Potent antigen-specific immunity to Toxoplasma gondii in adjuvant-free vaccination system using Rop2-Leishmania infantum Hsp83 fusion protein

The results of this study describe the immunostimulatory properties of Leishmania infantum Hsp83 (83) to elicit humoral and cellular response against the Toxoplasma gondii Rop2 protein in an adjuvant-free vaccination system. The analysis was performed by immunizing three different mice strains (BALB/c, C57BL/6 and C3H). Mice immunized with fusion Rop2-83 elicited a stronger humoral and cellular response in comparison to mice immunized with Rop2 alone, or a mix of LiHsp83 and Rop2. The fusion protein induced a Th1 type response, with predominance of specific IgG2a/IgG2c isotype and IFN-γ secretions, whereas Rop2 alone or mixed with LiHsp83 produced a Th1/Th2 mixed response. Vaccination with fusion protein conferred a remarkable resistance against oral infection with ME49 cysts in C57BL/6 and C3H mice, in comparison to mice immunized with Rop2 alone or the protein mixture. Following lethal challenge, a significant survival rate was observed in Rop2-83 immunized Balb/c and C57BL/6 mice in comparison to control groups.