Leveraging mouse genetics to generate heavy-chain only antibodies for therapeutic application

Abstract Conventional antibodies (Abs) consist of two heavy and two light immunoglobulin chains, while heavy-chain only antibodies (HCAbs), like those found in camelid and shark species, are unique because they lack a light chain binding partner. The unique structure of these HCAbs impart advantageous properties to these smaller Abs, including greater accessibility to their target antigens, higher hydrophilicity, and greater conformational stability under environmental stresses. We have generated a mouse model, the IgG3dCH1 strain, that can produce HCAbs from the endogenous murine heavy chain locus. We have shown that these mice undergo efficient B cell development in the bone marrow, and generate a diverse repertoire of B cells that populate all peripheral immune compartments. While single-cell sequencing analysis of B cells revealed some biases in VH and JH usage, it also highlighted the tremendous diversity of rearrangements that give rise to B cells bearing these single chain antibodies. We’ve been able to show that upon immunization, IgG3dCH1 animals are protected from lethal bacterial challenge with a pathogenic strain of Enterobacter hormaechei and generate pathogen specific IgG. Further, immunization with SARS-CoV2 stabilized prefusion spike protein elicited HCAbs with a KD in the nM range, measured via bio-layer interferometry. These data support this mouse being utilized as a platform for the generation of pathogen-specific HCAbs that can be further engineered for testing and application for translational outcomes. Supported by grants from NIH (T32 AI007180, R43 AI136141).