574. Sustaining Helper-Dependent Adenoviral Vector-Mediated Human CFTR Expression in Mouse Airways Through Transient Immunosuppression

Abstract

Cystic Fibrosis (CF) is a common life-threatening disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which encodes an epithelial chloride channel. Gene therapy for CF lung disease has been tested extensively. However, sustained expression of the CFTR gene is a major challenge to gene delivery with either viral or no viral vectors. One strategy to improve the persistent CFTR expression is to modulate host immune responses by transient immunosuppression.We showed previously that cyclophosphamide significantly enhanced human CFTR expression in mice received HD-Ad vector readministration, through inhibition of host immune reactions. In this study, we examined cyclophosphamide, dexmethoson, and combination of cyclosporine, methylprednsolone and azathioprine, for their effects on long term expression of the human CFTR delivered with helper-dependent adenoviral (HD-Ad) vectors to mouse airways. Four group mice were nasally delivered with an HD-Ad-K18-CFTR vector at 1.5×10E10 particles per mouse. Three groups were treated with immunesuppresants and one group without any treatment was used as a control. The immunosuppressants were administrated twice, at 6 hours before and 48 hours after nasal delivery of the HD-Ad-CFTR vector. Expression of the CFTR gene was assessed 4 months after vector administration. We found that cyclophosphamide has significantly improved the sustained expression of the CFTR gene (2.5 times higher) compared to the no treatment group as determined by real-time qPCR. It alsogreatly reduced the levels of anti-adenoviral and neutralizing antibodies in both BALF and serum. However, cyclophosphamide did not show major effects on the innate immune reaction to HD-Ad vectors, such as NK cell infiltration and activation, 4 days after vector delivery. Dexmethesone also greatly reduced neutralizing antibodies production, but not affected transgene expression. A combination of cyclosporine, methylprednsolone and azathioprine which is used to suppress immune reactions in lung transplantation, also did not affect CFTR gene expression, nor immune reactions following HD-Ad-CFTR vector delivery. These data demonstrate that transient administration of cyclophosphamide can significantly improve sustained HD-Ad-mediated transgene expression in mice and it is more effective than dexmethsone or the combination of cyclosporine, methylprednsolone and azathioprine.