Genetic targeting of the mouse immunoglobulin locus to permit the expression of heavy-chain only antibodies against viral antigens

Abstract

Abstract Conventional antibodies are composed of two identical sets of heavy and light chains, forming a dimer. The CH1 domain of the antibody heavy chain is essential for the pairing of heavy and light chains. However, certain animals, such as camels and sharks, evolved to produce heavy-chain-only antibodies (HCAbs) by losing this crucial CH1 domain in some of their antibody heavy chain constant regions. These HCAbs boast unique physicochemical properties that confer significant advantages: their smaller size allows for improved access to target antigens, increased hydrophilicity, enhanced tissue penetration, and greater structural stability compared to standard antibodies. Our research has successfully established a mouse model that intrinsically produces HCAbs from the mouse's own immunoglobulin heavy chain locus. Our findings demonstrate that heavy-chain-only B cell receptors, once introduced, facilitate normal B cell development, promote germinal center formation, and enhance plasma cell differentiation relative to B cells producing conventional antibodies. These genetically modified mice were vaccinated with viral antigens, resulting in the production of HCAbs that specifically target the SARS-CoV-2 spike protein and the HIV-1 Env trimer. Through single-cell sequencing, we have identified unique nucleotide sequences of clonotypes; the HCAbs are being synthesized to assess their viral neutralization potential and antigen-binding affinity to highlight the efficacy of our model.