Thursday, October 6, 2011

HIV (Human Immunodeficiency Virus)

One of the scariest virus around is the RNA virus called HIV! Once thought to have originated from Africa is now found worldwide.

What are the symptoms you would have to look out for?
Well, the progress of this disease can be categorized into 4 stages:
  1. First Phase: Most individuals will have no symptoms, but some might develop a rash, flu, and swollen lymph glands.
  2. Second Phase: Production of anti-HIV rises in blood stream. Although the level of HIV in blood falls, HIV replication continues in lymph nodes. This phase can last anywhere from weeks till more than 13 years.
  3. Third Phase: AIDS related complex refers to many opportunistic infections which affect the patient, like fungal and viral infections such as oral and genital herpes.
  4. Fourth Phase: Development of secondary cancers. Kaposi's sarcoma and non-Hodgkin's lymphoma are common. By this time, there is total loss of cellular immunity.

Mechanism of HIV Infection:

  1. HIV enters the body through body fluid or blood transfusion.
  2. HIV binds with CD4 receptors on the surface of T helper cell.
  3. Both membranes then fuse while the capsid is enzymatically removed to release viral RNA and reverse transcriptase into the cytoplasm of the helper T cell.
  4. Viral RNA undergoes reverse transcription followed by replication to produce a double-stranded viral DNA with the help of enzyme reverse transcriptase.
  5. Reverse transcriptase catalyses the synthesis of second DNA, which is complementary to the first.
  6. Viral DNA enters the nucleus and is incorporated into host DNA, as a provirus.
  7. Provirus may remain dormant but is replicated each time host cell divides.
  8. Activated provirus causes host cell to synthesize huge amounts of viral protein and viral mRNA which are then assembled into new retroviruses.
  9. New retroviruses bud off from host cell membrane, infecting other helper T cells.
  10. Number of helper T cells will gradually decrease and cause risk of individual contacting other diseases and finally leading to death.

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