OBJECTIVETo investigate the polymorphisms of the coding gene and the human T cell epitopes of antigen GlnA1, Mpt70, LppX, GroES and LpqH on Mycobacterium tuberculosis complex (MTBC) strains in thirteen provinces of China.

METHODSA total of 173 clinical MTBC isolates from thirteen provinces were selected to test the gene sequences of the five antigens, using PCR and DNA sequencing methods. Sequences were compared and sliced by BioEdit, and the variations of the human and nonhuman T cell epitopes were analyzed. The rates on synonymous mutation (dS), non-synonymous mutation (dN) and dN/dS values were calculated by Mega 6.0 software.

RESULTSAmong the 173 strains, there were two non-synonymous mutations in the non-epitope region of glnA1, one non-synonymous mutations in epitope domain of mpt70, one non-synonymous mutation and one synonymous mutation in the epitope domain of lpqH; while groES showed no mutation. lppX had five non-synonymous mutations and one synonymous mutation in the epitope domain. Nine strains presented higher polymorphism at the same gene locus of position 152 in lppX. And seven of the fifteen epitopes contained in lppX were altered and the dN/dS value of this gene was 0.19.

CONCLUSIONSData from the human T cell epitope domains of MTBC antigens Mpt70, LppX and LpqH contained epitope diversity, indicated that these antigens may have involved in diversifying the selection to evade the host immunity. GlnA1 had the polymorphism in epitope domain, which might have little influence on the immuno-response. While GroES seemed relatively conservative, it could play an important role on identification, diagnosis and the development of potential Mycobacterium tuberculosis vaccine.