Adeno-associated virus type 5-mediated intraarticular administration of tumor necrosis factor small interfering RNA improves collagen-induced arthritis

Objective. RNA interference (RNAi) is a powerful tool for sequence-specific gene silencing, and interest in its application in human diseases is growing. Given the success of recent strategies for administering gene therapy in rheumatoid arthritis using recombinant vectors such as adeno-associated virus type 5 (rAAV5) for optimized intraarticular gene transfer, we undertook the present study to determine the feasibility of using rAAV5-mediated RNAi-based therapy in arthritis. Methods. We developed rAAV5 vectors expressing short hairpin small interfering RNA (shRNA) against tumor necrosis factor α (TNFα) under H1 promoter, and carrying the enhanced green fluorescent protein (eGFP) reporter gene under cytomegalovirus promoter (rAAV5-shTNF). TNFα gene silencing was validated in vitro with mouse macrophages. Mice with collagen-induced arthritis were injected in the ankle and knee joints, at disease onset, with either rAAV5-shTNF or control rAAV5-eGFP vectors (5 × 10⁹ particles). Arthritis severity was assessed clinically and histologically, and immunologic response was examined. Local and systemic transgene expression was monitored using quantitative reverse transcriptase-polymerase chain reaction, immunohistochemical analysis, and enzyme-linked immunosorbent assay. Results. After a single injection of rAAV5-shTNF into inflamed joints, local TNFαgene silencing provided rapid and long-term suppression of arthritis progression and reduced joint damage compared with that observed in control groups. Treatment with rAAV5-shTNF was associated with decreased proliferation and interferon-γ production by antigen-stimulated T cells from draining lymph nodes, and the potency of this treatment was similar to that observed with other treatment strategies targeting TNFα at the protein level, either locally or systemically. Conclusion. Our data present the first proof-of-concept for the application of rAAV5-mediated RNAi-based gene therapy for local blockade of inflammation in experimental arthritis.