Fc-engineered antibodies enhance protection against SARS-CoV-2 lung infection and inflammation

As the SARS-CoV-2 pandemic progressed, many monoclonal antibodies (mAbs) that neutralized infection against initial strains lost potency against later variants due to the accumulation of mutations in the spike protein. Nonetheless, some mAbs, including the parent of the therapeutically used sotrovimab, S309, remained protective in animals against Omicron variants despite reduced neutralizing potential, with inhibitory activity likely sustained by Fc-mediated effector functions. Here, we identify Fc variants of S309 that confer enhanced protection against SARS-CoV-2 infection in a humanized Fcγ receptor transgenic (Hu-FcγR Tg) mouse model of infection. Versions of S309 that are afucosylated (AFUC) and contain a G236A (GA) mutation in the Fc region showed increased binding to FcγRs IIA, IIIA, and IIIB and enhanced phagocytic activity in cell culture-based assays. Treatment with S309-GA-AFUC resulted in less viral burden, inflammation, and pulmonary ventilatory dysfunction in the lungs of Hu-FcγR Tg mice challenged with SARS-CoV-2 strains compared to the parental S309 mAb or a variant lacking Fc effector functions (S309-GRLR). The enhanced protection in the lung conferred by S309-GA-AFUC required trafficking of CCR2-expressing monocytes to reduce SARS-CoV-2 viral burden and lung injury. Flow cytometry and RNA sequencing analyses showed that compared to the parental S309 mAb, S309-GA-AFUC treatment reduced the inflammatory state and induced a reparative transcriptional signature in monocytes and interstitial macrophages. Overall, our findings demonstrate that Fc engineering to increase antibody binding to activating FcγRs can strengthen effector functions, shape myeloid transcriptional profiles, and enhance protection against SARS-CoV-2 infection in vivo.

Although therapeutic antibodies had success in protecting vulnerable individuals from severe COVID-19 during the early stages of the pandemic, many lost effectiveness as SARS-CoV-2 accumulated mutations that compromised neutralizing activity. Our experiments show that antibody protection against SARS-CoV-2 strains can be enhanced by genetically engineering the Fc region or altering its N-linked glycosylation to improve interactions with FcγRs on host immune cells. Modified versions of S309, the parent of the clinically used sotrovimab antibody, more effectively reduce viral burden and inflammation in the lung and shape protective transcriptional responses, which, together, result in improved lung ventilatory function and outcome after SARS-CoV-2 infection. Thus, antibody engineering can serve as a strategy to enhance therapeutic activity against rapidly evolving viruses with the potential to escape neutralization.