Mycobacterium tuberculosis 38kDa antigen and its encoding gene-experience in diagnostic applications

Our experience has revealed that the detection of 38 kDa antigen or antibody to the antigen in various fluids is useful in diagnosis of various mainfestations of tuberculosis. The PCR developed for 340bp sequence of its encoding gene also shows a high degree of sensitivity and specificity. Thus the 38 kDa antigen/antibody combination or the PCR are ideal for development of kits for diagnosis. These immunoassays to be successful, isolation of the 38 kDa antigen in large quantities is essential. Using recombinant DNA technology and expression inE. coli this has been achieved. However, such recombinant antigen does not have the same immunological properties as the native antigen and hence not suitable in immunodiagnosis. To fully realise the potential of the MoAb defined antigens such as the 38 kDa antigen, 19 kDa antigen and others it is essential to devise alternative vector-host systems that help in glycosylation, do not accumulate as inclusion bodies and can be isolated with less damage.