Dendritic Cell‐Mediated Cross‐Priming by a Bispecific Neutralizing Antibody Boosts Cytotoxic T Cell Responses and Protects Mice against SARS‐CoV‐2

Abstract

Administration of neutralizing antibodies (nAbs) has proved to be effective by providing immediate protection against SARS‐CoV‐2. However, dual strategies combining virus neutralization and immune response stimulation to enhance specific cytotoxic T cell responses, such as dendritic cell (DC) cross‐priming, represent a promising field but have not yet been explored. Here, a broadly nAb, TNT, are first generated by grafting an anti‐RBD biparatopic tandem nanobody onto a trimerbody scaffold. Cryo‐EM data show that the TNT structure allows simultaneous binding to all six RBD epitopes, demonstrating a high‐avidity neutralizing interaction. Then, by C‐terminal fusion of an anti‐DNGR‐1 scFv to TNT, the bispecific trimerbody TNTDNGR‐1 is generated to target neutralized virions to type 1 conventional DCs (cDC1s) and promote T cell cross‐priming. Therapeutic administration of TNTDNGR‐1, but not TNT, protects K18‐hACE2 mice from a lethal SARS‐CoV‐2 infection, boosting virus‐specific humoral responses and CD8+ T cell responses. These results further strengthen the central role of interactions with immune cells in the virus‐neutralizing antibody activity and demonstrate the therapeutic potential of the Fc‐free strategy that can be used advantageously to provide both immediate and long‐term protection against SARS‐CoV‐2 and other viral infections.

Therapeutic nanobodies against SARS-CoV-2 and other pathogenic human coronaviruses

“…For example, TN T DNGR-1, which was generated by fusing a SARS-CoV-2 RBD-specific biparatopic nanobody (VHH)-based trimerbody (TN T ) with a DNGR-1-specific scFV, provides K18-hACE2 mice with therapeutic protection from challenge with lethal SARS-CoV-2 (B.1. strain), with a reduced viral load in the lungs [106]. SARS-CoV-2 RBD-targeting nanobodies also provide effective protection after inhalation or intranasal delivery [94,104,107,108].…”