Recombinant Sendai virus-mediated gene transfer to vasculature: a new class of efficient gene transfer vector to the vascular system

Generation of a photocontrollable recombinant bovine parainfluenza virus type 3

Bovine parainfluenza virus type 3 (BPIV3) is a promising vaccine vector against various respiratory virus infections, including the human PIV3, respiratory syncytial virus, and severe acute respiratory syndrome-coronavirus 2 infections. In this study, we combined the Magnet system and reverse genetic approach to generate photocontrollable BPIV3. An optically controllable Magnet gene was inserted into the H2 region of the BPIV3 large protein gene, which encodes an RNA-dependent RNA polymerase. The generated photocontrollable BPIV3 grew in specific regions of the cell sheet only when illuminated with blue light, suggesting that spatiotemporal control can aid in safe clinical applications of BPIV3.

Intranasal Sendai virus-based SARS-CoV-2 vaccine using a mouse model

The coronavirus disease 2019 (COVID-19) epidemic remains worldwide. The usefulness of the intranasal vaccine and boost immunization against severe acute respiratory syndrome-related coronavirus (SARS-CoV-2) has recently received much attention. We developed an intranasal SARS-CoV-2 vaccine by loading the receptor binding domain of the S protein (S-RBD) of SARS-CoV-2 as an antigen into an F-deficient Sendai virus vector. After the S-RBD-Fd antigen with trimer formation ability was intranasally administered to mice, S-RBD-specific IgM, IgG, IgA, and neutralizing antibody titers were increased in serum or bronchoalveolar lavage fluid for 12 weeks. Furthermore, in mice that received a booster dose at week 8, a marked increase in neutralizing antibodies in the serum and bronchoalveolar lavage fluid was observed at the final evaluation at week 12, which neutralized the pseudotyped lentivirus expressing the SARS-CoV-2 spike protein, indicating the usefulness of the Sendai virus-based SARS-CoV-2 intranasal vaccine.

Advances in RNA Viral Vector Technology to Reprogram Somatic Cells: The Paramyxovirus Wave

Ethical issues are a significant barrier to the use of embryonic stem cells in patients due to their origin: human embryos. To further the development of stem cells in a patient application, alternative sources of cells were sought. A process referred to as reprogramming was established to create induced pluripotent stem cells from somatic cells, resolving the ethical issues, and vectors were developed to deliver the reprogramming factors to generate induced pluripotent stem cells. Early viral vectors used integrating retroviruses and lentiviruses as delivery vehicles for the transcription factors required to initiate reprogramming. However, because of the inherent risk associated with vectors that integrate into the host genome, non-integrating approaches were explored. The development of non-integrating viral vectors offers a safer alternative, and these modern vectors are reliable, efficient, and easy to use to achieve induced pluripotent stem cells suitable for direct patient application in the growing field of individualized medicine. This review summarizes all the RNA viral vectors in the field of reprogramming with a special focus on the emerging delivery vectors based on non-integrating  Paramyxoviruses, Sendai and measles viruses. We discuss their design and evolution towards being safe and efficient reprogramming vectors in generating induced pluripotent stem cells from somatic cells.

Sequential actions of immune effector cells induced by viral activation of dendritic cells to eliminate murine neuroblastoma

PURPOSE

In preclinical trails, we reported the antitumor effect of dendritic cells activated with Sendai virus (rSeV/DC) combined with γ-irradiation against neuroblastoma. However, what kind of effector cells for the combined therapy were used to show the antitumor effect was unclear. In this study, we performed radiation and rSeV/DC therapy in vivo and examined the effector cells involved.

METHODS

Dendritic cells were cultured from bone marrow cells, activated with SeV and administered intratumorally at 10⁶ weekly for 3weeks. Radiation was administered at 4Gy/time × 3 times. During the treatment, CD4+ and CD8+ cells and natural killer (NK) cells were removed by antibodies.

RESULTS

Complete remission of neuroblastoma was observed in 62.5% of individuals in the combined therapy group. By depleting the effector cells using antibodies, the tumor increased in size from an early stage of treatment in the CD4+ and NK cell-depleted group. In contrast, the tumor increased in size in the late stage of treatment in the CD8+ cell-depleted group.

CONCLUSION

The combination of radiation and rSeV/DC therapy induces different effector cells, depending on the time point during treatment.

LEVEL OF EVIDENCE

V.

Simple Derivation of Spinal Motor Neurons from ESCs/iPSCs Using Sendai Virus Vectors

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal degenerative disorder of motor neurons (MNs). Embryonic stem cells (ESCs)/induced pluripotent stem cells (iPSCs) now help us to understand the pathomechanisms of ALS via disease modeling. Various methods to differentiate ESCs/iPSCs into MNs by the addition of signaling molecules have been reported. However, classical methods require multiple steps, and newer simple methods using the transduction of transcription factors run the risk of genomic integration of the vector genes. Heterogeneity of the expression levels of the transcription factors also remains an issue. Here we describe a novel approach for differentiating human and mouse ESCs/iPSCs into MNs using a single Sendai virus vector encoding three transcription factors, LIM/homeobox protein 3, neurogenin 2, and islet-1, which are integration free. This single-vector method, generating HB9-positive cells on day 2 from human iPSCs, increases the ratio of MNs to neurons compared to the use of three separate Sendai virus vectors. In addition, the MNs derived via this method from iPSCs of ALS patients and model mice display disease phenotypes. This simple approach significantly reduces the efforts required to generate MNs, and it provides a useful tool for disease modeling.

Constitutively active form of natriuretic peptide receptor 2 ameliorates experimental pulmonary arterial hypertension

We recently found a constitutively active mutant of natriuretic peptide receptor 2 (caNPR2; V883M), which synthesizes larger amounts of cyclic guanosine monophosphate (cGMP) intracellularly without any ligand stimulation than existing drugs. The aim of this study was to investigate the therapeutic effects of gene transduction using caNPR2 for pulmonary arterial hypertension (PAH). In vitro gene transduction into human pulmonary arterial smooth muscle cells using Sendai virus (SeV) vectors carrying caNPR2 induced 10,000-fold increases in the synthesis of cGMP without ligand stimulation, and the proliferation of caNPR2-expressing cells was significantly attenuated. The PAH model rats generated by hypoxia and the administration of SU5416 were then treated with SeV vectors through a direct injection into the left pulmonary artery. Right ventricular systolic pressure was significantly decreased 2 weeks after the treatment, while systemic blood pressure remained unchanged. Histological analyses revealed that the medial wall thickness and occlusion rate of pulmonary arterioles were significantly improved in caNPR2-treated lungs. Neither the systemic integration of virus vectors nor side effects were observed. The massive stimulation of cGMP synthesis by gene therapy with caNPR2 was safe and effective in a PAH rat model and, thus, has potential as a novel therapy for patients with severe progressive PAH.

The metamorphosis of vascular stents: passive structures to smart devices

The role of nanotechnology enabled techniques in the evolution of vascular stents.

Generation of Induced Pluripotent Stem Cells from Human Peripheral T Cells Using Sendai Virus in Feeder-free Conditions

Recently, iPSCs have attracted attention as a new source of cells for regenerative therapies. Although the initial method for generating iPSCs relied on dermal fibroblasts obtained by invasive biopsy and retroviral genomic insertion of transgenes, there have been many efforts to avoid these disadvantages. Human peripheral T cells are a unique cell source for generating iPSCs. iPSCs derived from T cells contain rearrangements of the T cell receptor (TCR) genes and are a source of antigen-specific T cells. Additionally, T cell receptor rearrangement in the genome has the potential to label individual cell lines and distinguish between transplanted and donor cells. For safe clinical application of iPSCs, it is important to minimize the risk of exposing newly generated iPSCs to harmful agents. Although fetal bovine serum and feeder cells have been essential for pluripotent stem cell culture, it is preferable to remove them from the culture system to reduce the risk of unpredictable pathogenicity. To address this, we have established a protocol for generating iPSCs from human peripheral T cells using Sendai virus to reduce the risk of exposing iPSCs to undefined pathogens. Although handling Sendai virus requires equipment with the appropriate biosafety level, Sendai virus infects activated T cells without genome insertion, yet with high efficiency. In this protocol, we demonstrate the generation of iPSCs from human peripheral T cells in feeder-free conditions using a combination of activated T cell culture and Sendai virus.

Reprogramming of Human Fibroblasts with Non-integrating RNA Virus on Feeder-Free or Xeno-Free Conditions

Recent advances in generating induced pluripotent stem cells have radically advanced the field of regenerative medicine by making possible the production of patient-specific pluripotent stem cells from somatic cells. However, a major obstacle to the use of iPSC for therapeutic applications is the potential genomic modifications resulted from viral insertion of transgenes in the cellular genome. Second, the culture of iPSCs and adult cells often requires the use of animal products, which hinder the generation of clinical-grade iPSCs. We report here the generation of iPSCs by an RNA Sendai virus vector that does not integrate transgenes into the cell's genome. In addition, reprogramming can be performed on a feeder-free or xeno-free condition without containing animal products. Generation of an integrant-free iPSCs in these conditions will facilitate the studies of iPSCs in cell-based therapies.

Cellular unfolded protein response against viruses used in gene therapy

Viruses are excellent vehicles for gene therapy due to their natural ability to infect and deliver the cargo to specific tissues with high efficiency. Although such vectors are usually "gutted" and are replication defective, they are subjected to clearance by the host cells by immune recognition and destruction. Unfolded protein response (UPR) is a naturally evolved cyto-protective signaling pathway which is triggered due to endoplasmic reticulum (ER) stress caused by accumulation of unfolded/misfolded proteins in its lumen. The UPR signaling consists of three signaling pathways, namely PKR-like ER kinase, activating transcription factor 6, and inositol-requiring protein-1. Once activated, UPR triggers the production of ER molecular chaperones and stress response proteins to help reduce the protein load within the ER. This occurs by degradation of the misfolded proteins and ensues in the arrest of protein translation machinery. If the burden of protein load in ER is beyond its processing capacity, UPR can activate pro-apoptotic pathways or autophagy leading to cell death. Viruses are naturally evolved in hijacking the host cellular translation machinery to generate a large amount of proteins. This phenomenon disrupts ER homeostasis and leads to ER stress. Alternatively, in the case of gutted vectors used in gene therapy, the excess load of recombinant vectors administered and encountered by the cell can trigger UPR. Thus, in the context of gene therapy, UPR becomes a major roadblock that can potentially trigger inflammatory responses against the vectors and reduce the efficiency of gene transfer.

Derivation of transgene-free human induced pluripotent stem cells from human peripheral T cells in defined culture conditions

Recently, induced pluripotent stem cells (iPSCs) were established as promising cell sources for revolutionary regenerative therapies. The initial culture system used for iPSC generation needed fetal calf serum in the culture medium and mouse embryonic fibroblast as a feeder layer, both of which could possibly transfer unknown exogenous antigens and pathogens into the iPSC population. Therefore, the development of culture systems designed to minimize such potential risks has become increasingly vital for future applications of iPSCs for clinical use. On another front, although donor cell types for generating iPSCs are wide-ranging, T cells have attracted attention as unique cell sources for iPSCs generation because T cell-derived iPSCs (TiPSCs) have a unique monoclonal T cell receptor genomic rearrangement that enables their differentiation into antigen-specific T cells, which can be applied to novel immunotherapies. In the present study, we generated transgene-free human TiPSCs using a combination of activated human T cells and Sendai virus under defined culture conditions. These TiPSCs expressed pluripotent markers by quantitative PCR and immunostaining, had a normal karyotype, and were capable of differentiating into cells from all three germ layers. This method of TiPSCs generation is more suitable for the therapeutic application of iPSC technology because it lowers the risks associated with the presence of undefined, animal-derived feeder cells and serum. Therefore this work will lead to establishment of safer iPSCs and extended clinical application.

Development of Sendai virus vectors and their potential applications in gene therapy and regenerative medicine

Gene delivery/expression vectors have been used as fundamental technologies in gene therapy since the 1980s. These technologies are also being applied in regenerative medicine as tools to reprogram cell genomes to a pluripotent state and to other cell lineages. Rapid progress in these new research areas and expectations for their translation into clinical applications have facilitated the development of more sophisticated gene delivery/expression technologies. Since its isolation in 1953 in Japan, Sendai virus (SeV) has been widely used as a research tool in cell biology and in industry, but the application of SeV as a recombinant viral vector has been investigated only recently. Recombinant SeV vectors have various unique characteristics, such as low pathogenicity, powerful capacity for gene expression and a wide host range. In addition, the cytoplasmic gene expression mediated by this vector is advantageous for applications, in that chromosomal integration of exogenous genes can be undesirable. In this review, we introduce a brief historical background on the development of recombinant SeV vectors and describe their current applications in gene therapy. We also describe the application of SeV vectors in advanced nuclear reprogramming and introduce a defective and persistent SeV vector (SeVdp) optimized for such reprogramming.

RNA-based tools for nuclear reprogramming and lineage-conversion: towards clinical applications

The therapeutic potential of induced pluripotent stem cells (iPSCs) is well established. Safety concerns remain, however, and these have driven considerable efforts aimed at avoiding host genome alteration during the reprogramming process. At present, the tools used to generate human iPSCs include (1) DNA-based integrative and non-integrative methods and (2) DNA-free reprogramming technologies, including RNA-based approaches. Because of their combined efficiency and safety characteristics, RNA-based methods have emerged as the most promising tool for future iPSC-based regenerative medicine applications. Here, I will discuss novel recent advances in reprogramming technology, especially those utilizing the Sendai virus (SeV) and synthetic modified mRNA. In the future, these technologies may find utility in iPSC reprogramming for cellular lineage-conversion, and its subsequent use in cell-based therapies.

Generation of induced pluripotent stem cells with CytoTune, a non-integrating Sendai virus

One of the major obstacles in generating induced pluripotent stem cells for research or downstream applications is the potential modifications of cellular genome as a result of using integrating viruses during reprogramming. Another major disadvantage of reprogramming cells with integrating vectors is that silencing and activation of transgenes are unpredictable, which may affect terminal differentiation potential and increase the risk of using iPSC-derived cells. Here we describe a protocol for the generation of induced pluripotent stem cells using a non-integrating RNA virus, Sendai virus, to efficiently generate transgene-free iPSCs starting with different cell types as well as in feeder-free conditions.

Advances in growth factor delivery for therapeutic angiogenesis

Therapeutic angiogenesis is a new revascularization strategy involving the administration of growth factors to induce new vessel formation. The biology and delivery of angiogenic growth factors involved in vessel formation have been extensively studied but success in translating the angiogenic capacity of growth factors into benefits for vascular disease patients is still limited. This could be attributed to issues related to patient selection, growth factor delivery methods or lack of vessel maturation. Comprehensive understanding of the cellular and molecular cross-talk during the different stages of vascular development is needed for the design of efficient therapeutic strategies. The presentation of angiogenic factors either in series or in parallel using a strategy that mimics physiological events, such as concentration and spatio-temporal profiles, is an immediate requirement for functional blood vessel formation. This review provides an overview of the recent delivery strategies of angiogenic factors and discusses targeting neovascular maturation as a promising approach to induce stable and functional vessels for therapeutic angiogenesis.

Generation of human-induced pluripotent stem cells by a nonintegrating RNA Sendai virus vector in feeder-free or xeno-free conditions

The generation of induced pluripotent stem cells (iPSCs) from somatic cells has enabled the possibility of providing unprecedented access to patient-specific iPSC cells for drug screening, disease modeling, and cell therapy applications. However, a major obstacle to the use of iPSC for therapeutic applications is the potential of genomic modifications caused by insertion of viral transgenes in the cellular genome. A second concern is that reprogramming often requires the use of animal feeder layers and reagents that contain animal origin products, which hinder the generation of clinical-grade iPSCs. Here, we report the generation of iPSCs by an RNA Sendai virus vector that does not integrate into the cells genome, providing transgene-free iPSC line. In addition, reprogramming can be performed in feeder-free condition with StemPro hESC SFM medium and in xeno-free (XF) conditions. Generation of an integrant-free iPSCs generated in xeno-free media should facilitate the safe downstream applications of iPSC-based cell therapies.

Provision of continuous maturation signaling to dendritic cells by RIG-I-stimulating cytosolic RNA synthesis of Sendai virus

Dendritic cell (DC)-based immunotherapy has potential for treating infections and malignant tumors, but the functional capacity of DC must be assessed in detail, especially maturation and Ag-specific CTL priming. Recent reports suggest that DC that are provided with continuous maturation signals in vivo after transfer into patients are required to elicit the full DC functions. We demonstrate in this study that the rSendai virus vector (SeV) is a novel and ideal stimulant, providing DC with a continuous maturation signal via viral RNA synthesis in the cytosol, resulting in full maturation of monocyte-derived DC(s). Both RIG-I-dependent cytokine production and CD4 T cell responses to SeV-derived helper Ags are indispensable for overcoming regulatory T cell suppression to prime melanoma Ag recognized by T cell-1-specific CTL in the regulatory T cell abundant setting. DC stimulated via cytokine receptors, or TLRs, do not show these functional features. Therefore, SeV-infected DC have the potential for DC-directed immunotherapy.

Efficient transfection of sendai virus vector to mouse pancreatic stem cells in the floating state

Sendai virus (SeV) vectors can efficiently introduce foreign genes without toxicity into various organs and are expected to be clinically applicable. We previously compared the transfectional efficiency of SeV and adenovirus (AdV) vectors by assessing the transfer of the green fluorescent protein (GFP) gene to pancreatic stem cells. Although the gene transfer efficiency was similar between these vectors, SeV vector had a lower toxicity in comparison to the AdV vector. In this study, we assessed the gene transfer efficiency of SeV vector in the floating state to pancreatic stem cells. The efficiency of gene transfer was much higher at all time points and at all concentrations in the floating state versus in the adhesion state. In addition, the pancreatic stem cells transfected with SeV in the floating state maintained their differentiation ability. These data suggest that SeV transfection to pancreatic stem cells in the floating state may be useful in gene transfer technology.

Transplantation of Sendai viral angiopoietin-1-modified mesenchymal stem cells for ischemic limb disease

Sendai viral vector (SeV) is emerging as a promising vector for gene therapy. However, little information is available regarding the combination of SeV-mediated gene and mesenchymal stem cell (MSC) therapy in dealing with ischemic diseases. In this study, we infected SeV to the MSCs in vitro; and injected MSCs modified with SeV harboring human angiopoietin-1 gene (SeVhAng-1) into the ischemic limb of rats in vivo. We found SeV had high transductive efficiency to the MSCs. Both MSCs and SeVhAng-1-modified MSCs improved the blood flow recovery and increased the capillary density of the ischemic limb, compared with the control. However, in contrast to MSCs, SeVhAng-1-modified MSCs had a better improvement of blood flow recovery in the ischemic limb. We further found the ischemic limb injected with SeVhAng-1-modified MSCs had strong expression of p-Akt, which improved survival of MSCs injected into the ischemic limb. This indicated SeVhAng-1 modification enhanced angiogenetic effect of MSCs by both angiogenesis and cell protection. We conclude that SeVhAng-1-modified MSCs may serve as a more effective tool in dealing with ischemic limb disease.

Development of viral vectors for use in cardiovascular gene therapy

Cardiovascular disease represents the most common cause of mortality in the developed world but, despite two decades of promising pre-clinical research and numerous clinical trials, cardiovascular gene transfer has so far failed to demonstrate convincing benefits in the clinical setting. In this review we discuss the various targets which may be suitable for cardiovascular gene therapy and the viral vectors which have to date shown the most potential for clinical use. We conclude with a summary of the current state of clinical cardiovascular gene therapy and the key trials which are ongoing.

VEGF-C regulates lymphangiogenesis and capillary stability by regulation of PDGF-B

Emerging evidence indicates that the tight communication between vascular endothelial cells and mural cells using platelet-derived growth factor (PDGF)-BB is essential for capillary stabilization during the angiogenic process. However, little is known about the related regulator that determines PDGF-BB expression. Using murine models of therapeutic neovascularization, we here show that a typical lymphangiogenic factor, vascular endothelial growth factor (VEGF)-C, is an essential regulator determining PDGF-BB expression for vascular stabilization via a paracrine mode of action. The blockade of VEGF type 3 receptor (VEGFR3) using neutralizing antibody AFL-4 abrogated FGF-2-mediated limb salvage and blood flow recovery in severely ischemic hindlimb. Interestingly, inhibition of VEGFR3 activity not only diminished lymphangiogenesis, but induced marked dilatation of capillary vessels, showing mural cell dissociation. In these mice, VEGF-C and PDGF-B were upregulated in the later phase after induced ischemia, on day 7, when exogenous FGF-2 expression had already declined, and blockade of VEGFR3 or PDGF-BB activities diminished PDGF-B or VEGF-C expression, respectively. These results clearly indicate that VEGF-C is a critical mediator, not only for lymphangiogenesis, but also for capillary stabilization, the essential molecular mechanism of communication between endothelial cells and mural cells during neovascularization.

RECOMBINANT SENDAI VIRUS FOR EFFICIENT GENE TRANSFER TO HUMAN AIRWAY EPITHELIUM

Recombinant Sendai virus (rSeV) infects respiratory epithelial cells in animal models and cultures of undifferentiated human nasal cells. It was the aim of this study to investigate the capability of rSeV to express a transgene in human airway epithelium. Differentiated human airway epithelial cells were generated using air-liquid interface culture techniques. Application of rSeV coding for green fluorescence protein (GFP) onto the apical surface (using a multiplicity of infection of 3) resulted in expression of the transgene in more than 90% of the cells followed by decreasing numbers of positive cells during the observation time of 3 weeks. The infection of human respiratory epithelial cells is mediated by sialic acid residues at the apical surface. Despite the secretion of interleukin (IL)-8 and the replication of rSeV in the epithelial cells, the authors could not detect any cytopathic effect after the infection. In conclusion, rSeV infects differentiated human airway epithelial cells with high efficiency. Transgene expression is transient and accompanied by the secretion of an inflammatory cytokine.

Recombinant Sendai Virus-Mediated Gene Transfer to Mouse Pancreatic Stem Cells

Efficient gene transfer into stem cells is essential for the basic research and for therapeutic applications in gene-modified regenerative medicine. Adenovirus (AdV) vectors, one of the most commonly used types of vectors, can mediate high, albeit transient, levels of expression of the transgene in pancreatic stem/progenitor cells. However, high multiplicity of infection (MOI) with AdV vectors can result in cellular toxicity. Therefore, AdV vectors have been of limited usefulness in clinical applications. In this study, we investigated the in vitro gene transfer efficiency of Sendai virus (SeV) vectors, a paramyxovirus vector that can efficiently introduce foreign genes without toxicity into several cell types, including pancreatic stem cells. The dose-dependent GFP expression of pancreatic stem cells transfected with SeV vectors after 48 h of culture at 37°C was observed. The transfection of pancreatic stem cells with SeV vectors and AdV vectors results in equal expression of the transgene (GFP expression) in the cells after 48 h of culture at 37°C. Although the transfection of pancreatic stem cells with AdV vectors at high MOIs was cytotoxic, transfection with SeV vectors at high MOIs was rarely cytotoxic. In addition, pancreatic stem cells transfected with SeV maintained their differentiation ability. These data suggest that SeV could provide advantages with respect to safety issues in gene-modified regenerative medicine.

Sendai viral vector mediated angiopoietin-1 gene transfer for experimental ischemic limb disease

Sendai virus vector is emerging as a promising vector for gene therapy, and angiopoietin-1 (Ang-1) has been reported to improve the blood flow recovery in the ischemic limb or heart. In this study, we constructed a human Ang-1-expressing Sendai viral vector (SeVhAng-1) and injected it into the ischemic limb of rats. We found that SeVhAng-1 improved the blood flow recovery and increased the capillary density of the ischemic limb, compared with the controls. We also found that SeVhAng-1 increased p-Akt during the early period of limb ischemia, and decreased apoptosis in ischemic limb. It suggests that SeVhAng-1 may serve as a potential therapeutic tool in ischemic limb disease.

Comparison of sendai virus-mediated gene transfer efficiency to adhesive and floating adipose tissue-derived stem cells

Sendai virus (SeV) vectors have potential clinical applications because they can efficiently introduce foreign genes without toxicity into various organs. A recent study reported the green fluorescent protein (GFP) gene transfer to adipose tissue-derived stem cells (ASCs) with SeV vectors results in more efficient expression of GFP than AdV and identified the preservation of the multilineage potential of ASCs transfected with SeV vectors. This study assessed the gene transfer efficiency to floating ASCs with SeV vectors. Although a slight cytotoxicity was observed, the efficiency of gene transfer to cells in the floating state was much higher at all times and all concentrations at MOIs of 2, 10, and 20 than in the adhesion state. Moreover, ASCs transfected with SeV vectors in floating state have the same potential for their differentiation into specific tissues, such as adipocytes and osteocytes, as untransfected ASCs. These data suggest that SeV transfection to ASCs in the floating state could therefore be useful for gene transfer technology.

Efficient induction of transgene-free human pluripotent stem cells using a vector based on Sendai virus, an RNA virus that does not integrate into the host genome

Induced pluripotent stem cells (iPSC) have been generated from somatic cells by introducing reprogramming factors. Integration of foreign genes into the host genome is a technical hurdle for the clinical application. Here, we show that Sendai virus (SeV), an RNA virus and carries no risk of altering host genome, is an efficient solution for generating safe iPSC. Sendai-viral human iPSC expressed pluripotency genes, showed demethylation characteristic of reprogrammed cells. SeV-derived transgenes were decreased during cell division. Moreover, viruses were able to be easily removed by antibody-mediated negative selection utilizing cell surface marker HN that is expressed on SeV-infected cells. Viral-free iPSC differentiated to mature cells of the three embryonic germ layers in vivo and in vitro including beating cardiomyocytes, neurons, bone and pancreatic cells. Our data demonstrated that highly-efficient, non-integrating SeV-based vector system provides a critical solution for reprogramming somatic cells and will accelerate the clinical application.

Newly-developed Sendai virus vector for retinal gene transfer: reduction of innate immune response via deletion of all envelope-related genes

BACKGROUND

Recombinant Sendai virus vectors (rSeV) constitute a new class of cytoplasmic RNA vectors that have shown efficient gene transfer in various organs, including retinal tissue; however, the related immune responses remain to be overcome in view of clinical applications. We recently developed a novel rSeV from which all envelope-related genes were deleted (rSeV/dFdMdHN) and, in the present study, assess host immune responses following retinal gene transfer.

METHODS

rSeV/dFdMdHN or conventional F-gene deleted rSeV (rSeV/dF) was injected into subretinal space of adult Wistar rats or C57BL/6 mice. The transgene expression and histopathological findings were assessed at various time points. Immunological assessments, including the expression of proinflammatory cytokines, natural killer (NK)-cell activity, as well as SeV-specific cytotoxic T lymphocytes (CTLs) and antibodies, were performed following vector injection.

RESULTS

rSeV/dFdMdHN showed high gene transfer efficiency into the retinal pigment epithelium at an equivalent level to that seen with rSeV/dF. In the early phase, the upregulation of proinflammatory cytokines, local inflammatory cell infiltration and tissue damage that were all prominently seen in rSeV/dF injection were dramatically diminished using rSeV/dFdMdHN. NK cell activity was also decreased, indicating a reduction of the innate immune response. In the later phase, on the other hand, CTL activity and anti-SeV antibodies were similarly induced, even using rSeV/dFdMdHN, and resulted in transient transgene expression in both vector types.

CONCLUSIONS

Deletion of envelope-related genes of rSeV dramatically reduces the vector-induced retinal damage and may extend the utility for ocular gene transfer; however, further studies regulating the acquired immune response are required to achieve long-term transgene expression of rSeV.

Gene delivery to the vasculature mediated by low-titre adeno-associated virus serotypes 1 and 5

BACKGROUND

Vascular gene therapy requires safe and efficient gene transfer in vivo. Recombinant adeno-associated virus (AAV) is a promising viral vector but its use in the vasculature has produced conflicting results and serotypes other than AAV2 have not been intensively studied. We investigated the efficiency of alternative AAV serotypes for vascular gene delivery in vitro and in vivo.

METHODS

Vascular cell lines were transduced in vitro with AAV vectors. Rabbit carotid arteries were transduced with AAV1, 2 and 5 encoding enhanced green fluorescent protein (eGFP) ( approximately 1.4 x 10(9) DNAse-resistant particles (drp)). Gene transfer in vivo was assessed at 14 and 28 days. High-titre doses of AAV2 encoding beta-galactosidase in vivo were also studied.

RESULTS

In vitro, transgene expression was not observed in endothelial cells using AAV2 whereas the use of serotypes 1 and 5 resulted in detectable levels of transgene expression. Coronary artery smooth muscle cells (CASMCs) transduced with AAV2 demonstrated higher levels of GFP expression than AAV1 or 5. Transgene expression in vivo was noted using low-titre AAV1 and AAV5 ( approximately 1.4 x 10(9) drp) in the media and adventitia. Only delivery of AAV1eGFP resulted in neointimal formation (3/7 vessels examined), with transgene expression noted in the neointima. Transgene expression with AAV2 was not detected in any layer of the blood vessel wall using low titre ( approximately 10(9) drp). However, high-titre ( approximately 10(11) drp) AAV2 resulted in transduction of cells in the media and adventitia but not the endothelium.

CONCLUSIONS

AAV1 and AAV5 have advantages over AAV2 for vascular gene delivery at low titres.

Recombinant Sendai Virus-Mediated Gene Transfer to Adipose Tissue-Derived Stem Cells (ASCs)

Adipose tissue-derived stem cells (ASCs) are expected to have clinical applications as well as other stem cells, because ASCs can be obtained safely from adult donors and used in autologous therapies without concern about rejection and the need for immunosuppression. However, the use of gene transfer with Sendai virus (SeV) vectors, which can efficiently introduce foreign genes without toxicity into several cells, with ASCs has not yet been investigated. This study documents on the use of SeV vectors for gene transfer to ASCs. The dose-dependent GFP expression of ASCs transfected with SeV vectors after 48 h of culture at 37°C was first evaluated. Next, the cellular toxicity of ASCs transfected with SeV vectors was verified. In addition, SeV vectors were compared with adenovirus (AdV) vectors. Finally, the time-dependent GFP expression of ASCs transfected with SeV vectors was evaluated. The results showed that transfection of ASCs with SeV vectors results in more efficient expression of transgene (GFP expression) in the ASCs than with AdV vectors after 48 h of culture at 37°C. Moreover, while the transfection of ASCs with AdV vectors at high MOIs was cytotoxic (a lot of transfected cells died) that of ASCs with SeV vectors at high MOIs was not necessarily cytotoxic. In addition, the preservation of multilineage ASCs transfected with SeV was observed. In conclusion, this is the first report describing the successful use of SeV-mediated gene transfer in ASCs, and the results indicate that SeV may thus provide advantages with respect to safety issues in gene therapy.

In vivo repopulation of cytoplasmically gene transferred hematopoietic cells by temperature-sensitive mutant of recombinant Sendai viral vector

Recent clinical studies revealed 'proof of concept' of gene therapy targeting hematopoietic stem cells (HSCs) to treat hematopoietic disorders. However, vector integration-related adverse events of retroviral vectors have slowed progress in this field. As an initial step to overcoming this hurdle, we examined the potential of an improved cytoplasmic RNA vector, temperature-sensitive mutant non-transmissible recombinant Sendai virus (ts-rSeV/dF), for gene transfer to murine HSCs and progenitors. Both conventional vector and ts-rSeV/dF-GFP showed efficient gene transfer to T-lymphocyte-depleted syngeneic bone marrow cells (BMCs) (>85%), but only BMCs treated with ts-rSeV/dF-GFP but not with conventional vector efficiently repopulated in the recipient mice, associated with multilineage differentiation in vitro and in vivo. To our knowledge, this is the first demonstration of the in vivo reconstruction of hematopoietic series by cytoplasmically gene transferred BMCs, that warrants further investigation to realize this strategy in clinical settings.

Current Status of Cardiovascular Gene Therapy

Gene transfer for the therapeutic modulation of cardiovascular diseases is an expanding area of gene therapy. During the last decade several approaches have been designed for the treatment of hyperlipidemias, post-angioplasty restenosis, hypertension, and heart failure, and for protection of vascular by-pass grafts and promotion of therapeutic angiogenesis. Adenoviruses (Ads) and adeno-associated viruses (AAVs) are currently the most efficient vectors for delivering therapeutic genes into the cardiovascular system. Gene transfer using local gene delivery techniques have been shown to be superior to less-targeted intra-arterial or intra-venous applications. To date, no gene therapy drugs have been approved for clinical use in cardiovascular applications. In preclinical studies of therapeutic angiogenesis, various growth factors such as vascular endothelial growth factors (VEGFs) and fibroblast growth factors (FGFs), have shown positive results. Gene therapy also appears to have potential clinical applications in improving the patency of vascular grafts and in treating heart failure. Post-angioplasty restenosis, hypertension, and hyperlipidemias (excluding homozygotic familial hypercholesterolemia) can usually be managed satisfactorily by conventional approaches, and are therefore less favored areas for gene therapy. The development of technologies that can ensure long-term, targeted, and regulated gene transfer, and a careful selection of target patient populations, will be very important for the progress of cardiovascular gene therapy in clinical applications.

Enhanced gene transfer into brain capillary endothelial cells using Antp-modified DNA-loaded nanoparticles

Brain capillary endothelial cells (BCECs) have been considered as one of the primary targets for cerebral gene therapy. However, the cells, well-known for their poor function of endocytosis, are difficult to be transfected by general non-viral vectors. The aim of this study was to enhance the efficiency of transfection and expression in BCECs of DNA/polymer nanoparticles with the modification of membrane-penetrating peptide, Antennapedia peptide (Antp) polyethylenimine (PEI) and polyamidoamine (PAMAM) were chosen to prepare Antp-modified DNA-loaded nanoparticles with a complex coacervation technique. After a 20-min transfection, the efficiency, in terms of transfection and expression, of DNA/PEI NP or DNA/PAMAM NP was enhanced significantly with the modification of Antp. After a 3-h transfection of DNA/Antp/PEI NP, there was no difference in cellular uptake but an enhancement in gene expression, compared to DNA/PEI NP alone. However, both the transfection and expression efficiency of DNA/PAMAM NP were enhanced using Antp. These observations suggest that Antp can increase the membrane-penetrating ability of DNA-loaded nanoparticles, which can be employed as novel non-viral gene vectors.

Sendai Virus Vector-Mediated Transgene Expression in the Cochlea in vivo

We injected a recombinant Sendai virus (SeV) vector into the guinea pig cochlea using two different approaches--the scala media and scala tympani--and investigated which cell types took up the vector. The hearing threshold shift and distribution of transfected cells in animals using the scala media approach were different compared to those using the scala tympani approach. SeV can transfect very different types of cells, including stria vascularis, spiral ganglion neurons, and sensory epithelia of the organ of Corti, and fibrocytes of the scala tympani. Because SeV vectors can potentially deliver stimuli to the cochlea to induce hair cell regeneration, it may be a powerful tool for repairing the organ of Corti.

Sendai virus-mediated gene delivery into hepatocytes via isolated hepatic perfusion

The recombinant Sendai virus vector is a promising tool for human gene therapy, capable of inducing high-level expression of therapeutic genes in tissue cells in situ. The target tissues include airway epithelium, blood vessels, skeletal muscle, retina and the central nervous system, but application to hepatic tissues has not yet been achieved, because direct intraportal injection of the vector is not feasible. We report an efficient and harmless procedure of gene delivery by recombinant Sendai virus into rat parenchymal hepatocytes, based on isolated hepatic perfusion with controlled inflow. Critical parameters for successful hepatic gene delivery are a brief preperfusion period (25 degrees C, 5 min); appropriate vector concentration in the perfusate (10(7) pfu/ml); moderate portal vein pressure (12 mmHg) and a brief hyperthermic postperfusion period (42 degrees C, 5 min). Under these optimized conditions, marker genes were expressed in most parenchymal hepatocytes without significant damage to hepatic tissues. Furthermore, expression of the marker genes was undetectable in nonhepatic tissues, including the gonads, indicating that this approach strictly targets hepatic tissues and thus offers good clinical potential for human gene therapy.

Induction of Efficient Antitumor Immunity Using Dendritic Cells Activated by Recombinant Sendai Virus and Its Modulation by Exogenous IFN-β Gene

Dendritic cell (DC)-based cancer immunotherapy has been paid much attention as a new and cancer cell-specific therapeutic in the last decade; however, little clinical outcome has been reported. Current limitations of DC-based cancer immunotherapy include sparse information about which DC phenotype should be administered. We here report a unique, representative, and powerful method to activate DCs, namely recombinant Sendai virus-modified DCs (SeV/DC), for cancer immunotherapy. In vitro treatment of SeV without any bioactive gene solely led DCs to a mature phenotype. Even though the expression of surface markers for DC activation ex vivo did not always reach the level attained by an optimized amount of LPS, superior antitumor effects to B16F1 melanoma, namely tumor elimination and survival, were obtained with use of SeV-GFP/DC as compared with those seen with LPS/DC in vivo, and the effect was enhanced by SeV/DC-expressing IFN-beta (SeV-murine IFN-beta (mIFN-beta)/DC). In case of the treatment of an established tumor of B16F10 (7-9 mm in diameter), a highly malignant subline of B16 melanoma, SeV-modified DCs (both SeV-GFP/DC and SeV-mIFN-beta/DC), but not immature DC and LPS/DC, dramatically improved the survival of animals. Furthermore, SeV-mIFN-beta/DC but not other DCs could lead B16F10 tumor to the dormancy, associated with strongly enhanced CD8+ CTL responses. These results indicate that rSeV is a new and powerful tool as an immune booster for DC-based cancer immunotherapy that can be significantly modified by IFN-beta, and SeV/DC, therefore, warrants further investigation as a promising alternative for cancer immunotherapy.

Diabetic Microangiopathy in Ischemic Limb Is a Disease of Disturbance of the Platelet-Derived Growth Factor-BB/Protein Kinase C Axis but Not of Impaired Expression of Angiogenic Factors

Diabetic foot is caused by microangiopathy and is suggested to be a result of impaired angiogenesis. Using a severe hindlimb ischemia model of streptozotocin-induced diabetic mice (STZ-DM), we show that diabetic foot is a disease solely of the disturbance of platelet-derived growth factor B-chain homodimer (PDGF-BB) expression but not responses of angiogenic factors. STZ-DM mice frequently lost their hindlimbs after induced ischemia, whereas non-DM mice did not. Screening of angiogenesis-related factors revealed that only the expression of PDGF-BB was impaired in the STZ-DM mice on baseline, as well as over a time course after limb ischemia. Supplementation of the PDGF-B gene resulted in the prevention of autoamputation, and, furthermore, a protein kinase C (PKC) inhibitor restored the PDGF-BB expression and also resulted in complete rescue of the limbs of the STZ-DM mice. Inhibition of overproduction of advanced-glycation end product resulted in dephosphorylation of PKC-α and restored expression of PDGF-BB irrespective of blood sugar and HbA1c, indicating that advanced-glycation end product is an essential regulator for PKC/PDGF-BB in diabetic state. These findings are clear evidence indicating that diabetic vascular complications are caused by impairment of the PKC/PDGF-B axis, but not by the impaired expression of angiogenic factors, and possibly imply the molecular target of diabetic foot.

Ex vivo electroporation as a potent new strategy for nonviral gene transfer into autologous vein grafts

Gene transfer to vein grafts has therapeutic potential to prevent late graft failure; however, certain issues, including efficacy and safety, have hindered the clinical application of this treatment modality. Here, we report the successful and efficient gene transfer of plasmid DNA via ex vivo electroporation into veins as well as into vein grafts. Two approaches were used: one involved transluminal in situ gene transfer using a T-shaped electrode (the “Lu” method), and the other was an adventitial ex vivo approach using an electroporation cuvette followed by vein grafting (the “Ad” method). The Lu method was carried out at 10 V, with optimal gene transfer efficiency in the in situ jugular veins of rabbits, and transgene expression was observed primarily in endothelial cells. However, when these veins were grafted into the arterial circulation, no luciferase activity was detected; this effect was probably due to the elimination of the gene-transferred cells as a result of endothelial denudation. In contrast, optimal and satisfactory gene transfer was obtained with the vein grafts subjected to the Ad method at 30 V, and transgene expression was seen primarily in adventitial fibroblasts. Gene transfer of endothelial nitric oxide synthase cDNA to the vein graft via the Ad method successfully limited the extent of intimal hyperplasia, even under hyperlipidemic conditions, at 4 wk after grafting. We thus propose that the Ad method via ex vivo electroporation may provide a novel, safe, and clinically available technique for nonviral gene transfer to sufficiently prevent late graft failure.

Recombinant Sendai virus vectors deleted in both the matrix and the fusion genes: efficient gene transfer with preferable properties

BACKGROUND

Sendai virus (SeV) is a new type of cytoplasmic RNA vector, which infects and replicates in most mammalian cells, directs high-level expression of the genes on its genome and is free from genotoxicity. In order to improve this vector, both the matrix (M) and fusion (F) genes were deleted from its genome.

METHODS

For the recovery of the M and F genes-deleted SeV (SeV/DeltaMDeltaF), the packaging cell line was established by using a Cre/loxP induction system. SeV/DeltaMDeltaF was characterized and compared with wild-type and F or M gene-deleted SeV vectors in terms of transduction ability, particle formation, transmissible property and cytotoxicity.

RESULTS

SeV/DeltaMDeltaF was propagated in high titers from the packaging cell line. When this vector was administered into the lateral ventricle and the respiratory tissue, many of the ependymal and epithelial cells were transduced, respectively, as in the case of wild-type SeV. F gene-deletion made the SeV vector non-transmissible, and M gene-deletion worked well to inhibit formation of the particles from infected cells. Simultaneous deletions of these two genes in the same genome resulted in combining both advantages. That is, both virus maturation into particles and transmissible property were almost completely abolished in cells infected with SeV/DeltaMDeltaF. Further, the cytopathic effect of SeV/DeltaMDeltaF was significantly attenuated rather than that of wild type in vitro and in vivo.

CONCLUSIONS

SeV/DeltaMDeltaF is an advanced type of cytoplasmic RNA vector, which retains efficient gene transfer, gains non-transmissible properties and loses particle formation with less cytopathic effect.

Efficient and stable Sendai virus-mediated gene transfer into primate embryonic stem cells with pluripotency preserved

Efficient gene transfer and regulated transgene expression in primate embryonic stem (ES) cells are highly desirable for future applications of the cells. In the present study, we have examined using the nonintegrating Sendai virus (SeV) vector to introduce the green fluorescent protein (GFP) gene into non-human primate cynomolgus ES cells. The GFP gene was vigorously and stably expressed in the cynomolgus ES cells for a year. The cells were able to form fluorescent teratomas when transplanted into immunodeficient mice. They were also able to differentiate into fluorescent embryoid bodies, neurons, and mature blood cells. In addition, the GFP expression levels were reduced dose-dependently by the addition of an anti-RNA virus drug, ribavirin, to the culture. Thus, SeV vector will be a useful tool for efficient gene transfer into primate ES cells and the method of using antiviral drugs should allow further investigation for regulated SeV-mediated gene expression.

Efficient propagation of single gene deleted recombinant Sendai virus vectors

Recombinant Sendai virus vectors (SeVV) have become an attractive tool for basic virological as well as for gene transfer studies. However, to (i) reduce the cellular injury induced by basic recombinant SeV vectors (encoding all six SeV genes as being present in SeV wild-type (wt) genomes) and to (ii) improve SeV vector safety, deletions of viral genes are necessary for the construction of superior SeVV generations. As a strong expression system recombinant replication-incompetent adenoviruses, coding for SeV proteins hemagglutinin-neuraminidase (HN), fusion (F), or matrix (M), were generated and successfully employed for the propagation of single gene deleted (DeltaHN, DeltaF, DeltaM) recombinant SeVV. Further investigations of the propagation procedures required for single gene deleted recombinant SeVV demonstrated (i) modifications of the cell culture medium composition as well as (ii) incubation with vitamin E as crucial steps for the enhancement of SeVV-DeltaHN, -DeltaF, or -DeltaM viral particle yield. Such optimized propagation procedures even led to a successful propagation of HN-deleted viral particles (SeVV-DeltaHN), which has not been reported before.

Essential role of PDGFRalpha-p70S6K signaling in mesenchymal cells during therapeutic and tumor angiogenesis in vivo: role of PDGFRalpha during angiogenesis

Discovery of the common and ubiquitous molecular targets for the disruption of angiogenesis, that are independent of the characteristics of malignant tumors, is desired to develop the more effective antitumor drugs. In this study, we propose that the platelet-derived growth factor receptor-alpha (PDGFRalpha)-p70S6K signal transduction pathway in mesenchymal cells, which is required for functional angiogenesis induced by fibroblast growth factor-2, is the potent candidate. Using murine limb ischemia as a tumor-free assay system, we demonstrated that p70S6K inhibitor rapamycin (RAPA) targets mesenchymal cells to shut down the sustained expression of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF), via silencing of the PDGFRalpha-p70S6K pathway. Irrespective of the varied expression profiles of angiogenic factors in each tumor tested, RAPA constantly led the tumors to dormancy and severe ischemia in the time course, even associated with upregulated expression of VEGF from tumors. Because RAPA showed only a minimal effect to hypoxia-related expression of VEGF in culture, these results suggest that RAPA targets the host-vasculature rather than tumor itself in vivo. Thus, our current study indicates that the PDGFRalpha-p70S6K pathway is an essential regulator for FGF-2-mediated therapeutic neovascularization, as well as for the host-derived vasculature but not tumors during tumor angiogenesis, via controlling continuity of expression of multiple angiogenic growth factors.

Reduced toxicity of F-deficient Sendai virus vector in the mouse fetus

Current concerns over insertional mutagenesis by retroviral vectors mitigate investigations into alternative, potentially persistent gene therapy vector systems not dependent on genomic integration, such as Sendai virus vectors (SeVV). Prenatal gene therapy requires efficient gene delivery to several tissues, which may not be achievable by somatic gene transfer to the adult. Initially, to test the potential and tropism of the SeVV for gene delivery to fetal tissues, first-generation (replication- and propagation-competent) recombinant SeVV, expressing beta-galactosidase was introduced into late gestation immunocompetent mice via the amniotic and peritoneal cavities and the yolk sac vessels. At 2 days, this resulted in very high levels of expression particularly in the airway epithelium, mesothelium and vascular endothelium, respectively. However, as expected, substantial vector toxicity was observed. The efficiency of gene transfer and the level of gene expression were then examined using a second-generation SeVV. The second generation was developed to be still capable of cytoplasmic RNA replication and therefore high-level gene expression, but incapable of vector spread due to lack of the gene for viral F-protein. Vector was introduced into the fetal amniotic and peritoneal cavities, intravascularly, intramuscularly and intraspinally; at 2 days, expression was observed in the airway epithelia, peritoneal mesothelia, unidentified cells in the gut wall, locally at the site of muscle injection and in the dorsal root ganglia, respectively. Mortality was dramatically diminished compared with the first-generation vector.

Recombinant Sendai virus vectors for activated T lymphocytes

T-lymphocyte-directed gene therapy has potential as a treatment of subjects with immunological disorders. One current limitation of this therapeutic strategy is low gene transfer efficiency, even when complex procedures are used. We report herein that a recombinant Sendai virus vector (SeV) was able to overcome this issue. Using jellyfish enhanced green fluorescent protein gene (EGFP), we found that SeV was able to transduce and express a foreign gene specifically and efficiently in activated murine and human T cells, but not in naive T cells, without centrifugation or reagents including polybrene and protamine sulfate; the present findings were in clear contrast to those demonstrated with the use of retroviruses. The transduction was selective in antigen-activated T cells, while antigen-irrelevant T cells were not transduced, even under bystander activation from specific T-cell responses by antigens ex vivo. Receptor saturation studies suggested a possible mechanism of activated T-cell-specific gene transfer, ie, SeV might attach to naive T cells but might be unable to enter their cytoplasm. We therefore propose that the SeV vector system may prove to be a potentially important alternative in the area of T-cell-directed gene therapy used in the clinical setting.

Sendai virus vectors as an emerging negative-strand RNA viral vector system

The power to manipulate the genome of negative-strand RNA viruses, including the insertion of additional non-viral genes, has led to the development of a new class of viral vectors for gene transfer approaches. The murine parainfluenza virus type I, or Sendai virus (SeV), has emerged as a prototype virus of this vector group, being employed in numerous in vitro as well as animal studies over the last few years. Extraordinary features of SeV are the remarkably brief contact time that is necessary for cellular uptake, a strong but adjustable expression of foreign genes, efficient infection in the respiratory tract despite a mucus layer, transduction of target cells being independent of the cell cycle, and an exclusively cytoplasmic replication cycle without any risk of chromosomal integration. In this review we describe the current knowledge of Sendai virus vector (SeVV) development as well as the results of first-generation vector applications under both in vitro and in vivo conditions. So far, Sendai virus vectors have been identified to be a highly efficient transduction tool for a broad range of different tissues and applications. Future directions in vector design and development are discussed.

Intramuscular gene transfer of FGF-2 attenuates endothelial dysfunction and inhibits intimal hyperplasia of vein grafts in poor-runoff limbs of rabbit

We previously demonstrated that sustained disturbance of endothelium-dependent vasorelaxation and poor distal runoff in ischemic limbs were critical factors affecting the neointimal development of autologous vein grafts (VGs). Also, we recently showed the superior therapeutic potential of basic fibroblast growth factor (bFGF/FGF-2) boosted by the recombinant Sendai virus (SeV) for severe limb ischemia compared with that of vascular endothelial growth factor. Here, the effect of FGF-2 on neointimal hyperplasia of VGs was examined in a rabbit model of poor-runoff limbs. Two weeks after initial surgery for the induction of poor-runoff, SeV-expressing human FGF-2 (SeV-hFGF2) or that encoding firefly luciferase (109 plaque-forming units/head) was injected into the thigh and calf muscle. At that time, the femoral vein was implanted in the femoral artery in an end-to-end manner in some groups. FGF-2 gene-transferred limbs demonstrated significantly increased blood flow assessed not only by laser Doppler flow image but also by ultrasonic transit-time flowmeter (USTF). USTF also showed a significant increase in the blood flow ratio of the deep femoral artery to external iliac artery, indicating that collateral flow was significantly restored in the thigh muscles (P < 0.01). Reduction of neointimal hyperplasia was also observed in the VGs treated by SeV-hFGF2; these grafts demonstrated significant restoration of endothelium-dependent vasorelaxation. These findings thus extend the indications of therapeutic angiogenesis using SeV-hFGF2 to include not only limb salvage but also prevention of late graft failure.

A new Sendai virus vector deficient in the matrix gene does not form virus particles and shows extensive cell-to-cell spreading

A new recombinant Sendai virus vector (SeV/DeltaM), in which the gene encoding matrix (M) protein was deleted, was recovered from cDNA and propagated in a packaging cell line expressing M protein by using a Cre/loxP induction system. The titer of SeV/DeltaM carrying the enhanced green fluorescent protein gene in place of the M gene was 7 x 10(7) cell infectious units/ml or more. The new vector showed high levels of infectivity and gene expression, similar to those of wild-type SeV vector, in vitro and in vivo. Virus maturation into a particle was almost completely abolished in cells infected with SeV/DeltaM. Instead, SeV/DeltaM infection brought about a significant increase of syncytium formation under conditions in which the fusion protein was proteolytically cleaved and activated by trypsin-like protease. This shows that SeV/DeltaM spreads markedly to neighboring cells in a cell-to-cell manner, because both hemagglutinin-neuraminidase and active fusion proteins are present at very high levels on the surface of cells infected with SeV/DeltaM. Thus, SeV/DeltaM is a novel type of vector with the characteristic features of loss of virus particle formation and gain of cell-to-cell spreading via a mechanism dependent on the activation of the fusion protein.

Nontransmissible virus-like particle formation by F-deficient sendai virus is temperature sensitive and reduced by mutations in M and HN proteins

The formation of nontransmissible virus-like particles (NTVLP) by cells infected with F-deficient Sendai virus (SeV/deltaF) was found to be temperature sensitive. Analysis by hemagglutination assays and Western blotting demonstrated that the formation of NTVLP at 38 degrees C was about 1/100 of that at 32 degrees C, whereas this temperature-sensitive difference was only moderate in the case of F-possessing wild-type SeV. In order to reduce the NTVLP formation with the aim of improving SeV for use as a vector for gene therapy, amino acid substitutions found in temperature-sensitive mutant SeVs were introduced into the M (G69E, T116A, and A183S) and HN (A262T, G264R, and K461G) proteins of SeV/deltaF to generate SeV/M(ts)HN(ts)deltaF. The use of these mutations allows vector production at low temperature (32 degrees C) and therapeutic use at body temperature (37 degrees C) with diminished NTVLP formation. As expected, the formation of NTVLP by SeV/M(ts)HN(ts)deltaF at 37 degrees C was decreased to about 1/10 of that by SeV/deltaF, whereas the suppression of NTVLP formation did not cause either enhanced cytotoxicity or reduced gene expression of the vector. The vectors showed differences with respect to the subcellular distribution of M protein in the infected cells. Clear and accumulated immunocytochemical signals of M protein on the cell surface were not observed in cells infected by SeV/deltaF at an incompatible temperature, 38 degrees C, or in those infected by SeV/M(ts)HN(ts)deltaF at 37 or 38 degrees C. The absence of F protein in SeV/deltaF and the additional mutations in M and HN in SeV/M(ts)HN(ts)deltaF probably weaken the ability to transport M protein to the plasma membrane, leading to the diminished formation of NTVLP.

Cell cycle independent infection and gene transfer by recombinant Sendai viruses

A common problem for viral vectors in the field of somatic gene therapy is the dependence of an efficient cellular transduction on the cell cycle phase of target cells. An optimized viral vector system should therefore transduce cells in different cell cycle phases equally to improve transduction efficiencies. Recent observations that recombinant Sendai viruses (SeV) can infect a broad range of different tissues suggested SeV to be a good candidate for future gene therapeutic strategies in which dividing and non-dividing cells have to be reached. However, detailed data on the influence of distinct cell cycle phases on the infection of SeV or related viruses are missing. We report that synchronization of NIH 3T3 cells as well as contact inhibition of human fibroblast cells did not exhibit any negative influence on SeV infection rates. Furthermore, different attractive target tissues like human umbilical cord derived cells or primary human hepatocytes can be reached by SeV efficiently. As an important information for further cell cycle studies of paramyxoviruses we discovered surprisingly that the DNA polymerase inhibitor aphidicolin (induces a G(1)/M arrest) functions as an inhibitor of SeV but not of an adenoviral expression vector. In conclusion, the results demonstrate SeV based vector particles to be an ideal tool to reach equally cells coexisting in different cell cycle phases.