Implementing the human artificial chromosome gene therapy platform remains challenging, but continuous animal model research will advance the platform closer to clinical trials

2021 ◽  
Author(s):  
Moataz Dowaidar

A normal degree of ectopic gene expression, infinite retention in target cells without chromosomal integration, minimal risk of cell or neoplastic transformation, and minimal or no immunogenicity are all critical characteristics for vectors employed in gene therapy. HACs were produced and used as autonomous vectors to compensate for genetic defects in mouse and human cell cultures. Bottom-up human artificial chromosomes (HACs) were studied for functional transgene expression in vitro and in vivo mice models. The primary advantages of synthesized alphoid-HACs over top-down HACs are their defined and documented structure, as well as their relative simplicity of modification in adding numerous Cre-lox-type transgen loading sites. The HAC transfer method's efficacy has greatly increased in recent years. Despite significant progress in developing alphoid-HAC-based gene therapy models, the technology still has a number of drawbacks, including low HAC efficiency, complex repeated HAC alphoid-DNA structure, large DNA fragmentation difficulties outside eukaryotic cells, inefficient transfer of chromosomes to target cells, and variable mitotic stability. The quantity and quality of PSC-derived or reversibly immortalized stem/precursor cells that can transplant specific tissues are also critical determinants in the effectiveness of HAC-based tissue replacement therapies. Translating the HAC-based gene therapy platform remains difficult, but ongoing animal model research will move the HAC platform closer to clinical trials.

2018 ◽  
Vol 9 (1) ◽  
pp. 4-11 ◽  
Author(s):  
Aparna Bansal ◽  
Himanshu

Introduction: Gene therapy has emerged out as a promising therapeutic pave for the treatment of genetic and acquired diseases. Gene transfection into target cells using naked DNA is a simple and safe approach which has been further improved by combining vectors or gene carriers. Both viral and non-viral approaches have achieved a milestone to establish this technique, but non-viral approaches have attained a significant attention because of their favourable properties like less immunotoxicity and biosafety, easy to produce with versatile surface modifications, etc. Literature is rich in evidences which revealed that undoubtedly, non–viral vectors have acquired a unique place in gene therapy but still there are number of challenges which are to be overcome to increase their effectiveness and prove them ideal gene vectors. Conclusion: To date, tissue specific expression, long lasting gene expression system, enhanced gene transfection efficiency has been achieved with improvement in delivery methods using non-viral vectors. This review mainly summarizes the various physical and chemical methods for gene transfer in vitro and in vivo.


2021 ◽  
Author(s):  
Moataz Dowaidar

Gene therapy involves transferring genetic material (DNA or RNA) to repair, regulate or replace genes to cure a disease. One of the most crucial barriers is successful delivery of the targeted gene into the target tissue. Various vector-based approaches have been developed to deliver the transgene to the target cells. In different cancers, numerous of these vectors are being developed for purposes such as immunotherapy, suicide gene therapy, microRNA (miRNA) focused treatment, oncogene silencing, and gene editing using CRISPR/Cas9. This article reviews several alternatives to cancer gene therapy, as well as their preclinical and clinical outcomes, possible limitations, and overall therapy effects. Ways of delivering cancer gene therapy include direct methods for introducing genetic material. Nonviral vectors are easy to manufacture and may be chemically modified to increase their usefulness. Cationic polymers such as Poly-L-Lysine (PLL) and Polyethylenimine (PEI-SS) are the most extensively used polycationic polymers for gene transfer, particularly in vitro. Many RNAi-based therapeutic approaches are approaching the clinical stage, and nanocarriers are likely to play a crucial role in treating specific cancers. In the previous decade, non-viral approaches were used in more than 17 percent of all gene therapy trials. The message is that this is a safe and effective technique for transferring genes to cancer patients who need it to be a safe, successful therapy. Exosomes were developed to carry oncogene-specific short interfering RNA. Sushrut and colleagues revealed that exosomes provide superior carriers of short RNA and prevent tumor growth than liposomes. Inhalation-based gene therapy (aerosol-mediated gene delivery) has gained pace as a feasible treatment approach, especially for lung cancer. Because the intended transgene is steered to specific cells/tissues, this should further increase therapeutic efficiency.


Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 455-455 ◽  
Author(s):  
Federico Mingozzi ◽  
Marcela V. Maus ◽  
Denise E. Sabatino ◽  
Daniel J. Hui ◽  
John E.J. Rasko ◽  
...  

Abstract Efforts to establish an adeno-associated viral (AAV) vector-mediated gene therapy for the treatment of hemophilia B have been hindered by an immune response to the viral capsid antigen. Preclinical studies in small and large animal models of the disease showed long-term factor IX (F.IX) transgene expression and correction of the phenotype. However, in a recent phase I/II clinical trial in humans (Manno et al., Nat. Med. 2006), after hepatic gene transfer with an AAV-2 vector expressing human F.IX transgene, expression lasted for only a few weeks, declining to baseline concurrently with a peak in liver enzymes. We hypothesized that T cells directed towards AAV capsid antigens displayed by transduced hepatocytes were activated and these mediated destruction of the transduced hepatocytes, thereby causing loss of transgene expression and a transient transaminitis. Peripheral blood mononuclear cells isolated from AAV-infused subjects were stained with an AAV capsid-specific MHC class I pentamer either directly or after in vitro expansion. Two weeks after vector infusion 0.14% of circulating CD8+ T cells were capsid-specific on direct staining, and five weeks after infusion the capsid-specific population had expanded to 0.5% of the circulating CD8+ T cells, indicating proliferation of this T cell subset. By 20 weeks after vector infusion, the capsid-specific CD8+ T cell population had contracted to the level seen at 2 weeks. The expansion and contraction of this capsid-specific CD8+ T cell population paralleled the rise and fall of serum transaminases in the subject observed. Subsequent ex vivo studies of PBMC showed the presence of a readily expandable pool of capsid-specific CD8+ T cells up to 2.5 years post vector-infusion. Similarly, we were able to expand AAV-specific CD8+ T cells from peripheral blood of normal donors, suggesting the existence of a T cell memory pool. Expanded CD8+ T cells were functional as evidenced by specific lysis of HLA-matched target cells and by IFN-γsecretion in response to AAV epitopes. It has been argued that potentially harmful immune responses could be avoided by switching AAV serotypes, however, capsid protein sequences are highly conserved among different serotypes, as are some immunodominant epitopes that we identified. Indeed, we demonstrated that capsid-specific CD8+ T cells from AAV-infused hemophilic subjects functionally cross-react with AAV-8. Moreover, cells expanded from normal donors with AAV-2 vector capsids proliferated upon culture with AAV-8 capsids, demonstrating that both vectors could be processed appropriately in vitro to present the epitopic peptide to capsid-specific T cells. This suggests that AAV-2-specific memory CD8+ T cells normally present in humans likely would expand upon exposure to AAV-8 capsid epitopes. We conclude that the use of immunomodulatory therapy may be a better approach to achieving durable transgene expression in the setting of AAV-mediated gene therapy.


2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
G J J Boink ◽  
J Wang ◽  
M Klerk ◽  
V M Christoffels ◽  
H L Tan ◽  
...  

Abstract Background Sodium channel gene therapy carries significant potential for treatment of acquired and inherited arrhythmias. However, delivery is challenging to the length of the transgene that exceeds the packaging capacity of Adeno-Associated Virus (AAV), the most advanced long-term gene therapy vector to date. To overcome this issue, we have developed dual AAV vectors for the delivery of the skeletal muscle sodium channel 1 (SkM1). Purpose To achieve cardiac delivery of SkM1 and other large therapeutic genes using dual AAV vectors. Methods Dual AAV vectors were constructed, containing SkM1 gene fragments that allow reconstruction in the target cells by trans-splicing and recombination. An oversized single AAV vector containing SkM1 served as a control. HEK293T cells and neonatal rat ventricular cardiomyocytes (NRVMs) were transduced with dual AAV vectors or oversized single AAV vector at an MOI of 50,000 per vector. Etoposide and Teniposide were added 2h before transduction to improve the efficiency. SkM1 mRNA and protein were isolated 3 days post transduction and the expression was detected by RT-qPCR and Western blot. Results Robust full-length SkM1 protein expression was detected in both HEK cells and NRVMs transduced by dual AAV vectors while no expression was detected in the control. Transduction with dual AAV vectors also showed significantly higher SkM1 mRNA expression in both cell types (4 to 29-fold) comparing to oversized single AAV vector. Moreover, a relatively high level of SkM1 mRNA expression was achieved in NRVM; 22-fold higher than the native cardiac sodium channel. Conclusion Efficient delivery and expression of SkM1 was successfully achieved in vitro by hybrid dual AAV vectors. This approach supports the application of SkM1 and other sodium channel antiarrhythmic gene therapies. In vivo validation and functional testing are currently in on-going.


Author(s):  
Ryosuke Kurauchi ◽  
Hiroi Kasai ◽  
Tatsuya Ito

Medical products comprising human cells, genes, and tissues have been developed for clinical applications worldwide, and their developmental environment has been established. These products can be imported and exported, but marketing authorization regulations are complicated among regions. This investigation was conducted to identify the characteristics of medical products comprising human cells, genes, and tissues. We used website data, books from survey companies, and reports from public agencies to conduct two investigations. We used website data to conduct a general information survey of 143 cell-therapy and gene-therapy products sold in 24 countries and public assessment reports to individually survey non-clinical and clinical developments of 18 cell-therapy and gene-therapy products developed in Japan and the European Union (EU). The first survey revealed that the numbers of products used in orthopedic surgery and dermatology have increased since 2000, and the numbers of hematological products have increased since 2011. The second investigation revealed that fewer orphaned products were developed in Japan than in the EU. The most appropriate dose was 1.2 × 108 cells per injection per adult. Clinical trials to determine the most appropriate dose were conducted in the EU but not in Japan. No non-clinical immunogenicity tests for autogenous products were conducted in Japan or the EU. Pharmacokinetics tests were not individually performed for sheet-form products. Both in vivo and in vitro pharmacological tests were more likely to be conducted in the EU, while only one or the other was conducted in Japan. Furthermore, in Japan, carcinogenicity tests were performed based on non-clinical technical guidance, while in the EU, these tests were determined according to each product's features. Fewer clinical trials were performed, and fewer subjects per product were used in Japan than in the EU. Many aspects of the clinical and non-clinical development of medical products comprising human cells, genes, and tissues differ between Japan and the EU. Analyzing these differences will enable the safe and rapid distribution of these products to clinical sites.


Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 2531-2531
Author(s):  
Paraskevi Diamanti ◽  
William J Barendt ◽  
Benjamin C Ede ◽  
Charlotte V. Cox ◽  
Allison Blair

Abstract Current therapies for the treatment of childhood acute lymphoblastic leukaemia (ALL) have resulted in vastly improved survival rates of around 90% in recent years. Despite these successes, around 15% of patients die of relapse. It is possible that ALL may be maintained by subpopulations of cells, known as leukaemia stem cells (LSC), that are resistant to therapy and subsequent relapses may arise from these cells. Parthenolide (PTL), a naturally occurring sesquiterpene lactone, is an NF-κB inhibitor that kills leukaemia cells by apoptosis and/or increase of reactive oxygen species. PTL has been shown to be remarkably effective against several LSC subpopulations in vivo, with complete ablation of leukaemia. In a minority of cases, leukaemia burden was reduced following PTL treatment but not eliminated. Therefore, it may be necessary to combine PTL with other agents to improve killing of all LSC subpopulations. Another pathway of increasing interest in the treatment of leukaemias is the BCL-2 family. BCL-2 has been shown to be overexpressed in over 66% of B-ALL cases and is associated with tumourigenesis in several cancers. ABT-263 is an inhibitor of BCL-2, BCL-xL and BCL-w, it has been shown to selectively target AML LSC and is in early clinical trials in lymphoid malignancies. ABT-199 is another promising inhibitor that is currently in clinical trials for CLL. ABT-199 is specific for BCL-2 and has minimal risk for thrombocytopenia. In the present study the effects of both ABT-263 and ABT-199 alone or in combination with PTL were assessed in childhood ALL samples to determine whether toxicity to leukaemia cells could be improved in vitro and in vivo. The viability of bulk cells from 11 B cell precursor (BCP) ALL cases and 11 cord blood (CB) samples following drug treatment for 24 hours were assessed using flow cytometry by staining with Annexin V and propidium iodide. Initially, PTL was used at a range of 1 to 10μM, ABT-263 from 0.025 to 1μM and ABT-199 from 0.1 to 10μM. Only PTL and ABT-263 significantly reduced the viability of ALL cells compared to CB with IC50 values of 1.2μM and 0.125μM (P≤0.01 and P≤0.0015), respectively. In vitro drug combination studies demonstrated synergism when combining PTL with ABT-263 in a 9.5:1 ratio using the Chou Talalay model. The viability of ALL cells following combination therapy (1.2μM PTL with 0.125μM ABT-263) was reduced to 38.3±32.5%, while CB viability was unaffected (96.9±29%, P<0.0001). Using this combined dose, toxicity to ALL cells was increased by a further 35% compared to PTL alone and by 25% compared to ABT-263 alone. Even at the highest combined doses tested (9.6μM PTL: 1μM ABT-263) normal CB remained relatively unaffected with 73.3±25% surviving. The effects of these drugs alone and in combination were also assessed in LSC subpopulations in 3 of these cases. Unsorted ALL cells, CD34+/CD19+ and CD34-/CD19+ subpopulations were the most responsive with viabilities ranging from 17.6±4% to 23.9±11% using 1.2μM PTL and 0.125μM ABT-263. The CD34+/CD19- and CD34-/CD19- cells were more resistant with 70.3±40% and 73.3±15% surviving, respectively. However, since we have previously shown that the effects of in vitro drug treatment do not always accurately reflect the response in vivo, it was important to evaluate the effects of these drugs in mice with established leukaemia. NOD/LtSz-scid IL-2Rγc null (NSG) mice were inoculated with 1-1.15x106 unsorted BCP-ALL cells. Once the levels of leukaemia engraftment in murine peripheral blood reached ≥ 0.1%, mice were treated with 100mg/kg ABT-263 or ABT-199 and vehicle by oral gavage for 21 consecutive days and the levels of leukaemia burden were monitored weekly. Results to date demonstrate that leukaemia levels continued to rise in placebo-treated mice, reaching 49.2±7% by day 21, while the levels in ABT-263 and ABT-199 treated mice were significantly lower at 8.6±10% and 23.7±12%, respectively (P<0.0001). The use of ABT-263 and ABT-199 significantly improved the survival of NSG compared to untreated controls (P=0.0001). These data indicate that combining PTL with ABT-263 shows promising results in the killing of bulk and LSC populations in BCP-ALL. Ongoing in vivo studies will assess the potential of using BCL-2 inhibitors in combination with PTL compared to standard chemotherapeutics. Disclosures No relevant conflicts of interest to declare.


2016 ◽  
Vol 90 (8) ◽  
pp. 3929-3943 ◽  
Author(s):  
Isa Murrell ◽  
Gavin S. Wilkie ◽  
Andrew J. Davison ◽  
Evelina Statkute ◽  
Ceri A. Fielding ◽  
...  

ABSTRACTClinical human cytomegalovirus (HCMV) strains invariably mutate when propagatedin vitro. Mutations in gene RL13 are selected in all cell types, whereas in fibroblasts mutants in the UL128 locus (UL128L; genes UL128, UL130, and UL131A) are also selected. In addition, sporadic mutations are selected elsewhere in the genome in all cell types. We sought to investigate conditions under which HCMV can be propagated without incurring genetic defects. Bacterial artificial chromosomes (BACs) provide a stable, genetically defined source of viral genome. Viruses were generated from BACs containing the genomes of strains TR, TB40, FIX, and Merlin, as well as from Merlin-BAC recombinants containing variant nucleotides in UL128L from TB40-BAC4 or FIX-BAC. Propagation of viruses derived from TR-BAC, TB40-BAC4, and FIX-BAC in either fibroblast or epithelial cells was associated with the generation of defects around the prokaryotic vector, which is retained in the unique short (US) region of viruses. This was not observed for Merlin-BAC, from which the vector is excised in derived viruses; however, propagation in epithelial cells was consistently associated with mutations in the unique longb′ (UL/b′) region, all impacting on gene UL141. Viruses derived from Merlin-BAC in fibroblasts had mutations in UL128L, but mutations occurred less frequently with recombinants containing UL128L nucleotides from TB40-BAC4 or FIX-BAC. Viruses derived from a Merlin-BAC derivative in which RL13 and UL128L were either mutated or repressed were remarkably stable in fibroblasts. Thus, HCMV containing a wild-type gene complement can be generatedin vitroby deriving virus from a self-excising BAC in fibroblasts and repressing RL13 and UL128L.IMPORTANCEResearchers should aim to study viruses that accurately represent the causative agents of disease. This is problematic for HCMV because clinical strains mutate rapidly when propagatedin vitro, becoming less cell associated, altered in tropism, more susceptible to natural killer cells, and less pathogenic. Following isolation from clinical material, HCMV genomes can be stabilized by cloning into bacterial artificial chromosomes (BACs), and then virus is regenerated by DNA transfection. However, mutations can occur not only during isolation prior to BAC cloning but also when virus is regenerated. We have identified conditions under which BAC-derived viruses containing an intact, wild-type genome can be propagatedin vitrowith minimal risk of mutants being selected, enabling studies of viruses expressing the gene complement of a clinical strain. However, even under these optimized conditions, sporadic mutations can occur, highlighting the advisability of sequencing the HCMV stocks used in experiments.


Biomedicines ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 107
Author(s):  
Narmatha Gurumoorthy ◽  
Fazlina Nordin ◽  
Gee Jun Tye ◽  
Wan Safwani Wan Kamarul Zaman ◽  
Min Hwei Ng

Lentiviral vectors (LVs) play an important role in gene therapy and have proven successful in clinical trials. LVs are capable of integrating specific genetic materials into the target cells and allow for long-term expression of the cDNA of interest. The use of non-integrating LVs (NILVs) reduces insertional mutagenesis and the risk of malignant cell transformation over integrating lentiviral vectors. NILVs enable transient expression or sustained episomal expression, especially in non-dividing cells. Important modifications have been made to the basic human immunodeficiency virus (HIV) structures to improve the safety and efficacy of LVs. NILV-aided transient expression has led to more pre-clinical studies on primary immunodeficiencies, cytotoxic cancer therapies, and hemoglobinopathies. Recently, the third generation of self-inactivating LVs was applied in clinical trials for recombinant protein production, vaccines, gene therapy, cell imaging, and induced pluripotent stem cell (iPSC) generation. This review discusses the basic lentiviral biology and the four systems used for generating NILV designs. Mutations or modifications in LVs and their safety are addressed with reference to pre-clinical studies. The detailed application of NILVs in promising pre-clinical studies is also discussed.


2012 ◽  
Vol 67 (5) ◽  
pp. 16-23 ◽  
Author(s):  
D. V. Glazkova ◽  
E. V. Bogoslovskaya ◽  
M. L. Markelov ◽  
G. A. Shipulin ◽  
V. V. Pokrovskii

Current methods of HIV treatment can contain a progression of the disease; however they do not lead to a cure. Lifelong antiretroviral therapy is therefore necessary, leading to problems of cost and toxicity of chemical drugs. The recent advances in science have allowed a new approach to the HIV-treatment — gene therapy. In the present publication we focus on one strategy of the gene therapy called «intracellular immunization». The strategy is based on the introducing of antiviral genes into the HIV-sensitive cells. We highlight the mechanisms of action of various antiviral genetic agents and discuss some issues concerning target cells and genes delivery. Finally we summarize the results of certain gene therapy clinical trials. 


2017 ◽  
Vol 37 (6) ◽  
Author(s):  
Jaitip Tipanee ◽  
Yoke Chin Chai ◽  
Thierry VandenDriessche ◽  
Marinee K. Chuah

Transposons derived from Sleeping Beauty (SB), piggyBac (PB), or Tol2 typically require cotransfection of transposon DNA with a transposase either as an expression plasmid or mRNA. Consequently, this results in genomic integration of the potentially therapeutic gene into chromosomes of the desired target cells, and thus conferring stable expression. Non-viral transfection methods are typically preferred to deliver the transposon components into the target cells. However, these methods do not match the efficacy typically attained with viral vectors and are sometimes associated with cellular toxicity evoked by the DNA itself. In recent years, the overall transposition efficacy has gradually increased by codon optimization of the transposase, generation of hyperactive transposases, and/or introduction of specific mutations in the transposon terminal repeats. Their versatility enabled the stable genetic engineering in many different primary cell types, including stem/progenitor cells and differentiated cell types. This prompted numerous preclinical proof-of-concept studies in disease models that demonstrated the potential of DNA transposons for ex vivo and in vivo gene therapy. One of the merits of transposon systems relates to their ability to deliver relatively large therapeutic transgenes that cannot readily be accommodated in viral vectors such as full-length dystrophin cDNA. These emerging insights paved the way toward the first transposon-based phase I/II clinical trials to treat hematologic cancer and other diseases. Though encouraging results were obtained, controlled pivotal clinical trials are needed to corroborate the efficacy and safety of transposon-based therapies.


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