Novel human gene transfer vectors: Evaluation of wild-type and recombinantanimal adenoviruses in human-derived cells

Major disadvantages of human adenovirus (hAd) vectors in gene therapy inclu de preexisting or induced immune responses, and possible coreplication of r ecombinant hAd in the presence of wild-type hAds. These disadvantages may b e overcome by using nonhuman, animal adenoviruses (aAds). We evaluated four different aAds for their potential use as viral vectors. The canine adenov irus type 2 (CAV2) and bovine adenovirus type 3 (BAV3) appeared to be suita ble systems, as they infect human cells. CAV2, but not BAV3, caused cytotox icity, and only limited (CAV2) or no (BAV3) production of infectious virus particles was observed after infection of human cell lines. CAV2 showed hig her expression of endogenous genes than did BAV3 in the tested human cells. No interference between hAd and CAV2 or BAV3, such as recombination of DNA or cross-activation of virus replication, was observed in up to five passa ges in double-infected human cells. Transfection of cloned genomic CAV2 or BAV3 DNA into appropriate permissive cell lines rescued infectious virus. F urthermore, we produced a recombinant E1-deleted BAV3, and showed that it c ould infect and express a reporter gene in various human cell types.