Epitope analysis, expression and protection of SAG5A vaccine against Toxoplasma gondii.

Bioinformatics approaches were used to identify B-cell epitopes and T-cell epitopes on SAG5A protein. Compared to SAG1, SAG5A with good B-cell epitopes and T-cell epitopes had a potentiality to become a more successful vaccine against Toxoplasma gondii. Thereafter, SAG5A DNA vaccine was constructed successfully and was injected into mice with peptide to evaluate the immunoprotection. Compared to the control groups, the vaccine (DNA/peptide) could induce more effective cellular and humoral immune responses in immunized mice. Furthermore, a significant reduction of brain cyst was detected in the mice vaccinated with peptide (732±160), pSAG5A (815±197), or pSAG5A/peptide (436±174) compared by the mice injected by PBS (1260±241) or pEGFP-C1 (1350±268). The number of cysts in brains was 35% reduced in the mice immunized with DNA/peptide than in the control mice treated by PBS. The results indicated that the DNA vaccine encoding SAG5A significantly induced immune responses and enhanced protection against cysts of PRU strain, especially with the help of peptide.