![]() ![]() In view of that, we sought to develop new capsid variants with further enhanced human islet cell transduction efficiency using directed evolution. More recently, capsid variants AAV-DJ ( 24) and AAV-LK03 ( 25) were found to have better transduction efficiency on human islets as compared with AAV2 and AAV3B however, a strong preference for α cells was observed for those capsids ( 26).Įven though different AAV capsids that are capable of transducing human islets have been described, the current low efficiencies limit their broad applicability to diabetes. AAV2 is the serotype that has been described most frequently for transduction of human islets ( 22, 23). Interestingly, studies in rats found that AAV5 was the best capsid for islet transduction in this animal model ( 21). Recently, tyrosine-phenylalanie (Y-F) mutant AAV8 vectors have been reported to achieve up to 10-fold improved gene transfer into mouse islets as compared with WT AAV8 ( 20). However, when delivered systemically, AAV8 proved to be the more robust serotype ( 19). Another study found that AAV6 was highly efficient in transducing mouse islets in vitro and in vivo when using intraductal delivery. delivery of an AAV8-based vector expressing IL-2 under control of the β cell type–specific insulin promoter has been described to achieve highly specific transduction of β cells in mice ( 18). However, rAAV vectors packaged with AAV8 capsid were also employed ( 11), as this serotype had previously been found to transduce murine β cells with high efficiency ( 16, 17). Most of those in vivo studies involved transgenic mouse models or used adenoviral vectors to deliver expression cassettes. Cell conversion has been achieved by overexpression or repression of certain transcription factors, such as Pdx1, Ngn3, MafA, Pax4, and Arx ( 7– 15). One strategy for diabetes treatment is the conversion of α cells or other endocrine or exocrine pancreatic cell types into β cells (reviewed in ref. Over a period of 30 weeks, this gene therapy strategy was successfull in counteracting progression to autoimmune diabetes. Igf1 is a prosurvival factor and β cell mitogen that has important roles in β cell maturation and function and is also involved in the interplay between the endocrine and the immune system. Recently, a study described the use of rAAV to overexpress Igf1 in diabetic mice ( 5). In addition to the approaches described above, it is of the utmost importance to prevent loss of the transplanted islets due to recurrent autoimmune destruction. Recombinant AAV–mediated (rAAV-mediated) overexpression of Follistatin, a protein with important roles in the proper functioning of the reproductive, endocrine, and muscoskeletal systems, has been shown to promote β cell proliferation and maintain pancreatic islet mass in a diabetic mouse model ( 4). In order to improve graft survival and function, different approaches of ex vivo gene therapy, either by supplying or repressing certain transcription factors using different viral or nonviral delivery systems (for example adeno-associated virus (AAV), adenovirus, lentivirus, various lipids, or nonlipid polymers), may be used (reviewed in ref. Because revascularization of the transplanted islets takes several weeks, those transplants suffer from a large number of cell death due to oxygen deprivation. Islets are highly vascularized and require large amounts of oxygen to survive. For example, transplantation of cadaveric human islets into the hepatic duct has been used to replace β cells in type 1 diabetic patients, so far with low efficiencies (reviewed in ref. ![]() Various strategies to cure diabetes have been evaluated over the years with limited success. Remarkably, this chimeric capsid also enabled transduction of both mouse and human hepatocytes at very high levels in a humanized chimeric mouse model, thus providing a versatile vector that has the potential to be used in both preclinical testing and human clinical trials for liver-based diseases and diabetes.Īn estimated 30.3 million US Americans are affected by either type 1 or type 2 diabetes mellitus ( 1). We describe the generation of a chimeric AAV capsid (AAV-KP1) that facilitates transduction of primary human islet cells and human embryonic stem cell–derived β cells with up to 10-fold higher efficiency compared with previously studied best-in-class AAV vectors. Because of the recent success in reprogramming islet-derived cells into functional β cells in animal models, we constructed 2 highly complex barcoded replication competent capsid shuffled libraries and selected for high-transducing variants on primary human islets. While gene transfer using recombinant adeno-associated viral (rAAV) vectors has shown success in some clinical trials, there remain many tissues that are not well transduced. ![]()
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