Association of natural induced antibodies against select Group B streptococcus surface proteins and invasive disease in early infancy

Abstract

Abstract Background Group B streptococcus (GBS) surface protein epitopes are potential targets for development of vaccines that could confer protection against invasive GBS disease (IGbsD) irrespective of the capsular serotype. The aim of this study was to determine the association of natural acquired mother-newborn GBS surface proteins specific serum IgG and IGbsD during early infancy (<90 days age). Methods Clinical GBS isolates from 81 women who delivered either infant with IGbsD (n=38) and healthy controls (n=43) were assessed for surface expression of proteins Sip, GBS0393 and GBS206 using flow cytometry. Serum IgG titres to Sip, GBS0393 and GBS206 surface proteins were measured in paired maternal-infant sera on multiplex Luminex platform to determine IgG titres associated with reduce risk of IGbsD caused by GBS strains expressing homotypic protein. Results Infant sera IgG GMT in IGbsD cases caused by strains expressing Sip and GBS2016 were lower (64 and 61 U/ml, respectively) compared to healthy controls born to women colonized by strains expressing the respective proteins (145 and 151 U/mL, respectively, p<0.01). Moreover, increasing infant antibody titres against Sip and GBS2016 were associated with ≥80% adjusted disease risk (ADR) reduction to GBS isolates expressing homotypic proteins. Among women colonized with GBS isolates expressing GBS2106, mothers of cases had lower GBS2016-specific IgG GMT (249 U/mL) compared to mothers of controls (163 U/mL, adj-p=0.023). Conclusion Increasing infant IgG titres to GBS2106 and Sip was associated with reduced IGbsD risk and therefore warranting further investigations as potential GBS vaccines and/or protein conjugants.