Search

The mutational escape of HIV-1 from established CTL responses is becoming evident. However, it is not yet clear whether antigenic variations of HIV-1 may have an additional effect on the differential antiviral effectiveness of HIV-specific CTLs. Herein, we characterized HIV-specific CTL responses toward Pol, Env, and Nef optimal epitopes presented by HLA-B*35 during a chronic phase of HIV-1 infection. We found CTL escape variants within Pol and Nef epitopes that affected recognition by TCRs, although there was no mutation within the Env epitope. An analysis of peptide-HLA tetrameric complexes revealed that CD8 T cells exclusively specific for the Nef variant were generated following domination by the variant viruses. The variant-specific cells were capable of killing target cells and producing antiviral cytokines but showed impaired Ag-specific proliferation ex vivo, whereas wild-type specific cells had potent activities. Moreover, clonotypic CD8 T cells specific for the Pol variant showed diminished proliferation, whereas Env-specific ones had no functional heterogeneity. Taken together, our data indicate that antigenic variations that abolished TCR recognition not only resulted in escape from established CTL responses but also eventually generated another subset of variant-specific CTLs having decreased antiviral activity, causing an additional negative effect on antiviral immune responses during a chronic HIV infection.

Human CTL clones discriminating serologically closely related HLA-Bw52, B51, and B35, which belong to HLA-B5 crossreacting group (CREG), were established from peripheral blood lymphocytes by repeated in vitro stimulations. Five HLA-Bw52-specific CTL clones from an individual with HLA-B5 CREG antigens and four CTL clones from another individual with HLA-B51 were generated. The specificity of these CTL clones was ascertained by their lysis of EBV-transformed B cells with HLA-Bw52, but not those with HLA-B51 or B35, and Bw52-transfected Hmy2CIR cells but not HLA-B51 or B35 transfectants. Conversely HLA-B51-specific clones were generated from the HLA-B5 CREG-negative individual, as well as another individual with HLA-Bw52. Their specificity was determined in a similar fashion. Since HLA-B51 differed from HLA-Bw52 only by two amino acid substitutions on the alpha helical region of the alpha 1 domain, these results demonstrated that allospecific CTLs can be produced and discriminate the epitopes formed by the subtle difference in the structure of these HLA class I molecules. Furthermore, three HLA-B35-specific CTL clones were generated from the HLA-B5 CREG-negative individual that discriminated HLA-B35 from HLA-Bw52 and B51. Taken together these results demonstrated that human CTL clones could definitively discriminate the three serologically related HLA-B5 CREG specificities.