Intratumoral modulation of the inducible co-stimulator ICOS by recombinant oncolytic virus promotes systemic anti-tumour immunity

ICOS-expressing Regulatory T Cells Influence the Composition of Antitumor CTL Populations

The role of ICOS in antitumor T cell responses and overall tumor progression has been controversial. In this study, we compared tumor progression in mice lacking ICOS selectively in regulatory T (Treg) cells or in all T cells. Using an experimental melanoma lung metastasis model, we found that Treg cell-specific ICOS knockout reduces the overall tumor burden compared with Cre control mice, with increased CD4+-to-Treg cell and CD8+-to-Treg cell ratios in the tumor. In contrast, there was no difference in the tumor burden in mice lacking ICOS in all of the T cell compartments. This suggests a dual role of ICOS costimulation in promoting protumor and antitumor T cell responses. Consistent with reduced tumor burden, we found that Treg cell-specific deletion of ICOS leads to an increase of CD8+ CTLs that express high levels of granzyme B and perforin. Moreover, single-cell transcriptome analysis revealed an increase of Ly108+Eomeshi CD8+ T cells at the cost of the Ly108+T-bethi subset in Treg cell-specific knockout mice. These results suggest that ICOS-expressing Treg cells suppress the CTL maturation process at the level of Eomes upregulation, a critical step known to drive perforin expression and cytotoxicity. Collectively, our data imply that cancer immunotherapies using ICOS agonist Abs may work better in Treg cell-low tumors or when they are combined with regimens that deplete tumor-infiltrating Treg cells.

A review exploring the fusion of oncolytic viruses and cancer immunotherapy: An innovative strategy in the realm of cancer treatment

Oncolytic viruses (OVs) are increasingly recognized as potent tools in cancer therapy, effectively targeting and eradicating oncogenic conditions while sparing healthy cells. They enhance antitumor immunity by triggering various immune responses throughout the cancer cycle. Genetically engineered OVs swiftly destroy cancerous tissues and activate the immune system by releasing soluble antigens like danger signals and interferons. Their ability to stimulate both innate and adaptive immunity makes them particularly attractive in cancer immunotherapy. Recent advancements involve combining OVs with other immune therapies, yielding promising results. Transgenic OVs, designed to enhance immunostimulation and specifically target cancer cells, further improve immune responses. This review highlights the intrinsic mechanisms of OVs and underscores their synergistic potential with other immunotherapies. It also proposes strategies for optimizing armed OVs to bolster immunity against tumors.

An oncolytic virus delivering tumor-irrelevant bystander T cell epitopes induces anti-tumor immunity and potentiates cancer immunotherapy

Tumor-specific T cells are crucial in anti-tumor immunity and act as targets for cancer immunotherapies. However, these cells are numerically scarce and functionally exhausted in the tumor microenvironment (TME), leading to inefficacious immunotherapies in most patients with cancer. By contrast, emerging evidence suggested that tumor-irrelevant bystander T (TBYS) cells are abundant and preserve functional memory properties in the TME. To leverage TBYS cells in the TME to eliminate tumor cells, we engineered oncolytic virus (OV) encoding TBYS epitopes (OV-BYTE) to redirect the antigen specificity of tumor cells to pre-existing TBYS cells, leading to effective tumor inhibition in multiple preclinical models. Mechanistically, OV-BYTE induced epitope spreading of tumor antigens to elicit more diverse tumor-specific T cell responses. Remarkably, the OV-BYTE strategy targeting human severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T cell memory efficiently inhibited tumor progression in a human tumor cell-derived xenograft model, providing important insights into the improvement of cancer immunotherapies in a large population with a history of SARS-CoV-2 infection or coronavirus disease 2019 (COVID-19) vaccination.

Integrating system biology and intratumor gene therapy by trans-complementing the appropriate co-stimulatory molecule as payload in oncolytic herpes virus

Systems biology has been applied at the multi-scale level within the cancer field, improving cancer prevention, diagnosis and enabling precision medicine approaches. While systems biology can expand the knowledge and skills for oncological treatment, it also represents a challenging expedition due to cancer complexity, heterogeneity and diversity not only between different cancer indications, but also in its evolution process through space and time. Here, by characterizing the transcriptional perturbations of the tumor microenvironment induced by oncolytic, we aimed to rationally design a novel armed oncolytic herpes virus. We found that intratumor oncovirotherapy with HSV-1 induces T-cell activation signatures and transcriptionally activates several costimulatory molecules. We identified differentially expressed costimulatory receptors and binding partners, where inducible co-stimulators (ICOS) resulted in the potentially most beneficial targeted therapy. Through an ex-vivo transcriptomic analysis, we explored the potential of arming an oncolytic virus as a combination therapy strategy; in particular, we engineered a targeted herpes virus encoding ICOSL (THV_ICOSL), which resulted in a significant improvement in tumor size control compared to unarmed parental virus. Also, combination with a PD-1 inhibitor enhanced antitumor efficacy as predictable by upregulation of PD-1 and ligands pair (PD-L1/PD-L2) upon oncolytic virus injection. Generation of the human version of this virus encoding hICOSL orthologue effectively and specifically activated human T cells by triggering the ICOS pathway. Our data support the data-driven generation of armed oncolytic viruses as combination immunotherapeutic with checkpoint inhibitors.

Intranasal vaccination with an NDV-vectored SARS-CoV-2 vaccine protects against Delta and Omicron challenges

The rapid development and deployment of vaccines following the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been estimated to have saved millions of lives. Despite their immense success, there remains a need for next-generation vaccination approaches for SARS-CoV-2 and future emerging coronaviruses and other respiratory viruses. Here we utilized a Newcastle Disease virus (NDV) vectored vaccine expressing the ancestral SARS-CoV-2 spike protein in a pre-fusion stabilized chimeric conformation (NDV-PFS). When delivered intranasally, NDV-PFS protected both Syrian hamsters and K18 mice against Delta and Omicron SARS-CoV-2 variants of concern. Additionally, intranasal vaccination induced robust, durable protection that was extended to 6 months post-vaccination. Overall, our data provide evidence that NDV-vectored vaccines represent a viable next-generation mucosal vaccination approach.

Engineering approaches for innate immune-mediated tumor microenvironment remodeling

Cancer immunotherapy offers transformative promise particularly for the treatment of lethal cancers, since a correctly trained immune system can comprehensively orchestrate tumor clearance with no need for continued therapeutic intervention. Historically, the majority of immunotherapies have been T cell-focused and have included immune checkpoint inhibitors, chimeric antigen receptor T cells, and T-cell vaccines. Unfortunately T-cell-focused therapies have failed to achieve optimal efficacy in most solid tumors largely because of a highly immunosuppressed 'cold' or immune-excluded tumor microenvironment (TME). Recently, a rapidly growing treatment paradigm has emerged that focuses on activation of tumor-resident innate antigen-presenting cells, such as dendritic cells and macrophages, which can drive a proinflammatory immune response to remodel the TME from 'cold' or immune-excluded to 'hot'. Early strategies for TME remodeling centered on free cytokines and agonists, but these approaches have faced significant hurdles in both delivery and efficacy. Systemic toxicity from off-target inflammation is a paramount concern in these therapies. To address this critical gap, engineering approaches have provided the opportunity to add 'built-in' capabilities to cytokines, agonists, and other therapeutic agents to mediate improved delivery and efficacy. Such capabilities have included protective encapsulation to shield them from degradation, targeting to direct them with high specificity to tumors, and co-delivery strategies to harness synergistic proinflammatory pathways. Here, we review innate immune-mediated TME remodeling engineering approaches that focus on cytokines, innate immune agonists, immunogenic viruses, and cell-based methods, highlighting emerging preclinical approaches and strategies that are either being tested in clinical trials or already Food and Drug Administration approved.

Intratumoral Delivery of Interleukin 9 via Oncolytic Vaccinia Virus Elicits Potent Antitumor Effects in Tumor Models

The success of cancer immunotherapy is largely associated with immunologically hot tumors. Approaches that promote the infiltration of immune cells into tumor beds are urgently needed to transform cold tumors into hot tumors. Oncolytic viruses can transform the tumor microenvironment (TME), resulting in immunologically hot tumors. Cytokines are good candidates for arming oncolytic viruses to enhance their function in this transformation. Here, we used the oncolytic vaccinia virus (oVV) to deliver interleukin-9 (IL-9) into the tumor bed and explored its antitumor effects in colon and lung tumor models. Our data show that IL-9 prolongs viral persistence, which is probably mediated by the up-regulation of IL-10. The vvDD-IL-9 treatment elevated the expression of Th1 chemokines and antitumor factors such as IFN-γ, granzyme B, and perforin. IL-9 expression increased the percentages of CD4+ and CD8+ T cells in the TME and decreased the percentage of oVV-induced immune suppressive myeloid-derived suppressor cells (MDSC), leading to potent antitumor effects compared with parental virus treatment. The vvDD-IL-9 treatment also increased the percentage of regulatory T cells (Tregs) in the TME and elevated the expression of immune checkpoint molecules such as PD-1, PD-L1, and CTLA-4, but not GITR. The combination therapy of vvDD-IL-9 and the anti-CTLA-4 antibody, but not the anti-GITR antibody, induced systemic tumor-specific antitumor immunity and significantly extended the overall survival of mice, indicating a potential translation of the IL-9-expressing oncolytic virus into a clinical trial to enhance the antitumor effects elicited by an immune checkpoint blockade for cancer immunotherapy.

Exploration of the Delivery of Oncolytic Newcastle Disease Virus by Gelatin Methacryloyl Microneedles

Oncolytic Newcastle disease virus is a new type of cancer immunotherapy drug. This paper proposes a scheme for delivering oncolytic viruses using hydrogel microneedles. Gelatin methacryloyl (GelMA) was synthesized by chemical grafting, and GelMA microneedles encapsulating oncolytic Newcastle disease virus (NDV) were prepared by micro-molding and photocrosslinking. The release and expression of NDV were tested by immunofluorescence and hemagglutination experiments. The experiments proved that GelMA was successfully synthesized and had hydrogel characteristics. NDV was evenly dispersed in the allantoic fluid without agglomeration, showing a characteristic virus morphology. NDV particle size was 257.4 ± 1.4 nm, zeta potential was -13.8 ± 0.5 mV, virus titer TCID50 was 107.5/mL, and PFU was 2 × 107/mL, which had a selective killing effect on human liver cancer cells in a dose and time-dependent manner. The NDV@GelMA microneedles were arranged in an orderly cone array, with uniform height and complete needle shape. The distribution of virus-like particles was observed on the surface. GelMA microneedles could successfully penetrate 5% agarose gel and nude mouse skin. Optimal preparation conditions were freeze-drying. We successfully prepared GelMA hydrogel microneedles containing NDV, which could effectively encapsulate NDV but did not detect the release of NDV.

Epstein-Barr virus-encoded EBNA2 downregulates ICOSL by inducing miR-24 in B-cell lymphoma

ABSTRACT

Hematological malignancies such as Burkitt lymphoma (BL), Hodgkin lymphoma (HL), and diffuse large B-cell lymphoma (DLBCL) cause significant morbidity in humans. A substantial number of these lymphomas, particularly HL and DLBCLs have poorer prognosis because of their association with Epstein-Barr virus (EBV). Our earlier studies have shown that EBV-encoded nuclear antigen (EBNA2) upregulates programmed cell death ligand 1 in DLBCL and BLs by downregulating microRNA-34a. Here, we investigated whether EBNA2 affects the inducible costimulator (ICOS) ligand (ICOSL), a molecule required for efficient recognition of tumor cells by T cells through the engagement of ICOS on the latter. In virus-infected and EBNA2-transfected B-lymphoma cells, ICOSL expression was reduced. Our investigation of the molecular mechanisms revealed that this was due to an increase in microRNA-24 (miR-24) by EBNA2. By using ICOSL 3' untranslated region-luciferase reporter system, we validated that ICOSL is an authentic miR-24 target. Transfection of anti-miR-24 molecules in EBNA2-expressing lymphoma cells reconstituted ICOSL expression and increased tumor immunogenicity in mixed lymphocyte reactions. Because miR-24 is known to target c-MYC, an oncoprotein positively regulated by EBNA2, we analyzed its expression in anti-miR-24 transfected lymphoma cells. Indeed, the reduction of miR-24 in EBNA2-expressing DLBCL further elevated c-MYC and increased apoptosis. Consistent with the in vitro data, EBNA2-positive DLBCL biopsies expressed low ICOSL and high miR-24. We suggest that EBV evades host immune responses through EBNA2 by inducing miR-24 to reduce ICOSL expression, and for simultaneous rheostatic maintenance of proproliferative c-MYC levels. Overall, these data identify miR-24 as a potential therapeutically relevant target in EBV-associated lymphomas.

Recombinant Newcastle disease viruses expressing immunological checkpoint inhibitors induce a pro-inflammatory state and enhance tumor-specific immune responses in two murine models of cancer

Introduction

Tumor microenvironments are immunosuppressive due to progressive accumulation of mutations in cancer cells that can drive expression of a range of inhibitory ligands and cytokines, and recruitment of immunomodulatory cells, including myeloid-derived suppressor cells (MDSC), tumor-associated macrophages, and regulatory T cells (Tregs).

Methods

To reverse this immunosuppression, we engineered mesogenic Newcastle disease virus (NDV) to express immunological checkpoint inhibitors anti-cytotoxic T lymphocyte antigen-4 and soluble programmed death protein-1.

Results

Intratumoral administration of recombinant NDV (rNDV) to mice bearing intradermal B16-F10 melanomas or subcutaneous CT26LacZ colon carcinomas led to significant changes in the tumor-infiltrating lymphocyte profiles. Vectorizing immunological checkpoint inhibitors in NDV increased activation of intratumoral natural killer cells and cytotoxic T cells and decreased Tregs and MDSCs, suggesting induction of a pro-inflammatory state with greater infiltration of activated CD8+ T cells. These notable changes translated to higher ratios of activated effector/suppressor tumor-infiltrating lymphocytes in both cancer models, which is a promising prognostic marker. Whereas all rNDV-treated groups showed evidence of tumor regression and increased survival in the CT26LacZ and B16-F10, only treatment with NDV expressing immunological checkpoint blockades led to complete responses compared to tumors treated with NDV only.

Discussion

These data demonstrated that NDV expressing immunological checkpoint inhibitors could reverse the immunosuppressive state of tumor microenvironments and enhance tumor-specific T cell responses.

Oncolytic virotherapy in cancer treatment: challenges and optimization prospects

Oncolytic viruses (OVs) are emerging cancer therapeutics that offer a multifaceted therapeutic platform for the benefits of replicating and lysing tumor cells, being engineered to express transgenes, modulating the tumor microenvironment (TME), and having a tolerable safety profile that does not overlap with other cancer therapeutics. The mechanism of OVs combined with other antitumor agents is based on immune-mediated attack resistance and might benefit patients who fail to achieve durable responses after immune checkpoint inhibitor (ICI) treatment. In this Review, we summarize data on the OV mechanism and limitations of monotherapy, which are currently in the process of combination partner development, especially with ICIs. We discuss some of the hurdles that have limited the preclinical and clinical development of OVs. We also describe the available data and provide guidance for optimizing OVs in clinical practice, as well as a summary of approved and promising novel OVs with clinical indications.

Oncolytic Viruses in the Era of Omics, Computational Technologies, and Modeling: Thesis, Antithesis, and Synthesis

Oncolytic viruses (OVs) are the frontier therapy for refractory cancers, especially in integration with immunomodulation strategies. In cancer immunovirotherapy, the many available "omics" and systems biology technologies generate at a fast pace a challenging huge amount of data, where apparently clashing information mirrors the complexity of individual clinical situations and OV used. In this review, we present and discuss how currently big data analysis, on one hand and, on the other, simulation, modeling, and computational technologies, provide invaluable support to interpret and integrate "omic" information and drive novel synthetic biology and personalized OV engineering approaches for effective immunovirotherapy. Altogether, these tools, possibly aided in the future by artificial intelligence as well, will allow for the blending of the information into OV recombinants able to achieve tumor clearance in a patient-tailored way. Various endeavors to the envisioned "synthesis" of turning OVs into personalized theranostic agents are presented.

Harnessing the power of oncolytic virotherapy and tertiary lymphoid structures to amplify antitumor immune responses in cancer patients

Tertiary lymphoid structures (TLS) are ectopic aggregates of immune cells that develop in non-lymphoid tissues under persistent inflammation. Since their presence has been associated with a better prognosis in cancer patients, modulating TLS formation is being part of new challenges in immunotherapy. Although mechanisms underlying TLS genesis are still not fully understood, different strategies have been developed in preclinical models to induce their formation and ultimately enhance antitumor responses. Herein, we will discuss a new approach that would consist in using oncolytic viruses (OV). These viruses have the unique feature to preferentially infect, replicate in and kill cancer cells. Their immunoadjuvant property, their use as a vector of therapeutic molecules and their selectivity for cancer cells, make them an attractive strategy to induce TLS in the tumor microenvironment. This review will examine the current knowledge about TLS neogenesis, approaches for inducing them, and relevance of using OV for this purpose, especially in combination with immunotherapy such as immune checkpoint blockade.

The Viral Knock: Ameliorating Cancer Treatment with Oncolytic Newcastle Disease Virus

The prospect of cancer treatment has drastically transformed over the last four decades. The side effects caused by the traditional methods of cancer treatment like surgery, chemotherapy, and radiotherapy through the years highlight the prospect for a novel, complementary, and alternative cancer therapy. Oncolytic virotherapy is an evolving treatment modality that utilizes oncolytic viruses (OVs) to selectively attack cancer cells by direct lysis and can also elicit a strong anti-cancer immune response. Newcastle disease virus (NDV) provides a very high safety profile compared to other oncolytic viruses. Extensive research worldwide concentrates on experimenting with and better understanding the underlying mechanisms by which oncolytic NDV can be effectively applied to intercept cancer. This review encapsulates the potential of NDV to be explored as an oncolytic agent and discusses current preclinical and clinical research scenarios involving various NDV strains.

Oncolytic virotherapy evolved into the fourth generation as tumor immunotherapy

BACKGROUND

Oncolytic virotherapy (OVT) is a promising anti-tumor modality that utilizes oncolytic viruses (OVs) to preferentially attack cancers rather than normal tissues. With the understanding particularly in the characteristics of viruses and tumor cells, numerous innovative OVs have been engineered to conquer cancers, such as Talimogene Laherparepvec (T-VEC) and tasadenoturev (DNX-2401). However, the therapeutic safety and efficacy must be further optimized and balanced to ensure the superior safe and efficient OVT in clinics, and reasonable combination therapy strategies are also important challenges worthy to be explored.

MAIN BODY

Here we provided a critical review of the development history and status of OVT, emphasizing the mechanisms of enhancing both safety and efficacy. We propose that oncolytic virotherapy has evolved into the fourth generation as tumor immunotherapy. Particularly, to arouse T cells by designing OVs expressing bi-specific T cell activator (BiTA) is a promising strategy of killing two birds with one stone. Amazing combination of therapeutic strategies of OVs and immune cells confers immense potential for managing cancers. Moreover, the attractive preclinical OVT addressed recently, and the OVT in clinical trials were systematically reviewed.

CONCLUSION

OVs, which are advancing into clinical trials, are being envisioned as the frontier clinical anti-tumor agents coming soon.

Oncolytic virotherapy: basic principles, recent advances and future directions

Oncolytic viruses (OVs) have attracted growing awareness in the twenty-first century, as they are generally considered to have direct oncolysis and cancer immune effects. With the progress in genetic engineering technology, OVs have been adopted as versatile platforms for developing novel antitumor strategies, used alone or in combination with other therapies. Recent studies have yielded eye-catching results that delineate the promising clinical outcomes that OVs would bring about in the future. In this review, we summarized the basic principles of OVs in terms of their classifications, as well as the recent advances in OV-modification strategies based on their characteristics, biofunctions, and cancer hallmarks. Candidate OVs are expected to be designed as "qualified soldiers" first by improving target fidelity and safety, and then equipped with "cold weapons" for a proper cytocidal effect, "hot weapons" capable of activating cancer immunotherapy, or "auxiliary weapons" by harnessing tactics such as anti-angiogenesis, reversed metabolic reprogramming and decomposing extracellular matrix around tumors. Combinations with other cancer therapeutic agents have also been elaborated to show encouraging antitumor effects. Robust results from clinical trials using OV as a treatment congruously suggested its significance in future application directions and challenges in developing OVs as novel weapons for tactical decisions in cancer treatment.

Immune responses elicited by ssRNA(-) oncolytic viruses in the host and in the tumor microenvironment

Oncolytic viruses (OVs) are at the forefront of biologicals for cancer treatment. They represent a diverse landscape of naturally occurring viral strains and genetically modified viruses that, either as single agents or as part of combination therapies, are being evaluated in preclinical and clinical settings. As the field gains momentum, the research on OVs has been shifting efforts to expand our understanding of the complex interplay between the virus, the tumor and the immune system, with the aim of rationally designing more efficient therapeutic interventions. Nowadays, the potential of an OV platform is no longer defined exclusively by the targeted replication and cancer cell killing capacities of the virus, but by its contribution as an immunostimulator, triggering the transformation of the immunosuppressive tumor microenvironment (TME) into a place where innate and adaptive immunity players can efficiently engage and lead the development of tumor-specific long-term memory responses. Here we review the immune mechanisms and host responses induced by ssRNA(-) (negative-sense single-stranded RNA) viruses as OV platforms. We focus on two ssRNA(-) OV candidates: Newcastle disease virus (NDV), an avian paramyxovirus with one of the longest histories of utilization as an OV, and influenza A (IAV) virus, a well-characterized human pathogen with extraordinary immunostimulatory capacities that is steadily advancing as an OV candidate through the development of recombinant IAV attenuated platforms.

Systems Biology Approaches for the Improvement of Oncolytic Virus-Based Immunotherapies

Oncolytic virus (OV)-based immunotherapy is mainly dependent on establishing an efficient cell-mediated antitumor immunity. OV-mediated antitumor immunity elicits a renewed antitumor reactivity, stimulating a T-cell response against tumor-associated antigens (TAAs) and recruiting natural killer cells within the tumor microenvironment (TME). Despite the fact that OVs are unspecific cancer vaccine platforms, to further enhance antitumor immunity, it is crucial to identify the potentially immunogenic T-cell restricted TAAs, the main key orchestrators in evoking a specific and durable cytotoxic T-cell response. Today, innovative approaches derived from systems biology are exploited to improve target discovery in several types of cancer and to identify the MHC-I and II restricted peptide repertoire recognized by T-cells. Using specific computation pipelines, it is possible to select the best tumor peptide candidates that can be efficiently vectorized and delivered by numerous OV-based platforms, in order to reinforce anticancer immune responses. Beyond the identification of TAAs, system biology can also support the engineering of OVs with improved oncotropism to reduce toxicity and maintain a sufficient portion of the wild-type virus virulence. Finally, these technologies can also pave the way towards a more rational design of armed OVs where a transgene of interest can be delivered to TME to develop an intratumoral gene therapy to enhance specific immune stimuli.

Oncolyic Virotherapy for Prostate Cancer: Lighting a Fire in Winter

As the most common cancer of the genitourinary system, prostate cancer (PCa) is a global men's health problem whose treatments are an urgent research issue. Treatment options for PCa include active surveillance (AS), surgery, endocrine therapy, chemotherapy, radiation therapy, immunotherapy, etc. However, as the cancer progresses, the effectiveness of treatment options gradually decreases, especially in metastatic castration-resistant prostate cancer (mCRPC), for which there are fewer therapeutic options and which have a shorter survival period and worse prognosis. For this reason, oncolytic viral therapy (PV), with its exceptional properties of selective tumor killing, relatively good safety in humans, and potential for transgenic delivery, has attracted increasing attention as a new form of anti-tumor strategy for PCa. There is growing evidence that OV not only kills tumor cells directly by lysis but can also activate anticancer immunity by acting on the tumor microenvironment (TME), thereby preventing tumor growth. In fact, evidence of the efficacy of this strategy has been observed since the late 19th century. However, subsequently, interest waned. The renewed interest in this therapy was due to advances in biotechnological methods and innovations at the end of the 20th century, which was also the beginning of PCa therapy with OV. Moreover, in combination with chemotherapy, radiotherapy, gene therapy or immunotherapy, OV viruses can have a wide range of applications and can provide an effective therapeutic result in the treatment of PCa.

Improving cancer immunotherapy by rationally combining oncolytic virus with modulators targeting key signaling pathways

Oncolytic viruses (OVs) represent a new class of multi-modal immunotherapies for cancer, with OV-elicited antitumor immunity being key to their overall therapeutic efficacy. Currently, the clinical effectiveness of OV as monotherapy remains limited, and thus investigators have been exploring various combinations with other anti-cancer agents and demonstrated improved therapeutic efficacy. As cancer cells have evolved to alter key signaling pathways for enhanced cell proliferation, cancer progression and metastasis, these cellular and molecular changes offer promising targets for rational cancer therapy design. In this regard, key molecules in relevant signaling pathways for cancer cells or/and immune cells, such as EGFR-KRAS (e.g., KRAS^G12C), PI3K-AKT-mTOR, ERK-MEK, JAK-STAT, p53, PD-1-PD-L1, and epigenetic, or immune pathways (e.g., histone deacetylases, cGAS-STING) are currently under investigation and have the potential to synergize with OV to modulate the immune milieu of the tumor microenvironment (TME), thereby improving and sustaining antitumor immunity. As many small molecule modulators of these signaling pathways have been developed and have shown strong therapeutic potential, here we review key findings related to both OV-mediated immunotherapy and the utility of small molecule modulators of signaling pathways in immuno-oncology. Then, we focus on discussion of the rationales and potential strategies for combining OV with selected modulators targeting key cellular signaling pathways in cancer or/and immune cells to modulate the TME and enhance antitumor immunity and therapeutic efficacy. Finally, we provide perspectives and viewpoints on the application of novel experimental systems and technologies that can propel this exciting branch of medicine into a bright future.

Transcriptome profile and clinical characterization of ICOS expression in gliomas

Inducible co-stimulator (ICOS), an immune costimulatory molecule, has been found to play an essential role across various malignancies. This study investigated the transcriptome profile and clinical characterization of ICOS in gliomas. Clinical information and transcriptome data of 301 glioma samples were downloaded from the Chinese Glioma Genome Atlas (CGGA) dataset for analysis (CGGA301 cohort). Furthermore, the results were validated in 697 samples with RNAseq data from the TCGA glioma dataset and 325 gliomas with RNAseq data from the CGGA325 dataset. Immunohistochemistry was performed to evaluate ICOS protein expression across different WHO grades in a tissue microarray (TMA). In addition, single-cell sequencing data from CGGA and GSE 163108 datasets were used to analyze the ICOS expression across different cell types. Statistical analyses and figure production were performed with R-language. We found that ICOS was significantly upregulated in higher-grade, IDH wild type, and mesenchymal subtype of gliomas. Functional enrichment analyses revealed that ICOS was mainly involved in glioma-related immune response. Moreover, ICOS showed a robust correlation with other immune checkpoints, including the PD1/PD-L1/PD-L2 pathway, CTLA4, ICOSL (ICOS ligand), and IDO1. Subsequent Tumor Immune Dysfunction and Exclusion (TIDE) analysis revealed that GBM patients with higher ICOS expression seemed to be more sensitive to ICB therapy. Furthermore, based on seven clusters of metagenes, GSVA identified that ICOS was tightly associated with HCK, LCK, MHC-I, MHC-II, STAT1, and interferon, especially with LCK, suggesting a strong correlation between ICOS and T-cell activity in gliomas. In cell lineage analysis, Higher-ICOS gliomas tended to recruit dendritic cells, monocytes, and macrophages into the tumor microenvironment. Single-cell sequencing analysis indicated that ICOS was highly expressed by regulatory T cells (Tregs), especially in mature Tregs. Finally, patients with higher ICOS had shortened survival. ICOS was an independent prognosticator for glioma patients. In conclusion, higher ICOS is correlated with more malignancy of gliomas and is significantly associated with Treg activity among glioma-related immune responses. Moreover, ICOS could contribute as an independent prognostic factor for gliomas. Our study highlights the role of ICOS in glioma and may facilitate therapeutic strategies targeting ICOS for glioma.

Strategies for Advanced Oncolytic Virotherapy: Current Technology Innovations and Clinical Approaches

Oncolytic virotherapy is a type of nanomedicine with a dual antitumor mechanism. Viruses are engineered to selectively infect and lyse cancer cells directly, leading to the release of soluble antigens which induce systemic antitumor immunity. Representative drug Talimogene laherparepvec has showed promising therapeutic effects in advanced melanoma, especially when combined with immune checkpoint inhibitors with moderate adverse effects. Diverse viruses like herpes simplex virus, adenovirus, vaccina virus, and so on could be engineered as vectors to express different transgenic payloads, vastly expanding the therapeutic potential of oncolytic virotherapy. A number of related clinical trials are under way which are mainly focusing on solid tumors. Studies about further optimizing the genome of oncolytic viruses or improving the delivering system are in the hotspot, indicating the future development of oncolytic virotherapy in the clinic. This review introduces the latest progress in clinical trials and pre-clinical studies as well as technology innovations directed at oncolytic viruses. The challenges and perspectives of oncolytic virotherapy towards clinical application are also discussed.

Antitumor activity of recombinant oncolytic vaccinia virus with human IL2

The tumor microenvironment is highly immunosuppressive. The genetically modified oncolytic vaccinia virus (OVV) is a promising vector for cancer immunotherapy. The aim of the present study was to assess the antitumor effects of human interleukin-2 (hIL2)-armed OVV in vitro. The hIL2 gene was inserted into a thymidine kinase and the viral growth factor double deleted oncolytic VV (VVDD) to generate recombinant hIL2-armed OVV (rVVDD-hIL2). Viral replication capacity in A549 cells was quantified by plaque titration on CV-1 cells. Production of hIL2 in cancer cells infected by rVVDD-hIL2 was measured by enzyme-linked immunosorbent assay. Finally, 3-(4,5-dimethylthiazol-2-yl)-5-(3-arboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay was performed to assess the antitumor effects of rVVDD-hIL2. The results showed that rVVDD-hIL2 viral particles expressed increasing levels of hIL2 in human and murine cancer cell lines with growing multiplicities of infection (MOIs). The insertion of the hIL2 gene did not impair the replication capacity of VV, and the rVVDD-hIL2 virus killed cancer cells efficaciously. The lytic effects of the recombinant oncolytic virus on tumor cells increased with the growing MOIs. In conclusion, these findings suggest that hIL2-armed VVDD effectively infects and lyses tumor cells, with high expression of hIL2.

Reporter Transgenes for Monitoring the Antitumor Efficacy of Recombinant Oncolytic Viruses

Accurate measurement of tumor size and margins is crucial for successful oncotherapy. In the last decade, non-invasive imaging modalities, including optical imaging using non-radioactive substrates, deep-tissue imaging with radioactive substrates, and magnetic resonance imaging have been developed. Reporter genes play the most important role among visualization tools; their expression in tumors and metastases makes it possible to track changes in the tumor growth and gauge therapy effectiveness. Oncolytic viruses are often chosen as a vector for delivering reporter genes into tumor cells, since oncolytic viruses are tumor-specific, meaning that they infect and lyse tumor cells without damaging normal cells. The choice of reporter transgenes for genetic modification of oncolytic viruses depends on the study objectives and imaging methods used. Optical imaging techniques are suitable for in vitro studies and small animal models, while deep-tissue imaging techniques are used to evaluate virotherapy in large animals and humans. For optical imaging, transgenes of fluorescent proteins, luciferases, and tyrosinases are used; for deep-tissue imaging, the most promising transgene is the sodium/iodide symporter (NIS), which ensures an accumulation of radioactive isotopes in virus-infected tumor cells. Currently, NIS is the only reporter transgene that has been shown to be effective in monitoring tumor virotherapy not only in preclinical but also in clinical studies.

Avian Paramyxovirus 4 Antitumor Activity Leads to Complete Remissions and Long-term Protective Memory in Preclinical Melanoma and Colon Carcinoma Models

Avulaviruses represent a diverse subfamily of non-segmented negative strand RNA viruses infecting avian species worldwide. To date, 22 different serotypes have been identified in a variety of avian hosts, including wild and domestic birds. APMV-1, also known as Newcastle disease virus (NDV), is the only avulavirus that has been extensively characterized due to its relevance for the poultry industry and, more recently, its inherent oncolytic activity and potential as a cancer therapeutic. An array of both naturally-occurring and recombinant APMV-1 strains has been tested in different preclinical models and clinical trials, highlighting NDV as a promising viral agent for human cancer therapy. To date, the oncolytic potential of other closely related avulaviruses remains unknown. Here, we have examined the in vivo anti-tumor capability of prototype strains of APMV serotypes -2, -3, -4, -6, -7, -8 and -9 in syngeneic murine colon carcinoma and melanoma tumor models. Our studies have identified APMV-4 Duck/Hong Kong/D3/1975 virus as a novel oncolytic agent with greater therapeutic potential than one of the NDV clinical candidate strains, La Sota. Intratumoral administration of the naturally-occurring APMV-4 virus significantly extends survival, promotes complete remission, and confers protection against re-challenge in both murine colon carcinoma and melanoma tumor models. Furthermore, we have designed a plasmid rescue strategy that allows us to develop recombinant APMV-4-based viruses. The infectious clone rAPMV-4 preserves the extraordinary antitumor capacity of its natural counterpart, paving the way to a promising next generation of viral therapeutics.

Ferroptosis Inducer Improves the Efficacy of Oncolytic Virus-Mediated Cancer Immunotherapy

Ferroptosis is a type of programmed cell death dependent on iron and characterized by the accumulation of lipid peroxides. In this study, we explore the combination of a ferroptosis activator with an oncolytic vaccinia virus in tumor models. Erastin induced cell death in hepatoma, colon, and ovarian cancer cells, but not in melanoma cancer cells. Erastin, not the oncolytic vaccinia virus (OVV), induced the expression of key marker genes for ferroptosis in cancer cells. In hepatocellular carcinoma and colon cancer models, either erastin or OVV inhibited tumor growth, but a combination of the two yielded the best therapeutic effects, as indicated by inhibited tumor growth or regression and longer host survival. Immunological analyses indicate that erastin alone had little or no effect on systemic immunity or local immunity in the tumor. However, when combined with OV, erastin enhanced the number of activated dendritic cells and the activity of tumor-infiltrating T lymphocytes as indicated by an increase in IFN-γ⁺CD8⁺ and PD-1⁺CD8⁺ T cells. These results demonstrate that erastin can exert cytotoxicity on cancer cells via ferroptosis, but has little effect on immune activity by itself. However, when combined with an OVV, erastin promoted antitumoral immunity and efficacy by increasing the number of activated dendritic cells and promoting the activities of tumor specific CD8⁺ T cells in the tumor.

Oncolytic virus expressing PD-1 inhibitors activates a collaborative intratumoral immune response to control tumor and synergizes with CTLA-4 or TIM-3 blockade

BACKGROUND

Oncolytic viruses (OVs) are capable to inflame the tumor microenvironment (TME) and elicit infiltrating tumor-specific T cell responses. However, OV treatment negatively alters the cancer-immune set point in tumors to attenuate the antitumor immune response, which suggests the necessity of dissecting the immune landscape of the virus-treated tumors and developing novel strategies to maximize the potential of OVs. The aim of this study is to investigate the effect of the single-chain variable fragment (scFv)-armed OVs targeting PD-1 on the TME, and ultimately overcome localized immunosuppression to sensitize tumors to immunotherapies.

METHODS

A tumor-selective oncolytic herpes simplex virus vector was engineered to encode a humanized scFv against human PD-1 (hPD-1scFv) (YST-OVH). The antitumor efficacy of YST-OVH was explored in multiple therapeutic mouse models. The neurotoxicity and safety of YST-OVH were evaluated in nonhuman primates. The precise dynamics in the TME involved in YST-OVH treatment were dissected using cytometry by time-of-flight (CyTOF).

RESULTS

The identified hPD-1scFv showed superior T-cell activating activity. Localized delivery of hPD-1scFv by YST-OVH promotes systemic antitumor immunity in humanized PD-1 mouse models of established cancer. Immune profiling of tumors using CyTOF revealed the enhanced antitumor effect of YST-OVH, which largely relied on CD8+ T cell activity by augmenting the tumor infiltration of effector CD8+ T cells and establishment of memory CD8+ T cells and reducing associated CD8+ T cell exhaustion. Furthermore, YST-OVH treatment modified the cancer-immune set point of tumors coupled to coexpression of CTLA-4 and TIM-3 on exhausted CD8+ T cells and high levels of CTLA-4+ Treg cells. A combination approach incorporating anti-CTLA-4 or anti-TIM-3 further improved efficacy by increasing tumor immunogenicity and activating antitumor adaptive immune responses. Moreover, this therapeutic strategy showed no neurotoxicity and was well tolerated in nonhuman primates. The benefit of intratumoral hPD-1scFv expression was also observed in humanized mice bearing human cancer cells.

CONCLUSION

Localized delivery of PD-1 inhibitors by engineered YST-OVH was a highly effective and safe strategy for cancer immunotherapy. YST-OVH also synergized with CTLA-4 or TIM-3 blockade to enhance the immune response to cancer. These data provide a strong rationale for further clinical evaluation of this novel therapeutic approach.

Immunotherapy combining tumor and endothelium cell lysis with immune enforcement by recombinant MIP-3α Newcastle disease virus in a vessel-targeting liposome enhances antitumor immunity

Background

Several agents for oncolytic immunotherapy have been approved for clinical use, but monotherapy is modest for most oncolytic agents. The combination of several therapeutic strategies through recombinant and nanotechnology to engineer multifunctional oncolytic viruses for oncolytic immunotherapy is a promising strategy.

Methods

An endothelium-targeting iRGD-liposome encapsulating a recombinant Newcastle disease virus (NDV), which expresses the dendritic cell (DC) chemokine MIP-3α (iNDV3α-LP), and three control liposomes were constructed. MIP-3α, HMGB1, IgG, and ATP were detected by western blotting or ELISA. The chemotaxis of DCs was examined by Transwell chambers. The phenotypes of the immune cells were analyzed by flow cytometry. The antitumor efficiency was investigated in B16 and 4T1 tumor-bearing mice. Immunofluorescence and immunohistochemistry were used to observe the localization of liposomes, molecular expression and angiogenesis. Synergistic index was calculated using the data of tumor volume, tumor angiogenesis and tumor-infiltrating lymphocytes.

Results

Compared with NDV-LP, treatment with iNDV3α-LP and NDV3α-LP induced stronger virus replication and cell lysis in B16 and 4T1 tumor cells and human umbilical vein endothelial cells (HUVECs) with the best response observed following iNDV3α-LP treatment. B16 and 4T1 cells treated with iNDV3α-LP produced more damage-associated molecular pattern molecules, including secreted HMGB1, ATP, and calreticulin. Moreover, iNDV3α-LP specifically bound to αvβ3-expressing 4T1 cells and HUVECs and to tumor neovasculature. Tumor growth was significantly suppressed, and survival was longer in iNDV3α-LP-treated B16-bearing and 4T1-bearing mice. A mechanism study showed that iNDV3α-LP treatment initiated the strongest tumor-specific cellular and humoral immune response. Moreover, iNDV3α-LP treatment could significantly suppress tumor angiogenesis and reverse the tumor immune suppressive microenvironment in both B16-bearing and 4T1-bearing mice.

Conclusions

In this study, iNDV3α-LP had several functions, such as tumor and vessel lysis, MIP-3α immunotherapy, and binding to αvβ3-expressing tumor and its neovasculature. iNDV3α-LP treatment significantly suppressed tumor angiogenesis and reversed the tumor immunosuppressive microenvironment. These findings offer a strong rationale for further clinical investigation into a combination strategy for oncolytic immunotherapy, such as the formulation iNDV3α-LP in this study.

Engagement of the costimulatory molecule ICOS in tissues promotes establishment of CD8+ tissue-resident memory T cells

Elevated gene expression of the costimulatory receptor Icos is a hallmark of CD8⁺ tissue-resident memory (Trm) T cells. Here, we examined the contribution of ICOS in Trm cell differentiation. Upon transfer into WT mice, Icos^-/- CD8⁺ T cells exhibited defective Trm generation but produced recirculating memory populations normally. ICOS deficiency or ICOS-L blockade compromised establishment of CD8⁺ Trm cells but not their maintenance. ICOS ligation during CD8⁺ T cell priming did not determine Trm induction; rather, effector CD8⁺ T cells showed reduced Trm differentiation after seeding into Icosl^-/- mice. Icos^YF/YF CD8⁺ T cells were compromised in Trm generation, indicating a critical role for PI3K signaling. Modest transcriptional changes in the few Icos^-/- Trm cells suggest that ICOS-PI3K signaling primarily enhances the efficiency of CD8⁺ T cell tissue residency. Thus, local ICOS signaling promotes production of Trm cells, providing insight into the contribution of costimulatory signals in the generation of tissue-resident populations.

Immunotherapy of Cancer by Targeting Regulatory T cells

Regulatory T (Treg) cells maintain immune homeostasis by inhibiting abnormal/overactive immune responses to both autogenic and nonautogenic antigens. Treg cells play an important role in immune tolerance, autoimmune diseases, infectious diseases, organ transplantation, and tumor diseases. Treg cells have two functional characteristics: T cell anergy and immunosuppression. Treg cells remain immune unresponsive to high concentrations of interleukin-2 and anti-CD3 monoclonal antibodies. In addition, the activation of Treg cells after TCR-mediated signal stimulation inhibits the activation and proliferation of effector T cells. In the process of tumor development, Treg cells accumulate locally in the tumor and lead to tumor escape by inducing anergy and immunosuppression. It is believed that targeted elimination of Treg cells can activate tumor-specific effector T cells and improve the efficiency of cancer immunotherapy. Therefore, inhibition/clearance of Treg cells is a promising strategy for enhancing antitumor immunity. Here, we review studies of cancer immunotherapies targeting Treg cells.

Stereotactic body radiation combined with oncolytic vaccinia virus induces potent anti-tumor effect by triggering tumor cell necroptosis and DAMPs

Radiation is an integral part of cancer therapy. With the emergence of oncolytic vaccinia virus immunotherapy, it is important to study the combination of radiation and vaccinia virus in cancer therapy. In this study, we investigated the anti-tumor effect of and immune mechanisms underlying the combination of high-dose hypofractionated stereotactic body radiotherapy (SBRT) and oncolytic vaccinia virus in preclinical murine models. The combination enhanced the in vivo anti-tumor effect and increased the numbers of splenic CD4⁺Ki-67⁺ helper T lymphocytes and CD8⁺Ki-67⁺ cytotoxic T lymphocytes. Combinational therapy also increased tumor-infiltrating CD3⁺CD4⁺ helper T lymphocytes and CD3⁺CD8⁺ cytotoxic T lymphocytes, but decreased tumor-infiltrating regulatory T cells. In addition, SBRT combined with oncolytic vaccinia virus enhanced in vitro cell death, partly through necroptosis, and subsequent release of damage-associated molecular patterns (DAMPs), and shifted the macrophage M1/M2 ratio. We concluded that SBRT combined with oncolytic vaccinia virus can trigger tumor cell necroptosis and modify macrophages through the release of DAMPs, and then generate potent anti-tumor immunity and effects. Thus, combined therapy is potentially an important strategy for clinical cancer therapy.

Towards a Precision Medicine Approach and In Situ Vaccination against Prostate Cancer by PSMA-Retargeted oHSV

Prostate specific membrane antigen (PSMA) is a specific high frequency cell surface marker of prostate cancers. Theranostic approaches targeting PSMA show no major adverse effects and rule out off-tumor toxicity. A PSMA-retargeted oHSV (R-405) was generated which both infected and was cytotoxic exclusively for PSMA-positive cells, including human prostate cancer LNCaP and 22Rv1 cells, and spared PSMA-negative cells. R-405 in vivo efficacy against LLC1-PSMA and Renca-PSMA tumors consisted of inhibiting primary tumor growth, establishing long-term T immune response, immune heating of the microenvironment, de-repression of the anti-tumor immune phenotype, and sensitization to checkpoint blockade. The in situ vaccination protected from distant challenge tumors, both PSMA-positive and PSMA-negative, implying that it was addressed also to LLC1 tumor antigens. PSMA-retargeted oHSVs are a precision medicine tool worth being additionally investigated in the immunotherapeutic and in situ vaccination landscape against prostate cancers.

Current strategies in engaging oncolytic viruses with antitumor immunity

Oncolytic virotherapy has produced promising yet limited results in preclinical and clinical studies. Besides direct oncolytic activity, a significant therapeutic mechanism of oncolytic virotherapy is the induction of tumor-specific immunity. Consequently, the efficacy of oncolytic viruses can be improved by the insertion of immune stimulator genes and rational combinatorial therapy with other immunotherapies. This article reviews recent efforts on arming oncolytic viruses with a variety of immune stimulator molecules, immune cell engagers, and other immune potentiating molecules. We outline what is known about the mechanisms of action and the corresponding results. The review also discusses recent preclinical and clinical studies of combining oncolytic virotherapy with immune-checkpoint inhibitors and the role of oncolytic virotherapy in changing the tumor microenvironment.

A recombinant oncolytic Newcastle virus expressing MIP-3α promotes systemic antitumor immunity

BACKGROUND

The oncolytic Newcastle disease virus (NDV) is inherently able to trigger the lysis of tumor cells and induce the immunogenic cell death (ICD) of tumor cells and is also an excellent gene-engineering vector. The macrophage inflammatory protein-3α (MIP-3α) is a specific chemokine for dendritic cells (DCs). Thus, we constructed a recombinant NDV expressing MIP-3α (NDV-MIP3α) as an in vivo DC vaccine for amplifying antitumor immunities.

METHODS

The recombinant NDV-MIP3α was constructed by the insertion of MIP-3α cDNA between the P and M genes. Western blotting assay and ELISA were used to detect MIP-3α, HMGB1, IgG, and ATP in the supernatant and sera. The chemotaxis of DCs was examined by Transwell chambers. The phenotypes of the immune cells (eg, DCs) were analyzed by flow cytometry. The antitumor efficiency of NDV-MIP3α was observed in B16 and CT26 tumor-bearing mice. Immunofluorescence and immunohistochemistry were applied to observe the ecto-calreticulin (CRT) and intratumoral attraction of DCs. Adoptive transfer of splenocytes and antibodies and depletion of T-cell subsets were used to evaluate the relationship between antitumor immunities and the role of the T-cell subtype.

RESULTS

The findings show that NDV-MIP3α has almost the same capabilities of tumor lysis and induction of ICD as the wild-type NDV (NDV-WT). MIP-3α secreted by NDV-MIP3α could successfully attract DCs in vitro and in vivo. Both B16 and CT26 cells infected with NDV-MIP3α could strongly promote DC maturation and activation. Compared with NDV-WT, intratumoral injection of NDV-MIP3α and the adoptive transfer of T lymphocytes from mice injected with NDV-MIP3α resulted in a significant suppression of B16 and CT26 tumor growth. The NDV-MIP3α-induced production of tumor-specific cellular and humoral immune responses was dependent on CD8⁺ T cells and partially on CD4⁺ T cells. A significant reversion of tumor microenvironments was found in the mice injected with NDV-MIP3α.

CONCLUSIONS

Compared with NDV-WT, the recombinant NDV-MIP3α as an in vivo DC vaccine demonstrates enhanced antitumor activities through the induction of stronger system immunities and modulation of the tumor microenvironment. This strategy may be a potential approach for the generation of an in vivo DC vaccine.

Pouring petrol on the flames: Using oncolytic virotherapies to enhance tumour immunogenicity

Oncolytic viruses possess the ability to infect, replicate and lyse malignantly transformed tumour cells. This oncolytic activity amplifies the therapeutic advantage and induces a form of immunogenic cell death, characterized by increased CD8 + T-cell infiltration into the tumour microenvironment. This important feature of oncolytic viruses can result in the warming up of immunologically 'cold' tumour types, presenting the enticing possibility that oncolytic virus treatment combined with immunotherapies may enhance efficacy. In this review, we assess some of the most promising candidates that might be used for oncolytic virotherapy: immunotherapy combinations. We assess their potential as separate agents or as agents combined into a single therapy, where the immunotherapy is encoded within the genome of the oncolytic virus. The development of such advanced agents will require increasingly sophisticated model systems for their preclinical assessment and evaluation. In vivo rodent model systems are fraught with limitations in this regard. Oncolytic viruses replicate selectively within human cells and therefore require human xenografts in immune-deficient mice for their evaluation. However, the use of immune-deficient rodent models hinders the ability to study immune responses against any immunomodulatory transgenes engineered within the viral genome and expressed within the tumour microenvironment. There has therefore been a shift towards the use of more sophisticated ex vivo patient-derived model systems based on organoids and explant co-cultures with immune cells, which may be more predictive of efficacy than contrived and artificial animal models. We review the best of those model systems here.

Lentogenic NDV V protein inhibits IFN responses and represses cell apoptosis

The V protein of Newcastle disease virus (NDV) has been shown to inhibit the secretion of interferon (IFN) during infection, which is responsible for the promotion of NDV pathogenicity. However, the ability of the V protein to suppress host innate immunity is not well understood. In this study, we explored the function of V protein and its relationship with virulence by generating V protein-inserted recombinant (r) NDVs. Using rNDVs as a model, we examined the efficiency of infection, IFN responses, and apoptosis of host cells during infection. We found that viral propagation occurred smoothly when V protein from lentogenic NDV is inserted instead of the V protein from the velogenic strain. The infection of lentogenic V protein-inserted rNDV induced less expression of IFNs and downstream antiviral proteins via efficient degradation of p-STAT1 and MDA5. Moreover, velogenic V protein triggered a higher apoptosis rate during infection thereby restricting the replication of NDV. Conversely, lentogenic V protein inhibits IFN responses efficiently and induces less apoptosis compared to the velogenic strain. Our findings provide a novel understanding of the role of V protein in NDV pathogenicity.

Co-stimulatory agonists: An insight into the immunotherapy of cancer

Immune checkpoint pathways consist of stimulatory pathways, which can function like a strong impulse to promote T helper cells or killer CD8⁺ cells activation and proliferation. On the other hand, inhibitory pathways keep self-tolerance of the immune response. Increasing immunological activity by stimulating and blocking these signaling pathways are recognized as immune checkpoint therapies. Providing the best responses of CD8⁺ T cell needs the activation of T cell receptor along with the co-stimulation that is generated via stimulatory checkpoint pathways ligation including Inducible Co-Stimulator (ICOS), CD40, 4-1BB, GITR, and OX40. In cancer, programmed cell death receptor-1 (PD-1), Programmed cell death ligand-1(PD-L1) and Cytotoxic T Lymphocyte-Associated molecule-4 (CTLA-4) are the most known inhibitory checkpoint pathways, which can hinder the immune responses which have specifically anti-tumor characteristics and attenuate T cell activation and also cytokine production. The use of antagonistic monoclonal antibodies (mAbs) that block CTLA-4 or PD-1 activation is used in a variety of malignancies. It has been reported that they can lead to an increase in T cells and thereby strengthen anti-tumor immunity. Agonists of stimulatory checkpoint pathways can induce strong immunologic responses in metastatic patients; however, for achieving long-lasting benefits for the wide range of patients, efficient combinatorial therapies are required. In the present review, we focus on the preclinical and basic research on the molecular and cellular mechanisms by which immune checkpoint inhibitor blockade or other approaches with co-stimulatory agonists work together to improve T-cell antitumor immunity.

Intratumoral expression of interleukin 23 variants using oncolytic vaccinia virus elicit potent antitumor effects on multiple tumor models via tumor microenvironment modulation

Background: Newly emerging cancer immunotherapy has led to significant progress in cancer treatment; however, its efficacy is limited in solid tumors since the majority of them are “cold” tumors. Oncolytic viruses, especially when properly armed, can directly target tumor cells and indirectly modulate the tumor microenvironment (TME), resulting in “hot” tumors. These viruses can be applied as a cancer immunotherapy approach either alone or in combination with other cancer immunotherapies. Cytokines are good candidates to arm oncolytic viruses. IL-23, an IL-12 cytokine family member, plays many roles in cancer immunity. Here, we used oncolytic vaccinia viruses to deliver IL-23 variants into the tumor bed and explored their activity in cancer treatment on multiple tumor models.

Methods: Oncolytic vaccinia viruses expressing IL-23 variants were generated by homologue recombination. The characteristics of these viruses were in vitro evaluated by RT-qPCR, ELISA, flow cytometry and cytotoxicity assay. The antitumor effects of these viruses were evaluated on multiple tumor models in vivo and the mechanisms were investigated by RT-qPCR and flow cytometry.

Results: IL-23 prolonged viral persistence, probably mediated by up-regulated IL-10. The sustainable IL-23 expression and viral oncolysis elevated the expression of Th1 chemokines and antitumor factors such as IFN-γ, TNF-α, Perforin, IL-2, Granzyme B and activated T cells in the TME, transforming the TME to be more conducive to antitumor immunity. This leads to a systemic antitumor effect which is dependent on CD8⁺ and CD4⁺ T cells and IFN-γ. Oncolytic vaccinia viruses could not deliver stable IL-23A to the tumor, attributed to the elevated tristetraprolin which can destabilize the IL-23A mRNA after the viral treatment; whereas vaccinia viruses could deliver membrane-bound IL-23 to elicit a potent antitumor effect which might avoid the possible toxicity normally associated with systemic cytokine exposure.

Conclusion: Either secreted or membrane-bound IL-23-armed vaccinia virus can induce potent antitumor effects and IL-23 is a candidate cytokine to arm oncolytic viruses for cancer immunotherapy.

Combination Therapy of Novel Oncolytic Adenovirus with Anti-PD1 Resulted in Enhanced Anti-Cancer Effect in Syngeneic Immunocompetent Melanoma Mouse Model

Malignant melanoma, an aggressive form of skin cancer, has a low five-year survival rate in patients with advanced disease. Immunotherapy represents a promising approach to improve survival rates among patients at advanced stage. Herein, the aim of the study was to design and produce, by using engineering tools, a novel oncolytic adenovirus AdV-D24- inducible co-stimulator ligand (ICOSL)-CD40L expressing potent co-stimulatory molecules enhancing clinical efficacy through the modulation of anti-cancer immune responses. Firstly, we demonstrated the vector's identity and genetic stability by restriction enzyme assay and sequencing, then, by performing in vitro and in vivo pre-clinical studies we explored the anti-cancer efficacy of the virus alone or in combination with anti PD-1 inhibitor in human melanoma cell lines, i.e., MUG Mel-1 and MUG Mel-2, and in immunocompetent C57BL/6 melanoma B16V mouse model. We showed that both monotherapy and combination approaches exhibit enhanced anti-cancer ability and immunogenic cell death in in vitro settings. Furthermore, AdV-D24-ICOSL-CD40L combined with anti PD-1 revealed a fall in tumor volume and 100% survival in in vivo context, thus suggesting enhanced efficacy and survival via complementary anti-cancer properties of those agents in melanoma therapy. Collectively, the novel oncolytic vector AdV-D24-ICOSL-CD40L alone or in combination with anticancer drugs, such as check point inhibitors, may open novel therapeutic perspectives for the treatment of melanoma.

Belantamab mafodotin in combination with novel agents in relapsed/refractory multiple myeloma: DREAMM-5 study design

Belantamab mafodotin (belamaf) is a BCMA-targeted antibody-drug conjugate recently approved as monotherapy for adults with relapsed/refractory multiple myeloma who have received ≥4 prior therapies. Belamaf binds to BCMA and eliminates myeloma cells by multimodal mechanisms of action. The cytotoxic and potential immunomodulatory properties of belamaf have led to novel combination studies with other anticancer therapies. Here, we describe the rationale and design of DREAMM-5, an ongoing Phase I/II platform study evaluating the safety and efficacy of belamaf combined with novel agents, including GSK3174998 (OX40 agonist), feladilimab (an ICOS; GSK3359609), nirogacestat (a gamma-secretase inhibitor; PF-03084014) and dostarlimab (a PD-1 blocker) versus belamaf monotherapy for patients with relapsed/refractory multiple myeloma. Clinical trial registration: NCT04126200 (ClinicalTrials.gov).

IL-36γ-armed oncolytic virus exerts superior efficacy through induction of potent adaptive antitumor immunity

In this study, we aimed to apply the cytokine IL-36γ to cancer immunotherapy by constructing new oncolytic vaccinia viruses (OV) expressing interleukin-36γ (IL-36γ-OVs), leveraging unique synergism between OV and IL-36γ’s ability to promote antitumor adaptive immunity and modulate tumor microenvironment (TME). IL-36γ-OV had dramatic therapeutic efficacies in multiple murine tumor models, frequently leading to complete cancer eradication in large fractions of mice. Mechanistically, IL-36-γ-armed OV induced infiltration of lymphocytes and dendritic cells, decreased myeloid-derived suppressor cells and M2-like tumor-associated macrophages, and T cell differentiation into effector cells. Further study showed that IL-36γ-OV increased the number of tumor antigen-specific CD4⁺ and CD8⁺ T cells and the therapeutic efficacy depended on both CD8⁺ and CD4⁺ T cells. These results demonstrate that these IL36γ-armed OVs exert potent therapeutic efficacy mainly though antitumor immunity and they may hold great potential to advance treatment in human cancer patients.

Activity of tumor-associated macrophage depletion by CSF1R blockade is highly dependent on the tumor model and timing of treatment

Tumor-associated macrophages (TAMs) are abundant in solid tumors where they exhibit immunosuppressive and pro-tumorigenic functions. Inhibition of TAM proliferation and survival through CSF1R blockade has been widely explored as a cancer immunotherapy. To further define mechanisms regulating CSF1R-targeted therapies, we systematically evaluated the effect of anti-CSF1R treatment on tumor growth and tumor microenvironment (TME) inflammation across multiple murine models. Despite substantial macrophage depletion, anti-CSF1R had minimal effects on the anti-tumor immune response in mice bearing established tumors. In contrast, anti-CSF1R treatment concurrent with tumor implantation resulted in more robust tumor growth inhibition and evidence of enhanced anti-tumor immunity. Our findings suggest only minor contributions of CSF1R-dependent TAMs to the inflammatory state of the TME in established tumors, that immune landscape heterogeneity across different tumor models can influence anti-CSF1R activity, and that alternative treatment schedules and/or TAM depletion strategies may be needed to maximize the clinical benefit of this approach.

Combining vanadyl sulfate with Newcastle disease virus potentiates rapid innate immune-mediated regression with curative potential in murine cancer models

The avian paramyxovirus, Newcastle disease virus (NDV), is a promising oncolytic agent that has been shown to be safe and effective in a variety of pre-clinical cancer models and human clinical trials. NDV preferentially replicates in tumor cells due to signaling defects in apoptotic and antiviral pathways acquired during the transformation process and is a potent immunostimulatory agent. However, when used as a monotherapy NDV lacks the ability to consistently generate durable remissions. Here we investigate the use of viral sensitizer-mediated combination therapy to enhance the anti-neoplastic efficacy of NDV. Intratumoral injection of vanadyl sulfate, a pan-inhibitor of protein tyrosine phosphatases, in combination with NDV significantly increased the number and activation status of natural killer (NK) cells in the tumor microenvironment, concomitant with increased expression of interferon-β, granulocyte-macrophage colony-stimulating factor, and monocyte chemoattractant protein-1, leading to rapid tumor regression and long-term cures in mice bearing syngeneic B16-F10 melanomas. The anti-tumor efficacy of this combination therapy was abrogated when NK cells were depleted and when interferon-β expression was transiently suppressed. Tumor-specific CD8⁺ T cell responses were not detected, nor were mice whose tumors regressed protected from re-challenge. This suggested efficacy of the combination therapy predominantly relied on the innate immune system. Importantly, efficacy was not limited to melanoma; it was also demonstrated in a murine prostate cancer model. Taken together, these results suggest that combining NDV with vanadyl sulfate potentiates an innate immune response that can potentiate rapid clearance of tumors, with type I interferon signaling and NK cells being important mechanisms of action.

The discovery and development of oncolytic viruses: are they the future of cancer immunotherapy?

Introduction: Despite diverse treatment modalities and novel therapies, many cancers and patients are not effectively treated. Cancer immunotherapy has recently achieved breakthrough status yet is not effective in all cancer types or patients and can generate serious adverse effects. Oncolytic viruses (OVs) are a promising new therapeutic modality that harnesses virus biology and host interactions to treat cancer. OVs, genetically engineered or natural, preferentially replicate in and kill cancer cells, sparing normal cells/tissues, and mediating anti-tumor immunity.Areas covered: This review focuses on OVs as cancer therapeutic agents from a historical perspective, especially strategies to boost their immunotherapeutic activities. OVs offer a multifaceted platform, whose activities are modulated based on the parental virus and genetic alterations. In addition to direct viral effects, many OVs can be armed with therapeutic transgenes to also act as gene therapy vectors, and/or combined with other drugs or therapies.Expert opinion: OVs are an amazingly versatile and malleable class of cancer therapies. They tend to target cellular and host physiology as opposed to specific genetic alterations, which potentially enables broad responsiveness. The biological complexity of OVs have hindered their translation; however, the recent approval of talimogene laherparepvec (T-Vec) has invigorated the field.

New viral vectors for infectious diseases and cancer

Since the discovery in 1796 by Edward Jenner of vaccinia virus as a way to prevent and finally eradicate smallpox, the concept of using a virus to fight another virus has evolved into the current approaches of viral vectored genetic vaccines. In recent years, key improvements to the vaccinia virus leading to a safer version (Modified Vaccinia Ankara, MVA) and the discovery that some viruses can be used as carriers of heterologous genes encoding for pathological antigens of other infectious agents (the concept of 'viral vectors') has spurred a new wave of clinical research potentially providing for a solution for the long sought after vaccines against major diseases such as HIV, TB, RSV and Malaria, or emerging infectious diseases including those caused by filoviruses and coronaviruses. The unique ability of some of these viral vectors to stimulate the cellular arm of the immune response and, most importantly, T lymphocytes with cell killing activity, has also reawakened the interest toward developing therapeutic vaccines against chronic infectious diseases and cancer. To this end, existing vectors such as those based on Adenoviruses have been improved in immunogenicity and efficacy. Along the same line, new vectors that exploit viruses such as Vesicular Stomatitis Virus (VSV), Measles Virus (MV), Lymphocytic choriomeningitis virus (LCMV), cytomegalovirus (CMV), and Herpes Simplex Virus (HSV), have emerged. Furthermore, technological progress toward modifying their genome to render some of these vectors incompetent for replication has increased confidence toward their use in infant and elderly populations. Lastly, their production process being the same for every product has made viral vectored vaccines the technology of choice for rapid development of vaccines against emerging diseases and for 'personalised' cancer vaccines where there is an absolute need to reduce time to the patient from months to weeks or days. Here we review the recent developments in viral vector technologies, focusing on novel vectors based on primate derived Adenoviruses and Poxviruses, Rhabdoviruses, Paramixoviruses, Arenaviruses and Herpesviruses. We describe the rationale for, immunologic mechanisms involved in, and design of viral vectored gene vaccines under development and discuss the potential utility of these novel genetic vaccine approaches in eliciting protection against infectious diseases and cancer.

Newcastle Disease Virus at the Forefront of Cancer Immunotherapy

Preclinical and clinical studies dating back to the 1950s have demonstrated that Newcastle disease virus (NDV) has oncolytic properties and can potently stimulate antitumor immune responses. NDV selectively infects, replicates within, and lyses cancer cells by exploiting defective antiviral defenses in cancer cells. Inflammation within the tumor microenvironment in response to NDV leads to the recruitment of innate and adaptive immune effector cells, presentation of tumor antigens, and induction of immune checkpoints. In animal models, intratumoral injection of NDV results in T cell infiltration of both local and distant non-injected tumors, demonstrating the potential of NDV to activate systemic adaptive antitumor immunity. The combination of intratumoral NDV with systemic immune checkpoint blockade leads to regression of both injected and distant tumors, an effect further potentiated by introduction of immunomodulatory transgenes into the viral genome. Clinical trials with naturally occurring NDV administered intravenously demonstrated durable responses across numerous cancer types. Based on these studies, further exploration of NDV is warranted, and clinical studies using recombinant NDV in combination with immune checkpoint blockade have been initiated.

Oncolytic Viruses and Immune Checkpoint Inhibitors: Preclinical Developments to Clinical Trials

Immuno-oncology (IO) has been an active area of oncology research. Following US FDA approval of the first immune checkpoint inhibitor (ICI), ipilimumab (human IgG1 k anti-CTLA-4 monoclonal antibody), in 2011, and of the first oncolytic virus, Imlygic (talimogene laherparepvec), in 2015, there has been renewed interest in IO. In the past decade, ICIs have changed the treatment paradigm for many cancers by enabling better therapeutic control, resuming immune surveillance, suppressing tumor immunosuppression, and restoring antitumor immune function. However, ICI therapies are effective only in a small subset of patients and show limited therapeutic potential due to their inability to demonstrate efficacy in 'cold' or unresponsive tumor microenvironments (TMEs). Relatedly, oncolytic viruses (OVs) have been shown to induce antitumor immune responses, augment the efficacy of existing cancer treatments, and reform unresponsive TME to turn 'cold' tumors 'hot,' increasing their susceptibility to checkpoint blockade immunotherapies. For this reason, OVs serve as ideal complements to ICIs, and multiple preclinical studies and clinical trials are demonstrating their combined therapeutic efficacy. This review will discuss the merits and limitations of OVs and ICIs as monotherapy then progress onto the preclinical rationale and the results of clinical trials of key combination therapies.