Genome Sequences Highlight Variations in Strains Found in TB Vaccines

For a paper in BMC Genomics, a team led by investigators at the Tehran University of Medical Sciences tallies single-nucleotide polymorphisms and small insertion and deletion variants in bacteria found in two versions of the Bacillus Calmette-Guerin (BCG) vaccine, developed to prevent tuberculosis. When they compared whole-genome sequences from the BCG Danish 1331 and the BCG Pasteur 1173P2 vaccine strains to one another and to reference genome sequences from the Mycobacterium tuberculosis strain H37Rv, an M. bovis strain known as AF2122/97, and a M. tuberculosis variant bovis Pasteur 1173P2 BCG strain, the researchers unearthed two previously undetected variants and a nearly 14,600 base pair duplication in the BCG Danish 1331 vaccine strain. The authors also got a look at human T cell antigen epitopes that correspond to each of the vaccine strains. "This study revealed that the present experimentally confirmed human T cell epitopes are highly conserved in both BCG strains and do not reflect any ongoing [evolution]," they conclude. "However, further studies are required to find the association of genetic variations with vaccine variable efficacy and determine the most effective vaccine strain."