Gamma Interferon Production and Plasma Concentrations of Pregnancy‐Associated Glycoproteins 1 and 2 in Gestating Dairy Cows Naturally Infected With Neospora caninum

Contents Gamma interferon ( IFN ‐γ) production and cross‐breed pregnancy have been attributed a role in protecting dairy cows infected with N eospora caninum against abortion. Plasma levels of pregnancy‐associated glycoproteins‐1 ( PAG ‐1) are a marker of placental/foetal well‐being and of PAG ‐2 is an abortion risk indicator in chronically N . caninum ‐infected animals. The present study examines, in cross‐breed pregnancies, interactions between IFN ‐ γ production and levels of PAG ‐1 and PAG ‐2 in non‐aborting naturally N eospora ‐infected dairy cows. Data were obtained from 60 pregnant H olstein‐ F riesian cows: 44 N eospora ‐seropositive and 16 N eospora ‐seronegative; 12 became pregnant using H olstein‐ F riesian semen and 48 using L imousin semen. Blood samples were collected on Days 40, 90, 120, 150, 180 and 210 of gestation. Gamma interferon was only detected in the plasma of nine of the 44 N eospora ‐seropositive cows, all of them became pregnant using L imousin semen. Through GLM procedures, in cows inseminated with Limousin semen and N eospora ‐seropositive cows showing no IFN ‐ γ production, PAG ‐1 concentrations were high and increased throughout gestation compared to the levels detected in cows inseminated with H olstein‐ F riesian semen and N eospora ‐seropositive cows producing IFN ‐ γ , respectively. In N eospora ‐seronegative cows and in N eospora ‐seropositive cows showing no IFN ‐ γ production, significantly increased PAG ‐2 concentrations were observed on gestation Day 120. Our findings indicate that IFN ‐ γ production correlates negatively and the production of antibodies against N . caninum is uncorrelated with plasma PAG concentrations during gestation in Neospora ‐infected dairy cows. Accordingly, IFN ‐ γ production could be linked to the transplacental migration of tachyzoites, which may cause a reduction in PAG levels.