Cantón, G.J., Katzer, F., Maley, S.W., Bartley, P.M., Benavides, J., Palarea Albaladejo, J., Pang, Y.P., Smith, S., Rocchi, M.S., Buxton, D.A., Innes, E.A. and Chianini, F.
||Neospora caninum is recognized as a major cause of bovine abortion but its pathogenesis is not completely understood. Evidence of immune mediated placental pathology has been reported as being responsible for compromising pregnancy probably due to the adverse effect of an exacerbated Th1 cytokine production at the maternal-foetal interface. Different clinical outcomes are known to follow experimental infections at different stages of gestation, with foetal death being the most common finding during early gestation infections, and the birth of live congenitally infected calves upon infection at mid or late gestation. The aim of the current study was to characterize Th1 cytokine expression by the placenta from cattle experimentally inoculated with the tachyzoites of the Nc-1 strain during early, mid and late gestation. Moderate to severe infiltration of IL-12, IFN-γ and TNF-α expressing cells was observed in the placentas collected at early gestation and this infiltration was more pronounced in the samples collected from dams carrying non-viable foetuses, compared with the mothers carrying viable foetuses. Contrastingly, the infiltration of Th1 cytokine expressing-cells was milder following N. caninum infection at mid gestation and scarce during infection at late gestation. Scarce expression of IL-4 was observed in the placentas from N. caninum-challenged and negative control animals throughout gestation. The presence of a milder Th1 cytokine expression following Nc-1 infection during the second and third trimesters of gestation could partially explain the less severe clinical outcome observed when animals are infected at this gestational stage.