Efficient Gene Delivery and Expression in Pancreas and Pancreatic Tumors by Capsid-Optimized AAV8 Vectors

Optimized rAAV8 targeting acinar KLF4 ameliorates fibrosis in chronic pancreatitis via exosomes-enriched let-7s suppressing pancreatic stellate cells activation

Chronic pancreatitis (CP) is marked by progressive fibrosis and the activation of pancreatic stellate cells (PSCs), accompanied by the destruction of pancreatic parenchyma, leading to the loss of acinar cells (ACs). Few research studies have explored the mechanism by which damaged ACs (DACs) contribute to PSCs activation and pancreatic fibrosis. Currently, there are no effective drugs for curing CP or limiting the progression of pancreatic fibrosis. In this research, co-culture with intact acinar cells (IACs) suppressed PSC activation, while co-culture with DACs did the opposite. Krüppel-like factor 4 (KLF4) was significantly upregulated in DACs and was established as the key molecule that switches ACs from PSCs-suppressor to PSCs-activator. We revealed the exosomes of IACs contributed to the anti-activated function of IACs-CS on PSCs. MiRNome profiling showed that let-7 family is significantly enriched in IAC-derived exosomes (>30% miRNome), which partially mediates IACs' suppressive impacts on PSCs. Furthermore, it has been observed that the enrichment of let-7 in exosomes was influenced by the expression level of KLF4. Mechanistic studies demonstrated that KLF4 in ACs upregulated Lin28A, thereby decreasing let-7 levels in AC-derived exosomes, and thus promoting PSCs activation. We utilized an adeno-associated virus specifically targeting KLF4 in ACs (shKLF4-pAAV) to suppress PSCs activation in CP, resulting in reduced pancreatic fibrosis. IAC-derived exosomes hold potential as potent weapons against PSCs activation via let-7s, while activated KLF4/Lin28A signaling in DACs diminished such functions. ShKLF4-pAAV holds promise as a novel therapeutic approach for CP.

The TRIM28/miR133a/CD47 axis acts as a potential therapeutic target in pancreatic necrosis by impairing efferocytosis

Efferocytosis, the clearance of apoptotic cells by macrophages, plays a crucial role in inflammatory responses and effectively prevents secondary necrosis. However, the mechanisms underlying efferocytosis in acute pancreatitis (AP) remain unclear. In this study, we demonstrated the presence of efferocytosis in injured human and mouse pancreatic tissues. We also observed significant upregulation of CD47, an efferocytosis-related the "do not eat me" molecule in injured acinar cells. Subsequently, we used CRISPR-Cas9 gene editing, anti-adeno-associated virus (AAV) gene modification, and anti-CD47 antibody to investigate the potential therapeutic role of AP. CD47 expression was negatively regulated by upstream miR133a, which is controlled by the transcription factor TRIM28. To further investigate the regulation of efferocytosis and reduction of pancreatic necrosis in AP, we used miR-133a-agomir and pancreas-specific AAV-shTRIM28 to modulate CD47 expression. Our findings confirmed that CD47-mediated efferocytosis is critical for preventing pancreatic necrosis and suggest that targeting the TRIM28-miR133a-CD47 axis is clinically relevant for the treatment of AP.

Pancreas-directed AAV8-hSPINK1 gene therapy safely and effectively protects against pancreatitis in mice

OBJECTIVE

Currently, there is no cure for chronic pancreatitis (CP). Germline loss-of-function variants in SPINK1 (encoding trypsin inhibitor) are common in patients with CP and are associated with acute attacks and progression of the disease. This preclinical study was conducted to explore the potential of adeno-associated virus type 8 (AAV8)-mediated overexpression of human SPINK1 (hSPINK1) for pancreatitis therapy in mice.

DESIGN

A capsid-optimised AAV8-mediated hSPINK1 expression vector (AAV8-hSPINK1) to target the pancreas was constructed. Mice were treated with AAV8-hSPINK1 by intraperitoneal injection. Pancreatic transduction efficiency and safety of AAV8-hSPINK1 were dynamically evaluated in infected mice. The effectiveness of AAV8-hSPINK1 on pancreatitis prevention and treatment was studied in three mouse models (caerulein-induced pancreatitis, pancreatic duct ligation and Spink1 c.194+2T>C mouse models).

RESULTS

The constructed AAV8-hSPINK1 vector specifically and safely targeted the pancreas, had low organ tropism for the heart, lungs, spleen, liver and kidneys and had a high transduction efficiency (the optimal expression dose was 2×1011 vg/animal). The expression and efficacy of hSPINK1 peaked at 4 weeks after injection and remained at significant level for up to at least 8 weeks. In all three mouse models, a single dose of AAV8-hSPINK1 before disease onset significantly alleviated the severity of pancreatitis, reduced the progression of fibrosis, decreased the levels of apoptosis and autophagy in the pancreas and accelerated the pancreatitis recovery process.

CONCLUSION

One-time injection of AAV8-hSPINK1 safely targets the pancreas with high transduction efficiency and effectively ameliorates pancreatitis phenotypes in mice. This approach is promising for the prevention and treatment of CP.

Recombinant adeno-associated virus 8 vector in gene therapy: Opportunities and challenges

In recent years, significant breakthroughs have been made in the field of gene therapy. Adeno-associated virus (AAV) is one of the most promising gene therapy vectors and a powerful tool for delivering the gene of interest. Among the AAV vectors, AAV serotype 8 (AAV8) has attracted much attention for its efficient and stable gene transfection into specific tissues. Currently, recombinant AAV8 has been widely used in gene therapy research on a variety of diseases, including genetic diseases, cancers, autoimmune diseases, and viral diseases. This paper reviewed the applications and challenges of using AAV8 as a vector for gene therapy, with the aim of providing a valuable resource for those pursuing the application of viral vectors in gene therapy.

Sustained heterologous gene expression in pancreatic islet organoids using adeno-associated virus serotype 8

Genetic modification of pancreatic islet organoids, assembled in vitro prior to transplantation is an emerging alternative to direct in vivo genetic manipulations for a number of clinical and research applications. We have previously shown that dispersion of islet cells followed by re-aggregation into islet organoids, or pseudoislets, allows for efficient transduction with viral vectors, while maintaining physiological functions of native islets. Among viruses currently used for genetic manipulations, adeno-associated viruses (AAVs) have the most attractive safety profile making them suitable for gene therapy applications. Studies reporting on pseudoislet transduction with AAVs are, however, lacking. Here, we have characterized in detail the performance of AAV serotype 8 in transduction of islet cells during pseudoislet formation in comparison with human adenovirus type 5 (AdV5). We have assessed such parameters as transduction efficiency, expression kinetics, and endocrine cell tropism of AAV8 alone or in combination with AdV5. Data provided within our study may serve as a reference point for future functional studies using AAVs for gene transfer to islet cell organoids and will facilitate further development of engineered pseudoislets of superior quality suitable for clinical transplantation.

Activation of Pancreatic Acinar FXR Protects against Pancreatitis via Osgin1-Mediated Restoration of Efficient Autophagy

Pancreatitis is the leading cause of hospitalization in gastroenterology, and no medications are available for treating this disease in current clinical practice. FXR plays an anti-inflammatory role in diverse inflammatory diseases, while its function in pancreatitis remains unknown. In this study, we initially observed a marked increase of nuclear FXR in pancreatic tissues of human patients with pancreatitis. Deleting the FXR in pancreatic acinar cells (FXR^acinarΔ/Δ ) led to more severe pancreatitis in mouse models of caerulein-induced acute and chronic pancreatitis, while the FXR agonist GW4064 significantly attenuated pancreatitis in caerulein or arginine-induced acute pancreatitis and caerulein-induced chronic pancreatitis. FXR deletion impaired the viability and stress responses of pancreatic exocrine organoids (PEOs) in vitro. Utilizing RNA-seq and ChIP-seq of PEOs, we identified Osgin1 as a direct target of FXR in the exocrine pancreas, which was also increasingly expressed in human pancreatitis tissues compared to normal pancreatic tissues. Pancreatic knockdown of Osgin1 by AAV-pan abolished the therapeutic effects of FXR activation on pancreatitis, whereas pancreatic overexpression of Osgin1 effectively alleviated caerulein-induced pancreatitis. Mechanistically, we found that the FXR-OSGIN1 axis stimulated autophagic flux in the pancreatic tissues and cell lines, which was considered as the intrinsic mechanisms through which FXR-OSGIN1 protecting against pancreatitis. Our results highlight the protective role of the FXR-OSGIN1 axis in pancreatitis and provided a new target for the treatment of this disease.

Adeno-associated virus-based caveolin-1 delivery via different routes for the prevention of cholesterol gallstone formation

BACKGROUND

Hepatic caveolin-1 (CAV1) is reduced in cholesterol gallstone disease (CGD). Mice with CAV1 deficiency were prone to develop CGD. However, it remains unknown whether restored hepatic CAV1 expression prevents the development of CGD.

METHODS

C57BL/6 mice were injected with adeno-associated virus 2/8 (AAV2/8) vectors carrying the CAV1 gene (^AAV2/8CAV1) via intravenous (i.v.) or intraperitoneal (i.p.) route and then subjected to a lithogenic diet (LD) for 8 weeks. Uninjected mice were used as controls. The functional consequences of rescuing CAV1 expression by either i.v. or i.p. ^AAV2/8CAV1 treatment for CGD prevention and its subsequent molecular mechanisms were examined.

RESULTS

CAV1 expression was reduced in the liver and gallbladder of LD-fed CGD mice. We discovered that ^AAV2/8CAV1 i.p. delivery results in higher transduction efficiency in the gallbladder than tail vein administration. Although either i.v. or i.p. injection of ^AAV2/8CAV1 improved liver lipid metabolic abnormalities in CGD mice but did not affect LD feeding-induced bile cholesterol supersaturation. In comparison with i.v. administration route, i.p. administration of ^AAV2/8CAV1 obviously increased CAV1 protein levels in the gallbladder of LD-fed mice, and i.p. delivery of ^AAV2/8CAV1 partially improved gallbladder cholecystokinin receptor (CCKAR) responsiveness and impeded bile cholesterol nucleation via the activation of adenosine monophosphate-activated protein kinase (AMPK) signaling, which induced a reduction in gallbladder mucin-1 (MUC1) and MUC5ac expression and gallbladder cholesterol accumulation.

CONCLUSION

CGD prevention by i.p. ^AAV2/8CAV1 injection in LD-fed mice was associated with the improvement of gallbladder stasis, which again supported the notion that supersaturated bile is required but not sufficient for the formation of cholesterol gallstones. Additionally, AAV treatment via the local i.p. injection offers particular advantages over the systemic i.v. route for much more effective gallbladder gene delivery, which will be an excellent tool for conducting preclinical functional studies on the maintenance of normal gallbladder function to prevent CGD.

Precise and efficient silencing of mutant KrasG12D by CRISPR-CasRx controls pancreatic cancer progression

Rationale: Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease with few therapeutic targets and rare effective treatments. Over 90% of PDAC tumors bear a Kras mutation, and the single-site mutation G12D (KrasG12D) is most prevalent. Methods: Here, we applied the CRISPR-CasRx system to silence the mutant KrasG12D transcript in PDAC cells. We also used a capsid-optimized adenovirus-associated virus 8 vector (AAV8) to deliver the CRISPR-CasRx system into PDAC orthotopic tumors and patient-derived tumor xenografts (PDX). Results: Our data showed that guided by a KrasG12D-specific gRNA, CasRx is able to precisely and efficiently silence the mutant KrasG12D expression in PDAC cells. The knockdown of mutant KrasG12D by CasRx abolishes the aberrant activation of downstream signaling induced by mutant KrasG12D and subsequently suppresses the tumor growth and improves the sensitivity of gemcitabine in PDAC. Additionally, delivering CasRx-gRNA via AAV8 into the orthotopic KrasG12D PDAC tumors substantially improves the survival of mice without obvious toxicity. Furthermore, targeting KrasG12D through CasRx suppresses the growth of PDAC PDXs. In conclusion, our study provides a proof-of-concept that CRISPR-CasRx can be utilized to target and silence mutant KrasG12D transcripts and therefore inhibit PDAC malignancy.

A Versatile Adeno-Associated Viral Vector Cross-Linking Platform Capable of Tuning Cellular Tropisms and Simultaneously Inducing Solid-Phase Gene Delivery

Developing gene carriers with improved affinities for target cells and the simultaneous diversification of their delivery modes will be pivotal for upgrading gene therapy technologies. In this study, a simple and versatile adeno-associated virus (AAV) conjugation platform using the cross-linker 3,3'-dithiobis(sulfosuccinimidyl propionate) (DTSSP) is proposed. Depending on the quantity of the DTSSP molecules, the AAV-DTSSP complexes could either be linked with the relevant biomolecules for altering cellular tropisms or further form a self-assembled AAV-DTSSP pellet capable of mimicking a polymeric gene delivery system. At lower quantities of DTSSP, the AAV-DTSSP complexes were conjugated with aminated l-fucose molecules, whose levels are typically upregulated in pancreatic cancer cells, resulting in enhanced gene delivery efficiencies in pancreatic cancer cells. At higher concentrations of DTSSP, visible solid forms of the AAV-DTSSP pellets were formed, and the AAV pellets demonstrated the capability to induce a localized, sustained gene expression pattern comparable to that of conventional biomaterial-based approaches. Thus, a multipurpose AAV cross-linking platform, which can enable AAV vector systems that are capable of altering cellular tropisms and simultaneously inducing solid-phase delivery, will provide crucial insights into vector design for further upgrading of gene delivery technologies.

An Engineered AAV6-Based Vaccine Induces High Cytolytic Anti-Tumor Activity by Directly Targeting DCs and Improves Ag Presentation

We have previously shown that an AAV6-based vaccine generates high levels of antigen-specific CD8+ T cells. Further modifications described here led to significantly increased levels of antigen-specific CD8+ and CD4+ T cells, enhanced formation of memory cells, and superior antigen-specific killing capacity in a murine model. By tracking reporter-gene-positive dendritic cells, we showed that they were directly targeted with modified AAV6 in vivo. Our vaccine's anti-cancer potential was evaluated with the antigen ovalbumin against a B16F10 melanoma cell line stably expressing ovalbumin. The vaccination showed superior protection in a murine model of metastatic melanoma. The vaccination significantly delayed solid tumor growth but did not completely prevent tumor development. We show that tumors in immunized mice escaped vaccine-induced killing by losing ovalbumin expression. The vaccine induced massive tumor infiltration with NK and CD8+ T cells with upregulated PD-1 expression. Thus, a vaccination of a combination of anti-PD-1 antibodies demonstrated significant improvement in the treatment efficacy. To summarize, we showed that a bioengineered AAV6-based vaccine elicits strong and long-lasting cellular and humoral responses against an encoded antigen. To increase AAV vaccine efficiency and mitigate tumor escape through antigen loss, we intended to target several antigens in combination with treatments targeting the tumor microenvironment.

Using a barcoded AAV capsid library to select for clinically relevant gene therapy vectors

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. 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. 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. 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.

A pipeline for rapidly generating genetically engineered mouse models of pancreatic cancer using in vivo CRISPR-Cas9-mediated somatic recombination

Genetically engineered mouse models (GEMMs) that recapitulate the major genetic drivers in pancreatic ductal adenocarcinoma (PDAC) have provided unprecedented insights into the pathogenesis of this lethal neoplasm. Nonetheless, generating an autochthonous model is an expensive, time consuming and labor intensive process, particularly when tissue specific expression or deletion of compound alleles are involved. In addition, many of the current PDAC GEMMs cause embryonic, pancreas-wide activation or loss of driver alleles, neither of which reflects the cognate human disease scenario. The advent of CRISPR/Cas9 based gene editing can potentially circumvent many of the aforementioned shortcomings of conventional breeding schema, but ensuring the efficiency of gene editing in vivo remains a challenge. Here we have developed a pipeline for generating PDAC GEMMs of complex genotypes with high efficiency using a single "workhorse" mouse strain expressing Cas9 in the adult pancreas under a p48 promoter. Using adeno-associated virus (AAV) mediated delivery of multiplexed guide RNAs (sgRNAs) to the adult murine pancreas of p48-Cre; LSL-Cas9 mice, we confirm our ability to express an oncogenic Kras G12D allele through homology-directed repair (HDR), in conjunction with CRISPR-induced disruption of cooperating alleles (Trp53, Lkb1 and Arid1A). The resulting GEMMs demonstrate a spectrum of precursor lesions (pancreatic intraepithelial neoplasia [PanIN] or Intraductal papillary mucinous neoplasm [IPMN] with eventual progression to PDAC. Next generation sequencing of the resulting murine PDAC confirms HDR of oncogenic KrasG12D allele at the endogenous locus, and insertion deletion ("indel") and frameshift mutations of targeted tumor suppressor alleles. By using a single "workhorse" mouse strain and optimal AAV serotype for in vivo gene editing with combination of driver alleles, we present a facile autochthonous platform for interrogation of the PDAC genome.

Evaluation of AAV-mediated delivery of shRNA to target basal-like breast cancer genetic vulnerabilities

Adeno-associated viral vectors (AAV) for gene therapy applications are gaining momentum, with more therapies moving into later stages of clinical development and towards market approval, namely for cancer therapy. The development of cytotoxic vectors is often hampered by side effects arising when non-target cells are infected, and their production can be hindered by toxic effects of the transgene on the producing cell lines. In this study, we evaluated the potential of rAAV-mediated delivery of short hairpin RNAs (shRNA) to target basal-like breast cancer genetic vulnerabilities. Our results show that by optimizing the stoichiometry of the plasmids upon transfection and time of harvest, it is possible to increase the viral titers and quality. All rAAV-shRNA vectors obtained efficiently transduced the BLBC cell lines MDA-MB-468 and HCC1954. In MDA-MB-468, transduction with rAAV-shRNA vector targeting PSMA2 was associated with significant decrease in cell viability and apoptosis induction. Importantly, rAAV2-PSMA2 also slowed tumor growth in a BLBC mouse xenograft model, thus potentially representing a therapeutic strategy against this type of cancer.

Gene Therapy for Pancreatic Diseases: Current Status

The pancreas is a key organ involved in digestion and endocrine functions in the body. The major diseases of the pancreas include pancreatitis, pancreatic cancer, cystic diseases, pancreatic divisum, islet cell tumors, endocrine tumors, diabetes mellitus, and pancreatic pain induced by these diseases. While various therapeutic methodologies have been established to date, however, the improvement of conventional treatments and establishment of novel therapies are essential to improve the efficacy. For example, conventional therapeutic options, including chemotherapy, are not effective against pancreatic cancer, and despite improvements in the last decade, the mortality rate has not declined and is estimated to become the second cause of cancer-related deaths by 2030. Therefore, continuous efforts focus on the development of novel therapeutic options. In this review, we will summarize the progress toward the development of gene therapies for pancreatic diseases, with an emphasis on recent preclinical studies and clinical trials. We aim to identify new areas for improvement of the current methodologies and new strategies that will lead to safe and effective gene therapeutic approaches in pancreatic diseases.

Improvement of Photoreceptor Targeting via Intravitreal Delivery in Mouse and Human Retina Using Combinatory rAAV2 Capsid Mutant Vectors

Purpose

Effective intravitreal gene delivery to cells of the central retina (i.e., photoreceptors) would be of substantial benefit for treating patients with retinal diseases, such as achromatopsia, where retinal detachment from a subretinal may be harmful. Previous studies demonstrated that mutation of the recombinant adeno-associated virus (rAAV) capsid through introduction of peptide insertions or amino acid substitutions dramatically alters vector tropism. Herein, we evaluate the photoreceptor transduction efficiency of three rAAV2/2-based capsid mutant vectors: rAAV2/2[7m8], rAAV2/2[QuadYF+TV], and a chimeric vector incorporating both mutations (termed rAAV2/2[MAX]) following intravitreal delivery in mice. Furthermore, we evaluate the transduction efficiency of rAAV2/2[MAX] using explanted human central retinal samples to address clinical translatability.

Methods

Vectors containing a GFP or mCherry reporter gene were intravitreally injected into C57BL/6J or Nrl-EGFP mice, respectively. Transduction was assessed in vivo utilizing a custom multiline confocal scanning laser ophthalmoscope. Injected Nrl-EGFP mouse retinas were used to quantify transduced photoreceptors using flow cytometry. Postmortem human retinal tissue was cultured following administration of rAAV2/2[MAX]. C57BL/6J retinas and human explants were cryosectioned to determine vector tropism.

Results

The chimeric vector rAAV2/2[MAX] transduced significantly higher proportions of the retina than did either single mutant serotypes following intravitreal delivery in murine retina, including inner retinal cells and photoreceptors. Vector rAAV2[MAX] demonstrated transduction of human photoreceptors and ganglion cells.

Conclusions

Transduction observed via rAAV2/2[MAX] indicates that combining mutations with complementary mechanisms of action in a single vector results in enhanced transduction. rAAV2/2[MAX] also presented the ability to transduce human photoreceptors and ganglion cells, indicating potential for efficient intravitreal vector delivery.

Safety and Efficacy of AAV Retrograde Pancreatic Ductal Gene Delivery in Normal and Pancreatic Cancer Mice

Recombinant adeno-associated virus (rAAV)-mediated gene delivery shows promise to transduce the pancreas, but safety/efficacy in a neoplastic context is not well established. To identify an ideal AAV serotype, route, and vector dose and assess safety, we have investigated the use of three AAV serotypes (6, 8, and 9) expressing GFP in a self-complementary (sc) AAV vector under an EF1α promoter (scAAV.GFP) following systemic or retrograde pancreatic intraductal delivery. Systemic delivery of scAAV9.GFP transduced the pancreas with high efficiency, but gene expression did not exceed >45% with the highest dose, 5 × 10¹² viral genomes (vg). Intraductal delivery of 1 × 10¹¹ vg scAAV6.GFP transduced acini, ductal cells, and islet cells with >50%, ∼48%, and >80% efficiency, respectively, and >80% pancreatic transduction was achieved with 5 × 10¹¹ vg. In a Kras^G12D-driven pancreatic cancer mouse model, intraductal delivery of scAAV6.GFP targeted acini, epithelial, and stromal cells and exhibited persistent gene expression 5 months post-delivery. In normal mice, intraductal delivery induced a transient increase in serum amylase/lipase that resolved within a day of infusion with no sustained pancreatic inflammation or fibrosis. Similarly, in PDAC mice, intraductal delivery did not increase pancreatic intraepithelial neoplasia progression/fibrosis. Our study demonstrates that scAAV6 targets the pancreas/neoplasm efficiently and safely via retrograde pancreatic intraductal delivery.