Salmonella typhimurium as a basis for a live oral Echinococcus granulosus vaccine.

A live attenuated Salmonella typhimurium vaccine candidate, LVR01, was constructed by introducing a null deletion into the aroC gene of the parental canine S. typhimurium isolate, P228067. LVR01 was used to orally deliver to the canine immune system a fatty acid binding protein (FABP) from Echinococcus granulosus (EgDf1), as a fusion protein with fragment C (TetC) of tetanus toxin. Immunization studies demonstrated that live LVR01 is well tolerated by orally vaccinated dogs. There was no detectable shedding of the vaccine strain in the faeces 2 days after immunization. Humoral antibody responses were observed against Salmonella, TetC and EgDf1. Cellular responses were consistently detected against Salmonella and TetC. A cellular response against EgDf1 was also seen in a proportion of the LVR01 vaccinated dogs. We propose S. typhimurium LVR01 as a carrier for recombinant antigens and a vector for the construction of multivalent oral vaccines for dogs.