Vaccination with recombinant adenovirus expressing multi-stage antigens of Toxoplasma gondii by the mucosal route induces higher systemic cellular and local mucosal immune responses than with other vaccination routes

Wang, Ting; Yin, Huiquan; Li, Yan; Zhao, Lingxiao; Sun, Xiahui; Cong, Hua

In our study, a highly virulent RH strain and a mild virulent PRU strain of T. gondii were used for the challenge study. With the RH strain, it is easy to induce acute infection in mice through intraperitoneal injection with tachyzoites. The PRU strain is more likely to induce chronic infection in mice following intragastric administration with cysts [36] . In order to simulate acute and chronic infection in the host, mice were infected with the RH strain and PRU strain by different challenge routes. When challenged with lethal doses of T. gondii (1 · 10 3 ), all five groups immunized with Ad-UMAS had a prolonged survival time as compared with control mice. In particular, mice immunized intranasally and intraorally showed higher survival rates than with the other immunization routes. Since protection via vaccination was not 100% because the strain of the parasite has high mortality and the dose of RH parasites for immunized mice was larger, the optimal challenge dose should be determined in the future. Furthermore, the higher mucosal immune responses that were induced by intraoral and intranasal vaccination of Ad-UMAS may explain the significant reduction in the cyst burden in the mice immunized with Ad-UMAS intraorally and intranasally, which exhibited reductions of 75.3% and 78.6% of brain cysts, respectively.