Heteroclitic peptides enhance human immunodeficiency virus-specific CD8 T cell responses

The inability of human immunodeficiency virus (HIV)-specific CD8⁺ T cells to durably control HIV replication due to HIV escape mutations and CD8⁺ T cell dysfunction is a key factor in disease progression. A few HIV-infected individuals termed elite controllers (EC) maintain polyfunctional HIV-specific CD8⁺ T cells, minimal HIV replication and normal CD4⁺ T lymphocyte numbers. Thus, therapeutic intervention to sustain or restore CD8⁺ T cell responses similar to those persisting in EC could relieve terminal dependence on antiretrovirals. Vaccination with HIV peptides is one approach to achieve this and our objective in this study was to determine whether certain HIV peptide variants display antigenic superiority over the reference peptides normally included in vaccines. Eight peptide sets were generated, each with a reference peptide and six variants harboring conservative or semi-conservative amino acid substitutions at positions predicted to affect T cell receptor interactions without affecting human class I histocompatibililty-linked antigen (HLA) binding. Recognition across peptide sets was tested with >80 HIV-infected individuals bearing the appropriate HLA alleles. While reference peptides were often the most antigenic, cross-reactivity with variants was common and in many cases, peptide variants were superior at stimulating interferon-γ production or selectively enhanced interleukin-2 production. Although such heteroclitic activity was not generalized for all individuals bearing the HLA class I allele involved, these data suggest that heteroclitic peptide variants could improve the efficacy of therapeutic peptide vaccines in HIV infection.