Findings published in the Journal of Infectious Diseases supported ongoing clinical evaluation of maternal vaccination with capsular polysaccharide conjugate vaccine GBS6 as an alternative method of prevention of infection with group B streptococcus (GBS) in infants.

Immune responses in mice and rhesus macaques to the GBS6 vaccine were evaluated in a multiplex Luminex immunoglobulin G (IgG) assay and opsonophagocytic activity assays. The vaccine itself was designed using whole-genome sequencing surveillance data from recent global isolates of GBS, which were responsible for invasive neonatal GBS disease.

Optimized conjugates of capsular polysaccharides induced IgG antibodies that mediated opsonophagocytic killing, alone or in combination, in mice and rhesus macaques. Serotype-specific protection of murine pups from a lethal challenge with group B streptococcus was achieved with active immunization of pregnant mice (dams) with GBS6 before mating. Protection after passive administration of serotype-specific IgG monoclonal antibodies to dams showed that anticapsular polysaccharide IgG by itself is enough for protection.

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According to study investigators, there is a severe unmet medical need for the prevention of early and late onset of GBS infection in infants worldwide. The GBS6 vaccine was developed to cover potentially 98% of GBS infections in infants, and preclinical studies such as this “demonstrated protection of pups born to vaccinated mice and a robust IgG-mediated functional immune response in rhesus macaques.” Researchers believed, therefore, that vaccination of pregnant women will elicit strong functional and protective responses that will transfer to infants before birth. However, ongoing clinical studies in nonpregnant volunteers are needed to evaluate the translation of preclinical results into clinical safety and immunogenicity.

Reference

Buurman ET, Timofeyeva Y, Gu J, et al. A novel hexavalent capsular polysaccharide conjugate vaccine (GBS6) for the prevention of neonatal group B streptococcal infections by maternal immunization [published online February 19 2019]. J Infect Dis. doi: 10.1093/infdis/jiz062