Recombinant canine adenovirus type-2 expressing TgROP16 provides partial protection against acute Toxoplasma gondii infection in mice.

We previously demonstrated that the survival time of BALB/c mice challenged with Toxoplasma gondii RH strain was prolonged by immunising the mice with a eukaryotic vector expressing the protein ROP16 of T. gondii . Building upon previous findings, we are exploring improved vaccination strategies to enhance protection. In this work, a novel recombinant canine adenovirus type 2 expressing ROP16 (CAV-2-ROP16) of T. gondii was constructed and identified to express ROP16 in Madin-Darby canine kidney cells (MDCK) cells by western blot (WB) and indirect immunofluorescence (IFA) assays. Intramuscular immunisation of BALB/c mice with CAV-2-ROP16 was performed to evaluate the humoral and cellular immune responses. This vaccination triggered significant humoral and cellular responses, including ROP16-stimulated lymphoproliferation ( P < 0.05). Compared to control groups, the CAV-2-ROP16 immunised mice had high production of IFN-γ, IL-2 and IL-12 ( P < 0.05), with a predominance of IgG2a production, but not IL-10 ( P > 0.05), revealing that a predominant Th1-type response had developed. The cell-mediated cytotoxic activity with high levels of IFN-γ and TNF-α was significantly increased in both CD4 + and CD8 + T-cell compartments in the mice immunised with CAV-2-ROP16 ( P < 0.05), compared to three control groups. In addition, when immunised mice were challenged with the RH strain of T. gondii , they showed a significantly increased survival rate (25%) 80 days post infection compared with control mice that all died within seven days ( P < 0.05). The 25% protection rate elicited by the recombinant virus CAV-2-ROP16 has not been achieved in the field of anti- T. gondii vaccination until now. Our work presents the successful use of recombinant virus CAV-2-ROP16 in vaccination protocols to protect against intraperitoneal challenge with the virulent RH strain of T. gondii . This system was shown to be extremely efficient in eliciting humoral and cellular immune responses that led to a significant improvement in survival time in mice. [ABSTRACT FROM AUTHOR]