Reducing the native tropism of adenovirus vectors requires removal of bothCAR and integrin interactions

The development of tissue-selective virus-based vectors requires a better u nderstanding of the role of receptors in gene transfer in vivo, both to rid the vectors of their native tropism and to introduce new specificity. CAR and alphav integrins have been identified as the primary cell surface compo nents that interact with adenovirus type 5 (Ad5)-based vectors during in vi tro transduction. We have constructed a set of four vectors, which individu ally retain the wild-type cell interactions, lack CAR binding, lack alphav integrin binding, or lack both CAR and alphav integrin binding. These vecto rs have been used to examine the roles of CAR and av integrin in determinin g the tropism of Ad vectors in a mouse model following intrajugular or intr amuscular injection. CAR was found to play a significant role in liver tran sduction. The absence of CAR binding alone, however, had little effect on t he low level of expression from Ad in other tissues. Binding of alphav inte grins appeared to have more influence than did binding of CAR in promoting the expression in these tissues and was also found to be important in liver transduction by Ad vectors. An effect of the penton base modification was a reduction in the number of vector genomes that could be detected in sever al tissues. In the liver, where CAR binding is important, combining defects in CAR and alphav integrin binding was essential to effectively reduce the high level of expression from Ad vectors. While there may be differences i n Ad vector tropism among species, our results indicate that both CAR and a v integrins can impact vector distribution in vivo. Disruption of both CAR and av integrin Interactions may be critical for effectively reducing nativ e tropism and enhancing the efficacy of specific targeting ligands in redir ecting Ad vectors to target tissues.