Objective: To characterize the adenoviral properties required to enhance intracellular transgene expression for gene therapy.
Methods: Primary human fibroblasts and macrophages were infected with standard replication-defective adenoviruses, adenoviral vectors containing modified fiber coat proteins expressing Arg-Gly-Asp (RGD) or heparin sulfate binding moieties, or a tetracycline-regulatable transgene transcription system. Each of these vectors expressed the beta-galactosidase gene (beta-Gal), which was quantified by flow cytometry. Ankle joints from rats with adjuvant induced arthritis were transduced intraarticularly with each of the vectors and B-Gal expression was quantified by flow cytometry.
Results: Primary human fibroblasts and macrophages displayed marked increases in transgene expression from both modified fiber protein vectors and from the tetracycline-regulatable vector, compared to an unmodified vector expressing the transgene from the cytomegalovirus promoter/enhancer. In the rat model, the modified fiber protein vectors and the tetracycline-regulatable vector system also displayed increased transgene expression in inflamed rat joints.
Conclusion: Adenovirus attachment and uptake by cells and promoter strength limit transgene expression from conventional adenoviral vectors in models of rheumatoid arthritis.