Study of gene homologous antigen, B cell antigen epitope and cross reaction with antibody IgG between two common non-tuberculous Mycobacteria and Mycobacterium tuberculosis

  Objective  To investigate the cross-immune reaction of the protein antigens between two kinds of common non-tuberculous mycobacterium (NTM) and Mycobacterium tuberculosis in China and provide reference for the development of new tuberculosis vaccines by using NTM.

  Methods  The genomic homology between M. intracellular, M. abscess and M. tuberculosis was calculated with the mean nucleic acid consistency calculator, the homologous genes were analyzed with OrthorFinder and the comparison with the B cell epitope encoding gene of M. tuberculosis was made. The inactivated antigen and whole protein antigens of the three kinds of bacteria were prepared respectively, and the white rabbits from New Zealand were immunized by subcutaneous injection. After immunization, indirect enzyme-linked immunosorbent assay (ELISA) was used to detect the serum IgG levels and cross-immunization serum IgG levels of the immunized rabbits.

  Results  There were 2350 and 2740 homologous genes with M. tuberculosis in M. abscess and M. intracellular, among which 479 and 521 homologous genes were rich in B-cell epitopes. The protein antigens of M. tuberculosis, M. intracellular and M. abscess all stimulated the white rabbits to produce high levels of antibody IgG titers, reaching 1∶320000, 1∶160000 and 1∶80000, respectively. Both M. intracellular and M. abscess immunized rabbits sera had cross-reaction with M. tuberculosis protein antigens at high levels, resulting in antibody titers up to 1∶40000 and 1∶80000 respectively.

  Conclusion  There were high level cross-immune reactions between M. intracellular, M. abscess and M. tuberculosis, suggesting that the two kinds of NTM and M. tuberculosis have more common protein antigens, which has a good potential application value in developing new tuberculosis vaccines.