Therapeutic Effects Of Gene Therapy Research Articles

Morc2a variants cause hydroxyl radical-mediated neuropathy and are rescued by restoring GHKL ATPase.

Mutations in the Microrchidia CW-type zinc finger 2 (MORC2) GHKL ATPase module cause a broad range of neuropathies, such as Charcot-Marie-Tooth disease type 2Z; however, the aetiology and therapeutic strategy are not fully understood. Previously, we reported that the Morc2a p.S87L mouse model exhibited neuropathy and muscular dysfunction through DNA damage accumulation. In the present study, we analysed the gene expression of Morc2a p.S87L mice and designated the primary causing factor. We investigated the pathological pathway using Morc2a p.S87L mouse embryonic fibroblasts and human fibroblasts harbouring MORC2 p.R252W. We subsequently assessed the therapeutic effect of gene therapy administered to Morc2a p.S87L mice. This study revealed that Morc2a p.S87L causes a protein synthesis defect, resulting in the loss of function of Morc2a and high cellular apoptosis induced by high hydroxyl radical levels. We considered the Morc2a GHKL ATPase domain as a therapeutic target because it simultaneously complements hydroxyl radical scavenging and ATPase activity. We used the adeno-associated virus (AAV)-PHP.eB serotype, which has a high CNS transduction efficiency, to express Morc2a or Morc2a GHKL ATPase domain protein in vivo. Notably, AAV gene therapy ameliorated neuropathy and muscular dysfunction with a single treatment. Loss-of-function characteristics due to protein synthesis defects in Morc2a p.S87L were also noted in human MORC2 p.S87L or p.R252W variants, indicating the correlation between mouse and human pathogenesis. In summary, CMT2Z is known as an incurable genetic disorder, but the present study demonstrated its mechanisms and treatments based on established animal models. This study demonstrates that the Morc2a p.S87L variant causes hydroxyl radical-mediated neuropathy, which can be rescued through AAV-based gene therapy.

Sustained Release of Gas6 via mPEG-PLGA Nanoparticles Enhances the Therapeutic Effects of MERTK Gene Therapy in RCS Rats.

Previous researches utilizing MER proto-oncogene tyrosine kinase (MERTK) gene therapy in Royal College of Surgeons (RCS) rats evidenced its effectiveness in treating MERTK-associated retinitis pigmentosa (RP). Specific ligands for receptor tyrosine kinases, such as growth arrest-specific 6 (Gas6), may enhance retinal phagocytosis via the MERTK receptor, and consequently, enhance the therapeutic effects of gene therapy. In order to overcome the short life effect of the injected Gas6 protein, we constructed a Gas6 loaded methoxy-poly (ethylene glyeol)-poly (lactic-co-glycolic acid) (mPEG-PLGA) nanoparticles (Gas6 NPs) system which allowed for localized and sustained Gas6 protein release, and therefore, a prolonged biological effect. Our data demonstrated that Gas6 protein release from Gas6 NPs preserved the bioactivity and promoted retinal pigment epithelium (RPE) phagocytosis in vitro. In vivo studies showed that RCS rats in the hMERTK/Gas6 NPs group exhibiting the highest electroretinogram responses and more complete retinal structure than that in other groups, further demonstrating that the co-administration of AAV2-BEST1-hMERTK and Gas6 NPs could protect photoreceptors from degeneration. These findings strongly suggest that Gas6 NPs are a promising method to enable the sustained release of Gas6 protein and could therefore enhance the therapeutic effects of gene therapy for MERTK-associated RP.

Oxygen nanocarrier broke the hypoxia trap of solid tumors and rescued transfection efficiency for gene therapy

BackgroundGene therapy shows great promise for a broad array of diseases. However, we found that hypoxic tumor microenvironment (TME) exerted significant inhibitory effects on transfection efficiency of a variety of gene vectors (such as Lipo 2000 and PEI) in an oxygen-dependent manner. Solid tumors inevitably resulted in acute hypoxic areas due to the rapid proliferation of tumor cells and the aberrant structure of blood vessels. Thus, the hypoxic TME severely limited the efficiency and application of gene therapy.MethodsIn our previous study, we constructed endoplasmic reticulum-targeted cationic liposomes, PAR-Lipo, which could effectively deliver genes and ensure high transfection efficiency under normoxia. Unsatisfactorily, the transfection efficiency of PAR-Lipo was rather poor under hypoxia. We believed that reoxygenation was the most direct and effective means to rescue the low transfection under hypoxia. Hence, we fabricated liposomes modified with perfluorooctyl bromide (PFOB@Lipo) to load oxygen and deliver it to tumor sites, which effectively alleviated the hypoxic nature of tumor. Then PAR-Lipo were applied to mediate high-efficiency delivery of tumor suppressor gene pTP53 to inhibit tumor progression.ResultsThe results showed that such staged strategy augmented the expression of P53 protein in tumors and extremely suppressed tumor growth.ConclusionThis work was the first attempt to utilize an oxygen nanocarrier to assist the therapeutic effect of gene therapy under hypoxia, providing a new reference for gene therapy in malignant tumors.Graphical Abstarct

Overexpression of PDX1 and NKX6.1 as a Treatment for Type 1 Diabetes: A Research Protocol

Introduction: Type 1 diabetes is an autoimmune disorder characterized by the destruction of pancreatic islet beta cells responsible for insulin production, leading to insulin deficiency. The PDX1 and NKX6-1 genes are essential to beta cell development and maturation in the pancreas. Based on previous studies, Pdx1 is downregulated in diabetics, and higher Nkx6.1 expression has been shown to induce high cell turnover. This proposal aims to investigate the potential therapeutic effects of gene therapy on streptozotocin-induced non-obese diabetic/severe-combined immunodeficient mice in treating Type 1 Diabetes. It is hypothesized that the use of gene therapy to overexpress PDX1 and NKX6-1 into the pancreas of experimental diabetic mice will result in increased beta cell production and improved glucose metabolism. Methods: Both male and female streptozotocin-induced non-obese diabetic/severe-combined immunodeficient experimental mice will receive human islets from individuals 32-55 years old. The PDX1 and NKX6-1 genes will be overexpressed in a shuttle vector and incorporated into the gutless adenovirus vector backbone through co-transfection using the Cre293/lox P cell line. Verification of successful vectors containing the gutless adenovirus coupled with a helper plasmid will be done using gel electrophoresis. Incubation with beta cells will stimulate the transduction process after which beta cells will be delivered into mice pancreas’ through endoscopic retrograde cholangiopancreatography. An intraperitoneal glucose tolerance test, pancreatic biopsy with immunohistochemical staining, and islet calculations will be done. Results: An intraperitoneal glucose tolerance test is expected to show improved blood glucose levels in experimental mice post-treatment, while a pancreatic biopsy with immunohistochemical staining and subsequent islet diameter and volume calculations are expected to depict an increase in the number of beta cells. Discussion: The experimental mice are anticipated to show an improvement in blood glucose levels and increased production of beta cells following treatment due to the overexpression of PDX1 and NKX6-1. The normal control mice and diabetic untreated mice are expected to show normal and high glucose levels, as well as normal and deficient beta cells respectively. Conclusion: This proposal may provide a better understanding of the pathophysiology in Type 1 Diabetes and pave a new path for its treatment.

Viral gene therapy for paediatric neurological diseases: progress to clinical reality.

In the era of genomic medicine, diagnoses of rare paediatric neurological diseases are increasing. Many are untreatable and life-limiting, leading to an exceptional increase in gene therapy development. It is estimated that 20 gene therapy products will have received approval from the US Food and Drug Administration by 2025. With viral gene therapy considered a potential single-dose cure for patients with spinal muscular atrophy type 1 as one example, and contemporaneously tragically resulting in the deaths of three male children with X-linked myotubular myopathy receiving high-dose gene therapy in 2020, what is the current state of gene therapy? What is behind the decades of hype around viral gene therapy and is it high impact, but high risk? In this review, we outline principles of viral gene therapy development and summarize the most recent clinical evidence for the therapeutic effect of gene therapy in paediatric neurological diseases. We discuss adeno-associated virus and lentiviral vectors, antisense oligonucleotides, emerging genetic editing approaches, and current limitations that the field still faces. What this paper adds Viral gene therapy development and clinically used transgenes, regulatory elements, capsids, dosage, and delivery routes are summarized. Viral gene therapy for 18 childhood neurological disorders involving over 600 children in 40 clinical trials are reviewed.

Sustained Release of Gas6 Through MPEG-PLGA Nanoparticles for Enhancing Therapeutic Effects of Gene Therapy for MERTK-Associated Retinitis Pigmentosa

Previous researches utilizing MER proto-oncogene tyrosine kinase (MERTK) gene therapy in Royal College of Surgeons (RCS) rats evidenced its effectiveness in treating MERTK-associated retinitis pigmentosa (RP). Specific ligands for receptor tyrosine kinases, such as growth arrest-specific 6 (Gas6), may enhance retinal phagocytosis via the MERTK receptor, and consequently, enhance the therapeutic effects of gene therapy. In order to overcome the short life effect of the injected Gas6 protein, we constructed a Gas6 loaded methoxy-poly(ethylene glyeol)-poly(lactic-co-glycolic acid) (mPEG-PLGA) nanoparticles (Gas6 NPs) system which allowed for localized and sustained Gas6 protein release, and therefore, a prolonged biological effect. Our data demonstrated that Gas6 protein release from Gas6 NPs preserved the bioactivity and promoted retinal pigment epithelium (RPE) phagocytosis in vitro. Furthermore, the co-transplantation of AAV2-BEST1-hMERTK and Gas6 NPs protected photoreceptors from degeneration in RCS rats. Electroretinogram responses in the hMERTK, hMERTK/Gas6, and hMERTK/Gas6 NPs groups were significantly higher than that of the control, with the hMERTK/Gas6 NPs group exhibiting the highest response. These findings strongly suggest that Gas6 NPs are a promising method to enable the sustained release of Gas6 protein within the therapeutic window and could therefore enhance the therapeutic effects of gene therapy for MERTK-associated RP.

Ex Vivo Gene Therapy Treats Bone Complications of Mucopolysaccharidosis Type II Mouse Models through Bone Remodeling Reactivation

Mucopolysaccharidosis type II is a disease caused by organ accumulation of glycosaminoglycans due to iduronate 2-sulfatase deficiency. This study investigated the pathophysiology of the bone complications associated with mucopolysaccharidosis II and the effect of lentivirus-mediated gene therapy of hematopoietic stem cells on bone lesions of mucopolysaccharidosis type II mouse models in comparison with enzyme replacement therapy. Bone volume, density, strength, and trabecular number were significantly higher in the untreated mucopolysaccharidosis type II mice than in wild-type mice. Accumulation of glycosaminoglycans caused reduced bone metabolism. Specifically, persistent high serum iduronate 2-sulfatase levels and release of glycosaminoglycans from osteoblasts and osteoclasts in mucopolysaccharidosis type II mice that had undergone gene therapy reactivated bone lineage remodeling, subsequently reducing bone mineral density, strength, and trabecular number to a similar degree as that observed in wild-type mice. Bone formation, resorption parameters, and mineral density in the diaphysis edge did not appear to have been affected by the irradiation administered as a pre-treatment for gene therapy. Hence, the therapeutic effect of gene therapy on the bone complications of mucopolysaccharidosis type II mice possibly outweighed that of enzyme replacement therapy in many aspects.

Enhancement of Adeno-Associated Virus-Mediated Gene Therapy Using Hydroxychloroquine in Murine and Human Tissues

The therapeutic effects of gene therapy using adeno-associated virus (AAV) vectors are dependent on the efficacy of viral transduction. Currently, we have reached the safe limits of AAV vector dose, beyond which damaging inflammatory responses are seen. To improve the efficacy of AAV transduction, we treated mouse embryonic fibroblasts, primate retinal pigment epithelial cells, and human retinal explants with hydroxychloroquine (HCQ) 1 h prior to transduction with an AAV2 vector encoding GFP driven by a ubiquitous CAG promoter. This led to a consistent increase in GFP expression, up to 3-fold, compared with vector alone. Comparing subretinal injections of AAV2.CAG.GFP vector alone versus co-injection with 18.75 μM HCQ in paired eyes in mice, mean GFP expression was 4.6-fold higher in retinae co-treated with HCQ without retinal toxicity. A comparative 5.9-fold effect was seen with an AAV8(Y733F).GRK1.GFP vector containing the photoreceptor-specific rhodopsin kinase promoter. While the mechanism of action remains to be fully elucidated, our data suggest that a single pulse of adjunctive HCQ could safely improve AAV transduction in vivo, thus providing a novel strategy for enhancing the clinical effects of gene therapy.

Therapeutic effects of lenvatinib in combination with rAd-p53 for the treatment of non-small cell lung cancer.

The aim of the present study was to analyze the effects of the combined treatment of lenvatinib and adenoviral delivered p53 gene (rAd-p53) on non-small cell lung cancer (NSCLC) cells and a total of 120 patients with NSCLC. The therapeutic effects of gene therapy of rAd-p53 and target therapy of Lenvatinib were investigated in NSCLC patients. The anti-tumor effects of combined treatment of llenvatinib and rAd-p53 was administered orally once-daily in NSCLC patients. Patients with NSCLC were divided into three groups and received lenvatinib (n=40), rAd-p53 (n=40) or combined treatment of lenvatinib and rAd-p53 (n=40) for a total of 30 days. Results showed that p53 was down-regulated and VEGFR, FGFR and PDGFR-β were up-regulated in NSCLC tissues compared to adjacent normal tissues. Combined treatment of Lenvatinib and rAd-p53 markedly inhibited NSCLC cell growth, migration and invasion, and promoted apoptosis compared to either lenvatinib or rAd-p53 alone. The most common treatment-related adverse events included hypertension, diarrhea, nausea, proteinuria and body weight loss. Outcomes indicated that combined treatment of lenvatinib and rAd-p53 markedly inhibited tumor growth compared to lenvatinib and rAd-p53 alone for NSCLC patients. Combined treatment of lenvatinib and rAd-p53 did not exhibit drug accumulation after 30-day treatment. In conclusion, these outcomes indicate that combined treatment of lenvatinib and rAd-p53 may be an efficient therapeutic schedule for the treatment of NSCLC patients.

Thrombomodulin domain 1 ameliorates diabetic nephropathy in mice via anti-NF-κB/NLRP3 inflammasome-mediated inflammation, enhancement of NRF2 antioxidant activity and inhibition of apoptosis

Chronic inflammatory processes have been increasingly shown to be involved in the pathogenesis of diabetes and diabetic nephropathy. Recently, we demonstrated that a lectin-like domain of thrombomodulin (THBD), which is known as THBD domain 1 (THBDD1) and which acts independently of protein C activation, neutralised an inflammatory response in a mouse model of sepsis. Here, therapeutic effects of gene therapy with adeno-associated virus (AAV)-carried THBDD1 (AAV-THBDD1) were tested in a mouse model of type 2 diabetic nephropathy. To assess the therapeutic potential of THBDD1 and the mechanisms involved, we delivered AAV-THBDD1 (10(11) genome copies) into db/db mice and tested the effects of recombinant THBDD1 on conditionally immortalised podocytes. A single dose of AAV-THBDD1 improved albuminuria, renal interstitial inflammation and glomerular sclerosis, as well as renal function in db/db mice. These effects were closely associated with: (1) inhibited activation of the nuclear factor κB (NF-κB) pathway and the NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome; (2) promotion of nuclear factor (erythroid-derived 2)-like 2 (NRF2) nuclear translocation; and (3) suppression of mitochondria-derived apoptosis in the kidney of treated mice. AAV-THBDD1 gene therapy resulted in improvements in a model of diabetic nephropathy by suppressing the NF-κB-NLRP3 inflammasome-mediated inflammatory process, enhancing the NRF2 antioxidant pathway and inhibiting apoptosis in the kidney.

Plerixafor+G-CSF-Mobilized Blood From Thalassemic Mice Provides High Yields Of Long-Term Repopulating Cells With Enhanced Engrafting Capacity : Implications For Human Stem Cell Gene Therapy

A durable therapeutic effect of gene therapy in β-thalassemia largely depends on the infusion of high numbers of genetically-modified hematopoietic stem cells (HSCs) with an enhanced engrafting potential.These requirements are necessary to compensate for the lack of a selective advantage of the thalassemic HSCs over the endogenous unmodified stem cells, especially if a nonmyeloablative conditioning is used. The higher HSC yields acquired by the mobilized peripheral blood and their faster time to engraftment as compared to bone marrow,qualifies mobilized blood cells as the preferable HSC source for genetic modification.To determine the optimal mobilization strategy for thalassemia, thalassemic (Hbbth345.2+) mice were mobilized with G-CSF or Plerixafor or Plerixafor+G-CSF and the yields of hematopoietic stem (Lin-sca-1+ckit+ cells-LSK cells) and progenitor cells (CFU-GM) were assayed by flow cytometry (FCM) and methylcellulose cultures and calculated in absolute numbers. C-kit+ progenitors mobilized by all the above approaches, were compared in terms of migration capacity towards SDF-1a, cell cycle status and CXCR4 and CD26 expression. To investigate the engrafting and long-term repopulation capacity of cells mobilized by different modes, whole blood from mobilized thalassemic 45.2+mice was infused into lethally irradiated PepBoy (45.1+) mice at a 3:1 (donors:recipient) ratio or as equal number of LSK cells, along with a fixed number of competitor 45.1+ cells (0.5x106). Donor chimerism was tested monthly by the frequency of 45.2+ cells in the recipients' blood by FCM analysis. Six months after primary transplantation, 2x106bm cells from the competitively engrafted mice were injected into lethally-irradiated secondary recipients in a noncompetitive manner.Plerixafor+G-CSF yielded significantly higher numbers of LSKs and CFU-GM over G-CSF-alone or Plerixafor-alone (p≤0.004) while Plerixafor-alone didn't further impove mobilization over G-CSF-alone. After competitive transplantation, Plerixafor+G-CSF-mobilized cells achieved earlier hematological reconstitution and increased donor chimerism over G-CSF- or Plerixafor-alone-mobilized cells (p≤0.05). To test whether the higher levels ofengraftment simply reflect the presence of higher numbers of stem/progenitor cells in the Plerixafor+G-CSF-mobilized graft (p<0.05) rather than an inherent qualitative difference of these cells, equal numbers (1X104) of LSK cells from each mobilization group was transplanted in a competitive manner. Plerixafor+G-CSF-mobilized LSKs showed again significantly higher engraftment levels than the single-agent mobilized LSKs (p<0.05), thus implying a qualitative benefit of this type of graft. This benefit was also evident after secondary transplantation, as the Plerixafor+G-CSF-cell secondary recipients exhibited the same or even higher levels of engraftment compared to primary engraftment, in contrast to the reduced secondary donor chimerism of mice that underwent transplantation from Plerixafor- or G-CSF- bone marrow primary chimeras, respectively. Plerixafor-mobilized cells showed decreased competiveness over G-CSF- or Plerixafor+G-CSF cells both in primary and secondary transplantations, a finding which could be attributed to the mobilization by Plerixafor of more actively proliferating cells compared to G-CSF or the Plerixafor+G-CSF combination (S/G2/M:G0+G1 ratio, p≤0.03) as well as to the higher CD26 expression in c-kit+ Plerixafor-mobilized progenitors (p=0.04).In conclusion, Plerixafor+G-CSF-mobilized peripheral blood represents an optimal graft for gene therapy of β-thalassemia because of the higher HSC-yields, the faster hematological recovery and the superiority in long-term engraftment over single-agent-mobilized blood cells. The therapeutic implications however, are not restricted to thalassemia but are of obvious relevance to all other stem cell gene therapy applications. Disclosures:No relevant conflicts of interest to declare.

Pupillometric analysis for assessment of gene therapy in Leber Congenital Amaurosis patients.

BackgroundObjective techniques to assess the amelioration of vision in patients with impaired visual function are needed to standardize efficacy assessment in gene therapy trials for ocular diseases. Pupillometry has been investigated in several diseases in order to provide objective information about the visual reflex pathway and has been adopted to quantify visual impairment in patients with Leber Congenital Amaurosis (LCA). In this paper, we describe detailed methods of pupillometric analysis and a case study on three Italian patients affected by Leber Congenital Amaurosis (LCA) involved in a gene therapy clinical trial at two follow-up time-points: 1 year and 3 years after therapy administration.MethodsPupillary light reflexes (PLR) were measured in patients who had received a unilateral subretinal injection in a clinical gene therapy trial. Pupil images were recorded simultaneously in both eyes with a commercial pupillometer and related software. A program was generated with MATLAB software in order to enable enhanced pupil detection with revision of the acquired images (correcting aberrations due to the inability of these severely visually impaired patients to fixate), and computation of the pupillometric parameters for each stimulus. Pupil detection was performed through Hough Transform and a non-parametric paired statistical test was adopted for comparison.ResultsThe developed program provided correct pupil detection also for frames in which the pupil is not totally visible. Moreover, it provided an automatic computation of the pupillometric parameters for each stimulus and enabled semi-automatic revision of computerized detection, eliminating the need for the user to manually check frame by frame. With reference to the case study, the amplitude of pupillary constriction and the constriction velocity were increased in the right (treated eye) compared to the left (untreated) eye at both follow-up time-points, showing stability of the improved PLR in the treated eye.ConclusionsOur method streamlined the pupillometric analyses and allowed rapid statistical analysis of a range of parameters associated with PLR. The results confirm that pupillometry is a useful objective measure for the assessment of therapeutic effect of gene therapy in patients with LCA.Trial registrationClinicalTrials.gov NCT00516477

O4-04-02: Therapeutic effects of gene therapy in the late treatment of prion diseases

O4-04-02: Therapeutic effects of gene therapy in the late treatment of prion diseases

Preventive and therapeutic effects of gene therapy using silica nanoparticles–binding of GM-CSF gene on white blood cell production in dogs with leukopenia

Our previous study has shown that granulocyte-macrophage colony-stimulating factor (GM-CSF) gene/silica nanoparticles have a leukocytosis effect in normal dogs. Therefore, this study was conducted to determine whether treatment of canine GM-CSF gene/silica nanoparticles has preventive or therapeutic effects in dogs with leukopenia. To induce leukopenia, vinblastine was administered intravenously at a dose of 2 mg/m(2) of body surface area on day 0. Then 7.5 microg GM-CSF/nanoparticles (1:100, w/w) were administered intravenously to each of four dogs in the prevention group on day 2 and an equivalent amount of GM-CSF/nanoparticles was administered to the post-nadir group on day 4 (other groups were administered phosphate-buffered saline intravenously). Therapeutic GM-CSF gene was expressed in peripheral blood mononuclear cells for 10 days and both the prevention and post-nadir groups showed significant increases in white blood cell counts when compared with the control group, as confirmed by complete blood count, differential count, and flow cytometry. GM-CSF/nanoparticles can be useful for correction of acute leukopenia, such as chemotherapy-induced myelosuppression, without developing neutralizing antibodies.

Gene Therapy for Laryngeal Paralysis

The surgical options for laryngeal paralysis only achieve static changes of vocal fold position. Laryngeal reinnervation procedures have had little impact on the return of dynamic laryngeal function. The development of a new treatment for laryngeal paralysis, aimed at the return of dynamic function and neurologic restoration and regeneration, is necessary. To assess the possibility of gene therapy for laryngeal paralysis aiming for the return of dynamic laryngeal function, we investigated the therapeutic effects of gene therapy using rat laryngeal paralysis models. In a rat vagal nerve avulsion model, we transferred glial cell line-derived neurotrophic factor (GDNF) gene into the nucleus ambiguus using an adenovirus vector. Two and 4 weeks after the GDNF gene transfer, a significantly larger number of surviving motoneurons was observed. These neuroprotective effects of GDNF gene transfer were enhanced by simultaneous brain-derived neurotrophic factor gene transfer. In a rat recurrent laryngeal nerve crush model, we transferred GDNF gene into recurrent laryngeal nerve fibers after crush injury. Two and 4 weeks after GDNF gene transfer, we observed significantly faster nerve conduction velocity and better vocal fold motion recovery. These results indicate that gene therapy could be a future treatment strategy for laryngeal paralysis. Further studies will be necessary to demonstrate the safety of the vector before clinical application.

Gene therapy for adenosine deaminase deficiency.

Gene therapy for severe combined immunodeficiency due to adenosine deaminase deficiency has moved from the early trials of safety and feasibility to recent studies demonstrating efficacy and clinical benefit. This review describes the latest advances in gene therapy trials for this condition using peripheral blood lymphocytes or hematopoietic progenitors. In the first patients with severe combined immunodeficiency due to adenosine deaminase deficiency treated with peripheral blood lymphocytes, transduced T cells have been shown to persist for over 10 years, expressing transgenic adenosine deaminase, but the therapeutic effect of gene therapy remained difficult to assess because of the concomitant treatment with bovine adenosine deaminase conjugated to polyethylene-glycol (PEG-ADA). A recent report showed that discontinuation of PEG-ADA resulted in a strong selective advantage of gene corrected T cells associated with restoration of T cell functions and antibody responses to neoantigen, but incomplete correction of the metabolic defect. Follow-up studies in patients treated with engineered hematopoietic progenitors in the early trials revealed low marking levels of long-term living progenitors and limited clinical effect. Recently, an improved gene transfer protocol in bone marrow CD34+ cells combined with low-dose busulfan resulted in multilineage, stable engraftment of transduced progenitors at substantial levels, restoration of immune functions, correction of the adenosine deaminase metabolic defect, and proven clinical benefit, in the absence of PEG-ADA. Overall, no adverse effect or toxicity has been observed in patients treated with adenosine deaminase gene transfer in mature lymphocytes or hematopoietic progenitors. Gene transfer in hematopoietic stem cells combined with nonmyeloablative conditioning is efficacious and might be extended to the treatment of other inherited and acquired disorders of the hematopoietic system.

Gene therapy for the treatment of peripheral vascular disease and coronary artery disease.

Owing to the easy accessibility and general importance of the vascular system, cardiovascular diseases, including postangioplasty and graft restenosis, have become one of the new areas for gene therapy and molecular medicine. Promising therapeutic effects have been obtained in animal models of vascular diseases and restenosis with the transfer of genes for vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), thymidine kinase, p53, retinoblastoma, bcl-x, tissue inhibitor of metalloproteinase (TIMP), hepatic growth factor (HGF) and nitric oxide synthase (NOS). Also, growth arrest homeobox gene and antisense oligonucleotides or antibodies against transcription factors or cell cycle regulatory proteins have produced beneficial therapeutic effects. However, further developments in gene delivery techniques and vectors are needed before the full therapeutic effects of gene therapy in vascular diseases can be obtained.