Exosomes and Infectious Diseases

### **Chapter 3**

## Effectiveness of Exosomes in the Immune Cascade

*Gözde Atila Uslu and Hamit Uslu*

### **Abstract**

In order to treat and/or control a disease or prevent its occurrence, first of all, physiological pathways must be understood very well. In the previous 10 years, there has been a lot of interest in the function of exosomes in intercellular communication, particularly in studies on cancer and neurodegenerative disorders. This has led to plenty of research in this area. Exosomes are tiny transmembrane vesicles that are produced by endocytosis and are found in a variety of bodily fluids, including blood, saliva, cerebrospinal fluid, and breast milk. They are also released by a variety of tissues. Exosomes have a varied composition depending on where they come from, but they are often rich in cytosolic and cell surface proteins, lipids, DNA, and RNA. In recent years, the interactions between exosomes and the immune system have been frequently studied. However, despite all the researches, the physiological purposes of exosomes are still largely unclear.

**Keywords:** exosomes, immune system, T cells, NK cells, mast cells

### **1. Introduction**

Exosomes; although it was first defined as microparticles released from neoplastic cell lines, it was later determined that these structures were secreted by almost all cells in the body, and it was concluded that it would be more accurate to call them membrane-bound extracellular vesicles produced with endosomal division [1, 2]. It is stated that these microvesicles have an average diameter range of 40–160 nm and are formed by endocytic cellular pathways consisting of three different stages that have been identified so far. First stage; It is stated that is the invagination of the cell membrane from endocytic vesicles and leads to the formation of an early-shorting endosome (ESE), after which either novo formation occurs or can directly fuse with a pre-existing ESE, moreover golgi apparatus and the endoplasmic reticulum participate in this process. In the second stage, it is stated that ESEs can mature into lateshorting endosomes (LSEs) and multivesicular bodies are formed by accumulation of intraluminal vesicles in these bodies. In the third stage, it has been determined that multivesicular bodies can undergo proteosomal degradation, function as a temporary storage area (for major histocompatibility complex (MHC) class II), or combine with the plasma membrane to release exosomes (**Figure 1**) [3–7]. Exosomes can enter cells directly by different mechanisms or can be produced by cells by the process of endocytosis as mentioned above. It has been determined that exosome production, release,

### **Figure 1.** *Exosome biogenesis.*

and uptake may change with oxidative stress, radiation, inhibiting a proton pump, altering cellular pH decrease in membrane cholesterol and increase in intracellular calcium level [8–11]. Numerous proteins, including the tetraspanins CD63, CD81, and CD9, TSG101, Alix, and HSP70, have been discovered to be present in exosomes. In addition, cell type-specific proteins may vary due to their endosomal origin, but they also have conserved proteins identified in almost all exosomes (hsc70, tetraspanin, CD63) [3]. It has been reported that exosomes also have lipid bilayer, which is mostly composed of phosphatidylcholine (PC), ganglioside GM3, phosphatidyl ethanolamine (PE), sphingomyelin (SM), and cholesterol [12]. Exosomes contain a wide variety of RNAs; some of these have been shown to be mRNA, miRNA, rRNA, tRNA, lncRNA, piRNA, snRNA, and small nucleolar RNA [13].

Although the functions of exosomes are not entirely understood and are still the subject of debate, they are involved in remodeling the extracellular matrix, homeostasis and adaptation of plasma membranous glycoprotein models, signal transduction between cells, immunity, tissue homeostasis, and many aspects of human health and disease which including cancer and neurodegenerative diseases have stated that have important functions [14–17]. They may have a role in the spread of prions throughout the body and the exchange of membranes between cells in infectious neurodegenerative illnesses, also known as prion diseases [18]. In their study on the synaptic physiology of neurons, Chivet et al. [19] found that the lipids, proteins, and RNAs in the exosomes released by neurons in response to synaptic activity can directly alter signal transmission and protein expression in recipient cells and play a crucial role in information transfer between synapses. It has been emphasized that intercellular communication has a very important role in vascular remodeling, and although direct intercellular contact or paracrine effects are focused on in this process, recently, it may be effective in this process in extracellular vesicles. When the effectiveness of exosomes in the neovascularization process was investigated, it was shown that they can act with the Notch signaling pathway, which is one of the cell interaction mechanisms, and an increase in blood vessel frequency and bifurcation number [20]. In order to treat and/or control a disease or prevent its occurrence, the physiological pathways must first be understood very well. Exosomes can also have an impact on the immune system by directly contacting the cell's plasma membrane during this process

and then inducing intracellular signal cascades. The immune system plays a significant role in the emergence and development of disease pathophysiology as well as the emergence of acute and chronic complications.

### **2. Exosomes and T cells**

In the case of contact with foreign antigens, such as in the case of infection, several days are needed for the formation of the immune responses, which we call cell-mediated or cellular immunity, by the effector T cells. For this reason, this type of immunity is also called delayed-type immune response. Antigen presenting cells (APC) such as macrophages, dendritic cells, and B cells are needed in this process. These constructs process antigenic constructs and antigen processing and presentation is performed with MHC class I or MHC class II. The term human leukocyte antigen (HLA) can also be used instead of MHC proteins in humans. AHS binary signaling is triggered by the binding of the intracellular adhesion molecule (ICAM) on the ASH surface and the lymphocyte function-associated antigen 1 (LFA-1) on T cells. This process can be opened as follows: (1) Recognition of the antigen by the T cell receptor and its co-receptor (CD8 molecules on cytotoxic T cells and CD4 molecules on helper T cells are called co-receptors). (2) The binding of the B7 protein in ASH and the CD28 protein on the T cells leads to rapid proliferation, clonal expansion, and differentiation in T cells [21]. In addition, suppression mediated by regulatory T (Treg) cells had found to be effective in making the immune system tolerant to most autoantigens and preventing host damage [22]. As mentioned above, a large number of extracellular and intracellular signals are needed to initiate the rapid proliferation, differentiation, and migration of T cells to peripheral infection sites (**Figure 2**).

Exosomes, which have been determined to be secreted by almost all cells in the body, are also secreted from various hematopoietic cell types such as reticulocytes, B lymphocytes, platelets, T lymphocytes, and dendritic cells. It is known that exosomes secreted from dendritic cells contain proteins such as MHC class I and II and CD86 (provide necessary signals for T cell activation and survival) and these structures

**Figure 2.** *T cell activation.*

are effective in T cell stimulation. Exosome production may occur in peripheral tissues, after dendritic cells have traveled to lymph nodes, or in both cases, according to reports, but there is currently insufficient evidence to make a firm determination [23]. Exosomes that are loaded with specific peptides or antigens serve as vehicles for antigen presentation and can activate T cells (CD4+ and CD8+) also in the lack of dendridic cell. It has been established that exosomes have a positive impact on the immune system through various activities such as antigen presentation, stimulation, suppression, and tolerance of immunity [24]. It is also mentioned that some exosomes can express chemokine sequences like CCL2-5, CCL7, CCL20, CCL28, CXCL1-2, and CXCL16 because they can start other leukocytes like T cells from migrating to the infection sites [25, 26]. It is known that dendritic cell-T cell interactions cause an increase in calcium mobilization and Interleukin-2 and Interferon-gamma levels, resulting in T-cell activation. In addition, it is emphasized that co-stimulatory molecules such as CD86 strengthen intercellular interactions and T-cell functional activation in this process [27]. Zitvogel et al. [28] found that tumor peptide-pulsed dendritic cells-derived exosomes could eradicate or suppress the growth of tumors in a T-cell-dependent manner.

While it has been reported that synoviocyte-produced microparticles in inflammatory conditions like rheumatoid arthritis may exacerbate cartilage damage by increasing the synthesis of inflammatory mediators and cartilage-degrading enzymes [29, 30], other studies have suggested that T cell-stimulated TRAIL- and FasLcontaining microvesicules produced in the synovium may also be helpful in preventing autoimmune damage in rheumatoid diseases [31]. In fact, exosomes originating from immunosuppressive dendritic cells have been shown to be more efficient and safe than modified dendritic cells in the therapies of autoimmune disorders like rheumatoid arthritis [32]. However, there are studies showing that exosomes produced from cancer cells could disturb the functions of T and B cells, monocytes/ macrophages, NK cells and dendritic cells [33–35]. Exosomes synthesized from other cells could affect T cell functions, and the T-cells themselves too synthesize exosomes. It has been shown that these exosomes have a lipid bilayer and contain structures such as CD2, CD3/TCR, CD4, CD8, CD11c, CD25, CD69, LFA-1, CXCR4, FasL [36]. Tregs are subtypes of T cells, and it has been determined that the expression of CD73 by these cells shows a suppressive effect by converting extracellular adenosine 5-monophosphate to adenosine, in the same way that exosomes secreted from these cells also contain CD73 and exerting a suppressive effect with same pathway [37]. It is stated that exosomes derived from Tregs have a suppressive role in acute rejection and inhibit the proliferation of T cells, therefore exosomes released from Tregs may be a good alternative to prevent transplant rejection [38]. In another study, it is stated that the antigen-specific CD41 T-cell exosome (expressing CD4, TCR, LFA-1, CD25, and Fas ligand) may act as an immunosuppressant in the transplant rejection and treatment of autoimmune diseases [39]. Scientists have demonstrated that exosomes isolated from CD3+ T cells stimulated with IL-2 interact with and promote proliferation in resting autologous T cells [40]. It has been emphasized that high-level regulation of the miR-765/PLP2 axis of CD45RO-CD8+ T cell-derived exosomes can limit the cancer-supporting effects of estrogen on uterine corpus endometrial cancer [41].

### **3. Exosomes and natural killer (NK) cells**

While NK cells were at first idea to be large granular lymphocytes with built-in cytotoxicity against tumor cells, they have since been identified as a distinct class of

### *Effectiveness of Exosomes in the Immune Cascade DOI: http://dx.doi.org/10.5772/intechopen.110780*

lymphocytes with effector capabilities that enable them to produce cytokines in addition to their natural cytotoxicity [42]. Since it was not known at the time what strategies NK cells use to differentiate between normal and abnormal cells and thus participate in the defense mechanism, the missing self hypothesis was suggested. According to this theory, NK cells recognize and eliminate cells that do not express their MHC Class-1 (MHC) molecules [43]. However, it is now known that NK cells have a large number of activating and inhibitory receptors that can combine MHC class-1 molecules, MHC class-1-like molecules and non-MHC related molecules [44]. Although not previously known, it is now well established that NK cells, in addition to their cytotoxic effector functions, can secrete cytokines and serve to control the immune system as regulatory lymphocytes that can interact with both innate and adaptive immune cells such as monocytes and macrophages, dendritic cells and T lymphocytes [45, 46]. Detailed studies have shown that conventional NK cells (cNK) are distributed in circulation in the blood, spleen, and bone marrow [47–49]. However, it has also been shown that NK cells can infiltrate tissues. They also have resident NK cells, defined as resident NK cells (trNK), in the lungs, skin, kidneys, lymph nodes, liver, intestines, and virgin uterus [47, 49, 50]. In addition to the peritoneal region and placenta, NK cells are also present in peripheral circulation, where they account for 10–15% of all lymphocytes [51].

Defined as a subgroup of extracellular vesicles of endocytic origin [52–55], 30–150 nm sized exosomes [53–57] are secreted by various cell types and are involved in complex physiological and pathological processes [58]. Exosomes can move far within the body and have been found in a variety of bodily secretions, including blood, saliva, cerebrospinal fluid, breast milk, urine, gastric juice, and semen [55]. Exosomes are produced by a wide variety of cell types, but it is known that exosomes released by cancer cells are specifically taken up by different immune cells, including Treg, dendritic cells, and NK cells, and are therefore successful in controlling their functions [59, 60]. Exosomes excreted by cancer cells are thought to help tumor cells escape immune surveillance in their microenvironment by stimulating angiogenesis and metastasis, as well as inhibiting the function of immune cells (**Figure 3**) [61]. Despite all this information, how exosomes secreted from tumor cells affect the health of individuals with cancer has not been fully elucidated [60, 61]. Exosomes can carry many different molecules with the ability to stimulate the immune system depending on the cell of origin from which they are secreted.

In particular, exosomes secreted from dendritic cells have been shown to carry ligands that can activate NK cells and can also be loaded with antigen to activate invariant NKT (a subset of T cells with characteristics of NK cells and conventional T cells) cells and induce T and B cell responses that are specific to the antigen [62]. Several studies in the last decade have provided evidence supporting the important role of cancer-originate exosomes in regulating the cancer microenvironment [63, 64]. Exosomes released by human tumors like myeloid leukemia, cervical cancer, breast cancer, hepatoblastoma, T cell cancer, pancreatic cancer, and multiple myeloma that are dyed with PKH67 membrane have been shown to associate with, infiltrate, and be engulfed by NK cells [65–67]. Li et al. [60] showed that exosomes derived from genetically modified K562 cells secreting IL-15, IL-18, and 4-1BBL on their surface carry the proteins of these three molecules similar to the source cell, and that these exosomes can increase the activity of NK cells after 4 h of treatment and even strengthen their cytotoxicity on some tumor types. In contrast, they reported that prolonged treatment (48 h) may suppress the cytotoxicity of NK cells by inhibiting the expression of activated receptors on NK cells. In mouse B16 melanoma, MC38 colon adenocarcinoma, and KLN205 squamous cell carcinoma cell lines, both

**Figure 3.** *Some roles of cancer cell-derived exosomes.*

dendritic cells and exosomes secreted from dendritic cells can cause caspase activation and apoptosis, and exosomes released from dendritic cells can activate NK cells, according to research by Munich et al. [68]. In addition, TNF generated by exosomes of dendritic cells stimulates interferon gamma secretion by binding with NK cell TNF receptors. Jiang et al. [69] in NK92 and NK92-hIL-15 cell lines exposed to hypoxia for 48 h, they demonstrated that cytotoxicity was significantly increased and that hypoxia increased FasL, perforin, and granzyme B secretion. They revealed that exosomes produced from these NK cell lines under hypoxic conditions were effective in inhibiting both cell proliferation and migration while promoting apoptosis of breast cancer (MCF-7) and ovarian cancer (A2780) cells. However, this strategy, which encourages the overproduction of exosomes from NK cells as a consequence of NK cell hypoxia induction, might be a hopeful one for treating malignancy.

As a result, it is widely believed that exosomes produced by immune cells can strengthen immunity against cancer. In contrast, exosomes derived from cancer cells may decrease immunity and even alter the tumor microenvironment to promote selfenhancement and metastasis [70].

### **4. Exosomes and mast cells**

Paul Ehrlich discovered mast cells 145 years ago and named them "mastzellen," meaning "nourishing cells," because of their appearance [71]. CD34+ progenitor

### *Effectiveness of Exosomes in the Immune Cascade DOI: http://dx.doi.org/10.5772/intechopen.110780*

cells, which are mast cell precursors of hematopoietic stem cells (CD34−), are produced in the bone marrow during hematopoiesis and are introduced into the bloodstream [72]. These hematopoietic progenitor cells are thought to stay undifferentiated in the circulation but mature into mast cells in the presence of different growth factors secreted from the microenvironment of the tissues where they must settle. C-kit ligand and stem cell proteins are a few of these [73]. Mature mast cells are not detected in circulation under normal circumstances. However, under the control of stem cell factor (SCF) and a number of mediators, CD34+ progenitor cells move to regions where they finish differentiating into mast cells [73, 74]. Mast cells are distributed in the skin and mucosal tissues such as the stomach, intestines, and respiratory tract, which are the entry points of antigens, as well as in the peritoneum and chest cavities, smooth muscle tissue, connective tissue surrounding hair follicles, the central nervous system, and all tissues with blood vessels except the retina [73, 75–77]. Mast cells are mainly recognized for their role in allergy. They are also known to mediate vital symptoms such as skin blistering and flare reactions, bronchospasms in asthma, congestion and excessive mucus secretion in allergy-induced rhinitis and even systemic anaphylaxis [77, 78].

On the membrane of every mast cell, there is a high affinity IgE receptor called FcεRI. Due to its high affinity, IgE molecules can no longer detach after binding to the receptor and consequently mast cells are coated with IgE. This stimulation leads to the secretion of exosomes containing a large number of proinflammatory mediators (proteases, chemokines, amines, and cytokines) that are stored and newly synthesized in mast cells [79, 80]. Of course, this extra vesicular composition varies according to the stimulation received by mast cells, but they frequently cause the secretion of numerous cytokines, growth factors, and mitogens such as TNF-α, IL-1β, IL-2, IL-3, IL-4, IL-5, IL-6, IL-9, IL-10, IL-11, IL-11, IL-12, IL-13, IL-16, IL-33, EGF, FG2, GM-CSF, IF-γ, NGF, PDGF, SCF, FGF-β1, and VEGF (**Figure 4**) [80].

Mast cells contribute to the promotion of angiogenesis. Mast cells promote angiogenesis, or the bud-like growth of new blood vessels from old ones, by secreting angiogenic factors like bFGF, VEGF, TGF-β, IL-8, and TNF-α. Mast cells also exude proteases that exude pro-angiogenic factors that bind to heparin and promote their release. However, there is also a proof that mast cells promote angiogenesis in the development of cancerous cells [73, 81]. Exosomes released by human mast cells have been shown by Ekström et al. [82] to be capable of RNA cell-to-cell transmission. They also showed that these exosomes have enough mRNA to equal 15% of the content of the source cell. Xiao et al. [83] also reported that exosomes containing KIT (labeled with PKH67), a cytokine receptor expressed mainly on the surface of hematopoietic stem cells, were secreted from a human mast cell line (HMC-1) and that these exosomes could be taken up by the lung epithelial cell line A549, and could also cause increased proliferation in recipient cancer cells by activation of the PI3K signaling pathway. Exosomes from human adipose-derived mesenchymal stem cells have been shown to effectively suppress atopic dermatitis in mice with the condition by lowering blood eosinophil counts, serum IgE levels, and the expression of the cytokines IL-4, IL-23, IL-31, and TNF- at the mRNA level [84]. However, in a model of cerebral malaria in C57BL/6 mice infected with Plasmodium berghei ANKA strain, it has been shown that intravenous administration of exosomes derived from mast cells to infected animals increases the incidence of the disease, exacerbates both liver and brain damage, contributes to disruption of the brain vascular endothelial structure, and increases the corruption of the blood-brain barrier (**Figure 5**) [85].

**Figure 5.** *Various cells' released exosomes' effects on the activation of mast cells.*

*Effectiveness of Exosomes in the Immune Cascade DOI: http://dx.doi.org/10.5772/intechopen.110780*

### **5. Conclusion**

In the literature reviews, it was observed that the activity of exosomes on the immune system has not been fully elucidated. Exosomes formed by other cells under normal physiological conditions and affecting cells in the immune system and exosomes expressed by cells that are effective in the immune system may have different activities. In addition, it has been determined that exosomes secreted under normal physiological conditions and exosomes secreted under pathological conditions have different routes of action (one of the main reasons for this difference is surface proteins), therefore, exosomes can exhibit immunomodulatory effects by showing both immunosuppressive and immunostimulatory effects depending on the current conditions.

### **Funding**

There is no organization that financed this study.

### **Conflict of interest**

The authors declare that there are no conflicts of interest.

### **Author details**

Gözde Atila Uslu\* and Hamit Uslu Faculty of Medicine, Department of Physiology, Erzincan Binali Yıldırım University, Erzincan, Turkey

\*Address all correspondence to: gzd.gozde@hotmail.com

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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### **Chapter 4**

## Perspective Chapter: Exosome-Mediated Pathogen Transmission

*Kundave Rajendran Venkataswamy*

### **Abstract**

Exosomes are membrane-bound vesicles. They are considered as waste-management system of cells, crucial for intercellular communication of information and have emerged to be mediators of pathogen transmission. Pathogen derived exosomes advance infections by suppression of host immune response, transmission of pathogen-related molecules and immune evasion. The ability of exosomes derived from the virus infected cells to modulate the host immune response and/or further viral replication in the host has been reported in several viruses infecting human and animals. Apart from the virus infected cells, parasites have also known to release exosomes, parasite derived exosomes help in the attachment of parasite to the host and facilitate evasion of host immune responses. Tick-derived exosomes aid transmission of vectorborne pathogens. Similar to certain viral and parasitic infections, exosomes derived from bacteria infected cells could also play a key role in dissemination of the infection. An understanding of the exosome mediated pathogen transmission, its pathway and host-pathogen interactions could pave way to discovery of novel therapeutic targets.

**Keywords:** exosomes, intercellular communication, pathogen transmission, immune response, viral replication, attachment of parasite, bacteria, therapeutic targets

### **1. Introduction**

Exosomes are small extracellular vesicles ranging from 50 to 100 nm, that were first described in the late 1980s as "garbage bags" for cells to dispose the unwanted material and cellular waste from the cytosol. However, it has ever since become clear that they play a much broader role in intercellular communication by transferring bioactive molecules between cells [1]. Exosomes are composed of diverse bioactive molecules, such as proteins, lipids, and nucleic acids, such as DNA and RNA. These molecules can be taken up by other cells and influence cellular behavior, making exosomes a potentially important mode of intercellular communication. The two mechanisms of exosome biogenesis are the ESCRT-dependent and ESCRT-independent pathways [2]. The ESCRT-dependent pathway utilizes the endosomal sorting complexes required for transport (ESCRT) machinery which consists of several protein complexes (ESCRT-0, -I, -II, and -III) that recognize and cluster cargo molecules on the endosomal membrane and facilitate the

### **Figure 1.**

*Exosomes mediate further infection. Exosomes mediate further infection through transferring pathogen-related molecules (pathogenic genes and proteins) or even the entire pathogens. Therefore, exosomes can be either directly infectious, alter nuclear gene expression, or mediate toxic reactions.*

budding of intraluminal vesicles (ILVs) within the lumen of late endosomes or multivesicular bodies (MVBs). After the formation of MVBs containing (ILVs), the MVBs either fuse with lysosomes for degradation or fuse with the plasma membrane for exosome release. The ESCRT-independent pathway, on the other hand, does not require the ESCRT machinery for cargo sorting and ILV formation. Instead, it involves the direct budding of the plasma membrane to form exosomes. This process is thought to be mediated by lipid rafts and tetraspanin-enriched microdomains on the plasma membrane, which recruit specific cargo molecules and drive the formation of small membrane vesicles [3, 4]. The resulting vesicles are then released into the extracellular space as exosomes. Exosomes are known to play a crucial role in infections as carriers of pathogen-related molecules. Microorganisms such as bacteria, Protozoa, and fungi have been found to secrete various types of microvesicles, including exosomes, which are used by pathogens to spread infection and evade the host immune system. In addition to these microorganisms, viruses, have been shown to stimulate the production of exosomes in host cells, which in turn can regulate the host immune response [5]. Exosomes can directly transmit substances of pathogen origin and also indirectly influence the progression of infection by modulating processes such as immune evasion and apoptosis (**Figure 1**). Thus, the study of microvesicles and their role in host-pathogen interactions is an important area of research that could lead to the development of new therapeutics for infectious diseases.

### **2. Exosome-mediated parasite transmission**

Exosome research in parasite infections is particularly intriguing because it suggests that the communication between the host and the parasite via exosomes may play a key role in pathogenesis. Exosomal vesicles are an important component of microbial communication and can facilitate the exchange of genetic material, which can have significant implications for microbial evolution and adaptation [6].

### **2.1 Haemoprotozoan parasites**

Studies have shown that promastigote and amastigote forms of *Leishmania donovani* and *Leishmania major* can release exosomes, which are detected in host cells and selectively induce IL-8 secretion from macrophages [7, 8]. The chemokinetic recruitment of neutrophils helps *Leishmania* invade cells and gain access to macrophages upon phagocytosis of the infected neutrophils. This process is thought to occur through the release of chemoattractants by the infected macrophages, which then recruit neutrophils to the site of infection [9, 10]. This suggests that exosomes released by *Leishmania* species may play a role in modulating the host immune response and contributing to the pathogenesis of leishmaniasis. Research has demonstrated that *Leishmania* exosomes can induce the release of the immunosuppressive cytokine IL-10 while inhibiting the inflammatory cytokine tumor necrosis factor (TNF) in human monocyte-derived dendritic cells (DCs) in response to interferon gamma (IFNg). Dendritic cells are a type of immune cell that play a crucial role in initiating and regulating immune responses. The inhibition of TNF and induction of IL-10 by *Leishmania* exosomes can have important implications for the ability of the immune system to effectively respond to and clear *Leishmania* infections. TNF is a pro-inflammatory cytokine that helps to recruit immune cells to sites of infection and activate their antimicrobial functions, while IL-10 is an immunosuppressive cytokine that can dampen immune responses and promote the persistence of pathogens [9]. Several protozoan parasites, including *Leishmania* species and *T. cruzi*, have been shown to release exosomes and/or microvesicles [11–13]. *Leishmania* species are the parasites that cause human leishmaniasis, while *T. cruzi* causes Chagas disease. Similarly, studies have shown that *T. cruzi* can release exosomes that contain parasite-derived molecules, such as proteins and nucleic acids, which can modulate the host immune response and aid in parasite survival and proliferation. *T. cruzi-*derived exosomes have also been shown to induce pro-inflammatory cytokine production and apoptosis in host cells [14]. *T. cruzi*-derived exosomes have also been shown to contain immunomodulatory molecules, including miRNAs, which can regulate theexpression of host immune genes and contribute to the pathogenesis of Chagas disease. *T. cruzi* induces the release of exosomes from infected host cells, which expresses TGF-β, which has proven to facilitate parasite invasion and maturation in host cells [15]. The exosomes are known to protect extracellular life cycle stages of *T. cruzi*, such as epimastigotes from the vector and trypomastigotes from ruptured cells, from complement-mediated attack, facilitating parasite invasion of host cells [16]. The secretion of exosomes by *Leishmania* spp. and *T. cruzi* induce the release of exosomes from the cells that they infect [7]. Extracellular vesicles (EVs) have been shown to play a role in intercellular communication between parasites. Recent studies have shown that microvesicles play a crucial role in the transmission of malaria caused by the *Plasmodium falciparum* parasite (DEBS). These microvesicles are small membrane-bound particles that are released by infected red blood cells and can interact with uninfected cells in the vicinity. It has been found that these microvesicles contain specific molecules that can influence the behavior of the parasite. In particular, they can increase the commitment of asexual parasites to differentiate into sexual stages, known as gametocytes. This is important for the transmission of the parasite, as only the sexual stages can be transmitted to mosquitoes and therefore continue the life cycle of the parasite. By increasing the production of gametocytes, the microvesicles can effectively enhance the transmission potential of the parasite, making it more likely to be passed on to mosquitoes and therefore increase the spread of malaria [17, 18].

### *2.1.1 Plasmodium falciparum*

Malaria parasite *Plasmodium falciparum* has been found to use exosomes for communication between infected red blood cells. This communication between infected and uninfected red blood cells via exosomes is thought to play a key role in the pathogenesis of malaria [7]. Exosomal vesicles released from *P. falciparum* infected erythrocytes have been shown to help in parasite survival, transmission, density sensing and differentiation of gametocytes [19–21]. *Plasmodium falciparum*-infected RBCs (iRBCs) can communicate with each other via different mechanisms, including the exchange of genetic material through a process called cell-cell transfer or tunneling nanotubes (TNTs). This communication can result in the increased production of gametocytes, which are the parasite's sexual forms that can be transmitted to mosquito vectors and infect other hosts. In addition to TNTs, iRBCs can also release exosome-like vesicles that contain different types of cargo, including proteins, lipids, and nucleic acids. These vesicles can be taken up by other iRBCs or host cells, modulating their functions and promoting parasite survival in different environments, such as drug pressure or immune attack. One of the proteins that play a critical role in exosome-like vesicle production in *P. falciparum* is PfPTP2. This protein is a phosphatase that regulates different signaling pathways in the parasite, including those involved in vesicle biogenesis and secretion. Disrupting PfPTP2 function can reduce exosome-like vesicle production and affect parasite survival and virulence.

### **2.2 Protozoan parasites**

### *2.2.1 Trichomonas vaginalis*

*Trichomonas vaginalis*, a parasitic protozoan that is responsible for the common sexually transmitted infection trichomoniasis, has been shown to release functional exosomes that play a role in both parasite-to-parasite and parasite-to-host communication. One study published in 2013 showed that *T. vaginalis* exosomes contained virulence products that could specifically downregulate the secretion of the pro-inflammatory cytokine IL-8 by ectocervical cells [22]. This downregulation of IL-8 secretion could potentially limit neutrophil migration, which in turn could prevent pathogen clearance and facilitate the establishment of infection. Furthermore, *T. vaginalis* exosomes have been shown to contain a range of other bioactive molecules, including proteins, lipids, and nucleic acids, that are capable of modulating host cell behavior. They are known to induce cell death in host immune cells, impair host cell signaling pathways, and modulate host cell gene expression. The detection of exosomes secreted by *T. vaginalis* suggests a potential role for these extracellular vesicles in the pathogenesis of trichomoniasis. Furthermore, the detection of specific parasite proteins in T. vaginalis exosomes suggests that these vesicles may also play a role in the parasite's adherence to host epithelial cells, which is a critical step in the infection process.

### *2.2.2 Toxoplasma gondii*

Toxoplasmosis is known to be caused by *Toxoplasma gondii*. The human foreskin fibroblasts infected with *T. gondii* release a type of exosome-like vesicle that contains abundant miRNAs and shows a significant increase in mRNAs compared to uninfected fibroblasts. The mRNAs that are most enriched in these vesicles include thymosin beta 4, eukaryotic elongation factor-1α (EF-1α), Rab-13, and LLP homolog. These mRNAs have been previously associated with neurologic activitysuggesting that *T. gondii* exosomes may play a role in mediating neurologic effects in toxoplasmosis, a parasitic disease caused by *T. gondii* [23].

### **2.3 Helminths**

Various helminths, including trematodes like *Fasciola hepatica* and *Echinostoma caproni*, secrete exosomes and other extracellular vesicles (EVs) that can be internalized by host cells. Electron microscopy images have been used to study the morphology and distribution of EVs released by these helminths, including those that can be detected on the tegumental surface. The tegument is the outermost layer of the parasite, and it plays a critical role in the host-parasite interaction. By releasing EVs that can interact with the tegument, these helminths may be able to modulate the host immune response and evade host defenses [24]. Exosomes released by *Heligmosomoides polygyrus* (*H. polygyrus*), a parasitic helminth, can block the activation of type 2 innate lymphoid cells (ILC2s), which are immune cells that play a critical role in the host response to helminth infections. This blockade of ILC2 activation is thought to contribute to the ability of *H. polygyrus* to establish chronic infections in its host [25]. Furthermore, *H. polygyrus*derived exosomes have downstream effects on eosinophilic recruitment. Eosinophils are immune cells that play a role in the host response to helminth infections, and studies have shown that *H. polygyrus*-derived exosomes can induce the recruitment of eosinophils to sites of infection. This recruitment is thought to be mediated by the activation of IL-5, a cytokine that plays a role in the production and recruitment of eosinophils. Analyses of the secretion products of the tapeworm *E. granulosus* have revealed the presence of exosome-associated proteins, including CD63-like tetraspanins. CD63 is a transmembrane protein that is commonly used as a marker of exosomes, and tetraspanins are a family of proteins that are associated with the membrane of exosomes and play a role in their biogenesis and function. The presence of CD63-like tetraspanins in the secretion products of *E. granulosus* suggests that the parasite is capable of releasing exosomes, which could play a role in the pathogenesis of echinococcosis [26]. Exosomes released by parasites such as *Heligmosomoides polygyrus*, *Schistosoma mansoni*, and *Schistosoma japonicum* have been shown to contain immunomodulatory molecules, including proteins and miRNAs, which can modulate the host immune response and aid in parasite survival and proliferation. Exosome-like extracellular vesicles (EVs) was isolated from excretory-secretory (ES) products of fourth stage larvae (Tci-L4ES) of *Telodorsagia circumcincta*, a parasitic nematode that affects sheep. Proteomic characterization of these EVs and identified several proteins involved in various functions such as structure and metabolism of the parasite. Importantly, it was found that some of these proteins can be bound by two types of antibodies, IgA and IgG, in *T. circumcincta*infected sheep suggesting that these proteins may have potential as vaccine targets for the development and production of a vaccine against *T. circumcincta* infection [27]. Proteomic analysis could identify proteins carried by extracellular vesicles (EVs) released by tapeworms. Parasite-derived proteins such as antigen-5, severin/gelsolin/ villin lipid transport protein, alpha-mannosidase, and malate-dehydrogenase, as well as host-origin proteins such as carbonic anhydrase, fructose-bisphosphate aldolase, peroxiredoxin, hemoglobin alpha and beta, pyruvate kinase, serum albumin, and triose phosphate isomerase were identified in the EVs. The study also revealed that the EVs carried virulence factors, including highly immunogenic and tolerogenic antigens and peptidases, that were associated with cyst survival. This finding suggests that EVs may play a crucial role in tapeworm infection [28].

### *2.3.1 Filarial parasites*

Lymphatic filariasis is a parasitic disease caused by filarial worms, including *Brugia malayi*, *Wuchereria bancrofti*, and *Brugia timori*, which are transmitted through the bites of infected mosquitoes. Studies have suggested that extracellular vesicles (EVs), including exosomes, released by these worms may play a role in the pathogenesis of the disease [29]. Exosome-like vesicles secreted by the infective L3 stage of *B. malayi* are designated a set of proteins, including actin, EF-1α, EF-2, Rab-1, and HSP70, as exosome markers based on their presence in the vesicles. These proteins are known to be involved in various cellular processes, such as cytoskeletal organization, protein synthesis, and vesicle trafficking, suggesting that the EVs may play a role in modulating the host immune response and promoting parasite survival.

### **3. Exosome-mediated pathogen transmission by arthropods**

Arthropods, such as ticks and mosquitoes, have been shown to release extracellular vesicles (EVs) in their saliva during feeding. EVs are double-layer vesicles that are secreted by all cells and play a critical role in cell-to-cell communication. These vesicles contain various molecules, including proteins, lipids, and nucleic acids, that can be transferred to other cells to influence their behavior. In the context of pathogen transmission, infected cells can secrete EVs that carry infectious cargo, such as viral RNA, which can enhance pathogen transmission and replication. This has been demonstrated in the case of Zika virus, where infected mosquito saliva was found to contain EVs that carry viral RNA and can promote infection in recipient cells. Ticks are ectoparasites that feed on the blood of their hosts, and their saliva contains a complex mixture of proteins, lipids, and other molecules that help them to obtain a blood meal and evade the host immune response. It is likely that EVs are also present in tick saliva and play a role in modulating the host immune response. The argasid tick *Ornithodoros moubata* secretes immunomodulatory proteins in the saliva. Proteomic analysis of tick saliva has revealed several exosome-associated proteins, such as aldolase and enolase, as well as lipocalins that have anti-inflammatory properties. These lipocalins can scavenge leukotrienes, which are inflammatory mediators, and adenosine nucleotides, which can modulate the immune response. It is reported that exosomes are critical for the transmission life cycle of Langat virus (LGTV), a tick-borne virus closely related to tick-borne encephalitis virus (TBEV), which is a causative agent of a neurological tick-borne disease [30]. A study demonstrated that LGTV can infect tick cells and replicate within them. The virus is then secreted into the extracellular space via. Exosomes, which are taken up by neighboring cells, including both tick and mammalian cells. The exosomes containing LGTV were found to be infectious and could transfer the virus from infected to uninfected cells, indicating that exosomes play a crucial role in LGTV transmission. Furthermore, research shows that the exosomal cargo of LGTV-infected tick cells contained viral RNA and proteins, which could induce an antiviral response in uninfected cells, potentially limiting viral spread. It is also suggested that exosomes derived from neuronal cells are likely able to mediate transmission of tick-borne flavivirus RNA and proteins from one neuronal cell to the other in the CNS. These findings suggest that exosomes play a complex role in the transmission and pathogenesis of LGTV, and potentially other related tick-borne viruses such as TBEV. RNAi-mediated silencing of synaptobrevin expression in *A. americanum* adult ticks resulted in a significant decrease in feeding

### *Perspective Chapter: Exosome-Mediated Pathogen Transmission DOI: http://dx.doi.org/10.5772/intechopen.111514*

success. Specifically, the silenced ticks exhibited increased mortality, premature detachment from the host, and lower engorgement weights compared to control ticks. These findings suggest that synaptobrevin is critical for successful tick feeding and survival [31]. Arthropods such as mosquitoes are known to be important vectors for the transmission of flaviviruses, including DENV. Recent studies have shown that arthropod-derived EVs can contain viral RNA, including full-length viral genomes, and can transfer this RNA to neighboring cells or even to other hosts, potentially leading to the spread of infection. In addition to DENV, other flaviviruses such as Zika virus, Japanese encephalitis virus, and West Nile virus have also been shown to be transmitted by arthropod vectors and may potentially be contained within EVs. The mechanisms by which flaviviruses are packaged into arthropod-derived EVs and how they are transmitted to new hosts are not yet fully understood, and further research is needed to elucidate these processes. However, the discovery of viral RNA in arthropod EVs suggests that these structures may play an important role in the transmission and dissemination of flaviviruses.

### **4. Exosome mediated fungal transmission**

In addition to the parasites, other eukaryotes such as pathogenic fungi also release extracellular vesicles (EVs) that play important role in mediating the pathogenesis. Exosomes can play a role in the proliferation of fungal infections by several mechanisms. Firstly, fungal exosomes can carry virulence factors and antigens that can directly contribute to the pathogenesis of the infection. For example, fungal exosomes have been shown to contain proteins and lipids that promote the adhesion and invasion of host cells, as well as molecules that suppress the immune response and promote the survival of the pathogen within the host. Secondly, exosomes secreted by infected host cells can also indirectly promote the proliferation of fungal infections by modulating immune responses. For instance, exosomes released by infected immune cells can contain cytokines and other immune modulators that suppress the activity of immune cells, such as macrophages and neutrophils, which are crucial for controlling fungal infections. This, in turn, can facilitate the proliferation of the fungus within the host. Moreover, recent studies suggest that exosomes may play a role in the horizontal transfer of antifungal resistance among fungal populations. Fungal exosomes can carry genetic material, such as RNA and DNA, which can be transferred to other fungi, leading to the acquisition of antifungal resistance. Exosomes can proliferate fungal infections by carrying virulence factors, modulating immune responses. For example, the pathogenic fungus *Paracoccidioides brasiliensis* releases highly immunogenic EVs that contain the carbohydrate galactose-/-1,3-galactose (/-Gal), which is not found in human cells. These/-Gal-enriched EVs may generate a robust immune response in the host, but they may also be beneficial to the pathogen by binding to host lectins and potentially stimulating a suppressive type 2 response. Other opportunistic fungi, including *Cryptococcus neoformans*, *Candida albicans*, and *Histoplasma capsulatum*, also release EVs that contain virulence-associated factors such as polysaccharides and lipids [32]. For example, *C. neoformans* EVs are enriched in virulent capsular components such as glucosylceramide and glucuronoxylomannan (GXM), and a recent study has shown that phospholipid translocases (flippases) are important for *C. neoformans* exosome packaging and transport [33]. Interestingly, fungus-released EVs can also induce antimicrobial activity by host cells. *C. neoformans* EVs are taken up by macrophages and stimulate the production of TNF, IL-10, TGF-b,

and nitric oxide [34]. EVs released by *Malassezia sympodialis*, a component of human flora, can generate IL-4 and TNF secretion from peripheral blood mononuclear cells, enhancing an inflammatory response in cases of atopic dermatitis [35].

### **5. Exosome mediated bacteria transmission**

Extracellular vesicles (EVs) have been identified as a mechanism for dissemination of bacterial components. Gram-negative bacteria such as *Escherichia coli* and *Salmonella* have been shown to produce outer membrane vesicles (OMVs) that contain lipopolysaccharide (LPS), a potent endotoxin that can trigger an inflammatory response in host cells. OMVs have also been shown to carry other virulence factors, such as adhesins and toxins, and can promote bacterial survival and dissemination within the host. Similarly, Gram-positive bacteria such as *Staphylococcus aureus* and *Streptococcus pyogenes* have been shown to release membrane vesicles that carry lipoteichoic acid (LTA), another pathogen-associated molecular pattern (PAMP) that can activate host immune responses. In addition to OMVs and membrane vesicles, bacteria can also release exosomes, which are thought to originate from the bacterial cytoplasmic membrane and can carry a range of bacterial components, including nucleic acids, proteins, and lipids. Extracellular vesicles (EVs) are a newly described mechanism for bacterial dissemination and can contribute to the pathogenesis of bacterial infections.

### **5.1** *Mycobacterium* **spp.**

In the case of bacterial infections, much of our understanding of exosome production and function comes from studies on *Mycobacteria*. Additionally, there is increasing evidence that other bacterial species also produce exosomes that contribute to disease pathogenesis. Mycobacterial exosomes have been shown to carry bacterial components that modulate host immune responses and promote bacterial survival, as well as contributing to the dissemination of mycobacteria to other cells and tissues in the host. *Mycobacterium avium*-infected macrophages release vesicles that can stimulate a pro-inflammatory response in neighboring macrophages that are not infected [36]. *Mycobacterium tuberculosis* PAMPs can be transported from the phagosome to the MVB during macrophage infection, and these PAMPs are also found in extracellular vesicles released by infected macrophages [37]. These vesicles have been shown to have markers of a late endosomal/lysosomal compartment and are released through calciumdependent exocytosis, suggesting that they are exosomes [38]. The content of these exosomes can be detected inside neighboring uninfected cells, suggesting a potential role in intercellular communication during infection. The release of pro-inflammatory exosomes has also been observed in macrophages infected with *Mycobacterium tuberculosis* or *Mycobacterium bovis* BCG. These exosomes carry mycobacterial components that can stimulate an immune response and contribute to disease pathogenesis. The pro-inflammatory response is thought to be mediated by the activation of pattern recognition receptors (PRRs) on the surface of the macrophages, which recognize the mycobacterial components carried by the exosomes. This activation leads to the production of pro-inflammatory cytokines and chemokines that recruit and activate other immune cells to the site of infection. While mycobacterial exosomes have been shown to stimulate pro-inflammatory responses in macrophages, it is also possible that the mycobacterial components present on or in the exosomes could function to suppress the immune response. Mycobacterial exosomes can carry immunosuppressive

### *Perspective Chapter: Exosome-Mediated Pathogen Transmission DOI: http://dx.doi.org/10.5772/intechopen.111514*

components, such as mycobacterial lipids, that can downregulate the immune response and promote bacterial survival within host cells. In addition to carrying immunosuppressive components, mycobacterial exosomes may also promote bacterial persistence by facilitating intercellular communication and promoting the formation of bacterial aggregates within host cells. This can protect the bacteria from immune surveillance and promote their survival within the host. Exosomes have been shown to play a role in anthrax infection by serving as carriers of anthrax toxin components [39]. Tissue factor, is a blood coagulation protein that is also involved in a variety of cellular processes such as cell proliferation, migration, and apoptosis. It has been found on the surface of various cell types, including endothelial cells and macrophages.

### **5.2** *Helicobacter pylori*

miRNA expression in exosomes plays a role in the regulation of inflammation in macrophages and can affect the infectivity and pathogenicity of *Helicobacter pylori*. Specifically, miR-155 expression in exosomes derived from *H. pylori*-infected macrophages was found to increase significantly and could be delivered to surrounding macrophages to induce a stronger inflammatory response. Moreover, miR-155 loaded in exosomes derived from *H. pylori*-infected macrophages was found to promote the production of cytokines such as TNF-α, IL-6, and IL-23 to regulate inflammatory responses, thereby enhancing the expressions of cellular signal transduction proteins such as CD40, CD63, CD81, and MHC-I for immune-regulation responses. However, overactive macrophages can produce a multitude of proinflammatory cytokines and chemokines, leading to inflammation-related diseases or autoimmune diseases. During *H. pylori* infection, exosomes may act as vectors to carry virulence factors or proteins of *H. pylori* to host cells and target organs, thus playing a role in the pathogenicity of *H. pylori* [18].

### **5.3** *Bacteroides fragilis*

*Bacteroides fragilis*, a representative strain of *Bacteroides* spp., has been found to enhance immune function. This is achieved through the transfer of bacterial lipopolysaccharide to intestinal dendritic cells via exosomes. This process promotes the secretion of IL-10 and IL-6 by dendritic cells and the differentiation of T lymphocytes, which in turn intensifies the immune reactions of the host. Exosomes, which are closely associated with bacterial infection, are believed to act as signal transduction messengers [40].

### **5.4 Other bacteria**

It is shown that "microparticles" released from *Chlamydia pneumoniae*-infected cells contain tissue factor, and that these microparticles can activate NF-κB, a transcription factor involved in the regulation of TF expression in endothelial cells suggesting that *Chlamydia pneumoniae* may use exosomes or exosome-like vesicles as a mechanism for spreading the infection and modulating host cell responses [37]. Other bacterial species, such as *Pseudomonas aeruginosa*, *Burkholderia cenocepacia*, and *Staphylococcus aureus*, also produce exosomes that carry virulence factors and other bacterial components, which can modulate host immune responses and promote bacterial survival and dissemination. *Chlamydia trachomatis* is an intracellular bacterial pathogen that causes a variety of diseases in humans, including sexually transmitted infections and ocular infections. To establish and maintain infection, *C. trachomatis* has evolved several mechanisms to interact with host cells and manipulate host cellular processes.

One such mechanism is the release of host cell vesicles that contain bacterial effector proteins. These vesicles can be internalized by neighboring cells, allowing *C. trachomatis* to spread and establish new infection foci. Several cytotoxic and secreted proteins have been identified in these host vesicles, and they are believed to play a role in the delivery of virulence factors. One such protein is CT166, a cytotoxic protein that has been shown to induce cell death in host cells. Another is CT694, a secreted protein that has been shown to interact with host proteins involved in cell signaling pathways. These proteins, along with others found in host vesicles, likely play a critical role in *C. trachomatis* pathogenesis by facilitating the delivery of virulence factors and manipulating host cellular processes to the bacterium's advantage. Exosomes have been found to play a role in the pathogenicity of *Staphylococcus aureus*, specifically through the actions of the pore-forming α-toxin [41]. This toxin targets human non-virally transformed keratinocytes (HaCaT cells) and can be endocytosed by the cells to prevent cell lysis. The toxin-containing vesicles are then transported to late endosomes and incorporated into exosomes, which are secreted by the cells [42]. Interestingly, these exosomes contain both mono- and multi-meric toxins, which can be activated after being taken up by naive cells. This mechanism allows the bacteria to spread its virulence factors and evade the immune system, ultimately leading to the development of infections.

### **6. Exosome-mediated viral transmission**

Exosomes have been shown to play a role in a range of viral infections, including HIV, Hepatitis B and C, Influenza, and Zika virus, among others. Exosomes can contribute to viral pathogenesis by promoting viral replication and spread, inducing apoptosis in infected cells, and modulating the immune response to favor viral persistence. Additionally, exosomes can serve as vehicles for the transfer of viral components, including nucleic acids and proteins, between cells, facilitating viral spread and potentially contributing to the development of chronic infections. Viruses can hijack the host cell's exosomal pathway to promote the transfer of viral components, including nucleic acids such as viral RNA or DNA, between cells. Exosomes containing viral genomes can be taken up by susceptible cells, potentially leading to the establishment of a productive viral infection. When a cell is infected with a virus, it may secrete exosomes that contain viral components. These exosomes can then be taken up by other cells, potentially leading to the spread of the virus. Exosomes derived from viral-infected cells can contain a range of viral components, including viral proteins, nucleic acids (such as RNA or DNA), and even intact viruses themselves. These exosomes can therefore serve as a means of exporting viral components from the infected cell, potentially contributing to viral pathogenesis [43, 44]. The viral components contained within exosomes derived from viral-infected cells can contribute to the pathophysiological effects on recipient cells. These effects can be mediated by a variety of mechanisms, including the activation of cellular signaling pathways, the induction of inflammation, and the suppression of antiviral responses.

### **6.1 Human immunodeficiency virus (HIV)**

Exosomes derived from HIV-infected cells have been shown to contain viral proteins that can induce apoptosis (programmed cell death) in recipient cells. Similarly, exosomes derived from cells infected with the Respiratory Syncytial Virus (RSV) have been shown to contain viral proteins that can trigger an inflammatory response in

### *Perspective Chapter: Exosome-Mediated Pathogen Transmission DOI: http://dx.doi.org/10.5772/intechopen.111514*

recipient cells. HIV-1 is known to exploit exosomes to facilitate viral spread and evade host immune responses. The transfer of HIV-1 coreceptors CCR5 and CXCR4 within exosomes from infected to uninfected cells is one mechanism by which the virus can enhance its infectivity and spread to new cells. Exosomes from HIV-1-infected cells can transfer viral proteins and RNA to uninfected cells, leading to the activation of host immune responses and the promotion of viral replication and dissemination [45, 46]. In addition to promoting viral spread, exosomes can also serve as a mechanism for the virus to evade host immune surveillance. HIV-1 has been shown to use exosomes to downregulate host immune responses by transferring viral proteins such as Nef and Vpu to immune cells, leading to the degradation of host immune factors such as CD4 and MHC class I molecules [47].

### **6.2 Hepatitis A virus (HAV)**

Exosomes can acquire Hepatitis A Virus (HAV) components after HAV-infected plasmacytoid dendritic cells. These exosomes can protect HAV from neutralization by HAV antibodies and assist in the transmission of HAV among liver cells. Additionally, these HAV-carrying exosomes can also directly invade and infect uninfected cells with modest pathogenicity. In the case of HAV, infected plasmacytoid dendritic cells can release exosomes containing HAV components, which can then be taken up by uninfected liver cells. These exosomes can protect HAV from neutralization by HAV antibodies, allowing the virus to more easily infect liver cells and spread throughout the liver [48].

### **6.3 Hepatitis C virus (HCV)**

In the case of HCV, studies have shown that the virus can incorporate into exosomes either as whole virions or as nucleocapsids, envelope proteins, and replicationcompetent viral RNA. The mechanism by which HCV incorporates into exosomes and how this process is regulated is not yet fully understood. However, it is believed that the incorporation of HCV into exosomes may help the virus to evade the immune system and spread throughout the body and play a role in the pathogenesis of HCV infection [49]. Hepatitis C virus (HCV) is a small enveloped virus with a positivesense single-stranded RNA genome, belonging to the Flaviviridae family. Recent research has shown that the assembly and release of HCV virions in hepatocytes are closely correlated with the exosome secretory pathway. This pathway can incorporate either the whole virions or only nucleocapsids, envelope proteins, and replicationcompetent viral RNA into exosomes. In addition to classical transmission by free viral particles, HCV can also be transferred by exosomes to naive human hepatoma Huh7.5.1 cells, resulting in productive infection with efficiency like that of free infectious particles. Exosomes derived from HCV-infected Huh7.5 cells or individuals both contain miR-122, which promotes HCV replication and transfer. Exosomes can transmit HCV to naive cells and modestly protect antibodies from being neutralized by HCV. This suggests that HCV may use transmission via exosomes as an immune evasion mechanism, allowing it to resist neutralization by anti-HCV antibodies.

### **6.4 Epstein-Barr virus (EBV)**

Epstein-Barr virus (EBV), exosomes are known to play a role in the maintenance of latent infection. EBV is a virus that can cause infectious mononucleosis and is

associated with several types of cancer. When EBV infects a cell, it can enter a latent phase in which it remains in the host cell without causing any symptoms. During this phase, the virus can be reactivated and start replicating, leading to the production of new viral particles and the spread of infection. EBV can exploit exosomes to deliver its genetic material, including proteins, RNA, and miRNA, to target cells. This allows the virus to maintain its latent infection in the host by regulating the expression of viral and host genes [50]. Apart from Burkitt lymphoma and nasopharyngeal carcinoma, EBV has also been linked to other malignancies, including Hodgkin's lymphoma, gastric cancer, and certain types of lymphomas and leukemias. Exosomes released by EBV-infected cells can play a role in the pathogenesis of these diseases by transferring viral proteins, RNA, and miRNA to surrounding cells and tissues. This can lead to the activation of signaling pathways that promote tumor growth and metastasis, as well as the suppression of host immune responses against the virus and cancer cells. Therefore, understanding the role of exosomes in EBV-associated malignancies may provide new insights into the mechanisms of tumor progression and immune evasion, as well as potential targets for therapeutic intervention [51].

### **6.5 Herpes simplex virus (HSV)**

Exosomes derived from Herpes Simplex Virus (HSV) infected cells have been shown to contain viral proteins, RNA, and miRNAs that can be transmitted to uninfected cells and modulate their gene expression to promote viral replication and transmission [52]. The presence of these viral components in exosomes suggests that they may play a role in HPV-mediated immune evasion and tumor progression. Furthermore, the ability of exosomes to transfer their contents to neighboring cells may contribute to the spread of HPV infection. Dias et al. [53]. found that the prion protein (PRNP) plays a role in directing multivesicular bodies (MVBs) containing intraluminal vesicles (ILVs) toward the plasma membrane for the release of exosomes. Specifically, PRNP was shown to interact with components of the endosomal sorting complex required for transport (ESCRT) machinery, which is involved in the formation of ILVs within MVBs. This interaction was found to promote the association of MVBs with the plasma membrane and the subsequent release of exosomes. These findings suggest that PRNP may play a key role in regulating the secretion of exosomes in various physiological and pathological contexts.

### **6.6 Porcine reproductive and respiratory syndrome virus (PRRSV)**

Exosomes derived from Porcine Reproductive and Respiratory Syndrome Virus (PRRSV)-infected cells can contain viral RNAs and transfer productive infections to naive cells, even in the presence of PRRSV-specific neutralizing antibodies (NAbs). PRRSV is a highly contagious virus that causes significant economic losses to the swine industry worldwide. The virus is known to replicate in the respiratory tract and can cause respiratory distress in infected pigs, as well as reproductive failure in pregnant sows. Recent studies have shown that exosomes derived from PRRSVinfected cells can contain viral RNAs, proteins, and even infectious virions. These exosomes can then be taken up by naive cells, which can lead to the establishment of a productive infection. It has been shown that PRRSV-specific NAbs are not effective in neutralizing the virus when it is packaged within exosomes. This suggests that exosomes may provide a mechanism for PRRSV to evade the host immune response and spread the infection to other cells [54].

### **6.7 West Nile virus (WNV)**

It has been demonstrated that exosomes containing mosquito-borne West Nile Virus (WNV) can facilitate the transmission of viral RNA and proteins from one neuronal cell to others, suggesting a potential role for exosomes in WNV neuropathogenesis. West Nile Virus is a neurotropic virus that can cause severe neurological disease in humans and animals. The virus is thought to replicate in neurons and can spread from cell to cell within the nervous system. Recent studies have shown that exosomes derived from WNV-infected cells can contain viral RNA and proteins, which can be transferred to neighboring neuronal cells. This suggests that exosomes may play a role in the spread of WNV within the nervous system [44]. Furthermore, it has been suggested that exosomes may also be involved in the development of WNV neuropathogenesis, as the transfer of viral RNA and proteins to neighboring cells may alter the function of the recipient cells and contribute to disease progression.

### **7. Conclusion**

In conclusion, exosomes play a significant role in mediating pathogen transmission between cells. Through their ability to transfer various types of bioactive molecules, including nucleic acids, proteins, and lipids, exosomes can facilitate the transfer of infectious agents, including bacteria, viruses, and parasites. Exosomes have been shown to act as vectors for the spread of several human pathogens, including HIV, HCV, and prion proteins. In addition, exosomes released from infected cells can promote the spread of infection by suppressing the host immune response and facilitating pathogen replication. However, the mechanisms by which exosomes mediate pathogen transmission are still not fully understood, and further research is needed to better characterize the specific roles of exosomes in the pathogenesis of different infectious diseases. Additionally, the potential use of exosomes as diagnostic markers or therapeutic targets for infectious diseases warrants further investigation. Despite the remaining uncertainties, the emerging evidence suggests that exosomemediated pathogen transmission is a crucial aspect of infectious disease biology and has significant implications for the development of new diagnostic and therapeutic approaches.

### **Author details**

Kundave Rajendran Venkataswamy Tanuvas Veterinary College and Research Institute, Orathanadu, Tamil Nadu, India

\*Address all correspondence to: kun.vet@gmail.com

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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### **Chapter 5**

## Role of Exosomes in Tuberculosis: Looking towards a Future Road Map

*Sushanta Kumar Barik and Jyotirmayee Turuk*

### **Abstract**

Exosomes are generated by the multivesicular degradation of plasma membrane fusion, lysosomal, and extracellular release of intracellular vesicles. The exosome ranges from 30 to 150 nm in size. Exosomes are "bioactive vesicles" that promote intercellular communication. Exosomes contain a variety of biologically active substances packaged with proteins, lipids, and nucleic acids. After any microbe infection into the exosomes, the content of the exosomes changes and is released into the bloodstream. Such type of exosome content could be useful for basic research on exosome biology. Tuberculosis (TB) is a serious infectious disease caused by *Mycobacterium tuberculosis* (*Mtb*). During the *Mtb* infection, the exosomes played an important role in the body's infection and immune response by releasing several exosome components providing new ideas for diagnosis, prevention, and therapeutic treatment of *Mtb* infection. The detection of the low abundance of the *Mtb* numbers or secreted peptides in the serum of TB patients is not possible. The best way of findings for diagnosis and treatment of TB could be possible by the exploration of exosome content analysis through various useful technologies. The study and analysis of exosome content would produce a road map for the future early diagnosis, prognosis estimation, efficacy monitoring, research, and application for TB.

**Keywords:** exosome, TB, *Mtb*, content, roadmap, serum

### **1. Introduction**

Tuberculosis (TB) is an infectious disease caused by *Mycobacterium tuberculosis* (*Mtb*). *Mtb* is an intracellular bacteria engulfed by the macrophages through the process of phagocytosis. After invades into the host body, some of them eliminates and survives by immune escape mechanism as well but cause TB or latent tuberculosis infection (LTI). The exosomes size ranges 30–100 nm and is secreted by all living cells. Exosomes are circulating in the human body fluids rich in proteins, nucleic acids, lipids, etc. The components of the exosomes released by the body after *Mtb* infection play an important role in body's immune response and infection by providing new ideas on the diagnosis, treatment, and prevention of TB infection [1]. The vesicles were isolated through centrifugation at 10,000 *g* for

90 minutes from in vitro culture of sheep reticulocytes during the maturation of reticulocytes. These vesicles were called "exosomes" coined by Johnstone in the year 1987 [2]. Those vesicular exosomes were released during the maturation of the sheep reticulocyte and contained a few numbers of plasma membrane functions. These vesicles contained the transferrin receptor and also contain other plasma membrane activities such as nucleoside transporter and acetylcholinesterase. The formation of exosomes is a natural phenomenon with the release of the transferrin receptor [3]. Exosomes were observed in both nucleated and non-nucleated reticulocytes. The protein content of exosomes is equal to the protein content of plasma membrane. The protein content of the exosomes may vary on the origin of the species. Exosomes contain a non-transmembrane protein HSP70, a major cellular chaperone protein. The externalized proteins are the intact proteins retaining the catalytic activity and native ligand binding activity. The small exosome structures relatively contain many proteins play an important role in controlling serious human pathological problems by various pathogens. Revisiting the functions of exosomes in human pathological problems since the discovery could possibly to making a roadmap [4].

Exosomes were involved in intercellular information transmission and potential medical applications. The special insight on the biological significance of the exosome is very essential for various applications in the human biological field [4]. The characterization of exosomes is very essential during immune response for a better announcement of host-pathogen interactions. Based on exosome characterization, development of various approaches would be possible to fight infections through various pathogens. When macrophages infected with the *Mtb* release from cells small vesicles known as exosomes that contain pathogen-associated molecular patterns (PAMPs). When exosomes were exposed to the uninfected macrophages, they were stimulated with a proinflammatory response in a toll-like receptor and myeloid differentiation factor 88-dependent manner. The cell culture media along with fetal calf serum (FCS) at a centrifugal speed of 100,000 *g* for 15 h had been used to isolate contaminating exosomes [5]. The exosomes are controlling *Mtb* infection through exosome biogenesis. During *Mtb* infection, exosomes played an important role in recruiting and regulating host cells. *Mtb*-infected RAW264.7 cells secreted chemokines from C57BL/6 mouse-derived bone marrow macrophages treated with exosomes and also induced the migration of CFSE-labeled macrophages and splenocytes. Exosomes were purified using Exo Quick purification system (System Biosciences, CA) on an average of 20 μg purified exosomes from 10 million cells [6].

*Mtb* peptides were detected in serum extracellular vesicles with latent tuberculosis-infected (LTBI) individuals. The identification of biomarkers from a serum source of latent *Mtb*-infected patients could be a better target for preventive therapy. Multiple reaction monitoring mass spectrometry (MRM-MS) assays detected 40 *Mtb* peptides from 19 LTBI patients. Mtb peptide detection in serum extracellular vesicles is a useful technique in diagnosis of LTBI [7]. Exosomes containing highly antigenic proteins could be an alternative approach for the development of a TB vaccine [8]. Extracellular vesicles (EVs) delivered Mycobacterium RNA into the host to promote host immunity by killing the bacteria. This technology is a novel approach to treat drug-resistant TB [9]. Exosomes were used as a tool for rapid diagnosis of TB. The detection of *Mtb* lipoarabinomannan and CFP-10 from the urinary EVs of pulmonary tuberculosis (PTB) and extrapulmonary tuberculosis (EPTB) patients would be helpful in the rapid diagnosis of TB [10].

*Mtb*-infected exosome contains a lot of proteins, nucleic acids for the rapid or slow manner detection and diagnosis of TB whether PTB or LTBI or drug-resistant (DR-TB). The collection of various *Mtb*-infected exosome materials from various research papers could give a better road map on the diagnosis of TB in a better way and plan out the future for rapid diagnosis on the development, detection, and cure of TB in the world.

### **2. Exosomes response to the** *Mtb*

The host interactions with the pathogens are always a challenge in chronic diseases and to understand the mechanism, complexities, and sequential events. TB is a major worldwide disease and the understanding of TB immunology become a major refined since the identification of *Mtb.* Understanding the mechanism of how the immune cells are recognizing *Mtb* can be an important issue for development of therapeutic strategies and vaccine development. Several classes of pattern recognition receptors (PRRS) including toll-like receptors (TLRs), C-type lectin receptors (CLRs), and nod-like receptors (NLRs) were involved in the recognition of *Mtb.* TLRs family such as TLR1, TLR2, TLR4, TLR9, IL-1β, and IL-18 played an important role in the pathogenesis of TB [11].

Exosomes are the potential mediator of T cell activation. The released exosomes from mouse *Mtb* infection contribute significantly to T cell response. Rab27a played an important role in exosome biogenesis. The Rab27a deficiency mice showed diminishing of the protein components to exosomes and *Mtb* strains. Exosomes function to promote T cell immunity during *Mtb* infection and an important source of extracellular antigen [12]. Exfoliated vesicles with 5′-nucleotidase activity was reflected from the culture of various normal and neoplastic cell lines. Exfoliated membrane vesicles were served in physiologic function and referred to as exosomes. It was observed by electron microscopy that the shredded vesicles were a constituted part of plasma membrane [13].

EVs were packed with proteins, nucleic acids, and lipids released from the mammalian and bacterial cells. EVs played an important role through the intercellular transduction acts like a messenger. The *Mtb*-infected EVs released cells played an important regulatory role in the anti-*Mtb* immune response. EVs regulate innate and acquired immune responses of the body against *Mtb* and for this key immune response, EVs were considered an important factor in the development of *Mtb* vaccine [14]. The microbial and host interaction components were spread through exosomes either activate or suppress the immune system of the host. Exosomes were involved in multiple infection processes including formation or modification of the infection, T or B cells activation, and interaction with nonimmune cells such as fibroblasts and endothelial cells (**Figures 1**–**3**). When the bacteria exposure to the exosome, the release of cellular components begins with the activation/submersion of the immune response of the host [15].

Proteins secreted from the Mycobacterium species were identified those were contributed to the protective immunity. Mycobacterial surface proteins were analyzed from infected macrophages. The fibronectin and 85 kDa protein complexes were identified among the mycobacterial proteins released by the infected macrophages [16].

The exosomes promoted the macrophages for the release of chemotactic factors by activating immune cells in vivo and in vitro [6]. The microvesicles and exosomes

### **Figure 1.**

*(A) Electron photomicrograph of vesicular particles sedimented from superfusate of C-6 rat glioma monolayer cultures. Particles in conditioned medium. (magnification X 33 600). Note smaller vesicles contained within the larger vesicles (arrow). (B) Small vesicle population at greater magnification (glutaraldehyde fixed, magnification X 78 400) [13].*

### **Figure 2.**

*Exosomes from bacteria-infected macrophages release exosomes containing antigens that induce cross-priming to activate antigen-specific CD4+ and CD8+ T cells. Some exosomes released from infected cells inhibit cytokine production by T cells. Exosomes from infected cells also contain PAMPs that stimulate macrophage production of proinflammatory mediators like TNF-α or limit the macrophage response to IFN-Y. Dashed line indicates unknown mechanism [15].*

from the *Mtb* macrophages could activate T cells in response to antigen presentation. Adenosine triphosphate (ATP) induced exosomes were generated very rapidly and yielded much higher allowing significant time and cost advantages. *Mtb* interacted with ATP to induce the release of exosomes. These induced exosomes contained the major histocompatibility complex class-II (MHC-II) molecules for antigen presentation. ATP-induced exosomes could be used for a therapeutic purpose as an alternative to conventional exosomes [17].

*Role of Exosomes in Tuberculosis: Looking towards a Future Road Map DOI: http://dx.doi.org/10.5772/intechopen.111544*

### **Figure 3.**

*The release of mycobacterial proteins from the phagosome in infected macrophages. Release of labeled mycobacterial proteins from the phagosome in infected macrophages. Live BMMf infected for 24 h with fluorescein succinimidyl ester-labeled BCG were analyzed by fluorescence microscopy. Labeled bacterial proteins were released from the mycobacterial phagosome into subcellular compartments of the infected macrophage (small arrowheads). The labeled bacteria are intensely fluorescent and are indicated by the large arrows [16].*

### **3. Exosome contents and proteomic profiles of exosome proteins with TB**

Exosomes are nanovesicles secreted by most but not all cells and specifically mediate intercellular communication through the transfer of genetic information of coding and noncoding RNA to recipient cells. The exosomes played an important biological role in the regulation of normal physiological and pathological processes through altered gene regulatory networks. Exosomes were targeted for the delivery of human genetic therapies through exogenous genetic cargoes such as siRNA [18]. *Mtb* is always in a dormant state for many years in the host system which is the cause of latent tuberculosis (LTB). Exosome contains a lot of *Mtb* antigens may be used as an alternative approach to develop the TB vaccine. A study was reported through the LC–MS/MS technique identified 41 *Mtb* proteins such as antigen 85-C, PckA, GabD1, β-1,3-Glucanase precursor, DnaK, LpdC, LprA, EST-6, etc. These were presented in exosomes released from *Mtb-*infected J774 cells and 29 *Mtb* proteins such as antigen 85-C, PckA, Fba, PepN, SahH, GroES, etc. Many of the released exosome proteins were highly immunogenic [8]. Flow cytometry analysis is a suitable method to characterize the surface markers of the extracellular vesicle's subpopulations in cells. The surface marker proteins were detected those were unique to exosomes naïve and *Mtb* infected THP-1 macrophages. The most similar findings of the surface protein markers such as CD63, CD9, CD81, and CD29 were detected in the exosomes of THP-1 cell culture supernatants by flow cytometry method. The purpose of characterization of the exosome surface proteins from the cell culture supernatants. Thus, the establishment of more sensitive methods enables the researcher to characterize the *Mtb* proteins in exosomes [19]. The main function of exosomes is interaction between cells through contact and exchange of soluble materials.

In TB patients, the exosomes were released from the *Mtb*-infected cells. The plasma of active TB patients generally contains the lipids and proteins derived from the exosome. Exosomes of all TB patients contains a lot of proteins such as sphingomyelins (SM), phosphatidylcholines, phosphatidylcholine inositol, free fatty acids, triglycerols, cholesteryl esters, etc. *Mtb* infections to the host proteins changed the

host protein composition of a total of 37 proteins. Proteomic study indicates the expression of low levels of proteins such as apolipoproteins, antibacterial proteins cathelicidin, scavenger receptor cystine rich family member, ficolin3, etc. were observed in TB patients but the adhesion proteins (integrins, intercellular adhesion molecule2 (ICAM2), CD151, proteoglycan4 were highly prevalent in PTB patients. Analysis of these exosome proteins in TB patients is a new achievement in the hostpathogen interaction and helps the development of new vaccines and therapies in TB research [20].

Exosomes were loaded with the microbial proteins after *Mtb* infection. After *Mtb* infection into the exosome, there must be changes in the composition of exosomal proteins and the study of the exosomal proteins could contribute to the understanding of the progression of TB after *Mtb* infection and open the way to understand the development of a specific biomarker for diagnosis of the TB. An experimental analysis of the *Mtb*-infected cells by the tandem mass spectrometry analysis specifically showed that the 41 proteins were significantly more abundant in exosomes. Some of the proteins were identified through the novel biotinylation strategy to confirm the protein localization in the exosomal membrane. The *Mtb* influenced the changes in the protein composition of exosomes released from the *Mtb-*infected cells [21]. These proteins are given in **Tables 1**–**3**.

A study investigated the regulation of protein N-glycosylation in human macrophages and their secreted microparticles (MPs) after *Mtb* infection. Upon *Mtb* infection, the protein N-glycosylation of macrophages rapidly and significantly occurred following *Mtb* infection [22]. Always searching for a rapid and sensitive biomarker is useful for the diagnosis of TB. Exosome markers were stable within the double membrane of the exosome. Heat shock protein HSP16.3 was an important capsule protein produced by *Mtb*. The HSP16.3 protein was secreted in excess amount in exosomes from the U937 cells infected with *Mtb* and an amount of HSP16.3 proteins was detected in blood exosomes of ATB patients. Thus, the HSP16.3 protein act as an exosome-based TB biomarker for *Mtb* diagnosis [23]. Blood-secreted exosome-based "biosignature" through the multiple reactions monitoring mass spectrometry assay (MRM-MS) could be used as a diagnostic biomarker for active TB [24]. The details of the peptides are given in **Tables 4** and **5**.

Exosome RNA sequencing analysis were derived from the clinical samples of ATB, LTB revealed the gene expression profiles. The selective packaging of RNA cargoes into exosomes in different stages of *Mtb* infection would facilitate the potential targets for prevention, treatment, and diagnosis of TB. The gene enrichment analysis of the *Mtb* RNA in exosomes identified a lot of functions in active and LTB patients [25]. The details of total function of *Mtb* exosome are given in **Figure 4**.

These gene-enrichment analysis of the *Mtb*-infected exosome gives an idea of the future roadmap of the TB diagnosis in active population level. Generally, TB diagnosis was performed through microscopy, PCR amplification, or culture of *Mtb* DNA from sputum or the biopsy of infected tissue from human beings. The current improvement of detection methods for diagnosis of TB in serum samples could possible by advanced methods. Sometimes the detection of Mycobacterial products in serum is not possible due to the low abundance number of *Mtb.* The exploration of the exosome enrichment advance assay would require to improve the sensitivity of the assay.


*Role of Exosomes in Tuberculosis: Looking towards a Future Road Map DOI: http://dx.doi.org/10.5772/intechopen.111544*


### **Table 1.**

*Proteins significantly different between exosomes from Mtb-infected and control macrophages.*


### **Table 2.**

*Membrane-associated proteins significantly more abundant in exosomes from Mtb infected cells and their biotinylation pattern.*

*Role of Exosomes in Tuberculosis: Looking towards a Future Road Map DOI: http://dx.doi.org/10.5772/intechopen.111544*


### **Table 3.**

*List of proteins and specific peptides labeled with LC-LC biotin.*

An enhanced MRM-MS is a method to detect ultra-low abundance of ultra-*Mtb* peptides in human serum exosomes. This MRM-MS technology could be useful for the detection and diagnosis of low-abundance *Mtb* peptides in the circulating serum exosome for the search of biomarkers [26]. As TB is a chronic infectious disease, attention to be paid to the non-coding RNA of exosome content of *Mtb* patients. Research on progress reported by Shu-hui et al. [27] on exosome noncoding RNA of *Mtb* patients could be useful as a potential biomarker on TB. A comprehensive proteomic analysis of the serum exosome proteins was analyzed in active TB (ATB) patients. A total of 123 differential proteins were identified in the serum exosome of ATB patient's. The characterization and identification of proteins in exosome of serum-active patients could consider a potential biomarker for TB [28]. The details of upregulated and downregulated proteins are given in **Tables 6** and **7**.

The study and analysis of exosome contents are suitable for the development of a suitable biomarker for the diagnosis and treatment of TB. The exosome protein components were identified.


### **Table 4.**

*Peptides that distinguish (a) pulmonary tuberculosis (PTB) or (b) extra-PTB patients from non-Tb patients.*


### **Table 5.**

*Peptides specifically detected in active Tb patients.*

**Figure 4.** *Total function of Mtb exosome.*

### **4. Exosome miRNA as a biomarker source for diagnosis and treatment of TB**

Serum exosomes expressed CD81, the exosome marker protein. When these exosomes were infected with the *Mtb,* contains the increased level of miRNA such as miR484, miR 425, and miR96 in TB patients compared with the healthy control. As these markers were associated with active PTB, the expression of these miR could possibly increase the diagnostic power for diagnosis of TB patients as a biomarker [29]. Selection of biomarkers for diagnosis and treatment of TB is the most important issue. Analysis of blood samples from TB patients showed that the upregulation of miR-106b-5p was increased in exosomes. miR106b-5p promoted lipid droplet accumulation through the regulation of Creb5-SOAT1-CIDEC and suppressed macrophage apoptosis via Creb5-CASP9-CASP3 pathway leads to survival of *Mtb* in the host. The miR-106b-5p could be used as a biomarker for diagnosis of TB patients [30].

### *Role of Exosomes in Tuberculosis: Looking towards a Future Road Map DOI: http://dx.doi.org/10.5772/intechopen.111544*

Now a days, TB is a threat to human health problem has an accuracy to the current TB diagnosis. Circulating exosome could be used as a diagnostic biomarker in TB. The study was examined the expression of the biomarkers for the diagnosis of TB infection. The miR-484, miR425, and miR96 were significantly increased in TB patients as compared with the healthy control and was examined the expression of miRNA as biomarker candidates for diagnosis of TB infection [31]. miRNA and electronic health records (EHRs) could be used to develop diagnostic models for


### **Table 6.**

*Upregulated proteins with significant interesting in exosomes from ATB patients.*



### **Table 7.**

*Down-expressed proteins with significant interesting in exosomes from ATB patients.*

PTB and tuberculosis meningitis (TBM) in a selective cohort study with the support vector machine (SVM) algorithm. Exosomal miRNAs (miR 20b, miR191 and miR486) along with EHR data through a machine learning algorithm could suggest for the diagnosis of the PTB and TBM [32]. The development of potential molecular targets for the detection and diagnosis of latent and active TB is possible by the miRNAs and repetitive region-derived small RNAs in exosomes. The most possible specifically expressed miRNA in LTBI patients were (hsa-let-7e-5p, hsa-let-7d-5p, hsa-miR-450a-5p, and hsa-miR-140-5p) and in TB patients were (hsa-miR-1246, hsa-miR-2110, hsa-miR-370-3P, hsa-miR-28-3P, and hsa-miR-193b-5p). Over all findings on miRNA, indicates the presence of biomarkers on the detection and diagnosis of the LTBI and TB patients [33].

*Role of Exosomes in Tuberculosis: Looking towards a Future Road Map DOI: http://dx.doi.org/10.5772/intechopen.111544*

The emerging role of functional and diagnostic potential of the several exosomal miRNA was studied by the several investigators and could explore as a possible diagnostic and therapeutic biomarker in *Mtb* infection [34]. TB biomarkers are generally predicting the treatment efficacy, cure of active tuberculosis, induction of protein immune responses by vaccination and reactivation of LTI. The suitable efforts are needed for development of suitable biomarker to meet the future challenges to cure the TB.

### **5. Exosomal DNA as a novel diagnostic biomarker for TB**

Exosome is suitable for the detection of pathogen-derived nucleic acids. A novel approach was adopted for diagnosis of TB using exosomal DNA (exoDNA) through the droplet digital PCR (ddPCR). The ddPCR platform was used for detection of *Mtb* DNA in suspected PTB cases. The exosomal DNA was the primary method for the detection of the *Mtb* DNA in the ddPCR. The ddPCR is more sensitive than the real-time PCR. Therefore, the detection of exoDNA would be a sensitive and accurate method for diagnosis of *Mtb* infection [35].

### **6. Basic needs of exosomes as a biomarker content in the diagnosis and treatment of TB**

*Mtb* causes the high morbidity and mortality for human TB. The pathogenesis of *Mtb* is very complex and is difficult to explained the mechanism of infection into human beings. The current TB diagnosis tools is inadequate and had several shortcomings on *Mtb* pathobiology. The study of the genetic diversity, pathogenesis of the *Mtb* through multi-omics approach leads to development of host biomarker in early diagnosis of TB. The discovery of new biomarkers has a great challenge on TB prevention and treatment. The search of a suitable biomarker for early diagnosis of TB is a great achievement in clinical context. TB remains a worldwide problem of human health. In order to prevent the TB infection, we must need the accurate vaccine development and reliable diagnostic tools.

Exosomes were isolated from human body fluids and considered for early detection of *Mtb* for diagnosis. From the above descriptive research papers, the research on the *Mtb*-derived exosomes (Mtbexo) is still at the preliminary stage and miRNA, protein, or DNA content of the *Mtb*-derived exosome from TB patients could possible for making a road map for biomarker discovery for the early diagnosis, treatment, and prevention of TB.

### **7. Conclusion**

Exosome emerged as a potent genetic information for therapeutic potential through transfer agents corroborating a range of biological processes. Exosomes were used as a research tool for diagnosis and treatment of TB because the exosomes were released from cells packaged with biochemical materials. The characterization and detection of various packaged biochemical materials in exosome could make a future roadmap for the diagnosis and treatment of TB in human population level.

### **Acknowledgements**

Indian Council of Medical Research, Govt. of India is acknowledged. N S Manisha, Odisha University of Agriculture and Technology, Odisha, India is highly praised for assisting making tables and pictures in the book chapter. Thanks to Mrs. Usha Padhee, Indian Administrative Service, Principal Secretary for a supportive stand on the road map for Tuberculosis.

### **Author details**

Sushanta Kumar Barik\* and Jyotirmayee Turuk\* Tuberculosis Division, ICMR-Regional Medical Research Centre, Chandrasekharpur, Bhubaneswar, Odisha, India

\*Address all correspondence to: sushantakumarbarik82@gmail.com and drjyotirmayeetruk@gmail.com

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Section 3
