Submitted to: European Cost
Publication Type: Abstract Only
Publication Acceptance Date: 1/10/2003
Publication Date: 6/15/2003
Citation: ALMERIA, S., DEMAREZ, T., DAWSON, H.D., ARAUJO, R., DUBEY, J.P., GASBARRE, L.C. EXPERIMENTAL INFECTION OF PREGNANT COWS WITH NEOSPORA CANINUM: IMMUNE RESPONSES IN DAM AND FETUS. EUROPEAN COST. p. 27, 2003.
Technical Abstract: The present study was performed to define the immune responses in dam and fetus after infection of pregnant cows with N. caninum. Four cows were infected early in the second trimester of pregnancy (110 days of gestation) intravenously with 107 cattle strain culture derived tachyzoites and three pregnant cows were kept as uninfected controls. Animals were euthanized at 3-4 weeks after infection (131-138 days of pregnancy). Fetal spinal chord and brain from fetuses of the infected cows were inoculated into IFN-g gene knock-out mice and mice were examined for the presence of parasites. Immune responses in lymphocyte populations from peripheral blood lymphocytes (PBLs) from the dams, and lymph nodes and spleen of both dams and fetuses were ascertained by flow cytometry and by real time PCR for cytokine message expression. Quantification of bovine cytokines was performed by real time PCR using bovine-specific TaqMan® probes for IL-10, IL-4, IFN-g, TNF-g and IL-12. No abortion was observed in any infected dam at the time of the killing, however, transplacental infection had already taken place and parasites were detected in tissues from at least 3 of 4 infected fetuses. Infection with N. caninum during pregnancy induced significant immune responses in both dams and their fetuses. After three weeks of infection, PBLs from infected animals showed significantly lower levels of CD3+, CD4+, CD8+ and IL-2R+ cells compared to uninfected dams, while significantly higher CD3+ and higher, although not statistically significant, CD4+, CD8+ and IL-2R+ cells were observed in mesenteric lymph nodes from infected dams compared to uninfected dams. In the fetuses although few immunocompetent lymphocytes were present, significantly higher levels of CD3+ cells were observed in the infected fetuses. Cytokine gene expression analyzed 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.