| Summary: | <i>Neospora caninum</i> is an obligate intracellular protozoan responsible for abortion and stillbirths in cattle. We previously developed a mucosal vaccination approach using <i>N. caninum</i> membrane proteins and CpG adjuvant that conferred long-term protection against neosporosis in mice. Here, we have extended this approach by alternatively using the carbomer-based adjuvant Carbigen™ in the immunizing preparation. Immunized mice presented higher proportions and numbers of memory CD4<sup>+</sup> and CD8<sup>+</sup> T cells. Stimulation of spleen, lungs and liver leukocytes with parasite antigens induced a marked production of IFN-γ and IL-17A and, less markedly, IL-4. This balanced response was also evident in that both parasite-specific IgG1 and IgG2c were raised by immunization, together with specific intestinal IgA. Upon intraperitoneal infection with <i>N. caninum</i>, immunized mice presented lower parasitic burdens than sham-immunized controls. In the infected immunized mice, memory CD4<sup>+</sup> T cells predominantly expressed T-bet and RORγt, and CD8<sup>+</sup> T cells expressing T-bet were found increased. While spleen, lungs and liver leukocytes of both immunized and sham-immunized infected animals produced high amounts of IFN-γ, only the cells from immunized mice responded with high IL-17A production. Since in cattle both IFN-γ and IL-17A have been associated with protective mechanisms against <i>N. caninum</i> infection, the elicited cytokine profile obtained using Carbigen<sup>TM</sup> as adjuvant indicates that it could be worth exploring for bovine neosporosis vaccination.
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