Oncolytic Vesicular Stomatitis Virus Research Articles

Oncolytic virus-mediated expansion of dual-specific CAR T cells improves efficacy against solid tumors in mice.

Oncolytic viruses (OVs) encoding a variety of transgenes have been evaluated as therapeutic tools to increase the efficacy of chimeric antigen receptor (CAR)-modified T cells in the solid tumor microenvironment (TME). Here, using systemically delivered OVs and CAR T cells in immunocompetent mouse models, we have defined a mechanism by which OVs can potentiate CAR T cell efficacy against solid tumor models of melanoma and glioma. We show that stimulation of the native T cell receptor (TCR) with viral or virally encoded epitopes gives rise to enhanced proliferation, CAR-directed antitumor function, and distinct memory phenotypes. In vivo expansion of dual-specific (DS) CAR T cells was leveraged by in vitro preloading with oncolytic vesicular stomatitis virus (VSV) or reovirus, allowing for a further in vivo expansion and reactivation of T cells by homologous boosting. This treatment led to prolonged survival of mice with subcutaneous melanoma and intracranial glioma tumors. Human CD19 CAR T cells could also be expanded in vitro with TCR reactivity against viral or virally encoded antigens and was associated with greater CAR-directed cytokine production. Our data highlight the utility of combining OV and CAR T cell therapy and show that stimulation of the native TCR can be exploited to enhance CAR T cell activity and efficacy in mice.

Natural killer T cell immunotherapy combined with IL-15-expressing oncolytic virotherapy and PD-1 blockade mediates pancreatic tumor regression

BackgroundPancreatic cancer is one of the leading causes of cancer death, with a 5-year -year survival rate of less than 10%. This results from late detection, high rates of metastasis,...

Clinical activity of single-dose systemic oncolytic VSV virotherapy in patients with relapsed refractory T-cell lymphoma

AbstractClinical success with intravenous (IV) oncolytic virotherapy (OV) has to-date been anecdotal. We conducted a phase 1 clinical trial of systemic OV and investigated the mechanisms of action in responding patients. A single IV dose of vesicular stomatitis virus (VSV) interferon-β (IFN-β) with sodium iodide symporter (NIS) was administered to patients with relapsed/refractory hematologic malignancies to determine safety and efficacy across 4 dose levels (DLs). Correlative studies were undertaken to evaluate viremia, virus shedding, virus replication, and immune responses. Fifteen patients received VSV-IFNβ-NIS. Three patients were treated at DL1 through DL3 (0.05, 0.17, and 0.5 × 1011 TCID50), and 6 were treated at DL4 (1.7 × 1011 TCID50) with no dose-limiting toxicities. Three of 7 patients with T-cell lymphoma (TCL) had responses: a 3-month partial response (PR) at DL2, a 6-month PR, and a complete response (CR) ongoing at 20 months at DL4. Viremia peaked at the end of infusion, g was detected. Plasma IFN-β, a biomarker of VSV-IFNβ-NIS replication, peaked between 4 hours and 48 hours after infusion. The patient with CR had robust viral replication with increased plasma cell-free DNA, high peak IFN-β of 18 213 pg/mL, a strong anti-VSV neutralizing antibody response, and increased numbers of tumor reactive T-cells. VSV-IFNβ-NIS as a single agent was effective in patients with TCL, resulting in durable disease remissions in heavily pretreated patients. Correlative analyses suggest that responses may be due to a combination of direct oncolytic tumor destruction and immune-mediated tumor control. This trial is registered at www.clinicaltrials.gov as #NCT03017820.

Intravesical immunotherapy with a GM-CSF armed oncolytic vesicular stomatitis virus improves outcome in bladder cancer

A significant proportion of non-muscle invasive bladder cancer cases will progress to muscle invasive disease. Transurethral resection followed by Bacillus Calmette Guerin immunotherapy can reduce this risk, while cystectomy prior to muscle invasion provides the best option for survival. Currently, there are no effective treatments for Bacillus Calmette Guerin refractory disease. A novel oncolytic vesicular stomatitis virus containing the human GM-CSF transgene (VSVd51-hGM-CSF) was rescued and tested as a potential bladder-sparing therapy for aggressive bladder cancer. The existing variant expressing mouse GM-CSF was also used. Measurement of gene expression and protein level alterations of canonical immunogenic cell death associated events on mouse and human bladder cancer cell lines and spheroids showed enhanced release of danger signals and immunogenic factors following infection with VSVd51-m/hGM-CSF. Intravesical instillation of VSVd51-mGM-CSF into MB49 bladder cancer bearing C57Bl/6 mice demonstrated enhanced activation of peripheral and bladder infiltrating effector immune cells, along with improved survival and reduced tumor volume. Importantly, virus-mediated anti-tumor immunity was recapitulated in bladder cancer patient-derived organoids. These results suggest that VSVd51-hGM-CSF is a promising viro/immunotherapy that could benefit bladder cancer patients.

The phosphoinositide 3-kinase inhibitor ZSTK474 increases the susceptibility of osteosarcoma cells to oncolytic vesicular stomatitis virus VSVΔ51 via aggravating endoplasmic reticulum stress

ABSTRACT Blockage of phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signal pathway is effective to increase the cytotoxic effects of oncolytic virus on cancer cells, but the detailed mechanisms are still largely unknown. Based on this, the present study managed to investigate the anti-tumor effects of PI3K inhibitor ZSTK474 and oncolytic vesicular stomatitis virus VSVΔ51 combination treatments on osteosarcoma (OS) in vitro and in vivo. Specifically, ZSTK474 aggravated the inhibiting effects of VSVΔ51 on osteosarcoma development by triggering endoplasmic reticulum (ER)-stress mediated apoptotic cell death. Mechanistically, either ZSTK474 or VSVΔ51 alone had limited effects on cell viability in osteosarcoma cells, while ZSTK474 and VSVΔ51 combination treatments significantly induced osteosarcoma cell apoptosis. Interestingly, VSVΔ51 increased the expression levels of IRE1α and p-PERK to initiate ER stress in osteosarcoma cells, which were aggravated by co-treating cells with ZSTK474. Next, the promoting effects of ZSTK474-VSVΔ51 combined treatment on osteosarcoma cell death were abrogated by the ER-stress inhibitor 4-phenyl butyric acid (4-PBA), indicating that ZSTK474 enhanced the cytotoxic effects of VSVΔ51 on osteosarcoma cells in an ER-stress dependent manner. Finally, the xenograft tumor-bearing mice models were established, and the results showed that ZSTK474-VSVΔ51 combined treatment synergistically hindered tumorigenesis of osteosarcoma cells in vivo. Taken together, our data suggested that ZSTK474 was a novel agent to enhance the cytotoxic effects of VSVΔ51 on osteosarcoma by aggravating ER-stress, and the present study might provide alternative therapy treatments for osteosarcoma in clinic.

Acquired chemoresistance can lead to increased resistance of pancreatic cancer cells to oncolytic vesicular stomatitis virus

Vesicular stomatitis virus (VSV) is a promising oncolytic virus (OV) against different malignancies, including pancreatic ductal adenocarcinoma (PDAC). Our previous studies have demonstrated that VSV-based OVs are effective against the majority of tested human PDAC cell lines. However, some PDAC cell lines are resistant to VSV. PDAC is one of the deadliest types of human malignancies in part due to intrinsic or acquired chemoresistance. Here, we investigated how acquired chemoresistance impacts the efficacy of VSV-based OV therapy. Using an experimental evolution approach, we generated PDAC cell lines with increased resistance to gemcitabine and examined their responsiveness to oncolytic virotherapy. We found that gemcitabine-resistant PDAC cells become more resistant to VSV. The cross-resistance correlated with upregulated levels of a subset of interferon-stimulated genes, resembling the interferon-related DNA damage resistance signature (IRDS), often associated with resistance of cancer cells to chemotherapy and/or radiation therapy. Analysis of ten different PDAC cell lines showed that four PDAC cell lines most resistant to VSV were also highly resistant to gemcitabine, and they all displayed IRDS-like expression in our previous reports. Our study highlights a possible interaction between two different therapies that should be considered in the future for the development of rational treatment regimens.

An Analysis of Virus Amplification and Antitumor Responses in T-Cell Lymphoma Patients Treated with Voyager-V1 ( VSV-IFNβ-NIS)

An Analysis of Virus Amplification and Antitumor Responses in T-Cell Lymphoma Patients Treated with Voyager-V1 ( VSV-IFNβ-NIS)

PI-D CONTROLLER BASED ON AN IMPROVED CROW SEARCH ALGORITHM FOR CANCER GROWTH TREATMENT

The number of cancer diagnoses and deaths worldwide is rising every year despite technological advancements in diagnosing and treating multiple forms of cancer. An oncolytic virus is a type of tumor-killing virus that can infect and analyze cancer cells while mostly preserving normal cells. The oncolytic Vesicular-Stomatitis Virus therapeutic's cell cycle-specific action mathematically investigated. An optimal Proportion Integral-Derivative (PI-D) controller is introduced in this paper based on a suggested Improved Crow Search Algorithm (ICSA) to enhance the outcome of oncolytic virotherapy. The control technique was tested in a computer using MATLAB simulation. The suggested ICSA is used to tune the parameters of the PI-D controller. The ICSA used the inertia factor and boundary handle mechanism in the position update equation to balance exploration and exploitation. The simulation results show that decrease in total dose, tumor cells to 30%, the tumor remain in the treatment area from day 30 onwards. Furthermore, the ICSA algorithm outperforms the CSA and PSO algorithms by 34.5497×10-6 and 15.2573 ×10-6, respectively, indicating the robustness of treatment methods that can accomplish tumor reduction through biological parameters ambiguity.

Antifibrotic Therapy Augments the Antitumor Effects of Vesicular Stomatitis Virus Via Reprogramming Tumor Microenvironment.

Solid tumors are characterized by abundant extracellular matrix originating from cancer-associated fibroblasts (CAFs). High collagen content can trigger the collapse of vascular system in the tumor and form physical barrier that eventually impedes the penetration of drug particles and cytotoxic immune cells. Moreover, CAFs is able to promote the enrichment of tumor-associated macrophages (TAMs) and differentiation of myeloid-derived suppressor cells (MDSCs) that work in concert to develop a highly immunosuppressive tumor microenvironment (TME). In this study, we investigated if halofuginone, an antifibrotic drug, can augment the therapeutic effects of oncolytic vesicular stomatitis virus (VSV). The results revealed that halofuginone significantly disrupts the collagen network in tumors and promotes the distribution of VSV and infiltration of CD8+ T cells (p < 0.0001). Combined treatment of VSV and halofuginone also modulates the immunosuppressive TME via deletion of TAM, MDSCs, and regulatory T cells (Tregs). Collectively, the combination therapy remarkably inhibits the tumor growth in multiple murine models and prolongs survival of mice. The results demonstrate the clinical potential of halofuginone in combination with oncolytic virus.

A modular self-adjuvanting cancer vaccine combined with an oncolytic vaccine induces potent antitumor immunity

Functional tumor-specific cytotoxic T cells elicited by therapeutic cancer vaccination in combination with oncolytic viruses offer opportunities to address resistance to checkpoint blockade therapy. Two cancer vaccines, the self-adjuvanting protein vaccine KISIMA, and the recombinant oncolytic vesicular stomatitis virus pseudotyped with LCMV-GP expressing tumor-associated antigens, termed VSV-GP-TAA, both show promise as a single agent. Here we find that, when given in a heterologous prime-boost regimen with an optimized schedule and route of administration, combining KISIMA and VSV-GP-TAA vaccinations induces better cancer immunity than individually. Using several mouse tumor models with varying degrees of susceptibility for viral replication, we find that priming with KISIMA-TAA followed by VSV-GP-TAA boost causes profound changes in the tumor microenvironment, and induces a large pool of poly-functional and persistent antigen-specific cytotoxic T cells in the periphery. Combining this heterologous vaccination with checkpoint blockade further improves therapeutic efficacy with long-term survival in the spectrum. Overall, heterologous vaccination with KISIMA and VSV-GP-TAA could sensitize non-inflamed tumors to checkpoint blockade therapy.

TCL-461: Clinical Activity of Systemic VSV-IFNβ-NIS Oncolytic Virotherapy in Patients with Relapsed Refractory Hematologic Malignancies

<h3>Context</h3> This is the first in human Phase 1 dose escalation trial of oncolytic Vesicular Stomatitis Virus (VSV) incorporating interferon beta and sodium iodine symporter transgenes (VSV-IFNβ-NIS) to be administered intravenously in patients with relapsed and refractory hematologic malignancies. <h3>Objective</h3> The primary objective was to determine the maximum tolerated dose of VSV-IFNβ-NIS as a single agent. The secondary objectives were to determine safety and efficacy of VSV-IFNβ-NIS. Correlative objectives included monitoring viremia and virus shedding. <h3>Design</h3> This was a 3+3 phase 1 clinical trial from April 2017 to August 2020 including adult patients (pts) with relapsed refractory multiple myeloma (MM), T-cell lymphoma (TCL), or acute myeloid leukemia (AML). <h3>Results</h3> Fifteen patients received VSV-IFNβ-NIS: MM (7), TCL (7), and AML (1); median age was 64 years, 60% male, and median prior lines of systemic cancer therapies was 5 (range, 2 to 11). Three patients were treated at each dose level (DL) 1 through 3 (respectively 0.05, 0.17, and 0.5 x 10¹¹ TCID₅₀), and 6 at DL 4 (1.7x10¹¹ TCID₅₀). There were no dose-limiting toxicities. Hematologic AEs, particularly lymphopenia (73%) were the predominant grade 3 and 4 AEs. Non-hematologic AE of interest were grade 1 (6.7%) and 2 (46.6%) cytokine release syndrome, of which only 1 patient required transient norepinephrine support. Objective responses were seen in patients with TCL. There was a 3-month partial response (PR) in a patient treated at DL 2 after 11 prior systemic therapies. However, compelling responses were seen at DL 4 with a deepening 6-month PR in a patient with PTCL and ongoing CR, even 14 months after VSV in another patient with cutaneous relapse of PTCL; both patients received 5 prior lines of therapy. Viremia rapidly declined after infusion, and there was no significant viral shedding. Neutralizing anti-VSV antibodies developed by day 29. IFNβ appeared to indicate intratumoral amplification with TCL patients mounting the highest levels. <h3>Conclusions</h3> A single intravenous dose of VSV-IFNβ-NIS up to 1.7x10¹¹ is safe in heavily pre-treated patients with hematologic malignancies and appears to be most effective as a single agent at DL 4, especially in patients with TCL. Future trials of combination strategies with immune-modulatory drugs are currently being planned. <h3>Grant Acknowledgements</h3> Mayo Clinic Multiple Myeloma Specialized Program of Research Excellence (SPORE), Grohne gifts, Phillips gift, and Liu gift.

Mechanisms that allow vaccination against an oncolytic vesicular stomatitis virus-encoded transgene to enhance safety without abrogating oncolysis

Vaccination can prevent viral infections via virus-specific T cells, among other mechanisms. A goal of oncolytic virotherapy is replication of oncolytic viruses (OVs) in tumors, so pre-existing T cell immunity against an OV-encoded transgene would seem counterproductive. We developed a treatment for melanomas by pre-vaccinating against an oncolytic vesicular stomatitis virus (VSV)-encoded tumor antigen. Surprisingly, when the VSV-vectored booster vaccine was administered at the peak of the primary effector T cell response, oncolysis was not abrogated. We sought to determine how oncolysis was retained during a robust T cell response against the VSV-encoded transgene product. A murine melanoma model was used to identify two mechanisms that enable this phenomenon. First, tumor-infiltrating T cells had reduced cytopathic potential due to immunosuppression. Second, virus-induced lymphopenia acutely removed virus-specific T cells from tumors. These mechanisms provide a window of opportunity for replication of oncolytic VSV and rationale for a paradigm change in oncolytic virotherapy, whereby immune responses could be intentionally induced against a VSV-encoded melanoma-associated antigen to improve safety without abrogating oncolysis.

Abstract 1747: Oncolytic Vesicular Stomatitis Virus expressing a species relevant interferon-beta is safe and provides a survival benefit when added as neoadjuvant to the standard of care for dogs with naturally occurring bone cancer

Abstract The goal of this study was to evaluate safety, efficacy, and immunological activity of Vesicular Stomatitis Virus (VSV) expressing a species relevant (canine) interferon-beta (IFN-β) and the sodium iodide symporter (NIS), henceforth called VSV, in companion dogs with naturally occurring appendicular osteosarcoma. The hypothesis was that VSV would track to the tumor, induce oncolysis, and lead to enhanced infiltration of immune cells, expansion of virus- and tumor specific T-cell clones, and improved survival outcomes.The first 15 dogs enrolled in the VSV Immunotherapy and Genomics of Osteosarcoma Research (VIGOR) study received a single iv dose of VSV (1x109 TCID50/kg) 10 days before amputation and adjuvant carboplatin chemotherapy. The final 13 dogs were randomized in a double-blinded fashion to receive either a single dose of VSV or placebo. Outcome data were compared to those from an historical control group of 57 dogs with appendicular osteosarcoma treated between 2006 and 2018 using the standard of care of alone. VSV treatment was associated with mild systemic effects (fever and inflammation), which were self-limiting and caused no symptomatology. Alterations in the tumor microenvironment (micronecrosis, increased fibrosis, and increased inflammation) were more common and more pronounced in VSV treated dogs than in placebo-treated dogs.Reduction in the expression of co-regulated cell cycle gene clusters in tumors after VSV-treatment was observed in dogs with longer survival. Conversely, increased expression of co-regulated immune/inflammatory gene clusters was observed in both VSV-treated dogs and in placebo-treated dogs, suggesting this might be, at least partly, due to the biopsy procedures. Assessment of changes in the clonal composition of T cells within the tumors, draining lymph nodes, and systemic circulation is in progress. No differences were evident in median event-free or overall survival times among the different groups, although aspects of the study design and sample size could obscure differences. Intriguingly, a “tail” of nine dogs (41%) that were long-term survivors (&amp;gt;450 days) was apparent in the VSV-treated group. All but one of these long-term survivors had evidence of inflammation in the pre-treatment tumor samples or showed increased inflammation in the post-treatment samples. We conclude that neoadjuvant VSV has an excellent safety profile and provides a survival benefit for a subset of dogs with spontaneous bone cancer. Ongoing work seeks to establish distinguishing characteristics that identify those individuals most likely to benefit from this therapy, as well as to evaluate the potential to enhance this benefit through the addition of novel immunomodulatory agents as part of our efforts to translate this approach to human cancer patients. Citation Format: Kelly M. Makielski, Aaron L. Sarver, Aishwarya Sathyanarayan, Michael S. Henson, Kathleen M. Stuebner, Alexandru-Flaviu Tabaran, Ingrid Cornax, Gerard O'Sullivan, Andrea Chehadeh, Donna Groschen, Kelly Bergsrud, Lauren J. Mills, Amber L. Winter, Sara Pracht, Milcah C. Scott, Michael A. Farrar, Gary R. Cutter, Joseph S. Koopmeiners, Stephen J. Russell, Shruthi Naik, Jaime F. Modiano. Oncolytic Vesicular Stomatitis Virus expressing a species relevant interferon-beta is safe and provides a survival benefit when added as neoadjuvant to the standard of care for dogs with naturally occurring bone cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1747.

Ruxolitinib Rescues Mice from Lethal Interferon Beta Toxicity and TLS

Introduction. Oncolytic Vesicular Stomatitis Virus expressing human interferon beta and the sodium iodide symporter reporter gene (VSV-hIFNβ-NIS) is in Phase 1 clinical testing for systemic administration in patients with relapsed multiple myeloma, acute myeloid leukemia and T cell lymphoma (NCT03017820). Local production of interferon β enhances virotherapy by activating the immune system, and restricts viral replication in normal cells by activating IFN induced antiviral responses. Thus, the virus propagates efficiently in IFN non-responsive cancer cells but is constrained in IFN responsive cells. Cancer cells that are defective in their viral sensing and IFN response pathways are exquisitely sensitive to VSV-IFNβ-NIS oncolysis, cumulating in tumor lysis syndrome and IFNβ induced toxicity in the MPC-11 mouse plasmacytoma model. Here, we evaluated the feasibility of using ruxolitinib, a clinically approved Jak1/2 inhibitor, to rescue mice from virotherapy induced TLS and IFNβ toxicity.Methods. To characterize IFNβ toxicity in the absence of TLS , varying levels of mIFNβ were achieved in the blood of mice by intramuscular injection of an AAV1 vector encoding mIFNβ. For the virotherapy-associated TLS and IFNβ toxicity model, Balb/c mice with subcutaneous MPC-11 murine plasmacytoma were given one intravenous administration of VSV-mIFNβ-NIS. To determine whether the Jak/STAT inhibitor ruxolitonib could impact IFNβ toxicity, mice were treated with ruxolitinib (2 mg/dose by oral gavage) given twice a day for 10 days. All mice were monitored for adverse clinical signs andtumor size. Plasma IFNβ levels, CBC and comprehensive clinical chemistry panels were analyzed at necropsy.Results. There was a dose dependent increase in plasma IFNβ levels with increasing doses of AAV1-mIFNβ given intramuscularly to mice. Adverse clinical signs were seen in mice given high doses of AAV1-mIFNβ. There was a good correlation between IFNβ and AST or ALT levels. High circulating levels of IFNβ resulted in elevation in transaminases, thrombocytopenia, anemia and lymphopenia. IFN receptor defective mice were completely resistant to these toxic effects even with blood levels of >80,000 pg/ml IFNβ. Nontumor bearing Balb/c mice were shown to tolerate high IV doses of VSV-mIFNβ-NIS with transient lymphopenia and transaminases. In Balb/c mice with IFN nonresponsive MPC-11 tumors that support robust viral replication, VSV-mIFNβ-NIS therapy was highly effective for tumor control, but resulted in TLS and IFNβ toxicity, requiring early euthanasia of mice. Mice given VSV and a neutralizing anti-IFNR antibody did not show any adverse clinical signs due to IFNβ toxicity but control of tumor growth was significantly impaired in comparison to virus treatment alone. In contrast combination treatment of mice VSV and ruxolitinib resulted in reversal of lethal IFNβ toxicity without loss of effective tumor control.Conclusions. Our data demonstrate that ruxolitinib reverses the toxicity of IFNβ seen following highly efficacious VSV-IFNβ-NIS virotherapy in the MPC-11 plasmacytoma model. Clinical evaluation of this promising combination is warranted. [Display omitted] DisclosuresPeng:Vyriad: Equity Ownership; Imanis Life Sciences: Employment, Equity Ownership. Russell:Vyriad: Equity Ownership; Imanis Life Sciences: Equity Ownership.

Oncolytic virotherapy induced CSDE1 neo-antigenesis restricts VSV replication but can be targeted by immunotherapy

In our clinical trials of oncolytic vesicular stomatitis virus expressing interferon beta (VSV-IFNβ), several patients achieved initial responses followed by aggressive relapse. We show here that VSV-IFNβ-escape tumors predictably express a point-mutated CSDE1P5S form of the RNA-binding Cold Shock Domain-containing E1 protein, which promotes escape as an inhibitor of VSV replication by disrupting viral transcription. Given time, VSV-IFNβ evolves a compensatory mutation in the P/M Inter-Genic Region which rescues replication in CSDE1P5S cells. These data show that CSDE1 is a major cellular co-factor for VSV replication. However, CSDE1P5S also generates a neo-epitope recognized by non-tolerized T cells. We exploit this predictable neo-antigenesis to drive, and trap, tumors into an escape phenotype, which can be ambushed by vaccination against CSDE1P5S, preventing tumor escape. Combining frontline therapy with escape-targeting immunotherapy will be applicable across multiple therapies which drive tumor mutation/evolution and simultaneously generate novel, targetable immunopeptidomes associated with acquired treatment resistance.

Natural killer T cell immunotherapy combined with oncolytic vesicular stomatitis virus or reovirus treatments differentially increases survival in mouse models of ovarian and breast cancer metastasis

BackgroundOncolytic viruses reduce tumor burden in animal models and have generated promising results in clinical trials. However, it is likely that oncolytic viruses will be more effective when used in...

In silico trials predict that combination strategies for enhancing vesicular stomatitis oncolytic virus are determined by tumor aggressivity

BackgroundImmunotherapies, driven by immune-mediated antitumorigenicity, offer the potential for significant improvements to the treatment of multiple cancer types. Identifying therapeutic strategies that bolster antitumor immunity while limiting immune suppression is...

Experimental virus evolution in cancer cell monolayers, spheroids, and tissue explants.

Viral laboratory evolution has been used for different applications, such as modeling viral emergence, drug-resistance prediction, and therapeutic virus optimization. However, these studies have been mainly performed in cell monolayers, a highly simplified environment, raising concerns about their applicability and relevance. To address this, we compared the evolution of a model virus in monolayers, spheroids, and tissue explants. We performed this analysis in the context of cancer virotherapy by performing serial transfers of an oncolytic vesicular stomatitis virus (VSV-Δ51) in 4T1 mouse mammary tumor cells. We found that VSV-Δ51 gained fitness in each of these three culture systems, and that adaptation to the more complex environments (spheroids or explants) correlated with increased fitness in monolayers. Most evolved lines improved their ability to suppress β-interferon secretion compared to the VSV-Δ51 founder, suggesting that the selective pressure exerted by antiviral innate immunity was important in the three systems. However, system-specific patterns were also found. First, viruses evolved in monolayers remained more oncoselective that those evolved in spheroids, since the latter showed concomitant adaptation to non-tumoral mouse cells. Second, deep sequencing indicated that viral populations evolved in monolayers or explants tended to be more genetically diverse than those evolved in spheroids. Finally, we found highly variable outcomes among independent evolutionary lines propagated in explants. We conclude that experimental evolution in monolayers tends to be more reproducible than in spheroids or explants, and better preserves oncoselectivity. Our results also suggest that monolayers capture at least some relevant selective pressures present in more complex systems.

Differential infection of murine and human dendritic cell subsets by oncolytic vesicular stomatitis virus variants

ABSTRACT Oncolytic viruses (OVs) can eradicate tumor cells and elicit antitumor immunity. VSV-GP, a chimeric vesicular stomatitis virus (VSV) with the glycoprotein (GP) of the lymphocytic choriomeningitis virus, is a promising new OV candidate. However, the interaction of VSV-GP with host immune cells is not fully understood. Dendritic cells (DCs) are essential for inducing efficient antitumor immunity. Thus, we aimed to investigate the interaction of VSV-GP with different murine and human DCs subsets in direct comparison to the less cytopathic variant VSV-dM51-GP and wild type VSV. Immature murine bone marrow-derived DCs (BMDCs) were equally infected and killed by VSV and VSV-GP. Human monocyte-derived DCs (moDCs) were more permissive to VSV. Interestingly, VSV-dM51-GP induced maturation instead of killing in both BMDCs and moDCs as well as a pronounced release of pro-inflammatory cytokines. Importantly, matured BMDCs and moDCs were no longer susceptible to VSV-GP infection. Mouse splenic conventional DC type 1 (cDC1) could be infected ex vivo by VSV and VSV-GP to a higher extent than cDC2. Systemic infection of mice with VSV-GP and VSV-dM51-GP resulted in strong activation of cDCs despite low infection rates in spleen and tumor tissue. Human blood cDC1 were equally infected by VSV and VSV-GP, whereas cDC2 showed preferential infection with VSV. Our study demonstrated differential DC infection, activation, and cytokine production after the treatment with VSV and VSV-GP variants among species and subsets, which should be taken into account when investigating immunological mechanisms of oncolytic virotherapy in mouse models and human clinical trials.

Development of an Oncolytic Recombinant Vesicular Stomatitis Virus Encoding a Tumor-suppressor MicroRNA.

Attempts have been made to enhance systemic therapy for osteosarcoma. In our previous study, the systemic administration of a vesicular stomatitis virus (VSV) improved the survival rates of mice with osteosarcoma but did not improve the long-term survival of the animals. In the present study, we developed a novel oncolytic VSV by incorporating tumor-suppressor microRNA143 (rVSV-miR143) to compare the antitumor effects of various doses (10×10-4, 5×10-4, and 1×10-4 multiplicity of infection) of rVSV-miR143 with those of VSV in vitro. The cytotoxicity and migration-inhibitory effects of rVSV-miR143 on the osteosarcoma cells were significantly higher than those of VSV alone at a dose of 5×10-4 multiplicity of infection, indicating that rVSV-miRNA143 enhances the antitumor effect at certain doses. VSV incorporating tumor-suppressor miRNA143 demonstrated a synergistic antitumor effect on osteosarcoma cells in vitro.