Biopanning of single-chain antibodies expressing phages reveals distinct expression patterns of angiogenic and arteriogenic vessels.

"Therapeutic angiogenesis" requires targeted delivery of growth factors for maximal benefit and limitation of potential hazards such as enhancement of tumor or plaque angiogenesis. Physiological distinctions between angiogenesis and collateral growth suggest the possibility of targeting selectively collateral endothelium. This article describes the generation of collateral-targeting single-chain antibodies (scFv). Membrane preparations of growing collateral arteries from rats were used to produce collateral-targeting antibodies (CTAs) via immunization of mice. ScFv were generated from CTA-producing hybridoma and cloned into the pV gene of M13 phages. Phages expressing collateral-targeting scFv (CT scFv) were selected via repeated exposure to activated collateral arteries followed by reamplification. CT scFv could specifically be amplified, selected, and sequenced. Phages expressing CT scFv bound selectively to proliferating collateral vessels as identified by positive Polycyclic Nuclear Antigen (PCNA) staining and homed specifically to collateral endothelium after in vivo injection but bound neither to control vessels nor to tumor vessels. This study reveals major differences between angiogenic and collateral endothelium and delivers a tool that will allow the stimulation of collateral growth without promoting tumor or plaque angiogenesis.