| Summary: | Brucella ovis is a non-zoonotic rough Brucella that causes genital lesions, abortions and increased perinatal mortal‑
ity in sheep and is responsible for important economic losses worldwide. Research on virulence factors of B. ovis is
necessary for deciphering the mechanisms that enable this facultative intracellular pathogen to establish persistent
infections and for developing a species-specifc vaccine, a need in areas where the cross-protecting ovine smooth
B. melitensis Rev1 vaccine is banned. Although several B. ovis virulence factors have been identifed, there is little
information on its metabolic abilities and their role in virulence. Here, we report that deletion of pyruvate phosphate
dikinase (PpdK, catalyzing the bidirectional conversion pyruvate ⇌ phosphoenolpyruvate) in B. ovis PA (virulent
and CO2-dependent) impaired growth in vitro. In cell infection experiments, although showing an initial survival
higher than that of the parental strain, this ppdK mutant was unable to multiply. Moreover, when inoculated at high
doses in mice, it displayed an initial spleen colonization higher than that of the parental strain followed by a marked
comparative decrease, an unusual pattern of attenuation in mice. A homologous mutant was also obtained in a B.
ovis PA CO2-independent construct previously proposed for developing B. ovis vaccines to solve the problem that
CO2-dependence represents for large scale production. This CO2-independent ppdK mutant reproduced the growth
defect in vitro and the multiplication/clearance pattern in mouse spleens, and is thus an interesting vaccine candidate
for the immunoprophylaxis of B. ovis ovine brucellosis.
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