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 (RT528-543). The present study aimed at enumerating all the potential sites of HIV-1 RT recognized by Th cells in the BALB/c (H-2d) 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 (Ad)-binding capacity as measured by the inhibition of the antigen-specific, Ad-restricted presentation of unfolded apamin (4-Acm) by fixed antigen-presenting cells to Ad/4-Acm-specific, interleukin-2-producing T hybridoma cells; and (iv) the presence of typical or degenerate consensus Ad-binding motifs. The results in this study permitted identification of three novel immunodominant RT mouse CD4+ T cell sites (RT276-290, RT375-389 and RT411-425) 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-2Kk- 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.