ABOUT AIDS Literature Exploration

Definition of AIDS

Clinical Course of HIV Infection

Routes of Transmission

Diagnosis

Treatment

Definition of AIDS

AIDS is manifested as a collection of diseases resulting from severe immunosuppression due to HIV infection. AIDS is clinically defined as the stage when an HIV-infected person's CD4+ lymphocyte count falls below 200 per microliter or the HIV-infected person has any of the AIDS-defining clinical illnesses as described below. Variation of illnesses among HIV-infected people may be due to the effectiveness of host immune response and the degree of viral virulence.

The following are seen commonly among individuals with AIDS. Because the immune system is "knocked out" as AIDS progresses, a person can sustain many other types of complications which may vary in intensity from less serious to lethal.

• Kaposi's sarcoma (KS)
  A form of malignant neoplasm, KS usually starts as benign-appearing endothelial lesions that can regress spontaneously. Growing lesions may progress to tumors with local invasion and lymph node metastasis. Lesions are characterized by reddish purple patches, plaques, or nodules over the skin. KS can be diagnosed with skin biopsy and can occur before the onset of severe immunosuppression.
• Fungal Infections
  Although many types of fungi can increase in severity due to AIDS, the most common is the yeast Candida albicans. This organism and related yeasts can occasionally produce invasive infections in the esophagus, upper respiratory tract, and lung. Other serious fungal infections are caused by Cryptococcus neoformans (meningitis and pneumonia) and Apergillus sp. (pneumonias).
• Protozoal Infections
  Toxoplasma gondii is a protozoan parasite that often causes brain infections in people with AIDS. There are usually multiple lesions and the appearance of abscesses. Cryptosporidium may cause extremely large amounts of watery diarrhea. Without proper replacement therapy, gastrointestinal infections may be fatal. Protozoal infection can be diagnosed by examination of stool specimens and/or intestinal biopsy.
• Pneumocystis carninii Pneumonia (PCP)
  This is the most frequent opportunistic infection seen in AIDS patients. This parasite produces a pulmonary infection which rarely disseminates outside of the lungs. Acute onset of fever, non-productive coughing, and shors of breath are characteristic of people with PCP.
• Mycobacterial Infections
  Mycobacterium tuberculosis causes pulmonary disease in people with and without AIDS, although the course of the disease is more severe and rapid in AIDS patients. Mycobacterium avium complex (MAC) infection is rarely seen in people without AIDS; it causes disease in organs of the mononuclear phagocyte system (lymph nodes, spleen, liver, bone marrow). MAC infections are less likely to produce visible granulomas, and the lesions often consist of clusters of macrophages filled with numerous mycobacteria.
• Herpes Viruses
  Herpes simplex virus (HSV) infection primarily involves the esophagus and perianal region of the gastrointestinal tract. Herpes zoster infection of skin can occur prior to the onset of clinical AIDS. Fortunately, herpes infection are rarely life-threatening. Cytomegalovirus(CMV) effectively circulates throughout the bodies of people with AIDS. When CMV is found in lungs, it causes pneumonia; however, CMV is known to cause disease in brain tissue and gastrointestinal tract. In addition, CMV commonly leads to retinitis in people with AIDS.

Clinical Course of HIV Infections

Following infection, the lymphoid organs (major site of immune cell activity) have not had time to mount an effective immune response and thus the virus begins to replicate. During this acute phase, activity of cytotoxic T cells increases and ultimately the number of circulating virus is held to a level that is manageable by the body. This level varies from person to person and may affect how long the subsequent inapparent clinically latent phase lasts. The average period of clinical latency is about ten years. Some HIV (+) people however can develop AIDS-defining diseases within 1 year of infection, while others have shown no clinical signs of the disease for more than a 15 years. The overtly deteriorating phase of infection, defining AIDS, occurs when the body can no longer contain the viral load. At this wasting stage, AIDS patients succumb to secondary infections, cancer, and nervous system deterioration leading to death.

Routes of Transmission

• Sexual transmission
• Parenteral inoculation
• Maternal transmission

  HIV is not transmitted by the following:

Diagnosis

The most common HIV test detects the presence of antibodies against the internal HIV antigen, gp24. This test, the ELISA (enzyme-linked immunoabsorbant assay) may be negative in an infected person if performed before antibodies have developed. A negative test should be repeated until at least 6 months have passed since exposure. A positive test must be followed by a more specific antibody test such as the Western blot.

More sensitive techniques include polymerase chain assay (PCR) to amplify specific viral genes and Branched DNA-Signal Amplification Assay (BD-SAA) to quantify HIV-1 ribonucleic acid.

Treatment

There are many drugs used to alleviate the painful effects of AIDS-defining illnesses. There are also drugs available that are targeted at different HIV gene products or at different stages of the viral replication cycle. A combination drug therapy appears to reduce viral load but as yet there is no known cure for HIV infection.

The combination drug therapies include using AZT, ddI or ddC, all reverse transcriptase inhibitors along with recently approved protease inhibitors that attack the viral protease necessary in the latter stages of the replication cycle.

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