**4. Haematologic aspects of HIV infection**

#### **4.1. Normal haemopoiesis**

Haemopoiesis is the formation of blood or blood cells in the living body. It involves the production of three (3) major cell lines which are red blood cells, white blood cells and platelets [37]. In humans, this process occurs in the bone marrow. In certain diseases, the process can be altered either directly or indirectly. Patients with HIV infection will have altered haemo‐ poiesis [38], affecting both red and white blood cells and platelet formation.

Haemopoietic stem cells (HSCs) are the earliest cells recognized in the bone marrow (Figure 2). HSCs produce all blood cells [37]. About 5% of the HSCs in the bone marrow are functioning at one time, thus maintaining the haemopoietic system for the lifetime in a human body. Growth factors, also play an important role for production and differentiation of blood cells in the bone marrow. Erythropoietin, a type of hormone which is mainly produced by the kidney and thrombopoietin, which is mainly produced by the liver, are the growth factors that are necessary for production and proliferation of red blood cells and platelets respective‐ ly.White blood cells have five (5) major components which include neutrophil, monocyte, eosinophil, basophil and lymphocyte. The lymphocytes are further subdivided into Blymphocytes and T-lymphocytes, which are important for functional activity.

In most circumstances, HIV infection causes reduction in blood cell formation [40]. These include red blood cell (anaemia), platelet (thrombocytopenia) and white blood cell (leucope‐

The diagram illustrates the hematopoiesis process that occurs in the bone marrow which gives rise to production of various cell lines from the marrow stem cell.

**Figure 2.** Production of red and white blood cells and platelets in the bone marrow [39]

nia) or any combination of these lineages (Table 6). The cause of these changes in HIV infection are not fully understood.


**Table 6.** Haematological abnormalities in HIV infection and normal adult reference values.

#### **4.2. Haematological changes in HIV infection**

stimulation with IFN-γ. The production is increased in HIV infection and infection by intracellular organisms such as parasite, autoimmune disease, malignant tumours, allograft rejection, neurological as well as cardiovascular disease [33]. However, it has slightly low predictive value compared to beta-2 microglobulin [5]. Neopterin and beta-2 microglobulin levels were proved to be significant predictors of AIDS risk in HIV-1 seropositive patients. The

beta-2 microglobulin are recommended to be used as an additional marker to predict AIDS risk for HIV-1 seropositive patients and is beneficial particularly in the setting where the CD4+

Oxidative stress is a condition in which there is increased amounts of reactive oxygen or nitrogen species. This condition is now recognized to be a prominent feature of many acute and chronic disease and even in normal ageing process. Lipid peroxidation was found to be one of the biomarkers to assess oxidative stress status in human disease including HIV [23]. A study done by Friis-Moller *et al*. [35] have shown that HIV-infected patients have oxidative imbalance early in the disease; low serum and tissue antioxidants and elevation of peroxidation products. Besides, high plasma levels of malondialdehyde (MDA), reduced plasma gluta‐

Haemopoiesis is the formation of blood or blood cells in the living body. It involves the production of three (3) major cell lines which are red blood cells, white blood cells and platelets [37]. In humans, this process occurs in the bone marrow. In certain diseases, the process can be altered either directly or indirectly. Patients with HIV infection will have altered haemo‐

Haemopoietic stem cells (HSCs) are the earliest cells recognized in the bone marrow (Figure 2). HSCs produce all blood cells [37]. About 5% of the HSCs in the bone marrow are functioning at one time, thus maintaining the haemopoietic system for the lifetime in a human body. Growth factors, also play an important role for production and differentiation of blood cells in the bone marrow. Erythropoietin, a type of hormone which is mainly produced by the kidney and thrombopoietin, which is mainly produced by the liver, are the growth factors that are necessary for production and proliferation of red blood cells and platelets respective‐ ly.White blood cells have five (5) major components which include neutrophil, monocyte, eosinophil, basophil and lymphocyte. The lymphocytes are further subdivided into B-

In most circumstances, HIV infection causes reduction in blood cell formation [40]. These include red blood cell (anaemia), platelet (thrombocytopenia) and white blood cell (leucope‐

thione (GSH) and decreased superoxide dismutase activities were also found [36].

poiesis [38], affecting both red and white blood cells and platelet formation.

lymphocytes and T-lymphocytes, which are important for functional activity.

T cell counts. Therefore, neopterin and

predictive value of both parameters is equal to CD4+

116 Trends in Basic and Therapeutic Options in HIV Infection - Towards a Functional Cure

**4. Haematologic aspects of HIV infection**

**4.1. Normal haemopoiesis**

T cell count measurement is not available [34].

*3.4.4. Biomarker*

Haematological abnormalities are common complications of HIV infection. These abnormal‐ ities increase as the disease advances. On both antiretroviral-treated and untreated individuals, different types of haematological abnormalities are common [41, 42, 43, 44] (Table 6).

Since the impact of HIV infection can be found in the peripheral blood and bone marrow, disorders of the haemopoietic system include anaemia, leucopenia, thrombocytopenia and thrombosis. These could be because of direct effects of the virus on the bone marrow, sup‐ pression of bone marrow by secondary infections or neoplasms causing ineffective haemato‐ poiesis, nutritional deficiencies or side effects of the drugs used [44]. The disorders commonly occur throughout the course of HIV infection.

#### *4.2.1. Blood abnormalities*

The majority of the HIV cases present haematological abnormalities in the middle or advanced stages of the infection. However, some of the changes such as low haemoglobin and platelets have been reported in the early stages of HIV infection [44].

#### *4.2.1.1. Anaemia*

Anaemia refers to decrease in the haemoglobin (Hb) concentration with reference to healthy individuals of the same age group, sex, physiological state and environment (altitude).Normal haemoglobin for men is more than 13 g/dL while for women is 12 g/dL [38]. This can be classified based on the etiology or morphology of the red blood cell. The normal red blood cell shows a normochromic normocytic morphology. Anaemia is one of the commonest abnor‐ malities seen in HIV, occurring in more than 50% of patients [40]. In a study done in HIV patients without myelosuppressive therapies, 8% of asymptomatic HIV-seropositive patients, 20% of those with symptomatic middle-stage HIV disease, and 71% of those with Centers for Disease Control (CDC)-defined AIDS were found to be anaemic [40]. Anaemia can be the earliest haematological manifestation, especially in children with HIV infection. Normochro‐ mic normocytic anaemia is the usual feature, but sometimes the HIV patients can present with a hypochromic microcytic anemia [45, 46, 47, 48, 49].

The causes of anemia in HIV patients are multifactorial. Inflammatory cytokines released by lymphocytes such as tumour necrosis factor (TNF), Interleukin-1 (IL-1) and interferon gamma play an important role in the pathogenesis of anaemia. These cytokines have been shown to inhibit red cell production (erythropoiesis) *in vitro* [51]. TNF levels were found to be consis‐ tently elevated in HIV infection and this condition is correlated with viral load [52]. Presence of dyserythropoiesis and opportunistic infections have also resulted in functional and morphological abnormalities of red blood cells [41]. This can alter the normal function of red blood cell as oxygen carrier or alter its normal biconcave shape. Other factors that contribute to the development of anaemia include underlying chronic disease, mixed nutritional defi‐ ciencies, opportunistic infections and side effects from the treatment [53]. As HIV disease progresses, the prevalence and severity of anaemia also increases [48, 54].

Disseminated Mycobacterium avium complex (MAC) disease may be present in HIV patients. It has been reported that about 76% of patients with this infection have severe anemia [52]. Another isolated red cell disorder, chronic pure red cell aplasia has been reported in HIV patients infected with parvovirus B19 [55]. This indicates that the underlying infection due to immunosuppression can give rise to anaemia.

The peripheral blood smear in Figure 3(a) appears normal morphology, this condition is a normochromic, normocytic anemia. The utilization of iron is impaired due to a cytokine-mediated blockage in transfer of iron from the storage pool to the erythroid precursors in the bone marrow. The RBC's in Figure 3(b) appear smaller than the normal mor‐ phology and have an increased zone of central pallor. This feature shows a hypochromic (less hemoglobin in each RBC) and microcytic (smaller size of each RBC) anemia.

**Figure 3.** (a) Normochromic normocytic red cells and (b) Hypochromic microcytic red cells [50]

Nutritional anaemia in HIV patients frequently arises from an inadequate balanced diet intake and malabsorption. Infection and drug toxicity are common causes of gastrointestinal disease. Vitamin B12 deficiency is seen in up to one-third of HIV-positive subjects. Iron and folate deficiency are also common in this type of patients [38]. Bone marrow infiltration by tumour, such as lymphoma, is more common among HIV patients as compared to the normal popu‐ lation.The infiltration can suppress the production of red blood cells which can lead to anaemia. Anaemia is known to occur as an adverse effect of drug therapy for HIV infection or its complications. Myelosuppression can be caused by dose limiting toxicity of zidovudine [56]. Other drugs such as primaquine, dapsone and ganciclovir can lead to anaemia in HIV patients [52]. HIV patients with lymphoma on chemotherapy may present with anaemia due to the myelosuppressive treatment.

#### *4.2.1.2. Thrombocytopaenia*

Since the impact of HIV infection can be found in the peripheral blood and bone marrow, disorders of the haemopoietic system include anaemia, leucopenia, thrombocytopenia and thrombosis. These could be because of direct effects of the virus on the bone marrow, sup‐ pression of bone marrow by secondary infections or neoplasms causing ineffective haemato‐ poiesis, nutritional deficiencies or side effects of the drugs used [44]. The disorders commonly

The majority of the HIV cases present haematological abnormalities in the middle or advanced stages of the infection. However, some of the changes such as low haemoglobin and platelets

Anaemia refers to decrease in the haemoglobin (Hb) concentration with reference to healthy individuals of the same age group, sex, physiological state and environment (altitude).Normal haemoglobin for men is more than 13 g/dL while for women is 12 g/dL [38]. This can be classified based on the etiology or morphology of the red blood cell. The normal red blood cell shows a normochromic normocytic morphology. Anaemia is one of the commonest abnor‐ malities seen in HIV, occurring in more than 50% of patients [40]. In a study done in HIV patients without myelosuppressive therapies, 8% of asymptomatic HIV-seropositive patients, 20% of those with symptomatic middle-stage HIV disease, and 71% of those with Centers for Disease Control (CDC)-defined AIDS were found to be anaemic [40]. Anaemia can be the earliest haematological manifestation, especially in children with HIV infection. Normochro‐ mic normocytic anaemia is the usual feature, but sometimes the HIV patients can present with

The causes of anemia in HIV patients are multifactorial. Inflammatory cytokines released by lymphocytes such as tumour necrosis factor (TNF), Interleukin-1 (IL-1) and interferon gamma play an important role in the pathogenesis of anaemia. These cytokines have been shown to inhibit red cell production (erythropoiesis) *in vitro* [51]. TNF levels were found to be consis‐ tently elevated in HIV infection and this condition is correlated with viral load [52]. Presence of dyserythropoiesis and opportunistic infections have also resulted in functional and morphological abnormalities of red blood cells [41]. This can alter the normal function of red blood cell as oxygen carrier or alter its normal biconcave shape. Other factors that contribute to the development of anaemia include underlying chronic disease, mixed nutritional defi‐ ciencies, opportunistic infections and side effects from the treatment [53]. As HIV disease

Disseminated Mycobacterium avium complex (MAC) disease may be present in HIV patients. It has been reported that about 76% of patients with this infection have severe anemia [52]. Another isolated red cell disorder, chronic pure red cell aplasia has been reported in HIV patients infected with parvovirus B19 [55]. This indicates that the underlying infection due to

progresses, the prevalence and severity of anaemia also increases [48, 54].

occur throughout the course of HIV infection.

have been reported in the early stages of HIV infection [44].

118 Trends in Basic and Therapeutic Options in HIV Infection - Towards a Functional Cure

a hypochromic microcytic anemia [45, 46, 47, 48, 49].

immunosuppression can give rise to anaemia.

*4.2.1. Blood abnormalities*

*4.2.1.1. Anaemia*

Platelets are produced in the bone marrow. Normal platelet count is between 150 – 400 x 109 /L. Reduction in the number of platelet count can be due to ineffective and/or reduced production of platelets in the bone marrow or increase destruction/ consumption of platelets in the peripheral blood. In HIV disease, thrombocytopaenia is the second most frequent hematolog‐ ical complication of HIV infection. It is found in 3% to 40% of individuals with HIV infection and could occur at any stage [57]. Presence of thrombocytopaenia is independent of the disease progression.

The mechanism of thrombocytopenia in HIV infection is mainly due to ineffective platelet production and at the same time increased platelet destruction [58]. There is a significant platelet sequestration and destruction in the spleen in HIV-associated thrombocytopenia. Platelet destruction normally occurs early in the course of the disease. The destruction is often antibody mediated [59]. There are HIV-specific antibodies that have been shown to share a common epitope with antibodies against glycoprotein on the platelet surface (platelet GPIIb/ IIIa) [59]. Nonspecific absorption of immune complexes onto platelets also occurs which predisposes the cell to immune thrombocytopaenia. Interestingly, there was a study that correlated the presence of lupus anticoagulant and anticardiolipin antibodies in HIV patients with the presence of thrombocytopaenia [60]. The other common cause of reduced platelet production in HIV patients is direct infection of megakaryocytes by the virus itself [61]. This gives rise to abnormal megakaryocytes morphology in the marrow. Other causes of throm‐ bocytopenia include marrow infiltration by opportunistic infection or lymphoma, presence of complications such as thrombothic thrombocytopaenic purpura, and myelosuppressive effects of drug therapy.
