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.