Medication and the HIV life cycle

Ever wondered how HIV medication works? To understand how medication works, you need to understand the HIV life cycle. Unfortunately there’s going to be some biology…

HIV life cycle

Viruses need a host cell so they can replicate.

There are six stages to the replication process, called the HIV life cycle, and different medications work at different stages.

1) Binding: HIV attaches itself to the surface of a CD4 cell (also called T-cells or T-helper cells). Once attached, viral penetration occurs. Medications called fusions and entry inhibitors work to prevent this happening.

2) Reverse transcription: HIV is a retrovirus which means it contains an enzyme called reverse transcriptase. Inside the CD4 cell, HIV releases and uses reverse transcriptase to convert viral RNA into proviral DNA. The name comes from the fact transcription is usually the other way round, from DNA to RNA, so a retrovirus is one that does transcription backwards (retro-). Nucleoside reverse transcriptase inhibitors (NRTIs or ’nukes’), non-nucleoside reverse transcriptase inhibitors (NNRTIs or ‘non-nukes’) and nucleotide reverse transcriptase inhibitors (NtRTIs) work to prevent reverse transcription.

3) Integration: HIV then enters the CD4 cell nucleus. An enzyme called integrase allows HIV DNA to be combined with the cell’s own DNA. Integrase inhibitors work at this stage.

4) Transcription: The two strands of DNA divide and form a new strand of RNA (sometimes called messenger RNA or mRNA) which contains instructions for making new HIV. Research on drugs that work at this stage, called antisense antivirals or transcription inhibitors (TIs), is ongoing.

5) Translation: Messenger RNA carries the instruction to make viral proteins. A corresponding string of proteins is made for each string of RNA that is processed.

6) Viral assembly: The protein building blocks are cut up into smaller smaller proteins by an enzyme called protease. These smaller proteins contain everything that is needed to make a new HIV particle, including enzymes and proteins. Once the proteins are assembled, the new HIV particle buds off from the CD4 host, floats into the blood stream and can infect new cells. Protease inhibitors work at this stage.

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