title: Persistence of group C anticapsular antibodies two to three years after immunization with an investigational quadrivalent Neisseria meningitidis-diphtheria toxoid conjugate vaccine.
abstract: BACKGROUND
  An investigational quadrivalent (A, C, Y and W-135) meningococcal conjugate (MC-4) vaccine was reported to be more immunogenic in 2-year-olds than the currently licensed meningococcal polysaccharide vaccine, but persistence of serum antibody beyond 6 months after conjugate vaccination is unknown.
  
  
  OBJECTIVE
  Determine persistence and the immunologic basis of protective activity of group C anticapsular antibodies in sera obtained 2-3 years after MC-4 vaccination.
  
  
  METHODS
  Group C antibody concentrations, bactericidal activity and passive protective activity were measured in sera from 48 children, ages 4-5 years, who had been immunized 2-3 years earlier with an MC-4 vaccine and from 47 children who had not been previously vaccinated.
  
  
  RESULTS
  Serum antibody concentrations were higher in the vaccinated than the unvaccinated children (geometric means, 0.30 and 0.09 mug/mL, respectively, P < 0.0001). Bactericidal titers > or =1/4 (considered protective) were infrequent in both vaccinated and unvaccinated children (14.6 and 6.4%, respectively, P = 0.3). Passive protective activity against bacteremia in the infant rat model was more frequent in sera from vaccinated (37.5%) than sera from unvaccinated children (12.5%, P < 0.02). The proportion of sera with passive protective activity increased with increasing anticapsular antibody concentrations (P < 0.0001).
  
  
  CONCLUSIONS
  Serum group C antibody concentrations remained elevated for 2-3 years after MC-4 vaccination, and passive protective activity was more frequent in vaccinated than unvaccinated children. However, serum antibody concentrations in many vaccinated children were no longer sufficient to activate complement-mediated bacteriolysis in vitro or to confer passive protection against experimental group C disease.
authors.affiliation: Children's Hospital Oakland Research Institute, Oakland, CA, USA.
authors.forename: Dan M
authors.initials: DM
authors.lastname: Granoff
authors.forename: Amy
authors.initials: A
authors.lastname: Morgan
authors.forename: Jo Anne
authors.initials: JA
authors.lastname: Welsch
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D016667:Bacterial Capsules / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D004195:Disease Models, Animal; D006801:Humans; D022401:Meningococcal Vaccines; D038542:Neisseria meningitidis, Serogroup C / Q000276:immunology*; D051381:Rats; D013997:Time Factors; D018074:Vaccines, Conjugate / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; C500411:MC-4 vaccine; D022401:Meningococcal Vaccines; D018074:Vaccines, Conjugate