Strain‐variable Streptococcus agalactiae (group B streptococci; GBS) proteins exposed at the bacterial cell surface are important markers in GBS serotyping. These proteins include the c proteins cα and cβ and the R proteins R1 through R4, of which R1 and R4 have been studied most extensively. This study presents the characteristics of a protein which was expressed by a capsular antigen type V GBS strain shown by means of polyclonal and monoclonal antibody testing. Examination of a number of reference and prototype strains by fluorescent antibody testing and Western blotting provided evidence that the serotype V‐derived protein was the R3 protein of GBS, previously defined on the basis of immunoprecipitation assays. The putative R3 protein formed ladder‐like banding patterns on Western blotting with polypeptides in the 30 kDa to ≥ 140 kDa range, was destroyed by pepsin digestion, and partially degraded by trypsin digestion. The protein was expressed by 10 (6.5%) of 153 clinical GBS strains tested, the expression being restricted to isolates of the capsular antigen types II, III, and V. Some isolates expressed both the cβ and the R3 protein. Expression in combination with cα or R4 protein synthesis was not detected. Inclusion of the anti‐R3 monoclonal antibody among antibody reagents for GBS serotyping will enhance the discriminatory power of this typing method.

Summary. The distribution of capsular polysaccharide antigen (CHO) types, surface-exposed c proteins a (c") and p (cp> and an R-protein antigen was examined in 334 group B streptococci (GBS) isolates from three groups of patients hospitalised in England and Wales or Norway. The isolates were from 108 carriers, 67 cases of neonatal infection and 154 cases of adult infection. Each group contained all CHO types (Ia, Ib, 11,111, IV, V and NT); type I11 strains predominated except in the adult infected group. Strains within each CHO type could be further subdivided by the protein markers into five subtypes by a combined typing system. The proportion of type Ib and type I11 strains in the neonatal infection cases and of type Ib strains in the adult infection cases significantly outnumbered isolates of these serotypes among the carrier strains. Twenty-nine different serovariants were identified; 24, 13 and 23 serovariants among the carrier, neonatal infection and adult infection isolates, respectively. Certain CHO antigen-protein associations were identified, notably those between Ia/ca, Ib/c@ and III/R. The proportion of invasive isolates that expressed protein was not higher than in the carrier isolates. All CHO-type Ib isolates contained a c protein, but 7 % of the Ib isolates did not contain any of these proteins. These findings indicate that this combined typing approach may be useful in examining epidemiological problems associated with GBS.

We have studied the relationships between genital or rectal carriage of group B streptococci (GBS) with the levels of systemic and mucosal antibodies to GBS in 200 women at about week 17 of pregnancy. Secretions from the uterine cervix were collected with absorbent cylindrical wicks for quantification of antibody levels with whole cell enzyme-linked immunosorbent assay. GBS were cultured from the cervix (with or without concomitant rectal colonization) of 13.5%, from the rectum (with or without concomitant cervical colonization) of 12%, and from both culture sites of 8.5% of the women. Serotypes Ia, II, and III were predominant. Compared with culture-negative women, the group of women colonized rectally had markedly elevated levels of both immunoglobulin A (IgA) and IgG antibodies to GBS in cervical secretions and also had a moderate but significant elevation of IgA antibodies in sera. Women colonized only in the cervix had increases of specific IgA and IgG antibodies in cervical secretions, but their serum antibody levels were not elevated. In cervical secretions, the increase in antibody levels in the groups of colonized women was most pronounced for the IgG isotype, indicating a mucosal immune response involving IgG as well as IgA. A close correlation was found among the levels of antibodies to each of the three GBS serotypes tested. Evidence for such cross-reacting antibodies to different serotypes of GBS, as well as to group A streptococci, was also obtained from absorption experiments. Altogether, our results show that undiluted secretions for antibody determination can be easily collected from the uterine cervix with absorbent wicks and demonstrate that colonization of GBS in the rectum and the uterine cervix may induce a systemic as well as a pronounced local immune response in the female genital tract. The findings may have implications for the development of a mucosal vaccine against GBS disease.

Streptococcus agalactiae (group B streptococci; GBS) are serotyped on the basis of the capsular polysaccharide antigens and subtyped on the basis of the strain-variable and surface-localised c proteins ca, cp, and R proteins. This study compared cp protein detection and the polymerase chain reaction (PCR) for p gene detection, by examining 50 clinical GBS strains. The cp protein was detected by antibody-based immunofluorescence in a GBS whole-cell assay and Western blotting by probing with the anti-cp antibody or human IgA. Absorption experiments were performed to test for surfaceanchoring of cp; and bacterial supernates were examined to test for cp production.Primers for the PCR target regions resulted in a 620-bp product that included p gene-

Most isolates of group B streptococci (GBS) express an alpha-like protein (Alp), C␣ (encoded by bca), Alp1 (also called epsilon; alp1), Alp2 (alp2), Alp3 (alp3), Alp4 (alp4), or R4/Rib (rib). These proteins are chimeras with a mosaic structure and with antigenic determinants with variable immunological crossreactivities between the Alps, including Alp1 and C␣ cross-reactivity. This study focused on antigenic domains of Alp1, studied by using rabbit antisera in immunofluorescence, Western blotting, and enzymelinked immunosorbent assay (ELISA)-based tests and whole cells of GBS or trypsin-extracted and partially purified antigens from the strains A909 (serotype Ia/C␣, C␤) and 335 (Ia/Alp1). Alp1 and C␣ shared an antigenic determinant, Alp1/C␣ common, not harbored by other Alps, probably located in the Alp1 and C␣ repeat units, as these units are nearly identical in genomic sequence. An antigenic Alp1 determinant was Alp1 specific and was most likely located in the N-terminal unit of Alp1 in which an Alp1-specific primer site for PCR is also located. In addition, Alp1 possessed a domain with low immunogenicity which cross-reacted immunologically with Alp2 and Alp3, with unknown location in Alp1. Alp1 was partially degraded by trypsin during antigen extraction but with the antigenic domains preserved. The results indicate that C␣ and Alp1 are immunologically related in the same manner that R4 (Rib) and Alp3 are related. The domain called Alp1 specific should be important in GBS serotyping as a surface-anchored serosubtype marker. The Alp1/C␣ common determinant may be of prime interest as an immunogenic domain in a GBS vaccine.Group B streptococci (GBS) can be classified into 10 serotypes based on the capsular polysaccharides (CPS), serotypes Ia, Ib, and II through IX. In addition, a number of surfaceanchored and strain-variable protein antigens enable serosubtyping of GBS, resulting in a large number of GBS serovariants. For example, 25 different serovariants were identified in a GBS strain collection from Zimbabwe (19). The surfacelocalized proteins include C␤ encoded by bac, C␣ (bca), the alpha-like proteins (Alps) Alp1 (alp1; also called epsilon), Alp2 (alp2), Alp3 (alp3), Alp4 (alp4), R4/Rib (rib), the GBS protective protein R5 (sar5) (8), the R3 protein (11, 32), and a recently described novel protein called Z (20). Neither R3 nor Z has as yet been sequenced. The Alps are chimeras with a mosaic structure composed of an N terminus with 220 to 230 amino acids (aa), including the signal sequence (6), an area with a variable number of identical, tandem repeats, each containing ϳ80 aa, and a C terminus (12,15,22,31). The structural arrangement provides for protein-specific immune reactions in some cases and variable immunological crossreactivities between the proteins. Epitopes of the Alps induce antibodies which protect against GBS infection in experimental models, including cross-protection by cross-reacting antibodies (1,12,15,27,33).The C␣-encoding gene bca was the first Alp gene sequenced (GenBank accession no....