EXPERIMENTAL VACCINATION AGAINST GROUP-B STREPTOCOCCUS, AN ENCAPSULATED BACTERIUM, WITH HIGHLY PURIFIED PREPARATIONS OF CELL-SURFACE PROTEIN-RIB AND PROTEIN-ALPHA

Encapsulated bacteria cause some of the most common diseases in humans . Although the polysaccharide capsules of these pathogens have attract ed the most attention with regard to vaccine development, recent evide nce suggests that bacterial surface proteins may also be used to confe r protective immunity. We have analyzed this possibility in group B st reptococcus (GBS), an encapsulated bacterium that is the major cause o f invasive bacterial disease in the neonatal period. Previous work has shown that the majority of GBS strains causing invasive infections ex press the Rib protein, and that most strains lacking Rib express a pro tein designated alpha. Here we report that active immunization with hi ghly purified preparations of Rib or alpha protected mice against leth al infection with strains expressing the corresponding protein. Vaccin ation with the Rib protein protected against two strains of capsular t ype III and two strains of type II, and vaccination with the alpha pro tein protected against one strain of type II and one strain of type Ib . The mice vaccinated with Rib or alpha shelved a good immunoglobulin G response to the immunogen. These data suggest that a vaccine against GBS disease may be based on cell surface proteins and support the not ion that proteins may be used for immunization against encapsulated ba cteria.