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Porin A-specific antibody avidity in patients who are convalescing from meningococcal B disease

Clementien L Vermont1, Harry H van Dijken, Ronald de Groot

  • 1Laboratory for Vaccine Research, Netherlands Vaccine Institute, 3720 AL Bilthoven, The Netherlands.

Pediatric Research
|March 19, 2005
PubMed

Insights

Children convalescing from meningococcal disease showed PorA-specific antibody avidity. Antibody avidity was highest against the infecting PorA subtype, but lower than after vaccination.

Area of Science:

  • Immunology
  • Microbiology
  • Vaccinology

Background:

  • Porin A (PorA) is the primary antigen in vaccines against serogroup B meningococci.
  • PorA determines the serosubtype of Neisseria meningitidis and elicits antibody responses.
  • Previous studies indicate PorA-based vaccines induce high-avidity antibodies in children.

Purpose of the Study:

  • To characterize the immune response in children post-meningococcal infection.
  • To assess antibody avidity and specificity following infection with a specific PorA subtype (P1.7-2,4).
  • To compare antibody avidity after natural infection versus vaccination.

Main Methods:

  • Collected acute- and convalescent-phase sera from 21 children with meningococcal septic shock.
  • Measured serum bactericidal antibody titers, IgG isotype distribution, and antibody avidity.
  • Assessed avidity against homologous, heterologous PorA subtypes, and PorA-negative strains.

Main Results:

  • Convalescent sera showed minimal bactericidal activity against the infecting strain.
  • IgG response was dominated by IgG(1) and IgG(3) isotypes.
  • Geometric Mean Avidity Index (GMAI) was significantly higher for the homologous PorA subtype (P1.7-2,4) compared to heterologous or PorA-negative strains (57% vs. 35% and 23%).
  • Antibody avidity after invasive meningococcal disease was lower than observed after vaccination in toddlers.

Conclusions:

  • The immune response to Neisseria meningitidis infection is PorA subtype-specific.
  • Antibody avidity following invasive meningococcal disease is lower than that induced by vaccination.
  • Findings highlight the importance of PorA in vaccine-induced immunity and suggest potential for improved vaccine strategies.

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