Bovine TB: Research project summary
Project SE3206: Sequencing and analysis of the genome of Mycobacterium bovis
Project duration: 5 years 3 months
The aim of this project was to determine the complete genome sequence of Mycobacterium bovis (M. bovis) AF2122/97, a GB strain isolated in 1997 from a diseased cow in Cornwall and to generate sequence data from the M. bovis BCG vaccine strain, the only currently available vaccine against tuberculosis in man or animals. This project is now completed and was undertaken by the VLA, the Sanger Institute and the Institut Pasteur. As a result of this project all the genes, proteins, enzymes and antigens present in M. bovis have been identified rapidly in a highly cost-effective manner. The genome sequence of M. bovis will therefore underpin all future Defra TB research in the development of vaccines and improved diagnostic tests, in the understanding of the molecular basis of pathogenesis and in developing improved tools for molecular epidemiology. Comparative analysis with the genome of BCG has identified antigens not present in the vaccine strain but present in the pathogen, hence providing the basis for differential diagnostics and providing clues to approaches that might improve BCG as a vaccine.
The genome sequence of M. bovis AF2122/97 was found to be 4345492 bp in length and was >99.95% identical at the nucleotide level to the genome of M. tuberculosis. However, deletion of genetic information led to a reduced genome size suggesting that M. bovis has evolved from a progenitor of the M. tuberculosis complex as a host-adapted clone. Cell wall components and secreted proteins showed the greatest variation, indicating their potential role in host-bacillus interactions or immune evasion. Furthermore, there were no genes unique to M. bovis, implying that differential gene expression may be the key to the host tropisms of human and bovine bacilli.
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Page last modified:
July 7, 2008