Immunoaffinity chromatographic isolation of a high molecular weight seroreactive protein from Mycobacterium leprae cell sonicate.

The purpose of this study was to isolate Mycobacterium leprae antigen(s) by immunoaffinity chromatography using immunoglobulins from leprosy patients and from rabbit anti-M. leprae hyperimmune serum coupled to CNBr-Sepharose 4B. A high molecular weight (M(r)) M. leprae protein (MLP) with a subunit M(r) of 22,000 was isolated. MLP was recognized by monoclonal antibody MMPII1G4 which is known to react with MMPII, a 22 kDa protein of M. leprae. The N-terminal sequence of the 22 kDa subunit (Met-gln-gly-asp-pro-asp-val-leu-arg-leu-leu-asn-glu-gln-leu-thr) was identical to MMPII and to antigen D (bacterioferritin) of M. paratuberculosis. It showed 44% homology with N-terminal end of E. coli bacterioferritin. In ELISA, MLP showed 100% and 60% positivity with leprosy and TB sera respectively as compared to normal healthy sera. The role of bacterioferritin in M. leprae and the importance of MLP as an immunogen has been discussed.