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.

Efficient and persistent transduction of exocrine and endocrine pancreas by adeno-associated virus type 8

“…A major advance is the discovery of novel AAV serotypes that possess specific structural and functional features, contributing to their differential tissue tropism, transduction efficiency and immune responses [11]. Previous studies revealed that AAV1 and AAV6 are the most efficient vector for infecting islet cells in vitro [17,21], while depending on the routes of administration (intravenous, intraperitoneal, intraductal), various serotypes showed different efficiency in transducing pancreatic islets in vivo [20,21]. We confirmed the superior efficiency of AAV8, and thoroughly studied the gene expression pattern following direct pancreatic injection, a delivery route that was not fully explored in a previous report [19].…”

“…However, previous studies using AAV in pancreas were mainly focused on ex vivo approaches to modify pancreatic islets for transplantation [15][16][17][18]. Not until recently were AAV vectors tested in vivo, which showed promising efficiency in transducing pancreas [19][20][21]. Nevertheless, these reports primarily focused on infection of endocrine islet cells for the purpose of treating diabetes.…”

“…In this study, we reported the efficiency of lentivirus in infecting pancreas in vivo for the first time, and compared with multiple AAV serotypes including type 1, 2, 5, 8 delivered by direct intrapancreatic injection. These four serotypes were chosen based on their promising effectiveness suggested by previous reports [15][16][17][18][19][20][21]. A thorough characterization of pancreatic gene delivery conferred by these vectors was performed in terms of cell tropism, transduction efficiency, duration of transgene expression, tissue distribution and histopathology.…”

Gene therapy: The first two decades and the current state‐of‐the‐art

“…Receptor-specific ligands have been inserted into specific regions of the capsid gene so that they are then displayed on the surface of the capsid (Wu et al, 2000;Nicklin and Baker, 2002;Loiler et al, 2003Loiler et al, , 2005Nicklin et al, 2003;White et al, 2004;Work et al, 2004). Work is also progressing with rAAV vectors that are based on newly available serotypes and genomic variants of AAV (Chao et al, 2000;Gao et al, 2002;Rabinowitz et al, 2002).…”

Gene Therapy for Type 1 Diabetes: Is it Ready for the Clinic?

“…Although limited, recent studies are beginning to confirm the utility of direct intrapancreatic vector administration for diabetes therapy, originally reported a decade ago (32) and improved more recently (33)(34)(35). Along these lines, a recent study by Bosch and colleagues (36) is important in two respects.…”