Immunity to adeno-associated virus-mediated gene transfer in a random-bred canine model of Duchenne muscular dystrophy

Recombinant adeno-associated virus (rAAV)-mediated gene transfer has shown promise for treating diseases in various animal models including the mdx mouse model of Duchenne muscular dystrophy (DMD). In many cases, however, preclinical studies in inbred mice have not successfully predicted human clinical responses. To assess the potential clinical utility of treating human DMD patients by AAV-mediated gene delivery, we performed a series of direct intramuscular injections in random-bred wild-type dogs. AAV serotypes 2 and 6 carrying different promoter-transgene cassettes were produced as previously described for murine studies and administered intramuscularly. The injection sites were biopsied at various time points and analyzed for transgene expression and immunohistochemical analysis. In contrast to the generally nonimmunogenic nature of these vectors in murine studies, both AAV2 and AAV6 vectors elicited robust cellular immune responses regardless of the transgene expressed, the cellular specificity of the promoter, and the muscle type injected. Viral purification by various methods did not diminish T cell-mediated infiltration. Our data indicate that AAV2 and AAV6 capsid proteins can elicit primary cellular immune responses when injected into the skeletal muscle of random-bred dogs, and suggest the possibility of cellular immunity to AAV vectors in humans.     

Recombinant adeno-associated virus-mediated in utero gene transfer gives therapeutic transgene expression in the sheep

Somatic in utero gene therapy aims to treat congenital diseases where pathology develops in perinatal life, thereby preventing permanent damage. The aim of this study was to determine whether delivery of self-complementary (sc) adeno-associated virus (AAV) vector in utero would provide therapeutic long-term transgene expression in a large animal model. We performed ultrasound-guided intraperitoneal injection of scAAV2/8-LP1-human Factor IX (hFIX)co (1 × 10(12) vector genomes/kg) in early (n = 4) or late (n = 2) gestation fetal sheep. The highest mean hFIX levels were detected 3 weeks after injection in late gestation (2,055 and 1,687.5 ng/ml, n = 2) and 3 days after injection in early gestation (435 ng/ml, n = 1). Plasma hFIX levels then dropped as fetal liver and lamb weights increased, although low levels were detected 6 months after late gestation injection (75 and 52.5 ng/ml, n = 2). The highest vector levels were detected in the fetal liver and other peritoneal organs; no vector was present in fetal gonads. hFIX mRNA was detectable only in hepatic tissues after early and late gestation injection. Liver function tests and bile acid levels were normal up to a year postnatal; there was no evidence of liver pathology. No functional antibodies to hFIX protein or AAV vector were detectable, although lambs mounted an antibody response after injection of hFIX protein and Freund's adjuvant. In conclusion, hFIX expression is detectable up to 6 months after delivery of scAAV vector to the fetal sheep using a clinically applicable method. This is the first study to show therapeutic long-term hFIX transgene expression after in utero gene transfer in a large animal model.     

Topoisomerase inhibition accelerates gene expression after adeno-associated virus-mediated gene transfer to the mammalian heart.

Utility of adeno-associated virus 2 (AAV2) vectors for cardiac gene therapy is limited by the prolonged lag phase before maximal gene expression. Topoisomerase inhibition can induce AAV2-mediated gene expression in vivo, but with variable success in different tissues. In this study, we demonstrate that topoisomerase inhibition can accelerate AAV2-mediated gene expression in the mouse heart. We used an AAV2 vector expressing firefly luciferase and monitored expression kinetics using non-invasive bioluminescence imaging. In the group receiving vector alone, cardiac luciferase activity was evident from week 2 onward and increased progressively to reach a steady plateau by 9 weeks postinjection. In the group receiving vector and camptothecine (CPT), luciferase expression was evident from days 2 to 4 onward and increased rapidly to reach a steady plateau by 3-4 weeks postinjection, nearly three times faster than in the absence of CPT (P<0.05). Southern blot analysis of AAV2 genomes in cardiac tissue showed rapid conversion of the AAV2 genome from its single-stranded to double-stranded form in CPT-treated mice. Non-invasive determinations of luciferase expression correlated well with in vitro luciferase assays. Direct injection of the AAV2 vector and long-term luciferase gene expression had no detectable effects on normal cardiac function as assessed by magnetic resonance imaging.     

Recombinant adeno-associated virus-mediated gene transfer for the potential therapy of adenosine deaminase-deficient severe combined immune deficiency

Severe combined immune deficiency due to adenosine deaminase (ADA) deficiency is a rare, potentially fatal pediatric disease, which results from mutations within the ADA gene, leading to metabolic abnormalities and ultimately profound immunologic and nonimmunologic defects. In this study, recombinant adeno-associated virus (rAAV) vectors based on serotypes 1 and 9 were used to deliver a secretory version of the human ADA (hADA) gene to various tissues to promote immune reconstitution following enzyme expression in a mouse model of ADA deficiency. Here, we report that a single-stranded rAAV vector, pTR2-CB-Igκ-hADA, (1) facilitated successful gene delivery to multiple tissues, including heart, skeletal muscle, and kidney, (2) promoted ectopic expression of hADA, and (3) allowed enhanced serum-based enzyme activity over time. Moreover, the rAAV-hADA vector packaged in serotype 9 capsid drove partial, prolonged, and progressive immune reconstitution in ADA-deficient mice. Overview Summary Gene therapies for severe combined immune deficiency due to adenosine deaminase (ADA) deficiency (ADA-SCID) over two decades have exclusively involved retroviral vectors targeted to lymphocytes and hematopoietic progenitor cells. These groundbreaking gene therapies represented an unprecedented revolution in clinical medicine but in most cases did not fully correct the immune deficiency and came with the potential risk of insertional mutagenesis. Alternatively, recombinant adeno-associated virus (rAAV) vectors have gained attention as valuable tools for gene transfer, having demonstrated no pathogenicity in humans, minimal immunogenicity, long-term efficacy, ease of administration, and broad tissue tropism (Muzyczka, 1992 ; Flotte et al., 1993 ; Kessler et al., 1996 ; McCown et al., 1996 ; Lipkowitz et al., 1999 ; Marshall, 2001 ; Chen et al., 2003 ; Conlon and Flotte, 2004 ; Griffey et al., 2005 ; Pacak et al., 2006 ; Stone et al., 2008 ; Liu et al., 2009 ; Choi et al., 2010 ). Currently, rAAV vectors are being utilized in phase I/II clinical trials for cystic fibrosis, α-1 antitrypsin deficiency, Canavan's disease, Parkinson's disease, hemophilia, limb-girdle muscular dystrophy, arthritis, Batten's disease, and Leber's congenital amaurosis (Flotte et al., 1996 , 2004 ; Kay et al., 2000 ; Aitken et al., 2001 ; Wagner et al., 2002 ; Manno et al., 2003 ; Snyder and Francis, 2005 ; Maguire et al., 2008 ; Cideciyan et al., 2009 ). In this study, we present preclinical data to support the viability of an rAAV-based gene transfer strategy for cure of ADA-SCID. We report efficient transduction of a variety of postmitotic target tissues in vivo, subsequent human ADA (hADA) expression, and enhanced hADA secretion in tissues and blood, with increasing peripheral lymphocyte populations over time.     

Evaluation of adeno-associated virus-mediated gene transfer into the rat retina by clinical fluorescence photography

The purpose of this study was to evaluate recombinant adeno-associated virus (AAV) as an in vivo gene transfer vector for the retina and to explore the possibility of monitoring the expression of green fluorescent protein (GFP) using a noninvasive method. Rats were injected subretinally with rAAV-gfp or rAAV-lacZ. Strong expression of the reporter gene in a circular area surrounding the injection site was observed in retinal whole mounts and tissue sections. Higher magnification revealed that cells demonstrating high levels of green fluorescence were hexagonal in shape, indicating they were retinal pigment epithelium (RPE) cells. Histological observation of retinal sections demonstrated that recombinant AAV specifically transduced RPE cells. Ten animals were injected with rAAV-gfp for longitudinal studies and the fluorescence was monitored by retinal fluorescence photography. The GFP signal was detected in 100% of the animals as early as 2 weeks postinjection and remained present throughout the experimental period of 4 months. After 2 weeks, a gradual increase in the number of transduced cells occurred before reaching maximal levels of GFP expression at 8 weeks. This was followed by a small decrease over 4 weeks before reaching stable expression at 16 weeks. Our results demonstrated that rAAV efficiently transduces rat RPE cells and that retinal fluorescence photography is suitable for monitoring GFP expression. By using this noninvasive technique, we demonstrated that repetitive measurements of GFP expression in vivo in the rAAV-gfp-transduced retina are possible. This study demonstrated that retinal fluorescence photography is a potent tool for studying AAV-mediated gene delivery in the retina.     

Noninvasive monitoring of therapeutic gene transfer in animal models of muscular dystrophies

Muscular dystrophies are a genetically and phenotypically heterogeneous group of degenerative muscle diseases. A subset of them are due to genetic deficiencies in proteins which form the dystrophin-associated complex at the membrane of the myofibers. In this report, we utilized recombinant adeno-associated virus containing a U7 cassette carrying an antisense sequence aimed at inducing exon skipping of the dystrophin gene or containing the alpha-sarcoglycan gene to alleviate the dystrophic phenotype of the mdx and Sgca-null mice, respectively. As these diseases are characterized by cycle of degeneration/regeneration, we postulated that a reporter gene coadministered at the time of the treatment would make it possible to follow the extent of muscle repair. We observed that the murine secreted alkaline phosphatase (muSeAP) level was very much lower in these animal models than in normal mice. Upon treatment of the dystrophic muscle by gene transfer, the level of muSeAP was restored and correlated with the expression of the therapeutic transgene and with the level of muscle improvement. The system described here provides a simple and noninvasive procedure for monitoring the outcome of a therapeutic strategy involving cell survival.     

Partial cure of established disease in an animal model of metachromatic leukodystrophy after intracerebral adeno-associated virus-mediated gene transfer

Metachromatic leukodystrophy (MLD) is a lysosomal storage disease caused by genetic deficiency of arylsulfatase A (ARSA) enzyme. Failure in catalyzing the degradation of its major substrate, sulfatide (Sulf), in oligodendrocytes and Schwann cells leads to severe demyelination in the peripheral (PNS) and central nervous system (CNS), and early death of MLD patients. The ARSA knockout mice develop a disease that resembles MLD but is milder, without significant demyelination in the PNS and CNS. We showed that adeno-associated virus serotype 5-mediated gene transfer in the brain of ARSA knockout mice reverses Sulf storage and prevents neuropathological abnormalities and neuromotor disabilities when vector injections are performed at a pre-symptomatic stage of disease. Direct injection of viral particles into the brain of ARSA knockout mice at a symptomatic stage results in sustained expression of ARSA, prevention of Sulf storage and neuropathological abnormalities. Despite these significant corrections, the treated mice continue to develop neuromotor disability. We show that more subtle biochemical abnormalities involving gangliosides and galactocerebroside are in fact not corrected.     

Production of CFTR-null and CFTR-DeltaF508 heterozygous pigs by adeno-associated virus-mediated gene targeting and somatic cell nuclear transfer

Progress toward understanding the pathogenesis of cystic fibrosis (CF) and developing effective therapies has been hampered by lack of a relevant animal model. CF mice fail to develop the lung and pancreatic disease that cause most of the morbidity and mortality in patients with CF. Pigs may be better animals than mice in which to model human genetic diseases because their anatomy, biochemistry, physiology, size, and genetics are more similar to those of humans. However, to date, gene-targeted mammalian models of human genetic disease have not been reported for any species other than mice. Here we describe the first steps toward the generation of a pig model of CF. We used recombinant adeno-associated virus (rAAV) vectors to deliver genetic constructs targeting the CF transmembrane conductance receptor (CFTR) gene to pig fetal fibroblasts. We generated cells with the CFTR gene either disrupted or containing the most common CF-associated mutation (DeltaF508). These cells were used as nuclear donors for somatic cell nuclear transfer to porcine oocytes. We thereby generated heterozygote male piglets with each mutation. These pigs should be of value in producing new models of CF. In addition, because gene-modified mice often fail to replicate human diseases, this approach could be used to generate models of other human genetic diseases in species other than mice.     

Elastin-like polypeptide matrices for enhancing adeno-associated virus-mediated gene delivery to human neural stem cells

The successful development of efficient and safe gene delivery vectors continues to be a major obstacle to gene delivery in stem cells. In this study, we have developed an elastin-like polypeptide (ELP)-mediated adeno-associated virus (AAV) delivery system for transducing fibroblasts and human neural stem cells (hNSCs). AAVs have significant promise as therapeutic vectors because of their safety and potential for use in gene targeting in stem cell research. ELP has been recently employed as a biologically inspired 'smart' biomaterial that exhibits an inverse temperature phase transition, thereby demonstrating promise as a novel drug carrier. The ELP that was investigated in this study was composed of a repetitive penta-peptide with [Val-Pro-Gly-Val-Gly]. A novel AAV variant, AAV r3.45, which was previously engineered by directed evolution to enhance transduction in rat NSCs, was nonspecifically immobilized onto ELPs that were adsorbed beforehand on a tissue culture polystyrene surface (TCPS). The presence of different ELP quantities on the TCPS led to variations in surface morphology, roughness and wettability, which were ultimately key factors in the modulation of cellular transduction. Importantly, with substantially reduced viral quantities compared with bolus delivery, ELP-mediated AAV delivery significantly enhanced delivery efficiency in fibroblasts and hNSCs, which have great potential for use in tissue engineering applications and neurodegenerative disorder treatments, respectively. The enhancement of cellular transduction in stem cells, as well as the feasibility of ELPs for utilization in three-dimensional scaffolds, will contribute to the advancement of gene therapy for stem cell research and tissue regenerative medicine.     

腺相关病毒介导癌胚抗原转染树突状细胞对免疫功能的调节作用

目的:近年来,树突状细胞参与调节作用的研究较多。实验拟验证重组腺相关病毒(rAAV)介导癌胚抗原基因转染树突状细胞后其的免疫调节作用的变化。方法:实验于2006-06/2006-11在美国阿肯色大学医学院基因治疗中心完成。①实验方法:取健康人外周血(自愿捐献),采用改良Ficoll密度梯度离心的方法分离外周血单个核细胞,取贴壁细胞,分为rAAV/CEA转染组和空白对照组,均采用重组人粒细胞巨噬细胞集落刺激因子、白细胞介素4、肿瘤坏死因子-α诱导树突状细胞前体细胞成熟,将成熟树突状细胞与末梢血淋巴细胞按比例混合培养,可得到激活的细胞毒性T淋巴细胞。②实验评估:采用流式细胞仪检测树突状细胞表面标志表达,细胞毒性T淋巴细胞的免疫表型变化,细胞毒性T淋巴细胞γ-干扰素表达。采用酶联免疫吸附法(ELISA法)检测树突状细胞的白细胞介素12和白细胞介素10表达。结果:①rAAV/CEA转染树突状细胞的CD14较空白对照组降低,共刺激分子CD40、CD80、CD83、CD86表达均较空白对照组高。②成熟树突状细胞细胞因子表达中,rAAV/CEA转染组的白细胞介素12较空白对照组升高,白细胞介素10降低。③与空白对照组比较,rAAV/CEA转染组能高表达CD8 T细胞和其表型CD69,CD8/CD56的T细胞比例上调,CD25 CD4 的T细胞减少。④rAAV/CEA转染的细胞毒性T淋巴细胞表达相对较高水平的γ-干扰素,与杀伤实验结果相吻合。结论:rAAV/CEA转染树突状细胞能够激活细胞毒性T淋巴细胞的特异性杀伤作用,与树突状细胞和细胞毒性T淋巴细胞等免疫细胞表面标志变化和细胞内细胞因子水平变化相关。     

Intrathecal gene transfer by adeno-associated virus for pain

Chronic pain is among the most prevalent medical problems, affecting more than half of patients with advanced cancer and many with other common diseases. Current analgesics often fail to provide satisfactory symptom relief and frequently cause severe side effects. Intrathecal (IT) gene transfer is an attractive method for pain research in rodent models, because it allows targeting of a wide variety of secretable peptides and proteins to the spinal cord, an important neural center for the processing of nociceptive signals. The potential of IT gene transfer for improving opioid therapy and for validating new analgesic targets, such as cytokines involved in spinal glial activation, is discussed. The IT space has been notoriously resistant to efficient gene transfer, limiting therapeutic gene expression to less than 2 weeks with most vector systems. Recent progress with adeno-associated virus (AAV) technology allowed efficient long-term gene expression, facilitating studies reflective of the chronic nature of many pain states. AAV is one of the most advanced gene therapy vectors currently undergoing clinical trials for a variety of disorders. In patients, AAV vectors could be administered intrathecally by a lumbar puncture, a safe procedure routinely performed at the bedside. AAV vectors may therefore become an important tool for translational studies to validate newly identified therapeutic targets in clinical pain states.     

Sendai virus-mediated CFTR gene transfer to the airway epithelium

The potential for gene therapy to be an effective treatment for cystic fibrosis has been hampered by the limited gene transfer efficiency of current vectors. We have shown that recombinant Sendai virus (SeV) is highly efficient in mediating gene transfer to differentiated airway epithelial cells, because of its capacity to overcome the intra- and extracellular barriers known to limit gene delivery. Here, we have identified a novel method to allow the cystic fibrosis transmembrane conductance regulator (CFTR) cDNA sequence to be inserted within SeV (SeV-CFTR). Following in vitro transduction with SeV-CFTR, a chloride-selective current was observed using whole-cell and single-channel patch-clamp techniques. SeV-CFTR administration to the nasal epithelium of cystic fibrosis (CF) mice (Cftr(G551D) and Cftr(tm1Unc)TgN(FABPCFTR)#Jaw mice) led to partial correction of the CF chloride transport defect. In addition, when compared to a SeV control vector, a higher degree of inflammation and epithelial damage was found in the nasal epithelium of mice treated with SeV-CFTR. Second-generation transmission-incompetent F-deleted SeV-CFTR led to similar correction of the CF chloride transport defect in vivo as first-generation transmission-competent vectors. Further modifications to the vector or the host may make it easier to translate these studies into clinical trials of cystic fibrosis.     

A histone deacetylase inhibitor enhances recombinant adeno-associated virus-mediated gene expression in tumor cells.

The transduction of cancer cells using recombinant adeno-associated virus (rAAV) occurs with low efficiency, which limits its utility in cancer gene therapy. We have previously sought to enhance rAAV-mediated transduction of cancer cells by applying DNA-damaging stresses. In this study, we examined the effects of the histone deacetylase inhibitor FR901228 on tumor transduction mediated by rAAV types 2 and 5. FR901228 treatment significantly improved the expression of the transgene in four cancer cell lines. The cell surface levels of alpha v integrin, FGF-R1, and PDGF-R were modestly enhanced by the presence of FR901228. These results suggest that the superior transduction induced by the HDAC inhibitor was due to an enhancement of transgene expression rather than increased viral entry. Furthermore, we characterized the association of the acetylated histone H3 in the episomal AAV vector genome by using the chromatin immunoprecipitation assay. The results suggest that the superior transduction may be related to the proposed histone-associated chromatin form of the rAAV concatemer in transduced cells. In the analysis with subcutaneous tumor models, strong enhancement of the transgene expression as well as therapeutic effect was confirmed in vivo. The use of this HDAC inhibitor may enhance the utility of rAAV-mediated transduction strategies for cancer gene therapy.     

Potential long-term inhibition of ocular neovascularisation by recombinant adeno-associated virus-mediated secretion gene therapy

Neovascularisation (NV) within the eye often results in visual loss. Vascular endothelial growth factor (VEGF) has been implicated in the development of ocular NV. Previous studies have shown that VEGF antagonists successfully suppressed retinal and choroidal NV in animal models. However, the systemic approach and transient nature of the delivery systems used in these studies hinder therapeutic application. To achieve stable and localised ocular anti-angiogenic therapy, we explored the use of recombinant adeno-associated virus (rAAV)-mediated secretion gene therapy (SGT). In this study, we generated a rAAV vector encoding soluble VEGF receptor 1, sFlt-1 (AAV-CMV.sflt) and determined its ability to inhibit cautery-induced corneal NV and laser-induced choroidal NV. Delivery of AAV-CMV.sflt into the anterior chamber resulted in transgene expression in the iris pigment epithelium and corneal endothelium, which reduced the development of corneal NV in the stroma of cauterised rats by 36% compared with cauterised control groups (P = 0.009). Subretinal delivery of AAV-CMV.sflt near the equator of the eye also suppressed choroidal NV at the laser lesions around the optic nerve by 19% (P = 0.002), indicating that there was diffusion of the secreted anti-angiogenic protein across the retina. Both results suggest that the long-term suppression of ocular NV is possible through the use of stable rAAV-mediated SGT.     

Evaluation of adeno-associated viral vectors for liver-directed gene transfer in dogs

This study evaluated six adeno-associated viral (AAV) vectors expressing green fluorescent protein (GFP) from the liver-specific thyroid hormone-binding globulin (TBG) promoter made with novel capsids in canine liver-directed gene transfer. Studies in 1.5-month-old dogs, which were administered vector through a peripheral vein, showed that AAV8 capsid vectors had the most favorable performance profiles. Interestingly, the absolute levels of hepatocyte transduction achieved with AAV8 were lower in dogs compared with what had been achieved in mice and nonhuman primates. Additional studies were performed with AAV8 delivered into the hepatic artery in adult dogs, with higher doses of vector used to assess potential dose-limiting toxicities. These studies showed good transduction on day 7 in one dog that apparently was lost by day 28 in another dog through the generation of GFP-specific T cells. Each adult dog was carefully monitored for any hemodynamic changes associated with vector infusion. Both animals demonstrated mild to moderate hypotension and bradycardia, which appeared to be anesthesia-related, making it difficult to evaluate contributions of the vector.     

Utility of PEGylated recombinant adeno-associated viruses for gene transfer.

Adeno-associated virus (AAV), capable of producing significant, long-term transgene expression, is one of the least toxic vectors employed in pre-clinical and clinical studies of gene transfer. One limitation is generation of neutralizing antibodies against viral capsids, blocking gene expression after readministration. AAV2 capsids were modified with poly(ethylene) glycols (PEGs) activated by cyanuric chloride (CCPEG), succinimidyl succinate (SSPEG) and tresyl chloride (TMPEG). SSPEG and TMPEG conjugation did not compromise gene transfer to the liver and muscle and improved gene expression in the lung 5 fold. Transduction efficiency of CCPEG-AAV was impeded in all tissues by aggregation. TMPEG afforded the best protection from neutralization in vitro and in vivo. Gene expression in mice immunized against unmodified AAV was reduced by a factor of 10 from that of na?ve animals after intramuscular rechallenge with PEGylated AAV but was not significantly different from na?ve mice after intravenous readministration (p=0.08). Gene expression was markedly reduced in muscle after two doses of PEGylated AAV. In contrast, mice given two intravenous doses of TMPEG-AAV had significantly higher transgene levels than na?ve animals 14 days after rechallenge (p=0.001). This technology could promote successful readministration of vector in the clinic and marked expression in patients with anti-AAV antibodies.     

Recombinant adeno-associated virus-mediated alpha-1 antitrypsin gene therapy prevents type I diabetes in NOD mice

Type I diabetes results from an autoimmune destruction of the insulin-producing pancreatic beta cells. Although the exact immunologic processes underlying this disease are unclear, increasing evidence suggests that immunosuppressive, immunoregulatory and anti-inflammatory agents can interrupt the progression of the disease. Alpha 1 antitrypsin (AAT) is a multifunctional serine proteinase inhibitor (serpin) that also displays a wide range of anti-inflammatory properties. To test the ability of AAT to modulate the development of type I diabetes, we performed a series of investigations involving recombinant adeno-associated virus vector (rAAV)-mediated gene delivery of human alpha-1 antitrypsin (hAAT) to nonobese diabetic (NOD) mice. Recombinant AAV-expressing hAAT (rAAV2-CB-AT) was administered intramuscularly to 4-week-old female NOD mice (1 x 10(10) i.u./mouse). A single injection of this vector reduced the intensity of insulitis, the levels of insulin autoantibodies, and the frequency of overt type I diabetes (30% (3/10) at 32 weeks of age versus 70% (7/10) in controls). Transgene expression at the injection sites was confirmed by immunostaining. Interestingly, antibodies against hAAT were present in a majority of the vector-injected mice and circulating hAAT was undetectable when assessed 10 weeks postinjection. This study suggests a potential therapeutic role for AAT in preventing type I diabetes as well as the ability of AAV gene therapy-based approaches to ameliorate disease effectively.