Identification and HLA restriction of naturally derived Th1-cell epitopes from the secreted Mycobacterium tuberculosis antigen 85B recognized by antigen-specific human CD4(+) T-cell lines.
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(+) 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.
Mustafa
A S
AS
Department of Microbiology, Faculty of Medicine, Kuwait University, Kuwait. abusalim@hsc.kuniv.edu.kw
Shaban
F A
FA
Abal
A T
AT
Al-Attiyah
R
R
Wiker
H G
HG
Lundin
K E
KE
Oftung
F
F
Huygen
K
K
D000217:Acyltransferases; D000595:Amino Acid Sequence; D017951:Antigen Presentation; D000942:Antigens, Bacterial / Q000235:genetics; D001500:BCG Vaccine / Q000276:immunology; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D002460:Cell Line; D000939:Epitopes / Q000235:genetics; D006680:HLA Antigens; D006801:Humans; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000276:immunology*; D017386:Sequence Homology, Amino Acid; D018417:Th1 Cells / Q000276:immunology*; D014397:Tuberculosis, Pulmonary / Q000276:immunology
D000942:Antigens, Bacterial; D001500:BCG Vaccine; D001426:Bacterial Proteins; D000939:Epitopes; D006680:HLA Antigens; D000217:Acyltransferases; C121433:antigen 85B, Mycobacterium tuberculosis