7  Strategy for investigating allo/autoantibodies
We are convinced that this hypothesis could be easily explored by testing allo-antibodies to ACE-2, or to its complexes with SARS-CoV-2 S Protein or its cleaved subunits, S1, and eventually associated with S2 or nucleoprotein. ACE-2 is now available in the recombinant form, even if still very expensive, and recombinant SARS-CoV-2 proteins or peptide sequences, including S Protein and S1, are available from various suppliers. A capture ELISA, designed by coating recombinant ACE-2, or its complexes with S-Protein or its S1 subunit, or eventually the viral nucleoprotein, onto the plate could be designed for capturing possible antibodies present in Covid-19 patients, especially those with delayed severe complications. Binding of antibody to these components, in the presence or absence of ACE-2 must be compared. This approach can allow the measurement amount of the kinetic course of these antibodies during the pathological evolution, and eventually in patients following their recovery. If present, these antibodies are expected to be alloantibodies, as induced by the association of a viral protein with a body’s self-component. However, if immuno stimulation is first induced by neo-epitopes exposed on ACE-2 when complexed with S Protein or S1, the response could be autoimmune. Laboratory investigations can clarify these considerations.