Abstract
Four Mycoplasma arthritidis strains, two virulent (158p10p9 and 14124p10) and two avirulent (PG6 and H606), were examined for differences in their antigenic compositions. Rabbit antisera prepared against each strain were compared for their reactivities against both homologous and heterologous strains by enzyme-linked immunosorbent assay and metabolism inhibition assay. These tests confirmed a close serologic relationship among the four strains. Only by cross-absorbing each antiserum with intact cells from both homologous and heterologous strains could serologic differences be detected. Interestingly, antigenic variability was minimal among those antigens involved in the metabolism inhibition reaction, suggesting that they may be highly conserved within this species. No differences in protein composition could be detected by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. However, slight variation was apparent on two-dimensional gels, and antigens possessing strain-specific epitopes were detected by two-dimensional immunoblotting experiments performed with cross-absorbed antisera. The enzyme-linked immunosorbent assay, two-dimensional electrophoresis, and immunoblotting experiments showed that the two virulent strains were closely related to each other, while the avirulent strains were more distantly related to each other and to the other two strains. The relationship of M. arthritidis serologic diversity to virulence remains unclear: however, this study has demonstrated that it may be possible to subdivide M. arthritidis into serogroups on the basis of cross-absorption patterns and to identify those antigens bearing strain-specific epitopes by immunoblotting with cross-absorbed antisera.