Vaccination with hatched but non-activated, non-viable oncospheres of Taenia taeniaeformis in rats.

The usefulness of hatched but non-activated oncospheres as a candidate vaccine was evaluated using a Taenia taeniaeformis/rat system, since preparation of these oncospheres in vitro is known to be very simple. The findings were: (1) rats vaccinated with non-viable oncospheres became completely resistant to challenge infection; (2) intra-venous injection was the most effective to induce complete resistance; (3) a single oncosphere was sufficient to induce complete resistance in infected rats, whereas approximately 50 and 500 non-viable oncospheres were required to evoke strong and complete resistance, respectively, in vaccinated rats. The usefulness of non-viable oncospheres without adjuvant is discussed.