Submitted to: Parasite Immunology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/15/2003
Publication Date: 7/7/2003
Citation: Almeria, S., Demarez, T., Dawson, H.D., Araujo, R., Dubey, J.P., Gasbarre, L.C. 2003. Cytokine gene expression in dams and fetuses after experimental neospora caninum infection of Heifers at mid gestation. Parasite Immunology. vol. 25, pp. 383-92. Interpretive Summary: Abortion and stillbirth due to Neospora caninum, especially in dairy cattle, are a significant cause of economic loss in the dairy industry. The major source of N caninum infection in dairy farms is transplacental transmission from naturally infected dams to the fetus during pregnancy. This study was performed to understand the immune response that takes place in dams and fetuses after experimental infection of pregnant heifers. Changes in immune cell populations were analyzed by flow cytometry and cytokine gene expression was analyzed by real time RT-PCR. Infection with N. caninum during pregnancy induced significant immune responses in both dams and fetuses. Infected dams showed significantly decreased T cells levels in peripheral blood, but levels of T cells increased in internal organs from both dams and fetuses. Cytokine gene expression analyzed by real time RT-PCR showed a predominant Thl cytokine expression in infected animals, however, Th2 cytokines, especially IL-l0, were also increased in N. caninum infected animals. This cytokine expression could have a role in the transplacental transmission of the parasite and/or mediate tissue damage.
Technical Abstract: Neospora caninum is a major cause of abortion in cattle. An essential role for Thl cytokines, such as IFN-g and IL-12 in protective immunity against N. caninum 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 Neospora caninum tachyzoites was compared to immune responses in uninfected pregnant heifers. Animals were euthanized 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 fetuses. Infected dams showed significantly compartmentalized changes in lymphocyte subpopulations compared to uninfected pregnant animals, and increased levels of T lymphocytes were observed in the infected fetuses. Cytokine gene expression analyzed by real time RT-PCR showed increased expression of both Thl 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.