Objective: To determine the influence of brucellosis vaccination on tumor necrosis factor-alpha (TNF-alpha) concentrations in pregnant cattle and the possible role of the bovine placenta in TNF-alpha production.
Animals: Polled Hereford heifers obtained from a nonvaccinated, brucellosis-free herd and bred at 16 to 27 months at age. All cattle were seronegative for Brucella abortus by results of the standard tube agglutination test.
Procedure: At 6 months' gestation, cattle were vaccinated i.v. with B abortus strain RB51 (n = 10), s.c. with B abortus strain RB51 (n = 5), or s.c. with B abortus strain 19 (n = 5); controls received pyrogen-free saline solution s.c. (n = 2). Blood samples were collected periodically for TNF-alpha assays. At necropsy, 8 to 12 weeks after vaccination, placental fluids and fetal blood were collected for TNF-alpha analysis and placental tissues were collected for immunohistochemical detection of TNF-alpha.
Results: Radioimmunoassays indicated no increase in TNF-alpha concentration in blood from i.v. or s.c. vaccinated cattle, compared with controls. Similarly, TNF-alpha concentrations in amniotic and allantoic fluids from s.c. vaccinated cattle were not different from values for controls. Although only i.v. vaccinated cattle developed placentitis, immunohistochemical analysis for TNF-alpha revealed increased immunoreactivity within placental trophoblastic epithelial cells of s.c. and i.v. vaccinated cattle.
Conclusions: s.c. vaccination for prevention of brucellosis, using recommended adult dosages, does not result in increase of TNF-alpha concentration in plasma, serum, or placental fluids; however, vaccination of pregnant cattle stimulates trophoblastic epithelial cells to express TNF-alpha, although the physiologic and quantitative importance of this expression remains unknown.