The lysis of Group A type 1 streptococcal cell walls by phage-associated lysin has been described. In the preparation of lysin, a new semisynthetic non-protein media to support growth of the propagating strain of Group C streptococci was employed. Following lysis of the cell walls, the resulting digest was partially purified by ion-exchange chromatography and ammonium sulfate precipitation. In addition to M protein, the resulting preparation (called lysin M protein) contained the group-specific carbohydrate and the T protein—but did not contain antigens, detectable by precipitin tests, which cross-reacted with absorbed heterologous group or type antisera. Capillary precipitin reactions between the lysin M protein and type-specific antiserum did not occur in the presence of high ionic strength buffers; these buffers did not similarly affect precipitin reactions of acid M protein.

Type 1 lysin M protein is shown to be a good antigen. A total of 1.5 mg. injected intradermally in saline produced bactericidal antibody in eight of nine rabbits; when injected in adjuvant in one rabbit, protective serum antibodies developed. Streptococci grown in sera from seven of nine rabbits immunized with lysin M protein demonstrated significantly longer chains than when grown in normal rabbit serum. Antibody as demonstrated by each of these three tests was shown to be type-specific.

No local or systemic toxicity was noted following intradermal injection in rabbits of lysin M protein.

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