Tumor necrosis factor-α in pregnant cattle after intravenous or subcutaneous vaccination with Brucella abortus strain RB51

Abstract

Objective-To determine the influence of brucellosis vaccination on tumor necrosis factor-α (TNF-α) concentrations in pregnant cattle and the possible role of the bovine placenta in TNF-α 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 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 pyrogen-free saline solution SC (n = 2). Blood samples were collected periodically for TNF-α assays. At necropsy, 8 to 12 weeks after vaccination, placental fluids and fetal blood were collected for TNF-α analysis and placental tissues were collected for immunohistochemical detection of TNF-α. Results-Radioimmunoassays indicated no increase in TNF- α concentration in blood from IV or SC vaccinated cattle, compared with controls. Similarly, TNF-α concentrations in amniotic 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-α revealed increased immunoreactivity within placental trophoblastic epithelial cells of SC and IV vaccinated cattle. Conclusions- SC vaccination for prevention of brucellosis, using recommended adult dosages, does not result in increase of TNF-α concentration in plasma, serum, or placental fluids; however, vaccination of pregnant cattle stimulates trophoblastic epithelial cells to express TNF-α, although the physiologic and quantitative importance of this expression remains unknown.