Conclusion
These results suggest that both AF and BM are rich in soluble forms of
at least some of the molecules that regulate SARS-CoV-2 host cell entry
and could help protect the fetus and neonate from infection by acting as
decoy receptors and contributing to innate immune protection in the
gastrointestinal and, in the case of AF, respiratory tracts (Figure 1C).
Such a mechanism might also be relevant for other viral infections.
Future work should focus on evaluating if AF and BM inhibit viral entry
into host cells and comparing the relative efficacy of different
isoforms. This could reveal a novel protective mechanism for the baby
against SARS-CoV-2 infection and/or severe disease and provide further
evidence for a protective role for breastfeeding.