[Purified protein derivative antigen purified by using a monoclonal antibody to Mycobacterium tuberculosis]

A component of Mycobacterium tuberculosis H37Rv PPD referred as C3Ag was purified with a column of affinity chromatography to which a monoclonal antibody (TB-15C3) was conjugated. C3Ag was found to have two bands in 56,000 and 66,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Western blot revealed that both fragments were recognized by TB-15C3. By ELISA C3Ag was shown to react with rabbit antisera against M. tuberculosis, M. Kansasii, M. screfulaceum, M. bovis BCG, but not to react substantially with antiserum against M. bovis. Among 82 sera from patients with pulmonary tuberculosis 60% showed positive reactions to C3Ag while for 100 normal control sera it was only 10%. C3Ag elicited a delayed cutaneous reaction in guinea pigs sensitized with heat killed M. tuberculosis, M. bovis and BCG. These results suggest that C3Ag might be an important fragment of H37Rv PPD.