HUMAN IMMUNODEFICIENCY VIRUS-1 REVERSE-TRANSCRIPTASE IMMUNODOMINANT CD4+ T-CELL EPITOPES - A PEPTIDE-BASED MULTIPARAMETRIC ASSESSMENT IN THE MOUSE

We previously identified an immunodominant CD4(+) T cell determinant in the carboxy-terminal region of HIV-1 reverse transcriptase (RT(528-543)) The present study aimed at enumerating all the potential sites of HIV-1 RT recognized by T-h cells in the BALB/c (H-2(d)) mouse model. To achieve this we used a panel of 62 overlapping 15-mer synthetic peptides covering the whole RT sequence to assay the following parameters: (i) immunogenicity in naive BALB/c mice injected either with peptides pools or individual peptides; (ii) antigenicity, as detected by their ability to restimulate in vitro T cells from BALB/c mice primed with native RT; (iii) MHC class II (A(d))-binding capacity as measured by the inhibition of the antigen-specific, A(d)-restricted presentation of unfolded apamin (4-Acm) by fixed antigen-presenting cells to A(d)/4-Acm-specific, interleukin-2-producing T hybridoma cells; and (iv) the presence of typical or degenerate consensus A(d)-binding motifs. The results in this study permitted identification of three novel immunodominant RT mouse CD4(+) T cell sites (RT(276-280), RT(375-389) and RT(411-425)) located in regions of limited polymorphism among RT from several HIV isolates. Some of these RT segments were found to be in the vicinity of B cell or H-2K(d)- or HLA-A2-restricted cytotoxic T lymphocyte epitopes. Finally, the approach used in this study was found to be very efficient for enumerating most T cell recognition sites in a complex protein, a result that would have not been achieved by a single parameter-based analysis.