Drugs used to treat HIV infection were developed based on the life cycle of HIV. These drugs prevent HIV entry into its target cells or inhibit the three enzymes (reverse transcriptase, integrase, and protease) that the virus uses to replicate.
1. HIV first attaches to and penetrates its target cell. The overall classes of drugs that act against HIV at this stage are called entry inhibitors, and they included attachment inhibitors, post-attachment inhibitors, and fusion inhibitors.
2. HIV releases RNA, the genetic code of the virus, into the cell. For the virus to replicate, its RNA must be converted to DNA. Drugs called reverse transcriptase inhibitors can prevent HIV reverse transcriptase from converting HIV RNA into DNA.
3. The viral DNA enters the cell’s nucleus.
4. With the help of an enzyme called integrase (also produced by HIV), the viral DNA becomes integrated with the cell’s DNA. At this stage, drugs called integrase inhibitors can prevent HIV DNA from being integrated into human DNA.
5. The DNA of the infected cell now produces viral RNA as well as proteins that are needed to assemble a new HIV.
6. A new virus is assembled from RNA and short pieces of protein.
7. The virus pushes (buds) through the membrane of the cell, wrapping itself in a fragment of the cell membrane and pinching off from the infected cell.
7.5 and 8. To be able to infect other cells, the budded virus must mature. Another HIV enzyme (HIV protease) is crucial to this maturation. At this stage, drugs called protease inhibitors can prevent the maturation of the HIV virus.