Adeno-associated virus vectors: potential applications for cancer gene therapy

Augmenting cancer treatment by protein and gene delivery continues to gain momentum based on success in animal models. The primary hurdle of fully exploiting the arsenal of molecular targets and therapeutic transgenes continues to be efficient delivery. Vectors based on adeno-associated virus (AAV) are of particular interest as they are capable of inducing transgene expression in a broad range of tissues for a relatively long time without stimulation of a cell-mediated immune response. Perhaps the most important attribute of AAV vectors is their safety profile in phase I clinical trials ranging from CF to Parkinson’s disease. The utility of AAV vectors as a gene delivery agent in cancer therapy is showing promise in preclinical studies. In this review, we will focus on the basic biology of AAV as well as recent progress in the use of this vector in cancer gene therapy

Reproducibility of left atrial ablation with high-intensity focused ultrasound energy in a calf model

ObjectiveAchieving transmural tissue ablation might be necessary for successful treatment of atrial fibrillation. The purpose of this study was to evaluate the reproducibility of transmural left atrial ablation using a high-intensity focused ultrasound energy system in a calf model.MethodsNine heparinized bovines underwent a beating-heart left atrial ablation with a single application of the high-intensity focused ultrasound device. All animals were acutely killed, and the left atrium was fixed in formalin. Protocolized histological sections (5 μm) were obtained throughout each lesion and prepared with Masson trichrome and hematoxylin and eosin staining. Measurements were performed on a total of 359 slides from the 9 lesions. In addition, fresh left atrial tissues from 18 unused human donor hearts that did not meet the criteria for cardiac transplantation were measured at the site where the high-intensity focused ultrasound device is normally applied.ResultsCalf left atrial thickness ranged between 2.5 and 20.1 mm, with a mean of 9.10 mm. High-intensity focused ultrasound ablation consistently produced a 100% transmural lesion in left atrial thickness up to 6 mm. In addition, a transmural lesion was observed in 91% of tissues that were up to 10 mm thick and in 85% that were up to 15 mm thick. Human left atrial thickness ranged between 1.2 to 6 mm, with a mean of 3.7 mm.ConclusionsCalf left atrial thickness in this study was greater than human left atrial thickness. Human left atrial thickness is generally less than 6 mm, and in this range high-intensity focused ultrasound ablation achieved 100% transmurality. These histological results might correlate with a high success rate of atrial fibrillation ablation by using the high-intensity focused ultrasound system

Adeno-Associated Viral Vectors Based on Serotype 3b Use Components of the Fibroblast Growth Factor Receptor Signaling Complex for Efficient Transduction

Adeno-associated virus type 3b (AAV3b) has been largely ignored by gene therapists because of the inability of vectors based on this serotype to transduce target tissues efficiently. Here we describe a phenomenon unique to AAV3b in that vectors based on this serotype mediate enhanced transduction in the presence of heparin. Among the many biological functions attributed to heparin, its interaction with, and ability to regulate, several growth factors (GFs) and growth factor receptors (GFRs) has been well characterized. Using GFR-overexpressing cell lines, soluble GFs and heparins, as well as specific GFR inhibitors, we have demonstrated a requirement for fibroblast growth factor receptor-2 (FGFR2) and FGF1 in the heparin-mediated augmentation of AAV3b vector transduction. In contrast to AAV2, we establish that heparin can be used as an adjunct with AAV3b to further increase transduction in a variety of cells and target tissues, additionally suggesting that AAV3b may be an attractive viral vector for clinical use during procedures in which heparin is used. In summary, AAV3b exhibits FGFR2-dependent, markedly enhanced transduction efficiency in the presence of heparin and FGFs, which could make it a useful vector for gene therapy in a variety of human diseases

Microgravity induces proteomics changes involved in endoplasmic reticulum stress and mitochondrial protection

On Earth, biological systems have evolved in response to environmental stressors, interactions dictated by physical forces that include gravity. The absence of gravity is an extreme stressor and the impact of its absence on biological systems is ill-defined. Astronauts who have spent extended time under conditions of minimal gravity (microgravity) experience an array of biological alterations, including perturbations in cardiovascular function. We hypothesized that physiological perturbations in cardiac function in microgravity may be a consequence of alterations in molecular and organellar dynamics within the cellular milieu of cardiomyocytes. We used a combination of mass spectrometry-based approaches to compare the relative abundance and turnover rates of 848 and 196 proteins, respectively, in rat neonatal cardiomyocytes exposed to simulated microgravity or normal gravity. Gene functional enrichment analysis of these data suggested that the protein content and function of the mitochondria, ribosomes, and endoplasmic reticulum were differentially modulated in microgravity. We confirmed experimentally that in microgravity protein synthesis was decreased while apoptosis, cell viability, and protein degradation were largely unaffected. These data support our conclusion that in microgravity cardiomyocytes attempt to maintain mitochondrial homeostasis at the expense of protein synthesis. The overall response to this stress may culminate in cardiac muscle atrophy

Hypoxia decreases creatine uptake in cardiomyocytes, while creatine supplementation enhances HIF activation

Abstract Creatine (Cr), phosphocreatine (PCr), and creatine kinases (CK) comprise an energy shuttle linking ATP production in mitochondria with cellular consumption sites. Myocytes cannot synthesize Cr: these cells depend on uptake across the cell membrane by a specialized creatine transporter (CrT) to maintain intracellular Cr levels. Hypoxia interferes with energy metabolism, including the activity of the creatine energy shuttle, and therefore affects intracellular ATP and PCr levels. Here, we report that exposing cultured cardiomyocytes to low oxygen levels rapidly diminishes Cr transport by decreasing V max and K m. Pharmacological activation of AMP‐activated kinase (AMPK) abrogated the reduction in Cr transport caused by hypoxia. Cr supplementation increases ATP and PCr content in cardiomyocytes subjected to hypoxia, while also significantly augmenting the cellular adaptive response to hypoxia mediated by HIF‐1 activation. Our results indicate that: (1) hypoxia reduces Cr transport in cardiomyocytes in culture, (2) the cytoprotective effects of Cr supplementation are related to enhanced adaptive physiological responses to hypoxia mediated by HIF‐1, and (3) Cr supplementation increases the cellular ATP and PCr content in RNCMs exposed to hypoxia

X-Linked Inhibitor of Apoptosis Protein-Mediated Attenuation of Apoptosis, Using a Novel Cardiac-Enhanced Adeno-Associated Viral Vector

Successful amelioration of cardiac dysfunction and heart failure through gene therapy approaches will require a transgene effective at attenuating myocardial injury, and subsequent remodeling, using an efficient and safe delivery vehicle. Our laboratory has established a well-curated, high-quality repository of human myocardial tissues that we use as a discovery engine to identify putative therapeutic transgene targets, as well as to better understand the molecular basis of human heart failure. By using this rare resource we were able to examine age- and sex-matched left ventricular samples from (1) end-stage failing human hearts and (2) nonfailing human hearts and were able to identify the X-linked inhibitor of apoptosis protein (XIAP) as a novel target for treating cardiac dysfunction. We demonstrate that XIAP is diminished in failing human hearts, indicating that this potent inhibitor of apoptosis may be central in protecting the human heart from cellular injury culminating in heart failure. Efforts to ameliorate heart failure through delivery of XIAP compelled the design of a novel adeno-associated viral (AAV) vector, termed SASTG, that achieves highly efficient transduction in mouse heart and in cultured neonatal rat cardiomyocytes. Increased XIAP expression achieved with the SASTG vector inhibits caspase-3/7 activity in neonatal cardiomyocytes after induction of apoptosis through three common cardiac stresses: protein kinase C-γ inhibition, hypoxia, or β-adrenergic receptor agonist. These studies demonstrate the potential benefit of XIAP to correct heart failure after highly efficient delivery to the heart with the rationally designed SASTG AAV vector

Proteomic and phosphoproteomic characterization of cardiovascular tissues after long term exposure to simulated space radiation

Introduction: It may take decades to develop cardiovascular dysfunction following exposure to high doses of ionizing radiation from medical therapy or from nuclear accidents. Since astronauts may be exposed continually to a complex space radiation environment unlike that experienced on Earth, it is unresolved whether there is a risk to cardiovascular health during long-term space exploration missions. Previously, we have described that mice exposed to a single dose of simplified Galactic Cosmic Ray (GCR 5-ion) develop cardiovascular dysfunction by 12 months post-radiation. Methods: To investigate the biological basis of this dysfunction, here we performed a quantitative mass spectrometry-based proteomics analysis of heart tissue (proteome and phosphoproteome) and plasma (proteome only) from these mice at 8 months post-radiation.Results: Differentially expressed proteins (DEPs) for irradiated versus sham irradiated samples (fold-change ≥1.2 and an adjusted p-value of ≤0.05) were identified for each proteomics data set. For the heart proteome, there were 87 significant DEPs (11 upregulated and 76 downregulated); for the heart phosphoproteome, there were 60 significant differentially phosphorylated peptides (17 upregulated and 43 downregulated); and for the plasma proteome, there was only one upregulated protein. A Gene Set Enrichment Analysis (GSEA) technique that assesses canonical pathways from BIOCARTA, KEGG, PID, REACTOME, and WikiPathways revealed significant perturbation in pathways in each data set. For the heart proteome, 166 pathways were significantly altered (36 upregulated and 130 downregulated); for the plasma proteome, there were 73 pathways significantly altered (25 upregulated and 48 downregulated); and for the phosphoproteome, there were 223 pathways significantly affected at 0.1 adjusted p-value cutoff. Pathways related to inflammation were the most highly perturbed in the heart and plasma. In line with sustained inflammation, neutrophil extracellular traps (NETs) were demonstrated to be increased in GCR 5-ion irradiated hearts at 12-month post irradiation. NETs play a fundamental role in combating bacterial pathogens, modulating inflammatory responses, inflicting damage on healthy tissues, and escalating vascular thrombosis. Discussion: These findings suggest that a single exposure to GCR5-ion results in long-lasting changes in the proteome and that these proteomic changes can potentiate acute and chronic health issues for astronauts, such as what we have previously described with late cardiac dysfunction in these mice

Phase 1 Gene Therapy for Duchenne Muscular Dystrophy Using a Translational Optimized AAV Vector

Efficient and widespread gene transfer is required for successful treatment of Duchenne muscular dystrophy (DMD). Here, we performed the first clinical trial using a chimeric adeno-associated virus (AAV) capsid variant (designated AAV2.5) derived from a rational design strategy. AAV2.5 was generated from the AAV2 capsid with five mutations from AAV1. The novel chimeric vector combines the improved muscle transduction capacity of AAV1 with reduced antigenic crossreactivity against both parental serotypes, while keeping the AAV2 receptor binding. In a randomized double-blind placebo-controlled phase I clinical study in DMD boys, AAV2.5 vector was injected into the bicep muscle in one arm, with saline control in the contralateral arm. A subset of patients received AAV empty capsid instead of saline in an effort to distinguish an immune response to vector versus minidystrophin transgene. Recombinant AAV genomes were detected in all patients with up to 2.56 vector copies per diploid genome. There was no cellular immune response to AAV2.5 capsid. This trial established that rationally designed AAV2.5 vector was safe and well tolerated, lays the foundation of customizing AAV vectors that best suit the clinical objective (e.g., limb infusion gene delivery) and should usher in the next generation of viral delivery systems for human gene transfer

Video analysis of ex vivo beating hearts during preservation on the TransMedics® organ care system

BackgroundReliable biomarkers for assessing the viability of the donor hearts undergoing ex vivo perfusion remain elusive. A unique feature of normothermic ex vivo perfusion on the TransMedics® Organ Care System (OCS™) is that the donor heart is maintained in a beating state throughout the preservation period. We applied a video algorithm for an in vivo assessment of cardiac kinematics, video kinematic evaluation (Vi.Ki.E.), to the donor hearts undergoing ex vivo perfusion on the OCS™ to assess the feasibility of applying this algorithm in this setting.MethodsHealthy donor porcine hearts (n = 6) were procured from Yucatan pigs and underwent 2 h of normothermic ex vivo perfusion on the OCS™ device. During the preservation period, serial high-resolution videos were captured at 30 frames per second. Using Vi.Ki.E., we assessed the force, energy, contractility, and trajectory parameters of each heart.ResultsThere were no significant changes in any of the measured parameters of the heart on the OCS™ device over time as judged by linear regression analysis. Importantly, there were no significant changes in contractility during the duration of the preservation period (time 0–30 min, 918 ± 430 px/s; time 31–60 min, 1,386 ± 603 px/s; time 61–90 min, 1,299 ± 617 px/s; time 91–120 min, 1,535 ± 728 px/s). Similarly, there were no significant changes in the force, energy, or trajectory parameters. Post-transplantation echocardiograms demonstrated robust contractility of each allograft.ConclusionVi.Ki.E. assessment of the donor hearts undergoing ex vivo perfusion is feasible on the TransMedics OCS™, and we observed that the donor hearts maintain steady kinematic measurements throughout the duration

Genetic mechanisms of critical illness in COVID-19.

Host-mediated lung inflammation is present1, and drives mortality2, in the critical illness caused by coronavirus disease 2019 (COVID-19). Host genetic variants associated with critical illness may identify mechanistic targets for therapeutic development3. Here we report the results of the GenOMICC (Genetics Of Mortality In Critical Care) genome-wide association study in 2,244 critically ill patients with COVID-19 from 208 UK intensive care units. We have identified and replicated the following new genome-wide significant associations: on chromosome 12q24.13 (rs10735079, P = 1.65 × 10-8) in a gene cluster that encodes antiviral restriction enzyme activators (OAS1, OAS2 and OAS3); on chromosome 19p13.2 (rs74956615, P = 2.3 × 10-8) near the gene that encodes tyrosine kinase 2 (TYK2); on chromosome 19p13.3 (rs2109069, P = 3.98 ×  10-12) within the gene that encodes dipeptidyl peptidase 9 (DPP9); and on chromosome 21q22.1 (rs2236757, P = 4.99 × 10-8) in the interferon receptor gene IFNAR2. We identified potential targets for repurposing of licensed medications: using Mendelian randomization, we found evidence that low expression of IFNAR2, or high expression of TYK2, are associated with life-threatening disease; and transcriptome-wide association in lung tissue revealed that high expression of the monocyte-macrophage chemotactic receptor CCR2 is associated with severe COVID-19. Our results identify robust genetic signals relating to key host antiviral defence mechanisms and mediators of inflammatory organ damage in COVID-19. Both mechanisms may be amenable to targeted treatment with existing drugs. However, large-scale randomized clinical trials will be essential before any change to clinical practice