Anti-capsular antibodies activate killing of Escherichia coli O8:K87 by the alternate complement pathway in porcine serum

N. M. Clark, E. M. Berberov, M. Wang, R. A. Moxley

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Enterotoxigenic Escherichia coli (ETEC) strains that produce K88 (F4)+ fimbria are important causes of diarrhea and post-diarrheal septicemia in swine. ETEC O8:K87, a serotype represented by a number of these strains, is typically serum resistant. Strain-specific antibodies are known to activate alternative C pathway-mediated killing of other serum-resistant E. coli [Hill, A.W., Shears, A.L., Hibbitt, K.G., 1978. The requirement of specific antibody for the killing of E. coli by the alternate complement pathway in bovine serum. Immunology 34, 131-136], but their antigenic targets have not been determined. We tested the hypothesis that anti-K87 antibodies activate alternative pathway-mediated killing of ETEC O8:K87. Pigs were immunized with ETEC O8:K87 strain 2534-86 cells or purified K87 polysaccharide. Post-, but not pre-immunization sera killed 2534-86 cells, and absorption with 2534-86 cells or by K87 affinity chromatography eliminated bactericidal activity. Complementation of absorbed serum with anti-K87 antibodies restored bactericidal activity, confirming the ability of these antibodies to activate C-mediated serum killing. Serum from age-matched, non-vaccinated control pigs also killed 2534-86. This activity was eliminated by absorption with 2534-86 cells, but not K87 affinity chromatography, indicating that specific non-capsular antibodies are also able to activate C-mediated killing. In all cases, Mg-EGTA-treated serum was as effective as non-treated serum in killing, suggesting that bactericidal activity was mediated predominantly if not exclusively via the alternative C pathway.

Original languageEnglish (US)
Pages (from-to)185-191
Number of pages7
JournalVeterinary Immunology and Immunopathology
Issue number1-2
StatePublished - Nov 15 2006


  • Alternative complement pathway
  • Anti-capsular antibodies
  • Capsule
  • Enterotoxigenic E. coli
  • Escherichia coli
  • K87
  • Pig
  • Polysaccharide
  • Porcine
  • Serum resistance

ASJC Scopus subject areas

  • Immunology
  • veterinary(all)


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