title: The putative R1 protein of Streptococcus agalactiae as serotype marker and target of protective antibodies.
abstract: The streptococcal R1 protein was studied by means of anti-R1 antibodies prepared by appropriate cross-absorption of rabbit antiserum raised against the group B streptococcal (GBS) strain ATCC 12403 (D136C), serotype III/R1. The protein was a ladder-forming antigen according to banding patterns in immunoblotting, similar to several other GBS proteins, and was susceptible to digestion by both pepsin and trypsin. Antibody-based testing revealed that 10% of Norwegian GBS isolates expressed the R1 protein, most frequently capsular antigen type V strains (72%) and less frequently type III strains (3%). None of 132 GBS strains from Zimbabwe, including 39 type V strains, expressed the R1 protein. R1-specific rabbit antibodies showed protective activity in mice challenged with a GBS type V/R1 strain. The results show that the R1 protein is an important GBS serotype marker in strains from certain geographical areas, notably for the subtyping of capsular type V strains, and that this protein is a target of protective antibodies.
authors.affiliation: Department of Medical Microbiology, University of Zimbabwe Medical School, Harare, Zimbabwe.
authors.forename: S R
authors.initials: SR
authors.lastname: Moyo
authors.forename: J A
authors.initials: JA
authors.lastname: Maeland
authors.forename: R V
authors.initials: RV
authors.lastname: Lyng
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology*; D001426:Bacterial Proteins / Q000276:immunology*; D015415:Biomarkers; D003429:Cross Reactions; D051379:Mice; D011817:Rabbits; D012703:Serotyping; D013292:Streptococcus agalactiae / Q000145:classification / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D015415:Biomarkers