Choriodecidual Group B Streptococcal Inoculation Induces Fetal Lung Injury without Intra-Amniotic Infection and Preterm Labor in Macaca nemestrina

Background Early events leading to intrauterine infection and fetal lung injury remain poorly defined, but may hold the key to preventing neonatal and adult chronic lung disease. Our objective was to establish a nonhuman primate model of an early stage of chorioamnionitis in order to determine the time course and mechanisms of fetal lung injury in utero. Methodology/Principal Findings Ten chronically catheterized pregnant monkeys (Macaca nemestrina) at 118–125 days gestation (term = 172 days) received one of two treatments: 1) choriodecidual and intra-amniotic saline (n = 5), or 2) choriodecidual inoculation of Group B Streptococcus (GBS) 1×106 colony forming units (n = 5). Cesarean section was performed regardless of labor 4 days after GBS or 7 days after saline infusion to collect fetal and placental tissues. Only two GBS animals developed early labor with no cervical change in the remaining animals. Despite uterine quiescence in most cases, blinded review found histopathological evidence of fetal lung injury in four GBS animals characterized by intra-alveolar neutrophils and interstitial thickening, which was absent in controls. Significant elevations of cytokines in amniotic fluid (TNF-α, IL-8, IL-1β, IL-6) and fetal plasma (IL-8) were detected in GBS animals and correlated with lung injury (p