The Study Of RAAV Carrying Rat CTLA4-FasL Fusion Gene In Gene Therapy For Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic, autoimmune disease, which is characterized by jointsynovitis. It mainly affects the joint cavity of the synovial tissue and even results in bonedestruction of cartilage. The high rate of teratogenicity affects the quality of patients’life.Rheumatoid arthritis is characterized by intra-articular pathology of the abnormal proliferation ofsynovial cells, and inflammatory cell infiltration.Fibroblast-like synoviocytes (FLSs) contribute significantly to the pathogenesis of RA.Through introducing apoptosis inducer FasL to suppress the proliferation of arthritic FLSs mayprovide an efficient approach for treatment of RA. T lymphocytes are key inflammatory cellscontributing significantly to the pathogenesis of RA. Biological treatments targeting Tlymphocytes may provide an efficient approach for treatment of RA. CTLA4–FasL, a fusionproduct of extracellular domains of CTLA4(which can induce T cell anergy through blockingcostimulatory signal) and FasL(which may upregulate Fas-mediated apoptosis in inflammatorysynoviocytes), integrating two inhibitory elements against T cells into one molecule, might be adesirable derivative of engineered soluble FasL or CTLA4and have therapeutic potential in RA.In present study, we investigated the possible effect of CTLA4-FasL protein on suppressing theproliferation of inflammatory FLSs and inflammation in experimental model of RA. The purifiedCTLA4-FasL protein exerted a significant proliferation-inhibition activity to activated arthriticFLSs through both unbounded free and membrane-anchorage manners. Recombinantadeno-associated virus (rAAV) vectors encoding rat CTLA4–FasL fusion gene(rAAV.CTLA4–FasL) or enhanced green fluorescent protein (rAAV.EGFP) were injectedintraarticularly into both ankle joints after immunization. The ankles were monitored by measuresof clinical, histological and inflammatory cytokines’ changes. Treatment usingrAAV.CTLA4–FasL resulted in a significant suppression of AIA compared with rAAV.EGFP control, as reflected in the mainly clinical signs including articular index, ankle joint thickness andpaw swelling and typically histological characters of arthritic joints including synovial hyperplasia,inflammatory cells infiltration and cartilage degradation. Treatment with rAAV.CTLA4–FasL alsosignificantly decreased the levels of key proinflammatory cytokines in AIA joints. Moreover, localproductions of transgene mRNA and protein of CTLA4–FasL were found in injected joints.Treatment with rAAV.CTLA4-FasL significantly decreased the levels of key proinflammatorycytokines in AIA joints. Our observations indicate that CTLA4-FasL protein represents asignificantly suppressive effect on inflammatory FLSs’ proliferation and CTLA4-FasL genetransfer profoundly suppressesAIA, implicating potential application for treatment of RA by localjoint delivery of CTLA4-FasL.