Gene therapy for rheumatoid arthritis. Lessons from animal models, including studies on interleukin-4, interleukin-10, and interleukin-1 receptor antagonist as potential disease modulators.

Evidence from animal models convincingly supports the fact that gene therapy can be an advantageous strategy in the treatment of chronic destructive RA. In this article, we review the state of the art in anticytokine gene transfer into the synovial arthritic joint with the emphasis on IL-1Ra, IL-4, and IL-10 effects on CIA in mice. In CIA, only high and continuous release of IL-1Ra protein systemically by mini-osmotic pumps could prevent disease onset and was curative in mice. Local gene transfer seemed to be the obvious way to reach the high local levels that are demanded for protection. It was shown that local IL-1Ra overexpression reduced arthritis incidence and severity as well as tissue destruction. In line with observations about neutralizing antibodies and soluble receptors, gene therapy with TNF soluble receptors provided anti-inflammatory activity in early arthritis but not in advanced arthritis. The limited efficacy at later stages and poor protection against destruction imply that the combination of gene constructs for TNF and IL-1 inhibitors is the obvious direction for future therapy. Apart from targeting of proinflammatory cytokines, adenoviral overexpression of IL-10 and IL-4 may have therapeutic applicability. Local injection of AdIL-10 in the knee joint was effective at the site, but also highly reduced spreading to ipsilateral sites. High local dosages caused suppression in contralateral sites as well. The reports on the anti-inflammatory effect of AdIL-4 are conflicting; however, all present data showed that IL-4 overexpression provides impressive protection against cartilage and bone erosion. Apart from the local effects in the injected joint, it is becoming more and more clear that local treatment also affects arthritis in nearby joints. This is an intriguing general finding, which may enlarge the therapeutic applicability of gene transfer in human arthritis. Proving the feasibility of gene therapy in experimental arthritis, most research efforts are now focused on improving local gene delivery by enhanced viral infection of synovial cells, using RGD-modified adenovirus, or achieving prolonged persistence and regulated expression with AAV. Elegant future alternatives are the application of in vitro engineered T cells as a vehicle capable of specific homing to joint tissues. The feasibility of viral transduction of chondrocytes to obtain a tissue-specific approach to treat articular cartilage damage in arthritis needs further attention.