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.