The plasmid pAdEasy-1, containing most of the human adenovirus serotype 5 (Ad5) genome, is deleted for the genes E1 and E3. The removal of these two viral genes creates space for foreign DNA and eliminates selfreplication capabilities. The E1 deletion renders the viruses defective for replication and incapable of producing infectious viral particles in target cells (provided there is no complementation by the host cell); the E3 region encodes proteins involved in evading host immunity and is dispensable. The deletion of both genes creates room for up to 7.5 kb of foreign DNA that can be inserted into the Ad5 genome. The E1 gene, which is necessary for production of viral particles, is provided in trans by AD-293 cells. pAdEasy-1 carries the ampicillin resistance gene, which is lost after recombination with a shuttle vector.
