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Britannica Sources used in this answer

How does HIV enter CD4 helper T cells before reverse transcription begins?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Diagram illustrating the process of retrovirus infection and reverse transcription, showing a retrovirus entering a host cell, releasing viral RNA, reverse transcriptase converting RNA to DNA, integration into the host genome, transcription of new viral RNA, assembly of new virions, and budding from the cell.
Reverse transcriptase After a retrovirus infects a cell, an enzyme known as reverse transcriptase converts viral RNA into proviral DNA in the cytoplasm. Proviral DNA then enters the nucleus, where it is incorporated into the host cell's DNA.

Before reverse transcriptase begins the process of reverse transcription, HIV enters a helper T cell through a multi-step fusion process:1

  • Attachment: The viral envelope protein gp120 binds to the CD4 receptor on the surface of the helper T cell.1
  • Coreceptor Interaction: This binding exposes a region of gp120 that interacts with specific chemokine receptors, such as CCR5 or CXCR4, which act as coreceptors.1
  • Fusion: This interaction triggers a conformational change in the viral protein gp41, causing it to insert into the host cell membrane. A subsequent change in gp41 pulls the viral envelope and the host cell membrane together, allowing them to fuse and release the viral genetic information into the cell.1

Only after this successful entry does the virus utilize reverse transcriptase to convert its RNA into DNA.1