An enzyme (protein) that's part of the human immunodeficiency virus reads the sequence of viral RNA nucleic acids (yellow in graphic) that have entered the host cell and transcribes the sequence into a complementary DNA sequence (shown in blue). That enzyme is called "reverse transcriptase" . Without reverse transcriptase, the viral genome couldn't become incorporated into the host cell, and couldn't reproduce.
Reverse transcriptase sometimes makes mistakes reading the RNA sequence. The result is that not all viruses produced in a single infected cell are alike. Instead, they end up with a variety of subtle molecular differences in their surface coat and enzymes. Vaccines, which induce the production of antibodies that recognize and binding to very specific viral surface molecules, are an unlikely player in fighting HIV, because throughout infection, HIV surface molecules are continually changing.
The first major class of drugs found useful in slowing HIV infections are collectively called "reverse transcriptase inhibitors" (shown in red). These include AZT, 3TC, d4T, ddc, and ddl that act by blocking the recoding of viral RNA into DNA. The chameleon-like nature of HIV, however, limits their continued effectiveness.
2. REVERSE TRANSCRIPTION
From viral RNA to DNA
3. INTEGRATION, TRANSCRIPTION
a. Viral DNA joins host DNA
b. Making multiple viral RNAs