Survival rate of the immunized mice. All four groups of the immunized mice (phosphate-buffered saline [PBS], pcDNA 3.1C, pcGRA2, and pcGRA5) were subjected to lethal challenge with 1,000 live tachyzoites of Toxoplasma gondii-virulent RH strain 3 weeks after the last immunization. Mice immunized with pcGRA2 and pcGRA5 demonstrated a minor increase in their survival days (median survival of 8 days) in comparison to that of the control mice injected with phosphate-buffered saline and pcDNA 3.1C (median survival of 6 and 7 days, respectively). Each group consisted of 10 mice.