Although adenovirus is an attractive vehicle for transferring although intraportal infusion of adenoviruses carrying a therapeutic genes in vivo, animal studies have indicated reporter lacZ gene resulted in transient high levels of transthat the clinical usefulness of adenoviruses may be limited gene expression in the rat liver, intraportal readministration by their immunogenicity. Although immunosuppressive of adenoviruses failed to induce detectable levels of transstrategies around the time of initial exposure of adenogene expression. Conversely, when animals were treated viruses have been shown to prevent the formation of neutransiently with cyclophosphamide before the intraportal tralizing antibodies and permit the successful readminisreadministration of adenoviruses, development of neutration of adenoviruses in animals, the practicality of the tralizing antibodies and antigen-specific T cell proliferation approaches remains questionable. Because the majority of in response to adenoviral readministration was significantly prospective gene therapy patients have already been suppressed and successful re-expression of the transgene infected with wild-type adenoviruses, initial treatment with was achievable. These results may have important impliadenoviruses in humans may correspond to readminiscations for efficacy considerations when adenoviral vectors tration of adenoviruses into animals. It is shown here that are employed in clinical settings.