Cross-protective immunity in calves conferred by a DNA adenine methylase deficient Salmonellaenterica serovar Typhimurium vaccine.

The global trend towards intensive livestock production is associated with increased fecal oral pathogen transmission resulting in a high prevalence of Salmonella. Since many pathogenic Salmonella serovars are often endemic to livestock production systems, it is desirable to develop a vaccine that is capable of eliciting immunity to more than one serovar. Here we examined whether immunization with a modified live Salmonella enterica serovar Typhimurium vaccine strain lacking the DNA adenine methylase (Dam) conferred protection in calves against a heterologous S. enterica Dublin challenge. Vaccinated animals challenged with a virulent Dublin strain exhibited a significant attenuation of clinical disease (improved attitude scores and reduced fever and diarrhea) and a concomitant reduction in Dublin fecal shedding and colonization of mesenteric lymph nodes (MLN) compared to non-vaccinated control animals. These data suggest that vaccination with a dam(-) Typhimurium vaccine strain conferred significant cross-protection against clinical disease in cattle attributable to heterologous challenge with Dublin.