Recombinant Proteins of Mycobacterium tuberculosis ? The Potential Serodiagnostic Candidates from Deleted Regions

Tuberculosis is one of the leading causes of death which haunted the mankind since antiquity and still is a global epidemic growing with increased incidence, especially in India. Bacillus Calmette-Guerin (BCG) is the only available vaccine for tuberculosis currently in use. But this vaccine shows a varied success rate (0% to 80%) in preventing tuberculosis. Gene deletion was an important part of the attenuation process that led to the BCG vaccine. The genome of M. tuberculosis comprises 4,411,529 bp and contains around 4,000 genes. Comparative genomics has identified several genomic regions in Mycobacterium tuberculosis and Mycobacterium bovis that are deleted in all tested BCG strains. The Region of Deletion 1 region is the best characterized of the deleted regions. It has been long speculated and recently been confirmed that the 9455 bp region of deletion 1 of Mycobacterium tuberculosis contributes to bacterial virulence. The identification of RD1 and the subsequent demonstration of its role in the virulence of Mycobacterium tuberculosis have fueled the speculation that this region could be exploited for the development of a vaccine for TB. Immunological tests based on detecting the presence of antibodies in the sera of active TB patients against various antigens of M. tuberculosis are useful for sero-diagnosis of TB and offer simple, rapid and cost effective methods most suitable for poor and developing countries. Several serodiagnostic assays use an optimized set of recombinant antigens from RD1 region of Mycobacterium tuberculosis. This may help to develop a novel anti-tuberculosis vaccine with higher efficiency than BCG by genetic engineering.