A recently determined X-ray crystal structure of a bovine antibody (BLV1H12) with an ultralong heavy chain complementarity determining region 3 (CDR3H) region revealed a unique scaffold that features a disulfide-bonded "knob" domain fused to a solvent exposed, antiparallel β-stranded "stalk". This unusual variable region motif provides a novel approach for generating chimeric antibodies with novel activities. Toward this end, human erythropoietin (hEPO) was substituted for the "knob" domain in this antibody to afford an antibody-hEPO (Ab-hEPO) fusion protein that efficiently expresses in mammalian cells. Ab-hEPO proliferated TF-1 cells with a potency comparable to that of hEPO (EC50 ~ 0.03 nM) and exhibits... More
A recently determined X-ray crystal structure of a bovine antibody (BLV1H12) with an ultralong heavy chain complementarity determining region 3 (CDR3H) region revealed a unique scaffold that features a disulfide-bonded "knob" domain fused to a solvent exposed, antiparallel β-stranded "stalk". This unusual variable region motif provides a novel approach for generating chimeric antibodies with novel activities. Toward this end, human erythropoietin (hEPO) was substituted for the "knob" domain in this antibody to afford an antibody-hEPO (Ab-hEPO) fusion protein that efficiently expresses in mammalian cells. Ab-hEPO proliferated TF-1 cells with a potency comparable to that of hEPO (EC50 ~ 0.03 nM) and exhibits a significantly extended plasma half-life (>6 days) in mice relative to hEPO (~4 hours). Mice treated with the Ab-hEPO fusion protein show sustained elevated hematocrit for more than two weeks. This work demonstrates the utility of BLV1H12 CDR3 fusions as a novel approach for generating potent polypeptides with enhanced pharmacological properties.
