The protective effect of two porcine enterovirus vaccines in swine.

Piglets vaccinated with a single oral dose of live porcine enterovirus strain T80 were protected to a highly significant degree against an oral challenge dose of 140 plaque forming units of T80 virus, in comparison with nonvaccinated controls, in terms of serum antibody response, titres and distribution of virus in the gastrointestinal tract contents and tissues and duration of virus excretion in the feces. Piglets vaccinated with multiple doses of adjuvanted, PE60-concentrated ethylenimine-inactivated virus administered both orally and subcutaneously showed only a slight degree of protection against the same challenge dose, despite the fact that they possessed high serum antibody titres at the time of challenge. Piglets vaccinated orally with live virus showed a degree of protection even against a challenge dose of 10(7.41) plaque forming units of T80 virus in terms of titres and distribution of virus in the gastrointestinal tract and duration of excretion of virus in the feces. Protection in the piglets dosed orally with live virus appeared to be attributable to the presence of relatively high levels of virus neutralizing antibody of the IgA class in the gastrointestinal tract.