GENOMIC, PROTEIN HOMOGENEITY AND ANTIGENIC VARIABILITY OF MYCOPLASMA-AGALACTIAE

Eleven strains of Mycoplasma agalactiae differing in pathogenicity, an imal species origin and geographic localisation, showed similar chromo some restriction profiles with four endonucleases, However the interna tional reference strain PG2 showed a unique profile. The protein and a ntigenic variabilities of 31 strains of M. agalactiae were investigate d using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS -PAGE) and immunoblotting performed with naturally infected animal ser a and purified antibodies against the 29 kDa protein. Protein profiles were similar but antigenic profiles could be separated into two main groups according to geographic origin: (i) strains isolated in south-w est France and (ii) strains from north-east France, Some differences a lso occurred from strain to strain within each group. The antigenic pr ofile variability found in immunoblotting, originated in two different phenomena: (i) some epitopes were expressed only in strains of one pr ofile type and (ii) some other epitopes were common to all strains but located on several proteins which differed in number and molecular ma ss from one strain to another. The presence of epitopes which undergo phase variation in the same lineage of clones from a single cell is di scussed.