Preface

Cysticercosis, caused by the larval stage of *Taenia solium*, is a serious health and veterinary problem in many developing countries and is considered one of the most important neglected tropical diseases in developed countries. In humans, *T. solium* cysticerci cause neurocysticercosis, which affects approximately 50 million people worldwide and is considered an emergent disease in the United States. *T. solium* also infects pigs, its intermediate hosts, leading to major economic losses. When humans ingest undercooked contaminated pork meat, the adult worm develops in the small intestine. After two months of asymptomatic infection, this tapeworm starts producing thousands of eggs that, once released with stools, can contaminate the environment, infecting pigs (rapidly differentiating into cysticerci mainly in the muscle) and humans (where most severe symptoms are observed due to the presence of cysticerci in the brain). Thus, maintenance of the parasite's life cycle depends on the adult tapeworm development. Even in communities that do not rear or consume pigs, human neurocysticercosis can be found, because of the presence of a tapeworm carrier. Furthermore, tapeworm development depends on scolex evagination, the initial step through which a single cysticercus becomes an adult parasite with the capability of producing infective eggs. There has been a great deal of scientific advances in this field, including in vaccination, epidemiology, current drug design, diagnostics, and host-parasite interaction at all levels. However, to date, there is no book that discusses these advances in detail. As such, this book provides a comprehensive overview of the current state of the art in taeniosis/ cysticercosis. It discusses recent advances in the study of cysticercosis and taeniosis, incuiding topics such as clinical disease, vaccines, immune response diagnostics, and new possible drug targets.

The book begins with a discussion in Chapter 1 by Medina Néri et al. about cardiac cysticercosis, a rare infection whose diagnosis is usually incidental because most patients are asymptomatic. Laboratory and imaging tests, such as echocardiogram and cardiac nuclear magnetic resonance, can also be used in the diagnostic approach. The clinical manifestations are broad, and patients can present with symptoms that range from heart failure to arrhythmias. Treatment of this condition has been scarcely studied and no protocols have been well established to date. One can choose not to treat the asymptomatic cases or to use cestocides, in the case of symptomatic individuals. Patient monitoring through cardiac enzymes and electrocardiogram during treatment is recommended, as well as performing imaging tests after treatment. Thus, the chapter discusses cardiac cysticercosis, covering everything from its epidemiology and clinical aspects to diagnostic methods, therapeutics, and treatment monitoring, with emphasis on the most current aspects.

In Chapter 2, Marisela Hernández et al. describe the most important advances in the development of an oral vaccine against porcine cysticercosis. Parasitic, fecally transmitted diseases, such as taeniasis/cysticercosis, represent a health problem with continued incidence due to the prevalence of inadequate sanitary conditions, particularly in developing countries. When the larval stage of the parasite is established in the central nervous system it causes neurocysticercosis, a disease that can severely affect human health. It can also cause cysticercosis in pigs, resulting in economic

losses. Since pigs are obligatory intermediate hosts, they are considered targets for vaccination to interrupt the transmission of parasitosis and eventually reduce disease. Progress has been made in the development of vaccines for the prevention of porcine cysticercosis. The authors' research group identified three peptides that, when expressed synthetically (S3Pvac) or recombinantly (S3Pvac-phage), reduced the amount of cysticerci in pigs exposed to natural conditions of infection by 98.7% and 87%, respectively. Considering that cysticercosis is orally acquired, it seems feasible to develop an edible vaccine to be administered by pig farmers, simplifying the logistical difficulties of its application, reducing costs, and facilitating the implementation of vaccination programs.

In Chapter 3, Olguín et al. discuss the general differences between the different types of immunoregulation, the kind of cellular populations of the immune system used by the helminths *T. solium* and *T. crassiceps* to induce immunoregulation and immunosuppression, and the mechanisms used by these parasites such as mimicking molecules of the immune system to replace these mechanisms directly. We have learned some critical lessons about the relationship between the human body and its interaction with many infectious diseases, where the immune system has a major role in protection. We learned to differentiate between the immune response occurring in either an intracellular or extracellular parasitic infection, between innate and adaptative immune response, between either inflammatory or anti-inflammatory responses, and finally, we learned to recognize very particular mechanisms, such as the inability of the immune system to respond during certain scenarios, such as the inability of T cells to both proliferate and produce cytokines even after their exposure to mitogens or specific antigens. Along with our increased knowledge of immunology, we figured out that immunoregulation and immunosuppression are processes used by many parasites to reduce the capacity of the immune system to eliminate them, and to persist in the host favoring their transmission and completing their life cycles. Immunoregulation involves several mechanisms such as anergy, apoptosis, induction of both suppressive cytokines and membrane-bound molecules, as well as specialized cell populations of the immune system like regulatory T cells, alternatively activated macrophages, or myeloid-derived suppressor cells, which together modify the outcome of the immune response. Understanding and deciphering all these regulatory mechanisms could be useful for developing new tools to control this infection.

In Chapter 4, Esquivel-Velazquez et. al. delves into the diagnosis of neurocysticercotic patients, the complex nature of cysticercosis disease, and the simplicity of common immunological assumptions involved in explaining the low scores and reproducibility of immunotests in the diagnosis of neurocysticercosis. To begin with, the few studies dealing with the immune response during neurocysticercosis are not conclusive, which of course is crucial for developing an immunodiagnostic test. Their full recognition should clear up confusion and reduce controversy as well as provide avenues of research and technological design. In this chapter, logical arguments add that even under common immunological assumptions, serology of neurocysticercosis will always include false negative and positive results. Thus, serology is no strong support for medical diagnosis of neurocysticercosis. In contrast, immunotests performed in the cerebrospinal fluid (CSF) of neurological patients should have fewer false positives and fewer false negatives than in serum. To conclude, it is argued that high scores in serology for neurocysticercosis will not yield to usual approaches and that success needs a concerted worldwide effort. A more punctilious strategy based on the design of panels of confirmed positive and negative sera needs to be construed, shared, and tested by all interested groups to

**V**

targets.

obtain comparable results. The identification of a set of specific and representative antigens of *T. solium* and a thorough compilation of the many forms of antibody response of humans to the many forms of *T. solium* disease are also to be considered

In Chapter 5, Matías Gastón Pérez discusses the role of MicroRNAs (miRNAs) in taeniosis/cysticercosis. miRNAs are found in animals, plants, and some viruses and belong to the heterogeneous class of non-coding RNAs (ncRNAs), which post-transcriptional activity regulates gene expression. They are linked to various cellular activities such as cell growth, differentiation, development, and apoptosis. In addition, clinical trials targeting miRNAs in cancer, metabolic diseases, and viral infections have shown promising results. The chapter provides an overview of *T. solium* and *T. crassiceps* miRNAs, their possible biological functions, their role in host-parasite communication, and their potential role as biomarkers and drug

In Chapter 6, Zubillaga et al. discuss the role of cytosolic glutathione transferases (GSTs) as potential drug targets. Helminth cytosolic glutathione transferases (GSTs) are essential enzymes involved in the regulation of immune responses, transport, and detoxification. In *T. solium*, three cytosolic GSTs with molecular masses of 26.5 (Ts26GST), 25.5 (Ts25GST), and 24.3 kDa (TsMσGST), classified as mu-class, mu-alpha, and sigma GST-classes, respectively, constitute the main detoxification system, and they may be immune targets for the development of vaccines and new anthelmintics. The authors performed a successful virtual screen, and identified I7, a novel selective inhibitor of Ts26GST that showed a non-competitive inhibition mechanism towards substrate glutathione with a Ki of 55.7 mM and mixed inhibition towards the electrophilic substrate 1-chloro-2,4- dinitrobenzene with a Ki of 8.64 mM. Docking simulation studies showed that I7 binds to a site adjacent to the electrophilic site and the furthest from the glutathione site. This new inhibitor of Ts26GST will be used as a lead molecule to develop new effective and safe drugs

In Chapter 7, Ríos-Valencia et al. discuss the post-genomic era of *T. solium*

cestodes and addresses the use and processing of host proteins.

research. Cestode parasites rely on their host to obtain their nutrients. Elucidation of tapeworm genomes has shown a remarkable reduction in the coding of multiple enzymes, particularly those of anabolic pathways. Previous findings showed that 10%–13% of the proteins found in the vesicular fluid of *T. solium* cysticerci are of host origin. Further proteomic characterization allowed identification of 4,259 different proteins including 891 of host origin in the parasite's protein lysates. One explanation for this high abundance and diversity of host proteins in the parasite lysates is related to the functional exploitation of host proteins by cysticerci. Supporting this concept is the uptake of host haptoglobin and hemoglobin by the parasite as a way to acquire iron. Surprisingly, internalized host proteins are minimally degraded by the parasite's physiological machinery. Additional proteomic analysis demonstrated that these host proteins become part of the organic matrix of calcareous corpuscles as 60%–70% of the protein content is host proteins. This chapter assembles a collection of available genomic and proteomic data for taeniid

Finally, in Chapter 8, Romano et al. examine the host-parasite relationship and the host's hormonal environment, which determines susceptibility to and the course and severity of several parasite infections. In most cases the infection disturbs the host environment and activates immune responses that end up affecting the

as one of the most important factors to the disease.

against diseases caused by *T. solium*.

obtain comparable results. The identification of a set of specific and representative antigens of *T. solium* and a thorough compilation of the many forms of antibody response of humans to the many forms of *T. solium* disease are also to be considered as one of the most important factors to the disease.

In Chapter 5, Matías Gastón Pérez discusses the role of MicroRNAs (miRNAs) in taeniosis/cysticercosis. miRNAs are found in animals, plants, and some viruses and belong to the heterogeneous class of non-coding RNAs (ncRNAs), which post-transcriptional activity regulates gene expression. They are linked to various cellular activities such as cell growth, differentiation, development, and apoptosis. In addition, clinical trials targeting miRNAs in cancer, metabolic diseases, and viral infections have shown promising results. The chapter provides an overview of *T. solium* and *T. crassiceps* miRNAs, their possible biological functions, their role in host-parasite communication, and their potential role as biomarkers and drug targets.

In Chapter 6, Zubillaga et al. discuss the role of cytosolic glutathione transferases (GSTs) as potential drug targets. Helminth cytosolic glutathione transferases (GSTs) are essential enzymes involved in the regulation of immune responses, transport, and detoxification. In *T. solium*, three cytosolic GSTs with molecular masses of 26.5 (Ts26GST), 25.5 (Ts25GST), and 24.3 kDa (TsMσGST), classified as mu-class, mu-alpha, and sigma GST-classes, respectively, constitute the main detoxification system, and they may be immune targets for the development of vaccines and new anthelmintics. The authors performed a successful virtual screen, and identified I7, a novel selective inhibitor of Ts26GST that showed a non-competitive inhibition mechanism towards substrate glutathione with a Ki of 55.7 mM and mixed inhibition towards the electrophilic substrate 1-chloro-2,4- dinitrobenzene with a Ki of 8.64 mM. Docking simulation studies showed that I7 binds to a site adjacent to the electrophilic site and the furthest from the glutathione site. This new inhibitor of Ts26GST will be used as a lead molecule to develop new effective and safe drugs against diseases caused by *T. solium*.

In Chapter 7, Ríos-Valencia et al. discuss the post-genomic era of *T. solium* research. Cestode parasites rely on their host to obtain their nutrients. Elucidation of tapeworm genomes has shown a remarkable reduction in the coding of multiple enzymes, particularly those of anabolic pathways. Previous findings showed that 10%–13% of the proteins found in the vesicular fluid of *T. solium* cysticerci are of host origin. Further proteomic characterization allowed identification of 4,259 different proteins including 891 of host origin in the parasite's protein lysates. One explanation for this high abundance and diversity of host proteins in the parasite lysates is related to the functional exploitation of host proteins by cysticerci. Supporting this concept is the uptake of host haptoglobin and hemoglobin by the parasite as a way to acquire iron. Surprisingly, internalized host proteins are minimally degraded by the parasite's physiological machinery. Additional proteomic analysis demonstrated that these host proteins become part of the organic matrix of calcareous corpuscles as 60%–70% of the protein content is host proteins. This chapter assembles a collection of available genomic and proteomic data for taeniid cestodes and addresses the use and processing of host proteins.

Finally, in Chapter 8, Romano et al. examine the host-parasite relationship and the host's hormonal environment, which determines susceptibility to and the course and severity of several parasite infections. In most cases the infection disturbs the host environment and activates immune responses that end up affecting the

endocrine system. Several reports indicate that parasites have reproductive systems, and some others have shown that these organisms synthesize sex steroid hormones. The authors show that the cysticerci of *T. crassiceps* and *T. solium* have the capacity to synthesize corticosteroids such as deoxicorticosterone and corticosterone. They also discuss the effects of thyroid hormones and infection with *T. solium* cysticerci (neurocysticercosis), and state that infection causes endocrine alterations in male and female patients.

This book assembles novel and important information about a disease that is a health burden in underdeveloped countries an emerging health problem in developed ones. We hope that readers find it a useful reference.

#### **Jorge Morales-Montor**

Departamento de Inmunología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad de México, México

#### **Luis Ignacio Terrazas**

Unidad de Investigación Biomédica, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, Ciudad de México, México

#### **Abraham Landa**

Facultad de Medicina, Departamento de Microbiología y Parasitología, Universidad Nacional Autónoma de México, Ciudad de México, México Section 1
