Maternal and fetal immune response patterns in heifers experimentally infected with Neospora caninum in the second trimester of pregnancy - A descriptive study

Fetal and maternal immune responses 3, 6 and 9 weeks post infection (wpi) were investigated in cows experimentally infected with Neospora caninum on day 110 of gestation. Descriptive analysis showed that the fetuses had lower percentages of spleen T cell subpopulations (CD3+, CD4+ and CD8+) at 6 wpi compared to 3 wpi and/or 9 wpi, with the lowest percentages observed in a dead fetus found upon euthanasia at that time. Increased expression of most cytokines over levels recorded at 3 and 9 wpi were found in fetuses that were alive at 6 wpi. Up-regulated Th1, Th2 and Treg expression was also observed at 6 wpi in the spleen and in the lymph nodes draining the placenta of the cows. At the placental level, while most cytokines were down-regulated from 6 wpi, up-regulation of IL-4 expression was observed at 6 wpi in the caruncle. Our results suggest that the immune response at 6 wpi was crucial for fetal survival in this model of bovine neosporosis.