Caracterização de lesões e de biomarcadores da imunidade inata em placentas expostas ao SARS-CoV-2

Abstract

Knowledge of the consequences of infection caused by SARS-CoV-2, COVID-19, during pregnancy is relatively limited and there is an urgent need to better understand the various manifestations of this new disease throughout pregnancy, especially its impacts on the placenta, such as the persistence of SARS-CoV-2 and the inflammatory responses triggered in the placentas of mothers who had COVID-19 during pregnancy. To contribute to reducing these gaps in knowledge of placental pathology during COVID-19 infection, this study characterized the morphological lesions and the expression of innate immunity receptors RIG-1 and the NLRP3 inflammasome pathway in the placentas of pregnant women exposed and not exposed to SARS-CoV-2 during pregnancy. Placental samples from 31 pregnant women were included in the study, 15 exposed and diagnosed with mild COVID-19 and 16 unexposed, for histopathological and immunohistochemical analyses. The results demonstrated the absence of SARS-CoV-2 and the occurrence of degenerative changes, such as fibrin deposition and calcification, in all samples. Comparing the morphological characteristics of the placentas of pregnant women exposed versus not exposed to SARS-CoV-2, higher and statistically non-significant proportions of inflammatory lesions were observed, such as chorioamnionitis (26.67% versus 12.5%) and acute vasculitis (33.3% versus 12.5%), corroborating an inflammatory pattern (57.14% versus 42.85%). Regarding the immunohistochemical expression of innate immunity biomarkers, hyperexpression of RIG-1 and basal expression of NLRP3 and IFN-γ were observed in all compartments of the placenta, in addition to predominance of hyperexpression of the biomarkers Caspase-1 and IL-1β and basal expression of IL-18 in the trophoblast, indicating constitutive presence of RIG-1 and activation of Caspase-1 and IL-1β independent of the NLRP3 inflammasome. Together, the results demonstrate the non-persistence of SARS-CoV-2 in the placenta and the presence of higher relative proportions of inflammatory lesions not associated with the NLRP3 inflammasome.