IFNβ-ACE2 had potentiated antiviral activity compared to IFN-β and/or sACE2 in a non-washed in vitro infection system (Figure 5). The rationale for a ‘virus-washed’ system (Figure 3 and Figure 4) was to assess the antiviral action of virion surface-bound IFNβ-ACE2 and sACE2. Here, ACE2 is linked to infection.