Recombinant Newcastle disease virus expressing human interleukin-2 serves as a potential candidate for tumor therapy

Oncolytic Newcastle disease virus carrying the IL24 gene exerts antitumor effects by inhibiting tumor growth and vascular sprouting

The second-leading cause of death, cancer, poses a significant threat to human life. Innovations in cancer therapies are crucial due to limitations in traditional approaches. Newcastle disease virus (NDV), a nonpathogenic oncolytic virus, exhibits multifunctional anticancer properties by selectively infecting, replicating, and eliminating tumor cells. To enhance NDV's antitumor activity, four oncolytic NDV viruses were developed, incorporating IL24 and/or GM-CSF genes at different gene loci using reverse genetics. In vitro experiments revealed that oncolytic NDV virus augmented the antitumor efficacy of the parental virus rClone30, inhibiting tumor cell proliferation, inducing tumor cell fusion, and promoting apoptosis. Moreover, NDV carrying the IL24 gene inhibited microvessel formation in CAM experiments. Evaluation in a mouse model of liver cancer confirmed the therapeutic efficacy of oncolytic NDV viral therapy. Tumors in mice treated with oncolytic NDV virus significantly decreased in size, accompanied by tumor cell detachment and apoptosis evident in pathological sections. Furthermore, oncolytic NDV virus enhanced T cell and dendritic cell production and substantially improved the survival rate of mice with hepatocellular carcinoma, with rClone30-IL24(P/M) demonstrating significant therapeutic effects. This study establishes a basis for utilizing oncolytic NDV virus as an antitumor agent in clinical practice.

Personalizing Oncolytic Immunovirotherapy Approaches

Development of successful cancer therapeutics requires exploration of the differences in genetics, metabolism, and interactions with the immune system among malignant and normal cells. The clinical observation of spontaneous tumor regression following natural infection with microorganism has created the premise of their use as cancer therapeutics. Oncolytic viruses (OVs) originate from viruses with attenuated virulence in humans, well-characterized vaccine strains of known human pathogens, or engineered replication-deficient viral vectors. Their selectivity is based on receptor expression level and post entry restriction factors that favor replication in the tumor, while keeping the normal cells unharmed. Clinical trials have demonstrated a wide range of patient responses to virotherapy, with subgroups of patients significantly benefiting from OV administration. Tumor-specific gene signatures, including antiviral interferon-stimulated gene (ISG) expression profile, have demonstrated a strong correlation with tumor permissiveness to infection. Furthermore, the combination of OVs with immunotherapeutics, including anticancer vaccines and immune checkpoint inhibitors [ICIs, such as anti-PD-1/PD-L1 or anti-CTLA-4 and chimeric antigen receptor (CAR)-T or CAR-NK cells], could synergistically improve the therapeutic outcome. Creating response prediction algorithms represents an important step for the transition to individualized immunovirotherapy approaches in the clinic. Integrative predictors could include tumor mutational burden (TMB), inflammatory gene signature, phenotype of tumor-infiltrating lymphocytes, tumor microenvironment (TME), and immune checkpoint receptor expression on both immune and target cells. Additionally, the gut microbiota has recently been recognized as a systemic immunomodulatory factor and could further be used in the optimization of individualized immunovirotherapy algorithms.

Viral Vectors Expressing Interleukin 2 for Cancer Immunotherapy

Interleukin 2 (IL-2) plays a crucial role in T cell growth and survival, enhancing the cytotoxic activity of natural killer and cytotoxic T cells and thus functioning as a versatile master proinflammatory anticancer cytokine. The FDA has approved IL-2 cytokine therapy for the treatment of metastatic melanoma and metastatic renal cell carcinoma. However, IL-2 therapy has significant constraints, including a short serum half-life, low tumor accumulation, and life-threatening toxicities associated with high doses. Oncolytic viruses (OVs) offer a promising option for cancer immunotherapy, selectively targeting and destroying cancer cells while sparing healthy cells. Numerous studies have demonstrated the successful delivery of IL-2 to the tumor microenvironment without compromising safety using OVs such as vaccinia, Sendai, parvo, Newcastle disease, tanapox, and adenoviruses. Additionally, by engineering OVs to coexpress IL-2 with other anticancer transgenes, the immune properties of IL-2 can be further enhanced. Preclinical and clinical studies have shown promising antitumor effects of IL-2-expressing viral vectors, either alone or in combination with other anticancer therapies. This review summarizes the therapeutic potential of IL-2-expressing viral vectors and their antitumor mechanisms of action.

Development of Molecular Mechanisms and Their Application on Oncolytic Newcastle Disease Virus in Cancer Therapy

Cancer is caused by the destruction or mutation of cellular genetic materials induced by environmental or genetic factors. It is defined by uncontrolled cell proliferation and abnormality of the apoptotic pathways. The majority of human malignancies are characterized by distant metastasis and dissemination. Currently, the most common means of cancer treatment include surgery, radiotherapy, and chemotherapy, which usually damage healthy cells and cause toxicity in patients. Targeted therapy is an effective tumor treatment method with few side effects. At present, some targeted therapeutic drugs have achieved encouraging results in clinical studies, but finding an effective solution to improve the targeting and delivery efficiency of these drugs remains a challenge. In recent years, oncolytic viruses (OVs) have been used to direct the tumor-targeted therapy or immunotherapy. Newcastle disease virus (NDV) is a solid oncolytic agent capable of directly killing tumor cells and increasing tumor antigen exposure. Simultaneously, NDV can trigger the proliferation of tumor-specific immune cells and thus improve the therapeutic efficacy of NDV in cancer. Based on NDV’s inherent oncolytic activity and the stimulation of antitumor immune responses, the combination of NDV and other tumor therapy approaches can improve the antitumor efficacy while reducing drug toxicity, indicating a broad application potential. We discussed the biological properties of NDV, the antitumor molecular mechanisms of oncolytic NDV, and its application in the field of tumor therapy in this review. Furthermore, we presented new insights into the challenges that NDV will confront and suggestions for increasing NDV’s therapeutic efficacy in cancer.

Oncolytic viruses and pancreatic cancer

BACKGROUND

Today, the pancreatic cancer prognosis is poor and genetic technology is developing to treat various types of cancers. Scientists are actively looking for a new technique to design a therapeutic strategy to treat pancreatic cancer. Several oncolytic viruses are known to be valuable tools for pancreatic cancer treatment. Recent Studies demonstrate their effectiveness and safety in various administration routes such as direct intratumoral, intracutaneous, intravascular, and other routes.

METHOD

In this study, all studies conducted in the past 20 years have been reviewed. Reputable scientific databases including Irandoc, Scopus, Google Scholar and PubMed, are searched for the keywords of Pancreatic cancer, oncolytic, viruses and treatment and the latest information about them is obtained.

RESULTS

Engineering the oncolytic viruses' genome and insertion of intended transgenes including cytokines or shRNAs, has caused promising promotions in pancreatic cancer treatment. Some oncolytic viruses inhibit tumors directly and some through activation of immune responses.

CONCLUSION

This approach showed some signs of success in efficiency like immune system activation in the tumor environment, effective virus targeting in the tumor cells by systemic administration, and enhanced patient survival in comparison with the control group. But of course, until now, using these oncolytic viruses alone has not been effective in elimination of tumors.

Engineering strategies to enhance oncolytic viruses in cancer immunotherapy

Oncolytic viruses (OVs) are emerging as potentially useful platforms in treatment methods for patients with tumors. They preferentially target and kill tumor cells, leaving healthy cells unharmed. In addition to direct oncolysis, the essential and attractive aspect of oncolytic virotherapy is based on the intrinsic induction of both innate and adaptive immune responses. To further augment this efficacious response, OVs have been genetically engineered to express immune regulators that enhance or restore antitumor immunity. Recently, combinations of OVs with other immunotherapies, such as immune checkpoint inhibitors (ICIs), chimeric antigen receptors (CARs), antigen-specific T-cell receptors (TCRs) and autologous tumor-infiltrating lymphocytes (TILs), have led to promising progress in cancer treatment. This review summarizes the intrinsic mechanisms of OVs, describes the optimization strategies for using armed OVs to enhance the effects of antitumor immunity and highlights rational combinations of OVs with other immunotherapies in recent preclinical and clinical studies.

The recombinant Newcastle disease virus Anhinga strain expressing human TRAIL exhibit antitumor effects on a glioma nude mice model

Oncolytic virus therapy is perhaps the next major breakthrough in cancer treatment following the success in immunotherapy using immune checkpoint inhibitors. However, the potential oncolytic ability of the recombinant newcastle disease virus (NDV) Anhinga strain carried with tumor necrosis factor-related apoptosis inducing ligand (TRAIL) has not been fully explored at present. In the present study, the recombinant NDV/Anh-TRAIL that secretes soluble TRAIL was constructed and the experiment results suggested NDV/Anh-TRAIL as a promising candidate for glioma therapy. Growth kinetic and TRAIL secreted quantity of recombinant NDV/Anh-TRAIL virus were measured. Cytotoxic and cell apoptosis were analyzed for its anti-glioma therapy in vitro. Nude mice were used for the in vivo evaluation. Both tumor volume and mice behavior after injection were observed. The recombinant virus replicated with the same kinetics as the parental virus and the highest expression of TRAIL (77.8 ng/L) was found at 48 hours. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, a tetrazole and flow cytometry data revealed that the recombinant NDV/Anh-TRAIL (56.1 ± 8.2%) virus could induce a more severe apoptosis rate, when compared with the NDV wild type (37.2 ± 7.0%) and mock (7.0 ± 1.8%) groups (P < .01), in U251 cells. Furthermore, in the present animal study, the average tumor volume was smaller in the NDV/Anh-TRAIL group (97.21 mm3 ), when compared with the NDV wild type (205.03 mm3 , P < .05) and PBS (310.30 mm3 , P < .01) groups.

Cytokines in oncolytic virotherapy

Tumors represent a hostile environment for the effector cells of cancer immunosurveillance. Immunosuppressive receptors and soluble or membrane-bound ligands are abundantly exposed and released by malignant entities and their stromal accomplices. As a consequence, executioners of antitumor immunity inefficiently navigate across cancer tissues and fail to eliminate malignant targets. By inducing immunogenic cancer cell death, oncolytic viruses profoundly reshape the tumor microenvironment. They trigger the local spread of danger signals and tumor-associated (as well as viral) antigens, thus attracting antigen-presenting cells, promoting the activation and expansion of lymphocytic populations, facilitating their infiltration in the tumor bed, and reinvigorating cytotoxic immune activity. The present review recapitulates key chemokines, growth factors and other cytokines that orchestrate this ballet of antitumoral leukocytes upon oncolytic virotherapy.

Cytotoxicity study of the interleukin-12-expressing recombinant Newcastle disease virus strain, rAF-IL12, towards CT26 colon cancer cells in vitro and in vivo

Background

Oncolytic viruses have emerged as an alternative therapeutic modality for cancer as they can replicate specifically in tumour cells and induce toxic effects leading to apoptosis. Despite the great potentials and promising results shown in multiple studies, it appears that their efficacy is still moderate and deemed as not sufficient in clinical studies. In addressing this issue, genetic/molecular engineering approach has paved its way to improve the therapeutic efficacy as observed in the case of herpes simplex virus (HSV) expressing granulocyte–macrophage colony-stimulating factor (GM-CSF). This study aimed to explore the cytotoxicity effects of recombinant NDV strain AF2240-i expressing interleukin-12 (rAF-IL12) against CT26 colon cancer cells.

Methods

The cytotoxicity effect of rAF-IL12 against CT26 colon cancer cell line was determined by MTT assay. Based on the IC₅₀ value from the anti-proliferative assay, further downward assays such as Annexin V FITC and cell cycle progression were carried out and measured by flow cytometry. Then, the in vivo study was conducted where the rAF-IL12 viral injections were given at the intra-tumoral site of the CT26 tumour-burden mice. At the end of the experiment, serum biochemical, T cell immunophenotyping, serum cytokine, histopathology of tumour and organ section, TUNEL assay, and Nanostring gene expression analysis were performed.

Results

The rAF-IL12 induced apoptosis of CT26 colon cancer cells in vitro as revealed in the Annexin V FITC analysis and also arrested the cancer cells progression at G₁ phase of the cell cycle analysis. On the other hand, the rAF-IL12 significantly (p < 0.05) inhibited the growth of CT26 tumour in Balb/c mice and had regulated the immune system by increasing the level of CD4 + , CD8 + , IL-2, IL-12, and IFN-γ. Furthermore, the expression level of apoptosis-related genes (bax and p53) was up-regulated as a result of the rAF-IL12 treatment. Additionally, the rAF-IL12 had also down-regulated the expression level of KRAS, BRAF, MAPK1, Notch1, CCL2, and VEGF oncogenes. Besides, rAF-IL12 intra-tumoral delivery was considered safe and not hazardous to the host as evidenced in pathophysiology of the normal tissues and organs of the mice as well as from the serum biochemistry profile of liver and kidney.

Conclusions

These results indicated that rAF-IL12 had better anti-tumoral and cytotoxicity effects compared to its parental wild-type, AF2240-i in combatting the CT26 colon cancer model.

Engineering Newcastle Disease Virus as an Oncolytic Vector for Intratumoral Delivery of Immune Checkpoint Inhibitors and Immunocytokines

Newcastle disease virus (NDV) is an attractive candidate for oncolytic immunotherapy due to its ability to replicate in tumor cells and potentially to overcome the inherently immunosuppressive nature of the tumor microenvironment. The advent of checkpoint blockade immunotherapy over the past few years represents a paradigm shift in cancer therapy. However, the prevalence of severe immune-related adverse events with CTLA4 and PD1 pathway blockade in clinical studies, especially in combination therapy groups, is a cause for concern. Immunotherapies with cytokines have also been extensively explored, but they have been associated with adverse events in clinical trials. Oncolytic vectors engineered to express checkpoint blockade antibodies and cytokines could provide an avenue for reducing the clinical toxicity associated with systemic therapy by concentrating the immunomodulatory payload at the site of disease. In this study, we engineered six different recombinant viruses: NDVs expressing checkpoint inhibitors (rNDV-anti-PD1 and rNDV-anti-PDL1); superagonists (rNDV-anti-CD28); and immunocytokines, where the antibodies are fused to an immunostimulatory cytokine, such as interleukin 12 (IL-12) (rNDV-anti-CD28-murine IL-12 [mIL-12], rNDV-anti-PD1-mIL-12, and rNDV-anti-PDL1-mIL-12). These six engineered viruses induced tumor control and survival benefits in both highly aggressive unilateral and bilateral B16-F10 murine melanoma models, indicative of an abscopal effect. The data represent a strong proof of concept on which further clinical evaluation could build.IMPORTANCE Checkpoint inhibitor therapy has shown tremendous efficacy, but also frequent and often severe side effects-especially when multiple drugs of the class are used simultaneously. Similarly, many investigational immunotherapy agents, which have shown promise in animal models, have failed in clinical trials due to dose-limiting toxicity when administered systemically. This study utilized a murine melanoma model to evaluate the efficacy of intratumoral injections of recombinant NDVs engineered to express multiple immunotherapeutic proteins with well-documented side effects in humans. Our results indicate that intratumoral administration of these recombinant NDVs, particularly when combined with systemic CTLA4 checkpoint inhibition, exerts a robust effect in treated and nontreated tumors, indicative of a systemic antitumoral response. The intratumoral delivery of rNDVs expressing immunotherapeutic proteins may be an effective method of targeting the immune cell populations most relevant for antitumoral immunity and allowing us to restrict the use of systemic immunotherapy agents.

Design and application of oncolytic viruses for cancer immunotherapy

The approval of the first oncolytic virus (OV) for the treatment of metastatic melanoma and the recent discovery that the use of oncolytic viruses may enhance cancer immunotherapies targeted against various immune checkpoint proteins have attracted great interest in the field of cancer virotherapy. OVs are designed to target and kill cancer cells leaving normal cell unharmed. OV infection and concomitant cancer cell killing stimulate anti-tumour immunity and modulates tumour microenvironment towards less immunosuppressive phenotype. The intrinsic capacity of OVs to turn immunologically cold tumours into immunologically hot tumours, and to increase immune cell and cytokine infiltration, can be further enhanced by arming OVs with transgenes that increase their immunostimulatory activities and direct immune responses specifically towards cancer cells. These OVs, specifically engineered to be used as cancer immunotherapeutics, can be synergized with other immune modulators or cytotoxic agents to achieve the most potent immunotherapy for cancer.

Evaluation of a Recombinant Newcastle Disease Virus Expressing Human IL12 against Human Breast Cancer

The Newcastle disease virus (NDV) strain AF2240 is an avian avulavirus that has been demonstrated to possess oncolytic activity against cancer cells. However, to illicit a greater anti-cancer immune response, it is believed that the incorporation of immunostimulatory genes such as IL12 into a recombinant NDV backbone will enhance its oncolytic effect. In this study, a newly developed recombinant NDV that expresses IL12 (rAF-IL12) was tested for its safety, stability and cytotoxicity. The stability of rAF-IL12 was maintained when passaged in specific pathogen free (SPF) chicken eggs from passage 1 to passage 10; with an HA titer of 2⁹. Based on the results obtained from the MTT cytotoxic assay, rAF-IL12 was determined to be safe as it only induced cytotoxic effects against normal chicken cell lines and human breast cancer cells while sparing normal cells. Significant tumor growth inhibition (52%) was observed in the rAF-IL12-treated mice. The in vivo safety profile of rAF-IL12 was confirmed through histological observation and viral load titer assay. The concentration and presence of the expressed IL12 was quantified and verified via ELISA assay. In summary, rAF-IL12 was proven to be safe, selectively replicating in chicken and cancer cells and was able to maintain its stability throughout several passages; thus enhancing its potential as an anti-breast cancer vaccine.

Exosomes Carry microRNAs into Neighboring Cells to Promote Diffusive Infection of Newcastle Disease Virus

Newcastle disease virus (NDV), an avian paramyxovirus, was shown to prefer to replicate in tumor cells instead of normal cells; however, this mechanism has not been fully elucidated. Exosomes play a crucial role in intercellular communication due to the bioactive substances they carry. Several studies have shown that exosomes are involved in virus infections. However, the effect that exosomes have on NDV-infected tumor cells is not known. In this study, we focus on the role of exosomes secreted by NDV-infected HeLa cells in promoting NDV replication. Three miRNA candidates (miR-1273f, miR-1184, and miR-198) embraced by exosomes were associated with enhancing NDV-induced cytopathic effects on HeLa cells. Furthermore, luciferase assays, RT-qPCR, and enzyme-linked immunosorbent assay (ELISA) all demonstrated that these miRNAs could suppress interferon (IFN)-β gene expression. Enhanced NDV replication in HeLa cells was identified by Western blot and plaque assays. Based on these results, we speculate that NDV employed exosomes entry into neighboring cells, which carry miRNAs, resulting in inhibition of the IFN pathway and promotion of viral infection. To our knowledge, this is the first report on the involvement of NDV-employed exosomes in tumor cells, and as such, it provides new insights into the development of anti-tumor therapies.

Tune Up In Situ Autovaccination against Solid Tumors with Oncolytic Viruses

With the progress of immunotherapy in cancer, oncolytic viruses (OVs) have attracted more and more attention during the past decade. Due to their cancer-selective and immunogenic properties, OVs are considered ideal candidates to be combined with immunotherapy to increase both specificity and efficacy in cancer treatment. OVs preferentially replicate in and lyse cancer cells, resulting in in situ autovaccination leading to adaptive anti-virus and anti-tumor immunity. The main challenge in OV approaches is how to redirect the host immunity from anti-virus to anti-tumor and optimize the clinical outcome of cancer patients. Here, we summarize the conceptual updates on oncolytic virotherapy and immunotherapy in cancer, and the development of strategies to enhance the virus-mediated anti-tumor immune response, including: (1) arm OVs with cytokines to modulate innate and adaptive immunity; (2) combining OVs with immune checkpoint inhibitors to release T cell inhibition; (3) combining OVs with immune co-stimulators to enhance T cell activation. Future studies need to be enforced on developing strategies to augment the systemic effect on metastasized tumors.

A review of virulent Newcastle disease viruses in the United States and the role of wild birds in viral persistence and spread

Newcastle disease is caused by virulent strains of Newcastle disease virus (NDV), which causes substantial morbidity and mortality events worldwide in poultry. The virus strains can be differentiated as lentogenic, mesogenic, or velogenic based on a mean death time in chicken embryos. Currently, velogenic strains of NDV are not endemic in United States domestic poultry; however, these strains are present in other countries and are occasionally detected in wild birds in the U.S. A viral introduction into domestic poultry could have severe economic consequences due to the loss of production from sick and dying birds, the cost of control measures such as depopulation and disinfection measures, and the trade restrictions that would likely be imposed as a result of an outbreak. Due to the disease-free status of the U.S. and the high cost of a potential viral incursion to the poultry industry, a qualitative risk analysis was performed to evaluate the vulnerabilities of the U.S. against the introduction of virulent strains of NDV. The most likely routes of virus introduction are explored and data gathered by several federal agencies is provided. Recommendations are ultimately provided for data that would be useful to further understand NDV on the landscape and to utilize all existing sampling opportunities to begin to comprehend viral movement and further characterize the risk of NDV introduction into the U.S.

Oncolytic Viruses-Interaction of Virus and Tumor Cells in the Battle to Eliminate Cancer

Oncolytic viruses (OVs) are an emerging treatment option for many cancer types and have recently been the focus of extensive research aiming to develop their therapeutic potential. The ultimate aim is to design a virus which can effectively replicate within the host, specifically target and lyse tumor cells and induce robust, long lasting tumor-specific immunity. There are a number of viruses which are either naturally tumor-selective or can be modified to specifically target and eliminate tumor cells. This means they are able to infect only tumor cells and healthy tissue remains unharmed. This specificity is imperative in order to reduce the side effects of oncolytic virotherapy. These viruses can also be modified by various methods including insertion and deletion of specific genes with the aim of improving their efficacy and safety profiles. In this review, we have provided an overview of the various virus species currently being investigated for their oncolytic potential and the positive and negative effects of a multitude of modifications used to increase their infectivity, anti-tumor immunity, and treatment safety, in particular focusing on the interaction of tumor cells and OVs.

Targeting Melanoma with Cancer-Killing Viruses

Melanoma is the deadliest skin cancer with ever-increasing incidence. Despite the development in diagnostics and therapies, metastatic melanoma is still associated with significant morbidity and mortality. Oncolytic viruses (OVs) represent a class of novel therapeutic agents for cancer by possessing two closely related properties for tumor reduction: virus-induced lysis of tumor cells and induction of host anti-tumor immune responses. A variety of viruses, either in "natural" or in genetically modified forms, have exhibited a remarkable therapeutic efficacy in regressing melanoma in experimental and/or clinical studies. This review provides a comprehensive summary of the molecular and cellular mechanisms of action of these viruses, which involve manipulating and targeting the abnormalities of melanoma, and can be categorized as enhancing viral tropism, targeting the tumor microenvironment and increasing the innate and adaptive antitumor responses. Additionally, this review describes the "biomarkers" and deregulated pathways of melanoma that are responsible for melanoma initiation, progression and metastasis. Advances in understanding these abnormalities of melanoma have resulted in effective targeted and immuno-therapies, and could potentially be applied for engineering OVs with enhanced oncolytic activity in future.

Rescue of nonlytic Newcastle Disease Virus (NDV) expressing IL-15 for cancer immunotherapy

In order to test and enhance the antitumor activity against mice melanoma by NDV-modified tumor vaccine, a recombinant NDV expressing IL-15 (LX/(IL-15)) was generated by reverse genetics. Then, the expression level and biological activity of IL-15 were examined. Our results showed that mice tumor cell lines infected with LX/(IL-15) expressed IL-15 at a high level, and that expressed IL-15 was biologically active. Expression kinetics demonstrated that the highest expression level of IL-15 was at 48h post infection. The cytotoxicity assay showed that murine melanoma cells modified with LX/(IL-15) could significantly enhance the antitumor immune response in vitro. In vivo study also showed that murine melanoma cells modified with LX/(IL-15) could prevent melanoma growth in mice. Taken together, our data strongly indicated that recombinant LX/(IL-15) is a promising agent for cancer immunotherapy both for human and animal.

Recombinant Newcastle disease virus expressing human TRAIL as a potential candidate for hepatoma therapy

Newcastle disease virus (NDV) have shown oncolytic therapeutic efficacy in preclinical studies and are currently proved for clinical trials. We have previously reported, for the first time, NDV Anhinga strain has an efficient cancer therapeutic efficacy in hepatoma. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) functions as a cytokine to selectively kill various cancer cells without toxicity to most normal cells. Numerous studies have demonstrated the potential use of recombinant soluble TRAIL as a cancer therapeutic agent. In this study, we have showed administration of a recombinant NDV Anhinga strain expressing soluble TRAIL (NDV/Anh-TRAIL) results in an efficient suppression of hepatocellular carcinoma without significant toxicity. The results show that recombinant NDV Anhinga strain expressing soluble TRAIL is a promising candidate for hepatoma therapy.

Tanapoxvirus lacking a neuregulin-like gene regresses human melanoma tumors in nude mice

Neuregulin (NRG), an epidermal growth factor is known to promote the growth of various cell types, including human melanoma cells through ErbB family of tyrosine kinases receptors. Tanapoxvirus (TPV)-encoded protein TPV-15L, a functional mimic of NRG, also acts through ErbB receptors. Here, we show that the TPV-15L protein promotes melanoma proliferation. TPV recombinant generated by deleting the 15L gene (TPVΔ15L) showed replication ability similar to that of wild-type TPV (wtTPV) in owl monkey kidney cells, human lung fibroblast (WI-38) cells, and human melanoma (SK-MEL-3) cells. However, a TPV recombinant with both 15L and the thymidine kinase (TK) gene 66R ablated (TPVΔ15LΔ66R) replicated less efficiently compared to TPVΔ15L and the parental virus. TPVΔ15L exhibited more robust tumor regression in the melanoma-bearing nude mice compared to other TPV recombinants. Our results indicate that deletion of TPV-15L gene product which facilitates the growth of human melanoma cells can be an effective strategy to enhance the oncolytic potential of TPV for the treatment of melanoma.

Recombinant Newcastle disease virus expressing P53 demonstrates promising antitumor efficiency in hepatoma model

Background

Numerous studies have demonstrated that the NDV-mediated gene therapy is a promising new approach for treatment of cancers. P53 plays a vital role in tumor suppression and surveillance. Therefore, we hypothesize that a recombinant NDV expressing P53 would be an ideal agent for the hepatoma therapy.

Results

In the essay, the human P53 gene was incorporated into the genome of a lentogenic strain (named rNDV-P53), which did not affect viral replication kinetics and magnitude in HepG2 cells. Compared to the vehicle virus, rNDV-P53 increased cell growth suppressor ratio and early apoptosis by 2 folds, and decreased the mitochondrial membrane potential in HepG2 cells. In vivo studies, treatment with rNDV-P53 reduced tumor volume of tumor-bearing mice by more than 4 folds, tumor weight by more than 5 folds comparing with rNDV. The 120-day survival rate of rNDV-P53-treated mice was 75 %, survival rate of rNDV-treated mice was 12.5 %. TUNEL analysis showed a significant increase in the apoptosis rate in the tumor tissues of rNDV-P53-treated mice than that of rNDV-treated mice. Moreover, serum chemistries revealed an insignificant change of blood urea nitrogen (BUN), creatinine levels, alanine aminotransferase (ALT) and aspartate transaminase (AST) in rNDV-P53-treated group compared to normal mice, suggesting treatment with the recombinant virus was not toxic.

Conclusion

rNDV-P53 is a potent candidate for carcinoma therapy especially for hepatocarcinoma.

Recombinant Newcastle disease virus (NDV/Anh-IL-2) expressing human IL-2 as a potential candidate for suppresses growth of hepatoma therapy

Newcastle disease virus (NDV) have shown oncolytic therapeutic efficacy in preclinical study and are currently approved for clinical trials. NDV Anhinga strain which is a mesogenic strain should be classified as lytic strain and has a therapeutic efficacy in hepatocellular cancer. In this study, we evaluated the capacity of NDV Anhinga strain to elicit immune reaction in vivo and the possibility for using as a vaccine vector for expressing tumor therapeutic factors. Interleukin-2 (IL-2) could boost the immune response against the tumor cells. Therefore, we use NDV Anhinga strain as backbone to construct a recombinant virus (NDV/Anh-IL-2) expressing IL-2. The virus growth curve showed that the production of recombinant NDV/Anh-IL-2 was slightly delayed compared to the wild type. The NDV/Anh-IL-2 strain could express soluble IL-2 and effectively inhibit the growth of hepatocellular carcinoma in vivo. 60 days post-treatment, mice which were completely cured by previous treatment were well protected when rechallenged with the same tumor cell. From the H&E-stained sections, intense infiltration of lymphocyte was observed in the NDV Anhinga strain treated group, especially in NDV/Anh-IL-2 group. The NDV Anhinga strain could not only kill the tumor directly, but could also elicit immune reaction and a potent immunological memory when killing tumor in vivo. In conclusion, the Anhinga strain could be an effective vector for tumor therapy; the recombinant NDV/Anh-IL-2 strain expressing soluble IL-2 is a promising candidate for hepatoma therapy.

Oncolytic Immunotherapy for Treatment of Cancer

Immunotherapy entails the treatment of disease by modulation of the immune system. As detailed in the previous chapters, the different modes of achieving immune modulation are many, including the use of small/large molecules, cellular therapy, and radiation. Oncolytic viruses that can specifically attack, replicate within, and destroy tumors represent one of the most promising classes of agents for cancer immunotherapy (recently termed as oncolytic immunotherapy). The notion of oncolytic immunotherapy is considered as the way in which virus-induced tumor cell death (known as immunogenic cancer cell death (ICD)) allows the immune system to recognize tumor cells and provide long-lasting antitumor immunity. Both immune responses toward the virus and ICD together contribute toward successful antitumor efficacy. What is now becoming increasingly clear is that monotherapies, through any of the modalities detailed in this book, are neither sufficient in eradicating tumors nor in providing long-lasting antitumor immune responses and that combination therapies may deliver enhanced efficacy. After the rise of the genetic engineering era, it has been possible to engineer viruses to harbor combination-like characteristics to enhance their potency in cancer immunotherapy. This chapter provides a historical background on oncolytic virotherapy and its future application in cancer immunotherapy, especially as a combination therapy with other treatment modalities.

Newcastle Disease Virus: Potential Therapeutic Application for Human and Canine Lymphoma

Research on oncolytic viruses has mostly been directed towards the treatment of solid tumors, which has yielded limited information regarding their activity in hematological cancer. It has also been directed towards the treatment of humans, yet veterinary medicine may also benefit. Several strains of the Newcastle disease virus (NDV) have been used as oncolytics in vitro and in a number of in vivo experiments. We studied the cytolytic effect of NDV-MLS, a low virulence attenuated lentogenic strain, on a human large B-cell lymphoma cell line (SU-DHL-4), as well as on primary canine-derived B-cell lymphoma cells, and compared them to healthy peripheral blood mononuclear cells (PBMC) from both humans and dogs. NDV-MLS reduced cell survival in both human (42% ± 5%) and dog (34% ± 12%) lymphoma cells as compared to untreated controls. No significant effect on PBMC was seen. Cell death involved apoptosis as documented by flow-cytometry. NDV-MLS infections of malignant lymphoma tumors in vivo in dogs were confirmed by electron microscopy. Early (24 h) biodistribution of intravenous injection of 1 × 10¹² TCID₅₀ (tissue culture infective dose) in a dog with T-cell lymphoma showed viral localization only in the kidney, the salivary gland, the lung and the stomach by immunohistochemistry and/or endpoint PCR. We conclude that NDV-MLS may be a promising agent for the treatment of lymphomas. Future research is needed to elucidate the optimal therapeutic regimen and establish appropriate biosafety measures.

Recombinant Newcastle Disease Virus Encoding IL-12 and/or IL-2 as Potential Candidate for Hepatoma Carcinoma Therapy

Interleukins as immunomodulators are promising therapeutic agents for cancer therapy. Previous studies showed that there was an improved antitumor immunity in tumor-bearing mice using recombinant Newcastle disease virus carrying for interleukin-2. Interleukin-12 is a promising antitumor cytokine too. So we investigated and compared the antitumor effect of genetically engineered Newcastle disease virus strains expressing both interleukin-12 and/or interleukin-2 (rClone30-interleukin-2, rClone30-interleukin-12, and rClone30-interleukin-12-interleukin-2). In vitro studies showed that rClone30s could efficiently infect tumor cells and express interleukin-12 and/or interleukin-2. 3-(4,5-Dimethylthiazol-2-y)-2,5-diphenyl-tetrazolium bromide results showed rClone30s possessed strong cytotoxic activities against multiple tumor cell lines (U251, HepG2, A549, and Hela). Animal studies showed that rClone30-interleukin-12-interleukin-2 was more effective in inhibition of murine hepatoma carcinoma tumors, with the mean tumor volume (day 14) of 141.70 mm(3) comparing 165.67 mm(3) of rClone30-interleukin-12 group, 210.47 mm(3) of rClone30-interleukin-2 group, 574.70 mm(3) of rClone30 group, and 1206.83 mm(3) of phosphate-buffered saline group. Moreover, the rClone30-interleukin-12-interleukin-2 treated mice secreted more interferon γ (333.518 pg/mL) and its downstream cytokine interferon-γ induced protein 10 (16.006 pg/mL) in tumor than the rClone30-interleukin-12 group (interferon γ: 257.548 pg/mL; interferon-γ induced protein 10: 13.601 pg/mL), rClone30-interleukin2 group (interferon γ: 124.601 pg/mL; interferon-γ induced protein 10: 9.779 pg/mL), or rClone30 group (interferon γ: 48.630 pg/mL; interferon-γ induced protein 10:1.650 pg/mL). For the survival study, rClone30-interleukin12-interleukin2 increased the survival rate (12 of 16) of the tumor-bearing mice versus 11 of 16 in rClone30-interleukin-12 group, 10 of 16 in rClone30-interleukin-2 group, 7 of 16 in Clone30 group, and 0/16 in phosphate-buffered saline group, respectively. To determine whether the mice treated with recombinant virus developed protective immune response, the mice were rechallenged with the same tumor cells. The results showed that viral-treated mice were significantly protected from rechallenge. These results suggest that expressing both interleukin-2 and/or interleukin-12 could be ideal approaches to enhance the antitumor ability of Newcastle disease virus, and rClone30-interleukin-12-interleukin-2 is slightly superior over rClone30-interleukin-12 and rClone30-interleukin-2 alone.

Recombinant Immunomodulating Lentogenic or Mesogenic Oncolytic Newcastle Disease Virus for Treatment of Pancreatic Adenocarcinoma

Oncolytic Newcastle disease virus (NDV) might be a promising new therapeutic agent for the treatment of pancreatic cancer. We evaluated recombinant NDVs (rNDVs) expressing interferon (rNDV-hIFNβ-F₀) or an IFN antagonistic protein (rNDV-NS1-F₀), as well as rNDV with increased virulence (rNDV-F_3aa) for oncolytic efficacy in human pancreatic adenocarcinoma cells. Expression of additional proteins did not hamper virus replication or cytotoxic effects on itself. However, expression of interferon, but not NS1, resulted in loss of multicycle replication. Conversely, increasing the virulence (rNDV-F_3aa) resulted in enhanced replication of the virus. Type I interferon was produced in high amounts by all tumor cells inoculated with rNDV-hIFNβ-F₀, while inoculation with rNDV-NS1-F₀ resulted in a complete block of interferon production in most cells. Inoculation of human pancreatic adenocarcinoma cells with rNDV-F_3aa caused markedly more cytotoxicity compared to rNDV-F₀, while inoculation with rNDV-hIFNβ-F₀ and rNDV-NS1-F₀ induced cytotoxic effects comparable to those induced by the parental rNDV-F₀. Evaluation in vivo using mice bearing subcutaneous pancreatic cancer xenografts revealed that only intratumoral injection with rNDV-F_3aa resulted in regression of tumors. We conclude that although lentogenic rNDVs harboring proteins that modulate the type I interferon pathway proteins do have an oncolytic effect, a more virulent mesogenic rNDV might be needed to improve oncolytic efficacy.

Promising oncolytic agents for metastatic breast cancer treatment

New therapies for metastatic breast cancer patients are urgently needed. The long-term survival rates remain unacceptably low for patients with recurrent disease or disseminated metastases. In addition, existing therapies often cause a variety of debilitating side effects that severely impact quality of life. Oncolytic viruses constitute a developing therapeutic modality in which interest continues to build due to their ability to spare normal tissue while selectively destroying tumor cells. A number of different viruses have been used to develop oncolytic agents for breast cancer, including herpes simplex virus, adenovirus, vaccinia virus, measles virus, reovirus, and others. In general, clinical trials for several cancers have demonstrated excellent safety records and evidence of efficacy. However, the impressive tumor responses often observed in preclinical studies have yet to be realized in the clinic. In order for the promise of oncolytic virotherapy to be fully realized for breast cancer patients, effectiveness must be demonstrated in metastatic disease. This review provides a summary of oncolytic virotherapy strategies being developed to target metastatic breast cancer.

Enhancement of the proapoptotic properties of newcastle disease virus promotes tumor remission in syngeneic murine cancer models

Newcastle disease virus (NDV) is considered a promising agent for cancer therapy due to its oncolytic properties. These include preferential replication in transformed cells, induction of innate and adaptive immune responses within tumors, and cytopathic effects in infected tumor cells due to the activation of apoptosis. To enhance the latter and thus possibly enhance the overall oncolytic activity of NDV, we generated a recombinant NDV encoding the human TNF receptor Fas (rNDV-B1/Fas). rNDV-B1/Fas replicates to similar titers as its wild-type (rNDV-B1) counterpart; however, overexpression of Fas in infected cells leads to higher levels of cytotoxicity correlated with faster and increased apoptosis responses, in which both the intrinsic and extrinsic pathways are activated earlier. Furthermore, in vivo studies in syngeneic murine melanoma models show an enhancement of the oncolytic properties of rNDV-B1/Fas, with major improvements in survival and tumor remission. Altogether, our data suggest that upregulation of the proapoptotic function of NDV is a viable approach to enhance its antitumor properties and adds to the currently known, rationally based strategies to design optimized therapeutic viral vectors for the treatment of cancer.

Apoptotic induction of lung adenocarcinoma A549 cells infected by recombinant RVG Newcastle disease virus (rL-RVG) in vitro

Newcastle disease virus (NDV) is a member of the genus Avulavirus in the Paramyxoviridae family and its antitumor properties depend on its ability to kill malignant cells while not affecting normal cells. The present study investigated a recombinant avirulent NDV LaSota strain (wild-type NDV strain) expressing the rabies virus glycoprotein (rL-RVG), examined its oncolytic effect on the lung adenocarcinoma A549 cell line and evaluated its potential to serve as a vaccine against lung cancer. A549 cells were infected with the rL-RVG virus and analyzed by MTT, western blot, polymerase chain reaction (PCR), immunofluorescence, terminal deoxynucleotidyl transferase dUTP nick end labeling and flow-cytometric analyses. PCR, western blot and immunofluorescence showed that the RVG gene and protein were stably expressed in A549 cells following infection with rL-RVG. The growth of A549 cells in the rL-RVG group was inhibited more effectively compared to those infected with the wild-type NDV strain. MTT results showed that cell growth inhibition rates in the rL-RVG group were significantly higher than those in the NDV group (P<0.05). Early apoptosis in the rL-RVG group was also more evident, with the apoptotic index being increased in rL-RVG group. The expression of the pro-apoptotic proteins caspase-3, -8 and -9 increased. The expression of caspase-3 decreased following application of the broad-specificity caspase inhibitor Z-VAD-FMK. However, the expression of the inhibitory apoptosis protein B-cell lymphoma 2 (bcl-2) did not change, but bcl-2-associated X/bcl-2 ratio was higher in the rL-RVG group than that in the NDV group. The rL-RVG strain was able to suppress lung cancer cell growth and promote lung cancer cell apoptosis to a greater extent than the wild-type NDV strain. Therefore, the rL-RVG strain is a potent antitumor agent.

Going viral with cancer immunotherapy

Recent clinical data have emphatically shown the capacity of our immune systems to eradicate even advanced cancers. Although oncolytic viruses (OVs) were originally designed to function as tumour-lysing therapeutics, they have now been clinically shown to initiate systemic antitumour immune responses. Cell signalling pathways that are activated and promote the growth of tumour cells also favour the growth and replication of viruses within the cancer. The ability to engineer OVs that express immune-stimulating 'cargo', the induction of immunogenic tumour cell death by OVs and the selective targeting of OVs to tumour beds suggests that they are the ideal reagents to enhance antitumour immune responses. Coupling of OV therapy with tumour antigen vaccination, immune checkpoint inhibitors and adoptive cell therapy seems to be ready to converge towards a new generation of multimodal therapeutics to improve outcomes for cancer patients.

Genetically engineered Newcastle disease virus expressing interleukin-2 and TNF-related apoptosis-inducing ligand for cancer therapy

Recombinant Newcastle disease virus (rNDV) have shown oncolytic therapeutic efficacy in preclinical studies and are currently in clinical trials. In this study, we have evaluated the possibility to enhance the cancer therapeutic potential of NDV by means of inserting both interleukin-2 (IL-2) and tumor necrosis factor-related apoptosis inducing ligand (TRAIL) delivered by rNDV. We demonstrated that rNDV expressing TRAIL (rNDV-TRAIL) or both human IL-2 and TRAIL (rNDV-IL-2-TRAIL) significantly enhanced inherent anti-neoplastic of rNDV by inducing apoptosis. And we showed that apoptosis-related genes mRNA expression was increased after treated with rNDV-TRAIL or rNDV-IL-2-TRAIL compared with rNDV and rNDV-IL-2. We also demonstrated that both rNDV-IL-2 and rNDV-IL-2-TRAIL induced proliferation of the CD4(+) and CD8(+) in treated mice and elicited expression of TNF-α and IFN-γ antitumor cytokines. These mice treated with oncolytic agents exhibited significant reduction in tumor development compared with mice treated with the parental virus. In addition, experiments in both hepatocellular carcinoma and melanoma-bearing mice demonstrated that the genetically engineered rNDV-IL-2-TRAIL exhibited prolonged animals' survival compared with rNDV, rNDV-IL-2, and rNDV-TRAIL. In conclusion, the immunotherapy and oncolytic virotherapy properties of NDV can be enhanced by the introduction of IL-2 and TRAIL genes, whose products initiated a broad cascade of immunological affects and induced tumor cells apoptosis in the microenvironment of the immune system.

Genetically engineered Newcastle disease virus expressing interleukin 2 is a potential drug candidate for cancer immunotherapy

Newcastle disease virus (NDV) is an intrinsically tumor-specific virus, several clinical trials have reported that mesogenic NDV is a safe and effective agent for human cancer therapy. Interleukin 2 (IL2) is a cytokine that stimulates T cell propagation to trigger innate and adaptive immunity. IL2 has been used for cancer therapy and has achieved curative effects. In this study, a recombinant NDV LaSota strain expressing human interleukin 2 (rLaSota/IL2) was generated. The ability of rLaSota/IL2 to express human IL2 was detected in the infected tumor cells. In addition, the activity of IL2 was analyzed. The antitumor potential of rLaSota/IL2 was studied by xenograph mice carrying H22 and B16-F10 cells. Tumor-specific CD4(+) and CD8(+) T cells and MHC II were also analyzed in the two tumor-bearing models. Our study showed that rLaSota/IL2 significantly stimulated tumor-specific cytotoxic T-lymphocyte (CTL) responses and increased regulatory CD4(+) and cytotoxic CD8(+) T cells proliferation. The treatment with rLaSota/IL2 led to tumor regression in tumor-bearing mice and prolonged the survival of tumor-bearing mice. Furthermore, tumor challenging experiments demonstrated that rLaSota/IL2 invoked mice a unique capacity to remember a pathogen through the generation of memory T cells, which protect the host in the event of reinfection and form adaptive immune system. The result indicates that tumor-infiltrating CD4(+) T regulatory cells may denote the effective regression of tumors. Taken together, rLaSota/IL2 has potential for immunotherapy and oncolytic therapy of cancers and may be an ideal candidate for clinical application in future cancer therapy.

Different responses of human pancreatic adenocarcinoma cell lines to oncolytic Newcastle disease virus infection

Newcastle disease virus (NDV) is a naturally occurring oncolytic virus with clinically proven efficacy against several human tumor types. Selective replication in and killing of tumor cells by NDV is thought to occur because of differences in innate immune responses between normal and tumor cells. In our effort to develop oncolytic virotherapy with NDV for patients with pancreatic cancer, we evaluated the responses to NDV infection and interferon (IFN) treatment of 11 different established human pancreatic adenocarcinoma cell lines (HPACs). Here we show that all HPACs were susceptible to NDV. However, this NDV infection resulted in different replication kinetics and cytotoxic effects. Better replication resulted in more cytotoxicity. No correlation was observed between defects in the IFN pathways and NDV replication or NDV-induced cytotoxicity. IFN production by HPACs after NDV infection differed substantially. Pretreatment of HPACs with IFN resulted in diminished NDV replication and decreased the cytotoxic effects in most HPACs. These findings suggest that not all HPACs have functional defects in the innate immune pathways, possibly resulting in resistance to oncolytic virus treatment. These data support the rationale for designing recombinant oncolytic NDVs with optimized virulence that should likely contain an antagonist of the IFN pathways.

Evolution of oncolytic viruses: novel strategies for cancer treatment

Many viruses have documented oncolytic activity, with the first evidence observed clinically over a decade ago. In recent years, there has been a resurgence of interest in the field of oncolytic viruses. Viruses may be innately oncotropic, lacking the ability to cause disease in people or they may require engineering to allow selective tumor targeting and attenuation of pathogenicity. Following infection of a neoplastic cell, several events may occur, including direct viral oncolysis, apoptosis, necrotic cell death and autophagic cellular demise. Of late, a large body of work has recognized the ability of oncolytic viruses (OVs) to activate the innate and adaptive immune system, as well as directly killing tumors. The production of viruses expressing transgenes encoding for cytokines, colony-stimulating factors, costimulatory molecules and tumor-associated antigens has been able to further incite immune responses against target tumors. Multiple OVs are now in the advanced stages of clinical trials, with several individual viruses having completed their respective trials with positive results. This review introduces the multiple mechanisms by which OVs are able to act as an antineoplastic therapy, either on their own or in combination with other more traditional treatment modalities. The full benefit and the place where OVs will be integrated into standard-of-care therapies will be determined with ongoing studies ranging from the laboratory to the patient. With various different viruses now in the clinic this therapeutic option is beginning to prove its worth, and the versatility of these agents means further innovative and novel applications will continue to be developed.

Recombinant Newcastle disease virus Anhinga strain (NDV/Anh-EGFP) for hepatoma therapy

Hepatocellular carcinoma remains one of the most common malignant tumors in the world. Newcastle disease virus (NDV) has been proved to be an efficient oncolytic agent. NDV tumor killing efficacy is not only dependening on the NDV strain but the type of tumor targeted. It is significant to discover more effective and safe oncolytic strains. We investigated the effectiveness of genetically engineered NDV Anhinga strain in hepatoma treatment. The modified virus containing an insertion of enhanced green fluorescent protein (EGFP), named NDV/Anh-EGFP. The antitumor efficacy of the recombinant virus on hepatoma was examined both in vivo and in vitro. NDV Anhinga strain, which could be classified as a lytic strain, is an effective oncolytic agent on hepatoma. There was no significant difference in the TCID50 and growth capability between the recombinant NDV and the parental. NDV/Anh-EGFP can obviously inhibit hepatocarcinoma development in vitro and in vivo. We demonstrate Anhinga strain could become a potent candidate for clinical carcinoma therapy especially for hepatocarcinoma.

Enhancement of immunogenicity of murine lymphocytic leukemia cells by transfection with BCG heat shock protein 70 gene

The effects of BCG heat shock protein 70 (BCG HSP70) gene transfection on tumorigenicity and immunogenicity of murine lymphocytic leukemia cell line (L1210) were studied. After HSP70 gene transfection, the tumor cells became strongly immunogenic and lost their tumorigenicity in syngeneic mice. It mainly exhibited that tumor growth was slow or without the formation of tumor, mean survival time of mice was significantly prolonged and a marked stimulating effect on L1210 specific Th1 cells detected by IFN-γ ELISPOT assay. Tumor-bearing mice treated with the L1210-HSP70 cells showed thorough coagulation necrosis and abundant CD8+ T lymphocyte infiltration. Meanwhile, as the tumor vaccine, the HSP70-transfected tumor cells could induce a protective immune response in vivo. It showed that the tumor growth was significantly inhibited, tumor diameter was markedly reduced and the survival time of tumor-bearing mice was further prolonged. Immunization with it also resulted in regression of the established L1210 tumor and prolonged survival time of mice. These results suggest that gene transfection of BCG HSP70 could effectively improve the immunogenicity of tumor cells and it may be used as a suitable candidate gene-modified cell vaccine for cancer immunotherapy.

Oncolytic Newcastle disease virus for cancer therapy: old challenges and new directions

Newcastle disease virus (NDV) is an avian paramyxovirus, which has been demonstrated to possess significant oncolytic activity against mammalian cancers. This review summarizes the research leading to the elucidation of the mechanisms of NDV-mediated oncolysis, as well as the development of novel oncolytic agents through the use of genetic engineering. Clinical trials utilizing NDV strains and NDV-based autologous tumor cell vaccines will expand our knowledge of these novel anticancer strategies and will ultimately result in the successful use of the virus in the clinical setting.

Apoptin enhances the oncolytic properties of Newcastle disease virus

OBJECTIVE

Naturally occurring strains of Newcastle disease virus (NDV) have demonstrated the potential to kill cancer cells in both preclinical and clinical studies. Previous studies showed that apoptin, the VP3 protein of chicken infectious anemia virus, is a p53-independent, Bcl-2-insensitive apoptotic protein with the ability to specifically induce apoptosis in transformed cells. In this study, we tested the hypothesis that apoptin enhances NDV-mediated tumor cell death.

METHODS

Reverse genetics was used to engineer an oncolytic NDV strain, FMW, to express apoptin. The antitumor effects of the recombinant virus (rFMW/AP) were also evaluated in the tumor cell lines and tumor-bearing mice.

RESULTS

Compared to the parental strain FMW, rFMW/AP was more potent in killing A459 and SMMC7721 tumor cells. Recombinant NDV also exhibited higher efficacy in suppressing tumor growth in mice bearing A549-induced tumors. Furthermore, rFMW/AP did not display apparent toxic effects in either normal cells or control mice.

CONCLUSION

Our results suggest that the recombinant NDV expressing apoptin is a promising novel antitumor agent.

Potentiating cancer immunotherapy using an oncolytic virus

Oncolytic viruses (OVs) are highly immunogenic and this limits their use in immune-competent hosts. Although immunosuppression may improve viral oncolysis, this gain is likely achieved at the cost of antitumoral immunity. We have developed a strategy wherein the immune response against the OV leads to enhanced therapeutic outcomes. We demonstrate that immunization with an adenoviral (Ad) vaccine before treatment with an oncolytic vesicular stomatitis virus (VSV) expressing the same tumor antigen (Ag) leads to significantly enhanced antitumoral immunity. Intratumoral replication of VSV was minimally attenuated in Ad-immunized hosts but extending the interval between treatments reduced the attenuating effect and further increased antitumoral immunity. More importantly, our combination approach shifted the immune response from viral Ags to tumor Ags and further reduced OV replication in normal tissues, leading to enhancements in both efficacy and safety. These studies also highlight the benefits of using a replicating, OV to boost a pre-existing antitumoral immune response as this approach generated larger responses versus tumor Ag in tumor-bearing hosts than could be achieved in tumor-free hosts. This strategy should be applicable to other vector combinations, tumor Ags, and tumor targets.

Use of the piggyBac transposon to create HIV-1 gag transgenic insect cell lines for continuous VLP production

BACKGROUND

Insect baculovirus-produced Human immunodeficiency virus type 1 (HIV-1) Gag virus-like-particles (VLPs) stimulate good humoral and cell-mediated immune responses in animals and are thought to be suitable as a vaccine candidate. Drawbacks to this production system include contamination of VLP preparations with baculovirus and the necessity for routine maintenance of infectious baculovirus stock. We used piggyBac transposition as a novel method to create transgenic insect cell lines for continuous VLP production as an alternative to the baculovirus system.

RESULTS

Transgenic cell lines maintained stable gag transgene integration and expression up to 100 cell passages, and although the level of VLPs produced was low compared to baculovirus-produced VLPs, they appeared similar in size and morphology to baculovirus-expressed VLPs. In a murine immunogenicity study, whereas baculovirus-produced VLPs elicited good CD4 immune responses in mice when used to boost a prime with a DNA vaccine, no boost response was elicited by transgenically produced VLPs.

CONCLUSION

Transgenic insect cells are stable and can produce HIV Pr55 Gag VLPs for over 100 passages: this novel result may simplify strategies aimed at making protein subunit vaccines for HIV. Immunogenicity of the Gag VLPs in mice was less than that of baculovirus-produced VLPs, which may be due to lack of baculovirus glycoprotein incorporation in the transgenic cell VLPs. Improved yield and immunogenicity of transgenic cell-produced VLPs may be achieved with the addition of further genetic elements into the piggyBac integron.

Intelligent design: combination therapy with oncolytic viruses

Metastatic cancer remains an incurable disease in the majority of cases and thus novel treatment strategies such as oncolytic virotherapy are rapidly advancing toward clinical use. In order to be successful, it is likely that some type of combination therapy will be necessary to have a meaningful impact on this disease. Although it may be tempting to simply combine an oncolytic virus with the existing standard radiation or chemotherapeutics, the long-term goal of such treatments must be to have a rational, potentially synergistic combination strategy that can be safely and easily used in the clinical setting. The combination of oncolytic virotherapy with existing radiotherapy and chemotherapy modalities is reviewed along with novel biologic therapies including immunotherapies, in order to help investigators make intelligent decisions during the clinical development of these products.

Recombinant Newcastle disease virus as a vaccine vector for cancer therapy

Naturally occurring strains of Newcastle disease virus (NDV) are currently being investigated in multiple clinical trials for oncolytic cancer therapy in the United States and abroad. We have previously reported, for the first time, the development of recombinant NDVs designed for enhanced cancer therapeutic efficacy. Specifically, we have shown that NDV engineered to express interleukin-2 (IL-2) generates a robust therapeutic response associated with increased tumor-specific T-cell infiltration after intratumoral administration in mice. We have now demonstrated that this therapeutic response is dependent on T cells and we have investigated the potential to focus the NDV-induced immune response toward a tumor-associated antigen (TAA) to enhance the inherent therapeutic efficacy of NDV further. We found that intratumoral treatments of tumor-bearing mice with recombinant NDV expressing a model TAA elicited an enhanced tumor-specific response, resulting in a significant increase in the number of complete tumor regressions compared with control NDV. Additionally, coadministration of NDV expressing a model TAA with NDV expressing IL-2 enhanced the TAA-directed response and led to more complete tumor regressions. Our results show that TAA-directed immunotherapy by oncolytic recombinant NDV alone or in combination with IL-2 results in an enhanced therapeutic efficacy and warrant consideration in the development of cancer therapies based on the use of oncolytic NDV.