TUMOR-NECROSIS-FACTOR-ALPHA IN PREGNANT CATTLE AFTER INTRAVENOUS OR SUBCUTANEOUS VACCINATION WITH BRUCELLA-ABORTUS STRAIN RB51

Objective-To determine the influence of brucellosis vaccination on tum or necrosis factor-alpha (TNF-alpha) concentrations in pregnant cattle and the possible role of the bovine placenta in TNF-alpha production. Animals-Foiled Hereford heifers obtained from a nonvaccinated, brucel losis-free herd and bred at 16 to 27 months at age. All cattle were se ronegative for Brucella abortus by results of the standard tube agglut ination test. Procedure-At 6 months' gestation, cattle were vaccinated IV with B abortus strain RB51 (n = 10), SC with B abortus strain RB51 (n = 5), or SC with B abortus strain 19 (n = 5); controls received py rogen-free saline solution SC (n = 2). Blood samples were collected pe riodically for TNF-alpha assays. At necropsy, 8 to 12 weeks after vacc ination, 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 increa se in TNF-alpha concentration in blood from IV or SC vaccinated cattle , compared with controls. Similarly, TNF-alpha concentrations in amnio tic and allantoic fluids from SC vaccinated cattle were not different from values for controls. Although only IV vaccinated cattle developed placentitis, immunohistochemical analysis for TNF-alpha revealed incr eased immunoreactivity within placental trophoblastic epithelial cells of SC and IV vaccinated cattle. Conclusions-SC vaccination for preven tion 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 trophoblast ic epithelial cells to express TNF-alpha, although the physiologic and quantitative importance of this expression remains unknown.