Comparison between Sendai virus and adenovirus vectors to transduce HIV-1 genes into human dendritic cells

Transition from Animal-Based to Human Induced Pluripotent Stem Cells (iPSCs)-Based Models of Neurodevelopmental Disorders: Opportunities and Challenges

Neurodevelopmental disorders (NDDs) arise from the disruption of highly coordinated mechanisms underlying brain development, which results in impaired sensory, motor and/or cognitive functions. Although rodent models have offered very relevant insights to the field, the translation of findings to clinics, particularly regarding therapeutic approaches for these diseases, remains challenging. Part of the explanation for this failure may be the genetic differences-some targets not being conserved between species-and, most importantly, the differences in regulation of gene expression. This prompts the use of human-derived models to study NDDS. The generation of human induced pluripotent stem cells (hIPSCs) added a new suitable alternative to overcome species limitations, allowing for the study of human neuronal development while maintaining the genetic background of the donor patient. Several hIPSC models of NDDs already proved their worth by mimicking several pathological phenotypes found in humans. In this review, we highlight the utility of hIPSCs to pave new paths for NDD research and development of new therapeutic tools, summarize the challenges and advances of hIPSC-culture and neuronal differentiation protocols and discuss the best way to take advantage of these models, illustrating this with examples of success for some NDDs.

MSCs vs. iPSCs: Potential in therapeutic applications

Over the past 2 decades, mesenchymal stem cells (MSCs) have attracted a lot of interest as a unique therapeutic approach for a variety of diseases. MSCs are capable of self-renewal and multilineage differentiation capacity, immunomodulatory, and anti-inflammatory properties allowing it to play a role in regenerative medicine. Furthermore, MSCs are low in tumorigenicity and immune privileged, which permits the use of allogeneic MSCs for therapies that eliminate the need to collect MSCs directly from patients. Induced pluripotent stem cells (iPSCs) can be generated from adult cells through gene reprogramming with ectopic expression of specific pluripotency factors. Advancement in iPS technology avoids the destruction of embryos to make pluripotent cells, making it free of ethical concerns. iPSCs can self-renew and develop into a plethora of specialized cells making it a useful resource for regenerative medicine as they may be created from any human source. MSCs have also been used to treat individuals infected with the SARS-CoV-2 virus. MSCs have undergone more clinical trials than iPSCs due to high tumorigenicity, which can trigger oncogenic transformation. In this review, we discussed the overview of mesenchymal stem cells and induced pluripotent stem cells. We briefly present therapeutic approaches and COVID-19-related diseases using MSCs and iPSCs.

An Insight into DNA-free Reprogramming Approaches to Generate Integration-free Induced Pluripotent Stem Cells for Prospective Biomedical Applications

More than a decade ago, a pioneering study reported generation of induced Pluripotent Stem Cells (iPSCs) by ectopic expression of a cocktail of reprogramming factors in fibroblasts. This study has revolutionized stem cell research and has garnered immense interest from the scientific community globally. iPSCs hold tremendous potential for understanding human developmental biology, disease modeling, drug screening and discovery, and personalized cell-based therapeutic applications. The seminal study identified Oct4, Sox2, Klf4 and c-Myc as a potent combination of genes to induce reprogramming. Subsequently, various reprogramming factors were identified by numerous groups. Most of these studies have used integrating viral vectors to overexpress reprogramming factors in somatic cells to derive iPSCs. However, these techniques restrict the clinical applicability of these cells as they may alter the genome due to random viral integration resulting in insertional mutagenesis and tumorigenicity. To circumvent this issue, alternative integration-free reprogramming approaches are continuously developed that eliminate the risk of genomic modifications and improve the prospects of iPSCs from lab to clinic. These methods establish that integration of transgenes into the genome is not essential to induce pluripotency in somatic cells. This review provides a comprehensive overview of the most promising DNA-free reprogramming techniques that have the potential to derive integration-free iPSCs without genomic manipulation, such as sendai virus, recombinant proteins, microRNAs, synthetic messenger RNA and small molecules. The understanding of these approaches shall pave a way for the generation of clinical-grade iPSCs. Subsequently, these iPSCs can be differentiated into desired cell type(s) for various biomedical applications.

An insight into non-integrative gene delivery approaches to generate transgene-free induced pluripotent stem cells

Over a decade ago, a landmark study that reported derivation of induced Pluripotent Stem Cells (iPSCs) by reprogramming fibroblasts has transformed stem cell research attracting the interest of the scientific community worldwide. These cells circumvent the ethical and immunological concerns associated with embryonic stem cells, and the limited self-renewal ability and restricted differentiation potential linked to adult stem cells. iPSCs hold great potential for understanding basic human biology, in vitro disease modeling, high-throughput drug testing and discovery, and personalized regenerative medicine. The conventional reprogramming methods involving retro- and lenti-viral vectors to deliver reprogramming factors in somatic cells to generate iPSCs nullify the clinical applicability of these cells. Although these gene delivery systems are efficient and robust, they carry an enormous risk of permanent genetic modifications and are potentially tumorigenic. To evade these safety concerns and derive iPSCs for human therapy, tremendous technological advancements have resulted in the development of non-integrating viral- and non-viral approaches. These gene delivery techniques curtail or eliminate the risk of any genomic alteration and enhance the prospects of iPSCs from bench-to-bedside. The present review provides a comprehensive overview of non-integrating viral (adenoviral vectors, adeno-associated viral vectors, and Sendai virus vectors) and DNA-based, non-viral (plasmid transfection, minicircle vectors, transposon vectors, episomal vectors, and liposomal magnetofection) approaches that have the potential to generate transgene-free iPSCs. The understanding of these techniques could pave the way for the use of iPSCs for various biomedical applications.

Efficient Delivery of Human Cytomegalovirus T Cell Antigens by Attenuated Sendai Virus Vectors

Human cytomegalovirus (HCMV) represents a major cause of clinical complications during pregnancy as well as immunosuppression, and the licensing of a protective HCMV vaccine remains an unmet global need. Here, we designed and validated novel Sendai virus (SeV) vectors delivering the T cell immunogens IE-1 and pp65. To enhance vector safety, we used a replication-deficient strain (rdSeV) that infects target cells in a nonproductive manner while retaining viral gene expression. In this study, we explored the impact that transduction with rdSeV has on human dendritic cells (DCs) by comparing it to the parental, replication-competent Sendai virus strain (rcSeV) as well as the poxvirus strain modified vaccinia Ankara (MVA). We found that wild-type SeV is capable of replicating to high titers in DCs while rdSeV infects cells abortively. Due to the higher degree of attenuation, IE-1 and pp65 protein levels mediated by rdSeV after infection of DCs were markedly reduced compared to those of the parental Sendai virus recombinants, but antigen-specific restimulation of T cell clones was not negatively affected by this. Importantly, rdSeV showed reduced cytotoxic effects compared to rcSeV and MVA and was capable of mediating DC maturation as well as secretion of alpha interferon and interleukin-6. Finally, in a challenge model with a murine cytomegalovirus (MCMV) strain carrying an HCMV pp65 peptide, we found that viral replication was restricted if mice were previously vaccinated with rdSeV-pp65. Taken together, these data demonstrate that rdSeV has great potential as a vector system for the delivery of HCMV immunogens.IMPORTANCE HCMV is a highly prevalent betaherpesvirus that establishes lifelong latency after primary infection. Congenital HCMV infection is the most common viral complication in newborns, causing a number of late sequelae ranging from impaired hearing to mental retardation. At the same time, managing HCMV reactivation during immunosuppression remains a major hurdle in posttransplant care. Since options for the treatment of HCMV infection are still limited, the development of a vaccine to confine HCMV-related morbidities is urgently needed. We generated new vaccine candidates in which the main targets of T cell immunity during natural HCMV infection, IE-1 and pp65, are delivered by a replication-deficient, Sendai virus-based vector system. In addition to classical prophylactic vaccine concepts, these vectors could also be used for therapeutic applications, thereby expanding preexisting immunity in high-risk groups such as transplant recipients or for immunotherapy of glioblastomas expressing HCMV antigens.

Gene transfer in inner ear cells: a challenging race

Recent advances in human genomics led to the identification of numerous defective genes causing deafness, which represent novel putative therapeutic targets. Future gene-based treatment of deafness resulting from genetic or acquired sensorineural hearing loss may include strategies ranging from gene therapy to antisense delivery. For successful development of gene therapies, a minimal requirement involves the engineering of appropriate gene carrier systems. Transfer of exogenous genetic material into the mammalian inner ear using viral or non-viral vectors has been characterized over the last decade. The nature of inner ear cells targeted, as well as the transgene expression level and duration, are highly dependent on the vector type, the route of administration and the strength of the promoter driving expression. This review summarizes and discusses recent advances in inner ear gene-transfer technologies aimed at examining gene function or identifying new treatment for inner ear disorders.

Emerging applications of lentiviral vectors in dendritic cell-based immunotherapy

Dendritic cells are professional antigen-presenting cells that initiate, regulate and shape the induction of specific immune responses. The ability to use dendritic cells in the induction of antigen-specific tolerance, antigen-specific immunity or specific differentiation of T-helper subsets holds great promise in dendritic cell-based immunotherapy of various diseases such as cancer, viral infections, allergy, as well as autoimmunity. Replication-incompetent HIV-1-based lentiviral vector is now emerging as a promising delivery system to genetically modify dendritic cells through antigen recognition, costimulatory molecules and/or polarization signals for the manipulation of antigen-specific immunity in vivo. This article discusses some of the recent advances in the uses of lentiviral vectors in dendritic cell-based immunotherapy.

Lung homing CTLs and their proliferation ability are important correlates of vaccine protection against influenza

We conducted a study to evaluate the protective efficacy in mice of vaccination with novel adenovirus vectors expressing an influenza A nucleoprotein (AdFluA-NP) based on isolates from non-human primates. In a previous study, we had observed that AdFluA-NP vectors can induce similar T cell responses in mice yet differ in ability to protect animals from lethal challenge with influenza A virus. To better define correlates of protection, we extended our study design to include additional novel AdFluA-NP vectors, and to evaluate cytotoxic T lymphocyte (CTL) responses in the spleens and lungs of immunized mice prior to virus challenge. As in our previous study, all vectors induced similar numbers of antigen-specific interferon gamma (IFNgamma) secreting T cells and memory T cells in the spleen 4 weeks post immunization, but differed in their ability to protect the animals from lethal infection. However, cytokine-secreting NP antigen-specific CTLs in the lungs of mice from immunization groups that survived lethal challenge showed greater proliferative ability and higher CD27 expression. In addition, NP antigen-specific peripheral blood lymphocytes from protected mice showed greater proliferative ability after ex vivo stimulation. Our results provide additional correlates of protection that should be considered when developing anti-influenza vaccines.