Artificial envelopment of nonenveloped viruses: enhancing adenovirus tumor targeting in vivo

Recombinant adenovirus (Ad) is a powerful tool in gene therapy. However, the ability to deliver Ad by systemic administration is limited due to rapid clearance from blood circulation, transfection of nontarget tissues, toxicity, and immunogenicity. To address these limitations, we developed an artificially enveloped Ad vector prepared by self-assembly of lipid bilayers around the Ad capsid. The physicochemical and structural features of the enveloped Ad vector can be altered according to the type of lipid used without the need for genetic modification or conjugation chemistry. Here we engineered 4 different types of artificially enveloped Ad using cationic, neutral, fusogenic, and PEGylated lipids to form the envelopes and obtained extended blood circulation times following i.v. administration and reduced vector immunogenicity. Moreover, the PEGylated lipid-enveloped Ad was capable of specifically delivering genes via the systemic circulation to solid tumors subcutaneously implanted in the absence of high levels of gene transfer to the liver and spleen. This provides the basis for the development of a novel vector platform for systemic delivery of Ad to disseminated targets. Furthermore, the artificial envelopment of Ad presented herein is an illustration of a general strategy to modulate the biological function of nonenveloped viruses and may have implications broader than gene therapy.