Frequency and stability of chromosomal integration of adenovirus vectors

One of the limitations of adenovirus vectors is the lack of machinery neces sary for their integration into host chromosomes, resulting in short-term g ene expression in dividing cells. We analyzed frequencies of integration an d persistence of gene expression from integrated adenovirus vectors. Both E l-substituted and helper-dependent adenovirus vectors achieved similar inte gration efficiencies of similar to 10(-3) to 10(-5) per cell, with the help er-dependent vector showing slightly higher efficiencies. Un stable cell po ols, gene expression of the integrated vector persisted for at least 50 cel l divisions without selection. However, some stable cell clones showed chan ges in gene expression, which were accompanied by structural changes in the integrated vector DNA.