Abstract
Purpose: :
Lentiviral vectors achieve permanent integration and are capable of sustained transgene expression in the trabecular meshworks of explanted human eyes in organ perfusion culture. Long–term transgene expression exceeding two years was achieved in domestic cats and was tracked by non–invasive monitoring. To further assess potential for application to glaucoma gene therapy, we injected FIV–based lentiviral vectors into the anterior chambers of cynomolgus monkeys.
Methods: :
4 cynomolgus monkeys received transcorneal anterior chamber (AC) bolus injections of vesicular stomatitis virus glycoprotein G–pseudotyped, eGFP–encoding FIV vectors. Six eyes total were injected, with doses of 0.03, 0.3, 1.0, 1.0, 1.0 and 2.0 x 10^8 transducing units (TUs) respectively. Follow–up examinations included intraocular pressure (IOP) measurements, slit lamp biomicroscopy, gonioscopy and UV illumination and photography to detect eGFP fluorescence.
Results: :
All four eyes injected with 1.0 or 2.0 x 10^8 TUs showed significant eGFP fluorescence in the TM during weeks 1–4, which was the most recent time point measured in three of the eyes. The one animal that has been followed long term continues to display eGFP fluorescence in the TM nine months after being injected with 1.0 x 10^8 TUs. The lowest dose eye (0.03 x 10^8 TUs) did not show gonioscopically detectable fluorescence at any time point. The eye injected with 0.3 x 10^8 TUs showed a low level of fluorescence in weeks 1–4. Mild to moderate AC inflammatory reactions (1–2+ cells, trace to 2+ flare) were seen in week 1 in the five highest–dose eyes, but these were minimal after several weeks. A transient fall in IOP was concurrently observed in week 1, with return to baseline by week 4. Enucleation and examination of some eyes for transgene expression and histology is scheduled within the next several months.
Conclusions: :
These data are the first demonstration of trabecular meshwork transduction with lentiviral vectors in nonhuman primates. FIV vectors transduced cynomolgus monkey TM without raising IOP and caused only short–term, modest inflammation. Sustained eGFP expression for nine months was achieved. Since gonioscopic examination only discloses highest levels of eGFP fluorescence and thus underestimates efficacy of gene transfer (our unpublished feline data), continued in vivo observations of these monkeys coupled with follow–up examination of enucleated eyes are planned.
Keywords: gene transfer/gene therapy • trabecular meshwork • anterior chamber