Journal of virology 2017 09 06() pii 10.1128/JVI.00544-17
Immune control of human immunodeficiency virus type 1 (HIV) infection is typically associated with effective Gag-specific CD8+ T-cell responses. We here focus on HLA-B*14, that protects against HIV disease progression, but the immunodominant HLA-B*14-restricted anti-HIV response is Env-specific (ERYLKDQQL, ‘HLA-B*14-EL9’). A subdominant HLA-B*14-restricted response targets Gag (DRYFKTLRA, ‘HLA-B*14-DA9’). Using HLA-B*14/peptide-saporin conjugated tetramers, we show that HLA-B*14-EL9 is substantially more potent at inhibiting viral replication than HLA-B*14-DA9. HLA-B*14-EL9 also has significantly higher functional avidity (p<0.0001) and drives stronger selection pressure on the virus than HLA-B*14-DA9. However, these differences were HLA-B*14 subtype-specific, applying only to HLA-B*14:02 and not HLA-B*14:01. Furthermore, the HLA-B*14-associated protection against HIV disease progression is significantly greater for HLA-B*14:02 than for HLA-B*14:01, consistent with the superior antiviral efficacy of the HLA-B*14-EL9 response. Thus, although Gag-specific CD8+ T-cell responses may usually have greater anti-HIV efficacy, factors independent of protein specificity, including functional avidity of individual responses, are also critically important to immune control of HIV.IMPORTANCE In HIV infection, although CTL play a potentially critical role in eradication of viral reservoirs, the features that constitute an effective response remain poorly defined. We focus on HLA-B*14, unique among HLA associated with control of HIV in that the dominant CTL response is Env-specific, not Gag. We demonstrate that Env-specific HLA-B*14-restricted activity is substantially more efficacious than the subdominant HLA-B*14-restricted Gag response. Env immunodominance over Gag, and strong Env-mediated selection pressure on HIV, are only observed in subjects expressing HLA-B*14:02, and not HLA-B*14:01. This reflects increased functional avidity of Env response over Gag, substantially more marked for HLA-B*14:02. Finally, we show that HLA-B*14:02 is significantly more strongly associated with viraemic control than HLA-B*14:01. These findings indicate that, although Gag-specific CTL may usually have greater anti-HIV efficacy than Env responses, factors independent of protein specificity, including functional avidity, may carry greater weight in mediating effective control of HIV.