title: Neisseria meningitidis Group A IgG1 and IgG2 Subclass Immune Response in African Children Aged 12-23 Months Following Meningococcal Vaccination.
abstract: BACKGROUND
  A group A meningococcal conjugate vaccine, PsA-TT, was licensed in 2010 and was previously studied in a phase 2 clinical trial to evaluate its safety and immunogenicity in African children 12-23 months of age.
  
  
  METHODS
  Subjects received either PsA-TT; meningococcal group A, C, W, Y polysaccharide vaccine (PsACWY); or Haemophilus influenzae type b conjugate vaccine (Hib-TT). Forty weeks following primary vaccination, the 3 groups were further randomized to receive either PsA-TT, one-fifth dose of PsACWY, or Hib-TT. Group A-specific immunoglobulin G (IgG) subclass response was characterized using an enzyme-linked immunosorbent assay.
  
  
  RESULTS
  The predominant IgG subclass response, regardless of vaccine, was IgG1. One month following primary vaccination, the geometric mean concentrations (GMCs) of IgG1 and IgG2 in the PsA-TT group were 21.73 µg/mL and 6.27 µg/mL, whereas in the PsACWY group the mean GMCs were 2.01 µg/mL and 0.97 µg/mL, respectively (P < .0001). Group A-specific IgG1 and IgG2 GMCs remained greater in the PsA-TT group than in the PsACWY group 40 weeks following primary vaccination (P < .0001). One week following revaccination, those given 2 doses of PsA-TT had the greatest IgG1 and IgG2 GMCs of 125.23 µg/mL and 36.12 µg/mL, respectively (P = .0008), and demonstrated a significant increase in IgG1:IgG2 mean ratio, indicative of the T-cell-dependent response associated with conjugate vaccines.
  
  
  CONCLUSIONS
  Vaccination of African children aged 12-24 months with either PsA-TT or PsACWY elicited a predominantly IgG1 response. The IgG1:IgG2 mean ratio decreased following successive vaccination with PsACWY, indicating a shift toward IgG2, suggestive of the T-cell-independent immune response commonly associated with polysaccharide antigens.
  
  
  BACKGROUND
  SRCTN78147026.
authors.affiliation: Vaccine Evaluation Unit, Public Health England, Manchester Royal Infirmary, United Kingdom.
authors.forename: Daniel
authors.initials: D
authors.lastname: Holme
authors.affiliation: Vaccine Evaluation Unit, Public Health England, Manchester Royal Infirmary, United Kingdom.
authors.forename: Helen
authors.initials: H
authors.lastname: Findlow
authors.affiliation: Centre pour le Développement des Vaccins, Ministère de la Santé, Bamako, Mali.
authors.forename: Samba O
authors.initials: SO
authors.lastname: Sow
authors.affiliation: Medical Research Council Unit, Basse, The Gambia.
authors.forename: Olubukola T
authors.initials: OT
authors.lastname: Idoko
authors.affiliation: Meningitis Vaccine Project, PATH, Ferney-Voltaire, France Meningitis Vaccine Project, Department of Immunization, Vaccines and Biologicals, World Health Organization, Geneva, Switzerland.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Preziosi
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: George
authors.initials: G
authors.lastname: Carlone
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Plikaytis
authors.affiliation: Vaccine Evaluation Unit, Public Health England, Manchester Royal Infirmary, United Kingdom.
authors.forename: Ray
authors.initials: R
authors.lastname: Borrow
mesh_terms: D000349:Africa; D000907:Antibodies, Bacterial / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D018073:Haemophilus Vaccines / Q000008:administration & dosage / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007223:Infant; D008297:Male; D022401:Meningococcal Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D038381:Neisseria meningitidis, Serogroup A / Q000276:immunology*; D013745:Tetanus Toxoid / Q000008:administration & dosage / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D018073:Haemophilus Vaccines; C055753:Haemophilus influenza type b polysaccharide vaccine-tetanus toxin conjugate; D007074:Immunoglobulin G; D022401:Meningococcal Vaccines; D013745:Tetanus Toxoid
keywords: IgG subclass; Neisseria meningitidis; meningococcal; vaccination