Question

6. A medical student asks you to draw a picture of the HIV virion and a CD4 cell, and to explain the mechanism of intracellular infection and the role of reverse transcriptase. What would you show on the drawing and explain about the process?

Answer 1

HIV HIV HIV virus particle HIV viral assembly and budding Mature HIV virion HIV viral entry into CD4+ cells and reverse transcription of viral RNA into DNA by HIV reverse transcriptase and further integration into host DNA and viral replication into new viral mRNA

Human immunodeficiency virus or HIV belongs to a class of viruses called retroviruses. They attack human immune cells and cause AIDS. They can't replicate on their own and therefore uses the CD4+ cells to make copies of themselves. The HIV virus is a spherical virus that is surrounded by viral envelope on which glycoproteins, gp120 and gp40 are present as spikes. These glycoproteins bind with the receptors on CD4+ cells and helps in entry of the viral genetic material and other enzymes like reverse transcriptase inside CD4+ cells. Since HIV is a retrovirus, Its genetic material is single stranded RNA. After entry inside the cell, HIV RNA is reverse transcribed by the enzyme reverse transcriptase (from HIV) into double-stranded viral DNA which is then transported into the nucleus. Inside the nucleus, viral DNA is integrated into the host DNA by HIV integrase where it may remain dormant in the latent stage of infection. When these CD4+ cells become active, for example in case of an infection, the viral DNA will starts replicating. HIV uses host cell machinery to transcribe viral DNA into mRNA, which is then translated into viral proteins. The viral proteins then start to assemble as new virus particles at the host's plasma membrane. The viral glycoproteins then associates with the plasma membrane and the assembling virus starts to bud from the membrane. The viral RNA is then enclosed by the capsid. After the virus assembly is complete, the budded virus is cleaved by the viral protease. Then mature virus particles spread and infect other CD4+ cells.