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Fig. 1. Common pattern of HIV infection in a typical untreated patient indicates a
three-phase evolution. The two lines represent CD4 T cell count and viral load respec-
tively. (Image: Bryan Christie, July 1998 Scientific American)
- Duringafewweeks(varyingfromtwotosixweeks),atransientanddramatic
jump of plasma virion level is present with a marked decrease of immune cell
count (CD4 T helper cells), following by a sharp decline.
- In the subsequent chronic phase (varying from one to ten or more years,
on average eight to ten years), the immune system partially eliminates the
HIV virus and the rate of viral production reaches a lower, but relatively
steady, state that varies greatly from patient to patient. Their apparent
good health continues because CD4 T cell levels remain high enough to
preserve defensive responses to other pathogens. But over time, CD4 T cell
concentrations gradually fall.
- An outbreak of the virus (varying from one to two years), together with con-
stitutional symptoms and onslaught by opportunistic diseases, cause death
[2].
1.2
Biological Background of Drug Therapy of HIV Infection
Avaccine would certainly be ideal for preventing infection by HIV and thus for
avoiding AIDS when immunity is severely impaired. The near-term prospects
for a vaccine are poor due to error occurrence during each transcription of HIV.
Therefore, for the immediate future, many scientists are concentrating on im-
proving the therapy.
- Currently, there are fifteen drugs licensed for treatment of individuals in-
fected with HIV. These drugs belong to two classes, one inhibiting the vi-
ral enzyme reverse transcriptase and the other inhibiting the viral protease.
Thesedrugsareusedincombinationtherapytomaximallyinhibitviralrepli-
cation and decrease HIV-RNAto below levels of detection levels (currently
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