Delivery of Echinococcus granulosus antigen EG95 to mice and sheep using recombinant vaccinia virus

SUMMARY The tapeworm Echinococcus granulosus is the causativeagent of hydatid disease and affects sheep, cattle, dogs andhumans worldwide. It has a two-stage life cycle existing asworms in the gut of infected dogs (definitive host) and ascysts in herbivores and humans (intermediate host). Thedisease is debilitating and can be life threatening where thecysts interfere with organ function. Interruption of the hyda-tid life cycle in the intermediate host by vaccination may bea way to control the disease, and a protective oncosphereantigen EG95 has been shown to protect animals againstchallenge with E. granulosus eggs. We explored the use ofrecombinant vaccinia virus as a delivery vehicle for EG95.Mice and sheep were immunized with the recombinant vec-tor, and the result monitored at the circulating antibodylevel. In addition, sera from immunized mice were assayedfor the ability to kill E. granulosus oncospheres in vitro.Mice immunized once intranasally developed effective onco-sphere-killing antibody by day 42 post-infection. Antibodyresponses and oncosphere killing were correlated and weresignificantly enhanced by boosting mice with either EG95protein or recombinant vector. Sheep antibody responses tothe recombinant vector or to EG95 protein mirrored those inmice.Keywords Echinococcus granulosus, EG95, hydatid, recom-binant poxvirus vaccine, vaccinia virus