Computational analysis for prediction of HLA-DR-promiscuous regions and epitopes of Mycobacterium tuberculosis protein Rv1980c, and their recognition by human T cell lines (39.1)

Abstract

Abstract Rv1980c, a major secreted antigen of Mycobacterium tuberculosis, is absent in many vaccine strains of BCG, and hence could be useful in the diagnosis or as a new vaccine against tuberculosis. However, to have world-wide application, Rv1980c should have HLA-promiscuous recognition by human Th1 cells. The aim of this study was to determine HLA-promiscuous regions/epitopes of Rv1980c using a computational method, and confirm the predictions experimentally. The sequence of Rv1980c protein was analyzed for binding to 51 HLA-DR alleles using PROPRED, a computational method. The prediction results were experimentally verified by testing 20-mer synthetic peptides corresponding to the predicted HLA-DR binding regions/epitopes with T-cell lines established from PPD-positive and HLA-heterogeneous healthy subjects in Th1-cell assays (antigen-induced proliferation and Interferon-gamma secretion). The PROPRED analysis showed that Rv1980c could bind to all 51 HLA-DR alleles with eight HLA-DR binding regions (9 to 35 aa in length), and five regions (aa 20-44, aa 68-102, aa 132-146, aa 164-186 and aa 194-202) being HLA-DR promiscuous. The results of testing synthetic peptides with T cell lines in Th1 cell assays showed that four peptides belonging to four HLA-promiscuous regions (aa 21-40, aa 81-100, aa 171-190 and aa 191-202) were immunodominant and HLA-DR promiscuous. These results show that PROPRED analysis was useful in identifying HLA- promiscuous regions/epitopes of Rv1980c.