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Adeno-Associated Viral Vector Delivery to the Enteric Nervous System: A Review.

ABSTRACT: Gene therapy to the gastrointestinal tract has remarkable potential for treating gastrointestinal disorders that currently lack effective treatments. Adeno-associated viral vectors (AAVs) have been extensively applied to the central nervous system, and have repeatedly demonstrated safety and efficacy in animal models. The enteric nervous system (ENS) represents a vast collection of neurons and glial cells that may also be subject to treatment by AAV, however little work has been conducted on AAV delivery to the ENS. Challenges for gastrointestinal gene therapy include identifying gene targets, optimizing gene delivery, and target cell selection. Researchers are now beginning to tackle the later of the two challenges with AAV, and the same AAV technology can be used to identify novel gene targets in the future. Continued efforts to understand AAV delivery and improve vector design are essential for therapeutic development. This review summarizes the current knowledge about AAV delivery to the ENS.

SUBMITTER: Gombash SE

PROVIDER: S-EPMC5001153 | biostudies-other | 2015 Aug

REPOSITORIES: biostudies-other

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Adeno-Associated Viral Vector Delivery to the Enteric Nervous System: A Review.

Gombash Sara E SE

Postdoc journal : a journal of postdoctoral research and postdoctoral affairs 20150801 8

Gene therapy to the gastrointestinal tract has remarkable potential for treating gastrointestinal disorders that currently lack effective treatments. Adeno-associated viral vectors (AAVs) have been extensively applied to the central nervous system, and have repeatedly demonstrated safety and efficacy in animal models. The enteric nervous system (ENS) represents a vast collection of neurons and glial cells that may also be subject to treatment by AAV, however little work has been conducted on AAV ...[more]

PMID: 27570787

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Project description:RATIONALE:Somatic overexpression in mice using an adeno-associated virus (AAV) as gene transfer vectors has become a valuable tool to analyze the roles of specific genes in cardiac diseases. The lack of atrial-specific AAV vector has been a major obstacle for studies into the pathogenesis of atrial diseases. Moreover, gene therapy studies for atrial fibrillation would benefit from atrial-specific vectors. Atrial natriuretic factor (ANF) promoter drives gene expression specifically in atrial cardiomyocytes. OBJECTIVE:To establish the platform of atrial specific in vivo gene delivery by AAV-ANF. METHODS AND RESULTS:We constructed AAV vectors based on serotype 9 (AAV9) that are driven by the atrial-specific ANF promoter. Hearts from mice injected with AAV9-ANF-GFP (green fluorescent protein) exhibited strong and atrial-specific GFP expression without notable GFP in ventricular tissue. In contrast, similar vectors containing a cardiac troponin T promoter (AAV9-TNT4-GFP) showed GFP expression in all 4 chambers of the heart, while AAV9 with an enhanced chicken ?-actin promoter (AAV-enCB-GFP) caused ubiquitous GFP expression. Next, we used Rosa26mT/mG (membrane-targeted tandem dimer Tomato/membrane-targeted GFP), a double-fluorescent Cre reporter mouse that expresses membrane-targeted tandem dimer Tomato before Cre-mediated excision, and membrane-targeted GFP after excision. AAV9-ANF-Cre led to highly efficient LoxP recombination in membrane-targeted tandem dimer Tomato/membrane-targeted green fluorescent protein mice with high specificity for the atria. We measured the frequency of transduced cardiomyocytes in atria by detecting Cre-dependent GFP expression from the Rosa26mT/mG allele. AAV9 dose was positively correlated with the number of GFP-positive atrial cardiomyocytes. Finally, we assessed whether the AAV9-ANF-Cre vector could be used to induce atrial-specific gene knockdown in proof-of-principle experiments using conditional JPH2 (junctophilin-2) knockdown mice. Four weeks after AAV9-ANF-Cre injection, a strong reduction in atrial expression of JPH2 protein was observed. Furthermore, there was evidence for abnormal Ca2+ handling in atrial myocytes isolated from mice with atrial-restricted JPH2 deficiency. CONCLUSIONS:AAV9-ANF vectors produce efficient, dose-dependent, and atrial-specific gene expression following a single-dose systemic delivery in mice. This vector is a novel reagent for both mechanistic and gene therapy studies on atrial diseases.

Project description:Gene delivery vectors based on adeno-associated viruses (AAV) have exhibited promise in both preclinical disease models and human clinical trials for numerous disease targets, including the retinal degenerative disorders Leber's congenital amaurosis and choroideremia. One general challenge for AAV is that preexisting immunity, as well as subsequent development of immunity following vector administration, can severely inhibit systemic AAV vector gene delivery. However, the role of neutralizing antibodies (NABs) in AAV transduction of tissues considered to be immune privileged, such as the eye, is unclear in large animals. Intravitreal AAV administration allows for broad retinal delivery, but is more susceptible to interactions with the immune system than subretinal administration. To assess the effects of systemic anti-AAV antibody levels on intravitreal gene delivery, we quantified the anti-AAV antibodies present in sera from non-human primates before and after intravitreal injections with various AAV capsids. Analysis showed that intravitreal administration resulted in an increase in anti-AAV antibodies regardless of the capsid serotype, transgene or dosage of virus injected. For monkeys injected with wild-type AAV2 and/or an AAV2 mutant, the variable that most significantly affected the production of anti-AAV2 antibodies was the amount of virus delivered. In addition, post-injection antibody titers were highest against the serotype administered, but the antibodies were also cross-reactive against other AAV serotypes. Furthermore, NAB levels in serum correlated with those in vitreal fluid, demonstrating both that this route of administration exposes AAV capsid epitopes to the adaptive immune system and that serum measurements are predictive of vitreous fluid NAB titers. Moreover, the presence of preexisting NAB titers in the serum of monkeys correlated strongly (R=0.76) with weak, decaying or no transgene expression following intravitreal administration of AAV. Investigating anti-AAV antibody development will aid in understanding the interactions between gene therapy vectors and the immune system during ocular administration and can form a basis for future clinical studies applying intravitreal gene delivery.

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Adeno-Associated Viral Vector Delivery to the Enteric Nervous System: A Review.

Publications

Adeno-Associated Viral Vector Delivery to the Enteric Nervous System: A Review.

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