A 24-year-old male with a homozygous CCR5 mutation is found to be immune to HIV infection. The patient’s CCR5 mutation interferes with the function of which viral protein?
1.Reverse transcriptase
2.gp120
3.gp41
4.p24
5.pp17
exp:
The viral protein gp120 mediates HIV attachment to host macrophages through the CCR5 and CD4 complex.
The viral protein gp120 is a product of the env gene, which codes a polyprotein product that is subsequently glycosylated to form gp160. The gp160 is cleaved within host cell endoplasmic reticulum to form gp120 and gp41. gp120 binds the CXCR4 or CCR5 co-receptor and CD4 complex on T cells and the CCR5 and CD4 complex in macrophages. Homozygous CCR5 mutation confers HIV immunity, while heterozygous CCR5 mutation leads to a slower disease course in infected individuals.
Illustration A diagrams attachment of HIV to a CD4 T-helper cell. The gp120 viral protein attaches to CD4. The gp120 variable loop then attaches to either CCR5 or CXCR4, and HIV enters the cell.