New tools for the construction of replication-competent adenoviral vectors with altered E1A regulation

We have designed new vectors for the construction of recombinant adenoviruses containing the early region 1A (E1A) gene under the transcriptional control of heterologous promoters. The normal E1A regulatory elements have been replaced by a convenient set of unique restriction enzyme sites, allowing for introduction of gene regulatory cassettes with relative ease. Subsequent rescue generates recombinant conditionally replicating adenovirus in which the transcription of E1A is under alternative control. This allows potentially cell-type specific expression of E1A, restricting efficient virus replication to chosen target cells. It is shown that in several viruses rescued using these constructs, E1A expression is regulated by the heterologous promoters in the expected manner. Specifically, a virus with E1A under the control of the human Cytomegalovirus Immediate Early promoter produced constitutively high levels of E1A. A second virus, with E1A expression regulated by the glucocorticoid-responsive Mouse Mammary Tumor Virus promoter produced E1A expression in a dose-dependent manner upon dexamethasone treatment. Efficient growth of this second virus also required the presence of dexamethasone.