Vaccination with highly purified cell surface proteins confers protection against experimental group B streptococcal infection.

Abstract

Group B Streptococcus (GBS) is the major cause of invasive bacterial infections among neonates. Although the polysaccharide capsule of GBS has attracted the most attention with regard to vaccine development, there is evidence that bacterial surface proteins may also confer protective immunity.3 Previous work has shown that ≈90% of all GBS strains causing invasive infections express either protein Rib or protein α on the cell surface.3 The Rib and α proteins are structurally related and define a novel family of streptococcal proteins, which in vitro show little or no cross-reactivity immunologically.2, 3, 4 To analyze whether these proteins can be used for vaccination against GBS disease, we developed a method for isolation of these proteins in a highly purified form, free of polysaccharides. Here we summarize data from our experiments which demonstrate that active immunization with each of these purified proteins protects mice from lethal infection with GBS strains expressing the corresponding protein.2