Engineering B cells to Express Fully Customizable Antibodies with Enhanced Fc Functions.

Genome editing within the constant region of the immunoglobulin Heavy chain locus () can reprogram B cells to express Heavy chain only antibodies (HCAbs) containing custom antigenrecognition domains. HCAb-engineered cells express both surface B cell receptor (BCR) and secreted antibody isoforms and respond to antigen. By selecting alternate editing sites within , we extended this approach to also allow customization of the constant (Fc) domain of the Heavy chain, producing HCAbs with enhanced effector functions or containing mutations to extend antibody half-life. We also introduced mutations to force obligate HCAb homodimers and prevent unwanted pairing with endogenous antibody chains. Finally, we showed that additional domains could be accommodated at the HCAb C-terminus and preferentially expressed in the secreted isoform. Together these data demonstrate the flexibility of the HCAb editing platform to express fully customized molecules that take advantage of the properties of B cells.