|MadSci Network: Virology|
The Human Immunodeficiency virus is a virus which mutates a lot. This
high mutation rate has two causes. First of all, it is an RNA virus which
must be translated into DNA. In this step about 1 in 2000 bases is wrongly
translated. In infected persons it is also around for many years (about 10)
before it really results in AIDS. During this time the virus is not 'asleep'
(latent) but fighting with the immune system. It is copied many times during
the 10 years and as you can imagine, may different 'subclasses' arise in this
one infected person.
These mutations may result in resistance to the various drugs that are around. To become resistant to the new protease inhibitors (PI's), only 10 mutations in specific places are needed. Resistance to AZT and the like occurs even faster, and the virus can be resistant in about 3 months (!).
The difference between HIV-1 and HIV-2 is quite big. HIV-2 is more related to the Simian immunodeficiency virus (SIV) of monkeys then to HIV-1.
HIV-1 is subdivided in several different classes. There are several ways to differentiate between these classes, by their reaction with antibodies or by their RNA-sequence. However, the differences within HIV-1 are smaller then the differences between HIV-1 and HIV-2.
A link: description of the retrovirus family
Hope this answers your question,
Try the links in the MadSci Library for more information on Virology.