Problem 15

Background and context

Human immunodeficiency virus (HIV) is a retrovirus that attacks the CD4 T lymphocytes and uses its machinery to replicate within the host thereby making the most susceptible to infection.

The HIV life cycle occurs in 7 stages:

• Attachment: HIV binds to receptors on the CD4 cell surface.
• Penetration: The virus fuses with the CD4 cell membrane and enters the CD4 cell.
• Uncoating: HIV releases its contents such as HIV RNA, reverse transcriptase, integrase, and other viral proteins into the cell.
• Reverse transcription: The HIV RNA is converted to HIV DNA by reverse transcriptase. The HIV DNA enters the nucleus and integrates with the host DNA with the help of the integrase enzyme.
• Replication: once integrated into the host genome, HIV uses the CD4 cell machinery to make more viral proteins. 
• Assembly: New HIV RNA and proteins move to the cell surface and assemble as immature HIV virus particles.
• Release: The immature HIV buds off the host cell. This new immature HIV releases proteases that break down the long protein chains to form the mature HIV virus.