Cytokine gene expression in dams and foetuses after experimental Neospora caninum infection of heifers at 110 days of gestation.

Neospora caninum is a major cause of abortion in cattle. An essential role for Th1 cytokines, such as IFN-gamma and IL-12 in protective immunity against N. caninum in murine models has been indicated. However, little is known about immunity to Neospora in pregnant cattle where a considerable level of immunomodulation may exist. In this study, the immune response of heifers infected early in the second trimester of pregnancy by intravenous inoculation of N. caninum tachyzoites was compared with immune responses in uninfected pregnant heifers. Animals were killed 3 weeks after infection. No abortion was observed in any infected dam, however, transplacental infection was shown to have already taken place. Infection with N. caninum during pregnancy induced significant immune responses in both dams and their foetuses. Infected dams showed significant changes in lymphocyte subpopulations compared with uninfected pregnant animals and these changes were compartmentalized. Increased levels of T lymphocytes were observed in the infected foetuses. Cytokine gene expression analysed by real time RT-PCR showed increased expression of both Th1 and Th2 cytokines in N. caninum infected animals. This cytokine expression could have a role in the transplacental transmission of the parasite and/or mediate tissue damage.