Protective immunization in mice against group B streptococci using encapsulated C5a peptidase.

Abstract

OBJECTIVE: The purpose of the study was to test whether C5a peptidase encapsulated within a biodegradable polymer can act as a vaccine and elicit an immune response to prevent group B streptococci (GBS) infection in mice and provide protection to pups. STUDY DESIGN: C5a peptidase was encapsulated in semipermeable microspheres of poly(lactide-co-glycolide). Female ICR mice were immunized with encapsulated C5a peptidase, free C5a peptidase, or empty microparticles. Booster doses were given at days 21 and 42. Antibody responses were measured by enzyme-linked immunosorbent assay. Challenge with GBS type III was performed 4 days after the final booster in the vaginal vault of adult mice and intraperitoneally 48 hours after the birth for pups. RESULTS: Encapsulated C5a peptidase elicited a systemic immunoglobulin (Ig) G antibody response after intramuscular and intranasal administration. Unencapsulated C5a peptidase elicited a smaller systemic response. In addition to the strong IgG response, a secretory IgA response was observed in the vaginal mucosa after intranasal vaccination. No evidence of GBS colonization was found in vaccinated mice. Eighty-seven percent and 81% of the pups from intramuscularly and intranasally vaccinated dams survived a 90% lethal dose (LD90) GBS challenge vs 9% born to nonvaccinated dams. CONCLUSION: Encapsulated C5a peptidase elicited significant immune responses and protection against GBS challenge. C5a peptidase microsphere encapsulation has potential as a GBS vaccine.