Using decoy proteins to treat viral illness As a non-biologist, my understanding is SARS-CoV-2 uses it spike protein to latch on to the ACE2 receptor on cells in order to inject its genetic material into the cell. Questions: 1. What would happen if you flooded a person with exogenous ACE2 proteins? 2. Would the virus attach to these decoy proteins and thereby save cells from being infected? 3. Would the injected proteins cause unwanted side effects? 4. Has this approach to treating viral infections been tried before? Reference: <

This is indeed a reputable strategy (#1,2,4) for rapid response to novel pathogens. See < and the open access article it cites <

In the case of coronavirus, however, there is an issue (your #3) in that ACE2 is an enzyme that catalyzes the breakdown of a circulating hormone, angiotensin II, which is responsible for maintaining high (or normal) blood pressure. So the "bait" used would have to be at least somewhat altered from this. You would probably have to take into account how it affected other protein interactions such as with integrin beta 1 ... (see articles like < ) to avoid getting caught up in speculation, it makes sense that a neutralizing protein might be made from part of ACE2 just as a neutralizing monoclonal antibody could be made, but you still have to have something specific before you can test for safety and efficacy.