Localized Gene Expression Following Administration of Adeno-associated Viral Vectors via Pancreatic Ducts

Abstract

Gene transfer into pancreatic cells in vivo could be of immense therapeutic benefit in cases of type 1 diabetes (T1D) through the production of molecules capable of interrupting the progression of autoimmunity or promoting regeneration of insulin-secreting beta cells. We adapted a clinically relevant surgical technique (endoscopic retrograde cholangiopancreatography) to deliver rAAV encoding human alpha1-antitrypsin (approved gene symbol SERPINA1) to the pancreas of 3-week-old Fisher 344 rats and C57BL/6 mice. We compared natural as well as bioengineered serotypes of rAAV (rAAV1, rAAV2/Apo, rAAV8) as well as different promoters (chicken beta-actin, human insulin) for their expression in vivo. Rats injected with rAAV1 showed the highest hAAT expression (week 2, rAAV1/CB-AT, 579 +/- 457 ng/ml). In mice, rAAV8 vector delivered the highest serum concentration of hAAT (week 2, rAAV8/CB-AT, 19 +/- 6 microg/ml). The chicken beta-actin promoter provided the highest expression in both rodent experiments. Immunohistochemical staining indicated transduction primarily of pancreatic acinar cells with either the rAAV1/CB-AT vector in the rat or the rAAV8/CB-AT vector in the mouse. This study demonstrates that rAAV vectors can be designed to deliver therapeutic genes efficiently to the pancreas and achieve high levels of gene expression and may be useful in treating pancreatic disorders, including T1D.