The maternal environment is rich in SARS-related receptors which could
be protective for the fetus
Abstract
Background: While risk of infection with SARS-CoV-2 is low to pregnant
women and the fetus, there is increased risk of preterm birth and
admission into ICU. The fetus is relatively protected against infection,
with cases of vertical transmission being rare. Various receptors and
accessory molecules which are known to regulate SARS-CoV-2 viral entry
into host cells have soluble versions which could act as decoy traps.
Following on from our previous findings regarding the abundance of some
of these molecules in breast milk and amniotic fluid, we show the
maternal-fetal interface is also rich in these molecules and how
systemically they can be differentially expressed between males,
non-pregnant females, pregnant females, and neonates. Methods: Archived
placental samples from before the pandemic, and blood from participants
in late 2020 who had not tested positive for COVID-19 were analysed for
the presence of receptors by ELISA, immunohistochemistry, immunoblotting
and flow cytometry. Results: We have confirmed that the placenta and
membranes are particularly rich in CD26 and CD147 and gone on to
consider if it is possible that shedding of these molecules into the
maternal and fetal circulation occurs. However, except for sCD147 in
umbilical cord plasma compared to all groups and sNRP-1 in pregnant
women in comparison to men and neonates, the expression of soluble forms
of these molecules is primarily consistent between the groups studied
here. Conclusion: The maternal-fetal interface has potential mechanisms
to protect the fetus from contracting SARS-CoV-2 by being rich with
soluble versions of receptors involved in host cell entry of the virus,
thereby limiting infection of host cells.