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1.  Human Parainfluenza Virus Type 2 Vector Induces Dendritic Cell Maturation Without Viral RNA Replication/Transcription 
Human Gene Therapy  2013;24(7):683-691.
The dendritic cell (DC), a most potent antigen-presenting cell, plays a key role in vaccine therapy against infectious diseases and malignant tumors. Although advantages of viral vectors for vaccine therapy have been reported, potential risks for adverse effects prevent them from being licensed for clinical use. Human parainfluenza virus type 2 (hPIV2), one of the members of the Paramyxoviridae family, is a nonsegmented and negative-stranded RNA virus. We have developed a reverse genetics system for the production of infectious hPIV2 lacking the F gene (hPIV2ΔF), wherein various advantages for vaccine therapy exist, such as cytoplasmic replication/transcription, nontransmissible infectivity, and extremely high transduction efficacy in various types of target cells. Here we demonstrate that hPIV2ΔF shows high transduction efficiency in human DCs, while not so high in mouse DCs. In addition, hPIV2ΔF sufficiently induces maturation of both human and murine DCs, and the maturation state of both human and murine DCs is almost equivalent to that induced by lipopolysaccharide. Moreover, alkylating agent β-propiolactone-inactivated hPIV2ΔF (BPL-hPIV2ΔF) elicits DC maturation without viral replication/transcription. These results suggest that hPIV2ΔF may be a useful tool for vaccine therapy as a novel type of paramyxoviral vector, which is single-round infectious vector and has potential adjuvant activity.
Using a reverse genetics approach, Hara and colleagues generate a human parainfluenza vector that lacks the F gene. These investigators show that the vector has high transduction efficiency in both mouse and human dendritic cells (DCs) and can trigger DC maturation in the absence of viral replication/transcription.
PMCID: PMC3719437  PMID: 23790317
2.  Granulocyte-Macrophage Colony-Stimulating Factor-Armed Oncolytic Measles Virus Is an Effective Therapeutic Cancer Vaccine 
Human Gene Therapy  2013;24(7):644-654.
Oncolytic measles viruses (MV) derived from the live attenuated vaccine strain have been engineered for increased antitumor activity, and are currently under investigation in clinical phase 1 trials. Approaches with other viral vectors have shown that insertion of immunomodulatory transgenes enhances the therapeutic potency. In this study, we engineered MV for expression of the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF). For the first time, therapeutic efficacy and adaptive immune response in the context of MV oncolysis could be evaluated in the previously established immunocompetent murine colon adenocarcinoma model MC38cea. MC38cea cells express the human carcinoembryonic antigen (CEA), allowing for infection with retargeted MV. Intratumoral application of MV-GMCSF significantly delayed tumor progression and prolonged median overall survival compared with control virus-treated mice. Importantly, more than one-third of mice treated with MV-GMCSF showed complete tumor remission and rejected successive tumor reengraftment, demonstrating robust long-term protection. An enhanced cell-mediated tumor-specific immune response could be detected by lactate dehydrogenase assay and interferon-γ enzyme-linked immunospot assay. Furthermore, MV-GMCSF treatment correlated with increased abundance of tumor-infiltrating CD3+ lymphocytes analyzed by quantitative microscopy of tumor sections. These findings underline the potential of oncolytic, GM-CSF-expressing MV as an effective therapeutic cancer vaccine actively recruiting adaptive immune responses for enhanced therapeutic impact and tumor elimination. Thus, the treatment benefit of this combined immunovirotherapy approach has direct implications for future clinical trials.
Grossardt and colleagues engineer measles viruses (MV) for expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) and evaluate its therapeutic efficacy and immune response in an established immunocompetent murine colon adenocarcinoma model. Intratumoral application of MV-GMCSF delayed tumor progression and significantly prolonged median overall survival, with more than one third of mice showing complete tumor remission as well as resistance to tumor re-engraftment.
PMCID: PMC3719441  PMID: 23642239
3.  Bone-Marrow-Derived Mesenchymal Stem Cells Promote Proliferation and Neuronal Differentiation of Niemann–Pick Type C Mouse Neural Stem Cells by Upregulation and Secretion of CCL2 
Human Gene Therapy  2013;24(7):655-669.
Niemann–Pick type C (NP-C) disease is a neurodegenerative disorder characterized neuropathologically by ballooned neurons distended with lipid storage and widespread neuronal loss. Neural stem cells (NSC) derived from NP-C disease models have decreased ability for self-renewal and neuronal differentiation. Investigation of neurogenesis in the adult brain has suggested that NP-C disease can be overcome, or at least ameliorated, by the generation of new neurons. Bone-marrow-derived mesenchymal stem cells (BM-MSCs) are regarded as potential candidates for use in the treatment of neurodegenerative disorders because of their ability to promote neurogenesis. The underlying mechanisms of BM-MSC-induced promotion of neurogenesis, however, have not been resolved. The aim of the present study was to examine the mechanism of neurogenesis by BM-MSCs in NP-C disease. Coculture of embryonic NSCs from NP-C mice that exhibit impaired ability for self-renewal and decreased rates of neuronal differentiation with BM-MSCs resulted in an enhanced capacity for self-renewal and an increased ability for differentiation into neurons or oligodendrocytes. In addition, results of in vivo studies have demonstrated that transplantation of intracerebral BM-MSCs resulted in stimulated proliferation and neuronal differentiation of NSCs within the subventricular zone. Of particular interest, enhanced proliferation and neuronal differentiation of endogenous NP-C mouse NSCs showed an association with elevated release of the chemokine (C-C motif) ligand 2 (CCL2) from BM-MSCs. These effects suggest that soluble CCL2 derived from BM-MSCs can modulate endogenous NP-C NSCs, resulting in their improved proliferation and neuronal differentiation in mice.
Using a murine model of Nieman–Pick type C disease, Lee and colleagues demonstrate that transplantation of bone-marrow-derived mesenchymal stem cells (BM-MSCs) into the sub ventricular zone (SVZ) results in enhanced self-renewal, proliferation, and neuronal differentiation of neural stem cells (NSCs) via a CCL2-mediated mechanism.
PMCID: PMC3719464  PMID: 23659480
4.  Exon Skipping as a Therapeutic Strategy Applied to an RYR1 Mutation with Pseudo-Exon Inclusion Causing a Severe Core Myopathy 
Human Gene Therapy  2013;24(7):702-713.
Central core disease is a myopathy often arising from mutations in the type 1 ryanodine receptor (RYR1) gene, encoding the sarcoplasmic reticulum calcium release channel RyR1. No treatment is currently available for this disease. We studied the pathological situation of a severely affected child with two recessive mutations, which resulted in a massive reduction in the amount of RyR1. The paternal mutation induced the inclusion of a new in-frame pseudo-exon in RyR1 mRNA that resulted in the insertion of additional amino acids leading to the instability of the protein. We hypothesized that skipping this additional exon would be sufficient to restore RyR1 expression and to normalize calcium releases. We therefore developed U7-AON lentiviral vectors to force exon skipping on affected primary muscle cells. The efficiency of the exon skipping was evaluated at the mRNA level, at the protein level, and at the functional level using calcium imaging. In these affected cells, we observed a decreased inclusion of the pseudo-exon, an increased RyR1 protein expression, and a restoration of calcium releases of normal amplitude either upon direct RyR1 stimulation or in response to membrane depolarization. This study is the first demonstration of the potential of exon-skipping strategy for the therapy of central core disease, from the molecular to the functional level.
Rendu and colleagues identify a patient with a recessive central core myopathy in which one of the disease-causing mutations results in pseudo-exon inclusion in the type 1 ryanodine receptor calcium channel mRNA. They demonstrate that a lentivirus vector expressing a U7 snRNA-linked antisense sequence can induce skipping of the pseudo-exon in primary patient myocytes, resulting in rescue of ryanodine receptor expression and correction of abnormal calcium release.
PMCID: PMC3719469  PMID: 23805838
6.  Long-Term Robust Myocardial Transduction of the Dog Heart from a Peripheral Vein by Adeno-Associated Virus Serotype-8 
Human Gene Therapy  2013;24(6):584-594.
Molecular intervention using noninvasive myocardial gene transfer holds great promise for treating heart diseases. Robust cardiac transduction from peripheral vein injection has been achieved in rodents using adeno-associated virus (AAV) serotype-9 (AAV-9). However, a similar approach has failed to transduce the heart in dogs, a commonly used large animal model for heart diseases. To develop an effective noninvasive method to deliver exogenous genes to the dog heart, we employed an AAV-8 vector that expresses human placental alkaline phosphatase reporter gene under the transcriptional regulation of the Rous sarcoma virus promoter. Vectors were delivered to three neonatal dogs at the doses of 1.35×1014, 7.14×1014, and 9.06×1014 viral genome particles/kg body weight via the jugular vein. Transduction efficiency and overall safety were evaluated at 1.5, 2.5, and 12 months postinjection. AAV delivery was well tolerated and dog growth was normal. Blood chemistry and internal organ histology were unremarkable. Widespread skeletal muscle transduction was observed in all dogs without T-cell infiltration. Encouragingly, whole heart myocardial transduction was achieved in two dogs that received higher doses and cardiac expression lasted for at least 1 year. In summary, peripheral vein AAV-8 injection may represent a simple heart gene transfer method in large mammals. Further optimization of this gene delivery strategy may open the door for a readily applicable gene therapy method to treat many heart diseases.
Pan and colleagues administer, via the jugular vein, adeno-associated virus serotype 8 (AAV8) vector expressing a human placental alkaline phosphatase reporter gene under the control of the Rous sarcoma virus promoter to three neonatal dogs at doses of 1.35 × 1014, 7.14 × 1014, and 9.06 × 1014 viral genome particles/kg body weight. Using this approach, they observe widespread skeletal muscle transduction in all dogs without T cell infiltration. Interestingly, whole heart myocardial transduction was achieved in the two dogs that received the highest doses, and this expression lasted for at least 1 year.
PMCID: PMC3689160  PMID: 23551085
7.  New Frontier in Regenerative Medicine: Site-Specific Gene Correction in Patient-Specific Induced Pluripotent Stem Cells 
Human Gene Therapy  2013;24(6):571-583.
Advances in cell and gene therapy are opening up new avenues for regenerative medicine. Because of their acquired pluripotency, human induced pluripotent stem cells (hiPSCs) are a promising source of autologous cells for regenerative medicine. They show unlimited self-renewal while retaining the ability, in principle, to differentiate into any cell type of the human body. Since Yamanaka and colleagues first reported the generation of hiPSCs in 2007, significant efforts have been made to understand the reprogramming process and to generate hiPSCs with potential for clinical use. On the other hand, the development of gene-editing platforms to increase homologous recombination efficiency, namely DNA nucleases (zinc finger nucleases, TAL effector nucleases, and meganucleases), is making the application of locus-specific gene therapy in human cells an achievable goal. The generation of patient-specific hiPSC, together with gene correction by homologous recombination, will potentially allow for their clinical application in the near future. In fact, reports have shown targeted gene correction through DNA-Nucleases in patient-specific hiPSCs. Various technologies have been described to reprogram patient cells and to correct these patient hiPSCs. However, no approach has been clearly more efficient and safer than the others. In addition, there are still significant challenges for the clinical application of these technologies, such as inefficient differentiation protocols, genetic instability resulting from the reprogramming process and hiPSC culture itself, the efficacy and specificity of the engineered DNA nucleases, and the overall homologous recombination efficiency. To summarize advances in the generation of gene corrected patient-specific hiPSCs, this review focuses on the available technological platforms, including their strengths and limitations regarding future therapeutic use of gene-corrected hiPSCs.
PMCID: PMC3689164  PMID: 23675640
8.  Direct and Retrograde Transduction of Nigral Neurons with AAV6, 8, and 9 and Intraneuronal Persistence of Viral Particles 
Human Gene Therapy  2013;24(6):613-629.
Recombinant adeno-associated viral (AAV) vectors of serotypes 6, 8, and 9 were characterized as tools for gene delivery to dopaminergic neurons in the substantia nigra for future gene therapeutic applications in Parkinson's disease. While vectors of all three serotypes transduced nigral dopaminergic neurons with equal efficiency when directly injected to the substantia nigra, AAV6 was clearly superior to AAV8 and AAV9 for retrograde transduction of nigral neurons after striatal delivery. For sequential transduction of nigral dopaminergic neurons, the combination of AAV9 with AAV6 proved to be more powerful than AAV8 with AAV6 or repeated AAV6 administration. Surprisingly, single-stranded viral genomes persisted in nigral dopaminergic neurons within cell bodies and axon terminals in the striatum, and intact assembled AAV capsid was enriched in nuclei of nigral neurons, 4 weeks after virus injections to the substantia nigra. 6-Hydroxydopamine (6-OHDA)–induced degeneration of dopaminergic neurons in the substantia nigra reduced the number of viral genomes in the striatum, in line with viral genome persistence in axon terminals. However, 6-OHDA–induced axonal degeneration did not induce any transsynaptic spread of AAV infection in the striatum. Therefore, the potential presence of viral particles in axons may not represent an important safety issue for AAV gene therapy applications in neurodegenerative diseases.
Löw and colleagues characterize adeno-associated viral (AAV) vector serotypes 6, 8, and 9 as tools for gene delivery to dopaminergic neurons in the substantia nigra. All three serotypes comparably transduce target cells when injected directly into the substantia nigra. AAV6 proved superior for retrograde transduction after striatal delivery, whereas combining AAV9 with AAV6 is most effective in sequential transduction regimens. In addition, although singlestranded viral genomes persist in neuronal cell bodies and axon terminals, induced degeneration does not induce transsynaptic transgene spread.
PMCID: PMC3689167  PMID: 23600720
9.  Gene Therapy Briefs 
Human Gene Therapy  2013;24(6):565-567.
PMCID: PMC3689177  PMID: 23777463
10.  Phase I/II Trial of Adeno-Associated Virus–Mediated Alpha-Glucosidase Gene Therapy to the Diaphragm for Chronic Respiratory Failure in Pompe Disease: Initial Safety and Ventilatory Outcomes 
Human Gene Therapy  2013;24(6):630-640.
Pompe disease is an inherited neuromuscular disease caused by deficiency of lysosomal acid alpha-glucosidase (GAA) leading to glycogen accumulation in muscle and motoneurons. Cardiopulmonary failure in infancy leads to early mortality, and GAA enzyme replacement therapy (ERT) results in improved survival, reduction of cardiac hypertrophy, and developmental gains. However, many children have progressive ventilatory insufficiency and need additional support. Preclinical work shows that gene transfer restores phrenic neural activity and corrects ventilatory deficits. Here we present 180-day safety and ventilatory outcomes for five ventilator-dependent children in a phase I/II clinical trial of AAV-mediated GAA gene therapy (rAAV1-hGAA) following intradiaphragmatic delivery. We assessed whether rAAV1-hGAA results in acceptable safety outcomes and detectable functional changes, using general safety measures, immunological studies, and pulmonary functional testing. All subjects required chronic, full-time mechanical ventilation because of respiratory failure that was unresponsive to both ERT and preoperative muscle-conditioning exercises. After receiving a dose of either 1×1012 vg (n=3) or 5×1012 vg (n=2) of rAAV1-hGAA, the subjects' unassisted tidal volume was significantly larger (median [interquartile range] 28.8% increase [15.2–35.2], p<0.05). Further, most patients tolerated appreciably longer periods of unassisted breathing (425% increase [103–851], p=0.08). Gene transfer did not improve maximal inspiratory pressure. Expected levels of circulating antibodies and no T-cell-mediated immune responses to the vector (capsids) were observed. One subject demonstrated a slight increase in anti-GAA antibody that was not considered clinically significant. These results indicate that rAAV1-hGAA was safe and may lead to modest improvements in volitional ventilatory performance measures. Evaluation of the next five patients will determine whether earlier intervention can further enhance the functional benefit.
Smith and colleagues present 180-day safety and ventilatory outcomes for five ventilator-dependent children in a phase 1/2 clinical trial of adeno-associated viral (AAV) vector-mediated gene therapy for lysosomal acid α-glucosidase (GAA) deficiency (rAAV1-hGAA) after intradiaphragmatic delivery. rAAV1-hGAA treatment was safe and may lead to modest improvements in volitional ventilatory performance measures.
PMCID: PMC3689178  PMID: 23570273
11.  Suppression of Nicotine-Induced Pathophysiology by an Adenovirus Hexon-Based Antinicotine Vaccine 
Human Gene Therapy  2013;24(6):595-603.
Despite antismoking campaigns, cigarette smoking remains a pervasive addiction with significant societal impact, accounting for one of every five deaths. Smoking cessation therapies to help smokers quit are ineffective with a high recidivism rate. With the knowledge that nicotine is the principal addictive compound of cigarettes, we have developed an antismoking vaccine based on the highly immunogenic properties of the hexon protein purified from the serotype 5 adenovirus (Ad) capsid. We hypothesized that an effective antinicotine vaccine could be based on coupling the nicotine hapten AM1 to purified Ad hexon protein. To assess this, AM1 was conjugated to hexon purified from serotype 5 Ad to produce the HexonAM1 vaccine. C57Bl/6 mice were sensitized by 10 daily nicotine administrations (0.5 mg/kg, subcutaneous) to render the mice addicted to nicotine. Control groups were sensitized to phosphate-buffered saline (PBS). The mice were then immunized with HexonAM1 (4 μg, intramuscular) at 0, 3, and 6 weeks. By 6 weeks, the HexonAM1-vaccinated mice had serum antinicotine antibody titers of 1.1×106±7.6×104. To demonstrate that these high antinicotine titers were sufficient to suppress the effects of nicotine, HexonAM1-vaccinated mice were evaluated for nicotine-induced hypoactive behavior with nicotine challenges (0.5 mg/kg wt) over 5 weeks. In all challenges, the HexonAM1-vaccinated mice behaved similar to PBS-challenged naive mice. These data demonstrate that a vaccine comprised of a nicotine analog coupled to Ad hexon can evoke a high level of antinicotine antibodies sufficient to inhibit nicotine-induced behavior. The HexonAM1 vaccine represents a platform paradigm for vaccines against small molecules.
Rosenberg and colleagues describe an antinicotine vaccine comprising a nicotine analog (AM1) coupled to hexon protein purified from the adenovirus serotype 5 capsid. They show that this vaccine can elicit high levels of antinicotine antibodies in vivo and that this leads to significant inhibition of nicotine-induced behaviors in C57BL/6 mice.
PMCID: PMC3689186  PMID: 23611296
12.  Recombinant AAV9-TLK1B Administration Ameliorates Fractionated Radiation-Induced Xerostomia 
Human Gene Therapy  2013;24(6):604-612.
Salivary glands are highly susceptible to radiation, and patients with head and neck cancer treated with radiotherapy invariably suffer from its distressing side effect, salivary hypofunction. The reduction in saliva disrupts oral functions, and significantly impairs oral health. Previously, we demonstrated that adenoviral-mediated expression of Tousled-like kinase 1B (TLK1B) in rat submandibular glands preserves salivary function after single-dose ionizing radiation. To achieve long-term transgene expression for protection of salivary gland function against fractionated radiation, this study examines the usefulness of recombinant adeno-associated viral vector for TLK1B delivery. Lactated Ringers or AAV2/9 with either TLK1B or GFP expression cassette were retroductally delivered to rat submandibular salivary glands (1011 vg/gland), and animals were exposed, or not, to 20 Gy in eight fractions of 2.5 Gy/day. AAV2/9 transduced predominantly the ductal cells, including the convoluted granular tubules of the submandibular glands. Transgene expression after virus delivery could be detected within 5 weeks, and stable gene expression was observed till the end of study. Pilocarpine-stimulated saliva output measured at 8 weeks after completion of radiation demonstrated >10-fold reduction in salivary flow in saline- and AAV2/9-GFP-treated animals compared with the respective nonirradiated groups (90.8% and 92.5% reduction in salivary flow, respectively). Importantly, there was no decrease in stimulated salivary output after irradiation in animals that were pretreated with AAV2/9-TLK1B (121.5% increase in salivary flow; p<0.01). Salivary gland histology was better preserved after irradiation in TLK1B-treated group, though not significantly, compared with control groups. Single preemptive delivery of AAV2/9-TLK1B averts salivary dysfunction resulting from fractionated radiation. Although AAV2/9 transduces mostly the ductal cells of the gland, their protection against radiation assists in preserving submandibular gland function. AAV2/9-TLK1B treatment could prove beneficial in attenuating xerostomia in patients with head and neck cancer undergoing radiotherapy.
Shanmugam and colleagues demonstrate that a single instillation of recombinant AAV9 encoding Tousled-like kinase 1B (TLK1B) in rat submandibular glands leads to a complete amelioration of salivary dysfunction caused by fractionated radiation. They suggest that this treatment modality may be beneficial in attenuating xerostomia in headand-neck cancer patients undergoing radiotherapy.
PMCID: PMC3689188  PMID: 23614651
13.  Kinetics of Adeno-Associated Virus Serotype 2 (AAV2) and AAV8 Capsid Antigen Presentation In Vivo Are Identical 
Human Gene Therapy  2013;24(5):545-553.
Adeno-associated viral (AAV) vectors 2 and 8 have been used in clinical trials for patients with hemophilia, and data suggest that the capsid-specific CD8+ T cell response has had a negative impact on therapeutic success. To date the pattern of capsid cross-presentation from AAV2 and AAV8 transduction in vivo has not been elucidated. Previously, we have demonstrated that an engineered AAV2 virus carrying the immune-dominant SIINFEKL peptide in the capsid backbone was indistinguishable from wild type with respect to titer, tropism, and the ability to induce capsid-specific CD8+ T cell responses in vivo. In this study, we used the same strategy to engineer an AAV8 vector and demonstrated that antigen from SIINFEKL peptide-integrated AAV8 capsid was effectively presented via either plasmid transfection or AAV8 transduction in vitro. The tissue tropism and transgene expression kinetics of the engineered AAV8 vector in vivo were identical to that of wild-type AAV8. Animal studies show that capsid antigen presentation from AAV transduction was dose dependent, and more importantly, the proliferation of capsid-specific CD8+ T cells had similar kinetics (detectable before 30 days and undetectable after 40 days) for both AAV2 and AAV8 vectors. Elucidation of the kinetics of capsid antigen presentation from AAV transduction by various serotypes provides new insight into the potential impact CD8+ T cells can have during clinical trials and may help with rational design of effective strategies to prevent capsid-specific CD8+ T cell-mediated elimination of AAV-transduced target cells.
He and colleagues investigate differences between the in vivo kinetics of capsid-specific cytotoxic responses to adeno-associated virus (AAV) serotypes 2 and 8. Tissue tropism and transgene expression kinetics of an AAV8 vector engineered to carry the immune dominant peptide SIINFEKL (AAV8OVA) were identical to that of wild-type AAV8. Proliferation of capsid-specific CD8+ T cells exhibited similar kinetics for both AAV8OVA and AAV2OVA vectors.
PMCID: PMC3655625  PMID: 23534873
14.  Strong Cortical and Spinal Cord Transduction After AAV7 and AAV9 Delivery into the Cerebrospinal Fluid of Nonhuman Primates 
Human Gene Therapy  2013;24(5):526-532.
The present study builds on previous work showing that infusion of adeno-associated virus type 9 (AAV9) into the cisterna magna (CM) of nonhuman primates resulted in widespread transduction throughout cortex and spinal cord. Transduction efficiency was severely limited, however, by the presence of circulating anti-AAV antibodies. Accordingly, we compared AAV9 to a related serotype, AAV7, which has a high capsid homology. CM infusion of either AAV7 or AAV9 directed high level of cell transduction with similar patterns of distribution throughout brain cortex and along the spinal cord. Dorsal root ganglia and corticospinal tracts were also transduced. Both astrocytes and neurons were transduced. Interestingly, little transduction was observed in peripheral organs. Our results indicate that intrathecal delivery of either AAV7 or AAV9 directs a robust and widespread cellular transduction in the central nervous system and other peripheral neural structures.
Samaranch and colleagues compare the transduction profiles of AAV9-GFP and AAV7-GFP in nonhuman primates. They show that intrathecal delivery of either vector leads to equally high levels of cell transduction with similar patterns of distribution throughout the brain cortex and spinal cord, including the dorsal root ganglia and corticospinal tracts. Importantly, using this approach, they observe virtually no transduction of peripheral organs.
PMCID: PMC3655626  PMID: 23517473
15.  Recombinant Adeno-Associated Virus Integration Sites in Murine Liver After Ornithine Transcarbamylase Gene Correction 
Human Gene Therapy  2013;24(5):520-525.
Recombinant adeno-associated viruses (rAAVs) have been tested in humans and other large mammals without adverse events. However, one study of mucopolysaccharidosis VII correction in mice showed repeated integration of rAAV in cells from hepatocellular carcinoma (HCC) in the Dlk1–Dio3 locus, suggesting possible insertional mutagenesis. In contrast, another study found no association of rAAV integration with HCC, raising questions about the generality of associations between liver transformation and integration at Dlk1–Dio3. Here we report that in rAAV-treated ornithine transcarbamylase (Otc)–deficient mice, four examples of integration sites in Dlk1–Dio3 could be detected in specimens from liver nodule/tumors, confirming previous studies of rAAV integration in the Dlk1–Dio3 locus in the setting of another murine model of metabolic disease. In one case, the integrated vector was verified to be present at about one copy per cell, consistent with clonal expansion. Another verified integration site in liver nodule/tumor tissue near the Tax1bp1 gene was also detected at about one copy per cell. The Dlk1–Dio3 region has also been implicated in human HCC and so warrants careful monitoring in ongoing human clinical trials with rAAV vectors.
Zhong and colleagues use deep sequencing to examine the distribution of integrated AAV genomes in nodules/tumors from the livers of ornithine transcarbamylace (Otc) deficient mice. Using this approach, they report four examples of integration sites in the Dlk1-Dio3 locus; this site has previously been implicated in human hepatocellular carcinoma and may warrant careful monitoring in human clinical trials using AAV vectors.
PMCID: PMC3655627  PMID: 23621841
16.  Antisense Oligonucleotides for the Treatment of Spinal Muscular Atrophy 
Human Gene Therapy  2013;24(5):489-498.
Spinal muscular atrophy (SMA) is an autosomal recessive disease affecting ∼1 in 10,000 live births. The most striking component is the loss of α-motor neurons in the ventral horn of the spinal cord, resulting in progressive paralysis and eventually premature death. There is no current treatment paradigm other than supportive care, though the past 15 years has seen a striking advancement in understanding of both SMA genetics and molecular mechanisms. A variety of disease-modifying interventions are rapidly bridging the translational gap from the laboratory to clinical trials, including the application of antisense oligonucleotide (ASO) therapy for the correction of aberrant RNA splicing characteristic of SMA. Survival motor neuron (SMN) is a ubiquitously expressed 38-kD protein. Humans have two genes that produce SMN, SMN1 and SMN2, the former of which is deleted or nonfunctional in the majority of patients with SMA. These two genes are nearly identical with one exception, a C to T transition (C6T) within exon 7 of SMN2. C6T disrupts a modulator of splicing, leading to the exclusion of exon 7 from ∼90% of the mRNA transcript. The resultant truncated Δ7SMN protein does not oligomerize efficiently and is rapidly degraded. SMA can therefore be considered a disease of too little SMN protein. A number of cis-acting splice modifiers have been identified in the region of exon 7, the steric block of which enhances the retention of the exon and a resultant full-length mRNA sequence. ASOs targeted to these splice motifs have shown impressive phenotype rescue in multiple SMA mouse models.
PMCID: PMC3655628  PMID: 23544870
17.  Antisense Oligonucleotides: Rising Stars in Eliminating RNA Toxicity in Myotonic Dystrophy 
Human Gene Therapy  2012;24(5):499-507.
Myotonic dystrophy (DM) is a dominantly inherited, multisystemic disease caused by expanded CTG (type 1, DM1) or CCTG (type 2, DM2) repeats in untranslated regions of the mutated genes. Pathogenesis results from expression of RNAs from the mutated alleles that are toxic because of the expanded CUG or CCUG repeats. Increased understanding of the repeat-containing RNA (C/CUGexp RNA)-induced toxicity has led to the development of multiple strategies targeting the toxic RNA. Among these approaches, antisense oligonucleotides (ASOs) have demonstrated high potency in reversing the RNA toxicity in both cultured DM1 cells and DM1 animal models, thus offering great promise for the potential treatment of DM1. ASO targeting approaches will also provide avenues for the treatment of other repeat RNA-mediated diseases.
PMCID: PMC3655630  PMID: 23252746
18.  Hepatic Stellate Cell–Targeted Delivery of Hepatocyte Growth Factor Transgene via Bile Duct Infusion Enhances Its Expression at Fibrotic Foci to Regress Dimethylnitrosamine-Induced Liver Fibrosis 
Human Gene Therapy  2013;24(5):508-519.
Liver fibrosis generates fibrotic foci with abundant activated hepatic stellate cells and excessive collagen deposition juxtaposed with healthy regions. Targeted delivery of antifibrotic therapeutics to hepatic stellate cells (HSCs) might improve treatment outcomes and reduce adverse effects on healthy tissue. We delivered the hepatocyte growth factor (HGF) gene specifically to activated hepatic stellate cells in fibrotic liver using vitamin A–coupled liposomes by retrograde intrabiliary infusion to bypass capillarized hepatic sinusoids. The antifibrotic effects of DsRed2-HGF vector encapsulated within vitamin A–coupled liposomes were validated by decreases in fibrotic markers in vitro. Fibrotic cultures transfected with the targeted transgene showed a significant decrease in fibrotic markers such as transforming growth factor-β1. In rats, dimethylnitrosamine-induced liver fibrosis is manifested by an increase in collagen deposition and severe defenestration of sinusoidal endothelial cells. The HSC-targeted transgene, administered via retrograde intrabiliary infusion in fibrotic rats, successfully reduced liver fibrosis markers alpha-smooth muscle actin and collagen, accompanied by an increase in the expression of DsRed2-HGF near the fibrotic foci. Thus, targeted delivery of HGF gene to hepatic stellate cells increased the transgene expression at the fibrotic foci and strongly enhanced its antifibrotic effects.
Narmada and colleagues demonstrate that vitamin A–coupled liposomes can be used to deliver hepatocyte growth factor (HGF) specifically to activated human hepatic stellate cells (HSCs) in vitro. In vivo, they show that this approach leads to regression of liver fibrosis in a rat model.
PMCID: PMC3655631  PMID: 23527815
19.  A Novel Armed Oncolytic Measles Vaccine Virus for the Treatment of Cholangiocarcinoma 
Human Gene Therapy  2013;24(5):554-564.
Cholangiocarcinoma (CC) is curable only in early stages by complete surgical resection. Thus, in advanced disease stages in which a complete removal of the tumor mass is no longer possible and palliative chemotherapy achieves only modest success, therapeutics employing new methods of action are desperately needed. Oncolytic viruses employed in clinical studies have been shown to spread preferentially in cancer cells. Beyond that, virotherapeutic cell killing can be enhanced by virus-based expression of suicide genes. We engineered a measles vaccine virus (MeV) vector expressing super cytosine deaminase (SCD), a fusion protein of yeast cytosine deaminase and uracil phosphoribosyltransferase, which converts the prodrug 5-fluorocytosine (5-FC) to 5-fluorouracil (5-FU) and subsequently to 5-fluorouridine-monophosphate. This novel vector was evaluated using three different human-derived CC cell lines. In vitro, all CC cell lines were found to be permissive to MeV infection. Partial blocking of MeV-mediated oncolysis could be overcome by employment of the SCD transgene together with administration of 5-FC. In vivo, intratumoral application of SCD-armed MeV together with a systemic 5-FC treatment showed a significant reduction in tumor size in a TFK-1 xenograft mouse model when compared with virus-only treatment. In a second animal experiment employing a HuCCT1 xenograft tumor model, an enhanced SCD-armed MeV vector, in which the SCD transgene was expressed from a different genomic position, led not only to reduced tumor volumes, but also to a significant survival benefit. On the basis of these encouraging preclinical data on employment of SCD-armed MeV for the virotherapeutic treatment of chemotherapy-resistant CC, a clinical virotherapy trial is set up currently.
Lange and colleagues engineer a measles vaccine virus (MeV) vector expressing an enzyme that converts 5-fluorocytosine (5-FC) prodrug into 5-fluorouracil-monophosphate. Partial blocking of MeV-mediated oncolysis could be overcome by vector and 5–FC co-administration in cell lines. In vivo, intratumoral vector injection along with systemic 5–FC treatment resulted in significant tumor reduction in a xenograft mouse model.
PMCID: PMC3655633  PMID: 23550539
20.  Gene Therapy for Rare Diseases: Summary of a National Institutes of Health Workshop, September 13, 2012 
Human Gene Therapy  2013;24(4):355-362.
Gene therapy has shown clinical efficacy for several rare diseases, using different approaches and vectors. The Gene Therapy for Rare Diseases workshop, sponsored by the National Institutes of Health (NIH) Office of Biotechnology Activities and Office of Rare Diseases Research, brought together investigators from different disciplines to discuss the challenges and opportunities for advancing the field including means for enhancing data sharing for preclinical and clinical studies, development and utilization of available NIH resources, and interactions with the U.S. Food and Drug Administration.
PMCID: PMC3631014  PMID: 23517518
21.  Recovery of Radiation-Induced Dry Eye and Corneal Damage by Pretreatment with Adenoviral Vector-Mediated Transfer of Erythropoietin to the Salivary Glands in Mice 
Human Gene Therapy  2013;24(4):417-423.
Therapeutic doses of radiation (RTx) causes dry eye syndrome (DES), dry mouth, and as in other sicca syndromes, they are incurable. The aims of this work are as follows: (a) to evaluate a mouse model of DES induced by clinically relevant doses of radiation, and (b) to evaluate the protective effect of erythropoietin (Epo) in preventing DES. C3H female mice were subjected to five sessions of RTx, with or without pre-RTx retroductal administration of the AdLTR2EF1a-hEPO (AdEpo) vector in the salivary glands (SG), and compared with naïve controls at Day 10 (10d) (8 Gy fractions) and 56 days (56d) (6 Gy fractions) after RTx treatment. Mice were tested for changes in lacrimal glands (LG), tear secretion (phenol red thread), weight, hematocrit (Hct), and markers of inflammation, as well as microvessels and oxidative damage. Tear secretion was reduced in both RTx groups, compared to controls, by 10d. This was also seen at 56d in RTx but not AdEpo+RTx group. Hct was significantly higher in all AdEpo+RTx mice at 10d and 56d. Corneal epithelium was significantly thinner at 10d in the RTx group compared with AdEpo+RTx or the control mice. There was a significant reduction at 10d in vascular endothelial growth factor (VEGF)-R2 in LG in the RTx group that was prevented in the AdEpo+RTx group. In conclusion, RTx is able to induce DES in mice. AdEpo administration protected corneal epithelia and resulted in some recovery of LG function, supporting the value of further studies using gene therapy for extraglandular diseases.
Rocha and colleagues describe a mouse model of radiation-induced dry eye syndrome (DES). They show that adenoviral vector–mediated overexpression of erythropoietin in the salivary glands of mice protects the corneal epithelia and leads to recovery of lacrimal gland function.
PMCID: PMC3631015  PMID: 23402345
22.  Effects of Immunosuppression on Circulating Adeno-Associated Virus Capsid-Specific T cells in Humans 
Human Gene Therapy  2013;24(4):431-442.
In humans adeno-associated virus (AAV)-mediated gene transfer is followed by expansion of AAV capsid-specific T cells, evidence of cell damage, and loss of transgene product expression, implicating immunological rejection of vector-transduced cells, which may be prevented by immunosuppressive drugs. We undertook this study to assess the effect of immunosuppression (IS) used for organ transplantation on immune responses to AAV capsid antigens. Recipients of liver or kidney transplants were tested before and 4 weeks after induction of IS in comparison with matched samples from healthy human adults and an additional cohort with comorbid conditions similar to those of the transplant patients. Our data show that transplant patients and comorbid control subjects have markedly higher frequencies of circulating AAV capsid-specific T cells compared with healthy adults. On average, IS resulted in a reduction of AAV-specific CD4+ T cells, whereas numbers of circulating CD8+ effector and central memory T cells tended to increase. Independent of the type of transplant or the IS regimens, the trend of AAV capsid-specific T cell responses after drug treatment varied; in some patients responses were unaffected whereas others showed decreases or even pronounced increases, casting doubt on the usefulness of prophylactic IS for AAV vector recipients.
Parzych and colleagues assess the effect of immunosuppression (IS) when used for organ transplantation on immune responses to adeno-associated virus (AAV) capsid antigens. Transplant patients and comorbid control subjects had markedly higher frequencies of circulating AAV capsid–specific T cells compared with healthy adults. IS treatment resulted in a reduction of AAV-specific CD4+ T cells, whereas numbers of circulating CD8+ effector and central memory T cells tended to increase.
PMCID: PMC3631016  PMID: 23461589
23.  Persistence, Localization, and External Control of Transgene Expression After Single Injection of Adeno-Associated Virus into Injured Joints 
Human Gene Therapy  2013;24(4):457-466.
A single intra-articular injection of adeno-associated virus (AAV) results in stable and controllable transgene expression in normal rat knees. Because undamaged joints are unlikely to require treatment, the study of AAV delivery in joint injury models is crucial to potential therapeutic applications. This study tests the hypotheses that persistent and controllable AAV-transgene expression are (1) highly localized to the cartilage when AAV is injected postinjury and (2) localized to the intra-articular soft tissues when AAV is injected preinjury. Two AAV injection time points, postinjury and preinjury, were investigated in osteochondral defect and anterior cruciate ligament transection models of joint injury. Rats injected with AAV tetracycline response element (TRE)–luciferase received oral doxycycline for 7 days. Luciferase expression was evaluated longitudinally for 6 months. Transgene expression was persistent and controllable with oral doxycycline for 6 months in all groups. However, the location of transgene expression was different: postinjury AAV-injected knees had luciferase expression highly localized to the cartilage, while preinjury AAV-injected knees had more widespread signal from intra-articular soft tissues. The differential transgene localization between preinjury and postinjury injection can be used to optimize treatment strategies. Highly localized postinjury injection appears advantageous for treatments targeting repair cells. The more generalized and controllable reservoir of transgene expression following AAV injection before anterior cruciate ligament transection (ACLT) suggests an intriguing concept for prophylactic delivery of joint protective factors to individuals at high risk for early osteoarthritis (OA). Successful external control of intra-articular transgene expression provides an added margin of safety for these potential clinical applications.
Lee and colleagues investigate preinjury and postinjury intra-articular injection of inducible adeno-associated viral vectors (AAVs) in osteochondral defect and anterior cruciate ligament transection rat models of joint injury. Postinjury AAV-injected knees displayed highly localized transgene expression to the cartilage while preinjury AAV-injected knees had more widespread expression from intra-articular soft tissues.
PMCID: PMC3631018  PMID: 23496155
24.  Adenoviral Gene Transfer of Hepatic Stimulator Substance Confers Resistance Against Hepatic Ischemia–Reperfusion Injury by Improving Mitochondrial Function 
Human Gene Therapy  2013;24(4):443-456.
Hepatic stimulator substance (HSS) has been suggested to protect liver cells from various toxins. However, the precise role of HSS in hepatic ischemia–reperfusion (I/R) injury remains unknown. This study aims to elucidate whether overexpression of HSS could attenuate hepatic ischemia–reperfusion injury and its possible mechanisms. Both in vivo hepatic I/R injury in mice and in vitro hypoxia–reoxygenation (H/R) in a cell model were used to evaluate the effect of HSS protection after adenoviral gene transfer. Moreover, a possible mitochondrial mechanism of HSS protection was investigated. Efficient transfer of the HSS gene into liver inhibited hepatic I/R injury in mice, as evidenced by improvement in liver function tests, the preservation of hepatic morphology, and a reduction in hepatocyte apoptosis. HSS overexpression also inhibited H/R-induced cell death, as detected by cell viability and cell apoptosis assays. The underlying mechanism of this hepatic protection might involve the attenuation of mitochondrial dysfunction and mitochondrial-dependent cell apoptosis, as shown by the good preservation of mitochondrial ultrastructure, mitochondrial membrane potential, and the inhibition of cytochrome c leakage and caspase activity. Moreover, the suppression of H/R-induced mitochondrial ROS production and the maintenance of mitochondrial respiratory chain complex activities may participate in this mechanism. This new function of HSS expands the possibility of its application for the prevention of I/R injury, such as hepatic resection and liver transplantation in clinical practice.
Jiang and colleagues evaluate whether adenoviral-mediated overexpression of hepatic stimulator substance (HSS) could attenuate hepatic ischemia–reperfusion (I/R) injury. Efficient transfer of the HSS gene into liver-inhibited hepatic I/R injury in mice and hypoxia/reoxygenation–induced cell death in vitro. This hepatic protection appeared to involve the attenuation of mitochondrial dysfunction and mitochondrial-dependent cell apoptosis.
PMCID: PMC3631019  PMID: 23461564
25.  Myocardial Gene Transfer: Routes and Devices for Regulation of Transgene Expression by Modulation of Cellular Permeability 
Human Gene Therapy  2013;24(4):375-392.
Heart diseases are major causes of morbidity and mortality in Western society. Gene therapy approaches are becoming promising therapeutic modalities to improve underlying molecular processes affecting failing cardiomyocytes. Numerous cardiac clinical gene therapy trials have yet to demonstrate strong positive results and advantages over current pharmacotherapy. The success of gene therapy depends largely on the creation of a reliable and efficient delivery method. The establishment of such a system is determined by its ability to overcome the existing biological barriers, including cellular uptake and intracellular trafficking as well as modulation of cellular permeability. In this article, we describe a variety of physical and mechanical methods, based on the transient disruption of the cell membrane, which are applied in nonviral gene transfer. In addition, we focus on the use of different physiological techniques and devices and pharmacological agents to enhance endothelial permeability. Development of these methods will undoubtedly help solve major problems facing gene therapy.
PMCID: PMC3631020  PMID: 23427834

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