A Test of Virulence and Live-Vaccine Efficacy for a phoQ Derivative of Salmonella choleraesuis
Perdue, Scott P.
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Salmonellosis is a worldwide problem that affects both humans and food-producing animals. Salmonella choleraesuis is a host adapted to swine and is often the etiologic agent of a fatal septicemia. Vaccination is an appropriate strategy for control of and protection against salmonellosis and several studies have shown that live vaccines are more efficacious than killed vaccines for inducing protective immunity in pigs. In this study, we examined the possibility of using a phoQ derivative of S. choleraesuis for the development of a safe and efficacious vaccine. PhoQ is part of a two-component system that is important for the regulation of virulence in Salmonella. An isogenic mutant (phoQ) of a pig-virulent strain of S. choleraesuis was constructed by transposon-mediated mutagenesis. This strain was evaluated for safety and protective efficacy as a live vaccine in mice and pigs after oral administration. In mice, this vaccine construct was highly attenuated by both oral and intraperitoneal (IP) routes. In pigs, it did not cause significant clinical signs of disease but did elicit a protective immune response. These data suggest that a live phoQ mutant strain may serve as a useful vaccine for the prevention of porcine salmonellosis