Targeted adenoviral vectors

Abstract

Subgroup C human adenoviruses (Ad2 or Ad5) can transduce a wide array of dividing and quiescent adherent cell types in vitro and in vivo, essentially because their primary receptor (CAR) is widely expressed at the cellular surface. On the other hand, specific target cell types (eg some tumor cells, smooth muscle cells, fibroblasts) display limiting amounts of the CAR receptor so that large viral doses are needed for efficient infection, a constraint which favors vector dissemination in vivo, even after loco-regional injection. Abrogating the native virus-CAR interaction while allowing the virus to use a CAR-independent pathway for entry would thus represent a major milestone in order to better control the vector tropism in vivo. Towards this goal, we first engineered a series of capsid-modified adenoviruses by genetically inserting targeting peptides within protruding loops of the fiber and hexon capsid monomers (Vigne E, et al: J Virol 1999, 73:5156). The most interesting virus – AE43 – displays within the fiber HI loop a vitronectin-derived high affinity peptide for the urokinase-type plasminogen activator (uPAR or CD87), a cell surface receptor upregulated during cellular activation, and which controls cellular migration and invasion. Most interestingly, AE43 could increase transduction of cells normally refractory to adenovirus infection more than 100-fold in vitro. We could also demonstrate that AE43 retained its ability to enter the cell via a CAR-dependent pathway in vitro, and displayed a normal tropism following systemic injection in mice. To cripple the virus-CAR interaction, we then evaluated various strategies, including the introduction of CAR-ablating mutations within the fiber, and the shortening of the fiber shaft. Interestingly, some of these constructs could decrease transduction of CAR-positive cells at least 10-fold in vitro, with a similar reduction in liver transduction following systemic injection in naive mice. We are currently assessing the effect of combining within a single vector the uPAR-binding peptide of AE43 with our best CAR-ablating mutations.