Immune response of healthy women to 2 different group B streptococcal type V capsular polysaccharide-protein conjugate vaccines

Background. Infections caused by group B streptococcal (GBS) type V are increasingly common. Capsular polysaccharide (CPS)-protein conjugate GBS vaccines are immunogenic in healthy adults, but type V vaccines have not previously been tested. Methods. Thirty-five healthy, nonpregnant women were randomized to receive an intramuscular dose of GBS type V CPS-tetanus toxoid (TT) vaccine (n = 15), GBS type V CPS-cross-reactive material (CRM197) conjugate vaccine (n = 15), or placebo (n = 5) (double-masked design). Levels of serum antibodies to type V CPS were measured by ELISA, and functional activity was measured by opsonophagocytosis. Results. The vaccines were well tolerated. Significant increases in type V CPS-specific immunoglobulin G (IgG) were elicited by both vaccines, peaking at 4-8 weeks and persisting for 26 weeks. Four-fold or greater increases in type V CPS-specific IgG concentrations were noted in postimmunization serum samples obtained from 93% of subjects in each vaccine group. These concentrations persisted in greater than or equal to85% of conjugate-vaccine recipients 104 weeks later. Type V CPS-specific immunoglobulin M was a dominant isotype of immune response to each conjugate. Postimmunization serum samples promoted opsonophagocytic killing of GBS type V in vitro, whereas those from placebo recipients did not. Conclusion. GBS type V conjugate vaccines are safe and immunogenic and would be appropriate for inclusion in a candidate multivalent GBS vaccine.