title: The Protective Value of Maternal Group B Streptococcus Antibodies: Quantitative and Functional Analysis of Naturally Acquired Responses to Capsular Polysaccharides and Pilus Proteins in European Maternal Sera.
abstract: Group B Streptococcus (GBS) is a major cause of neonatal sepsis and meningitis. A vaccine targeting pregnant women could protect infants through placentally transferred antibodies. The association between GBS maternal antibody concentrations and the risk of neonatal infection has been investigated in US and African populations. Here we studied naturally acquired immunoglobulin G (IgG) responses to GBS capsular polysaccharides (CPS) and pilus proteins in European pregnant women.
  
  
  
  Maternal sera were prospectively collected in 8 EU countries from 473 GBS non-colonized and 984 colonized pregnant women who delivered healthy neonates and from 153 mothers of infants with GBS disease. GBS strains from these colonized women and infected infants were obtained in parallel and their capsular and pilus types were identified by serological and molecular methods. Maternal serum concentrations of IgG anti- Ia, -Ib, -III and -V polysaccharides and anti-BP-1, -AP1-2a and -BP-2b pilus proteins were determined by enzyme-linked immunosorbent assay. Antibody functional activity was quantified by Opsonophagocytic Killing Assay.
  
  
  
  Antibody levels against CPS and pilus proteins were significantly higher in GBS colonized women delivering healthy babies than in mothers of neonates with GBS disease or non-colonized women. Moreover, maternal anti-capsular IgG concentrations showed a significant correlation with functional titers measured by Opsonophagocytic Killing Assay.
  
  
  
  Maternal anti-capsular IgG concentrations above 1 µg/mL mediated GBS killing in vitro and were predicted to respectively reduce by 81% (95% confidence interval, 40%-100%) and 78% (45%-100%) the risk of GBS Ia and III early-onset disease in Europe.
authors.affiliation: GSK Vaccines Srl, Siena.
authors.forename: Monica
authors.initials: M
authors.lastname: Fabbrini
authors.affiliation: GSK Vaccines Srl, Siena.
authors.forename: Fabio
authors.initials: F
authors.lastname: Rigat
authors.affiliation: GSK Vaccines Srl, Siena.
authors.forename: C Daniela
authors.initials: CD
authors.lastname: Rinaudo
authors.affiliation: GSK Vaccines Srl, Siena.
authors.forename: Irene
authors.initials: I
authors.lastname: Passalaqua
authors.affiliation: GSK Vaccines Srl, Siena.
authors.forename: Sceida
authors.initials: S
authors.lastname: Khacheh
authors.affiliation: Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Creti
authors.affiliation: Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Lucilla
authors.initials: L
authors.lastname: Baldassarri
authors.affiliation: GSK Vaccines Srl, Siena.
authors.forename: Filippo
authors.initials: F
authors.lastname: Carboni
authors.affiliation: GSK Vaccines Srl, Siena.
authors.forename: Giulia
authors.initials: G
authors.lastname: Anderloni
authors.affiliation: GSK Vaccines Srl, Siena.
authors.forename: Roberto
authors.initials: R
authors.lastname: Rosini
authors.affiliation: GSK Vaccines Srl, Siena.
authors.forename: Domenico
authors.initials: D
authors.lastname: Maione
authors.affiliation: GSK Vaccines Srl, Siena.
authors.forename: Guido
authors.initials: G
authors.lastname: Grandi
authors.affiliation: GSK Vaccines Srl, Siena.
authors.forename: John L
authors.initials: JL
authors.lastname: Telford
authors.affiliation: GSK Vaccines Srl, Siena.
authors.forename: Immaculada
authors.initials: I
authors.lastname: Margarit
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood*; D005060:Europe / Q000453:epidemiology; D005260:Female; D010861:Fimbriae, Bacterial / Q000276:immunology*; D006801:Humans; D007112:Immunity, Maternally-Acquired; D007074:Immunoglobulin G / Q000097:blood; D011135:Polysaccharides, Bacterial / Q000276:immunology*; D011247:Pregnancy; D011446:Prospective Studies; D013290:Streptococcal Infections / Q000453:epidemiology / Q000276:immunology*; D013292:Streptococcus agalactiae / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; D011135:Polysaccharides, Bacterial
keywords: Streptococcus agalactiae; capsular polysaccharide; group B Streptococcus; immune response; neonatal infection; pilus island