Functional diversification of innate and inflammatory immune responses mediated by antibody fragment crystallizable activities against SARS-CoV-2.

Monoclonal antibodies (mAb) targeting the SARS-CoV-2 Spike (S) glycoprotein have been exploited for the treatment of severe COVID-19. In this study, we evaluated the immune-regulatory features of two neutralizing anti-S mAbs (nAbs), named J08 and F05, with wild-type (WT) conformation or silenced Fc functions. In the presence of D614G SARS-CoV-2, WT nAbs enhance intracellular viral uptake in immune cells and amplify antiviral type I Interferon and inflammatory cytokine and chemokine production without viral replication, promoting the differentiation of CD16+ inflammatory monocytes and innate/adaptive PD-L1+ and PD-L1+ CD80+ plasmacytoid Dendritic Cells. In spite of a reduced neutralizing property, WT J08 nAb still promotes the IL-6 production and differentiation of CD16+ monocytes once binding Omicron BA.1 variant. Fc-mediated regulation of antiviral and inflammatory responses, in the absence of viral replication, highlighted in this study, might positively tune immune response during SARS-CoV-2 infection and be exploited also in mAb-based therapeutic and prophylactic strategies against viral infections.