The core/E1 and E2 amplicons were cloned into pGEMEasy (Promega) and subsequently subcloned and ligated to produce a construct which was verified by DNA sequencing. This construct was subsequently subcloned into pAdTrack-CMV (provided by B Vogelstein, Howard Hughes Medical Centre, Baltimore), digested with PmeI and transformed into AdEasier-1 cells by electroporation (Bio-Rad Gene Pulser) as previously described [24] .