“…ESAT-6 and CFP-10 form a heterodimer in the cytoplasm which is recognized by the secretion system through a signal sequence present in the CFP-10 C-terminus (Renshaw et al 2005). Both M. microti and M. bovis BCG contain a deletion in the esx-1 region which is one of the main causes of their attenuation suggesting that these two proteins have an important role in pathogenicity (Brodin et al 2006;Gordon et al 1999). To reinforce this hypothesis, it was recently demonstrated that a strongly attenuated strain of M. tuberculosis, H37Ra, is unable to secrete ESAT-6 because of the down-regulation of the genes rv3614c-rv3616c (espA).…”