Acquired resistance to Fasciola hepatica in cattle using a purified adult worm antigen.

Calves were immunized twice in 4 weeks with a Fasciola/Schistosoma cross-reactive, cross-protective defined immunity antigen (denoted FhSmIII(M)) isolated from F. hepatica adult worm extracts by antibody affinity chromatography and challenged 7 weeks later with F. hepatica metacercariae. Flukes were recovered at 16 weeks of infection at which time the immunized calves had 55% less F. hepatica than the controls. All of the immunized calves developed high antibody levels of FhSmIII(M), detectable in the ELISA, by 4 weeks after a single immunization. By 9 weeks of infection with F. hepatica the immunized calves had lower sorbitol dehydrogenase levels than the unimmunized, F. hepatica-infected control calves, indicating less liver damage in the vaccinated group. These studies demonstrate that subcellular F. hepatica macromolecules cross-reactive and cross-protective against S. mansoni also have the potential to serve as vaccines in cattle exposed to this parasitic disease.