HIV stuff Flashcards
what is the definition of AIDS
less than 200CD4+ T cell count
what are the first three steps in HIV infection
1: attachment - this sees the gp120 protein bind to the CD4 receptor on the T cell
2: fusion - binding of gp120 to CD4 induces a conformational change which allows gp120 to also bind CCR5. with that bound the gp41 can bind to the T cell membrane and the virus fuses
3: uncoating of the viral capsid
what are steps 4-6 in the HIV infection cycle
4: reverse transcription of the RNA genome into DNA form by reverse transcriptase
5: nuclear import as the DNA genome forms a pre-implantation complex which then moves into the nucleus of the cell
6: integration of the viral DNA into the DNA of the T Cell
what are steps 7-13 of HIV replication
7: Transcription
8: nuclear export
9: translation
10: assembly at the cell membrane
11: budding
12: release
13: maturation - protease activity cleaves the gag and gag pol into the proteins of the virus
why can we have latent HIV infection
the HIV taken up into these cells will form memory T cell responses, so the T cell is not active in DNA transcription. hence the virus is not being made in this cell as its non active. so it lays dormant
why do the CD4+ T cells die
the CD8 T cells kill the infected CD4+ cells as they contain the viral antigen
why is HIV so hard to cure
the Reverse transcriptase for the virus has high error rate each time it replicates, and there is no DNA proof reading mechanism in the virus. so the virus can have its antigen that was once being detected, mutate. making the CD4 infected cells no longer detectable and hence the virus can proliferate.
how do entry inhibitors work
maraviroc - this is a CCR5 inhibitor that prevents gp120 binding to it.
Fusion inhibitor - enfuvirtide this inhibits gp41 binding and fusion of the virus
what are the two types of reverse transcriptase inhibitors
nucleoside analogues: these compete with the natural DNA substrates and get incorporated into the expanding DNA chain. but they lack a 3’OH group so they cause premature chain termination.
Non-nucleosides - non-competitive inhibitors that bind to a hydrophobic pocket away from the active site, thereby preventing the active site of reverse transcriptase working as the active site has changed shape.
integrase inhibitors do what
inhibit the action of integrase enzyme. so no viral DNA be getting into that host DNA
what things do we use to test for HIV
viral RNA which is present for whole lifespan
p24 antigen which is transient
antibody which spikes then stays around
