Stable transduction of actively dividing cells via a novel adenoviral/episomal vector

Many gene therapy indications would benefit from vectors capable of achievi ng efficient in vivo delivery and long-term transgene expression in either dividing or nondividing cells. Such vector systems are not yet available. T o achieve both goals, we have used noncytotoxic E1- and E4-deleted adenovir al vectors as vehicles for delivering an Epstein-Barr virus-based self-repl icating episome (replicon) via Cre/loxP site-specific recombination. Go-inf ection of human cells with a proreplicon-encoded and a Cre-expressing adeno virus resulted in efficient delivery and excision of a functional replicon in the absence of vector-induced cytotoxicity. In addition, replication and nuclear retention of the replicon in the cell progeny translated into a pr olonged transgene expression in actively dividing cells, both in vitro and in vivo. Combining desired features from different viruses within a single hybrid vector system should expand the range of clinical indications curren tly amenable to gene transfer.