PDE6B and tuberculosis: Furthermore, RD1 is absent in all sub-strains of BCG [93,94,95,96] because of its deletion during the attenuation of the parent BCG strain obtained by prolonged sub-culturing of pathogenic M. bovis in an artificial medium [97], and hence the application of RD1-encoded immunodominant antigens in the diagnosis of TB is not expected to have any effect due to BCG vaccination [98,99,100,101].