Human placental cells are resistant to SARS-CoV-2 infection and replication.

Background: Infection during pregnancy with SARS-CoV-2 can have a serious impact on both maternal and foetal health. Clinical studies have shown that SARS-CoV-2 transmission from the mother to the foetus typically does not occur. However, there is evidence that SARS-CoV-2 can infect the placenta Methods: By using publicly available single-cell RNA sequencing (scRNAseq) data sets and confocal microscopy we compared ACE2 transcript and protein expression across human first trimester and term placental cells. We also used Results: ACE2 transcripts are found in a range of placental cell types across gestation, including trophoblast. However, ACE2 protein expression does not significantly change across placental cell types from first trimester to term. We find that 0.5±0.15 % of term trophoblast cells can be infected with SARS-CoV-2 while primary placental fibroblasts and macrophages, and JEG-3, JAR and HUVEC cell lines are resistant to infection. Furthermore, primary trophoblast cells poorly support viral release while JEG-3 cells allow relatively high levels of viral release. Conclusions: The low level of viral release by primary placental cells provides insight into how the virus is impaired from crossing the placenta to the foetus.