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Infect. Immun., 08 1997, 3048-3056, Vol 65, No. 8
CP Simmons, AL Hodgson and RA Strugnell
Corynebacterium pseudotuberculosis, a gram-positive intracellular bacterial
pathogen, is the etiological agent of the disease caseous lymphadenitis
(CLA) in both sheep and goats. Attenuated mutants of C. pseudotuberculosis
have the potential to act as novel live veterinary vaccine vectors. We have
cloned and sequenced the aroB and aroQ genes from C. pseudotuberculosis
C231. By allelic exchange, aroQ mutants of both C231, designated CS100, and
a pld mutant strain TB521, designated CS200, were constructed. Infection of
BALB/c mice indicated that introduction of the aroQ mutation into C231 and
TB521 attenuated both strains. In sublethally infected BALB/c mice, both
CS100 and CS200 were cleared from spleens and livers by day 8
postinfection. The in vivo persistence of these strains was increased when
the intact aroQ gene was supplied on a plasmid in trans. Mice infected with
TB521 harbored bacteria in organs at least till day 8 postinfection without
ill effect. When used as a vaccine, only the maximum tolerated dose of
CS100 had the capacity to protect mice from homologous challenge.
Vaccination with TB521 also elicited protective immunity, and this was
associated with gamma interferon (IFN-gamma) production from splenocytes
stimulated 7 days postvaccination. The role of IFN-gamma in controlling
primary infections with C. pseudotuberculosis was examined in mice
deficient for the IFN-gamma receptor (IFN-gammaR(-/-) mice).
IFN-gammaR(-/-) mice cleared an infection with CS100 but were significantly
more susceptible than control littermates to infection with C231 or TB521.
These studies support an important role for IFN- gamma in control of
primary C. pseudotuberculosis infections and indicate that aroQ mutants
remain attenuated even in immunocompromised animals. This is the first
report of an aroQ mutant of a bacterial pathogen, and the results may have
implications for the construction of aromatic mutants of Mycobacterium
tuberculosis for use as vaccines.
Copyright © 1997, American Society for Microbiology
Attenuation and vaccine potential of aroQ mutants of Corynebacterium pseudotuberculosis
CRC for Vaccine Technology and Department of Microbiology and Immunology, University of Melbourne, Parkville, Victoria, Australia.
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