title: Group B streptococcal conjugate vaccines elicit functional antibodies independent of strain O-acetylation.
abstract: Recently, it was discovered that sialic acid residues on group B streptococcal (GBS) capsular polysaccharides (CPS) are O-acetylated. Since GBS vaccine development has focused on de-O-acetylated CPS, it became germane to investigate the influence of de-O-acetylated GBS vaccine formulations on functional activity of sera against strains that bear the O-acetyl modification. Post-immunization sera from healthy adult recipients of de-O-acetylated GBS CPS-tetanus toxoid conjugate vaccines were evaluated in opsonophagocytosis assays using 20 GBS clinical isolates representing type Ia, Ib, II, III, or V CPS that varied in amount of O-acetylation from 2% to 40%. Ninety percent or greater opsonophagocytosis and killing of all strains were achieved, using CPS type-specific post-immunization sera. These data indicate that de-O-acetylated CPS-conjugate vaccines contain immunogenic epitopes that offer protection against GBS, independent of O-acetyl CPS modifications. Thus, presence of O-acetyl groups on the GBS CPS is not essential for functional antibodies to be elicited by GBS glycoconjugate vaccines.
authors.affiliation: Section of Infectious Diseases, Department of Pediatrics, Baylor College of Medicine and Texas Children's Hospital, Houston, TX, United States. ppannaraj@chla.usc.edu
authors.forename: Pia S
authors.initials: PS
authors.lastname: Pannaraj
authors.forename: Morven S
authors.initials: MS
authors.lastname: Edwards
authors.forename: Kristen T
authors.initials: KT
authors.lastname: Ewing
authors.forename: Amanda L
authors.initials: AL
authors.lastname: Lewis
authors.forename: Marcia A
authors.initials: MA
authors.lastname: Rench
authors.forename: Carol J
authors.initials: CJ
authors.lastname: Baker
mesh_terms: D000107:Acetylation; D000328:Adult; D000907:Antibodies, Bacterial / Q000097:blood / Q000276:immunology*; D016667:Bacterial Capsules / Q000276:immunology*; D006801:Humans; D019158:N-Acetylneuraminic Acid / Q000276:immunology / Q000378:metabolism; D010587:Phagocytosis; D013290:Streptococcal Infections / Q000276:immunology / Q000517:prevention & control*; D022541:Streptococcal Vaccines / Q000276:immunology*; D018074:Vaccines, Conjugate / Q000276:immunology; D014614:Vaccines, Synthetic / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D022541:Streptococcal Vaccines; D018074:Vaccines, Conjugate; D014614:Vaccines, Synthetic; D019158:N-Acetylneuraminic Acid