Analyses for IgG titers of immunized mouse sera. Groups of mice were peritoneally immunized with one dose of PLG-rSAG1/2 MPs (●), one dose of rSAG1/2 (Vet L-10) (◆), two doses of rSAG1/2 (Vet L-10) (■), one dose of rSAG1/2 alone (○), one dose of blank PLG (◇), or one dose of PBS (□). Every two weeks, mouse sera were collected from different groups and their anti-Toxoplasma IgG titers were determined by ELISA. Results are presented as the mean of log₁₀ titers ± SD. All groups were analyzed by the Nest design and an asterisk (*) indicates P < 0.05 when comparing the PLG-rSAG1/2 (single I.P. dose) group to the rSAG1/2 (Vet L-10) (two I.P. doses) group.