Optimization of human erythropoietin secretion from MLV-infected human primary fibroblasts used for encapsulated cell therapy

The ultrasonically treated nanoliposomes containing PCV2 DNA vaccine expressing gC1qR binding site mutant Cap is efficient in mice

Nowadays, vaccines are broadly used to prevent porcine circovirus type 2 (PCV2) infection-induced expenditures, but the virus is still spreading among pigs. The current PCV2 vaccines all rely on the immunogenicity of Cap, yet our previous studies found that Cap is also the major component mediating the PCV2 infection-induced immune suppression through its interaction with host gC1qR. Thereby, new vaccines are still necessary for PCV2 prevention and control. In this study, we constructed a new PCV2 DNA vaccine expressing the gC1qR binding site mutant Cap. We introduced the Intron A and WPRE elements into the vector to improve the Cap expression level, and fused the IL-2 secretory signal peptides to the N-terminal of Cap to mediate the secretion of Cap. We also screened and selected chemokines CXCL12, CCL22, and CCL25 to migrate dendritic cells. In addition, we contained the vectors with PEI and then ultrasonic them into nano size to enhance the entrance of the vectors. Finally, the animal experiments showed that the new PCV2 DNA vaccine expressing the gC1qR binding site mutant Cap could induce stronger humoral and cellular immune responses than the PCV2 DNA vaccine expressing the wild-type Cap and the non-ultrasonic treated PCV2 DNA vaccine in mice, and protect the mice from PCV2 infection and lung lesions. The results indicate the new PCV2 DNA vaccine expressing the gC1qR binding site mutant Cap has a certain development value, and provide new insight into the development of novel PCV2 vaccines.

Pushing the Right Buttons: Improving Efficacy of Therapeutic DNA Vectors

Gene therapy represents a potent therapeutical application for regenerative medicine. So far, viral and nonviral approaches suffer from major drawbacks hindering efficient gene therapeutic applicability: the immunogenicity of viral systems on the one hand, and the low gene transfer efficiency of nonviral systems on the other hand. Therefore, there is a high demand for improvements of therapeutical systems at several levels. This review summarizes different DNA vector modifications to enhance biological efficacy and efficiency of therapeutical vectors, aiming for low toxicity, high specificity, and biological efficacy-the cornerstones for successful translation of gene therapy into the clinic. We aim to provide a step-by-step instruction to optimize their vectors to achieve the desired outcome of gene therapy. Our review provides the means to either construct a potent gene therapeutic vector de novo or to specifically address a bottleneck in the chain of events mandatory for therapeutic success. Although most of the introduced techniques can be translated into different areas, this review primarily addresses improvements for applications in transient gene therapy in the field of tissue engineering.

Enhancing Transgene Expression from Recombinant AAV8 Vectors in Different Tissues Using Woodchuck Hepatitis Virus Post-Transcriptional Regulatory Element

Adeno-associated virus (AAV) vectors have been utilized extensively in gene therapy and gene function studies, as strong transgene expression is a prerequisite for positive outcomes. AAV8 was reported as the most efficient AAV serotype for transduction of the liver, brain and muscle compared with other serotypes. However, AAV8-mediated transduction of human hepatocytes is rather poor with approximately 20-fold lower efficiency compared with that of mouse hepatocytes. Therefore, we applied the woodchuck hepatitis virus post-transcriptional regulatory element (WPRE) to enhance AAV8-mediated transgene expression driven by a combination promoter (CAG promoter) with a CMV-IE enhancer and chicken beta-actin promoter for a more efficient viral vector. Transgene expression from recombinant AAV8 (rAAV8) vectors harboring a red fluorescent protein (RFP) reporter gene with or without WPRE were evaluated in vitro and in vivo. The results demonstrated that WPRE improved AAV8-mediated RFP expression in different cell lines with clear increases of transgene expression in the liver, brain or muscle of animals. The findings of this study will help to substantially reduce the quantity of viral particles that must be injected in order to reach a therapeutic level of transgene expression in gene therapy. Consequently, such dose reductions may lessen the potential risks associated with high doses of viral vectors.

Improvement of lentiviral transfer vectors using cis-acting regulatory elements for increased gene expression

Lentiviral vectors are an important tool for gene delivery in vivo and in vitro. The success of gene transfer approaches relies on high and stable levels of gene expression. To this end, several molecular strategies have been employed to manipulate these vectors towards improving gene expression in the targeted animal cells. Low gene expression can be accepted due to the weak transcription from the majority of available mammalian promoters; however, this obstacle can be in part overcome by the insertion of cis-acting elements that enhance gene expression in various expression contexts. In this work, we created different lentiviral vectors in which several posttranscriptional regulatory elements, namely the Woodchuck hepatitis posttranscriptional regulatory element (WPRE) and different specialized poly(A) termination sequences (BGH and SV40) were used to develop vectors leading to improved transgene expression. These vectors combine the advantages of restriction enzyme/ligation-independent cloning eliminating the instability and recombinogenic problems occurring from traditional cloning methods in lentiviral expression vectors and were tested by expressing GFP and the firefly Luciferase reporter gene from different cellular promoters in different cell lines. We show that the promoter activity varies between cell lines and is affected by the lentiviral genomic context. Moreover, we show that the combination of the WPRE element with the BGH poly(A) signal significantly enhances transgene expression. The vectors herein created can be easily modified and adapted without the need for extensive recloning making them a valuable tool for viral vector development.

Cell encapsulation technology as a novel strategy for human anti-tumor immunotherapy

Granulocyte-macrophage colony-stimulating factor (GM-CSF) as an adjuvant in autologous cell-based anti-tumor immunotherapy has recently been approved for clinical application. To avoid the need for individualized processing of autologous cells, we developed a novel strategy based on the encapsulation of GM-CSF-secreting human allogeneic cells. GM-CSF-producing K562 cells showed high, stable and reproducible cytokine secretion when enclosed into macrocapsules. For clinical development, the cryopreservation of these devices is critical. Thawing of capsules frozen at different time points displayed differences in GM-CSF release shortly after thawing. However, similar secretion values to those of non-frozen control capsules were obtained 8 days after thawing at a rate of >1000 ng GM-CSF per capsule every 24 h. For future human application, longer and reinforced capsules were designed. After irradiation and cryopreservation, these capsules produced >300 ng GM-CSF per capsule every 24 h 1 week after thawing. The in vivo implantation of encapsulated K562 cells was evaluated in mice and showed preserved cell survival. Finally, as a proof of principle of biological activity, capsules containing B16-GM-CSF allogeneic cells implanted in mice induced a prompt inflammatory reaction. The ability to reliably achieve high adjuvant release using a standardized procedure may lead to a new clinical application of GM-CSF in cell-based cancer immunization.

Lung adenocarcinoma originates from retrovirus infection of proliferating type 2 pneumocytes during pulmonary post-natal development or tissue repair

Jaagsiekte sheep retrovirus (JSRV) is a unique oncogenic virus with distinctive biological properties. JSRV is the only virus causing a naturally occurring lung cancer (ovine pulmonary adenocarcinoma, OPA) and possessing a major structural protein that functions as a dominant oncoprotein. Lung cancer is the major cause of death among cancer patients. OPA can be an extremely useful animal model in order to identify the cells originating lung adenocarcinoma and to study the early events of pulmonary carcinogenesis. In this study, we demonstrated that lung adenocarcinoma in sheep originates from infection and transformation of proliferating type 2 pneumocytes (termed here lung alveolar proliferating cells, LAPCs). We excluded that OPA originates from a bronchioalveolar stem cell, or from mature post-mitotic type 2 pneumocytes or from either proliferating or non-proliferating Clara cells. We show that young animals possess abundant LAPCs and are highly susceptible to JSRV infection and transformation. On the contrary, healthy adult sheep, which are normally resistant to experimental OPA induction, exhibit a relatively low number of LAPCs and are resistant to JSRV infection of the respiratory epithelium. Importantly, induction of lung injury increased dramatically the number of LAPCs in adult sheep and rendered these animals fully susceptible to JSRV infection and transformation. Furthermore, we show that JSRV preferentially infects actively dividing cell in vitro. Overall, our study provides unique insights into pulmonary biology and carcinogenesis and suggests that JSRV and its host have reached an evolutionary equilibrium in which productive infection (and transformation) can occur only in cells that are scarce for most of the lifespan of the sheep. Our data also indicate that, at least in this model, inflammation can predispose to retroviral infection and cancer.

Epo delivery by genetically engineered C2C12 myoblasts immobilized in microcapsules

ver the last half century, the use of erythropoietin (Epo) in the management of malignancies has been extensively studied. Originally viewed as the renal hormone responsible for red blood cell production, many recent in vivo and clinical approaches demonstrate that various tissues locally produce Epo in response to physical or metabolic stress. Thus, not only its circulating erythrocyte mass regulator activity but also the recently discovered nonhematological actions are being thoroughly investigated in order to fulfill the specific Epo delivery requirements for each therapeutic approach.

Human Embryonic Stem Cells and Gene Therapy

Human embryonic stem cells (hESCs) theoretically represent an unlimited supply of normal differentiated cells to engineer diseased tissues to regain normal function. However, before hESCs can be useful as human therapeutics, technologies must be developed to provide them with the specific signals required to differentiate in a controlled fashion, to regulate and/or shut down the growth of hESCs and their progeny once they have been transferred to the recipient, and to circumvent the recognition of non-autologous hESC-derived cells as foreign. In the context that gene therapy technologies represent strategies to deliver biological signals to address all of these challenges, this review sets out a framework for combined gene transfer/hESC therapies. We discuss how hESCs are derived, characterized, and differentiated into specific cell lineages, and we summarize the characteristics of the 500 hESC lines reported to date. The successes and failures of gene transfer to hESCs are reviewed for both non-viral and viral vectors, as are the challenges to successful use of gene transfer in developing hESC therapy. We also consider gene transfer as a means of facilitating growth and isolation of genetically modified hESCs and as a mechanism for mitigating adverse effects associated with administration of hESCs or their derivatives. Finally, we evaluate the challenges that are likely to be encountered in translating the promise of hESCs to the clinic.

WPRE-mediated enhancement of gene expression is promoter and cell line specific

The success of gene therapy approaches relies on sufficiently high levels of expression of the therapeutic gene. However, if tissue specific or tumour specific gene expression is desired, a lower level of transgene expression usually has to be accepted due to the weakness of the majority of available tissue or tumour specific promoters. This obstacle can in part be overcome by the insertion of viral cis-acting elements that enhance gene expression in various expression vector contexts regardless of the respective promoter. We designed a series of murine leukaemia virus (MLV)-based retroviral promoter conversion (ProCon) vectors that contain the woodchuck hepatitis post-transcriptional regulatory element (WPRE) and evaluated its use by measuring enhanced green fluorescent protein (EGFP) levels and viral titres. In viral vector packaging cells, when the EGFP encoding gene was transcribed from the MLV promoter, incorporation of the WPRE resulted in a marked improvement of the vectors in terms of EGFP expression and virus titres. However, in infected cells after promoter conversion had taken place, the effect of the WPRE became promoter and cell line dependent. When the EGFP gene was transcribed from the heterologous mouse mammary tumour virus (MMTV) promoter the same beneficial role of the WPRE on transgene expression was observed in all eight cell lines tested. In contrast, when EGFP gene expression was driven by the murine whey acidic protein (WAP) promoter, the positive effect of the WPRE could only be observed in two cell lines whereas expression was actually reduced in the six other cell lines tested. This decrease of EGFP expression was not only demonstrated at the protein level but also manifested on the RNA level.

Long-Term Expression of Erythropoietin from Myoblasts Immobilized in Biocompatible and Neovascularized Microcapsules

The present paper investigates the long-term functionality of an ex vivo gene therapy approach based on cell microencapsulation for the continuous delivery of erythropoietin (EPO) without implementation of immunosuppressive protocols. Polymer microcapsules (0.5 ml) loaded with EPO-secreting C(2)C(12) myoblasts and releasing 15,490 +/- 600 IU EPO/24 h were implanted in the peritoneum and subcutaneous tissue of syngeneic and allogeneic mice. High and constant hematocrit levels were maintained for more than 100 days in all implanted mice. Capsules retrieved from the peritoneum were free-floating or forming small capsule clusters, and we detected only a weak fibroblast outgrowth in capsules adhered to organs, whereas capsules explanted from the subcutaneous region appeared altogether as a richly vascularized structure with no signs of major host reaction. Interestingly, the functionality of capsules implanted in the allogeneic mice persisted until day 210 after implantation. These results highlight the feasibility of cell encapsulation technology for the long-term delivery of EPO independent of the method of administration and the mouse strain.

B-cell-specific transgene expression using a self-inactivating retroviral vector with human CD19 promoter and viral post-transcriptional regulatory element

Retroviral gene transfer resulting in transgene expression selectively restricted to specific cell lineages would be desirable for many gene therapeutic applications. Such transcriptional targeting of retroviruses can be accomplished by employing eukaryotic control elements in self-inactivating (SIN) retroviral vectors, but use of these vectors is complicated by an accompanying reduction in viral titers. To overcome this restriction and address the influence of the post-transcriptional regulatory element of the Woodchuck hepatitis virus (WPRE) on viral titers and transgene expression, we developed SIN-vectors with and without WPRE. Using the enhancer-promoter of the Spleen Focus Forming virus (SFFV) to direct eGFP expression to multiple hematopoietic lineages, we show that WPRE significantly (>10 x) increased viral titers (>10(6) per ml of unconcentrated supernatant) and transgene expression in NIH3T3 cells in vitro. Gene expression in vivo was significantly lowered in lymphoid cells, but not in myeloid cells when WPRE was present. Furthermore, the use of WPRE in combination with the B-cell lineage-specific CD19 promoter significantly increased viral titers and allowed targeting of transgene expression by SIN-vectors specifically to B cells throughout their development in primary and secondary lymphoid organs.

Survival of Encapsulated Human Primary Fibroblasts and Erythropoietin Expression Under Xenogeneic Conditions

Allogeneic cells are the most attractive source for cell transplantation, as the use of xenogeneic cells is hampered by safety concerns and the use of autologous cells involves practical difficulties. The immune rejection of allogeneic cells can be overcome by physical immunoprotection provided by polymer encapsulation. To study the variability of cell and donor sources, we compared different primary human cells as candidates for gene therapy-mediated delivery of human erythropoietin (hEpo). DARC-3.1 fibroblasts, MDX-01 fibroblasts, and ARPE-19 retinal pigment epithelial cells were encapsulated into polyethersulfone hollow fibers and implanted for 1 month in nude mice as well as in immunocompetent and FK506-immunosuppressed mice to test their in vivo resistance, with the assumption that xenogeneic conditions constitute a stringent model for human application. DARC-3.1 fibroblasts showed the best survival, prompting us to evaluate cell lineages from the same donor (DARC-3.2) or another donor (DARC-4.3 and DARC-4.4). With the exception of DARC-4.3, the remaining three lineages showed comparable survival in immunocompetent C3H and DBA/2J mice. DARC-3.1 fibroblasts were retrovirally engineered with hEpo cDNA, reaching a secretion level of 170 IU of hEpo per 10(6) cells per day. Encapsulated DARC-3.1-hEpo cells led to significantly increased hematocrits in the various hosts and under various transplantation conditions. The present study shows that encapsulated primary human DARC-3.1 fibroblasts are able to survive under xenogeneic conditions and, once engineered with hEpo cDNA, to increase the hematocrit of transplanted mice.