The Use of Killed Vaccines in Immunization against an Intracellular Parasite: Toxoplasma Gondii

Abstract

The pretreatment of mice with antigens prepared from killed Toxoplasma gondii induced long term protection against challenge with this organism. Resistance was measured in terms of length of survival and number of deaths following challenge with graded doses of the relatively avirulent C56 strain of Toxoplasma, and was observed when antigen was administered alone or incorporated into Freund's incomplete adjuvant. Freund's complete adjuvant also afforded significant protection. A protective role for humoral antibody was observed as significant resistance following the passive transfer of high titer anti-Toxoplasma antisera.