Factors Responsible for the Differential Growth of Brucella Abortus in Bovine Trophoblasts.

The interactions of bovine chorionic membrane explants (CAMs) as well as three different bovine trophoblastic cell lines with Brucella abortus were evaluated. The ability of B. abortus to infect and grow within the cells of these CAMs and within these cell lines was measured. In addition, prostanoid and hormone production by the trophoblastic cells after infection with B. abortus was measured. Internalization of B. abortus within the cells of CAMs derived from placentas from both 3-month-gravid cows and 7-month-gravid cows was similar. By 24 hours post-inoculation B. abortus replication in 7-months-derived CAMs was significantly greater than the replication occurring in 3-month-gravid cows derived CAMs. Three trophoblastic cell lines derived from bovine placentas of differing gestational stages were used to study the differential replication of B. abortus. The trophoblastic cell lines were derived from a 15-day-old bovine embryo, the placentomal tissue from a 5-month-old bovine placenta and from the extra-placentomal portion of the CAM for a 8-month-old bovine placenta. Brucella abortus rapidly replicate within the trophoblastic cell lines derived from 5 and 8-month-old-bovine placentas but grew slowly within trophoblastic cells derived from embryonic bovine placenta. Bovine trophoblastic cells synthesize a variety of biologically active compounds throughout gestation. The concentration of hormones and prostanoids produced by trophoblastic cells exposed to either B. abortus or to B. abortus endotoxins was measured and compared to the concentrations of these compounds produced by non-infected cells. Significant increases in the concentration of PGF$\sb{2\alpha},$ PGE$\sb2,$ estrogens and cortisol were observed in cells derived from 5 and 8 month gestational placentas, whereas, a significant increase was not observed in embryonic cells. These hormones and prostanoids were individually added to the standard tissue culture media to determine the effects of these compounds on B. abortus growth. Progesterone during the first 8 hours of the culture increased the replication rate of B. abortus in the two cell lines. Estrogens significantly increased the growth of B. abortus in these two lines at 16 and 24 hours of incubation. Prostanoids had no influence on B. abortus growth in all these cell lines