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Ashworth, Helen (Communicable Disease Center, Atlanta, Ga.), and William K. Harrell. New method of preparing immunizing antigens for the production of anti-M sera against certain serotypes of group A streptococci. J. Bacteriol. 89:141-145. 1965.-Antisera against types 4, 29, 41, and 46 streptococci have been prepared by use of a vaccine killed by adjusting the pH to 11.7 and heating for 1 hr at 56 C. Heating at the high pH destroyed the antigenic material responsible for the major reciprocal crosses present in cells of types 4, 29, and 46 without affecting the M protein. Antisera prepared with the "alkaline-treated" vaccine did not contain the major reciprocal crosses. Antibodies against the M protein were shown to be present by the bactericidal test, failure to react in the precipitin test with acid extracts of homologous trypsinized cells, and retention of the precipitin reaction after absorption with homologous trypsinized cells. The antisera did not react with the "B" antigen of the provisional type B 3264. Type 11 antisera prepared with alkaline-treated vaccine did not contain antibodies against the M protein. The usefulness of this type vaccine, particularly for the preparation of type 4 antiserum, is discussed, as well as its limitations.

New Method of Preparing Immunizing Antigens for the Production of Anti-M Sera Against Certain Serotypes of Group A Streptococci