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 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.