Does the human placenta express the canonical cell entry mediators for SARS-CoV-2?

The pandemic of coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has affected over 3.8 million people, including pregnant women. To date, no consistent evidence of vertical transmission for SARS-CoV-2 exists. This new coronavirus canonically utilizes the angiotensin-converting enzyme 2 (ACE2) receptor and the serine protease TMPRSS2 for cell entry. Herein, building upon our previous single cell study of the placenta (Pique-Regi, 2019), another study, and new single-cell/nuclei RNA-sequencing data, we investigated the expression of ACE2 and TMPRSS2 throughout pregnancy as well as in third-trimester chorioamniotic membranes. We report that co-transcription of ACE2 and TMPRSS2 is negligible, thus not a likely path of vertical transmission for SARS-CoV-2 at any stage of pregnancy. In contrast, receptors for Zika virus and cytomegalovirus which cause congenital infections are highly expressed by placental cell types. These data suggest that SARS-CoV-2 is unlikely to infect the human placenta through the canonical cell entry mediators; yet, other interacting proteins could still play a role in the viral infection.