A mouse model platform for heavy-chain-only antibody production and insights into B cell development 3254

Abstract Description Conventional antibodies consist of paired heavy and light chains, with the CH1 domain on the heavy chain required for their interaction. In contrast, animals like camelids and sharks produce heavy-chain-only antibodies (HCAbs) by omitting the CH1 domain. These HCAbs exhibit unique properties: smaller size, improved target access, enhanced tissue penetration, and greater structural stability compared to conventional antibodies. We have established a mouse model that produces HCAbs from the endogenous immunoglobulin heavy chain locus, confirmed by serum protein analysis. Our findings demonstrate that HCAb-expressing B cells undergo robust development in the bone marrow, are recruited into germinal centers, undergo affinity maturation and show enhanced plasma cell differentiation. We have also generated a control model restricted to conventional IgG3 expression, which enables us to distinguish B cell characteristics specifically attributed to HCAb expression versus phenotypes that arise as a consequence of IgG3 isotype. Following immunization of HCAb mouse model with viral antigens, including SARS-CoV-2 spike protein and HIV-1 Env trimer, single-cell sequencing and BCR repertoire analysis enabled rapid identification and synthesis of monoclonal HCAbs from top expanded B cell clones. Our novel small-animal platform allows efficient generation of target-specific HCAbs, combining the advantages of in vivo affinity maturation with streamlined monoclonal antibody production. Funding Sources R44AI136141 Topic Categories Technological Innovations in Immunology (TECH)