1992 Volume 4 Issue 17 Pages 269-278
Group B Streptococci(GBS) are Gram-positive, encapsulated bacteria that cause disease in humans, especially in newborns. A major virulence determinant for GBS is the capsular polysaccharide that surrounds GBS cells. Four GBS capsular polysaccharide serotypes (Ia, Ib, II and III) are responsible for all but rare cases of GBS disease, with strains containing type III polysaccharide responsible for nearly two-thirds of all GBS infections in neonates. Mothers of infants with GBS disease have low or unmeasurable levels of antibody to the capsular polysaccharide. It is theoretically possible to increase the levels of polysaccharide-specific antibody in humans by vaccination with purified polysaccharide. However, as with many other bacterial polysaccharides, the immunogenicity of GBS polysaccharide in adults is low. Recent efforts have focused on increasing the immunogenicity of type III polysaccharide by coupling native or derivative type III oligosaccharides to tetanus toxoid. Experimental type III polysaccharide- and oligosaccharide-tetanus toxoid conjugate vaccines of different designs have been developed and their immunogenicity tested in laboratory animals. Despite differences in coupling strategies and size of polysaccharide used for conjugation, all GBS type III glycoconjugates were highly immunogenic in animals compared to uncoupled native type III polysaccharide.
