STUDY ON THE SURFACE ANTIGENS AND GENOTYPES OF GROUP E STREPTOCOCCI

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Monoclonal antibodies(MAbs II-T, IV21 and V16) to surface antigen of group E streptococci (GES) were prepared by fusing myeloma cells with spleen cells of mice immunized with whole cells of GES.One of them, MAb II-T, reacted in an enzyme immunoassay (EIA) with whole cells of serotypes II and V strains, and in a gel diffusion test with autoclaved-saline extracts of both serotypes. MAb IV21 reacted specifically with a serotype IV strain. On the other hand, MAb V16 reacted with almost all strains of GES and serotype e strains of S.mutans. The crude antigen was extracted from whole cell of GES by autoclaving. The extract was purified by DEAE-Sephadex A-25, followed by the treatment with Proteinase K, and further by chromatography with a Sephadex G-200 column. The purified antigen for MAb II-T was a polysaccharide (PS) composed of 98.6% carbohydrate and 1.4% protein with no detectable phosphorus. That for MAb V16 was also found to consist of 92.4% carbohydrate and 7.6% protein. The antigen for MAb IV21 is now being purified. Furthermore, DNA was extracted from 6 serotypes strains (II, IV, V, VI, VII, and VIII) and 3 clinical isolates of GES.The GC contents(%) of these DNAs were determined to be 36 to 38%, indicating that there is no clear difference in the values among 6 serotypes. In DNA-DNA hybridization experiments using radiolabelled DNA of serotype II strain as a probe, the DNA of only serotype V strain showed 100% homology to the probe while others were 56 to 76% homologous. The ribo-typing of GES in now in progress.