Cloning and expression of immunoreactive antigens from Mycobacterium tuberculosis

Four immunoreactive proteins, B.4, B.6, B.10, and B.M, with molecular weigh ts ranging from 16,000 to 58,000, were observed from immunoblots of Mycobac terium tuberculosis total lysates screened with sera from individuals with active tuberculosis. These proteins were identified from microsequence anal yses, and genes of proteins with the highest homology were PCR amplified an d cloned into the pQE30 vector for expression studies. In addition, a 37.5- kDa protein, designated C17, was identified from a phage expression library of M. tuberculosis genomic DNA. Preliminary immunoblot assays indicated th at these five resultant recombinant proteins could detect antibodies in ind ividuals with active pulmonary and extrapulmonary tuberculosis. The overall ranges of sensitivities, specificities, positive predictive values, and ne gative predictive values for the recombinant antigens were 20 to 58, 88 to 100, 69 to 100, and 56 to 71%, respectively. The B.6 antigen showed prefere ntial reactivity to antibodies in pulmonary compared to nonpulmonary tuberc ulosis serum specimens. All of these recombinant antigens demonstrated pote ntial for serodiagnosis of tuberculosis.