FIG. 2.

Protection by N. caninum vaccination is dose dependent. A/J mice were vaccinated with 10⁶, 5 × 10⁵, or 5 × 10⁴ tachyzoites of N. caninum. Postvaccination the mice were challenged with 2.5 × 10⁴ PLK strain tachyzoites of T. gondii via intraperitoneal inoculation. Control mice were sham vaccinated with saline. Mice were examined daily for evidence of clinical infection, and mortality was used as the end point. Results are representative of two experiments (n = 12 mice/group).