General strategy for broadening adenovirus tropism

In spite of its broad host range, adenovirus type 5 (Ad5) transduces a number of clinically relevant tissues and cell types inefficiently, mostly because of low expression of the coxsackievirus-adenovirus receptor (CAR). To improve gene transfer to such cells, we modified the Ads fiber knob to recognize novel receptors. We expressed a functional Ads fiber knob domain on the capsid of phage X and employed this display system to construct a large collection of ligands in the HI loop of the Ads knob. Panning this library on the CAR-negative mouse fibroblast cell line NIH 3T3 resulted in the identification of three clones with increased binding to these cells. Adenoviruses incorporating these ligands in the fiber gene transduced NIH 3T3 cells 2 or 3 orders of magnitude better than the parent vector. The same nonnative tropism was revealed in other cell types, independently of CAR expression. These Ads derivatives proved capable of transducing mouse and human primary immature dendritic cells with up to 100-fold increased efficiency.