Immunological and pathological changes in the placenta during infection with Listeria monocytogenes in pregnant guinea pigs

Exposure to Listeria monocytogenes during pregnancy can result in spontaneous abortion and stillbirths; however, the mechanisms are unknown. Our objective was to determine the effects of infection on specific inflammatory and anti-inflammatory cytokine mRNA expression and apoptosis in the placenta after infection with L. monocytogenes. Pregnant guinea pigs were treated on gestation day (gd) 35 with 108 colony forming units L. monocytogenes and sacrificed on gd 37, 41, 44, or 55. At gd 41, IFN-γ and IL-2 mRNA expression was significantly decreased in placentas from treated dams (0.0012-fold and 0.131-fold, respectively). At gd 55, TNF-α mRNA expression was significantly decreased (0.19-fold), while IFN-γ mRNA expression was significantly increased (32-fold), and apoptosis was detected in 100% of placentas from treated dams. In conclusion, inflammatory cytokine mRNA expression is altered and apoptosis is increased in the placenta after treatment with L. monocytogenes, and these changes may contribute to fetal death.