Comparison of Mycoplasma synoviae isolates by immunoblotting

SDS-polyacrylamide gel electrophoresis (PAGE) and immunoblot profiles using antisera from M. synoviae F10-2AS-inoculated chickens detected heterogeneity among 10 M. synoviae isolates. This variation was primarily seen in immunoblots as a difference in the molecular size of immunoreactive proteins below 50 kDa and corresponded to an area of variability seen in SDS-PAGE. No two isolates had the same immunoblot profile below 50 kDa. Hyperimmune antiserum to a M. synoviae F10-2AS protein of 41 kDa (p41) reacted with protein(s) ranging from 41 to 48 kDa in nine of 10 isolates and strongly with one of 87 kDa in one isolate. The immunoreactivity of antiserum from inoculated chickens and the hyperimmune antiserum to p41 varied from intense to weak with the 10 M. synoviae isolates. All of the highly immunogenic proteins of M. synoviae F10-2AS, including p41, partitioned into the Triton X-114 detergent phase, indicating that they are amphiphilic in nature and integral membrane proteins. The data suggest that M. synoviae is capable of varying the molecular size of a highly immunogenic integral membrane protein.