Evaluation of protective effect of multi-epitope DNA vaccine encoding six antigen segments of Toxoplasma gondii in mice.

To investigate the vaccine potential of multi-epitope vaccines against toxoplasmosis, a multi-epitope DNA vaccine, eukaryotic plasmid pcDNA3.1/T-ME expressing six antigen segments (SAG1(238-256), SAG1(281-320), GRA1(170-193), GRA4(331-345), GRA4(229-245), and GRA2(171-185)) of Toxoplasma gondii was constructed. We investigated the efficacy of pcDNA3.1/T-ME with or without co-administration of a CpG-oligodeoxynucleotide (CpG-ODN) as an adjuvant to protect mice (BALB/c and C57BL/6) against toxoplasmosis. High survival rates were observed in mice immunized with pcDNA3.1/T-ME when challenged with T. gondii RH strain. Lymphocyte proliferation assays, cytokine, and antibody determinations show that mice immunized with pcDNA3.1/T-ME produced stronger humoral and Th1-type cellular immune responses compared to untreated mice or those immunized with empty plasmids. However, co-immunization with CpG-ODN resulted in impaired immune responses. Our data demonstrates that multi-epitope DNA vaccination is a potential strategy for the control of toxoplasmosis and paves the way for further investigations into producing a multi-epitope anti-T. gondii DNA vaccine.