Oncolytic viruses: overcoming translational challenges

Oncolytic viruses as cancer therapeutics: From mechanistic insights to clinical translation

Oncolytic virotherapy is a therapeutic approach that leverages genetically engineered or naturally occurring viruses to selectively target and destroy cancer cells while sparing normal tissues. This review provides an overview of the mechanisms of action by oncolytic viruses (OVs), including direct oncolysis, immune activation, and tumor microenvironment (TME) modulation. Despite significant progress, challenges such as immune resistance, tumor evasion mechanisms, and delivery barriers continue to limit the efficacy of OVs. To address these obstacles, recent advances in OV engineering have focused on arming viruses with immunomodulatory molecules, utilizing tumor-specific promoters, and employing CRISPR-based genome editing. Emerging strategies, such as dual-targeting OVs and viral enhancer drugs, have demonstrated promising potential in preclinical and clinical settings. This review also highlights findings from recent clinical trials, underscoring the translational challenges in scaling OVs for widespread therapeutic application. By exploring these innovations and their implications, we aim to shed light on the future directions of oncolytic virotherapy and its transformative potential in cancer treatment.

Oncolytic Virus Therapy in a New Era of Immunotherapy, Enhanced by Combination with Existing Anticancer Therapies: Turn up the Heat!

Oncolytic viral therapy is a promising treatment for cancer, where 'cold' tumour cells can become 'hot' to the host immune system. However, with few FDA approved therapies, development of new strategies for more cancer types has been slow and relatively unsuccessful in recent years, Combination therapy has been successful for other types of cancer treatment, therefore, may be a viable alternative to improve the efficacy of oncolytic viral therapy which may reduce some of the adverse events of currently used monotherapies, oncolytic virus therapy and chemotherapy being mutually complimentary with each other. Combining oncolytic viruses with immune checkpoint inhibitors provides a significant increase in efficacy when viral therapy was combined with the drug ipilimumab. Phase I and II studies concluded that combination with chemotherapies was safe and effective but did not significantly improve on current monotherapies. Recent experiments suggest that a combination of CAR-T and CAR--M cells is a promising therapeutic approach but needs to advance to clinical testing to observe the human response to the therapy. Viral combination with ipilimumab showed the highest potential for a successful treatment and clinical trials should be advanced to phase III to find conclusive supporting evidence. This review aims to identify and evaluate the potential of currently evolving oncolytic viral therapy with recent advances in genetic engineering providing enhanced oncolytic activity in the tumour, and addressing the lack of host immune responses in 'cold' tumours, with an additional role in enhancing conventional treatment efficacy with combination therapies. The potential of oncolytic viruses to 'turn up the heat' of a tumour microenvironment immunogenicity in combination with other anticancer treatments, provides a promising future for new cancer therapies.

Bioorthogonal oncolytic-virus nanovesicles combined bio-immunotherapy with CAR-T cells for solid tumors

Various oncolytic viruses (OVs) have been adopted as therapeutic tools to increase the efficacy of chimeric antigen receptor (CAR)-T cells against solid tumors. However, the therapeutic effect of OVs has been limited by pre-existing neutralizing antibodies and poor targeting delivery for systemic administration. Herein, we propose using bioorthogonal OV nanovesicles to boost the antitumor effects of CAR-T cells in solid tumors by reshaping the tumor microenvironment. Using a cell-membrane nanomimetic technique, we embedded artificial chemical ligands on cancer cell surfaces and then encapsulated lysoviral particles to obtain dual-targeted OV nanovesicles with bioorthogonal targeting and homologous recognition. OVs can be directly encapsulated into cancer cell nanovesicles and exhibit a liposome-like nanostructure, efficient loading, and excellent tumor-targeting capability. Encouragingly, OV nanovesicles efficiently induced tumor-cell apoptosis while sparing normal tissues and cells, thereby inhibiting tumor growth. Administration of viral nanovesicles effectively increased the secretion of anti-tumor cytokines such as IL-2, TNF-α and IFN-γ, and significantly promoted the infiltration and activation of CD8+CAR-T cells in tumors. Our data suggest that bioorthogonal OV nanovesicles hold great potential to overcome the limitations of CAR-T cells as monotherapies against solid tumors and, thus, drive the clinical application of combination therapy.

Neutrophils in oncolytic virus immunotherapy

Oncolytic viruses have emerged as a highly promising modality for cancer treatment due to their ability to replicate specifically within tumors, carry therapeutic genes, and modulate the immunosuppressive tumor microenvironment through various mechanisms. Additionally, they show potential synergy with immune checkpoint inhibitors. A study report indicates that from 2000 to 2020, 49.5% of oncolytic viruses were administered intratumorally and 35% intravenously during clinical trials. However, both administration methods face significant challenges, particularly with intravenous delivery, which encounters issues such as non-specific tissue uptake, neutralizing antibody responses, and antiviral effects mediated by various immune cells. Despite extensive research into the antiviral roles of CD8+ T cells and NK cells in oncolytic virus therapy, neutrophils-constituting approximately 50% to 70% of human peripheral blood leukocytes-have received relatively little attention. Neutrophils are the most abundant leukocyte subset in peripheral circulation, known for their phagocytic activity. Beyond their traditional roles in bacterial and fungal infections, emerging literature suggests that neutrophils also play a critical role in the body's antiviral responses. Given the gaps in understanding the role of neutrophils in oncolytic virus therapy, this article reviews current literature on this topic. It aims to provide a theoretical foundation for developing oncolytic virus-based cancer therapies and enhancing their anti-tumor efficacy in future clinical treatments.

The Potential of Oncolytic Virotherapy in the Treatment of Head and Neck Cancer: A Comprehensive Review

Head and neck cancer (HNC) represents a challenging oncological entity with significant morbidity and mortality rates. Despite advances in conventional therapies, including surgery, chemotherapy, and radiation therapy, the overall survival rates for advanced HNC remain suboptimal. In recent years, the emerging field of oncolytic virotherapy has gained attention as a promising therapeutic approach for various malignancies, including HNC. This review provides a comprehensive overview of the current understanding of oncolytic viruses (Ovs) in the context of HNC treatment, including their mechanisms of action, preclinical and clinical studies, challenges, and future directions. Future oncolytic virotherapy focuses on improving delivery and specificity through nanoparticle carriers and genetic modifications to enhance tumor targeting and immune response. Combining different OVs and integrating them with immunotherapies, such as checkpoint inhibitors, could overcome tumor resistance and improve outcomes. Personalized approaches and rigorous clinical trials are key to ensuring the safety and effectiveness of virotherapy in treating HNC.

Systemic delivery of tannic acid-ferric-masked oncolytic adenovirus reprograms tumor microenvironment for improved therapeutic efficacy in glioblastoma

Glioblastoma (GBM) represents the most aggressive primary brain tumor, and urgently requires effective treatments. Oncolytic adenovirus (OA) shows promise as a potential candidate for clinical antitumor therapy, including in the treatment of GBM. Nevertheless, the systemic delivery of OA continues to face challenges, leading to significantly compromised antitumor efficacy. In this study, we developed an innovative approach by encapsulating CXCL11-armed OA with tannic acid and Fe3+ (TA-Fe3+) to realize the systemic delivery of OA. The nanocarrier's ability to protect the OA from elimination by host immune response was evaluated in vitro and in vivo. We evaluated the antitumor effect and safety profile of OA@TA-Fe3+ in a GBM-bearing mice model. OA@TA-Fe3+ effectively safeguarded the virus from host immune clearance and extended its circulation in vivo. After targeting tumor sites, TA-Fe3+ could dissolve and release Fe3+ and OA. Fe3+-induced O2 production from H2O2 relieved the hypoxic state, and promoted OA replication, leading to a remarkable alteration of tumor immune microenvironment and enhancement in antitumor efficacy. Moreover, the systemic delivery of OA@TA-Fe3+ was safe without inflammation or organ damage. Our findings demonstrated the promising potential of systemically delivering the engineered OA for effective oncolytic virotherapy against GBM.

Engineered oncolytic virus expressing B7H3-targeting BiTE enhances antitumor T-cell immune response

BACKGROUND

Bispecific T-cell engagers (BiTEs) are recombinant bispecific proteins designed to stimulate polyclonal T-cell immunity. In recent years, B7H3, a pan-cancer antigen, has been considered a promising target for future immunotherapy. However, the B7H3-targeting BiTE faces the challenge of systemic toxicity. Oncolytic viruses (OVs) represent a new class of cancer immunotherapeutics and serve as an appropriate platform for locoregional delivery of therapeutic genes. In this study, we designed an oncolytic adenovirus (OAd) encoding BiTE targeting human B7H3. We hypothesized that OVs encoding B7H3 BiTE deliver this molecule persistently to the tumor site while mediating polyclonal T-cell activation and redirecting it to tumor cells.

METHODS

B7H3-targeting BiTE was constructed by linking a single-chain variable fragment (scFv) that recognizes human B7H3 to an scFv that recognizes human CD3. B7H3 BiTE was inserted into OAd to construct OAd-B7H3-BiTE. The function of the OV-delivered B7H3 BiTE was detected via co-culturing B7H3+ target cells and peripheral blood mononuclear cells. A humanized immune system mouse model was used to evaluate the therapeutic effects in vivo.

RESULTS

B7H3 is highly expressed in a high proportion of human malignancies. OV-delivered BiTEs bind to T cells and target cells. We observed a series of phenomena reflecting T-cell activation induced by OAd-B7H3-BiTE, including cell clustering, cell size, activation markers, cytokine secretion, and proliferation. Furthermore, T-cell activation was mirrored by the corresponding cytotoxicity against B7H3+ tumor cells. In vivo, B7H3 BiTE was persistently expressed in tumors and enhanced the antitumor T-cell immune response.

CONCLUSIONS

Using an OV for the local expression of B7H3 BiTE maximizes the local concentration of BiTE while reducing systemic exposure. OV also provides a relatively "hot" T-cell immune environment for the function of BiTE. Because of its capacity to activate polyclonal T cells, BiTE has the potential to redirect virus-specific T cells to tumors. Our study provides new opportunities for the exploitation of B7H3-BiTE-armed OVs as therapeutic agents for the treatment of B7H3-positive malignancies.

Oncolytic Viruses as Reliable Adjuvants in CAR-T Cell Therapy for Solid Tumors

Although impactful scientific advancements have recently been made in cancer therapy, there remains an opportunity for future improvements. Immunotherapy is perhaps one of the most cutting-edge categories of therapies demonstrating potential in the clinical setting. Genetically engineered T cells express chimeric antigen receptors (CARs), which can detect signals expressed by the molecules present on the surface of cancer cells, also called tumor-associated antigens (TAAs). Their effectiveness has been extensively demonstrated in hematological cancers; therefore, these results can establish the groundwork for their applications on a wide range of requirements. However, the application of CAR-T cell technology for solid tumors has several challenges, such as the existence of an immune-suppressing tumor microenvironment and/or inadequate tumor infiltration. Consequently, combining therapies such as CAR-T cell technology with other approaches has been proposed. The effectiveness of combining CAR-T cell with oncolytic virus therapy, with either genetically altered or naturally occurring viruses, to target tumor cells is currently under investigation, with several clinical trials being conducted. This narrative review summarizes the current advancements, opportunities, benefits, and limitations in using each therapy alone and their combination. The use of oncolytic viruses offers an opportunity to address the existing challenges of CAR-T cell therapy, which appear in the process of trying to overcome solid tumors, through the combination of their strengths. Additionally, utilizing oncolytic viruses allows researchers to modify the virus, thus enabling the targeted delivery of specific therapeutic agents within the tumor environment. This, in turn, can potentially enhance the cytotoxic effect and therapeutic potential of CAR-T cell technology on solid malignancies, with impactful results in the clinical setting.

Nanomaterial combined engineered bacteria for intelligent tumor immunotherapy

Cancer remains the leading cause of human death worldwide. Compared to traditional therapies, tumor immunotherapy has received a lot of attention and research focus due to its potential to activate both innate and adaptive immunity, low toxicity to normal tissue, and long-term immune activity. However, its clinical effectiveness and large-scale application are limited due to the immunosuppression microenvironment, lack of spatiotemporal control, expensive cost, and long manufacturing time. Recently, nanomaterial combined engineered bacteria have emerged as a promising solution to the challenges of tumor immunotherapy, which offers spatiotemporal control, reversal of immunosuppression, and scalable production. Therefore, we summarize the latest research on nanomaterial-assisted engineered bacteria for precise tumor immunotherapies, including the cross-talk of nanomaterials and bacteria as well as their application in different immunotherapies. In addition, we further discuss the advantages and challenges of nanomaterial-engineered bacteria and their future prospects, inspiring more novel and intelligent tumor immunotherapy.

Immunopeptidomics in the cancer immunotherapy era

Cancer is the primary cause of death worldwide, and conventional treatments are painful, complicated, and have negative effects on healthy cells. However, cancer immunotherapy has emerged as a promising alternative. Principle of cancer immunotherapy is the re-activation of T-cell to combat the tumor that presents the peptide antigen on major histocompatibility complex (MHC). Those peptide antigens are identified with the set of omics technology, proteomics, genomics, and bioinformatics, which referred to immunopeptidomics. Indeed, immunopeptidomics can identify the neoantigens that are very useful for cancer immunotherapies. This review explored the use of immunopeptidomics for various immunotherapies, i.e., peptide-based vaccines, immune checkpoint inhibitors, oncolytic viruses, and chimeric antigen receptor T-cell. We also discussed how the diversity of neoantigens allows for the discovery of novel antigenic peptides while post-translationally modified peptides diversify the overall peptides binding to MHC or so-called MHC ligandome. The development of immunopeptidomics is keeping up-to-date and very active, particularly for clinical application. Immunopeptidomics is expected to be fast, accurate and reliable for the application for cancer immunotherapies.

The investigation of oncolytic viruses in the field of cancer therapy

Oncolytic viruses (OVs) have emerged as a potential strategy for tumor treatment due to their ability to selectively replicate in tumor cells, induce apoptosis, and stimulate immune responses. However, the therapeutic efficacy of single OVs is limited by the complexity and immunosuppressive nature of the tumor microenvironment (TME). To overcome these challenges, engineering OVs has become an important research direction. This review focuses on engineering methods and multi-modal combination therapies for OVs aimed at addressing delivery barriers, viral phagocytosis, and antiviral immunity in tumor therapy. The engineering approaches discussed include enhancing in vivo immune response, improving replication efficiency within the tumor cells, enhancing safety profiles, and improving targeting capabilities. In addition, this review describes the potential mechanisms of OVs combined with radiotherapy, chemotherapy, cell therapy and immune checkpoint inhibitors (ICIs), and summarizes the data of ongoing clinical trials. By continuously optimizing engineering strategies and combination therapy programs, we can achieve improved treatment outcomes and quality of life for cancer patients.

Systemic delivery of oncolytic herpes virus using CAR-T cells enhances targeting of antitumor immuno-virotherapy

Recent studies have indicated that combining oncolytic viruses with CAR-T cells in therapy has shown superior anti-tumor effects, representing a promising approach. Nonetheless, the localized delivery method of intratumoral injection poses challenges for treating metastatic tumors or distal tumors that are difficult to reach. To address this obstacle, we employed HSV-1-infected CAR-T cells, which systemically delivery HSV into solid tumors. The biological function of CAR-T cells remained intact after loading them with HSV for a period of three days. In both immunocompromised and immunocompetent GBM orthotopic mouse models, B7-H3 CAR-T cells effectively delivered HSV to tumor lesions, resulting in enhanced T-cell infiltration and significantly prolonged survival in mice. We also employed a bilateral subcutaneous tumor model and observed that the group receiving intratumoral virus injection exhibited a significant reduction in tumor volume on the injected side, while the group receiving intravenous infusion of CAR-T cells carrying HSV displayed suppressed tumor growth on both sides. Hence, CAR-THSV cells offer notable advantages in the systemic delivery of HSV to distant tumors. In conclusion, our findings emphasize the potential of CAR-T cells as carriers for HSV, presenting significant advantages for oncolytic virotherapy targeting distant tumors.

Emerging delivery strategy for oncolytic virotherapy

Oncolytic virotherapy represents a promising approach in cancer immunotherapy. The primary delivery method for oncolytic viruses (OVs) is intratumoral injection, which apparently limits their clinical application. For patients with advanced cancer with disseminated metastasis, systemic administration is considered the optimal approach. However, the direct delivery of naked viruses through intravenous injection presents challenges, including rapid clearance by the immune system, inadequate accumulation in tumors, and significant side effects. Consequently, the development of drug delivery strategies has led to the emergence of various bio-materials serving as viral vectors, thereby improving the anti-tumor efficacy of oncolytic virotherapy. This review provides an overview of innovative strategies for delivering OVs, with a focus on nanoparticle-based or cell-based delivery systems. Recent pre-clinical and clinical studies are examined to highlight the enhanced efficacy of systemic delivery using these novel platforms. In addition, prevalent challenges in current research are briefly discussed, and potential solutions are proposed.

Revisiting the standards of cancer detection and therapy alongside their comparison to modern methods

In accordance with the World Health Organization data, cancer remains at the forefront of fatal diseases. An upward trend in cancer incidence and mortality has been observed globally, emphasizing that efforts in developing detection and treatment methods should continue. The diagnostic path typically begins with learning the medical history of a patient; this is followed by basic blood tests and imaging tests to indicate where cancer may be located to schedule a needle biopsy. Prompt initiation of diagnosis is crucial since delayed cancer detection entails higher costs of treatment and hospitalization. Thus, there is a need for novel cancer detection methods such as liquid biopsy, elastography, synthetic biosensors, fluorescence imaging, and reflectance confocal microscopy. Conventional therapeutic methods, although still common in clinical practice, pose many limitations and are unsatisfactory. Nowadays, there is a dynamic advancement of clinical research and the development of more precise and effective methods such as oncolytic virotherapy, exosome-based therapy, nanotechnology, dendritic cells, chimeric antigen receptors, immune checkpoint inhibitors, natural product-based therapy, tumor-treating fields, and photodynamic therapy. The present paper compares available data on conventional and modern methods of cancer detection and therapy to facilitate an understanding of this rapidly advancing field and its future directions. As evidenced, modern methods are not without drawbacks; there is still a need to develop new detection strategies and therapeutic approaches to improve sensitivity, specificity, safety, and efficacy. Nevertheless, an appropriate route has been taken, as confirmed by the approval of some modern methods by the Food and Drug Administration.

Enhancing oncolytic virus efficiency with methionine and N-(3-aminoprolil)methacrylamide modified acrylamide cationic block polymer

Oncolytic virus ablation of tumor cells has the advantages of high tumor selectivity, strong immunogenicity, and low side effects. However, the recognition and clearance of oncolytic viruses by the immune system are the main factors limiting their anti-tumor efficiency. As a highly biosafe and highly modifiable oncolytic virus vector, acrylamide can improve the long-term circulation of oncolytic viruses. Still, it is limited in its uptake efficiency by tumor cells. Herein, we constructed an N-hydroxymethyl acrylamide-b-(N-3-aminopropyl methacrylamide)-b-DMC block copolymer (NMA-b-APMA-b-DMA, NAD) as an oncolytic virus carrier, which not only improves the long-term circulation of oncolytic viruses in the body but also shows excellent stability for loading an oncolytic virus. The data shows that there was no obvious difference in the transfection effect of the NAD/Ad complex with or without neutralizing antibodies in the medium, which meant that the cationic carrier mediated by NAD/Ad had good serum stability. Only 10 micrograms of NAD carrier are needed to load the oncolytic virus, which can increase the transfection efficiency by 50 times. Cell experiments and mouse animal experiments show that NAD vectors can significantly enhance the anti-tumor effect of oncolytic viruses. We hope that this work will promote the application of acrylamide as an oncolytic virus vector and provide new ideas for methods to modify acrylamide for biomedical applications.

Tumor-targeted delivery of copper-manganese biomineralized oncolytic adenovirus for colorectal cancer immunotherapy

Oncolytic viral therapy (OVT) is a novel anti-tumor immunotherapy approach, specifically replicating within tumor cells. Currently, oncolytic viruses are mainly administered by intratumoral injection. However, achieving good results for distant metastatic tumors is challenging. In this study, a multifunctional oncolytic adenovirus, OA@CuMnCs, was developed using bimetallic ions copper and manganese. These metal cations form a biomineralized coating on the virus's surface, reducing immune clearance. It is known that viruses upregulate the expression of PD-L1. Copper ions in OA@CuMnCs can decrease the PD-L1 expression of tumor cells, thereby promoting immune cell-related factor release. This process involves antigen presentation and the combination of immature dendritic cells, transforming them into mature dendritic cells. It changes "cold" tumors into "hot" tumors, further inducing immunogenic cell death. While oncolytic virus replication requires oxygen, manganese ions in OA@CuMnCs can react with endogenous hydrogen peroxide. This reaction produces oxygen, enhancing the virus's replication ability and the tumor lysis effect. Thus, this multifunctionally coated OA@CuMnCs demonstrates potent amplification in immunotherapy efficacy, and shows great potential for further clinical OVT. STATEMENT OF SIGNIFICANCE: Oncolytic virus therapy (OVs) is a new anti-tumor immunotherapy method that can specifically replicate in tumor cells. Although the oncolytic virus can achieve a therapeutic effect on some non-metastatic tumors through direct intratumoral injection, there are still three major defects in the treatment of metastatic tumors: immune response, hypoxia effect, and administration route. Various studies have shown that the immune response in vivo can be overcome by modifying or wrapping the surface protein of the oncolytic virus. In this paper, a multifunctional coating of copper and manganese was prepared by combining the advantages of copper and manganese ions. The coating has a simple preparation method and mild conditions, and can effectively enhance tumor immunotherapy.

TheraVision: Engineering platform technology for the development of oncolytic viruses based on herpes simplex virus type 1

Viruses are able to efficiently penetrate cells, multiply, and eventually kill infected cells, release tumor antigens, and activate the immune system. Therefore, viruses are highly attractive novel agents for cancer therapy. Clinical trials with first generations of oncolytic viruses (OVs) are very promising but show significant need for optimization. The aim of TheraVision was to establish a broadly applicable engineering platform technology for combinatorial oncolytic virus and immunotherapy. Through genetic engineering, an attenuated herpes simplex virus type 1 (HSV1) was generated that showed increased safety compared to the wild-type strain. To demonstrate the modularity and the facilitated generation of new OVs, two transgenes encoding retargeting as well as immunomodulating single-chain variable fragments (scFvs) were integrated into the platform vector. The resulting virus selectively infected epidermal growth factor receptor (EGFR)-expressing cells and produced a functional immune checkpoint inhibitor against programmed cell death protein 1 (PD-1). Thus, both viral-mediated oncolysis and immune-cell-mediated therapy were combined into a single viral vector. Safety and functionality of the armed OVs have been shown in novel preclinical models ranging from patient-derived organoids and tissue-engineered human in vitro 3D tumor models to complex humanized mouse models. Consequently, a novel and proprietary engineering platform vector based on HSV1 is available for the facilitated preclinical development of oncolytic virotherapy.

Stem Cells and Tumor-Killing Virus to Target Brain Tumor: In Pursuit to Bring a Potential Delivery Vehicle for the Central Nervous System Tumors

To target brain cancer, various therapeutic options are present to fight against cancer cells. But the existing therapies are not showing a proper curation of cancer patients. Henceforth, activating the immune cells and targeting oncogenes/proteins might be an emerging therapeutic approach to target and destroy malignant brain tumor. Stem cells (SCs) are considered potential immunomodulators that trigger the highly suppressed immune system in the tumor microenvironment. Also, engineered SCs can repress the aberrantly expressed oncoproteins that cause tumor cell proliferation and growth. SCs have an excellent migration capability to reach the infected site and support the regeneration of damaged blood vessels and tissues. Likewise, oncolytic virotherapy (OVT) is a promising novel therapeutic molecule in which genetically modified viruses can selectively replicate and destroy cancer cells without harming healthy cells. Same as SCs, oncolytic viruses (OVs) tend to stimulate the host's innate and adaptive immune response to battle against the advanced brain tumor. In clinical studies, various OVs have shown good immunogenic responses with a high safety profile and tolerability against cancer patients with reduced morbidity and mortality rate. SCs act as an attractive cargo for OVs which helps to influence the tumor site and destroy the tumor volume. SCs protect the OVs from systemic degradation and promote therapeutic efficacy against cancer cells. SCs carried OVs might be a potential therapeutic way to bring an effective treatment option for brain tumors.

Breaking the barriers in cancer care: The next generation of herpes simplex virus-based oncolytic immunotherapies for cancer treatment

Since the US Food and Drug Administration first approved talimogene laherparepvec for the treatment of melanoma in 2015, the field of oncolytic immunotherapy (OI) has rapidly evolved. There are numerous ongoing clinical studies assessing the clinical activity of OIs across a wide range of tumor types. Further understanding of the mechanisms underlying the anti-tumor immune response has led to the development of OIs with improved immune-mediated preclinical efficacy. In this review, we discuss the key approaches for developing the next generation of herpes simplex virus-based OIs. Modifications to the viral genome and incorporation of transgenes to promote safety, tumor-selective replication, and immune stimulation are reviewed. We also review the advantages and disadvantages of intratumoral versus intravenous administration, summarize clinical evidence supporting the use of OIs as a strategy to overcome resistance to immune checkpoint blockade, and consider emerging opportunities to improve OI efficacy in the combination setting.

Progress in oncolytic viruses modified with nanomaterials for intravenous application

In oncolytic virus (OV) therapy, a critical component of tumor immunotherapy, viruses selectively infect, replicate within, and eventually destroy tumor cells. Simultaneously, this therapy activates immune responses and mobilizes immune cells, thereby eliminating residual or distant cancer cells. However, because of OVs' high immunogenicity and immune clearance during circulation, their clinical applications are currently limited to intratumoral injections, and their use is severely restricted. In recent years, numerous studies have used nanomaterials to modify OVs to decrease virulence and increase safety for intravenous injection. The most commonly used nanomaterials for modifying OVs are liposomes, polymers, and albumin, because of their biosafety, practicability, and effectiveness. The aim of this review is to summarize progress in the use of these nanomaterials in preclinical experiments to modify OVs and to discuss the challenges encountered from basic research to clinical application.

Oncolytic myxoma virus is effective in murine models of triple negative breast cancer despite poor rates of infection

Oncolytic viruses are being heavily investigated as novel methods to treat cancers; however, predicting their therapeutic efficacy remains challenging. The most commonly used predictive tests involve determining the in vitro susceptibility of a tumor's malignant cells to infection with an oncolytic agent. Whether these tests are truly predictive of in vivo efficacy, however, remains unclear. Here we demonstrate that a recombinant, oncolytic myxoma virus shows efficacy in two murine models of triple negative breast cancer despite extremely low permissivity of these models to viral infection. These data demonstrate that in vitro infectivity studies are not an accurate surrogate for therapeutic efficacy and suggest that other tests need to be developed.

Oncolytic Virus Engineering and Utilizations: Cancer Immunotherapy Perspective

Oncolytic viruses have positively impacted cancer immunotherapy over the past 20 years. Both natural and genetically modified viruses have shown promising results in treating various cancers. Various regulatory authorities worldwide have approved four commercial oncolytic viruses, and more are being developed to overcome this limitation and obtain better anti-tumor responses in clinical trials at various stages. Faster advancements in translating research into the commercialization of cancer immunotherapy and a comprehensive understanding of the modification strategies will widen the current knowledge of future technologies related to the development of oncolytic viruses. In this review, we discuss the strategies of virus engineering and the progress of clinical trials to achieve virotherapeutics.

Navoximod modulates local HSV-1 replication to reshape tumor immune microenvironment for enhanced immunotherapy via an injectable hydrogel

Oncolytic virotherapy can lead to tumor lysis and systemic anti-tumor immunity, but the therapeutic potential in humans is limited due to the impaired virus replication and the insufficient ability to overcome the immunosuppressive tumor microenvironment (TME). To solve the above problems, we identified that Indoleamine 2, 3-dioxygenase 1 (IDO1) inhibitor Navoximod promoted herpes simplex virus type 1 (HSV-1) replication and HSV-1-mediated oncolysis in tumor cells, making it a promising combination modality with HSV-1-based virotherapy. Thus, we loaded HSV-1 and Navoximod together in an injectable and biocompatible hydrogel (V-Navo@gel) for hepatocellular carcinoma (HCC) virotherapy. The hydrogel formed a local delivery reservoir to maximize the viral replication and distribution at the tumor site with a single-dose injection. Notably, V-Navo@gel improved the disease-free survival time of HCC- bearing mice and protects the mice against tumor recurrence. What's more, V-Navo@gel also showed an effective therapeutic efficacy in the rabbit orthotopic liver cancer model. Mechanistically, we further discovered that our combination strategy entirely reprogramed the TME through single-cell RNA sequencing. All these results collectively indicated that the combination of Navoximod with HSV-1 could boost the viral replication and reshape TME for tumor eradication through the hydrogel reservoir.

Polycytidine tract deletion from microRNA-detargeted oncolytic Mengovirus optimizes the therapeutic index in a murine multiple myeloma model

Mengovirus is an oncolytic picornavirus whose broad host range allows for testing in immunocompetent cancer models. Two pathogenicity-ablating approaches, polycytidine (polyC) tract truncation and microRNA (miRNA) targets insertion, eliminated the risk of encephalomyocarditis. To investigate whether a polyC truncated, miRNA-detargeted oncolytic Mengovirus might be boosted, we partially or fully rebuilt the polyC tract into the 5' noncoding region (NCR) of polyC-deleted (MC0) oncolytic constructs (NC) carrying miRNA target (miRT) insertions to eliminate cardiac/muscular (miR-133b and miR-208a) and neuronal (miR-124) tropisms. PolyC-reconstituted viruses (MC24-NC and MC37-NC) replicated in vitro and showed the expected tropism restrictions, but reduced cytotoxicity and miRT deletions were frequently observed. In the MPC-11 immune competent mouse plasmacytoma model, both intratumoral and systemic administration of MC0-NC led to faster tumor responses than MC24-NC or MC37-NC, with combined durable complete response rates of 75%, 0.5%, and 30%, respectively. Secondary viremia was higher following MC0-NC versus MC24-NC or MC37-NC therapy. Sequence analysis of virus progeny from treated mice revealed a high prevalence of miRT sequences loss among MC24- and MC37- viral genomes, but not in MC0-NC. Overall, MC0-NC was capable of stably retaining miRT sites and provided a more effective treatment and is therefore our lead Mengovirus candidate for clinical translation.

The emerging field of oncolytic virus-based cancer immunotherapy

Oncolytic viruses (OVs) provide novel and promising therapeutic options for patients with cancers resistant to traditional therapies. Natural or genetically modified OVs are multifaceted tumor killers. They directly lyse tumor cells while sparing normal cells, and indirectly potentiate antitumor immunity by releasing antigens and activating inflammatory responses in the tumor microenvironment. However, some limitations, such as limited penetration of OVs into tumors, short persistence, and the host antiviral immune response, are impeding the broad translation of oncolytic virotherapy into the clinic. If these challenges can be overcome, combination therapies, such as OVs plus immune checkpoint blockade (ICB), chimeric antigen receptor (CAR) T cells, or CAR natural killer (NK) cells, may provide powerful therapeutic platforms in the clinic.

Harnessing Engineered Immune Cells and Bacteria as Drug Carriers for Cancer Immunotherapy

Immunotherapy continues to be in the spotlight of oncology therapy research in the past few years and has been proven to be a promising option to modulate one's innate and adaptive immune systems for cancer treatment. However, the poor delivery efficiency of immune agents, potential off-target toxicity, and nonimmunogenic tumors significantly limit its effectiveness and extensive application. Recently, emerging biomaterial-based drug carriers, including but not limited to immune cells and bacteria, are expected to be potential candidates to break the dilemma of immunotherapy, with their excellent natures of intrinsic tumor tropism and immunomodulatory activity. More than that, the tiny vesicles and physiological components derived from them have similar functions with their source cells due to the inheritance of various surface signal molecules and proteins. Herein, we presented representative examples about the latest advances of biomaterial-based delivery systems employed in cancer immunotherapy, including immune cells, bacteria, and their derivatives. Simultaneously, opportunities and challenges of immune cells and bacteria-based carriers are discussed to provide reference for their future application in cancer immunotherapy.

Transarterial viroembolization improves the therapeutic efficacy of immune-excluded liver cancer: Three birds with one stone

OBJECTIVE

To investigate the mechanism and efficacy of transarterial viroembolization (TAVE) with an oncolytic virus (OH2) for the treatment of liver cancer in rabbit VX2 tumor models.

MATERIALS AND METHODS

Subcutaneous tumor and liver cancer models were established to determine the optimal viral titer and administration modality of OH2. Different liver cancer models were established to evaluate the locoregional tumor response, synergistic and standby effects, survival benefit, and specific antitumor immune memory after TAVE treatment. The immune cell densities in tumor tissues were measured.

RESULTS

The optimal viral titer of OH2 was 1 × 10⁷ CCID₅₀. TAVE was the most effective modality with greater homogeneous OH2 distribution and therapeutic efficacy compared to other administration routes of transarterial virus infusion (TAVI), commonly adopted intratumor injection (TI), and intravenous injection (IV). Additionally, TAVE treatment significantly improved the locoregional tumor response, standby effect, and survival benefit compared to the TAVI, transarterial embolization (TAE), and control groups. TAVE modified the immune cell densities for immune-excluded liver cancer, partially destroyed vessel metastases, and established antitumor immune memory. The synergistic treatment efficacy of TAVE was superior to the simple addition of two independent monotherapies.

CONCLUSION

TAVE was the optimal and a safe modality for treating immune-excluded liver cancer, and its synergistic effect achieved a remarkable tumor response, standby effect, survival benefit, and antitumor immune memory, which providing an innovative therapeutic modality for clinical practice.

DATA AVAILABILITY

Data is available from the corresponding author upon requirement.

Oncolytic virus-based hepatocellular carcinoma treatment: Current status, intravenous delivery strategies, and emerging combination therapeutic solutions

Current treatments for advanced hepatocellular carcinoma (HCC) have limited success in improving patients' quality of life and prolonging life expectancy. The clinical need for more efficient and safe therapies has contributed to the exploration of emerging strategies. Recently, there has been increased interest in oncolytic viruses (OVs) as a therapeutic modality for HCC. OVs undergo selective replication in cancerous tissues and kill tumor cells. Strikingly, pexastimogene devacirepvec (Pexa-Vec) was granted an orphan drug status in HCC by the U.S. Food and Drug Administration (FDA) in 2013. Meanwhile, dozens of OVs are being tested in HCC-directed clinical and preclinical trials. In this review, the pathogenesis and current therapies of HCC are outlined. Next, we summarize multiple OVs as single therapeutic agents for the treatment of HCC, which have demonstrated certain efficacy and low toxicity. Emerging carrier cell-, bioengineered cell mimetic- or nonbiological vehicle-mediated OV intravenous delivery systems in HCC therapy are described. In addition, we highlight the combination treatments between oncolytic virotherapy and other modalities. Finally, the clinical challenges and prospects of OV-based biotherapy are discussed, with the aim of continuing to develop a fascinating approach in HCC patients.

A Genome-Wide CRISPR-Cas9 Loss-of-Function Screening to Identify Host Restriction Factors Modulating Oncolytic Virotherapy

Oncolytic virotherapy represents an efficient immunotherapeutic approach for cancer treatment. Oncolytic viruses (OVs) promote antitumor responses through tumor-selective cell lysis and immune system activation. However, some tumor cell lines and primary tumors display resistance to therapy. Here we describe a protocol to identify novel host factors responsible for tumor resistance to oncolysis using an unbiased genome-wide CRISPR-Cas9 loss-of-function screening. Cas9-expressing tumor cells are transduced with a library of pooled single-guide RNA (sgRNA)-expressing lentiviruses that target all human genes to obtain a cell population where each cell is knocked out for a single gene. Upon OV infection, resistant cells survive, while sensitive cells die. The relative abundance of each genome-integrated sgRNA is measured by next-generation sequencing (NGS) in resistant and control cells. This protocol is amenable to uncover host factors involved in the resistance to different OVs in multiple tumor models.

Development of Allogeneic Stem Cell-Based Platform for Delivery and Potentiation of Oncolytic Virotherapy

We describe the repurposing and optimization of the TK-positive (thymidine kinase) vaccinia virus strain ACAM1000/ACAM2000™ as an oncolytic virus. This virus strain has been widely used as a smallpox vaccine and was also used safely in our recent clinical trial in patients with advanced solid tumors and Acute Myeloid Leukemia (AML). The vaccinia virus was amplified in CV1 cells and named CAL1. CAL1 induced remarkable oncolysis in various human and mouse cancer cells and preferentially amplified in cancer cells, supporting the use of this strain as an oncolytic virus. However, the therapeutic potential of CAL1, as demonstrated with other oncolytic viruses, is severely restricted by the patients' immune system. Thus, to develop a clinically relevant oncolytic virotherapy agent, we generated a new off-the-shelf therapeutic called Supernova1 (SNV1) by loading CAL1 virus into allogeneic adipose-derived mesenchymal stem cells (AD-MSC). Culturing the CAL1-infected stem cells allows the expression of virally encoded proteins and viral amplification prior to cryopreservation. We found that the CAL1 virus loaded into AD-MSC was resistant to humoral inactivation. Importantly, the virus-loaded stem cells (SNV1) released larger number of infectious viral particles and virally encoded proteins, leading to augmented therapeutic efficacy in vitro and in animal tumor models.

Vanadyl sulfate-enhanced oncolytic virus immunotherapy mediates the antitumor immune response by upregulating the secretion of pro-inflammatory cytokines and chemokines

Oncolytic viruses (OVs) are promising anticancer treatments that specifically replicate in and kill cancer cells and have profound immunostimulatory effects. We previously reported the potential of vanadium-based compounds such as vanadyl sulfate (VS) as immunostimulatory enhancers of OV immunotherapy. These compounds, in conjunction with RNA-based OVs such as oncolytic vesicular stomatitis virus (VSVΔ51), improve viral spread and oncolysis, leading to long-term antitumor immunity and prolonged survival in resistant tumor models. This effect is associated with a virus-induced antiviral type I IFN response shifting towards a type II IFN response in the presence of vanadium. Here, we investigated the systemic impact of VS+VSVΔ51 combination therapy to understand the immunological mechanism of action leading to improved antitumor responses. VS+VSVΔ51 combination therapy significantly increased the levels of IFN-γ and IL-6, and improved tumor antigen-specific T-cell responses. Supported by immunological profiling and as a proof of concept for the design of more effective therapeutic regimens, we found that local delivery of IL-12 using VSVΔ51 in combination with VS further improved therapeutic outcomes in a syngeneic CT26WT colon cancer model.

SIRPα antibody combined with oncolytic virus OH2 protects against tumours by activating innate immunity and reprogramming the tumour immune microenvironment

BACKGROUND

The combination of oncolytic viruses (OVs) with immune checkpoint blockades is a research hotspot and has shown good efficacy. Here, we present the first attempt to combine oncolytic herpes simplex virus 2 (OH2) with an anti-SIRPα antibody as an antitumour treatment. Our results provide unique insight into the combination of innate immunity with OV.

METHODS

We verified the polarization and activation of OH2 in RAW264.7 cells in vitro. Subsequently, we evaluated the antitumour ability of OH2 and anti-SIRPα combined therapy in a tumour-bearing mouse model. RNA-seq and Single-cell RNA-seq were used to characterize the changes in the tumour microenvironment.

RESULTS

The OH2 lysates effectively stimulated RAW264.7 cells to polarize towards the M1 but not the M2 phenotype and activated the function of the M1 phenotype in vitro. In the macrophage clearance experiment, OH2 therapy induced polarization of M1 macrophages and participated in the antitumour immune response in a tumour-bearing mouse model. Treatment with a combination of OH2 and anti-SIRPα effectively inhibited tumour growth and significantly prolonged the survival time of the mice, and this result was more obvious in the mouse model with a larger tumour volume at the beginning of the treatment. These results suggest that combination therapy can more profoundly reshape the TME and activate stronger innate and adaptive immune responses.

CONCLUSIONS

Our data support the feasibility of oncolytic virus therapy in combination with anti-SIRPα antibodies and suggest a new strategy for oncolytic virus therapy.

Development of intravenously administered synthetic RNA virus immunotherapy for the treatment of cancer

The therapeutic effectiveness of oncolytic viruses (OVs) delivered intravenously is limited by the development of neutralizing antibody responses against the virus. To circumvent this limitation and to enable repeated systemic administration of OVs, here we develop Synthetic RNA viruses consisting of a viral RNA genome (vRNA) formulated within lipid nanoparticles. For two Synthetic RNA virus drug candidates, Seneca Valley virus (SVV) and Coxsackievirus A21, we demonstrate vRNA delivery and replication, virus assembly, spread and lysis of tumor cells leading to potent anti-tumor efficacy, even in the presence of OV neutralizing antibodies in the bloodstream. Synthetic-SVV replication in tumors promotes immune cell infiltration, remodeling of the tumor microenvironment, and enhances the activity of anti-PD-1 checkpoint inhibitor. In mouse and non-human primates, Synthetic-SVV is well tolerated reaching exposure well above the requirement for anti-tumor activity. Altogether, the Synthetic RNA virus platform provides an approach that enables repeat intravenous administration of viral immunotherapy.

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.

The Metabolic Relationship Between Viral Infection and Cancer

Viruses are fundamental tools in cancer research. They were used to discover the first oncogenes in the 1970s, and they are now being modified for use as antitumor therapeutics. Key to both of these oncogenic and oncolytic properties is the ability of viruses to rewire host cell metabolism. In this review, we describe how viral oncogenes alter metabolism to increase the synthesis of macromolecules necessary for both viral replication and tumor growth. We then describe how understanding the specific metabolic requirements of virus-infected cells can help guide strategies to improve the efficacy of oncolytic viruses, and we highlight immunometabolism and tumor microenvironment research that could also increase the therapeutic benefits of oncolytic viruses. We also describe how studies describing the therapeutic effects of dietary nutrient restriction in cancer can suggest new avenues for research into antiviral therapeutics.

Therapeutic Efficacy of an Oncolytic Influenza Virus Carrying an Antibody Against Programmed Cell Death 1 in Hepatocellular Carcinoma

Oncolytic virus therapy is a promising novel immunotherapy. In this report, we engineered a novel oncolytic influenza virus (IV) carrying an antihuman programmed cell death 1 (PD-1) monoclonal antibody utilizing reverse genetics. A reassortant chimeric IV, named rFlu-huPD1, was synthesized as follows: the heavy chain of the PD-1 antibody was encoded on the PB1 fragment, and the light chain of the PD-1 antibody was encoded on the polymerase acid protein fragment. rFlu-huPD1 antibodies were produced in infected ovalantoic eggs and could replicate to high titers. Moreover, selective cytotoxicity of rFlu-huPD1 was upregulated in multiple hepatocellular carcinoma (HCC) cell lines compared with a control, as determined by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Furthermore, the activation of T cells in the spleen of tumor-bearing BALB/c mice treated with rFlu-huPD1 was observed, especially cytotoxic CD8+ T cell activation in vivo. In addition, in a patient-derived xenograft liver cancer mouse model, tumor growth was reduced and the overall survival of the mice was increased by intratumoral injections with rFlu-huPD1 compared with wild-type PR8 virus. Taken together, these findings provide evidence for the utility of a combination of oncolytic IVs expressing PD-1 inhibitors for use in HCC virotherapy.

The Landscape of Nanovectors for Modulation in Cancer Immunotherapy

Immunotherapy represents a promising strategy for the treatment of cancer, which functions via the reprogramming and activation of antitumor immunity. However, adverse events resulting from immunotherapy that are related to the low specificity of tumor cell-targeting represent a limitation of immunotherapy's efficacy. The potential of nanotechnologies is represented by the possibilities of immunotherapeutical agents being carried by nanoparticles with various material types, shapes, sizes, coated ligands, associated loading methods, hydrophilicities, elasticities, and biocompatibilities. In this review, the principal types of nanovectors (nanopharmaceutics and bioinspired nanoparticles) are summarized along with the shortcomings in nanoparticle delivery and the main factors that modulate efficacy (the EPR effect, protein coronas, and microbiota). The mechanisms by which nanovectors can target cancer cells, the tumor immune microenvironment (TIME), and the peripheral immune system are also presented. A possible mathematical model for the cellular communication mechanisms related to exosomes as nanocarriers is proposed.

Targeting circulating monocytes with CCL2-loaded liposomes armed with an oncolytic adenovirus

Oncolytic viruses (OVs) selectively replicate in and destroy cancer cells resulting in anti-tumor immunity. However, clinical use remains a challenge because of virus clearance upon intravenous delivery. OV packaging using a nanomedicine approach could overcome this. Here we encapsulate an oncolytic adenovirus (Ad[I/PPT-E1A]) into CCL2-coated liposomes in order to exploit recruitment of CCR2-expressing circulating monocytes into tumors. We demonstrate successful encapsulation of Ad[I/PPT-E1A] into CCL2-coated liposomes that were preferentially taken up by CCR2-expressing monocytes. No complex-related toxicities were observed following incubation with prostate tumor cells and the encapsulation did not affect virus oncolytic activity in vitro. Furthermore, intravenous administration of our nanomedicine resulted in a significant reduction in tumor size and pulmonary metastasis in prostate cancer-bearing mice whereby a 1000-fold less virus was needed compared to Ad[I/PPT-E1A] alone. Taken together our data provide an opportunity to target OVs via circulation to inaccessible tumors using liposome-assisted drug delivery.

M11: A Tropism-modified Oncolytic Adenovirus Arming with Tumor-homing Peptide for Advanced Ovarian Cancer Therapies

Oncolytic adenoviruses (OAds) have shown great promise in cancer therapy, but their efficacy has been greatly limited by poor tumor selectivity and highly off-target liver sequestration. Herein, we generate a novel "stealth' and tumor-targeting oncolytic adenovirus vector M0-TMTP1 through inserting TMTP1 (NVVRQ), a tumor homing peptide specifically targeting metastasis, into the hypervariable region 5 (HVR5) of hexon. M0-TMTP1 exhibits increased transduction of tumor cells in vitro. In vivo biodistribution of M0-TMTP1 in an intraperitoneal disseminated ovarian cancer model showed significantly reduced virus load in major organs but apparent aggregation in tumors. The tumor-to-liver ratio of M0-TMTP1 was nearly 5000-fold higher than control adenovirus M0. Further, we armed M0-TMTP1 with trunked BID (tBID), a mitochondrial apoptosis protein, to obtain M11. Combining M11 with cisplatin (DDP) could induce an intensive antitumor effect in vitro and in vivo. Moreover, this combination therapy showed higher biosafety. Taken together, our results suggest that M11 represents a tumor-targeting, efficacious, and relatively nontoxic viro-therapeutic agent, and these findings might offer renewed hope for tumor management.

Local treatment of a pediatric osteosarcoma model with a 4-1BBL armed oncolytic adenovirus results in an antitumor effect and leads to immune memory

Osteosarcoma is an aggressive bone tumor occurring primarily in pediatric patients. Despite years of intensive research, the outcomes of patients with metastatic disease or who do not respond to therapy have remained poor and have not changed in the last 30 years. Oncolytic virotherapy is becoming a reality to treat local and metastatic tumors while maintaining a favorable safety profile. Delta-24-ACT is a replicative oncolytic adenovirus engineered to selectively target cancer cells and to potentiate immune responses through expression of the immune costimulatory ligand 4-1BB. This work aimed to assess the antisarcoma effect of Delta-24-ACT. MTS and replication assays were used to quantify the antitumor effects of Delta-24-ACT in vitro in osteosarcoma human and murine cell lines. Evaluation of the in vivo antitumor effect and immune response to Delta-24-ACT was performed in immunocompetent mice bearing orthotopic K7M2 cell line. Immunophenotyping of the tumor microenvironment was characterized by immunohistochemistry and flow cytometry. In vitro, Delta-24-ACT killed osteosarcoma cells and triggered the production of danger signals. In vivo, local treatment with Delta-24-ACT led to antitumor effects against both the primary tumor and spontaneous metastases in a murine osteosarcoma model. Viral treatment was safe, with no noted toxicity. Delta-24-ACT significantly increased the median survival time of treated mice. Collectively, our data identify Delta-24-ACT administration as an effective and safe therapeutic strategy for local and metastatic osteosarcoma. These results support clinical translation of this viral immunotherapy approach.

Efficacy and safety of a third-generation oncolytic herpes virus G47Δ in models of human esophageal carcinoma

Treatment options are limited for esophageal carcinoma (EC). G47Δ, a triple-mutated, conditionally replicating herpes simplex virus type 1 (HSV-1), exhibits enhanced killing of tumor cells with high safety features. Here, we studied the efficacy of G47Δ using preclinical models of human EC. In vitro, G47Δ showed efficient cytopathic effects and replication capabilities in all eight human esophageal cancer cell lines tested. In athymic mice harboring subcutaneous tumors of human EC (KYSE180, TE8, and OE19), two intratumoral injections with G47Δ significantly inhibited the tumor growth. To mimic the clinical treatment situations, we established an orthotopic EC model using luciferase-expressing TE8 cells (TE8-luc). An intratumoral injection with G47Δ markedly inhibited the growth of orthotopic TE8-luc tumors in athymic mice. Furthermore, we evaluated the safety of applying G47Δ to the esophagus in mice. A/J mice inoculated intraesophageally or administered orally with G47Δ (10⁷ plaque-forming units [pfu]) survived for more than 2 months without remarkable symptoms, whereas the majority with wild-type HSV-1 (10⁶ pfu) deteriorated within 10 days. PCR analyses showed that the G47Δ DNA was confined to the esophagus after intraesophageal inoculation and was not detected in major organs after oral administration. Our results provide a rationale for the clinical use of G47Δ for treating EC.

Oncolytic Viruses: Newest Frontier for Cancer Immunotherapy

Cancer remains a leading cause of death worldwide. Despite many signs of progress, currently available cancer treatments often do not provide desired outcomes for too many cancers. Therefore, newer and more effective therapeutic approaches are needed. Oncolytic viruses (OVs) have emerged as a novel cancer treatment modality, which selectively targets and kills cancer cells while sparing normal ones. In the past several decades, many different OV candidates have been developed and tested in both laboratory settings as well as in cancer patient clinical trials. Many approaches have been taken to overcome the limitations of OVs, including engineering OVs to selectively activate anti-tumor immune responses. However, newer approaches like the combination of OVs with current immunotherapies to convert "immune-cold" tumors to "immune-hot" will almost certainly improve the potency of OVs. Here, we discuss strategies that are explored to further improve oncolytic virotherapy.

Phosphor-IWS1-dependent U2AF2 splicing regulates trafficking of CAR-E-positive intronless gene mRNAs and sensitivity to viral infection

AKT-phosphorylated IWS1 promotes Histone H3K36 trimethylation and alternative RNA splicing of target genes, including the U2AF65 splicing factor-encoding U2AF2. The predominant U2AF2 transcript, upon IWS1 phosphorylation block, lacks the RS-domain-encoding exon 2, and encodes a protein which fails to bind Prp19. Here we show that although both U2AF65 isoforms bind intronless mRNAs containing cytoplasmic accumulation region elements (CAR-E), only the RS domain-containing U2AF65 recruits Prp19 and promotes their nuclear export. The loading of U2AF65 to CAR-Elements was RS domain-independent, but RNA PolII-dependent. Virus- or poly(I:C)-induced type I IFNs are encoded by genes targeted by the pathway. IWS1 phosphorylation-deficient cells therefore, express reduced levels of IFNα1/IFNβ1 proteins, and exhibit enhanced sensitivity to infection by multiple cytolytic viruses. Enhanced sensitivity of IWS1-deficient cells to Vesicular Stomatitis Virus and Reovirus resulted in enhanced apoptotic cell death via caspase activation. Inhibition of this pathway may therefore sensitize cancer cells to oncolytic viruses.

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.

Successful cancer immune therapy correlates with a T cell-inflamed tumour microenvironment. Authors show here that co-administration of a self-adjuvanting protein vaccine and an antigen-expressing oncolytic virus in an optimised regimen strongly enhances T cell immunogenicity and may turn non-inflamed tumours proinflammatory and less resistant to checkpoint blockade therapy.

Recent Advances in the Treatment of Bone Metastases and Primary Bone Tumors: An Up-to-Date Review

In the last decades, the treatment of primary and secondary bone tumors has faced a slow-down in its development, being mainly based on chemotherapy, radiotherapy, and surgical interventions. However, these conventional therapeutic strategies present a series of disadvantages (e.g., multidrug resistance, tumor recurrence, severe side effects, formation of large bone defects), which limit their application and efficacy. In recent years, these procedures were combined with several adjuvant therapies, with different degrees of success. To overcome the drawbacks of current therapies and improve treatment outcomes, other strategies started being investigated, like carrier-mediated drug delivery, bone substitutes for repairing bone defects, and multifunctional scaffolds with bone tissue regeneration and antitumor properties. Thus, this paper aims to present the types of bone tumors and their current treatment approaches, further focusing on the recent advances in new therapeutic alternatives.

Oncolytic Herpes Simplex Virus-Based Therapies for Cancer

With the increased worldwide burden of cancer, including aggressive and resistant cancers, oncolytic virotherapy has emerged as a viable therapeutic option. Oncolytic herpes simplex virus (oHSV) can be genetically engineered to target cancer cells while sparing normal cells. This leads to the direct killing of cancer cells and the activation of the host immunity to recognize and attack the tumor. Different variants of oHSV have been developed to optimize its antitumor effects. In this review, we discuss the development of oHSV, its antitumor mechanism of action and the clinical trials that have employed oHSV variants to treat different types of tumor.

Human immunology and immunotherapy: main achievements and challenges

The immune system is a fascinating world of cells, soluble factors, interacting cells, and tissues, all of which are interconnected. The highly complex nature of the immune system makes it difficult to view it as a whole, but researchers are now trying to put all the pieces of the puzzle together to obtain a more complete picture. The development of new specialized equipment and immunological techniques, genetic approaches, animal models, and a long list of monoclonal antibodies, among many other factors, are improving our knowledge of this sophisticated system. The different types of cell subsets, soluble factors, membrane molecules, and cell functionalities are some aspects that we are starting to understand, together with their roles in health, aging, and illness. This knowledge is filling many of the gaps, and in some cases, it has led to changes in our previous assumptions; e.g., adaptive immune cells were previously thought to be unique memory cells until trained innate immunity was observed, and several innate immune cells with features similar to those of cytokine-secreting T cells have been discovered. Moreover, we have improved our knowledge not only regarding immune-mediated illnesses and how the immune system works and interacts with other systems and components (such as the microbiome) but also in terms of ways to manipulate this system through immunotherapy. The development of different types of immunotherapies, including vaccines (prophylactic and therapeutic), and the use of pathogens, monoclonal antibodies, recombinant proteins, cytokines, and cellular immunotherapies, are changing the way in which we approach many diseases, especially cancer.

Efficient delivery of oncolytic enterovirus by carrier cell line NK-92

Many members of the enterovirus family are considered as promising oncolytic agents; however, their systemic administration is largely inefficient due to the rapid neutralization of the virus in the circulation and the barrier functions of the endothelium. We aimed to evaluate natural killer cells as carriers for the delivery of oncolytic enteroviruses, which would combine the effects of cell immunotherapy with virotherapy. We tested four strains of nonpathogenic enteroviruses against the glioblastoma cell line panel and evaluated the produced infectious titers. Next, we explored whether these virus strains could be delivered to the tumor by natural killer cell line NK-92, which is being actively evaluated as a clinically acceptable therapeutic. Several strains of enteroviruses demonstrated oncolytic properties, but only coxsackievirus A7 (CVA7) could replicate in NK-92 cells efficiently. We compared the delivery efficiency of CVA7 in vivo, using NK-92 cells and direct intravenous administration, and found significant advantages of cell delivery even after a single injection. This suggests that the NK-92 cell line can be utilized as a vehicle for the delivery of the oncolytic strain of CVA7, which would improve the clinical potential of this viral oncolytic for the treatment of glioblastoma multiforme and other forms of cancer.