Mycoplasma gallisepticum is a poultry pathogen that causes respiratory disease and loss of egg production worldwide. A live attenuated vaccine, ts-11, has been used for control of M. gallisepticum in several countries. The rapid serum agglutination test is usually used as an indicator of flock response to vaccination; however, in some flocks, the detected response may be weak or absent.
With the use of specific monoclonal antibodies against M. gallisepticum strain S6 pMGA in immunoaffinity purification, the major membrane antigen of ts-11 was purified. An indirect enzyme-linked immunosorbent assay (ELISA) was developed with the purified antigen, and its potential for detection of antibodies induced after ts-11 vaccination was compared with an indirect ELISA with M. gallisepticum strain S6 pMGA. In the presence of high levels of ts-11–induced antibodies, both antigens detected similar numbers of positive sera. However, when lower levels of antibodies were present, ts-11 pMGA showed a higher sensitivity than S6 pMGA. Further examination of ts-11 pMGA with Mycoplasma synoviae–infected chicken sera revealed that ts-11 pMGA is specific for M. gallisepticum antibodies. With a panel of sera from ts-11–vaccinated or non-ts-11–vaccinated field chickens, the ts-11 pMGA ELISA was found to be more sensitive than the commercial rapid serum agglutination test in detecting antibodies to ts-11 vaccine.
The results from this study suggest that the major membrane antigen of M. gallisepticum may have slightly different antigenic profiles in different strains, thereby necessitating the use of autologous antigens in serodiagnostic assays to increase sensitivity of the tests for mycoplasma antibodies. Thus, the low level of antibody response after ts-11 vaccination is, at least partially, due to the low ability of the current diagnostic antigens to bind ts-11 antibodies.