Acquired Immune Deficiency Syndrome - Term Paper Example

? Acquired Immune Deficiency Syndrome 25 AUG AIDS – Acquired Immune Deficiency Syndrome Introduction: AIDS was first recognized in the U.S. in 1981, the primary approach employed in identifying patients was through the identification of several opportunistic infections. Pneumosystis pneumonia is one the several opportunistic infections which provided a mean to identify AIDS patients. It is characterized by the presence of profound defects of cellular immunity, these defects are a distinguishing feature as they are absent in other cases of immunodeficiency syndromes. According to the Centers for Disease Control and Prevention, individuals are classified as having AIDS if they have a positive HIV serology along with certain infections and malignancies such as pulmonary tuberculosis and cervical cancer, which can also occur in immunocompetent individuals but are more common in HIV positive individuals. Human Immunodeficiency Virus (HIV): AIDS is classified as a secondary immunodeficiency syndrome and is caused by human immunodeficiency virus (HIV). HIV belongs to the family Lentiviridae. AIDS is caused by two types of human immunodeficiency viruses, namely the HIV-1 and HIV-2. Most cases of AIDS in U.S. Canada and Europe are normally due to HIV1. Whereas HIV2 is responsible for AIDS in West Africa and it is less virulent than HIV1. DNA sequencing of HIV2 reveals that it is closely related to simian immunodeficiency virus (SIV). On the contrary, HIV1 is not even remotely related to HIV2 and SIV. Immune system and HIV: Specific targets of HIV are TH cells, macrophages, dendritic cells and Langerhans cells which have CD4 molecule on their plasma membrane. TH cells are responsible for the synthesis and secretion of cytokines, which stimulate the cytotoxic T cells to carry out cytosis of infected host cells. TH cells also mediate the B-cell antibody production. Dendritic cells are immune cells that are involved in the presenting of antigenic materials on their surface in order to stimulate an immune response. Dendritic cells are present on the inner lining of lungs and nose and the digestive tract. Macrophages are cells of the immune system that destroy free viruses by the process of phagocytosis and act as antigen presenting cells, and lead to the activation of both B and T lymphocytes. Macrophages secrete interleukin 1 which activates specific B and T cell clones that have surface receptors complementary to the viral antigens. Langerhans cells are specialized dendritic cells present in the skin. These reside in the epidermal layer of the skin and are involved in phagocytosis of antigenic foreign particles and also act as antigen presenting cells. The skin has approximately 800/mm2 of dendritic cells. (AIDS. New York: Facts on File by Flanders, S. A., & Flanders, C. N. 1991). Transmission: All acts which result in the transmission of body fluids carry a risk of transmitting HIV infection from an infected individual to an uninfected individual. Sexual transmission: All forms of unprotected heterosexual and homosexual intercourse transmit HIV infection. Direct contact of sexual secretions of an HIV positive individual with genital, rectal or oral mucous membranes of an uninfected individual result in the transmission of HIV infection. Sharing of unsterilized needles: The sharing of unsterilized intravenous needles by drug users also carries a risk of transmitting HIV infection. HIV contaminated blood transfusion: HIV contaminated blood transfusion has been responsible for numerous AIDS cases in the 1980s. In particular, people at risk are hemophiliacs who regularly receive injections of blood products. Placental transmission from an infected mother to an infant: Approximately 25% of the infants born to HIV positive mothers have HIV infection. HIV transmission occurs through the uterus during parturition. The virus is also transmitted to the infant through breast feeding. Preliminary studies reveal that there are greater chances of HIV transmission to the infant during parturition than during the period of gestation. (AIDS. New York: Rosen Cefrey, H.2001). Pathogenesis of HIV infection and AIDS: HIV affects all immune cells that have CD4 antigens, these antigens serve as attachment sites for the virus. Chemokine co-receptors mediate the entry of the virus into the host cells. However, individuals who lack Chemokine co-receptors have a lower chance of developing HIV infection but if these individuals do become infected, the disease progression is slow. Establishment of the latent state is characterized by the integration of viral genome into the host cell genome. Principally, CD4 lymphocytes are affected which coordinate the immune response. As the duration of infection prolongs there is a decrease in the number of circulating CD4 lymphocytes. This Quantitative defects of the immune system leads to a number of opportunistic infections. B lymphocytes and macrophages are also infected by HIV. Mainly, B lymphocytes defects are mediated due to the abnormal activities of TH cells since B cell activities are regulated by TH cells, which leads to hypergammaglobulinemia and this condition further depresses the response of B lymphocytes to foreign antigens. Macrophages serve as a reservoir of HIV and dispense it to other cells of the immune system. Furthermore, HIV infection leads to neuropathology which occurs due to a large secretion of variety of neurotoxins by viral infected macrophages. Perturbations of excitatory neurotransmitters and calcium flux leads to neurologic dysfunction. The virus directly also infects the kidneys (renal tubular cells) and gastrointestinal epithelium. Signs and symptoms of HIV infection: Most HIV positive individuals remain asymptomatic for years. In many cases, there is a mean time of about 10 years from the time of exposure to the development of symptoms. Symptoms of HIV infection include hairy leukoplakia of the tongue, Kaposi sarcoma, and generalized lymphadenopathy. A wide variety of opportunistic infections and malignancies are common in HIV positive individuals such as Pneumocystis jiroveci infection, Mycobacterium avium infection, Toxoplasmosis, Lymphoma, Cryptococcal Meningitis, Cytomegalovirus infection, Esophageal Candidiasis, Herpes Simplex infection, Herpes Zoster, and Kaposi sarcoma, Preventive measures: I. Practicing safe sex: Prevention of HIV infection involves practicing safe sex by using latex condoms. Natural skin condoms should not be used as they allow the passage of the virus. However, use of condoms does not completely eliminate the chance of transmission because they have a failure rate of 17 to 54%. II. Using sterilized needles: Prevention of HIV infection involves the use of sterilized needles in hospitals as well as by drug users. This efficiently breaks the transmission cycle. III. Scanning of blood and blood related products before transfusion: Donated blood should be routinely scanned for HIV antibodies. Even today, about a quarter of 2.5 million units of blood which is administered in Africa are not screened for HIV. This accounts for the increased number of AIDS cases being reported in Africa. IV. HIV positive mother is given an injection of AZT during the last few weeks of pregnancy. This reduces the chance of HIV transmission from the positive mother to infant to half. Medical Treatment: Some of the drugs used in the treatment of AIDS related opportunistic infections are given below: I. Pneumocystis jiroveci infection: 15 mg/kg/d of Trimethoprim-sulfamethoxazole are administered either orally or intravenously for 14-21 days 3-4 mg/kg/d of Pentamidine are administered intravenously for 14-21 days. II. Mycobacterium avium complex infection: 500 mg of Clarithromycin administered orally twice daily along with ethambutol. III. Toxoplasmosis: 100-200 mg of Pyrimethamine is administered orally as a loading dose along with sulfadiazine 4-6 g orally in four divided doses, 10 mg daily of folinic acid for 4-8 weeks IV. Lymphoma: Combination chemotherapy is the choice of treatment. V. Cytomegalovirus infection: 900 mg of Valganciclover is given orally with 900 mg of food twice daily for 21 days. VI. Cytococcal meningitis: Amphotericin B 0.6 mg /kg/d is administered intravenously. VII. Esophageal candidiasis or recurrent vaginal candidiasis: Fluconazole 100-200 mg is administrated orally daily for 10-14 days. VIII. Herpes simplex infection: 400 mg of Acyclovir is administered orally thrice daily until the infection is healed. (AIDS: Etiology, diagnosis, treatment, and prevention. Philadelphia: Lippincott-Raven by DeVita et al) Conclusion: With vast improvements in medical treatments, patients now have a longer life expectancy after being diagnosed with AIDS. Recently, a population based study conducted in Denmark revealed that HIV infected people at the age of 25 years who do not have hepatitis C have a life expectancy of about 35 years. The high death rate associated with AIDS is due to the fact that all HIV infected individuals do not have access to treatment. References: Flanders, S. A., & Flanders, C. N. (1991). AIDS. New York: Facts on File. Cefrey, H. (2001). AIDS. New York: Rosen DeVita, V. T., Hellman, S., & Rosenberg, S. A. (1997). AIDS: Etiology, diagnosis, treatment, and prevention. Philadelphia: Lippincott-Raven. Read More