Membrane-associated and cytosolic species-specific antigens of Mycoplasma bovis recognized by monoclonal antibodies.

Mycoplasma bovis is a causative agent of bovine mastitis, arthritis, and pneumonia. Six monoclonal antibodies (MAbs) against M. bovis were prepared and used to characterize specific antigens of the mycoplasma. Reactivity of the MAbs to six M. bovis strains was tested by IFA, ELISA, and immunoblotting. The specificity of these MAbs was tested by the same methods against 8 other species of bovine mycoplasmas and 1 mycoplasma species of sheep and goats (Mycoplasma agalactiae) that is highly cross-reactive with M. bovis. Three of the MAbs were used on Western blots of trypsin-treated whole organisms to determine if the antigens were exposed on the surface of M. bovis By isotyping, MAbs were identified as kappa chain IgG1 (3 MAbs), and IgM (3MAbs). The MAbs reacted with all six M. bovis strains in IFA, ELISA, and Western blots. Four of the antigens recognized were highly specific for M. bovis in ELISA, and 3 were cross-reactive with M. agalactiae or other bovine mycoplasmas in Western blots. One MAb reacted with multiple bands with all M. bovis strains, indicating recognition of a size-variant antigen. The size-variant antigen and one of the M. bovis-specific antigens were recognized as surface proteins. A large M. bovis-specific antigen was a conserved cytosolic protein. The M. bovis antigens discovered may be used for specific detection of the organism or measurement of antibody responses, particularly if used in tests with nondenatured alkali-treated antigen, such as ELISA.