Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/1998
Publication Date: N/A
Interpretive Summary: Brucellosis is an important disease of cattle resulting in the premature delivery of dead calves. Recently, a new vaccine, Brucella abortus strain RB51, was approved for use in cattle to prevent brucellosis. Strain RB51 is superior to the previous brucellosis vaccine (strain 19) as it allows the differentiation of vaccinated cattle from naturally infected cattle. As part of a study to determine the safety of strain RB51 in pregnant cattle, indicators of tissue inflammation or damage were measured. Pregnant cattle vaccinated with RB51 did not show elevations of these indicators in maternal blood, fetal blood, or placental fluids which were different than nonvaccinated cattle. Although indicators of inflammation were found in some cells of the placenta of vaccinated cows, no tissue damage was present. These studies further support the use of RB51 for vaccination of pregnant cattle and should be of interest to livestock producers, animal health officials, and other researchers. Furthermore, vaccination of calve and cows with RB51 will advance the goal of achieving a brucellosis-free country and increase the competitiveness of U.S. cattle in the world market.
Technical Abstract: TNF-alpha is a key cytokine in inflammatory processes and mediates many of the clinical signs associated with endotoxemia due to gram negative bacterial infection. In order to determine the influence of brucellosis vaccination on TNF-alpha levels in pregnant cattle and the possible role of the placenta in TNF-alpha production, pregnant cattle were vaccinated IV with Brucella abortus strain RB51 (n=10), SC with B. abortus strain RB51 (n=5), or SC with B. abortus strain 19 (n=5); controls received pyrogen free saline SC (n=2). Radioimmunoassays showed no elevations in TNF-alpha levels in serum or plasma from IV or SC vaccinated cattle that differed from controls (P>0.05). Similarly, TNF-alpha levels in amniotic and allantoic fluids from SC vaccinated cattle were not different from controls (P>0.05). Immunohistochemistry for TNF-alpha revealed increased immunoreactivity within trophoblastic epithelial cells in SC and IV vaccinated cattle. Immunoreactivity was most extensive in IV vaccinated cattle that developed vaccine induced placentitis. These studies indicate that SC vaccination for the prevention of brucellosis using recommended adult dosages does not result in elevations of TNF-alpha in plasma, serum, or placental fluids; however, vaccination of pregnant cattle does stimulate trophoblastic epithelial cells to express TNF-alpha even when placentitis is not histologically evident.