BIOLOGY OF ADENOVIRUS VECTORS WITH E1 AND E4 DELETIONS FOR LIVER-DIRECTED GENE-THERAPY

Recombinant adenoviruses with E1 sequences deleted efficiently transfe r genes into a nide variety of target cells. Antigen- and nonantigen-s pecific responses to the therapy lead to toxicity, loss of transgene e xpression, and difficulties with vector readministration. We have crea ted new cell lines that allowed the isolation of more disabled adenovi rus vectors that have both E1 and E4 deletions, Studies with murine mo dels of liver-directed gene therapy indicated that the E1- and E4-dele ted vector expresses fewer virus proteins and induces less apoptosis, leading to blunted host responses and an improved safety profile. The impact of the E4 deletion on tile stability of vector expression was c onfounded by immune responses to the transgene product, which in this study was beta-galactosidase, When transgene responses were eliminated , the doubly deleted vector was substantially more stable in mouse liv er than was the E1-deleted construct. These studies indicate that aden ovirus vectors with both E1 and E4 deletions may have advantages in te rms of safety and efficacy over first-generation constructs for liver- directed gene therapy.