Cellular immune response induced by surface immunogenic protein with AbISCO-100 adjuvant vaccination decreases group B Streptococcus vaginal colonization

Group B Streptococcus (GBS) represents one of the most common causes of bacterial infection in neonates; it is also associated with premature childbirth and stillbirth. A vaccine against GBS is needed, but no approved vaccines are yet available. The Surface Immunogenic Protein (SIP) of GBS is conserved in all serotypes and had been reported to be a good vaccine prototype in a mouse model of GBS infection. Also, we have previously shown that both subcutaneous and oral immunization with rSIP can induce an efficient immune response that decreases GBS vaginal colonization in mice. In this study, we show that a vaccine based on a mixture of rSIP and AbISCO-100 adjuvant reduces GBS vaginal colonization in mice and induces antibodies with opsonophagocytic activities. Moreover, the passive transfer of sera and total T-cells from mice immunized with rSIP mixed with AbISCO-100 to unvaccinated mice decreases vaginal GBS colonization in an infected mouse. This is the first report of cellular immunity associated with rSIP-based vaccine testing in a mouse model of GBS infection.