Systemic Effects of AAV.COMPAng1 in the Ins2Akita Diabetic Mouse

Abstract

Purpose : Diabetic retinopathy (DR) involves vascular hyperpermeability and capillary dropout. Angiopoietin-1 (Ang1) acting on Tie2 receptor is known to be important in retinal vasculature stabilization; angiopoietin-2, an Ang-1-antagonist, is increased in DR. We previously showed that intravitreal injection of AAV2.COMPAng1, a more stable analogue of Ang1, prevents vascular loss and leakage and preserves visual acuity in type 1 diabetic Ins2Akita mice. AAV10 serotype has been shown to elicit minimal neutralizing immune response in mice and humans; we previously showed that a single intravenous injection of AAV10.COMPAng1 does not transduce the gene in the eye but achieves systemic distribution and sustains therapeutic levels of serum COMPAng1 at least 2 weeks post-injection. We now examine effects of AAV10.COMPAng1, systemically and on visual function, 6 months post-injection.

Methods : We treated 2-month-old Akita with a single tail vein injection of AAV10.COMPAng1, AAV10.GFP, or PBS for controls. At 6 months post-injection, we assessed mice for fasting blood glucose, body weight, hemoglobin A1c (HgbA1c), serum COMPAng1 by ELISA, visual tracking response by OptoMotry, retinal thickness by OCT, and scotopic ERG response. At 6 weeks and 3 months post-AAV10.GFP treatment, we harvested liver, lung, kidney, and retina to examine GFP expression by immunofluorescence staining and semi-quantitative RT-PCR.

Results : Therapeutic levels of serum COMPAng1 were reached as early as 7 days and sustained at 6 months post-injection. At 8 months old, Akita treated with AAV10.COMPAng1 when 2 months old had significant lowering of HgbA1c, fasting blood glucose, and body weight as compared to Akita controls. There was no difference in visual tracking response, retinal thickness, or ERG response. Mice did not show adverse effects or reactions. At 6 weeks and 3 months after AAV10.GFP treatment, we found most GFP expression in liver, followed by lung, then kidney.

Conclusions : Serum COMPAng1 was expressed at therapeutic levels as early as 7 days and sustained for 6 months after a single intravenous treatment. Although AAV10.COMPAng1-treated Akita did not differ from Akita controls on visual function measures, the treated mice, on average, had significantly lower HgbA1c, fasting blood glucose, and body weight as compared to controls. Further studies are required to evaluate the potential of AAV.COMPAng1 as a therapeutic against diabetic end-organ disease.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.