A Streptococcus agalactiae R protein analysed by polyclonal and monoclonal antibodies

Abstract

Bevanger, L., Kvam. A. I. & Mdand, J. A. A Streptococcus agulactiue R protein analysed by polyclonal and monoclonal antibodies. APMIS 103: 731-736, 1995. Unexpected cross-reactivity between two Streptococcus uguluctiue (GBS) isolates formed the basis for purification of a GBS protein called the Ra antigen, and raising of murine monoclonal antibody (MAb) against Ra. The Ra protein was resistant to trypsin digestion, susceptible to pepsin digestion, formed a ladder-like pattern of lines with a periodicity of -8 kD on immunoblotting, was surfacelocalized in GBS strains, and was variably expressed by GBS. These characteristics provided evidence that the Ra antigen belonged to the R proteins of GBS. By testing of reference GBS isolates and antiserum, including an anti-R4 protein serum, cross-reactivity was recorded consistent with the assumption that Ra is a R4 protein. The Ra/R4 protein also showed cross-reactivity with a previously described GBS protein called protein Rib (J. Exp. Med. 177: 1593-1603, 1993. Several characteristics of the RdR4 protein were similar to those of the GBS protein ca, but the two proteins showed no cross-reactivity. The anti-RdR4 MAb has proved useful in serosubtype determination of GBS of known serotype and should be a valuable tool for studying the immunobiological function of antibodies targetting the surface-localized Ra/R4 protein.Streptococcus agalactiae (group B streptococci; GBS) are important pathogens in humans, particularly in neonatal infections. The bacteria harbour capsular carbohydrate antigens which for decades have formed the basis for serotype determination, and have also been considered important virulence factors of GBS and targets for protective antibodies (1, 2). In addition to the serotype antigen, the majority of GBS isolates harbour surface-localized protein antigens which show strain variability. Of these, the ca and cp antigens of the c proteins and the R protein antigens have attracted considerable interest (7, 11, 12). These proteins provide the basis

Molecular Profiles of Group B Streptococcal Surface Protein Antigen Genes: Relationship to Molecular Serotypes

“…Numerous methods have been used to identify GBS surface antigens by using monoclonal (24) or polyclonal antibodies (3) or genes by hybridization with probes (27), PCR (19,20,21), and/or sequencing (16,20). PCR-based methods are attractive because of their high discriminatory power and reproducibility (20).…”

Cervical Secretions in Pregnant Women Colonized Rectally with Group B Streptococci have High Levels of Antibodies to Serotype III Polysaccharide Capsular Antigen and Protein R

“…In addition, the presence of c proteins (c a antigen and c b antigen) and R protein was determined by indirect FAT [14,15].…”

“…Protein R 4 was prepared from GBS strain 65604 as described previously [15,17]. Briefly, the bacteria were cultured overnight in Todd Hewitt broth, and extracted with HCl (0.2 N HCl, 56ЊC, 2 h).…”

“…Protein in the supernatant was precipitated three times with 10% trichloracetic acid (TCA), and dissolved in the least possible amount of PBS before extensive dialysis. Protein R 4 was affinity purified from this crude extract using CNBr-activated Sepharose containing bound murine IgG monoclonal antibody (MoAb) R 4 , which was developed as described previously [15].…”

Survey of Immunological Features of the Alpha-Like Proteins of Streptococcus agalactiae

“…Anti-Rib antibodies showed protective activity in experimental infections with GBS strains expressing Rib and with infection that was caused by a Streptococcus strain which was Rib negative but expressed a crossreacting surface protein (26,38). Immunological testing and sequence analysis have shown that Rib is identical to the historical R4 protein (39,40). When antibodies were elicited by immunization with intact Rib with multiple C-terminal repeats, the repeat region was immunodominant and the N terminus was nonimmunodominant.…”