A variety of non-viral and viral vectors have been tested for the local and systemic treatment of rheumatic diseases by gene therapy10. The human adenovirus type 5 (HAdV5)-based vectors gave the best results, despite low efficiency in transduction of rheumatoid synovium in RA animal models11. HAdV5 infection is initiated by the attachment of the viral vector to its high-affinity receptor, the Coxsackie-adenovirus receptor (CAR), on the surface of cells12. However, human FLS do not express CAR on their surface and are thus poorly transduced by HAdV5 vectors13.