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
Lipopolysaccharides (LPSs) were prepared by phenol‐water extraction of the gonococcal strain 8551 and the group B meningococcal strain 44/76, digested with pronase, and purified by ultracentrifugation and Sepharose CL‐6B fractionation in the presence of 1.5 per cent sodium deoxycholate. On SDS‐PAGE with 10 per cent acrylamide the purified 5I‐labelled LPSs migrated as single, low‐molecular‐weight components. The LPSs were coupled to CNBr‐activated Sepharose 4B for affinity purification of antibodies to the common antigenic factor 1 and the sero‐type factor 5 of LPS 8551, and antibodies to LPS 44/76. The antibodies eluted showed ELISA activity against wells coated with LPS or whole cells of the bacteria, the antibody activity being inhibited by LPS. SDS‐PAGE of whole cells of the strain 8551 and immunoblotting with the anti‐factor 1 or ‐factor 5 antibodies resulted in single, broad bands corresponding to the low‐molecular‐weight LPS subunits.
Production of the common enterobacterial antigen (CA) by strains of Yersinia enterocolitica (Y. e.) serotypes 3 and 9 (Winblad), by strains of 5 different Y. e. serogroups (Wauters) and various other bacteria was examined. Antibody against CA was raised by immunization of rabbits with E. coli O 14. Extract prepared from S. typhimurium was used for the sensitization of sheep erythrocytes with CA. Absorption and haemagglutination inhibition experiments showed that CA could be detected in heat extracts from all Y.e. strains examined, and in that from Yersinia pseudotuberculosis. CA was not detected in extracts from Pasteurella multocida, Francisella tularensis, Brucella abortus, Acinetobacter calcoaceticus or Pseudomonas aeruginosa. Anti‐CA antibodies could not be demonstrated in serum from rabbits immunized with Y.e. bacteria, but were demonstrated in serum from rabbits immunized with a CA‐containing fraction of the Y.e. extract. The possibility of participation of anti‐CA antibody in indirect haemagglutination tests for detection of antibody to Y.e. O antigens is emphasized.
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