gondii. In the present work, we constructed recombinant Influenza A viruses harboring a dicistronic neuraminidase segment encoding T. gondii tachizoyte surface antigen SAG2 under control of a duplicated internally located 3′ promoter. Recombinant FLU-SAG2 viruses were genetically stable and induced expression of SAG2 in cell culture as well as in lungs of infected mice. We also observed that FLU-SAG2 was immunogenic

and, when associated with recombinant adenoviruses expressing SAG2 in vaccination protocols, elicited humoral and cellular anti-SAG2 immune responses, conferring a high degree of protection against challenge infection screening assay with the P-Br strain of T. gondii. Previous studies demonstrated that sequence of vector administration has pivotal importance in induction of heterospecific immune response in heterologous vaccination protocols [13], [14], [47] and [50]. Indeed, Li and co-workers showed that mice primed with a recombinant influenza and boosted with recombinant

Vaccinia encoding CS antigen, were protected after challenge with Plasmodium. However, no protection was observed in mice primed with Vaccinia and boosted with influenza. According to the authors, the systemic boost with Vaccinia could induce CTL migration to the liver, where Plasmodium circumsporozoyte replication occurs, while the intranasal boost with influenza viruses Selleck PLX3397 would favor CTL migration to lungs [13]. Based on these previous observations, we have chosen to prime the animals with FLU-SAG2 and to boost with Ad-SAG2. We speculate that the influenza vector would elicit anti-SAG2 immune response mainly at the respiratory level, priming both B and T cells, whereas a boost with adenovirus would reinforce the response at systemic level. Indeed, detection of IFN-γ producing

T cells specific for SAG2 in spleen and protection after challenge infection were only demonstrated in mice that received Ad-SAG2 boost by subcutaneous route. Although we did not evaluate the cellular immune response in respiratory tract, we speculate that boosting by intranasal route could detour T lymphocytes to respiratory tract and to abrogate the systemic cellular immune response. In our experiments, mice primed through with FLU-SAG2 and boosted with recombinant Ad-SAG2 displayed significant reduction of parasite burden after challenge with the P-Br strain of T. gondii. On the other hand, mice vaccinated with a single dose of Ad-SAG2 showed parasite burden similar to that found in animals vaccinated with control vectors. These results support previous studies showing that often significant protection cannot be achieved after a single immunization [3] and [51]. In addition, our results showed that innate immune response triggered by influenza inoculation was not sufficient to explain protection observed after the boost with Ad-SAG2.