Targeting Retroviral Vectors to Vascular Lesions by Genetic Engineering of the MoMLV gp70 Envelope Protein

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Abstract
Targeted gene delivery to vascular lesions is a major challenge in the development of gene therapy protocols for cardiovascular diseases. One approach would be to enable retroviral vectors to accumulate at sites of vascular injury and enhance local vector concentration. An early step in wound repair is the adhesion of platelets to collagen exposed from damaged vasculature. Hence, the Moloney murine leukemia virus (MoMLV) envelope (env) protein was engineered to incorporate a high-affinity collagen-binding domain derived from von Willebrand clotting factor, and expressed in Escherichia coli and in mammalian cells. The chimeric env protein bound tightly to collagen, and virions bearing this collagen-binding env protein exhibited viral titers approaching those of virions expressing wild-type (WT) env protein. The chimeric virions were concentrated on collagen matrices, and they retained their infectivity under conditions in which virions bearing WT env protein were washed away. Targeted delivery of the chimeric env protein to injured mouse aorta and selective binding of the collagen-targeted virions to injured rabbit artery were observed. In comparative studies, vascular smooth muscle cell transduction was demonstrated in catheter-injured carotid arteries following infusion of collagen-targeted virions but not of virions bearing WT env protein. Taken together, these observations demonstrate the ability of collagen-targeted virions to localize gene delivery to sites of vascular injury. Targeted gene delivery to vascular lesions is a major goal in the development of gene therapy protocols for cardiovascular diseases. To this end, the Moloney murine leukemia virus (MoMLV) env protein was engineered to incorporate a high-affinity collagen-binding domain derived from von Willebrand factor and thus to increase the effective local concentration of the retrovirus. The chimeric virions bound tightly to collagen matrices and retained their infectivity. Targeted delivery of the chimeric env protein to injured mouse aorta and selective binding of the collagen-targeted virions to injured rabbit artery were observed. Furthermore, transduction of injured rat carotid arteries was demonstrated in vivo following local infusion of collagen-targeted virions but not of virions bearing WT env protein. These findings have clinical applicability for in vivo targeting of retroviral vectors to injured vasculature.