pstS1 polymorphisms of Mycobacterium tuberculosis strains may reflect ongoing immune evasion.

The mycobacterial antigen PstS1 is a highly immunogenic and immunostimulatory component of the mycobacterial cell membrane and a good candidate for the diagnosis and vaccination against tuberculosis. Here we selected 180 clinical isolates of Mycobacterium tuberculosis complex (MTBC) in China and 11 different Bacille Calmette Guerin (BCG) strains, amplified the gene of the PstS1 antigen and compared the sequences with those of four other Mycobacterium bovis and BCG strains from the NCBI genome website. Some of the mutations, especially 2 frameshift mutations, occurred in the PstS1antigen, which may have resulted in the protein function alteration and ongoing immune evasion. A unique single nucleotide polymorphism of the M. bovis and BCG strains was found in this antigen and may be useful for differentiating M. bovis and BCG strains from M. tuberculosis strains.