Mouse‐protective Effect of Rabbit Anti‐r‐protein Antibodies Against Group B Streptococci Type Ii Carrying R‐protein

Abstract

Linden, V. Mouse-protective effect of rabbit anti-R-protein antibodies against group B streptococci type I1 carrying R-protein. Lack of effect on type 111 carrying R-protein. Acta path. microbiol. immunol.scand. Sect. B, 9 / : 145-151, 1983. R-proteins was isolated by affinity chromatography from an alkaline extract of group B streptococci, type 111. The identity of the protein was demonstrated by pepsin-and trypsin-treatment and in double diffusion-in-gel with antisera from other laboratories. A monospecific rabbit antiserum against the Rprotein was studied in mouse-protection tests. using three type II strains with R-protein and three without, and six type 111 strains, of which four carried R-protein. The serum protected animals from infection by type I1 strains carrying R-protein, but not against any of the other strains. The capacity of anti-R-protein serum to opsonize type I1 strains carrying R-protein was also demonstrated in phagocytosis experiments with mouse peritoneal macrophages. Studies with radio-labelled protein A and anti-R-protein antibodies showed that R-protein was localized on the surface of both type 11 and type 111 group B streptococci. Taken together, the results suggest that type 11 group B streptococci should be divided into two subtypes, 11. R + and 11. R-.

The Occurrence of R‐protein Among Isolates of Group B Streptococci From Human Sources

“…We were not able to demonstrate any mouseprotective effect of anti-R-protein antibodies against experimental type 111 infections. On the other hand, such antibodies do protect mice from infection by type I1 strains carrying R-protein ( 13) which might contribute to the low frequency of type I1 strains in neonatal meningitis also reflected in the present report, provided that anti-R antibodies are also protective in human beings. R-protein is generally considered to be ))unstable( (1 5); the meaning of this characterization, as well as the scientific background to such a statement, is not clear.…”

“…B and C. For many years it was believed that R-protein was of no importance for the virulence of group B streptococci ( I ) , a view based on the observation that anti-R antibodies are incapable of protecting mice against infection by group A streptococci type 28 (1 2). Recently, we demonstrated that anti-R antibodies are in fact capable of protecting mice from infection by type I1 group B streptococci carrying this antigen, but not against type I1 without R-protein or against type 111, irrespective of the presence of R-protein (13). These studies indicated that R-protein might be of importance for the virulence of type I1 group B streptococci.…”