HLA class I binding regions of HIV-1 proteins.

To identify HIV peptides containing HLA class I binding regions, different studies have been performed. These include the detection of interactions between HIV peptides and purified HLA molecules in solid-phase assays, the measurement of HLA molecule assembly in the presence of peptide added to cell lysates, and the detection of inhibition of CTL-mediated cytolysis by competition between peptides on target cells. To date, the HIV epitopes recognized by anti-HIV CTL are from the Env, Gag, Nef, and Pol proteins and they are identified using synthetic peptides of 12 to 20 amino acids. The search for a correlation between known HIV CTL epitopes and the results of HLA/peptide interaction assays reveals that: (1) most of the peptides that are positive in the assembly assay contain a HLA-A2 peptide motif but the correlation between these positive peptides and the CTL epitopes is not obvious; (2) a high proportion of HIV epitopes are included in the peptides positive in solid-phase binding and in inhibition of cytolysis assays, although these tests do not allow us to predict HLA restriction; (3) the HLA-A2 peptide motif is not systematically included in HLA-A2-restricted CTL epitopes, this observation raising the possibility that other sequences are involved in HLA binding.