Functional Profile of CD8+ T-Cells in Response to HLA-A*02:01-Restricted Mutated Epitopes Derived from the Gag Protein of Circulating HIV-1 Strains from Medellín, Colombia

Abstract

CD8+ T-cells play a crucial role in the control of HIV replication. HIV-specific CD8+ T-cell responses rapidly expand since the acute phase of the infection, and it has been observed that HIV controllers harbor CD8+ T-cells with potent anti-HIV capacity. The development of CD8+ T-cell-based vaccine against HIV-1 has focused on searching for immunodominant epitopes. However, the strong immune pressure of CD8+ T-cells causes the selection of viral variants with mutations in immunodominant epitopes. Since HIV-1 mutations are selected under the context of a specific HLA-I, the circulation of viral variants with these mutations is highly predictable based on the most prevalent HLA-I within a population. We previously demonstrated the adaptation of circulating strains of HIV-1 to the HLA-A*02 molecule by identifying mutations under positive selection located in GC9 and SL9 epitopes derived from the Gag protein. Also, we used an in silico prediction approach and evaluated whether the mutations found had a higher or lower affinity to the HLA-A*02. Although this strategy allowed predicting the interaction between mutated peptides and HLA-I, the functional response of CD8+ T-cells that these peptides induce is unknown. In the present work, peripheral blood mononuclear cells from 12 HIV-1+ HLA-A*02:01+ individuals were stimulated with the mutated and wild-type peptides derived from the GC9 and SL9 epitopes. The functional profile of CD8+ T-cells was evaluated using flow cytometry, and the frequency of subpopulations was determined according to their number of functions and the polyfunctionality index. The results suggest that the quality of the response (polyfunctionality) could be associated with the binding affinity of the peptide to the HLA molecule, and the functional profile of specific CD8+ T-cells to mutated epitopes in individuals under cART is maintained.

CD8+T-cell response to mutated HLA-B*35-restricted Gag HY9 and HA9 epitopes from HIV-1 variants from Medellin, Colombia

“…Multiple studies have demonstrated the critical role of CD8 + T-cells in controlling HIV-1 replication [ [28] , [29] , [30] ], attributing the control of viremia and slower progression of HIV-1 infection to CD8 + T-cell responses targeting peptides derived from HIV-1 Gag. Previously, we determined the CD8 + T-cell response to Gag peptides restricted to the HLA-A*02 allele and could associate the peptide binding affinity with CD8 + T-cells polyfunctionality [ 22 ]. Importantly, HLA-I allotype restriction is a limitation for developing effective peptide-based vaccines; therefore, identifying immunodominant Gag peptides restricted to the most prevalent HLA-I molecules makes peptide-based vaccines accessible to larger patient cohorts [ 31 , 32 ].…”

“…Notably, the binding affinity of peptides to HLA molecules tends to be associated with higher immune responses [ 22 , 57 ], where amino acid substitutions at critical HIV-1 epitope sites can affect antigenic presentation, reducing the binding affinity and weaken the TCR-peptide-HLA complex interaction [ 58 , 59 ]. Previously, Lund and collaborators reported that peptides with proline in P2 and tyrosine in P9 of the peptide could bind to B7 supertype alleles [ 60 ].…”

“…HIV-1 + individuals possessing at least one allele belonging to the HLA-B*35 subtype were identified. Inclusion and exclusion criteria for this study were established as previously reported [ 22 ]. The Bioethics Committee of the Faculty of Medicine, Universidad de Antioquia, reviewed and approved this study.…”

“…Peptides were provided by Núcleo de Biotecnología Curauma, Pontificia Universidad Católica de Valparaíso, Chile. Peptide synthesis was performed as previously described [ 22 ].…”

“…The polyfunctional profile was defined as the capacity of CD8 + T-cells to produce multiple markers simultaneously [ 23 , 24 ]. The percentage of cells exhibiting from one to six functions was analyzed as previously described using the SPICE v5.35 software [ 22 , 25 ].…”