Crossed immunoelectrophoretic analysis of Mycobacterium paratuberculosis.

Antigenic analysis of M. paratuberculosis revealed extensive cross-reactivity with M. avium; however, the number of cross-reactive antigens found was dependent on the strain of M. avium tested. One antigen was shown to be the common antigen while another appeared to be iron-rgulated in its production. A commercial polyclonal antibody to M. paratuberculosis produced a CIE precipitin pattern comparable to that of the antibody produced for the present study. An antigen designated no. 6 was consistently precipitated by sera from cattle infected with M. paratuberculosis. This antigen exhibited complete cross-reaction with M. avium and partial cross-reaction with M. phlei. Among three commercially available complement fixation (CF) antigen preparations widely used for serodiagnosis of Johne's disease, none were shown to contain protein antigens that could be precipitated by M. paratuberculosis antibodies. A commercial antigen for use in an agar gel immunodiffusion test for Johne's disease diagnosis produced 12 precipitins with the M. paratuberculosis antibody, one of which was identical with antigen 6.