IMMUNODOMINANT ANTIGENS OF STREPTOCOCCUS-EQUISIMILIS SHARED BY OTHER BETA-HEMOLYTIC STREPTOCOCCI

Three immunodominant antigens of Streptococcus equisimilis (Lancefield group C) with approximate mel, wts of 46, 66 and 105 kDa were recogni sed by human serum IgG and IgA immunoblotting. These antigens were ide ntified consistently by various human sera but immunoblots with IgA (h eavy chain) and secretory IgA (J chain) from human respiratory secreti ons gave more variable results. Antigens with similar migration rates were demonstrated in S. pyogenes, large colony human biotype group G s treptococci, and streptococci of groups C and G from the ''S. anginosu s-milleri group''. Polyclonal antibody which was eluted from immunoblo t substrates that contained the S. equisimilis 66-kDa antigen reacted with the 60-kDa antigen of S. pyogenes. Both polyclonal and monoclonal anti-vimentin antibodies identified the 46-kDa and 66-kDa antigens of S. equisimilis. The homology of these antigens among beta-haemolytic streptococci has the potential to complicate both a strategy for the u tilisation of immunoblotting for diagnostic purposes and the understan ding of how such antigens may be involved in the pathogenesis of post- infectious sequelae.