Safety and immunogenicity of capsular polysaccharide-tetanus toxoid conjugate vaccines for group B streptococcal types Ia and Ib

About 40% of invasive group B streptococcal (GBS) isolates are capsular pol ysaccharide (CPS) types Ia or Ib, Because infant and maternal GBS infection s may be preventable by maternal vaccination, individual GBS CPS have been coupled to tetanus toroid (TT) to prepare vaccines with enhanced immunogeni city, Immunogenicity in rabbits and protective capacity in mice of a series of type Ia- and Ib-TT conjugates increased with the degree of polysacchari de-to-protein cross-linking. In total, 190 healthy, nonpregnant women aged 18-40 years were randomized in four trials to receive Ia- or Ib-TT conjugat e (dose range, 3.75-63 mu g of CPS component), uncoupled Ia or Ib CPS, or s aline. All vaccines were well-tolerated. CPS-specific IgG serum concentrati ons peaked 4-8 weeks after vaccination and were significantly higher in rec ipients of conjugated than of uncoupled CPS. Immune responses to the conjug ates were dose-dependent and correlated in vitro with opsonophagocytosis, T hese results support inclusion of Ia- and Ib-TT conjugates when formulating a multivalent GBS vaccine.