We have previously demonstrated the survival time of mice challenge with T.gondii RH strain was prolonged by immunizing the mice with an eukaryotic vector expressing the protein ROP16 of T.gondii.We are now looking for ways to improve the vaccination strategy and enhance protection.In the study,we established a novel recombinant virus canine adenovirus type 2 expressing ROP16(CAV-2-ROP16)of T.gondii,and determined the foreign ROP16 expressed in MDCK cells by western blot(WB)and northern blot assays.The results indicated this vaccination elicited significant humoral and cellular immune responses,including ROP16-stimulated lymphoproliferation(P < 0.05).Compared to controls,the CAV-2-ROP16 immunized mice had high production of IFN-γ,IL-2 and IL-12(P < 0.05),with a predominance of IgG2a production,except for IL-10(P > 0.05),indicating that a Th1-predominant response was established.The cell-mediated cytotoxic activity with frequencies of IFN-γ and TNF-α parameters was significantly augmented in both CD4+ and CD8+ T cell compartments in the mice inoculated with CAV-2-ROP16(P <0.05),compared to three control groups.Moreover,when immunized mice were challenged with the RH strain of T.gondii,they displayed a significantly increased survival rate(25%)compared with control mice which all died within 7 days(P < 0.05).Collectively,these data indicate that recombinant virus CAV-2-ROP16 can enhance the ROP16-specific humoral and cellular immune responses,and,in particular,could effectively protect the mice against acute toxoplasmosis.It wll be useful for future clinical studies.