Engineering HSV-1 vectors for gene therapy

Disease-modifying rdHSV-CA8* non-opioid analgesic gene therapy treats chronic osteoarthritis pain by activating Kv7 voltage-gated potassium channels

Chronic pain is common in our population, and most of these patients are inadequately treated, making the development of safer analgesics a high priority. Knee osteoarthritis (OA) is a primary cause of chronic pain and disability worldwide, and lower extremity OA is a major contributor to loss of quality-adjusted life-years. In this study we tested the hypothesis that a novel JDNI8 replication-defective herpes simplex-1 viral vector (rdHSV) incorporating a modified carbonic anhydrase-8 transgene (CA8*) produces analgesia and treats monoiodoacetate-induced (MIA) chronic knee pain due to OA. We observed transduction of lumbar DRG sensory neurons with these viral constructs (vHCA8*) (~40% of advillin-positive cells and ~ 50% of TrkA-positive cells colocalized with V5-positive cells) using the intra-articular (IA) knee joint (KJ) route of administration. vHCA8* inhibited chronic mechanical OA knee pain induced by MIA was dose- and time-dependent. Mechanical thresholds returned to Baseline by D17 after IA KJ vHCA8* treatment, and exceeded Baseline (analgesia) through D65, whereas negative controls failed to reach Baseline responses. Weight-bearing and automated voluntary wheel running were improved by vHCA8*, but not negative controls. Kv7 voltage-gated potassium channel-specific inhibitor XE-991 reversed vHCA8*-induced analgesia. Using IHC, IA KJ of vHCA8* activated DRG Kv7 channels via dephosphorylation, but negative controls failed to impact Kv7 channels. XE-991 stimulated Kv7.2-7.5 and Kv7.3 phosphorylation using western blotting of differentiated SH-SY5Y cells, which was inhibited by vHCA8* but not by negative controls. The observed prolonged dose-dependent therapeutic effects of IA KJ administration of vHCA8* on MIA-induced chronic KJ pain due to OA is consistent with the specific activation of Kv7 channels in small DRG sensory neurons. Together, these data demonstrate for the first-time local IA KJ administration of vHCA8* produces opioid-independent analgesia in this MIA-induced OA chronic pain model, supporting further therapeutic development.

rdHSV-CA8 non-opioid analgesic gene therapy decreases somatosensory neuronal excitability by activating Kv7 voltage-gated potassium channels

Chronic pain is common and inadequately treated, making the development of safe and effective analgesics a high priority. Our previous data indicate that carbonic anhydrase-8 (CA8) expression in dorsal root ganglia (DRG) mediates analgesia via inhibition of neuronal ER inositol trisphosphate receptor-1 (ITPR1) via subsequent decrease in ER calcium release and reduction of cytoplasmic free calcium, essential to the regulation of neuronal excitability. This study tested the hypothesis that novel JDNI8 replication-defective herpes simplex-1 viral vectors (rdHSV) carrying a CA8 transgene (vHCA8) reduce primary afferent neuronal excitability. Whole-cell current clamp recordings in small DRG neurons showed that vHCA8 transduction caused prolongation of their afterhyperpolarization (AHP), an essential regulator of neuronal excitability. This AHP prolongation was completely reversed by the specific Kv7 channel inhibitor XE-991. Voltage clamp recordings indicate an effect via Kv7 channels in vHCA8-infected small DRG neurons. These data demonstrate for the first time that vHCA8 produces Kv7 channel activation, which decreases neuronal excitability in nociceptors. This suppression of excitability may translate in vivo as non-opioid dependent behavioral- or clinical analgesia, if proven behaviorally and clinically.

Macrophage's role in solid tumors: two edges of a sword

The tumor microenvironment is overwhelmingly dictated by macrophages, intimately affiliated with tumors, exercising pivotal roles in multiple processes, including angiogenesis, extracellular matrix reconfiguration, cellular proliferation, metastasis, and immunosuppression. They further exhibit resilience to chemotherapy and immunotherapy via meticulous checkpoint blockades. When appropriately stimulated, macrophages can morph into a potent bidirectional component of the immune system, engulfing malignant cells and annihilating them with cytotoxic substances, thus rendering them intriguing candidates for therapeutic targets. As myelomonocytic cells relentlessly amass within tumor tissues, macrophages rise as prime contenders for cell therapy upon the development of chimeric antigen receptor effector cells. Given the significant incidence of macrophage infiltration correlated with an unfavorable prognosis and heightened resistance to chemotherapy in solid tumors, we delve into the intricate role of macrophages in cancer propagation and their promising potential in confronting four formidable cancer variants-namely, melanoma, colon, glioma, and breast cancers.

Evaluation of parameters for efficient purification and long-term storage of herpes simplex virus-based vectors

Replication competent oncolytic herpes simplex virus (HSV) vectors have been used extensively to treat solid tumors with promising results. However, highly defective HSV vectors will be needed for applications that require sustained therapeutic gene expression in the absence of vector-related toxicity or inflammation. These vectors require complementing cell lines for their manufacture, creating significant challenges to achieve high yields of infectious virus particles. We recently described an improved upstream process for the production of a non-cytotoxic HSV vector for gene therapy applications. Here, we sought to optimize the downstream conditions for purification and long-term storage of the same vector, JΔNI5. We compared different methods to remove cellular impurities and concentrate the vector by monitoring both physical and biological titers, resulting in the establishment of optimal conditions for vector production. To optimize the long-term storage parameters for non-cytotoxic HSV vectors, we evaluated vector stability at low temperature and sensitivity to freeze-thaw cycles. We report that suboptimal purification and storage methods resulted in loss of vector viability. Our results describe effective and reproducible protocols for purification and storage of HSV vectors for pre-clinical studies.

Oncolytic Virus Therapy Alters the Secretome of Targeted Glioblastoma Cells

Simple Summary

Proteins secreted by cancer cells in response to oncolytic virus anti-tumor therapy constitute the instructions for the immune cells. Yet as there are hundreds of proteins, including those encapsulated in vesicles, whose message drives the mobilization of immune cells, we aimed to decipher the instruction sent by cancer cells in response to therapy. Searching the cataloged vesicle and vesicle-free secreted proteins, we found that the proteins associated with the favorable survival of brain cancer patients were those that have the power to mobilize the immune cells. Thus, this approach established cancer-secreted contributors to the immune–therapeutic effect of the oncolytic virus.

Abstract

Oncolytic virus (OV) therapy, which is being tested in clinical trials for glioblastoma, targets cancer cells, while triggering immune cells. Yet OV sensitivity varies from patient to patient. As OV therapy is regarded as an anti-tumor vaccine, by making OV-infected cancer cells secrete immunogenic proteins, linking these proteins to transcriptome would provide a measuring tool to predict their sensitivity. A set of six patient-derived glioblastoma cells treated ex-vivo with herpes simplex virus type 1 (HSV1) modeled a clinical setting of OV infection. The cellular transcriptome and secreted proteome (separated into extracellular vesicles (EV) and EV-depleted fractions) were analyzed by gene microarray and mass-spectroscopy, respectively. Data validation and in silico analysis measured and correlated the secretome content with the response to infection and patient survival. Glioblastoma cells reacted to the OV infection in a seemingly dissimilar fashion, but their transcriptomes changed in the same direction. Therefore, the upregulation of transcripts encoding for secreted proteins implies a common thread in the response of cancer cells to infection. Indeed, the OV-driven secretome is linked to the immune response. While these proteins have distinct membership in either EV or EV-depleted fractions, it is their co-secretion that augments the immune response and associates with favorable patient outcomes.

Gold Nanoparticle-Assisted Virus Formation by Means of the Delivery of an Oncolytic Adenovirus Genome

Oncolytic adenoviruses are a therapeutic alternative to treat cancer based on their ability to replicate selectively in tumor cells. However, their use is limited mainly by the neutralizing antibody (Nab) immune response that prevents repeated dosing. An alternative to facilitate the DNA access to the tumor even in the presence of anti-viral Nabs could be gold nanoparticles able to transfer DNA molecules. However, the ability of these nanoparticles to carry large DNA molecules, such as an oncolytic adenovirus genome, has not been studied. In this work, gold nanoparticles were functionalized with different amounts of polyethylenimine to transfer in a safe and efficient manner a large oncolytic virus genome. Their transfer efficacy and final effect of the oncolytic virus in cancer cells are studied. For each synthesized nanoparticle, (a) DNA loading capacity, (b) complex size, (c) DNA protection ability, (d) transfection efficacy and (e) cytotoxic effect were studied. We observed that small gold nanoparticles (70–80 nm in diameter) protected DNA against nucleases and were able to transfect the ICOVIR-15 oncolytic virus genome encoded in pLR1 plasmid. In the present work, efficient transgene RNA expression, luciferase activity and viral cytopathic effect on cancer cells are reported. These results suggest gold nanoparticles to be an efficient and safe vector for oncolytic adenovirus genome transfer.

Viral Vector Systems for Gene Therapy: A Comprehensive Literature Review of Progress and Biosafety Challenges

INTRODUCTION

National Institutes of Health (NIH) defines gene therapy as an experimental technique that uses genes to treat or prevent disease. Although gene therapy is a promising treatment option for a number of diseases (including inherited disorders, some types of cancer, and certain viral infections), the technique remains risky and is still under study to make sure that it will be effective and safe.

METHODS

Applications of viral vectors and nonviral gene delivery systems have found an encouraging new beginning in gene therapy in recent years. Although several viral vectors and nonviral gene delivery systems have been developed in the past 3 decades, no one delivery system can be applied in gene therapy to all cell types in vitro and in vivo. Furthermore, the use of viral vector systems (both in vitro and in vivo) present unique occupational health and safety challenges. In this review article, we discuss the biosafety challenges and the current framework of risk assessment for working with the viral vector systems.

DISCUSSION

The recent advances in the field of gene therapy is exciting, but it is important for scientists, institutional biosafety committees, and biosafety officers to safeguard public trust in the use of this technology in clinical trials and make conscious efforts to engage the public through ongoing forums and discussions.

RAD52: Viral Friend or Foe?

Mammalian Radiation Sensitive 52 (RAD52) is a gene whose scientific reputation has recently seen a strong resurgence. In the past decade, RAD52, which was thought to be dispensable for most DNA repair and recombination reactions in mammals, has been shown to be important for a bevy of DNA metabolic pathways. One of these processes is termed break-induced replication (BIR), a mechanism that can be used to re-start broken replication forks and to elongate the ends of chromosomes in telomerase-negative cells. Viruses have historically evolved a myriad of mechanisms in which they either conscript cellular factors or, more frequently, inactivate them as a means to enable their own replication and survival. Recent data suggests that Adeno-Associated Virus (AAV) may replicate its DNA in a BIR-like fashion and/or utilize RAD52 to facilitate viral transduction and, as such, likely conscripts/requires the host RAD52 protein to promote its perpetuation.

Viral approaches to study the mammalian brain: Lineage tracing, circuit dissection and therapeutic applications

Viral vectors are widely used to study the development, function and pathology of neural circuits in the mammalian brain. Their flexible payloads with customizable choices of tool genes allow versatile applications ranging from lineage tracing, circuit mapping and functional interrogation, to translational and therapeutic applications. Different applications have distinct technological requirements, therefore, often utilize different types of virus. This review introduces the most commonly used viruses for these applications and some recent advances in improving the resolution and throughput of lineage tracing, the efficacy and selectivity of circuit tracing and the specificity of cell type targeting.

High-brightness anterograde transneuronal HSV1 H129 tracer modified using a Trojan horse-like strategy

Neurotropic viral transsynaptic tracing is an increasingly powerful technique for dissecting the structure and function of neural circuits. Herpes simplex virus type 1 strain H129 has been widely used as an anterograde tracer. However, HSV tracers still have several shortcomings, including high toxicity, low sensitivity and non-specific retrograde labeling. Here, we aimed to construct high-brightness HSV anterograde tracers by increasing the expression of exogenous genes carried by H129 viruses. Using a Trojan horse-like strategy, a HSV/AAV (adeno-associated virus) chimaera termed H8 was generated to enhance the expression of a fluorescent marker. In vitro and in vivo assays showed that the exogenous gene was efficiently replicated and amplified by the synergism of the HSV vector and introduced AAV replication system. H8 reporting fluorescence was brighter than that of currently available H129 tracers, and H8 could be used for fast and effective anterograde tracing without additional immunostaining. These results indicated that foreign gene expression in HSV tracers could be enhanced by integrating HSV with AAV replication system. This approach may be useful as a general enhanced expression strategy for HSV-based tracing tools or gene delivery vectors.

Repurposing the yellow fever vaccine for intratumoral immunotherapy

Live 17D is widely used as a prophylactic vaccine strain for yellow fever virus that induces potent neutralizing humoral and cellular immunity against the wild-type pathogen. 17D replicates and kills mouse and human tumor cell lines but not non-transformed human cells. Intratumoral injections with viable 17D markedly delay transplanted tumor progression in a CD8 T-cell-dependent manner. In mice bearing bilateral tumors in which only one is intratumorally injected, contralateral therapeutic effects are observed consistent with more prominent CD8 T-cell infiltrates and a treatment-related reduction of Tregs. Additive efficacy effects were observed upon co-treatment with intratumoral 17D and systemic anti-CD137 and anti-PD-1 immunostimulatory monoclonal antibodies. Importantly, when mice were preimmunized with 17D, intratumoral 17D treatment achieved better local and distant antitumor immunity. Such beneficial effects of prevaccination are in part explained by the potentiation of CD4 and CD8 T-cell infiltration in the treated tumor. The repurposed use of a GMP-grade vaccine to be given via the intratumoral route in prevaccinated patients constitutes a clinically feasible and safe immunotherapy approach.

The rapidly evolving state of gene therapy

Gene therapy is emerging as a viable option for clinical therapy of monogenic disorders and other genetically defined diseases, with approved gene therapies available in Europe and newly approved gene therapies in the United States. In the past 10 years, gene therapy has moved from a distant possibility, even in the minds of much of the scientific community, to being widely realized as a valuable therapeutic tool with wide-ranging potential. The U.S. Food and Drug Administration has recently approved Luxturna (Spark Therapeutics Inc, Philadelphia, PA, USA), a recombinant adeno-associated virus (rAAV) 2 gene therapy for one type of Leber congenital amaurosis 2 ( 1 , 2 ). The European Medicines Agency (EMA) has approved 3 recombinant viral vector products: Glybera (UniQure, Amsterdam, The Netherlands), an rAAV vector for lipoprotein lipase deficiency; Strimvelis (Glaxo Smith-Kline, Brentford, United Kingdom), an ex vivo gammaretrovirus-based therapy for patients with adenosine deaminase-deficient severe combined immune deficiency (ADA-SCID); and Kymriah (Novartis, Basel, Switzerland), an ex vivo lentivirus-based therapy to engineer autologous chimeric antigen-receptor T (CAR-T) cells targeting CD19-positive cells in acute lymphoblastic leukemia. These examples will be followed by the clinical approval of other gene therapy products as this field matures. In this review we provide an overview of the state of gene therapy by discussing where the field stands with respect to the different gene therapy vector platforms and the types of therapies that are available.-Gruntman, A. M., Flotte, T. R. The rapidly evolving state of gene therapy.

Gene Therapy Leaves a Vicious Cycle

The human genetic code encrypted in thousands of genes holds the secret for synthesis of proteins that drive all biological processes necessary for normal life and death. Though the genetic ciphering remains unchanged through generations, some genes get disrupted, deleted and or mutated, manifesting diseases, and or disorders. Current treatment options—chemotherapy, protein therapy, radiotherapy, and surgery available for no more than 500 diseases—neither cure nor prevent genetic errors but often cause many side effects. However, gene therapy, colloquially called “living drug,” provides a one-time treatment option by rewriting or fixing errors in the natural genetic ciphering. Since gene therapy is predominantly a viral vector-based medicine, it has met with a fair bit of skepticism from both the science fraternity and patients. Now, thanks to advancements in gene editing and recombinant viral vector development, the interest of clinicians and pharmaceutical industries has been rekindled. With the advent of more than 12 different gene therapy drugs for curing cancer, blindness, immune, and neuronal disorders, this emerging experimental medicine has yet again come in the limelight. The present review article delves into the popular viral vectors used in gene therapy, advances, challenges, and perspectives.

Photobiomodulation promotes adenoviral gene transduction in auditory cells

Gene therapy is the delivery of a therapeutic gene into target cells to treat disorders by replacing disease-causing mutated genes with healthy ones. Gene therapy of the inner ear has been recently described, with applications for sensorineural hearing loss. However, gene delivery to the location of the inner ear, and thus efficacy of therapy, is challenging. Photobiomodulation (PBM) with a low-level laser has been suggested to have a therapeutic effect and has the potential to augment gene therapy. To investigate whether PBM improves the rate of adenovirus (Ad)-mediated viral delivery, we compared low-level laser therapy (LLLT) and non-LLLT HEI-OC1 cells treated with an Ad viral vector carrying green fluorescent protein (GFP). Cultured HEI-OC1 cells were divided into six groups: no treatment control, LLLT only, 1 μL Ad-GFP, 3 μL Ad-GFP, 1 μL Ad-GFP + LLLT, and 3 μL Ad-GFP + LLLT (LLLT: 808 nm at 15 mW for 15 min). Cells were irradiated twice: at 2 h and again at 24 h. A nonparametric Mann-Whitney U test was used to statistically analyze differences between the control and treatment groups. The viral inoculations used in this study did not change the amount of viable HEI-OC1 cells (N = 4-8). The 1 μL Ad-GFP + LLLT and 3 μL Ad-GFP + LLLT groups showed an increased density of GFP-positive cells compared to 1 μL and 3 μL Ad-GFP cells (N = 5-8, 1 μL: p = 0.0159; 3 μL: p = 0.0168,). The quantitative analysis of the epifluorescence of the 1 μL Ad-GFP + LLLT, and 3 μL Ad-GFP + LLLT groups revealed increased GFP expression/cell compared to 1 μL and 3 μL Ad-GFP cells (N = 6-15, 1 μL: p = 0.0082; 3 μL: p = 0.0012). The RT-qPCR results were consistent (N = 4-5, p = 0.0159). These findings suggest that PBM may enhance the gene delivery of Ad-mediated viral transduction, and the combination of the two may be a promising tool for gene therapy for sensorineural hearing loss.

Effects of herpes simplex virus vectors encoding poreless TRPV1 or protein phosphatase 1α in a rat cystitis model induced by hydrogen peroxide

Enhanced afferent excitability is considered to be an important pathophysiological basis of interstitial cystitis/bladder pain syndrome (IC/BPS). In addition, transient receptor potential vanilloid-1 (TRPV1) receptors are known to be involved in afferent sensitization. Animals with hydrogen peroxide (HP)-induced cystitis have been used as a model exhibiting pathologic characteristics of chronic inflammatory condition of the bladder. This study investigated the effect of gene therapy with replication-defective herpes simplex virus (HSV) vectors encoding poreless TRPV1 (PL) or protein phosphatase 1 α (PP1α), a negative regulator of TRPV1, using a HP-induced rat model of cystitis. HSV vectors encoding green fluorescent protein, PL or PP1α were inoculated into the bladder wall of female rats. After 1 week, 1% HP or normal saline was administered into the bladder, and the evaluations were performed 2 weeks after viral inoculation. In HP-induced cystitis rats, gene delivery of PL or PP1α decreased pain behavior as well as a reduction in the intercontraction interval. Also, both treatments reduced nerve growth factor expression in the bladder mucosa, reduced bladder inflammation characterized by infiltration of inflammatory cells and increased bladder weight. Taken together, HSV-mediated gene therapy targeting TRPV1 receptors could be effective for the treatment of IC/BPS.

Morphological changes in different populations of bladder afferent neurons detected by herpes simplex virus (HSV) vectors with cell-type-specific promoters in mice with spinal cord injury

Functional and morphological changes in C-fiber bladder afferent pathways are reportedly involved in neurogenic detrusor overactivity (NDO) after spinal cord injury (SCI). This study examined the morphological changes in different populations of bladder afferent neurons after SCI using replication-defective herpes simplex virus (HSV) vectors encoding the mCherry reporter driven by neuronal cell-type-specific promoters. Spinal intact (SI) and SCI mice were injected into the bladder wall with HSV mCherry vectors driven by the cytomegalovirus (CMV) promoter, CGRP promoter, TRPV1 promoter or neurofilament 200 (NF200) promoter. Two weeks after vector inoculation into the bladder wall, L1 and L6 dorsal root ganglia (DRG) were removed bilaterally for immunofluorescent staining using anti-mCherry antibody. The number of CMV promoter vector-labeled neurons was not altered after SCI. The number of CGRP and TRPV1 promoter vector-labeled neurons was significantly increased whereas the number of NF200 vector-labeled neurons was decreased in L6 DRG after SCI. The median size of CGRP promoter-labeled C-fiber neurons was increased from 247.0 in SI mice to 271.3μm² in SCI mice whereas the median cell size of TRPV1 promoter vector-labeled neurons was decreased from 245.2 in SI mice to 216.5μm² in SCI mice. CGRP and TRPV1 mRNA levels of laser-captured bladder afferent neurons labeled with Fast Blue were significantly increased in SCI mice compared to SI mice. Thus, using a novel HSV vector-mediated neuronal labeling technique, we found that SCI induces expansion of the CGRP- and TRPV1-expressing C-fiber cell population, which could contribute to C-fiber afferent hyperexcitability and NDO after SCI.

Intratumoral Delivery of Immunotherapy-Act Locally, Think Globally

Immune mechanisms have evolved to cope with local entry of microbes acting in a confined fashion but eventually inducing systemic immune memory. Indeed, in situ delivery of a number of agents into tumors can mimic in the malignant tissue the phenomena that control intracellular infection leading to the killing of infected cells. Vascular endothelium activation and lymphocyte attraction, together with dendritic cell-mediated cross-priming, are the key elements. Intratumoral therapy with pathogen-associated molecular patterns or recombinant viruses is being tested in the clinic. Cell therapies can be also delivered intratumorally, including infusion of autologous dendritic cells and even tumor-reactive T lymphocytes. Intralesional virotherapy with an HSV vector expressing GM-CSF has been recently approved by the Food and Drug Administration for the treatment of unresectable melanoma. Immunomodulatory monoclonal Abs have also been successfully applied intratumorally in animal models. Local delivery means less systemic toxicity while focusing the immune response on the malignancy and the affected draining lymph nodes.

Oncolytic Herpes Virus rRp450 Shows Efficacy in Orthotopic Xenograft Group 3/4 Medulloblastomas and Atypical Teratoid/Rhabdoid Tumors

Pediatric brain tumors including medulloblastoma and atypical teratoid/rhabdoid tumor are associated with significant mortality and treatment-associated morbidity. While medulloblastoma tumors within molecular subgroups 3 and 4 have a propensity to metastasize, atypical teratoid/rhabdoid tumors frequently afflict a very young patient population. Adjuvant treatment options for children suffering with these tumors are not only sub-optimal but also associated with many neurocognitive obstacles. A potentially novel treatment approach is oncolytic virotherapy, a developing therapeutic platform currently in early-phase clinical trials for pediatric brain tumors and recently US Food and Drug Administration (FDA)-approved to treat melanoma in adults. We evaluated the therapeutic potential of the clinically available oncolytic herpes simplex vector rRp450 in cell lines derived from medulloblastoma and atypical teratoid/rhabdoid tumor. Cells of both tumor types were supportive of virus replication and virus-mediated cytotoxicity. Orthotopic xenograft models of medulloblastoma and atypical teratoid/rhabdoid tumors displayed significantly prolonged survival following a single, stereotactic intratumoral injection of rRp450. Furthermore, addition of the chemotherapeutic prodrug cyclophosphamide (CPA) enhanced rRp450's in vivo efficacy. In conclusion, oncolytic herpes viruses with the ability to bioactivate the prodrug CPA within the tumor microenvironment warrant further investigation as a potential therapy for pediatric brain tumors.

Gene transfer to the outflow tract

Elevated intraocular pressure is the primary cause of open angle glaucoma. Outflow resistance exists within the trabecular meshwork but also at the level of Schlemm's canal and further downstream within the outflow system. Viral vectors allow to take advantage of naturally evolved, highly efficient mechanisms of gene transfer, a process that is termed transduction. They can be produced at biosafety level 2 in the lab using protocols that have evolved considerably over the last 15-20 years. Applied by an intracameral bolus, vectors follow conventional as well as uveoscleral outflow pathways. They may affect other structures in the anterior chamber depending on their transduction kinetics which can vary among species when using the same vector. Not all vectors can express long-term, a desirable feature to address the chronicity of glaucoma. Vectors that integrate into the genome of the target cell can achieve transgene function for the life of the transduced cell but are mutagenic by definition. The most prominent long-term expressing vector systems are based on lentiviruses that are derived from HIV, FIV, or EIAV. Safety considerations make non-primate lentiviral vector systems easier to work with as they are not derived from human pathogens. Non-integrating vectors are subject to degradation and attritional dilution during cell division. Lentiviral vectors have to integrate in order to express while adeno-associated viral vectors (AAV) often persist as intracellular concatemers but may also integrate. Adeno- and herpes viral vectors do not integrate and earlier generation systems might be relatively immunogenic. Nonviral methods of gene transfer are termed transfection with few restrictions of transgene size and type but often a much less efficient gene transfer that is also short-lived. Traditional gene transfer delivers exons while some vectors (lentiviral, herpes and adenoviral) allow transfer of entire genes that include introns. Recent insights have highlighted the role of non-coding RNA, most prominently, siRNA, miRNA and lncRNA. SiRNA is highly specific, miRNA is less specific, while lncRNA uses highly complex mechanisms that involve secondary structures and intergenic, intronic, overlapping, antisense, and bidirectional location. Several promising preclinical studies have targeted the RhoA or the prostaglandin pathway or modified the extracellular matrix. TGF-β and glaucoma myocilin mutants have been transduced to elevate the intraocular pressure in glaucoma models. Cell based therapies have started to show first promise. Past approaches have focused on the trabecular meshwork and the inner wall of Schlemm's canal while new strategies are concerned with modification of outflow tract elements that are downstream of the trabecular meshwork.

Viral vector-based tools advance knowledge of basal ganglia anatomy and physiology

Viral vectors were originally developed to deliver genes into host cells for therapeutic potential. However, viral vector use in neuroscience research has increased because they enhance interpretation of the anatomy and physiology of brain circuits compared with conventional tract tracing or electrical stimulation techniques. Viral vectors enable neuronal or glial subpopulations to be labeled or stimulated, which can be spatially restricted to a single target nucleus or pathway. Here we review the use of viral vectors to examine the structure and function of motor and limbic basal ganglia (BG) networks in normal and pathological states. We outline the use of viral vectors, particularly lentivirus and adeno-associated virus, in circuit tracing, optogenetic stimulation, and designer drug stimulation experiments. Key studies that have used viral vectors to trace and image pathways and connectivity at gross or ultrastructural levels are reviewed. We explain how optogenetic stimulation and designer drugs used to modulate a distinct pathway and neuronal subpopulation have enhanced our mechanistic understanding of BG function in health and pathophysiology in disease. Finally, we outline how viral vector technology may be applied to neurological and psychiatric conditions to offer new treatments with enhanced outcomes for patients.

Immunodynamics: a cancer immunotherapy trials network review of immune monitoring in immuno-oncology clinical trials

The efficacy of PD-1/PD-L1 targeted therapies in addition to anti-CTLA-4 solidifies immunotherapy as a modality to add to the anticancer arsenal. Despite raising the bar of clinical efficacy, immunologically targeted agents raise new challenges to conventional drug development paradigms by highlighting the limited relevance of assessing standard pharmacokinetics (PK) and pharmacodynamics (PD). Specifically, systemic and intratumoral immune effects have not consistently correlated with standard relationships between systemic dose, toxicity, and efficacy for cytotoxic therapies. Hence, PK and PD paradigms remain inadequate to guide the selection of doses and schedules, both starting and recommended Phase 2 for immunotherapies. The promise of harnessing the immune response against cancer must also be considered in light of unique and potentially serious toxicities. Refining immune endpoints to better inform clinical trial design represents a high priority challenge. The Cancer Immunotherapy Trials Network investigators review the immunodynamic effects of specific classes of immunotherapeutic agents to focus immune assessment modalities and sites, both systemic and importantly intratumoral, which are critical to the success of the rapidly growing field of immuno-oncology.

Autophagy interaction with herpes simplex virus type-1 infection

More than 50% of the U.S. population is infected with herpes simplex virus type-I (HSV-1) and global infectious estimates are nearly 90%. HSV-1 is normally seen as a harmless virus but debilitating diseases can arise, including encephalitis and ocular diseases. HSV-1 is unique in that it can undermine host defenses and establish lifelong infection in neurons. Viral reactivation from latency may allow HSV-1 to lay siege to the brain (Herpes encephalitis). Recent advances maintain that HSV-1 proteins act to suppress and/or control the lysosome-dependent degradation pathway of macroautophagy (hereafter autophagy) and consequently, in neurons, may be coupled with the advancement of HSV-1-associated pathogenesis. Furthermore, increasing evidence suggests that HSV-1 infection may constitute a gradual risk factor for neurodegenerative disorders. The relationship between HSV-1 infection and autophagy manipulation combined with neuropathogenesis may be intimately intertwined demanding further investigation.

First oncolytic virus approved for melanoma immunotherapy

On 2015, October 27th, the US Food and Drug Administration (FDA) has officially approved talimogene laherparepvec (T-VEC, also known as OncoVEX^GM-CSF) for use in melanoma patients with injectable but non-resectable lesions in the skin and lymph nodes. T-VEC (which is commercialized by Amgen, Inc. under the name of Imlygic®) becomes therefore the first oncolytic virus approved for cancer therapy in the US.

Assessment of current virotherapeutic application schemes: "hit hard and early" versus "killing softly"?

Over the past two decades, a considerable amount of oncolytic vector families has entered numerous clinical trials. However, to this date, the field has not yet been able to come to a common understanding regarding the best possible ways to administer oncolytic viruses to cancer patients. This is mainly due to the fact that so far clinical trials being designed for head-to-head comparisons (such as using two different virotherapeutics originating from two distinct virus families being applied via identical routes in the same types of cancer) are still missing. Hence, there is no consent (i) on the best route of virotherapeutics administration (e.g., systemic versus intratumoral), (ii) on the virus dosages to be applied, (iii) on dosing intervals, and (iv) on the numbers of repetitive courses of virus administration. As the detailed comparison of clinical virotherapy trial regimens is time-consuming and complex, we here present an overview of current state-of-the-art virotherapeutic application schemes. Notably, our comprehensive assessment culminates in raising two rough classifications of virotherapeutic strategies, i.e., "hit hard and early" versus "killing softly". In order to find out which one of these two gross alternatives might be most successful for each and every tumor entity, we here suggest the implementation of phase 1/2 studies, which primarily aim at a repetitive sampling and analysis of tumor samples in cancer patients treated with oncolytic viruses reading out (i) virus-specific, (ii) tumor-specific as well as (iii) immunotherapeutic parameters. On this basis, a rational design of significantly improved virotherapeutic application schemes should be possible in the future.

Histone deacetylase 6 inhibition enhances oncolytic viral replication in glioma

Oncolytic viral (OV) therapy, which uses genetically engineered tumor-targeting viruses, is being increasingly used in cancer clinical trials due to the direct cytolytic effects of this treatment that appear to provoke a robust immune response against the tumor. As OVs enter tumor cells, intrinsic host defenses have the potential to hinder viral replication and spread within the tumor mass. In this report, we show that histone deacetylase 6 (HDAC6) in tumor cells appears to alter the trafficking of post-entry OVs from the nucleus toward lysosomes. In glioma cell lines and glioma-stem-like cells, HDAC6 inhibition (HDAC6i) by either pharmacologic or genetic means substantially increased replication of oncolytic herpes simplex virus type 1 (oHSV). Moreover, HDAC6i increased shuttling of post-entry oHSV to the nucleus. In addition, electron microscopic analysis revealed that post-entry oHSVs are preferentially taken up into glioma cells through the endosomal pathway rather than via fusion at the cell surface. Together, these findings illustrate a mechanism of glioma cell defense against an incoming infection by oHSV and identify possible approaches to enhance oHSV replication and subsequent lysis of tumor cells.

Molecular Pathways: Targeting the Stimulator of Interferon Genes (STING) in the Immunotherapy of Cancer

Novel immunotherapy approaches are transforming the treatment of cancer, yet many patients remain refractory to these agents. One hypothesis is that immunotherapy fails because of a tumor microenvironment that fails to support recruitment of immune cells, including CD8(+) T cells. Therefore, new approaches designed to initiate a de novo antitumor immune response from within the tumor microenvironment are being pursued. Recent evidence has indicated that spontaneous activation of the Stimulator of Interferon Genes (STING) pathway within tumor-resident dendritic cells leads to type I IFN production and adaptive immune responses against tumors. This pathway is activated in the presence of cytosolic DNA that is detected by the sensor cyclic GMP-AMP synthase (cGAS) and generates cyclic GMP-AMP (cGAMP), which binds and activates STING. As a therapeutic approach, intratumoral injection of STING agonists has demonstrated profound therapeutic effects in multiple mouse tumor models, including melanoma, colon, breast, prostate, and fibrosarcoma. Better characterization of the STING pathway in human tumor recognition, and the development of new pharmacologic approaches to engage this pathway within the tumor microenvironment in patients, are important areas for clinical translation.

Herpes Simplex Virus Vector-Mediated Gene Delivery of Poreless TRPV1 Channels Reduces Bladder Overactivity and Nociception in Rats

Increased afferent excitability has been proposed as an important pathophysiology of interstitial cystitis/bladder pain syndrome (IC/BPS) and overactive bladder (OAB). In this study, we investigated whether herpes simplex virus (HSV) vectors encoding poreless TRPV1, in which the segment in C terminus of TRPV1 receptor is deleted, suppress bladder overactivity and pain behavior using a rat model of chemical cystitis. Replication-defective HSV vectors encoding poreless TRPV1 were injected into the bladder wall of adult female Sprague-Dawley rats. Additionally, recombinant HSV virus (vHG) vectors were injected as control. Cystometry (CMG) under urethane anesthesia was performed 1 week after viral injection to evaluate bladder overactivity induced by resiniferatoxin (RTx, a TRPV1 agonist). RTx-induced nociceptive behavior such as licking (lower abdominal licking) and freezing (motionless head-turning) was observed 2 weeks after viral injection. GFP expression in L4/L6/S1 dorsal root ganglia and the bladder as well as c-Fos-positive cells in the L6 spinal cord dorsal horn were also evaluated 2 weeks after viral injection. In CMG, the poreless TRPV1 vector-treated group showed a significantly smaller reduction in intercontraction intervals and voided volume after RTx infusion than the vHG-treated control group. The number of the RTx-induced freezing events was significantly decreased in the poreless TRPV1 group than in the vHG group, whereas there was no significant difference of the number of RTx-induced licking events between groups. The number of c-Fos-positive cells in the DCM and SPN regions of the L6 spinal dorsal horn was significantly smaller in the poreless TRPV1 group than in the vHG group. Our results indicated that HSV vector-mediated gene delivery of poreless TRPV1 had a therapeutic effect on TRPV1-mediated bladder overactivity and pain behavior. Thus, the HSV vector-mediated gene therapy targeting TRPV1 receptors could be a novel modality for the treatment of OAB and/or hypersensitive bladder disorders such as IC/BPS.

Intratumoral immunotherapy for melanoma

Selection of suitable tumor-associated antigens is a major challenge in the development of effective cancer vaccines. Intratumoral (i.t.) immunotherapy empowers the immune system to mount T cell responses against tumor-associated antigens which are most immunogenic. To mediate systemic tumor regression, i.t. immunotherapy must generate systemic T cell responses that can target distant metastases beyond the initially treated tumor mass. Now that promising preclinical results and some initial success in clinical trials have been obtained, we here review i.t. immunotherapy-related preclinical and clinical studies, their mechanisms of action and future prospects.

Direct Activation of STING in the Tumor Microenvironment Leads to Potent and Systemic Tumor Regression and Immunity

Spontaneous tumor-initiated T cell priming is dependent on IFN-β production by tumor-resident dendritic cells. On the basis of recent observations indicating that IFN-β expression was dependent upon activation of the host STING pathway, we hypothesized that direct engagement of STING through intratumoral (IT) administration of specific agonists would result in effective anti-tumor therapy. After proof-of-principle studies using the mouse STING agonist DMXAA showed a potent therapeutic effect, we generated synthetic cyclic dinucleotide (CDN) derivatives that activated all human STING alleles as well as murine STING. IT injection of STING agonists induced profound regression of established tumors in mice and generated substantial systemic immune responses capable of rejecting distant metastases and providing long-lived immunologic memory. Synthetic CDNs have high translational potential as a cancer therapeutic.

Ad-REIC Gene Therapy: Promising Results in a Patient with Metastatic CRPC Following Chemotherapy

A 63-year-old man with metastatic castration-resistant prostate cancer (CRPC) was successfully treated for two years with in situ gene therapy using an adenovirus vector carrying the human REIC/Dkk-3 gene (Ad-REIC), following chemotherapy. Ad-REIC mediates simultaneous induction of cancer-selective apoptosis and augmentation of antitumor immunity, and a Phase I/IIa clinical study on Ad-REIC has been conducted at Okayama University Hospital since January 2011. At the time of enrollment in December 2012, the patient presented with rapid progression of lymph node (LN) metastases. Two scheduled Ad-REIC injections and 10 additional Ad-REIC injections into metastatic pelvic and para-aortic LNs under CT guidance, with an average four weeks' interval, exhibited the potent direct and indirect effects of Ad-REIC as a therapeutic cancer vaccine. During the next 12 months, three additional injections into para-aortic LNs showing regrowth achieved adequate control of all metastatic LNs with prostate-specific antigen (PSA) decline, without any particular adverse events.

Chemovirotherapy: combining chemotherapeutic treatment with oncolytic virotherapy

Oncolytic virotherapy has made significant progress in recent years, however, widespread approval of virotherapeutics is still limited. Primarily, this is due to the fact that currently available virotherapeutics are mostly tested in monotherapeutic clinical trials exclusively (ie, not in combination with other therapies) and so far have achieved only small and often clinically insignificant responses. Given that the predominantly immunotherapeutic mechanism of virotherapeutics is somewhat time-dependent and rapidly growing tumors therefore exhibit only minor chances of being captured in time, scenarios with combination partners are postulated to be more effective. Combinatory settings would help to achieve a rapid stabilization or even reduction of onset tumor masses while providing enough time (numerous months) for achieving immuno(viro)therapeutic success. For this reason, combination strategies of virotherapy with highly genotoxic regimens, such as chemotherapy, are of major interest. A number of clinical trials bringing the concepts of chemotherapy and virotherapy together have previously been undertaken, but optimal scheduling of chemovirotherapy (maximizing the anti-tumor effect while minimizing the risk of overlapping toxicity) still constitutes a major challenge. Therefore, an overview of published as well as ongoing Phase I–III trials should improve our understanding of current challenges and future developments in this field.

Oncolytic HSV virotherapy in murine sarcomas differentially triggers an antitumor T-cell response in the absence of virus permissivity

Multiple studies have indicated that in addition to direct oncolysis, virotherapy promotes an antitumor cytotoxic T cell response important for efficacy. To study this phenomenon further, we tested three syngeneic murine sarcoma models that displayed varied degrees of permissiveness to oncolytic herpes simplex virus replication and cytotoxicity in vitro, with the most permissive being comparable to some human sarcoma tumor lines. The in vivo antitumor effect ranged from no or modest response to complete tumor regression and protection from tumor rechallenge. The in vitro permissiveness to viral oncolysis was not predictive of the in vivo antitumor effect, as all three tumors showed intact interferon signaling and minimal permissiveness to virus in vivo. Tumor shrinkage was T-cell mediated with a tumor-specific antigen response required for maximal antitumor activity. Further analysis of the innate and adaptive immune microenvironment revealed potential correlates of susceptibility and resistance, including favorable and unfavorable cytokine profiles, differential composition of intratumoral myeloid cells, and baseline differences in tumor cell immunogenicity and tumor-infiltrating T-cell subsets. It is likely that a more complete understanding of the interplay between the immunologic immune microenvironment and virus infection will be necessary to fully leverage the antitumor effects of this therapeutic platform.