Improvements in adenovirus technology : aiming at replication specificity and vector integration

Current generation adenoviral vectors (Ads) are not suitable for those gene therapy approaches that require long-term gene expression. This is due to their high immunogenicity and transient gene expression in fast dividing tissue. The development of gutless Ads, also known as helper-dependent Ads, is a major improvement in reducing the immunogenicity of the vector system. Gutless Ads lack virtually all viral protein-coding sequences, thus severely limiting the viral-antigen evoked cellular immune responses that may result in the elimination of the transduced cells. Safety wise, recombinant Ads are considered safe due to their inability to replicate autonomously. However, we show in this thesis that replication of recombinant Ads can be rescued by the co-infection of wild type (wt) Ads. In this thesis studies are described that aim at the development of a new system to prevent vector mobilization. Though at its present state not directly applicable, this system could also potentially be used for the production of gutless Ads devoid of helper Ad contamination. To improve efficacy of the Ad vector in dividing tissue we also studied two integration systems for their applicability in Ads. Overall, the experiments described in this thesis aim at generating safer vectors that should result in prolonged transgene expression due to lower immunogenicity and genomic integration.