HIV - AN OVERVIEW :
HIV/AIDS is among the greatest health crisis ever faced by humanity. Already this pandemic has killed 30 million people. Today, 38 million people are living with HIV. Each year, 3 million are dying of HIV/AIDS. More than 6 million people are living with HIV in the countries of the South-East Asia Region. India ranks as the country with the second largest number (5.1 million) of such people in the world and is next only to South Africa.
Envelope Proteins (env):
- Outer env protein-gp 120
- Transmembrane protein: gp 41-HIV 1, gp 36-HIV
- Precursor protein-gp 160
Polymerase Proteins (pol):
- Reverse transcriptase-p66
- Endonuclease/integrase-p31
Core Proteins:
- Major structural proteins-p24 & p18
- Internal structural proteins-p17
- Precursor protein-p55
LABORATORY TESTS FOR DIAGNOSIS OF HIV INFECTION :
Antibody response in HIV infection:
Basis of serology is that infected persons develop detectable antibodies to protein components of virus within 3 wks - 6 months after exposure to virus. Sequence of events following entry of HIV helps optimal usage of various tests during different stages of the infection.
- Abs appear by 2 - 8 weeks.
- Window period - period between entry of HIV & appearance of detectable ab levels
- Most of the presently available kits detect only after 3 weeks to 12 weeks
- Anti gag abs (p24 & p55) appear first
- Anti env & pol abs - persist throughout infection - Abs are IgA, IgM & IgG
- Tests for IgA & IgM have Inconsistent response and have low sensitivity