Purpose: To evaluate the recombinant adeno-associated virus vector encoding interleukin-1 receptor antagonist (rAAV–IL-1Ra) complementary DNA for its potential in the prevention of phorbol ester–induced extraocular myositis.
Methods: Gene delivery to superior recturs muscle was achieved through intramuscular injections of rAAV-IL-1 Ra in the left eyes and AAV expressing Escherichia coli LacZ (rAAV-LacZ) in the right eyes of white rabbit. After 3 weeks, phorbol ester was used to induce myositis, and the severity of myositis was evaluated. The synthesis and accumulation of IL-1Ra within the muscle were determined using immunohistochemistry and western blot analysis three weeks after gene delivery. The preventive effects of IL-1Ra were evaluated by strain measurement, histologic changes of muscle and inflammatory cell counts one week after myositis induction.
Results: Gene expression of IL-1 Ra was demonstrated through immunohistochemistry and Western blot analysis. Histology revealed more inflammatory cells were retained in the rAAV- LacZ treated muscles (2594.386±319.933 cells/mm2; n=10) than in the rAAV- IL-1 Ra treated
muscles (1369.479±228.509 cells/mm2; n=10). Strain measurement increased 150.4% 1 week after injection of phorbol ester in right eye, and increased 69.4% in the left eye with previous rAAV–IL-1Ra injection (p<0.01). The myositis in rAAV- IL-1 Ra treated muscles was less severe than that in the rAAV- LacZ treated muscles.
Conclusion: This gene therapy, by combining highly efficient and stable rAAV gene delivery, and the anti-inflammatory effect of IL-1Ra, provides a valuable approach for prevention of extraoculor myositis.
