Polypeptide and antigenic variability among strains of Mycoplasma ovipneumoniae demonstrated by SDS-PAGE and immunoblotting.

Comparison of the polypeptide patterns of 22 isolates of M. ovipneumoniae by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) showed a marked degree of heterogeneity with only limited groupings identifiable. Of the 50 major polypeptides identified in one strain (956/2), 35 were shown to be antigenic using immunoblotting with a homologous polyclonal serum. Radioimmune precipitation of 125I-surface-labelled proteins and phase partition using Triton X-114 detergent indicated that these were membrane associated. Cross-reactivity between the isolates was examined by immunoblotting using one polyclonal serum and four monoclonal antibodies (MAbs), all raised against strain 956/2. The polyclonal serum revealed considerable antigenic heterogeneity, but at least nine major antigens were conserved across all isolates. Two MAbs cross-reacted with all 22 strains, but the other two MAbs allowed some differentiation of the strains. One (MO/3) divided the isolates into groups of 16 and 6 based on the presence of absence of a 26-kDa antigen. All strains isolated from sheep with pulmonary adenomatosis fell into the smaller group and did not possess the 26-kDa antigen.