Therapeutic gene transfer for rheumatoid arthritis

Rheumatoid arthritis (RA) is a severe autoimmune systemic disease. Chronic synovial inflammation results in destruction of the joints. No conventional treatment is efficient in RA. Gene therapy of RA targets mainly the players of inflammation or articular destruction: TNF-alpha or IL-1 blocking agents (such as anti-TNF-alpha monoclonal antibodies, soluble TNF-alpha receptor, type II soluble receptor of IL-1, IL-1 receptor antagonist), anti-inflammatory cytokines (such as IL-4, IL-10, IL-1), growth factors. In this polyarticular disease, the vector expressing the therapeutic protein can be administered as a local (intra articular injection) or a systemic treatment (extra articular injection). All the main vectors has been used in experimental models, including the more recent lentivirus and adeno-associated virus. Ex vivo gene transfer was done with synovial cells, fibroblasts, T cells, dendritic cells, and different cells from xenogenic origin. In vivo gene therapy is simpler, although less controlled method. Clinical trials in human RA has started with ex vivo retrovirus expressing IL-1 receptor antagonist and have demonstrated the feasibility of the strategy of gene therapy. The best target remains to be determined and extensive researches have to be conducted in pre-clinical studies.