Identification and Characterization of a Mycoplasma synoviae 55,000-Molecular-Weight Antigen Associated with Hemagglutination

Abstract

Serological studies have shown that some antigenic determinants are conserved among several pathogenic Mycoplasma species, including Mycoplasma pneumoniae, M. genitalium, and M. gallisepticum. M. synoviae, an avian pathogen that shares certain morphological and biological features with the above-mentioned mycoplasmas, was examined by the protein immunoblot procedure for its reactivity with hyperimmune rabbit antiserum specific for the major (190,000 molecular-weight [MW]) adhesion P1 protein of M. pneumoniae. A single polypeptide of M. synoviae of approximately 55,000 MW was recognized by the anti-P1 antiserum. The 55,000-MW antigen was electroeluted following electrophoretic separation of M. synoviae polypeptides, and the eluted protein was used for immunization of mice for the production of monoclonal antibodies (MAbs) and polyclonal antiserum. Immunoelectron microscopy with MAbs and gold-conjugated secondary antibodies showed that the 55,000-MW antigen was located at the cell surface and was more densely clustered around the bleb-like protuberance of the cell. Immuno-affinity-purified 55,000-MW antigen, as well as the antibodies produced against it, blocked the hemagglutination by M. synoviae.