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Infection and Immunity, May 2001, p. 3067-3072, Vol. 69, No. 5
Department of Molecular Genetics,
Biochemistry and Microbiology, University of Cincinnati,
Cincinnati, Ohio 45267
Received 28 November 2000/Returned for modification 12 January
2001/Accepted 5 February 2001
Bordetella pertussis produces a 73-kDa protein,
BrkA (Bordetella resistance to killing), which inhibits
the bactericidal activity of complement. In this study we characterized
the step in the complement cascade where BrkA acts, using three
strains: a wild-type strain, a strain containing an insertional
disruption of brkA, and a strain containing two copies
of the brkA locus. Following incubation with 10% human
serum, killing was greatest for the BrkA mutant, followed by that for
the wild-type strain, while the strain with two copies of
brkA was the most resistant. Complement activation was
monitored by enzyme-linked immunosorbent assay (ELISA) or Western
blotting. ELISAs for SC5b-9, the soluble membrane attack complex,
showed that production of SC5b-9 was greatest with the
brkA mutant, less with the wild type, and least with the
strain containing two copies of brkA. Deposition of
complement proteins on the bacteria was monitored by Western blotting.
A decrease in deposition on the bacteria of C4, C3, and C9 corresponded with decreased complement sensitivity. Deposition of C1, however, was
not affected by the presence of BrkA. These studies show that BrkA
inhibits the classical pathway of complement activation and prevents
accumulation of deposited C4.
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.5.3067-3072.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
BrkA Protein of Bordetella pertussis
Inhibits the Classical Pathway of Complement after C1
Deposition
*
Corresponding author. Mailing address: Department of
Molecular Genetics, Biochemistry and Microbiology, University of
Cincinnati, 231 Sabin Way, ML 0524, Cincinnati, OH 45230. Phone: (513)
558-2820. Fax: (513) 558-7484. E-mail:
Alison.Weiss{at}uc.edu.
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