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Infection and Immunity, May 1999, p. 2090-2095, Vol. 67, No. 5
Departments of
Pharmacology1 and
Medicine,2 University of Virginia,
Charlottesville, Virginia, and Institute for Microbiology,
Czech Academy of Sciences, Prague, Czech Republic3
Received 28 October 1998/Returned for modification 16 December
1998/Accepted 26 January 1999
Adenylate cyclase (AC) toxin from Bordetella pertussis
is a 177-kDa repeats-in-toxin (RTX) family protein that consists of four principal domains; the catalytic domain, the hydrophobic domain,
the glycine/aspartate-rich repeat domain, and the secretion signal
domain. Epitope mapping of 12 monoclonal antibodies (MAbs) directed
against AC toxin was conducted to identify regions important for the
functional activities of this toxin. A previously developed panel of
in-frame deletion mutants of AC toxin was used to localize MAb-specific
epitopes on the toxin. The epitopes of these 12 MAbs were located
throughout the toxin molecule, recognizing all major domains. Two MAbs
recognized a single epitope on the distal portion of the catalytic
domain, two reacted with the C-terminal 217 amino acids, one bound to
the hydrophobic domain, and one bound to either the hydrophobic domain
or the functionally unidentified region adjacent to it. The remaining
six MAbs recognized the glycine/aspartate-rich repeat region. To
localize these six MAbs, different peptides derived from the repeat
region were constructed. Two of the six MAbs appeared to react with the
repetitive motif and exhibited cross-reactivity with Escherichia
coli hemolysin. The remaining four MAbs appeared to interact with
unique epitopes within the repeat region. To evaluate the roles of
these epitopes on toxin function, each MAb was screened for its effect
on intoxication (cyclic AMP accumulation) and hemolytic activity. The
two MAbs recognizing the distal portion of the catalytic domain blocked intoxication of Jurkat cells by AC toxin but had no effect on hemolysis. On the other hand, a MAb directed against a portion of the
repeat region caused partial inhibition of AC toxin-induced hemolysis
without affecting intoxication. In addition, the MAb recognizing either
the hydrophobic domain or the unidentified region adjacent to it
inhibited both intoxication and hemolytic activity of AC toxin. These
findings extend our understanding of the regions necessary for the
complex events required for the biological activities of AC toxin and
provide a set of reagents for further study of this novel virulence factor.
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Epitope Mapping of Monoclonal Antibodies against
Bordetella pertussis Adenylate Cyclase Toxin

*
Corresponding author. Mailing address: Box 419, School
of Medicine, University of Virginia, Charlottesville, VA 22908. Phone: (804) 924-5945. Fax: (804) 982-3830. E-mail:
eh2v{at}virginia.edu.
Present address: Department of Protein Chemistry, Immunnex
Corp., Seattle, WA 98101.
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