Anti-SARS-CoV-2 hyperimmune immunoglobulin provides potent and robust neutralization capacity and antibody-dependent cellular cytotoxicity and phagocytosis induction through N and S proteins

Abstract Background Although progressive COVID-19 vaccinations provide a significant reduction of infection rate in the short-to mid-term, effective COVID-19 treatments will continue to be an urgent need. Methods We have functionally characterized the anti-SARS-CoV-2 hyperimmune immunoglobulin (hIG) prepared from human COVID-19 convalescent plasma. SARS-CoV-2 virus neutralization was evaluated by four different methodologies (plaque reduction, virus induced cytotoxicity, TCID50 reduction and immunofluorimetry-based methodology) performed at four different laboratories and using four geographically different SARS-CoV-2 isolates (one each from USA and Italy; two from Spain). Two of the isolates contained the D614G mutation. Neutralization capacity against the original Wuhan SARS-CoV-2 straom and variants (D614G mutant, B.1.1.7, P.1 and B.1.351 variants) was evaluated using a pseudovirus platform expressing the corresponding spike (S) protein. The capacity to induce antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP) was also evaluated. Results All the SARS-CoV-2 isolates tested were effectively neutralized by hIG solutions. This was confirmed by all four methodologies showing potent neutralization capacity. Wild-type SARS-CoV-2 and variants were effectively neutralized as demonstrated using the pseudovirus platform. The hIG solutions had the capacity to induce ADCC and ADCP against SARS-CoV-2 N and S proteins but not the E protein. Under our experimental conditions, very low concentrations (25-100 µg IgG/mL) were required to induce both effects. Besides the S protein, we observed a clear and potent effect triggered by antibodies in the hIG solutions against the SARS-CoV-2 N protein. Conclusions These results show that, beyond neutralization, other IgG Fc-dependent pathways may play a role in the protection from and/or resolution of SARS-CoV-2 infection when using hIG COVID-19 products. This could be especially relevant for the treatment of more neutralization resistant SARS-CoV-2 variants of concern.