Impact of Fc engineering on the transcriptional profile of monocytes and interstitial macrophages in the lungs of Hu-FcgR Tg mice after MA30 infection

As the SARS-CoV-2 pandemic progressed, many monoclonal antibodies (mAbs) that neutralized infection against initial strains lost potency against later variants due to accumulation of mutations in the spike protein. Nonetheless, some mAbs, including S309, the parent of the therapeutically used sotrovimab, remained protective in animals against Omicron variants despite reduced neutralizing potential, with Fc-mediated effector functions likely sustaining inhibitory activity. Here, we identify Fc variants of S309 that confer enhanced protection against SARS-CoV-2 infection in a humanized Fcg receptor transgenic (Hu-FcgR 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 FcgRs 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-FcgR Tg mice challenged with SARS-CoV-2 strains compared to the parental S309 mAb or a variant (S309-GRLR) lacking Fc effector functions. 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 FcgRs can strengthen effector functions, shape myeloid transcriptional profiles, and enhance protection against SARS-CoV-2 infection in vivo.