Vaccines to prevent neonatal GBS infection.

Group B Streptococcus (GBS) remains the leading bacterial cause of neonatal sepsis and meningitis in the United States. Although antibiotic prophylaxis has decreased the infection rate, the best long-term solution lies in the development of effective vaccines. The GBS capsular polysaccharide (CPS) is a major target of antibody-mediated immunity. While antibody to CPS is protective, uncoupled CPS is variably immunogenic in humans, a finding that led to the development of GBS CPS-protein conjugate vaccines. GBS CPS-protein conjugate vaccines of all clinically important serotypes have been produced and tested in animals. Mice and baboons immunized with CPS conjugates transplacentally transferred functionally active GBS-specific IgG to their offspring. Phase 1 and phase 2 clinical trials have shown that GBS conjugate vaccines are safe, well-tolerated and immunogenic in healthy adults. Moreover, human antibodies elicited by the conjugate vaccines are functionally active both in vitro and in animal models of invasive GBS disease.