Expression of Group B Protective Surface Protein (BPS) by Invasive and Colonizing Isolates of Group B Streptococci

Abstract

Group B protective surface protein (BPS) is expressed on the cell surface of some group B streptococcal (GBS) (Streptococcus agalactiae) strains and adds to the identification by capsular polysaccharide (CPS), and c or R proteins. We investigated the prevalence of BPS among GBS clinical isolates (303 invasive, 4122 colonizing) collected over 11 years in four American cities. Hot HCl cell extracts were tested by immunoprecipitation in agarose with rabbit antisera to BPS; the alpha (α) and beta (β) components of c protein; R1, R3, and R4 species of R protein; and CPS serotypes Ia-VIII. BPS was found in 155 isolates (seven invasive, 148 colonizing). Of these, 87 were Ia, 37 II, 20 V; none were III. BPS was expressed usually with another protein: a species of R by 87 or a component of c by 39. The predominant CPS/protein profiles with BPS were Ia/R1,BPS and II/c(α + β),BPS. Thus, along with CPS serotype and other surface proteins, BPS can be a valuable marker for precise strain characterization of unique GBS clinical isolates with complex surface protein profiles.

The Streptococcus agalactiae R3 surface protein is encoded by sar5

“…Whether the sar5D-encoded protein may be less efficient in host adhesion, due to the loss of two MucBP domains, remains PLOS ONE to be investigated. BPS was previously detected in a similar portion of invasive and colonizing isolates [37], suggesting the presence of the protein alone does not increase GBS' ability to invade/cause disease, for instance by enhancing host adhesion.…”

The Streptococcus agalactiae R3 surface protein is encoded by sar5

“…Immunoprecipitation-bands that were considered evidence of R3 by Erdogan et al in 2002 (13), may in fact have been bands representing Alp4. Similarly, a study reporting 155 (of 4425 total) colonizing and invasive GBS strains expressing BPS found no overlap between R3-and BPS-expression (34).…”

“…in 2002 (13), may in fact have been bands representing Alp4. Similarly, a study reporting 155 (of 4425 total) colonizing and invasive GBS strains expressing BPS found no overlap between R3- and BPS-expression (34). The presumed R3-specific antibody used in that study was also prepared by adsorbing antisera made by immunizing a rabbit with GBS strain NCTC 9828.…”

“…Existing data suggest that the prevalence of sar5 in GBS strains differs between geographical regions. In Norway and the United States, the prevalence has been reported to lie in the range 2.3-8.1 % in invasive GBS strains (18, 27, 34). In a study from the United States, 3.6 % of more than 4000 colonizing GBS strains carried R3/BPS (34), while in Zimbabwe it amounted to near 30 % in healthy pregnant carriers (6).…”

“…In Norway and the United States, the prevalence has been reported to lie in the range 2.3-8.1 % in invasive GBS strains (18, 27, 34). In a study from the United States, 3.6 % of more than 4000 colonizing GBS strains carried R3/BPS (34), while in Zimbabwe it amounted to near 30 % in healthy pregnant carriers (6). Thus, as a strain variable marker, the R3/BPS protein has proved its potential in serotyping, as a serosubtype marker.…”