A bispecific monomeric nanobody induces spike trimer dimers and neutralizes SARS-CoV-2 in vivo

Hanke, Leo; Das, Hrishikesh; Sheward, Daniel J; Vidakovics, Laura Perez; Urgard, Egon; Moliner-Morro, Ainhoa; Kim, Changil; Karl, Vivien; Pankow, Alec; Smith, Natalie L; Porebski, Bartlomiej; Fernandez-Capetillo, Oscar; Sezgin, Erdinc; Pedersen, Gabriel K; Coquet, Jonathan M; Hällberg, B Martin; Murrell, Ben; McInerney, Gerald M

Antibodies binding to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike have therapeutic promise, but emerging variants show the potential for virus escape. This emphasizes the need for therapeutic molecules with distinct and novel neutralization mechanisms. Here we isolated a nanobody that interacts simultaneously with two RBDs from different spike trimers of SARS-CoV-2, rapidly inducing the formation of spike trimer-dimers leading to the loss of their ability to attach to the host cell receptor, ACE2. We show that this nanobody potently neutralizes SARS-CoV-2, including the B.1.351 variant, and cross-neutralizes SARS-CoV. Furthermore, we demonstrate the therapeutic potential of the nanobody against SARS-CoV-2 and the B.1.351 variant in a human ACE2 transgenic mouse model. This naturally elicited bispecific monomeric nanobody establishes a novel strategy for potent inactivation of viral antigens and represents a promising antiviral against emerging SARS-CoV-2 variants.