R 440
Gene therapy in retinal dystrophies hopes and limitations
J. Bennett, N. S. Dejneka, A. Auricchio, A. M. Maguire
Purpose: There has been great progress in the past few years in demonstrating proof of principle for gene therapy for retinal degenerative diseases such as retinitis pigmentosa (RP). One challenge at present is to obtain the appropriate levels of transgene expression in the target cells at the appropriate developmental stage. Using both adenovirus and adeno-associated virus (AAV), we evaluated an externally regulatable promoter for use in gene retinal therapy.
Methods: Subretinal injections of virus were performed in mice with retinal degeneration and with normal retinas. Transgene expression was characterized as a function of time using the externally regulatable tetracyclin inducible promoter system (tet-on). Reporter genes included green fluorescent protein (GFP) and biologically active molecules (human growth hormone).
Results: Transgene expression could be induced in all animals through ingestion of the tetracyclin analogue, doxycycline. Transgene expression was substantially reduced when doxycycline was removed. Further, expression could be elicited additional times upon readministration of the doxycycline. There was no limit to the duration of transgene expression in AAV-treated animals. Longterm studies of transgene regulation in adenovirus-treated animals could only be performed using immunodeficient animals.
Conclusions: Longterm externally regulatable retinal transgene expression can be achieved through delivery of AAV vectors containing the tetracyclin inducible promoter system. This system promises to be useful not only for therapeutic purposes but also to define stages of degeneration in which rescue is no longer possible.
Supported by: NIH RO1 EY12156 and RO1 EY10820, FFB, the Mackall Foundation Trust, and the F.M. Kirby
Foundation.
Scheie Eye Institute, University of Pennsylvania, 310 Stellar-Chance Labs, 422 Curie Blvd., Philadelphia, PA USA