MOUSE‐PROTECTIVE EFFECT OF RABBIT ANTI‐R‐PROTEIN ANTIBODIES AGAINST GROUP B STREPTOCOCCI TYPE II CARRYING R‐PROTEIN

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Abstract
R-proteins were isolated by affinity chromatography from an alkaline extract of group B streptococci type III. The identity of the protein was demonstrated by pepsin- and trypsin-treatment and in double diffusion with antisera. A monospecific rabbit antiserum against the R-protein was studied in mouse-protection tests, using 3 type II strains with R-proteins and 3 without, and 6 type III strains, of which 4 carried R-proteins. The serum protected animals from infection by type II strains carrying R-protein, but not against any of the other strains. The capacity of anti-R-protein serum to opsonize type II strains carrying R-protein was also demonstrated in phagocytosis experiments with mouse peritoneal macrophages. Studies with radio-labeled protein A and anti-R-protein antibodies showed that R-protein was localized on the surface of type II and type III group B streptococci. Apparently, type II group B streptococci should be divided into 2 subtypes, II, R+ and II, R-.