Hofbauer cells and COVID-19 in pregnancy: Molecular pathology analysis of villous macrophages, endothelial cells, and placental findings from 22 placentas infected by SARS-CoV-2 with and without fetal transmission

David A Schwartz, Marcella Baldewijns, Alexandra Benachi, Mattia Bugatti, Gaetano Bulfamante, Ke Cheng, Rebecca R J Collins, Larisa Debelenko, Danièle De Luca, Fabio Facchetti, Brendan Fitzgerald, Daniel Levitan, Rebecca L Linn, Lukas Marcelis, Denise Morotti, Raffaella Morotti, Luisa Patanè, Sophie Prevot, Bianca Pulinx, Ali G SaadSam Schoenmakers, David Strybol, Kristen Thomas, Delfina Tosi, Valentina Toto, Lotte E van der Meeren, Robert M Verdijk, Alexandre J Vivanti, Mehreen Zaigham

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Abstract

Context.-SARS-CoV-2 can undergo maternal-fetal transmission, heightening interest in the placental pathology findings from this infection. Transplacental SARS-CoV-2 transmission is typically accompanied by chronic histiocytic intervillositis together with necrosis and positivity of syncytiotrophoblast for SARS-CoV-2. Hofbauer cells are placental macrophages that have been involved in viral diseases, including HIV and Zika virus, but their involvement in SARS-CoV-2 is unknown. Objective.-To determine whether SARS-CoV-2 can extend beyond the syncytiotrophoblast to enter Hofbauer cells, endothelium, and other villous stromal cells in infected placentas of liveborn and stillborn infants. Design.-Case-based retrospective analysis by 29 perinatal and molecular pathology specialists of placental findings from a preselected cohort of 22 SARS-CoV-2-infected placentas delivered to pregnant women testing positive for SARS-CoV-2 from 7 countries. Molecular pathology methods were used to investigate viral involvement of Hofbauer cells, villous capillary endothelium, syncytiotrophoblast, and other fetal-derived cells. Results.-Chronic histiocytic intervillositis and trophoblast necrosis were present in all 22 placentas (100%). SARS-CoV-2 was identified in Hofbauer cells from 4 of 22 placentas (18.2%). Villous capillary endothelial staining was positive in 2 of 22 cases (9.1%), both of which also had viral positivity in Hofbauer cells. Syncytiotrophoblast staining occurred in 21 of 22 placentas (95.5%). Hofbauer cell hyperplasia was present in 3 of 22 placentas (13.6%). In the 7 cases having documented transplacental infection of the fetus, 2 (28.6%) occurred in placentas with Hofbauer cell staining positive for SARS-CoV-2. Conclusions.-SARS-CoV-2 can extend beyond the trophoblast into the villous stroma, involving Hofbauer cells and capillary endothelial cells, in a small number of infected placentas. Most cases of SARS-CoV-2 transplacental fetal infection occur without Hofbauer cell involvement.

Original languageEnglish
Pages (from-to)1328-1340
Number of pages13
JournalArchives of pathology & laboratory medicine
Volume145
Issue number11
Early online date23 Jul 2021
DOIs
Publication statusPublished - 1 Nov 2021

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