Genomic, protein and antigenic variability of mycoplasma bovis

Restriction endonuclease analysis (REA) with three enzymes SmaI, PstI, BamHI- was used to identify 13 different genomic groups among 37 Mycoplasma bovis strains. One genomic group was comprised of 14 strains. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) patterns for one strain chosen from each genomic group and an international reference strain PG45 were all similar. Antigenic variability in M. bovis species was investigated by immunoblotting, using serum from a calf that had been naturally infected with M. bovis and three M. bovis-specific monoclonal antibodies — mAbs N₂, I₂ and 5D7. Twenty M. Bovis field strains were tested, comprising one from each genomic group, six from the same genomic group and the reference strain. Antigenic profiles obtained with calf serum differed markedly one from the other, the heterogeneity being equally great among the strains belonging to the same genomic group as those coming from different groups. A stable antigen common to 164 out of 168 strains was detected by mAb N₂, whilst with mAbs I₂ and 5D7, two different membrane antigenic systems were demonstrated that were strikingly variable. These variations in expression occurred not only from one strain to another, but also within the same lineage of clones from a single cell.