High Frequency of HIV Mutations Associated with HLA-C Suggests Enhanced HLA-C Restricted CTL Selective Pressure Associated with an AIDS-Protective Polymorphism

Delayed HIV-1 disease progression is associated with a single nucleotide polymorphism upstream of the HLA-C gene that correlates with differential expression of the HLA-C Ag. This polymorphism was recently shown to be a marker for a protective variant in the 3'UTR of HLA-C that disrupts a microRNA binding site, resulting in enhanced HLA-C expression at the cell surface. Whether individuals with "high" HLA-C expression show a stronger HLA-C restricted immune response exerting better viral control than that of their counterparts has not been established. We hypothesized that the magnitude of the HLA-C restricted immune pressure on HIV would be greater in subjects with highly expressed HLA-C alleles. Using a cohort derived from a unique narrow source epidemic in China, we identified mutations in HIV proviral DNA exclusively associated with HLA-C, which were used as markers for the intensity of the immune pressure exerted on the virus. We found an increased frequency of mutations in individuals with highly expressed HLA-C alleles, which also correlated with IFN-gamma production by HLA-C restricted CD8(+) T cells. These findings show that immune pressure on HIV is stronger in subjects with the protective genotype and highlight the potential role of HLA-C restricted responses in HIV control. This is, to our knowledge, the first in vivo evidence supporting the protective role of HLA-C restricted responses in nonwhites during HIV infection. The Journal of Immunology, 2012, 188: 4663-4670.