title: Development and use of a serum bactericidal assay using pooled human complement to assess responses to a meningococcal group A conjugate vaccine in African toddlers.
abstract: A meningococcal group A polysaccharide (PS) conjugate vaccine (PsA-TT) has been developed for African countries affected by epidemic meningitis caused by Neisseria meningitidis. Complement-mediated serum bactericidal antibody (SBA) assays are used to assess protective immune responses to meningococcal vaccination. Human complement (hC') was used in early studies demonstrating antibody-mediated protection against disease, but it is difficult to obtain and standardize. We developed and evaluated a method for sourcing hC' and then used the SBA assay with hC' (hSBA) to measure bactericidal responses to PsA-TT vaccination in 12- to 23-month-old African children. Sera with active complement from 100 unvaccinated blood donors were tested for intrinsic bactericidal activity, SBA titer using rabbit complement (rSBA), and anti-group A PS antibody concentration. Performance criteria and pooling strategies were examined and then verified by comparisons of three independently prepared hC' lots in two laboratories. hSBA titers of clinical trial sera were then determined using this complement sourcing method. Two different functional antibody tests were necessary for screening hC'. hSBA titers determined using three independent lots of pooled hC' were within expected assay variation among lots and between laboratories. In African toddlers, PsA-TT elicited higher hSBA titers than meningococcal polysaccharide or Hib vaccines. PsA-TT immunization or PS challenge of PsA-TT-primed subjects resulted in vigorous hSBA memory responses, and titers persisted in boosted groups for over a year. Quantifying SBA using pooled hC' is feasible and showed that PsA-TT was highly immunogenic in African toddlers.
authors.affiliation: Center for Biologics Evaluation and Research, FDA, Bethesda, Maryland, USA.
authors.forename: Margaret C
authors.initials: MC
authors.lastname: Bash
authors.forename: Freyja
authors.initials: F
authors.lastname: Lynn
authors.forename: Brian
authors.initials: B
authors.lastname: Mocca
authors.forename: Ray
authors.initials: R
authors.lastname: Borrow
authors.forename: Helen
authors.initials: H
authors.lastname: Findlow
authors.forename: Musa
authors.initials: M
authors.lastname: Hassan-King
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Preziosi
authors.forename: Olubukola
authors.initials: O
authors.lastname: Idoko
authors.forename: Samba
authors.initials: S
authors.lastname: Sow
authors.forename: Prasad
authors.initials: P
authors.lastname: Kulkarni
authors.forename: F Marc
authors.initials: FM
authors.lastname: Laforce
mesh_terms: D000293:Adolescent; D000328:Adult; D000349:Africa; D000368:Aged; D001770:Blood Bactericidal Activity; D003165:Complement System Proteins / Q000276:immunology*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008585:Meningitis, Meningococcal / Q000517:prevention & control*; D022401:Meningococcal Vaccines / Q000008:administration & dosage / Q000276:immunology*; D008875:Middle Aged; D038381:Neisseria meningitidis, Serogroup A / Q000276:immunology*; D018074:Vaccines, Conjugate / Q000008:administration & dosage / Q000276:immunology; D055815:Young Adult
chemical_list: D022401:Meningococcal Vaccines; D018074:Vaccines, Conjugate; D003165:Complement System Proteins