Constitutive Interferon Pathway Activation in Tumors as an Efficacy Determinant Following Oncolytic Virotherapy

The Role and Therapeutic Targeting of JAK/STAT Signaling in Glioblastoma

Glioblastoma remains one of the deadliest and treatment-refractory human malignancies in large part due to its diffusely infiltrative nature, molecular heterogeneity, and capacity for immune escape. The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway contributes substantively to a wide variety of protumorigenic functions, including proliferation, anti-apoptosis, angiogenesis, stem cell maintenance, and immune suppression. We review the current state of knowledge regarding the biological role of JAK/STAT signaling in glioblastoma, therapeutic strategies, and future directions for the field.

Live Attenuated Measles Virus Vaccine Expressing Helicobacter pylori Heat Shock Protein A

Measles virus (MV) Edmonston derivative strains are attractive vector platforms in vaccine development and oncolytic virotherapy. Helicobacter pylori heat shock protein A (HspA) is a bacterial heat shock chaperone with essential function as a Ni-ion scavenging protein. We generated and characterized the immunogenicity of an attenuated MV strain encoding the HspA transgene (MV-HspA). MV-HspA showed faster replication within 48 h of infection with >10-fold higher titers and faster accumulation of the MV proteins. It also demonstrated a superior tumor-killing effect in vitro against a variety of human solid tumor cell lines, including sarcoma, ovarian and breast cancer. Two intraperitoneal (i.p.) doses of 10⁶ 50% tissue culture infectious dose (TCID₅₀) MV-HspA significantly improved survival in an ovarian cancer xenograft model: 63.5 days versus 27 days for the control group. The HspA transgene induced a humoral immune response in measles-permissive Ifnarko-CD46Ge transgenic mice. Eight of nine animals developed a long-term anti-HspA antibody response with titers of 1:400 to 1:12,800 without any negative impact on development of protective anti-MV immune memory. MV-HspA triggered an immunogenic cytopathic effect as measured by an HMGB1 assay. The absence of significant elevation of PD-L1 expression indicated that vector-encoded HspA could act as an immunomodulator on the immune check point axis. These data demonstrate that MV-HspA is a potent oncolytic agent and vaccine candidate for clinical translation in cancer treatment and immunoprophylaxis against H. pylori.

Lassa-VSV chimeric virus targets and destroys human and mouse ovarian cancer by direct oncolytic action and by initiating an anti-tumor response

Ovarian cancer is the third most common female cancer, with poor survival in later stages of metastatic spread. We test a chimeric virus consisting of genes from Lassa and vesicular stomatitis viruses, LASV-VSV; the native VSV glycoprotein is replaced by the Lassa glycoprotein, greatly reducing neurotropism. Human ovarian cancer cells in immunocompromised nude mice were lethal in controls. Chemotherapeutic paclitaxel and cisplatin showed modest cancer inhibition and survival extension. In contrast, a single intraperitoneal injection of LASV-VSV selectively infected and killed ovarian cancer cells, generating long-term survival. Mice with human ovarian cancer cells in brain showed rapid deterioration; LASV-VSV microinjection into brain blocked cancer growth, and generated long-term survival. Treatment of immunocompetent mice with infected mouse ovarian cancer cells blocked growth of non-infected ovarian cancer cells peritoneally and in brain. These results suggest LASV-VSV is a viable candidate for further study and may be of use in the treatment of ovarian cancer.

Identification of oncolytic vaccinia restriction factors in canine high-grade mammary tumor cells using single-cell transcriptomics

Mammary carcinoma, including triple-negative breast carcinomas (TNBC) are tumor-types for which human and canine pathologies are closely related at the molecular level. The efficacy of an oncolytic vaccinia virus (VV) was compared in low-passage primary carcinoma cells from TNBC versus non-TNBC. Non-TNBC cells were 28 fold more sensitive to VV than TNBC cells in which VV replication is impaired. Single-cell RNA-seq performed on two different TNBC cell samples, infected or not with VV, highlighted three distinct populations: naïve cells, bystander cells, defined as cells exposed to the virus but not infected and infected cells. The transcriptomes of these three populations showed striking variations in the modulation of pathways regulated by cytokines and growth factors. We hypothesized that the pool of genes expressed in the bystander populations was enriched in antiviral genes. Bioinformatic analysis suggested that the reduced activity of the virus was associated with a higher mesenchymal status of the cells. In addition, we demonstrated experimentally that high expression of one gene, DDIT4, is detrimental to VV production. Considering that DDIT4 is associated with a poor prognosis in various cancers including TNBC, our data highlight DDIT4 as a candidate resistance marker for oncolytic poxvirus therapy. This information could be used to design new generations of oncolytic poxviruses. Beyond the field of gene therapy, this study demonstrates that single-cell transcriptomics can be used to identify cellular factors influencing viral replication.

The identification of cellular genes influencing viral replication/propagation has been studied using hypothesis-driven approaches and/or high-throughput RNA interference screens. In the present report, we propose a methodology based on single-cell transcriptomics. We have studied, in the context of oncolytic virotherapy, the susceptibility of different grades of primary low-passage mammary carcinoma cells of canine origin to an oncolytic vaccinia virus (VV). We highlight a fault in replication of VV in cells that originated from high-grade triple-negative breast carcinomas (TNBC). Single-cell RNA-seq performed on TNBC cell samples infected with VV suggested that the reduced activity of the virus was associated with a higher mesenchymal status of the cells. We also demonstrate that high expression of one gene, DDIT4, is detrimental to VV production. Considering that DDIT4 is associated with a poor prognosis in various cancers including TNBC, our data highlight DDIT4 as a candidate resistance marker for oncolytic poxvirus therapy. Beyond the field of cancer gene therapy, we demonstrate here that single-cell transcriptomics increases the arsenal of tools available to identify cellular factors influencing viral replication.

New hints towards a precision medicine strategy for IDH wild-type glioblastoma

Glioblastoma represents the most common primary malignancy of the central nervous system in adults and remains a largely incurable disease. The elucidation of disease subtypes based on mutational profiling, gene expression and DNA methylation has so far failed to translate into improved clinical outcomes. However, new knowledge emerging from the subtyping effort in the IDH-wild-type setting may provide directions for future precision therapies. Here, we review recent learnings in the field, and further consider how tumour microenvironment differences across subtypes may reveal novel contexts of vulnerability. We discuss recent treatment approaches and ongoing trials in the IDH-wild-type glioblastoma setting, and propose an integrated discovery stratagem incorporating multi-omics, single-cell technologies and computational approaches.

Measles virus in cancer therapy

Over the last years, the development of viruses to treat cancer patients has re-gained considerable attention. A genetically modified herpesvirus, Talimogene laherparepvec, has already been authorized for the treatment of melanoma patients. Also recombinant measles virus (MeV) is developed as an oncolytic virus. Because of its high genetic flexibility, a number of different MeV strains have been the basis for the generation of targeted, armed, or shielded viruses that are highly specific for a given tumor target, more effective, or protected against serum neutralization. Such MeV have been extensively tested in vitro and in vivo, whereby remarkable oncolytic potency is accompanied by safety also in non-human primates. Therefore, MeV has been introduced into 19 different clinical trials and has reached phase II against two different tumor entities, multiple myeloma and ovarian carcinoma. Remarkably, one patient with advanced stage myeloma experienced long-term remission after treatment, visualizing the potency of this approach.

Retargeted and Stealth-Modified Oncolytic Measles Viruses for Systemic Cancer Therapy in Measles Immune Patients

Measles viruses (MV) are rapidly inactivated by anti-measles neutralizing antibodies, which has limited their clinical performance as oncolytic agents. Here, by substituting the H and F surface glycoproteins of MV with those from the homologous canine distemper virus (CDV) and engineering the CDV H attachment protein to target EGFR or CD38, we generated a fully retargeted MV capable of resisting neutralization by measles-immune human serum. The resultant recombinant MVs encoding retargeted CDV envelope glycoproteins had similar growth kinetics as the control MV, showed the expected engineered receptor specificities for cell entry, intercellular fusion, and target cell killing, and were blind to native CDV receptors. In contrast to the control MV, recombinant MVs incorporating CDV F and H glycoproteins retained full infectivity when exposed to high concentrations of pooled measles-immune human serum. Comparing viruses bearing MV or CDV glycoproteins in the SKOV3ip.1 model, only the virus bearing an EGFR-retargeted CDV envelope glycoprotein complex was capable of limiting tumor growth and extending the survival in measles immune mice. MV, "stealthed" and retargeted using engineered CDV surface glycoproteins, may be a promising platform to advance for systemic cancer therapy in measles immune patients.

Targeting the JAK/STAT pathway in solid tumors

Aberrant activation of signal transducer and activator of transcription (STAT) proteins is associated with the development and progression of solid tumors. However, as transcription factors, these proteins are difficult to target directly. In this review, we summarize the role of targeting Janus kinases (JAKs), upstream activators of STATs, as a strategy for decreasing STAT activation in solid tumors. Preclinical studies in solid tumor cell line models show that JAK inhibitors decrease STAT activation, cell proliferation, and cell survival; in in vivo models, they also inhibit tumor growth. JAK inhibitors, particularly the JAK1/2 inhibitor ruxolitinib, sensitize cell lines and murine models to chemotherapy, immunotherapy, and oncolytic viral therapy. Ten JAK inhibitors have been or are actively being tested in clinical trials as monotherapy or in combination with other agents in patients with solid tumors; two of these inhibitors are already Food and Drug Administration (FDA) approved for the treatment of myeloproliferative disorders and rheumatoid arthritis, making them attractive agents for use in patients with solid tumors as they are known to be well-tolerated. Four JAK inhibitors (two of which are FDA approved for other indications) have exhibited promising anti-cancer effects in preclinical studies; however, clinical studies specifically assessing their activity against the JAK/STAT pathway in solid tumors have not yet been conducted. In summary, JAK inhibition is a viable option for targeting the JAK/STAT pathway in solid tumors and merits further testing in clinical trials.

Mechanisms of measles virus oncolytic immunotherapy

The study of measles virus (MeV) as a cancer immunotherapeutic was prompted by clinical observations of leukemia and lymphoma regressions in patients following measles virus infection in the 1970s and 1980s. Since then, numerous preclinical studies have confirmed the oncolytic activity of MeV vaccine strains as well as their potential to promote long-lasting tumor-specific immune responses. Early clinical data indicate that some of these effects may translate to the treatment of cancer patients. In this review, we provide a structured summary of current evidence for the anti-tumor immune activity of oncolytic MeV. We start with an overview of MeV oncolysis and MeV-induced immunogenic cell death. Next, we relate findings on MeV-mediated activation of antigen-presenting cells, T cell priming and effector mechanisms to the cancer immunity cycle. We discuss additional factors in the tumor microenvironment which are modulated by MeV treatment as well as the role of anti-viral immunity. Based on these findings, we highlight avenues for rational enhancement of oncolytic MeV immunotherapy by vector engineering. We further point to advantages and drawbacks of experimental models and propose areas warranting promising research. Lastly, we review the available immunomonitoring data from several Phase I clinical trials. While this review presents data for MeV, the concepts and principles introduced herein apply to other oncolytic viruses, providing a framework to assess novel cancer immunotherapies.

Collateral Lethal Effects of Complementary Oncolytic Viruses

Virus-infected cells release type 1 interferons, which induce an antiviral state in neighboring cells. Naturally occurring viruses are therefore equipped with stealth replication strategies to limit virus sensing and/or with combat strategies to prevent or reverse the antiviral state. Here we show that oncolytic viruses with simple RNA genomes whose spread was suppressed in tumor cells pretreated with interferon were able to replicate efficiently when the cells were coinfected with a poxvirus known to encode a diversity of innate immune combat proteins. In vivo the poxvirus was shown to reverse the intratumoral antiviral state, rescuing RNA virus replication in an otherwise restrictive syngeneic mouse tumor model leading to antitumor efficacy. Pairing of complementary oncolytic viruses is a promising strategy to enhance the antitumor activity of this novel class of anticancer drugs.

Developing oncolytic viruses for clinical use: A consortium approach

The use of oncolytic viruses forms an appealing approach for cancer treatment. On the one hand the viruses replicate in, and kill, tumor cells, leading to their intra-tumoral amplification. On the other hand the viral infection will activate virus-directed immune responses, and may trigger immune responses directed against tumor cells and tumor antigens. To date, a wide variety of oncolytic viruses is being developed for use in cancer treatment. While the development of oncolytic viruses has often been initiated by researchers in academia and other public institutions, a large majority of the final product development and the testing of these products in clinical trials is industry led. As a consequence relatively few pre-clinical and clinical studies evaluated different oncolytic viruses in competitive side-by-side preclinical or clinical studies. In this review we will summarize the steps and considerations essential in the development and characterization of oncolytic viruses, and describe our multidisciplinary academic consortium, which involves a dozen departments in three different Dutch universities, collaborating in the development of oncolytic viruses. This consortium has the ambition to develop a small series of oncolytic viruses and to evaluate these in various cancers.

Virotherapy: From single agents to combinatorial treatments

Virotherpay is emerging as a promising strategy against cancer, and three oncolytic viruses (OVs) have gained approval in different countries for the treatment of several cancer types. Beyond the capability to selectively infect, replicate and lyse cancer cells, OVs act through a multitude of events, including modification of the tumour micro/macro-environment as well as a complex modulation of the anti-tumour immune response by activation of danger signals and immunogenic cell death pathways. Most OVs show limited effects, depending on the viral platform and the interactions with the host. OVs used as monotherapy only in a minority of patients elicited a full response. Better outcomes were obtained using OVs in combination with other treatments, such as immune therapy or chemotherapy, suggesting that the full potential of OVs can be unleashed in combination with other treatment modalities. Here, we report the main described combination of OVs with conventional chemotherapeutic agents: platinum salts, mitotic inhibitors, anthracyclines and other antibiotics, anti-metabolites, alkylating agents and topoisomerase inhibitors. Additionally, our work provides an overview of OV combination with targeted therapies: histone deacetylase inhibitors, kinase inhibitors, monoclonal antibodies, inhibitors of DNA repair, inhibitors of the proteasome complex and statins that demonstrated enhanced OV anti-neoplastic activity. Although further studies are required to assess the best combinations to translate the results in the clinic, it is clear that combined therapies, acting with complementary mechanisms of action might be useful to target cancer lesions resistant to currently available treatments.

Oncolytic Virus Encoding a Master Pro-Inflammatory Cytokine Interleukin 12 in Cancer Immunotherapy

Oncolytic viruses (OVs) are genetically modified or naturally occurring viruses, which preferentially replicate in and kill cancer cells while sparing healthy cells, and induce anti-tumor immunity. OV-induced tumor immunity can be enhanced through viral expression of anti-tumor cytokines such as interleukin 12 (IL-12). IL-12 is a potent anti-cancer agent that promotes T-helper 1 (Th1) differentiation, facilitates T-cell-mediated killing of cancer cells, and inhibits tumor angiogenesis. Despite success in preclinical models, systemic IL-12 therapy is associated with significant toxicity in humans. Therefore, to utilize the therapeutic potential of IL-12 in OV-based cancer therapy, 25 different IL-12 expressing OVs (OV-IL12s) have been genetically engineered for local IL-12 production and tested preclinically in various cancer models. Among OV-IL12s, oncolytic herpes simplex virus encoding IL-12 (OHSV-IL12) is the furthest along in the clinic. IL-12 expression locally in the tumors avoids systemic toxicity while inducing an efficient anti-tumor immunity and synergizes with anti-angiogenic drugs or immunomodulators without compromising safety. Despite the rapidly rising interest, there are no current reviews on OV-IL12s that exploit their potential efficacy and safety to translate into human subjects. In this article, we will discuss safety, tumor-specificity, and anti-tumor immune/anti-angiogenic effects of OHSV-IL12 as mono- and combination-therapies. In addition to OHSV-IL12 viruses, we will also review other IL-12-expressing OVs and their application in cancer therapy.

The Susceptibility of Human Melanoma Cells to Infection with the Leningrad-16 Vaccine Strain of Measles Virus

Oncolytic viruses, including live attenuated measles virus (MV) vaccine strains, have recently been shown as promising therapeutic agents against human malignancies. In this study, the oncolytic potential of the attenuated vaccine strain Leningrad-16 (L-16) of MV was evaluated in a panel of human metastatic melanoma cell lines. The L-16 measles virus was shown to replicate within melanoma cells mediating direct cell killing of tumor cells, although all melanoma cell lines varied in regard to their ability to respond to L-16 MV infection, as revealed by the different pattern of the Interferon Stimulated Gene expression, cytokine release and mechanisms of cell death. Furthermore, the statistically significant L-16 measles virus related tumor growth inhibition was demonstrated in a melanoma xenograft model. Therefore, L-16 MV represents an appealing oncolytic platform for target delivery of therapeutic genes along with other attenuated measles virus strains.

Type 1 Interferon Responses Underlie Tumor-Selective Replication of Oncolytic Measles Virus

The mechanism of tumor-selective replication of oncolytic measles virus (MV) is poorly understood. Using a stepwise model of cellular transformation, in which oncogenic hits were additively expressed in human bone marrow-derived mesenchymal stromal cells, we show that MV-induced oncolysis increased progressively with transformation. The type 1 interferon (IFN) response to MV infection was significantly reduced and delayed, in accordance with the level of transformation. Consistently, we observed delayed and reduced signal transducer and activator of transcription (STAT1) phosphorylation in the fully transformed cells. Pre-treatment with IFNβ restored resistance to MV-mediated oncolysis. Gene expression profiling to identify the genetic correlates of susceptibility to MV oncolysis revealed a dampened basal level of immune-related genes in the fully transformed cells compared to their normal counterparts. IFN-induced transmembrane protein 1 (IFITM1) was the foremost basally downregulated immune gene. Stable IFITM1 overexpression in MV-susceptible cells resulted in a 50% increase in cell viability and a significant reduction in viral replication at 24 h after MV infection. Overall, our data indicate that the basal reduction in functions of the type 1 IFN pathway is a major contributor to the oncolytic selectivity of MV. In particular, we have identified IFITM1 as a restriction factor for oncolytic MV, acting at early stages of infection.

Frequent Homozygous Deletions of Type I Interferon Genes in Pleural Mesothelioma Confer Sensitivity to Oncolytic Measles Virus

INTRODUCTION

Oncolytic immunotherapy is based on the use of nonpathogenic replicative oncolytic viruses that infect and kill tumor cells exclusively. Recently, we found that the spontaneous oncolytic activity of the Schwarz strain of measles virus (MV) against human malignant pleural mesothelioma (MPM) depends on defects in the antiviral type I interferon (IFN-I) response in tumor cells.

METHODS

In this study, we studied three independent human MPM bio-collections to identify the defects in the IFN-I responses in tumor cells.

RESULTS

We show that the most frequent defect is the homozygous deletions (HDs) of all the 14 IFN-I genes (IFN-α and IFN-β) that we found in more than half of MV-sensitive MPM cell lines. These HDs occur together with the HDs of the tumor suppressor gene CDKN2A also located in the 9p21.3 chromosome region. Therefore, the IFN-I^-/- MPM cell lines develop a partial and weak IFN-I response when they are exposed to the virus compared with that of normal cells and MV-resistant MPM cell lines. This response consists of the expression of a restricted number of IFN-stimulated genes that do not depend on the presence of IFN-I. In addition, the IFN-I^-/- MPM cell lines infected by MV also develop a pro-inflammatory response associated with stress of the endoplasmic reticulum.

CONCLUSION

Our study emphasizes the link between HDs of IFN-I encoding genes and the CDKN2A gene in MPM and sensitivity to MV oncolytic immunotherapy.

Immunomodulation in Oncolytic Measles Virotherapy

With the recognition of oncolytic virotherapy as an immunotherapy, the distinct interactions between oncolytic agents and the immune system have come into focus. The role of the immune system in oncolytic virotherapy is somewhat ambiguous: While preexisting or arising immunity directed against viral antigens may preclude efficient viral replication and spread, immunity directed against tumor antigens is considered essential for long-term treatment success. Aside from the antiviral and antitumor immune status of the patient, the specific immunological microenvironment in a given tumor adds an additional layer of complexity.In this review we focus on the case of measles virus, which has long been known for its multifaceted interplay with the immune system. The high prevalence of measles-neutralizing antibodies in the general population may pose additional challenges. The oncolytic measles virus vector platform offers manifold opportunities for tumor-targeted immunomodulation. This review provides a survey of immunomodulation in the context of measles virotherapy including strategies to suppress or circumvent antiviral immunity as well as enhance antitumor immunity that have been pursued in preclinical and clinical studies. Understanding and selective manipulation of the intricate balance between antiviral and antitumor immunity will be crucial to develop the full potential of oncolytic virotherapy.

The potential of the combined use of targeted type I interferon pathway inhibitors and oncolytic viruses to treat sarcomas

Replicating oncolytic viruses (OVs) are appealing, new, FDA-approved, therapeutic options for humans with head and neck cancers and melanomas. These treatments are not yet available for veterinary patients, but recent clinical trials have shown several OVs to be safe in dogs and cats. Specific viruses being used to treat sarcomas in dogs include modified canine adenovirus 2, myxoma virus, vesicular stomatitis virus and reovirus. In cats with vaccine-associated sarcomas, poxviruses have been injected postoperatively and a reduced rate of tumour recurrence was documented. To date, the response rates of canine and feline patients to OV therapy have been variable (as they are in people). Optimal methods of OV administration and dosing schedules continue to be evaluated. One way to improve outcomes of OV therapy in veterinary patients may be to use OVs in combination with other immunomodulatory therapies. This review discusses the potential utility of concurrent therapy with an OV and an inhibitor of the type I interferon pathway.

Oncolytic Measles Virotherapy and Opposition to Measles Vaccination

Recent measles epidemics in US and European cities where vaccination coverage has declined are providing a harsh reminder for the need to maintain protective levels of immunity across the entire population. Vaccine uptake rates have been declining in large part because of public misinformation regarding a possible association between measles vaccination and autism for which there is no scientific basis. The purpose of this article is to address a new misinformed antivaccination argument-that measles immunity is undesirable because measles virus is protective against cancer. Having worked for many years to develop engineered measles viruses as anticancer therapies, we have concluded (1) that measles is not protective against cancer and (2) that its potential utility as a cancer therapy will be enhanced, not diminished, by prior vaccination.

Optimizing oncolytic virotherapy in cancer treatment

In the wake of the success of modern immunotherapy, oncolytic viruses (OVs) are currently seen as a potential therapeutic option for patients with cancer who do not respond or fail to achieve durable responses following treatment with immune checkpoint inhibitors. OVs offer a multifaceted therapeutic platform because they preferentially replicate in tumour cells, can be engineered to express transgenes that augment their cytotoxic and immunostimulatory activities, and modulate the tumour microenvironment to optimize immune-mediated tumour eradication, both at locoregional and systemic sites of disease. Lysis of tumour cells releases tumour-specific antigens that trigger both the innate and adaptive immune systems. OVs also represent attractive combination partners with other systemically delivered agents by virtue of their highly favourable safety profiles. Rational combinations of OVs with different immune modifiers and/or antitumour agents, based on mechanisms of tumour resistance to immune-mediated attack, may benefit the large, currently underserved, population of patients who respond poorly to immune checkpoint inhibition.

Systematic Review of Patient-Derived Xenograft Models for Preclinical Studies of Anti-Cancer Drugs in Solid Tumors

Patient-derived xenograft (PDX) models are used as powerful tools for understanding cancer biology in PDX clinical trials and co-clinical trials. In this systematic review, we focus on PDX clinical trials or co-clinical trials for drug development in solid tumors and summarize the utility of PDX models in the development of anti-cancer drugs, as well as the challenges involved in this approach, following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Recently, the assessment of drug efficacy by PDX clinical and co-clinical trials has become an important method. PDX clinical trials can be used for the development of anti-cancer drugs before clinical trials, with their efficacy assessed by the modified response evaluation criteria in solid tumors (mRECIST). A few dozen cases of PDX models have completed enrollment, and the efficacy of the drugs is assessed by 1 × 1 × 1 or 3 × 1 × 1 approaches in the PDX clinical trials. Furthermore, co-clinical trials can be used for personalized care or precision medicine with the evaluation of a new drug or a novel combination. Several PDX models from patients in clinical trials have been used to assess the efficacy of individual drugs or drug combinations in co-clinical trials.

A key anti-viral protein, RSAD2/VIPERIN, restricts the release of measles virus from infected cells

Measles virus (MV), a paramyxovirus, is one of the most contagious human pathogens and is responsible for thousands of deaths annually. Wild-type MV evolved to counter the innate immune system by avoiding both type I interferon (IFN) induction and inhibiting IFN signaling through the JAK/STAT pathway. However, virus replication is significantly inhibited in IFN-pretreated cells. Similarly, MV vaccine derived strains are inhibited by IFN pretreatment, but vaccine strains also induce IFN. Despite the significant progress in understanding the interactions between MV and the IFN pathway, the IFN stimulated genes (ISGs) that inhibit MV replication remain largely unknown. The aim of this study is to identify specific ISGs that mediate restriction of MV. In this study, we report that Radical S-adenosyl methionine domain containing 2 (RSAD2) restricts MV infection at the stage of virus release in infected 293T cells. Furthermore, attenuated MV strains are currently being developed as a novel treatment for solid and hematological malignancies. Therefore, we tested the impact of RSAD2 expression in an oncolytic virotherapy context using a MV permissive ovarian cancer line (SR-B2). As measured in 293T cells, MV release was also impaired in SR-B2 cells transduced to express RSAD2 in vitro. Additionally, oncolytic MV therapeutic efficacy was impaired in SR-B2 cells transduced to express RSAD2 in vivo. Overall, we identify RSAD2 as a novel restriction factor for MV by inhibiting the release of virus. These results provide important information regarding the interaction between MV and the innate immune system, as well as implications for the design of oncolytic MV platforms.

Measles Virus-Based Treatments Trigger a Pro-inflammatory Cascade and a Distinctive Immunopeptidome in Glioblastoma

Glioblastoma is an aggressive primary brain tumor with bad prognosis. On the other hand, oncolytic measles virus (MeV) therapy is an experimental glioma treatment strategy with clinical safety and first evidence of anti-tumoral efficacy. Therefore, we investigated the combination of MeV with conventional therapies by cytotoxic survival assays in long-term glioma cell lines LN229, LNZ308, and glioma stem-like GS8 cells, as well as the basal viral infectivity in primary glioblastoma cultures T81/16, T1094/17, and T708/16. We employed Chou-Talalay analysis to identify the synergistic treatment sequence chemotherapy, virotherapy, and finally radiotherapy (CT-VT-RT). RNA sequencing and immunopeptidome analyses were used to delineate treatment-induced molecular and immunological profiles. CT-VT-RT displayed synergistic anti-glioma activity and initiated a type 1 interferon response, along with canonical Janus kinase-signal transducers and activators of transcription (JAK-STAT) signaling, and downstream interferon-stimulated genes were induced, resulting in apoptotic cascades. Furthermore, antigen presentation along with immunostimulatory chemokines was increased in CT-VT-RT-treated glioma cells, indicating a treatment-induced pro-inflammatory phenotype. We identified novel treatment-induced viral and tumor-associated peptides through HLA ligandome analysis. Our data delineate an actionable treatment-induced molecular and immunological signature of CT-VT-RT, and they could be exploited for the design of novel tailored treatment strategies involving virotherapy and immunotherapy.

Synthesis and Translation of Viral mRNA in Reovirus-Infected Cells: Progress and Remaining Questions

At the end of my doctoral studies, in 1988, I published a review article on the major steps of transcription and translation during the mammalian reovirus multiplication cycle, a topic that still fascinates me 30 years later. It is in the nature of scientific research to generate further questioning as new knowledge emerges. Our understanding of these fascinating viruses thus remains incomplete but it seemed appropriate at this moment to look back and reflect on our progress and most important questions that still puzzle us. It is also essential of being careful about concepts that seem so well established, but could still be better validated using new approaches. I hope that the few reflections presented here will stimulate discussions and maybe attract new investigators into the field of reovirus research. Many other aspects of the viral multiplication cycle would merit our attention. However, I will essentially limit my discussion to these central aspects of the viral cycle that are transcription of viral genes and their phenotypic expression through the host cell translational machinery. The objective here is not to review every aspect but to put more emphasis on important progress and challenges in the field.

Oncolytic Viruses on Drugs: Achieving Higher Therapeutic Efficacy

Over the past 20 years there has been a dramatic expansion in the testing of oncolytic viruses (OVs) for the treatment of cancer. OVs are unique biotherapeutics that induce multimodal responses toward tumors, from direct cytopathic effects on cancer cells, to tumor associated blood vessel disruption, and ultimately potent stimulation of anti-tumor immune activation. These agents are highly targeted and can be efficacious as cancer treatments resulting in some patients experiencing complete tumor regression and even cures from OV monotherapy. However, most patients have limited responses with viral replication in tumors often found to be modest and transient. To augment OV replication, increase bystander killing of cancer cells, and/or stimulate stronger targeted anti-cancer immune responses, drug combination approaches have taken center stage for translation to the clinic. Here we comprehensively review drugs that have been combined with OVs to increase therapeutic efficacy, examining the proposed mechanisms of action, and we discuss trends in pharmaco-viral immunotherapeutic approaches currently being investigated.