Secretion antigens of Mycobacterium tuberculosis: A comparison between a reference strain and seven wild isolates

Background. This study was carried out with the aim of detecting possible differences between proteins secreted by fresh wild isolates of Mycobacterium tuberculosis and from a reference strain of this microorganism, H37Rv TMCC 102. Materials and Methods. This reference strain of M. tuberculosis has been in our laboratory for over 10 years, where it has been maintained by serial subcultures in PBY and Lowenstein-Jensen media. Patterns of protein secretion and recognition by sera derived from both tuberculosis patients and normal individuals were analyzed by electrophoresis and Western blotting. Results. No major qualitative differences were observed among the several strains studied with respect to protein patterns or recognition of these proteins by test sera. Normal sera were found to react with almost all antigens recognized by tuberculosis sera, but with less intensity. However, a small protein of 14.5 kDa, secreted by both the wild and reference strains of M. tuberculosis, was recognized by 32 of the 40 tuberculous patient sera tested (80%), and was not recognized by any of the 40 serum samples derived from healthy individuals. Conclusions. This small protein seems to be a potentially important antigen for the serological diagnosis of tuberculosis and/or for use in the follow up of patients who receive treatment.