Cloning and Expression in Escherichia coli of a Protective Surface Protein from Type V Group B Streptococci

Abstract

Infection by group B streptococci (GBS) is an important cause of bacterial disease in neonates, pregnant women, and non-pregnant adults. While strains of serotypes Ia, Ib, II, and III have historically been most prevalent among disease cases, type V strains have emerged recently as important strains in the United States and elsewhere (2). Many GBS strains also possess surface protein antigens that share the phenotypic characteristics of a laddering pattern on SDS-PAGE and resistance to trypsin digestion. These include the alpha C protein (4), which is present primarily on strains of serotypes Ia, Ib, and II; protein Rib (6), which is present on many type III strains; and the R proteins (1,3). We report here the cloning and expression in E. coli of the gene encoding a trypsin-resistant laddering protein purified from a type V GBS strain. This protein is cross-reactive with the alpha C protein and with R1 and elicits protective antibody in an animal model. Preliminary nucleotide sequence data indicates significant homology, though not identity, with the alpha C protein gene.