The immune systems role in protecting the normal physiological well-being of the human body is of great importance, in preventing infections acquired from the external environment. Our body is in a constant warfare with a lot of causative agents of disease such as fungi, bacteria and viruses. It is therefore necessary to have an effective defence against these agents. An immune deficient person is more susceptible to opportunistic attacks and is more prone to developing several diseases, due to lack of a sufficient defence mechanism against infections. Also the balance between the normal microbiota and pathogenic organism is upset and the person is more likely to be susceptible to organisms that are ubiquitous or suppressed in normal circumstances. HIV or human immunodeficiency virus is the cause AIDS or Acquired Immunodeficiency Syndrome, which is a worldwide health problem. With an estimated death of 2.0 million people in 2008 (World Health Organization 2010) AIDS has become a pandemic worldwide primarily due to increase promiscuity in society. The cost of AIDS as a result of HIV infection, is not only measured in human lives, but also inhibition of a country's economic progress due to loss of human capital and a skilled workforce.
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HIV is a lentivirus that is commonly transmitted through unprotected sexual intercourse with an infected partner, infection via bodily fluids semen or saliva or contamination with another person's blood, such as in the case of sharing needles among drug abusers. HIV is a retrovirus, having a single stranded RNA as its genome and contains the enzyme reverse transcriptase, to synthesize DNA once inside the host cell. It specifically attacks the CD4 receptors of the T-Helper cells. T-Helper cells are necessary for cell-mediated immunity, and lack of these cells decreases a person's immunity, making him or her more vulnerable to infections. The mechanism for HIV infection is the attachment of the gp120 envelope glycoprotein to the CD4 receptors on the surface of the T-helper cells. Once infection is established, the virus uses the T-helper cells' mechanism for its own replication and propagation.
Initially the body's immune system counter-attack the virus by producing antibodies against the viral proteins. Once these antibodies for the viral proteins are produced, they are present in the infected person's serum and the individual is said to be seropositive for HIV (Goldsby et al 485) The T-helper cells are also attacked by macrophages, monocytes, dendritic cells and CD8-cytotoxic T-cells recognising the virus as a foreign antigen. HIV infection transforms into full blown AIDS once a significant amount of T-helper cells decrease and the viral count increases, thus rendering the person open for other infections. Several acquired infections over time increases the person's mortality and death ensues. A count of less than 200 cells per mm3 T-helper cells, makes a person open for other infections (Goldsby et al 485) and increases the viral count significantly. The symptoms of AIDS, from the initial infection of the HIV virus till death usually take many years (11-20 yrs in some patients). This is known as the chronic phase.
Symptoms of AIDS vary, depending on the infections acquired. Primary symptoms usually include fever and a rash which usually goes away once the patient has reached the chronic phase of the disease. One of the most common infection acquired by AIDS patient is Candidiasis, caused by the fungus Candida Albicans. This fungi is normally harmless and is part of the body's normal microbiota in the gastro-intestinal tract and the vaginal area. Its growth is suppressed by the immune system but a person with AIDS lacks sufficient defence mechanism to suppress its growth and the person develops Candidiasis. C. Albicans is a strict aerobe, therefore the classical symptoms of the infection associated with Candiasis often occurs in the skin and also sometimes in the genital area. The symptom of Candidiasis is thrush, which appears as whitish-yellowish flakes that cover the skin or the genital area. This is usually a problem for the newborn if the mother's vaginal area is heavily colonized by the fungus, it can pass through the child's upper respiratory tract who has not acquired the normal microbiota yet, during passage in the birth canal (Willey et.al pg 1017)
The mortality rate for candidiasis is 50% when Candida invades the blood and spread to visceral organs (Willey et.al 1018) As stated above most infections acquired as a result of HIV infection, comes from microorganisms that are ubiquitous in nature. Another common infection in AIDS patients as a result of HIV infection is Aspergillosis. The fungi that causes Aspergillosis is Aspergillus Fumigatus and are found in water, soil, dust and decaying plants. This fungi can cause allergic bronchitis and bronchopulmonary infections (Willey et.al pg 1016). Aspergillosis usually occurs in persons with T-helper cell count of less than 50 cells per microlitre, Candidasis occurs when T-helper cell count is less than 350 cells/microlitre (World Health Organization 2009). Common manifestation of the disease include bronchitis due to hypersensitivity allergic reactions.
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Aspergillosis can be invasive, when subsequent infection to the fungi results in colonization of the organism in the lungs and other organs. Immunodeficient people, such as patiens are at risk of having their lungs filled with fungal hyphae. Intraconazole is the drug used for the management of aspergillosis, however a medical study have shown that there is a definite increase in this infection as the number of HIV infection increased over the years. It is uncertain as to what other co-factors, which may have caused an increase in the incident of Aspergillosis. Perhaps it could be due to prior pneumonia (which is very common among AIDS patients) which may have reduced macrophage functions. Contaminated air, such as smoking marijuana may also play a role (Ampel 1996 pg 110)
It can be seen from the two common fungal pathogens mentioned that the role played by the immune system, is of great importance in preventing opportunistic attacks. A significant amount of T-helper cell count has to be present in the host in order to provide sufficient protection against these ubiquitous microorganisms. Other co-factors may lead to the exacerbation of fungal infection such as in the case of aspergillosis. Prognosis for AIDS patients unfortunately is that of a negative one as T-cell count drastically decrease, the person's immune system fails and he or she remains open for infections other than fungal infections.