Development of a Recombinant Attenuated Salmonella Vaccine System for Taenia Solium Cysticercosis in Pigs

Taenia solium is a cestode that has a two-hosts life cycle. The adult tapeworm causes an asymptomatic disease known as taeniasis whereas the larval stage causes a disease called cysticercosis. In humans, the most common localization for the larvae is the central nervous system where it produces the neurological disorder neurocysticercosis. Previous works by several research groups around the world have shown that T. solium is a potentially eradicable parasite. Control programs have included treatment of human and pig populations with antihelmintics in conjunction with health education and are now considering vaccination of naïve piglets. The potential of a live vector vaccine system to deliver Taenia solium Tsol18, a proven protective antigen, to prevent transmission of cysticercosis was investigated. An attenuated strain of Salmonella enterica serovar Typhimurium χ9402 was used to develop an oral delivery system. Tsol18 gene was cloned downstream from the β-lactamase signal sequence in a multicopy asd + plasmid vector pYA3620 to yield plasmid pYA3620/Tsol18 and then transformed into the vaccine strain. The recombinant attenuated salmonella vaccine construct was stable for 50 generations and expressed rTsol18. Immunization of mice either with one or two doses of 10 CFU of the recombinant vaccine strain carrying plasmid pYA3620/Tsol18 elicited specific antibody response to Salmonella self antigens and to rTsol18. Moreover, oral immunization of piglets with 10 CFU of the vaccine construction significantly reduced the numbers of viable cysts after challenged. The development of a quantitative assay to detect specific antibodies against Tsol18 is also presented here. The Falcon assay screening test –enzyme linked immunoabsorbant assay (FAST-ELISA) format was used to develop a quantitative antibody detection assay. We have cloned, expressed and purified rTsol18. With purified porcine IgGs we constructed a standard curve that can be used to quantify the immune response. Our Fast-ELISA was able to follow the kinetics of the immune response in vaccinated pigs from an experimental trial. The data we present here provides the basis for a safe, affordable and easy vaccine delivery system that can be used as an adjunct in control programs. INDEX WORDS: Taenia solium, Cysticercosis, Salmonella, Vaccine, Tsol18, FastELISA. DEVELOPMENT OF A RECOMBINANT ATTENUATED SALMONELLA VACCINE SYSTEM FOR TAENIA SOLIUM CYSTICERCOSIS IN PIGS