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Infection and Immunity, January 2001, p. 472-478, Vol. 69, No. 1
Institut für Mikrobiologie und
Tierseuchen1 and Klinik für Kleine
Klauentiere,2 Tieraerztliche Hochschule
Hannover, 30173 Hanover, and Abteilung für Funktionelle
und Angewandte Anatomie, Medizinische Hochschule Hannover, 30625 Hanover,3 Germany
Received 8 August 2000/Returned for modification 26 September
2000/Accepted 25 October 2000
Actinobacillus pleuropneumoniae, a porcine respiratory
tract pathogen, has been shown to express transferrin-binding proteins and urease during infection. Both activities have been associated with
virulence; however, their functional role for infection has not yet
been elucidated. We used two isogenic A. pleuropneumoniae single mutants (
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.1.472-478.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Actinobacillus pleuropneumoniae Iron Transport and
Urease Activity: Effects on Bacterial Virulence and Host Immune
Response
exbB and
ureC) and a
newly constructed A. pleuropneumoniae double
(
ureC
exbB) mutant in aerosol infection
experiments. Neither the A. pleuropneumoniae
exbB mutant nor the double
ureC
exbB mutant was able to colonize sufficiently long to
initiate a detectable humoral immune response. These results imply that the ability to utilize transferrin-bound iron is required for multiplication and persistence of A. pleuropneumoniae in the porcine respiratory tract. The
A. pleuropneumoniae
ureC mutant and the parent strain both caused infections that were indistinguishable from
one another in the acute phase of disease; however, 3 weeks postinfection the A. pleuropneumoniae
ureC
mutant, in contrast to the parent strain, could not be isolated from
healthy lung tissue. In addition, the local immune response
as
assessed by fluorescence-activated cell sorter and enzyme-linked
immunosorbent spot analyses
revealed a significantly higher number of
A. pleuropneumoniae-specific B cells in the bronchoalveolar
lavage fluid (BALF) of pigs infected with the A. pleuropneumoniae
ureC mutant than in the BALF of those infected with the parent strain. These results imply that A. pleuropneumoniae urease activity may cause sufficient
impairment of the local immune response to slightly improve the
persistence of the urease-positive A. pleuropneumoniae
parent strain.
*
Corresponding author. Mailing address: Tieraerztliche
Hochschule Hannover, Institut fuer Mikrobiologie und Tierseuchen,
Bischofsholer Damm 15, 30173 Hanover, Germany. Phone:
49-511-856-7598. Fax: 49-511-856-7697. E-mail:
gfgerlach{at}gmx.de.
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