Identification and HLA restriction of naturally derived Th1-cell epitopes from the secreted Mycobacterium tuberculosis antigen 85B recognized by antigen-specific human CD4 super(+) T-cell lines

• Published in: Infection and immunity Vol. 68; no. 7; pp. 3933 - 3940
• Main Authors: Mustafa, A S, Shaban, F A, Abal, A T, Al-Attiyah, R, Wiker, H G, Lundin, KEA, Oftung, F, Huygen, K
• Format: Journal Article
• Language: English
• Published: 01-07-2000
• Subjects: antigen 85B; CD4 antigen; histocompatibility antigen HLA; Mycobacterium tuberculosis
• ISSN: 0019-9567
• DOI: 10.1128/IAI.68.7.3933-3940.2000

Antigen 85B (Ag85B/MPT59) is a major secreted protein from Mycobacterium tuberculosis which is a promising candidate antigen for inclusion in novel subunit vaccines against tuberculosis (TB). The present study was undertaken to map naturally derived T-cell epitopes from M. tuberculosis Ag85B in relation to major histocompatibility complex (MHC) class II restriction. Antigen-specific CD4 super(+) T-cell lines were established from HLA-typed TB patients and Mycobacterium bovis BCG vaccinees by stimulation of peripheral blood mononuclear cells with purified Ag85B in vitro. The established T-cell lines were then tested for proliferation and gamma interferon (IFN- gamma ) secretion in response to 31 overlapping synthetic peptides (18-mers) covering the entire sequence of the mature protein. The results showed that the epitopes recognized by T-cell lines from TB patients were scattered throughout the Ag85B sequence whereas the epitopes recognized by T-cell lines from BCG vaccinees were located toward the N-terminal part of the antigen. The T-cell epitopes represented by peptides p2 (amino acids [aa] 10 to 27), p3 (aa 19 to 36), and p11 (aa 91 to 108) were frequently recognized by antigen-specific T-cell lines from BCG vaccinees in both proliferation and IFN- gamma assays. MHC restriction analysis demonstrated that individual T-cell lines specifically recognized the complete Ag85B either in association with one of the self HLA-DRB1, DRB3, or DRB4 gene products or nonspecifically in a promiscuous manner. At the epitope level, panel studies showed that peptides p2, p3, and p11 were presented to T cells by HLA-DR-matched as well as mismatched allogeneic antigen-presenting cells, thus representing promiscuous epitopes. The identification of naturally derived peptide epitopes from the M. tuberculosis Ag85B presented to Th1 cells in the context of multiple HLA-DR molecules strongly supports the relevance of this antigen to subunit vaccine design.