Individualized Multimodal Immunotherapy (IMI): Scientific Rationale and Clinical Experience from a Single Institution

Oncolytic viruses and combinatorial immunotherapy for cancer (this Special Issue) are both part of cancer treatment at IOZK. This review focusses on an individual multimodal cancer immunotherapy concept developed by IOZK, Cologne, Germany. The scientific rationale for employing three main components is explained: (i) oncolytic Newcastle disease virus, (ii) modulated electrohyperthermia and (iii) individual tumor antigen and oncolytic virus modified dendritic cell vaccine (IO-VACR). The strategy involves repeated cancer-immunity cycles evoked in cancer patients by systemic oncolytic virus exposure plus hyperthermia pretreatment to induce immunogenic cell death followed by intradermal IO-VACR vaccination. As an example of the experience at IOZK, we present the latest results from combining the immunotherapy with standard treatment of patients suffering from glioblastoma multiforme. The promising clinical results in terms of overall survival benefit of additional individualized multimodal immunotherapy are presented. The cancer-immunity cycle, as introduced 10 years ago, describes key important steps occurring locally at the sites of both tumor and draining lymph nodes. This view is extended here towards systemic events occuring in blood where immunogenic cell death-induced tumor antigens are transported into the bone marrow. For 20 years it has been known that bone marrow is an antigen-responsive organ in which dendritic cells present tumor antigens to T cells leading to immunological synapse formation, tumor antigen-specific T cell activation and memory T cell formation. Bone marrow is known to be the most prominent source of de novo cellular generation in the body and to play an important role for the storage and maintenance of immunological memory. Its systemic activation is recommended to augment cancer-immunity cycles.

Methods behind oncolytic virus-based DC vaccines in cancer: Toward a multiphase combined treatment strategy for Glioblastoma (GBM) patients

Glioblastoma (GBM) remains an orphan cancer disease with poor outcome. Novel treatment strategies are needed. Immunotherapy has several modes of action. The addition of active specific immunotherapy with dendritic cell vaccines resulted in improved overall survival of patients. Integration of DC vaccination within the first-line combined treatment became a challenge, and immunogenic cell death immunotherapy during chemotherapy was introduced. We used a retrospective analysis using real world data to evaluate the complex combined treatment, which included individualized multimodal immunotherapy during and after standard of care, and which required adaptations during treatment, and found a further improvement of overall survival. We also discuss the use of real world data as evidence. Novel strategies to move the field of individualized multimodal immunotherapy forward for GBM patients are reviewed.

The Application of Evidence-Based Medicine in Individualized Medicine

The fundamental aim of healthcare is to improve overall health of the population by providing state-of-the-art healthcare for individuals at an affordable cost. The foundation for this system is largely referred to as "evidence-based medicine". Too often, evidence-based medicine is based solely on so-called "best research evidence", collected through randomized controlled trials while disregarding clinical expertise and patient expectations. As healthcare gravitates towards personalized and individualized medicine, such external clinical (research) evidence can inform, but never replace, individual clinical expertise. This applies in particular to orphan diseases, for which clinical trials are methodologically particularly problematic, and evidence derived from them is often questionable. Evidence-based medicine constitutes a complex process to allow doctors and patients to select the best possible solutions for each individual based on rapidly developing new therapeutic directions. This requires a revisit of the foundations of evidence-based medicine. A proposition as to how to manage evidence-based data in individualized immune-oncology is presented here.

Counteracting Immunosuppression in the Tumor Microenvironment by Oncolytic Newcastle Disease Virus and Cellular Immunotherapy

An apparent paradox exists between the evidence for spontaneous systemic T cell- mediated anti-tumor immune responses in cancer patients, observed particularly in their bone marrow, and local tumor growth in the periphery. This phenomenon, known as "concomitant immunity" suggests that the local tumor and its tumor microenvironment (TME) prevent systemic antitumor immunity to become effective. Oncolytic Newcastle disease virus (NDV), an agent with inherent anti-neoplastic and immune stimulatory properties, is capable of breaking therapy resistance and immunosuppression. This review updates latest information about immunosuppression by the TME and discusses mechanisms of how oncolytic viruses, in particular NDV, and cellular immunotherapy can counteract the immunosuppressive effect of the TME. With regard to cellular immunotherapy, the review presents pre-clinical studies of post-operative active-specific immunotherapy and of adoptive T cell-mediated therapy in immunocompetent mice. Memory T cell (MTC) transfer in tumor challenged T cell-deficient nu/nu mice demonstrates longevity and functionality of these cells. Graft-versus-leukemia (GvL) studies in mice demonstrate complete remission of late-stage disease including metastases and cachexia. T cell based immunotherapy studies with human cells in human tumor xenotransplanted NOD/SCID mice demonstrate superiority of bone marrow-derived as compared to blood-derived MTCs. Results from clinical studies presented include vaccination studies using two different types of NDV-modified cancer vaccine and a pilot adoptive T-cell mediated therapy study using re-activated bone marrow-derived cancer-reactive MTCs. As an example for what can be expected from clinical immunotherapy against tumors with an immunosuppressive TME, results from vaccination studies are presented from the aggressive brain tumor glioblastoma multiforme. The last decades of basic research in virology, oncology and immunology can be considered as a success story. Based on discoveries of these research areas, translational research and clinical studies have changed the way of treatment of cancer by introducing and including immunotherapy.

IMMU-03. Synergy between TMZ and individualized multimodal immunotherapy to improve Overall Survival of IDH1 wild-type MGMT promoter-unmethylated GBM patients

The prognosis of IDH1 wild-type MGMT promoter-unmethylated GBM patients remains poor. Addition of Temozolomide (TMZ) to first-line local treatment shifted the median overall survival (OS) from 11.8 to 12.6 months. We retrospectively analysed the value of individualized multimodal immunotherapy (IMI) to improve OS in these patients. All adults meeting the criteria and treated 06/2015-06/2021 were selected. Thirty-two patients (12f, 20m) had a median age of 47y (range 18-69) and a KPI of 70 (50-100). Extent of resection was complete (11), <complete (12) or not documented (9). Seven patients were treated with surgery/radio(chemo)therapy and subsequent IMI (Group-1); 25 patients were treated with radiochemotherapy followed by maintenance TMZ plus IMI during and after TMZ (Group-2). Age, KPI and extent of resection were not different amongst both groups. The median OS of group-1 patients was 11m (2y OS: 0%). Surprisingly the median OS of group-2 patients was 22m with 2y OS of 36% (CI95%: 16-57), which was significantly (Log-rank: p = 0.0001) different from group-1. The data suggest that addition of IMI after local therapy on its own has no relevant effect on OS in these GBM patients, similar to maintenance TMZ. However, the combination of both TMZ + IMI significantly improved OS. This finding might also have implications in the search for novel combined treatment approaches for children with malignant glioma.

Molecular Mechanisms of Anti-Neoplastic and Immune Stimulatory Properties of Oncolytic Newcastle Disease Virus

Oncolytic viruses represent interesting anti-cancer agents with high tumor selectivity and immune stimulatory potential. The present review provides an update of the molecular mechanisms of the anti-neoplastic and immune stimulatory properties of the avian paramyxovirus, Newcastle Disease Virus (NDV). The anti-neoplastic activities of NDV include (i) the endocytic targeting of the GTPase Rac1 in Ras-transformed human tumorigenic cells; (ii) the switch from cellular protein to viral protein synthesis and the induction of autophagy mediated by viral nucleoprotein NP; (iii) the virus replication mediated by viral RNA polymerase (large protein (L), associated with phosphoprotein (P)); (iv) the facilitation of NDV spread in tumors via the membrane budding of the virus progeny with the help of matrix protein (M) and fusion protein (F); and (v) the oncolysis via apoptosis, necroptosis, pyroptosis, or ferroptosis associated with immunogenic cell death. A special property of this oncolytic virus consists of its potential for breaking therapy resistance in human cancer cells. Eight examples of this important property are presented and explained. In healthy human cells, NDV infection activates the RIG-MAVs immune signaling pathway and establishes an anti-viral state based on a strong and uninhibited interferon α,ß response. The review also describes the molecular determinants and mechanisms of the NDV-mediated immune stimulatory effects, in which the viral hemagglutinin-neuraminidase (HN) protein plays a prominent role. The six viral proteins provide oncolytic NDV with a special profile in the treatment of cancer.

Synergy between TMZ and individualized multimodal immunotherapy to improve overall survival of IDH1 wild-type MGMT promoter-unmethylated GBM patients

The prognosis of IDH1 wild-type MGMT promoter-unmethylated GBM patients remains poor. Addition of Temozolomide (TMZ) to first-line local treatment shifted the median overall survival (OS) from 11.8 to 12.6 months. We retrospectively analyzed the value of individualized multimodal immunotherapy (IMI) to improve OS in these patients. All adults meeting the criteria and treated 06/2015-06/2021 were selected. Thirty-two patients (12f, 20m) had a median age of 47 y (range 18-69) and a KPI of 70 (50-100). Extent of resection was complete (11), <complete (12) or not documented (9). Seven patients were treated with surgery/radio(chemo)therapy and subsequent IMI (Group-1); 25 patients were treated with radiochemotherapy followed by maintenance TMZ plus IMI during and after TMZ (Group-2). Age, KPI and extent of resection were not different amongst both groups. The median OS of group-1 patients was 11 m (2 y OS: 0%). Surprisingly the median OS of group-2 patients was 22 m with 2 y OS of 36% (CI95%: 16-57), which was significantly (Log-rank: p = 0.0001) different from group-1. The data suggest that addition of IMI after local therapy on its own has no relevant effect on OS in these GBM patients, similar to maintenance TMZ. However, the combination of both TMZ + IMI significantly improved OS.

IMMU-25. SYNERGY BETWEEN TMZ AND INDIVIDUALIZED MULTIMODAL IMMUNOTHERAPY TO IMPROVE OS OF IDH1 WILD TYPE MGMT PROMOTOR UNMETHYLATED GBM PATIENTS

The prognosis of IDH1 wild type MGMT promotor unmethylated (MGMT-p-UM) GBM patients remains poor. Addition of TMZ to radiotherapy shifted the median OS from 11.8 to 12.6 months (Stupp, Lancet Oncol 2019). We retrospectively analysed the value of individualized multimodal immunotherapy (IMI) to improve OS in these patients. Adults with first event of IDH1wt GBM and documented status of MGMT-p-UM, and treated with IMI in the period June 2015 till July 2020, were selected. IMI consisted of 1/ immunogenic cell death (ICD) therapy (NDV injections + modulated electrohyperthermia), 2/ active specific immunotherapy with autologous mature dendritic cells loaded with tumor lysate or ICD therapy-induced serum-derived antigenic extracellular microvesicles and apoptotic bodies (IO-Vac® is an approved advanced therapy medicinal product since 27/05/2015), 3/ modulatory immunotherapy adapted to the patient, and 4/ complementary medicines. Twenty-eight patients (11f, 17m) had a median age of 48y (range 18-69) and a KPI of 90 (50-100). Extent of resection was complete (11), &lt; complete (9) or not documented (8). Seven patients were treated with surgery/radio(chemo)therapy and subsequent IMI (Group-1); 21 patients were treated with radiochemotherapy followed by maintenance TMZ + ICD therapy, followed by DC vaccines (Group-2). Both groups received further maintenance ICD therapy. Age, KPI and extent of resection were not different amongst both groups. PFS was not assessed because of challenges about pseudoprogression. The median OS of group-1 patients was 11m (2y OS: 0%). Surprisingly the median OS of group-2 patients was 18m with 2y OS of 17% (CI95%: +31, -15), which was significantly (Log-rank: p = 0.027) different from group-1. The data suggest that addition of IMI after local therapy on its own has no relevant effect on OS in IDH1 wild type MGMT-p-UM GBM patients, similar to maintenance TMZ. However, the combination of both TMZ + IMI significantly improves median OS.

DIPG-38. ADDITION OF MULTIMODAL IMMUNOTHERAPY TO COMBINATION TREATMENT STRATEGIES FOR CHILDREN WITH DIPG: FINAL RESULTS OF A COHORT OF CHILDREN

The prognosis of children with Diffuse Intrinsic Pontine Glioma (DIPG) remains dismal in spite of radio- and chemotherapy or therapies based on molecular biology diagnostics. Immunotherapy is a powerful and promising approach for improving the overall survival (OS). A retrospective analysis for feasibility, immune responsiveness and OS was performed on 41 children treated in compassionate use with Newcastle Disease Virus, hyperthermia and autologous dendritic cell vaccines as part of an individualized combined treatment approach for DIPG patients at diagnosis (n=28), or at time of progression (n=13). All except one patient had reduced values of at least one immune test before starting immunotherapy. In all patients at least one PanTum Detect test was outside the normal range. Ten patients had PDL1 mRNA expression in circulating tumor cells at diagnosis. Multimodal immunotherapy was feasible as scheduled, until progression, in all patients without major toxicity. When immunotherapy was part of primary treatment, median PFS and OS were 8.4m and 14.4m respectively with a 2-year OS of 10.7%. When immunotherapy was given at the time of progression, median PFS and OS calculated from diagnosis were 6.5m and 9.1m respectively. Th1 shift and rise in PanTum Detect test scores were linked with longer OS. Multimodal immunotherapy is feasible without major toxicity, and its value as part of a combination treatment for primary diagnosed DIPG should be elaborated in clinical trials.

Evidence-Based Medicine in Oncology: Commercial Versus Patient Benefit

At times of personalized and individualized medicine the concept of randomized- controlled clinical trials (RCTs) is being questioned. This review article explains principles of evidence-based medicine in oncology and shows an example of how evidence can be generated independently from RCTs. Personalized medicine involves molecular analysis of tumor properties and targeted therapy with small molecule inhibitors. Individualized medicine involves the whole patient (tumor and host) in the context of immunotherapy. The example is called Individualized Multimodal Immunotherapy (IMI). It is based on the individuality of immunological tumor-host interactions and on the concept of immunogenic tumor cell death (ICD) induced by an oncolytic virus. The evidence is generated by systematic data collection and analysis. The outcome is then shared with the scientific and medical community. The priority of big pharma studies is commercial benefit. Methods used to achieve this are described and have damaged the image of RCT studies in general. A critical discussion is recommended between all partners of the medical health system with regard to the conduct of RCTs by big pharma companies. Several clinics and institutions in Europe try to become more independent from pharma industry and to develop their own modern cancer therapeutics. Medical associations should include references to such studies from personalized and individualized medicine in their guidelines.

Position paper: new insights into the immunobiology and dynamics of tumor-host interactions require adaptations of clinical studies

INTRODUCTION

Prospective double-blind placebo-controlled randomized clinical trials (RCTs) are considered standard for the proof of the efficacy of oncologic therapies. Molecular methods have provided new insights into tumor biology and led to the development of targeted therapies. Due to the increasing complexity of molecular tumor characteristics and of the individuality of specific anti-tumor immune reactivity, RCTs are unfortunately only of limited use.

AREAS COVERED

The historical methods of drug research and approval and the related practices of reimbursement by statutory and private health insurance companies are being questioned. New, innovative methods for the documentation of evidence in personalized medicine will be addressed. Possible perspectives and new approaches are discussed, in particular with regard to glioblastoma.

EXPERT OPINION

Highly specialized translational oncology groups like the IOZK can contribute to medical progress and quick transfer 'from bench to bedside.' Their contribution should be acknowledged and taken into account more strongly in the development of guidelines and the reimbursement of therapy costs. Methodological plurality should be encouraged.

Addition of Multimodal Immunotherapy to Combination Treatment Strategies for Children with DIPG: A Single Institution Experience

Background: The prognosis of children with diffuse intrinsic pontine glioma (DIPG) remains dismal despite radio- and chemotherapy or molecular-targeted therapy. Immunotherapy is a powerful and promising approach for improving the overall survival (OS) of children with DIPG. Methods: A retrospective analysis for feasibility, immune responsiveness, and OS was performed on 41 children treated in compassionate use with multimodal therapy consisting of Newcastle disease virus, hyperthermia, and autologous dendritic cell vaccines as part of an individualized combinatorial treatment approach for DIPG patients. Results: Patients were treated at diagnosis (n = 28) or at the time of progression (n = 13). In the case of 16 patients, histone H3K27M mutation was confirmed by analysis of biopsy (n = 9) or liquid biopsy (n = 9) specimens. PDL1 mRNA expression was detected in circulating tumor cells of ten patients at diagnosis. Multimodal immunotherapy was feasible as scheduled, until progression, in all patients without major toxicity. When immunotherapy was part of primary treatment, median PFS and OS were 8.4 m and 14.4 m from the time of diagnosis, respectively, with a 2-year OS of 10.7%. When immunotherapy was given at the time of progression, median PFS and OS were 6.5 m and 9.1 m, respectively. A longer OS was associated with a Th1 shift and rise in PanTum Detect test scores. Conclusions: Multimodal immunotherapy is feasible without major toxicity, and warrants further investigation as part of a combinatorial treatment approach for children diagnosed with DIPG.

Cancer Vaccines and Oncolytic Viruses Exert Profoundly Lower Side Effects in Cancer Patients than Other Systemic Therapies: A Comparative Analysis

This review compares cytotoxic drugs, targeted therapies, and immunotherapies with regard to mechanisms and side effects. Targeted therapies relate to small molecule inhibitors. Immunotherapies include checkpoint inhibitory antibodies, chimeric antigen receptor (CAR) T-cells, cancer vaccines, and oncolytic viruses. All these therapeutic approaches fight systemic disease, be it micro-metastatic or metastatic. The analysis includes only studies with a proven therapeutic effect. A clear-cut difference is observed with regard to major adverse events (WHO grades 3-4). Such severe side effects are not observed with cancer vaccines/oncolytic viruses while they are seen with all the other systemic therapies. Reasons for this difference are discussed.

Breaking Therapy Resistance: An Update on Oncolytic Newcastle Disease Virus for Improvements of Cancer Therapy

Resistance to therapy is a major obstacle to cancer treatment. It may exist from the beginning, or it may develop during therapy. The review focusses on oncolytic Newcastle disease virus (NDV) as a biological agent with potential to break therapy resistance. This avian virus combines, upon inoculation into non-permissive hosts such as human, 12 described anti-neoplastic effects with 11 described immune stimulatory properties. Fifty years of clinical application of NDV give witness to the high safety profile of this biological agent. In 2015, an important milestone was achieved, namely the successful production of NDV according to Good Manufacturing Practice (GMP). Based on this, IOZK in Cologne, Germany, obtained a GMP certificate for the production of a dendritic cell vaccine loaded with tumor antigens from a lysate of patient-derived tumor cells together with immunological danger signals from NDV for intracutaneous application. This update includes single case reports and retrospective analyses from patients treated at IOZK. The review also presents future perspectives, including the concept of in situ vaccination and the combination of NDV or other oncolytic viruses with checkpoint inhibitors.

From chemotherapy to biological therapy: A review of novel concepts to reduce the side effects of systemic cancer treatment (Review)

The side effects of systemic chemotherapy used to treat cancer are often severe. For decades, oncologists have focused on treating the tumor, which may result in damage to the tumor-bearing host and its immune system. Recently, much attention has been paid to the immune system of patients and its activation via biological therapies. Biological therapies, including immunotherapy and oncolytic virus (OV) therapy, are often more physiological and well tolerated. The present review elucidated how these therapies work and why these therapies may be better tolerated: i) In contrast to chemotherapy, immunotherapies induce a memory function of the adaptive immunity system; ii) immunotherapies aim to specifically activate the immune system against cancer; side effects are low due to immune tolerance mechanisms, which maintain the integrity of the body in the presence of B and T lymphocytes with their antigen-receptor specificities and; iii) the type I interferon response, which is evoked by OVs, is an ancient innate immune defense system. Biological and physiological therapies, which support the immune system, may therefore benefit cancer treatment. The present review focused on immunotherapy, with the aim of reducing side effects and increasing long-lasting efficacy in cancer therapy.

Immunobiology of Newcastle Disease Virus and Its Use for Prophylactic Vaccination in Poultry and as Adjuvant for Therapeutic Vaccination in Cancer Patients

Newcastle disease (ND) is one of the most important diseases of poultry worldwide. In the last decades, molecular research has gained a lot of new information about its causative agent, newcastledisease virus (NDV). In poultry industry, certain strains of NDV have been used for preventive vaccination for more than 60 years. NDV has also been applied to cancer patients with beneficial effects for about 50 years, but this is less well known. The molecular basis for these differential effects of NDV in birds and man have been elucidated in the last decades and are explained in this review. The anti-neoplastic and immune-stimulatory properties in non-permissive hosts such as mouse and man have to do with the strong type I interferon responses induced in these foreign species. Additionally, NDV has the potential to break various types of tumor resistances and also to affect liver fibrosis. A main section is devoted to the benefits of clinical application of NDV and NDV-based vaccines to cancer patients. Reverse genetics technology allowed developing NDV into a vector suitable for gene therapy. Examples will be provided in which genetically engineered NDV is being used successfully as vector against new emerging viruses.

Fifty Years of Clinical Application of Newcastle Disease Virus: Time to Celebrate!

This review provides an overview of 50 years of basic and clinical research on an oncolytic avian virus, Newcastle Disease Virus (NDV), which has particular anti-neoplastic and immune stimulatory properties. Of special interest is the fact that this biological agent induces immunogenic cell death and systemic anti-tumor immunity. Furthermore, localized oncolytic virotherapy with NDV was shown to overcome systemic tumor resistance to immune checkpoint blockade immunotherapy. Clinical experience attests to low side effects and a high safety profile. This is due among others to the strong virus-induced type I interferon response. Other viral characteristics are lack of interaction with host cell DNA, lack of genetic recombination and independence of virus replication from cell proliferation. In this millennium, new recombinant strains of viruses are being produced with improved therapeutic properties. Clinical applications include single case observations, case series studies and Phase I to III studies.

Cancer-reactive memory T cells from bone marrow: Spontaneous induction and therapeutic potential (Review)

Cognate interactions between naïve tumor antigen (TA)-specific T cells and TA-presenting dendritic cells (DCs) are facilitated by secondary lymphoid organs such as lymph nodes or the spleen. These can result either in TA-specific tolerance or, depending on environmental costimulatory signals, in TA-specific immune responses. In the present review, we describe such events for the bone marrow (BM) when blood-borne TA, released from the primary tumor or expressed by blood circulating tumor cells or DCs enters the BM stroma and parenchyma. We argue that cognate T-DC interactions in the BM result in immune responses and generation of memory T cells (MTCs) rather than tolerance because T cells in the BM show an increased level of pre-activation. The review starts with the spontaneous induction of cancer-reactive MTCs in the BM and the involvement of such MTCs in the control of tumor dormancy. The main part deals with the therapeutic potency of BM MTCs. This is a new area of research in which the authors research group has performed pioneering studies which are summarized. These include studies in animal tumor models, studies with human cells in tumor xenotransplant models and clinical studies. Based on observations of an enormous expansion capacity, longevity and therapeutic capacity of BM MTCs, a hypothesis is presented which suggests the involvement of stem-like MTCs.

Oncolytic Newcastle disease virus as a prospective anti-cancer therapy. A biologic agent with potential to break therapy resistance

INTRODUCTION

Oncolytic viruses (OVs) selectively replicate in tumor cells and cause cancer cell death. Most OVs in clinical studies are genetically engineered. In contrast, the avian Newcastle disease virus (NDV) is a naturally oncolytic RNA virus. While anti-viral immunity is considered a major problem in achieving maximal tumor cell killing by OVs, this review discusses the importance of NDV immunogenic cell death (ICD) and how anti-viral immune responses can be integrated to induce maximal post-oncolytic T-cell-mediated anti-tumor immunity. Since replication of NDV is independent of host cell DNA replication (which is the target of many cytostatic drugs and radiotherapy) and because of other findings, oncolytic NDV is a candidate agent to break therapy resistance of tumor cells.

AREAS COVERED

Properties of this avian paramyxovirus are summarized with special emphasis to its anti-neoplastic and immune-stimulatory properties. The review then discusses prospective anti-cancer therapies, including treatments with NDV alone, and combinations with an autologous NDV-modified tumor cell vaccine or with a viral oncolysate pulsed dendritic cell vaccine. Various combinatorial approaches between these and with other modalities are also reviewed.

EXPERT OPINION

Post-oncolytic anti-tumor immunity based on ICD is in the expert's opinion of greater importance for long-term therapeutic effects than maximal tumor cell killing. Of the various combinatorial approaches discussed, the most promising and feasible for clinical practice appears to be the combination of systemic NDV pre-treatment with anti-tumor vaccination.

Signaling through RIG-I and type I interferon receptor: Immune activation by Newcastle disease virus in man versus immune evasion by Ebola virus (Review)

In this review, two types of RNA viruses are compared with regard to the type I interferon (IFN) response in order to obtain a better understanding of the molecular mechanisms of immune activation or evasion. Upon human infection, both viruses exert either beneficial or detrimental effects. The Newcastle disease virus (NDV), is a type strain for avian paramyxoviruses, while the Ebola virus (EBOV), is a virus affecting primates. During evolution, both viruses specifically adapted to their respective hosts, acquiring sophisticated viral escape mechanisms. Two types of receptors play an important role in the life cycle of these two viruses: cytoplasmic retinoic acid‑inducible gene I (RIG‑I) and membrane expressed type I IFN receptor (IFNAR). In mouse and human cells, NDV is a strong inducer of the type I IFN response. The early phase of this is initiated by signaling through RIG‑I and the late response by signaling through IFNAR. EBOV does not induce type I IFN responses in humans as it has viral proteins that specifically and strongly interfere with RIG‑I and IFNAR signaling, as well as immune activation. In this review, we discuss whether the beneficial effects of one virus can be exploited in the fight against the detrimental effects of the other.

Long-term survival of a breast cancer patient with extensive liver metastases upon immune and virotherapy: a case report

Liver metastases in breast cancer are associated with a poor prognosis. We report long-term survival of a patient with breast cancer and liver metastases. After operation the patient declined further standard therapy. Instead, she was treated with local hyperthermia, Newcastle disease virus and dendritic cell vaccination at the Immunological and Oncological Center Cologne (IOZK), Germany. A continuous high quality of life was reported and the patient survived more than 66 months after initial diagnosis. No recurrence or further metastases developed under treatment. Following treatment, a long-lasting tumor-reactive memory T-cell responsiveness could be documented. This possibly explains the favorable course of disease. Since this combination of therapies is not restricted to a particular tumor type, further exploration is warranted.

Long-term remission of prostate cancer with extensive bone metastases upon immuno- and virotherapy: A case report

The present study reports the case of a patient with hormone-refractory metastatic prostate cancer who had failed standard therapy, but then achieved complete remission following combined treatment with local hyperthermia (LHT), Newcastle disease virus and dendritic cell (DC) vaccination, which was an unusual combination. In August 2005, the patient underwent a radical prostatectomy. Despite standard treatment, the patient developed progressive bone metastases and stopped conventional therapy in June 2007. Starting in October 2007, the patient was treated with LHT, oncolytic virotherapy and DC vaccination. Prostate-specific antigen (PSA)-levels, with the highest level of 233.8 ng/ml in January 2008, decreased to 0.8 ng/ml in late February 2008. In March 2008, a reduction in bone metastases could be detected by positron emission tomography/computed tomography. Since then, the PSA levels have remained low and the patient is doing well. The treatment induced a long-lasting antitumor memory T-cell response. This possibly explains the long-term effectiveness of this novel experimental combined treatment approach.

Autologous tumor cell vaccines for post-operative active-specific immunotherapy of colorectal carcinoma: long-term patient survival and mechanism of function

Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths worldwide. Surgery remains the primary curative treatment but nearly 50% of patients relapse as consequence of micrometastatic or minimal residual disease (MRD) at the time of surgery. Spontaneous T-cell-mediated immune responses to CRC tumor-associated antigens (TAAs) in tumor-draining lymph nodes and in the bone marrow (BM) lead to infiltration of the tumors by lymphocytes. Certain types of such tumor-infiltrating lymphocytes (TILs) have a positive and others a negative impact on the patients' prognosis. This review focuses on advances in CRC active-specific immunotherapy (ASI), in particular on results from randomized controlled clinical studies employing therapeutic autologous tumor cell vaccines. The observed improvement of long-term survival is explained by activation and mobilization of a pre-existing repertoire of tumor-reactive memory T cells which, according to recent discoveries, reside in distinct niches of patients' bone marrow in neighborhood with hematopoietic (HSC) and mesenchymal (MSC) stem cells. Interestingly, memory T cells also contain a subset of stem memory T cells (SMTs) in addition to effector (EMTs) and central memory T cells (CMTs). The mechanism of function of a therapeutic vaccine in a chronic disease is distinct from that of prophylactic vaccines which have to generate de novo protective immune responses. The advantage of autologous vaccines for mobilization of a broad and highly individual repertoire of memory T cells will be discussed.

Multimodal cancer therapy involving oncolytic newcastle disease virus, autologous immune cells, and bi-specific antibodies

This paper focuses on oncolytic Newcastle disease virus (NDV). This paper summarizes (i) the peculiarities of this virus as an anti-cancer and immune stimulatory agent and (ii) the approaches to further harness this virus as a vector to combat cancer. Special emphasis is given on combining virus therapy with cell therapy and on improving tumor targeting. The review will include some of the authors work on NDV, bi-specific antibodies, and cell therapy as building blocks for a new perspective of multimodal cancer therapy. The broad anti-tumor immune reactivation includes innate and adaptive, tumor antigen (TA) specific and TA independent activities

Complete remission of cancer in late-stage disease by radiation and transfer of allogeneic MHC-matched immune T cells: lessons from GvL studies in animals

Most immunotherapy studies in animal tumor models are performed in early stages of the disease. Reports on the studies of treatment in late stages of tumor growth and metastasis are much rarer. To guide future efforts for treatment in late-stage disease, a model of effective immune rejection of advanced metastasized cancer is reviewed and lessons therefrom are summarized. Already cachectic DBA/2 mice with a subcutaneously transplanted syngeneic tumor (ESb-MP lymphoma) of 1.5 cm diameter and with macroscopic liver and kidney metastases at 4 weeks could be successfully treated by a combination of sublethal (5 Gy) irradiation followed by a single transfer of 20 million anti-tumor immune spleen cells from tumor-resistant allogeneic MHC-B10.D2 mice. Following intravenous cell transfer, the primary tumors became encapsulated and were eventually rejected from the skin while visceral metastases gradually disappeared leaving behind only scar tissue. There was wound-healing at the site of the rejected primary tumor, and the animals survived long term without any tumor recurrence. The complete eradication of late-stage disease by adoptive cellular immunotherapy could be corroborated noninvasively by (31)P-NMR spectroscopy of primary tumors and by (1)H-NMR microimaging of liver metastases. Conclusions from functional mechanistic studies in this model are summarized and clinical implications discussed.

Bispecific antibodies and trispecific immunocytokines for targeting the immune system against cancer: preparing for the future

Monoclonal anti-tumor antibodies (mAbs) that are clinically effective usually recruit, via their constant fragment (Fc) domain, Fc receptor (FcR)-positive accessory cells of the immune system and engage these additionally against the tumor. Since T cells are FcR negative, these important cells are not getting involved. In contrast to mAbs, bispecific antibodies (bsAbs) can be designed in such a way that they involve T cells. bsAbs are artificially designed molecules that bind simultaneously to two different antigens, one on the tumor cell, the other one on an immune effector cell such as CD3 on T cells. Such dual antibody constructs can cross-link tumor cells and T cells. Many such bsAb molecules at the surface of tumor cells can thus build a bridge to T cells and aggregate their CD3 molecules, thereby activating them for cytotoxic activity. BsAbs can also contain a third binding site, for instance a Fc domain or a cytokine that would bind to its respective cytokine receptor. The present review discusses the pros and cons for the use of the Fc fragment during the development of bsAbs using either cell-fusion or recombinant DNA technologies. The recombinant antibody technology allows the generation of very efficient bsAbs containing no Fc domain such as the bi-specific T-cell engager (BiTE). The strong antitumor activity of these molecules makes them very interesting new cancer therapeutics. Over the last decade, we have developed another concept, namely to combine bsAbs and multivalent immunocytokines with a tumor cell vaccine. The latter are patient-derived tumor cells modified by infection with a virus. The virus-Newcastle Disease Virus (NDV)-introduces, at the surface of the tumor cells, viral molecules that can serve as general anchors for the bsAbs. Our strategy aims at redirecting, in an Fc-independent fashion, activities of T cells and accessory cells against autologous tumor antigens. It creates very promising perspectives for a new generation of efficient and safe cancer therapeutics that should confer long-lasting anti-tumor immunity.

Oncolytic Newcastle Disease Virus as Cutting Edge between Tumor and Host

Oncolytic viruses (OVs) replicate selectively in tumor cells and exert anti-tumor cytotoxic activity. Among them, Newcastle Disease Virus (NDV), a bird RNA virus of the paramyxovirus family, appears outstanding. Its anti-tumor effect is based on: (i) oncolytic activity and (ii) immunostimulation. Together these activities facilitate the induction of post-oncolytic adaptive immunity. We will present milestones during the last 60 years of clinical evaluation of this virus. Two main strategies of clinical application were followed using the virus (i) as a virotherapeutic agent, which is applied systemically or (ii) as an immunostimulatory agent combined with tumor cells for vaccination of cancer patients. More recently, a third strategy evolved. It combines the strategies (i) and (ii) and includes also dendritic cells (DCs). The first step involves systemic application of NDV to condition the patient. The second step involves intradermal application of a special DC vaccine pulsed with viral oncolysate. This strategy, called NDV/DC, combines anti-cancer activity (oncolytic virotherapy) and immune-stimulatory properties (oncolytic immunotherapy) with the high potential of DCs (DC therapy) to prime naive T cells. The aim of such treatment is to first prepare the cancer-bearing host for immunocompetence and then to instruct the patient's immune system with information about tumor-associated antigens (TAAs) of its own tumor together with danger signals derived from virus infection. This multimodal concept should optimize the generation of strong polyclonal T cell reactivity targeted against the patient's TAAs and lead to the establishment of a long-lasting memory T cell repertoire.

Effective immune rejection of advanced metastasized cancer

A cellular cancer therapy is described with unique efficiency even in late-stage disease. in situ activated tumor-immune T cells, induced in allogeneic, tumor-resistant, MHC identical but superantigen different donor mice (B10.D2) could transfer strong graft-versus-leukemia (GvL) effects accompanied by only mild graft-versus-host (GvH) reactivity. Systemic immune cell transfer into 5 Gy irradiated DBA/2 mice bearing up to 4 week established syngeneic tumors and macrometastases led to massive infiltration of tumor tissues by CD4 and CD8 donor T lymphocytes. Upon interaction of immune CD4 donor T cells with host antigen presenting cells in synergy with immune CD8 donor T cells attacking the tumor cells directly, primary tumors (1.5 cm diameter) were encapsulated and rejected from the skin and liver metastases eradicated. For the first time, such adoptive cellular immunotherapy (ADI) was followed in individual live animals by P-31-NMR spectroscopy of primary tumors. An approximately 25,000 fold excess of metastatic tumor cells could be rejected as revealed quantitatively by FACScan analysis of lacZ gene transfected tumor cells.

Gamma-irradiation suppresses T-cell mediated protective immunity against a metastatic tumor in the afferent phase of the immune-response but enhances it in the efferent phase when given before immune cell transfer

Using a metastasizing animal tumor as a model we describe experimental conditions for obtaining either synergistic or antagonistic effects between host irradiation and T cell mediated antitumor immunity. The results were obtained in the well defined murine lymphoma ESb which is a spontaneous highly metastatic tumor variant expressing a tumor associated antigen that can induce protective immunity and tumor specific cytotoxic T lymphocyte (CTL) activity. Sublethal irradiation of mice during the afferent (induction) phase but not during the efferent (effector) phase of the antitumor immune response had a strong suppressive effect on protective immunity. The radiation mediated defect could be reconstituted by transfer of immune spleen cells. The immune system of syngeneic (DBA/2) and allogeneic (B10.D2) mice changed within 24 h after first contact with the ESb tumor cells from radio-sensitivity to radio-resistance possibly reflecting an active cellular response associated with the change from virgin to an antigen sensitized (primed) state of T lymphocyte differentiation. T cell depletion experiments revealed that the afferent phase was dependent on both CD4 and CD8 host T lymphocytes while the efferent phase was mainly CD8 T cell dependent. A synergistic effect between gamma-irradiation and antitumor immunity was observed in adoptive immunotherapy experiments. When tumor-bearing hosts were irradiated before intravenous transfer of either syngeneic or allogeneic antitumor immune T cells the expression of anti-metastatic protective immunity was greatly enhanced in comparison to identically treated non-irradiated hosts.

Changes in liver glycogen and lipid metabolism during transient graft-versus-host (GvH) and graft-versus-leukemia (GvL) reactivity

We investigated the influence of transient graft-versus-leukemia (GvL) and graft-versus-host reactivity (GvH) following allogeneic immune cell transfer on the glycogen and lipid metabolism in the liver of affected mice to better understand the underlying mechanism of these phenomena. As model we used a well established adoptive cellular immunotherapy (ADI) system. This involves transfer of in situ activated anti-tumor immune spleen lymphocytes (ISPL) from the tumor-resistant mouse strain B10.D2 (H-2(d), M1s(b)) into 5 Gy sublethally irradiated syngeneic ESb-MP lymphoma-bearing DBA/2 (H-2(d), M1s(a)) mice. Experiments were performed by transfer of ISPL from B10.D2 into DBA/2 tumor-bearing mice (GvL effect on liver metabolism) and into DBA/2 non-tumor-bearing mice (GvH effect on liver metabolism). Our results show that glycogen in hepatocytes decreased dramatically 5 days after ISPL transfer, which coincided with a high increase of large fat granules. 8 days after ISPL transfer, livers started to re-express glycogen and to decrease their lipid content. Normalization of both parameters was seen after day 30. These changes were qualitatively similar in both GvL and GvH. Measurement of activity of the liver marker enzymes, GOT and GPT, in the sera of animals subjected to GvL or GvH, showed peak values also at day 5, coinciding with the loss of glycogen. Quantitative differences were seen, however, in that much higher levels were reached in GvL than in GvH. Immune system recovery from irradiation damage and liver regeneration after immune cell mediated liver damage are likely explanations for the reversibility of the metabolic changes and for the lack of GVH disease and mortality in this new and effective cellular cancer immunotherapy model.

Adhesive function of newcastle-disease virus hemagglutinin in tumor-host interaction

Infection of metastatic lymphoma cells (ESbL) by a low dose of a non-lytic strain of Newcastle disease virus (NDV) leads to viral replication followed by strong cell surface expression of viral antigens, especially hemagglutinin neuraminidase (HN). The expressed HN was functional and facilitated cell-cell interactions and cell attachment. This was shown for NDV infected tumor cells, lymphocytes, fibroblasts and endothelial cells. The interactions could be strongly inhibited by antibodies against the viral HN protein. Increased binding was also seen with HN c-DNA transfectants expressing the HN as the only viral protein. Viral infection did not influence proliferation and lysability of the infected tumor cells. Following intravenous injection of tumor cells, the number of hepatic metastases was significantly reduced when the cells had been pre-infected with NDV. This reduction of metastases correlated with an increased survival time of the animals. As potential mechanisms of these NDV effects we propose augmentation of cell-eel interactions and immune functions and reduction of invasive capacity of NDV infected, as compared to non-infected tumor cells.

Expression of epidermal growth-factor receptor correlates with metastatic potential of 13762nf rat mammary adenocarcinoma cells

Increased expression of EGFR in metastases of human mammary carcinoma as compared to cells of the primary cancer suggests a contribution of EGFR to mammary carcinoma metastasis. To test for a positive correlation, we investigated 13762NF rat mammary adenocarcinoma cloned tumor cell lines of high (MTLn3) or low (MTC) metastatic potential. While MTC cells expressed barely detectable amounts of EGFR, MTLn3 cells expressed readily detectable levels of receptor. This was demonstrated in Northern blot analysis, in immunoprecipitation studies using metabolically labeled whole cell lysates and in Western blot analysis of membrane fractions. Cross-linking of radiolabeled ligand to intact cells identified on both cell types specific binding to a 170 kd protein, however, at much lower levels on low-metastatic MTC cells and not in sufficient amounts to estimate receptor numbers by Scatchard analysis. In contrast, Scatchard plot analysis of I-125-EGF binding to MTLn3 cells revealed the expression of about 10,000 high and 46,000 low affinity sites. Both cell lines expressed the ligand in comparable amounts as was demonstrated by using a specific rat TGFalpha cDNA probe in Northern blot and an antibody recognising membrane bound TGF in FACS analysis. Adhesion of MTC cells to immobilized collagen or fibronectin was rapid reaching 50% after 30 min while control MTLn3 cells demonstrated lower adhesion to collagen. Addition of 10 ng/ml EGF increased the rate and the maximal adhesion of MTLn3 cells to collagen G, while the adhesion kinetics of MTC cells to collagen G or fibronectin were unaffected.

Activated endothelial cells induce apoptosis in lymphoma cells

We have previously shown that the arrest or regression of mouse liver metastases formed by lacZ-transduced ESbL T lymphoma cells (ESbL-lacZ) is associated with the stimulation of nitric oxide (NO) production by liver endothelial cells in sis. Here we studied in vitro the NO-mediated cytotoxicity against ESbL-lacZ target cells using well-characterized bovine endothelial cells (BEG) as effector cells. It was found that the co-culture of BEC with human TNF-alpha caused an increase of NO synthesis which could be completely blocked by the treatment with inducible NO synthase (iNOS) inhibitor N-G-monomethyl-L-arginine (NMMA). Incubation of activated BEC with metastatic lymphoma cells led to the death of the latter cells as evidenced by staining with propidium iodide and FAGS analysis. This cytotoxicity was considerably reduced after pretreatment of BEC with NMMA. Cytotoxic effects were also demonstrated after incubation of tumor cells with NO donor glycerol trinitrate (GTN). Non-activated BEC were not able to produce NO and showed a substantially lower level of cytotoxicity. The anti-tumor cytotoxicity exerted by activated BEC includes the stimulation of apoptosis in metastatic lymphoma cells which is mediated to a large extent by NO. These data reveal a novel role of endothelial cells in the elimination of metastatic cells through the induction of programmed cell death.

In situ downregulation of VLA-4 integrin cell surface expression during lymphoma growth and liver metastasis

The role of VLA-4 integrin in liver metastasis of lymphoma cells was investigated. ESbL-lacZ lymphoma cells in vitro exhibited high surface expression of VLA-4, adhered to CS-1 fibronectin and VCAM-1 and cell adhesion was inhibited by anti-VLA-4 MAb PS/2. When injected in vivo, however, PS/2 did not interfere with spontaneous liver metastasis and had no effect on survival. Ex vivo analysis of VLA-4 surface expression was facilitated by a new reisolation method for tumor and host cells derived from metastatic target organs. Freshly ex vivo isolated tumor cells from metastatic livers revealed VLA-4 surface downregulation as early as 3 days after tumor injection, which continued during the course of metastasis. VLA-4 downregulation in liver metastasis was also seen at the mRNA transcriptional level. Primary tumor cells showed similar VLA-4 downregulation suggesting that the in vivo phenotype was induced by the microenvironment at the primary tumor site. In support of this hypothesis, re-isolated tumor cells from metastatic livers recovered the high VLA-4 expression in host-depleted cell cultures. This study suggests that VLA-4 expression on tumor cells can be modulated in situ during tumor growth and metastasis formation.

Intra-pinna induction of specific antitumor immune T cell functions

Upon inoculation of highly metastatic ESb lymphoma cells into the ear pinna of syngeneic mice a potent specific antitumor immune response is induced which prevents the outgrowth of the tumor cells at this particular site. When the tumor cell inoculated pinna was resected at different times after antigen application, systemic protective antitumor immunity, tested by s.c. tumor challenge 7 days later, could still be induced. This was true even for a situation in which the pinna was resected as early as two hours after tumor cell inoculation. Protective antitumor immunity was found to be even augmented when the pinna was removed three days after tumor cell inoculation as compared to the non-resected situation. Pinna resection had no effect on the induction of a tumor specific cytotoxic T lymphocyte response while resection after 48 h had an augmenting effect on the delayed type hypersensitivity (DTH) response. An explanation for some of these findings was found when lacZ-labeled lymphoma cells were used for single cell detection in tissue sections. As early as 15 min after intra-pinna inoculation disseminated single tumor cells were detected in the local draining lymph node as well as in the spleen. Whether these tumor cells can prime T cells for protective immunity directly or only after processing and presentation by specialized host cells remains to be elucidated.

Tumor response and 4 year survival-data of patients with advanced renal-cell carcinoma treated with autologous tumor vaccine and subcutaneous R-IL-2 and IFN-alpha(2b)

Several forms of immunotherapy are apparently effective in inducing clinical remissions in metastatic renal cancer, but their benefit on survival times have not been demonstrated so far. The present analysis was designed to assess the effects of concomitant application of renal cancer vaccine and cytokines on DTH skin responses to tumor cell challenge, clinical remissions and patients survival. 40 patients with advanced RCC, all with distant metastases in at least one organ, were entered after nephrectomy into a protocol involving multiple vaccinations with Newcastle disease virus (NDV)-infected autologous irradiated tumor cells, with subsequent repetitive 3 bi-weekly cycles of low dose interleukin-2 (r-IL-2) and interferon-alpha(2b)/rIFN-alpha(2) s.c. (1.5 million r-IL-2 Cetus units/m(2)/day and 3 million IFN-alpha IU/m(2)/day). In a pilot study the coadministration of a supplement of r-IL-2 proved to be important for augmentation of DTH responsiveness upon tumor cell challenge. Patients with aneuploid tumors vaccinated without r-IL-2 apparently developed an anergy to the vaccine throughout vaccination. In the main study, of the 40 evaluable RCC patients, 5 exhibited a complete response (CR), 6 displayed a partial remission (PR), 12 showed stable disease (SD, median 25 months) and 17 tumor progression. Survival distribution analysis predicted for all patients with stable disease a median survival of 31 months while CR+PR patients had a median survival >4 years. 23/40 (57.5%) patients (CR, PR and SD) appear to have a significant survival advantage compared to the patients with progressive disease during the treatment period and to a historic reference group. Further data analysis revealed that the number of metastatic sites was predictive of survival characteristics (p<0.05). A marked increase during 3 vaccinations of DTH anti-tumor reactivity predicted a survival advantage (35 vs 14 months), a correlation that was also significant by the Wilcoxon test. While the multi-modality treatment with autologous tumor vaccine and s.c. administration of IL-2 and IFN-alpha appears to be effective in advanced RCC, a randomized trial (ASI-IL-2/IFN-alpha vs IL-2/IFN-alpha without ASI) is now set up to help assess the role of ASI within the combined treatment regimen.

Peripheral immunization against malignant rat glioma can induce effective antitumor immunity in the brain

Using two malignant rat glioma cell lines, we tested to what extent peripheral immunization could affect tumor growth in the brain of syngeneic rats. Peripheral subcutaneous (s.c.) immunization was performed with autologous Newcastle-disease-virus (NDV)-infected or non-infected live tumor cells. Thus immunized rats or non-immunized controls were intracerebrally implanted with increasing numbers of the respective malignant glioma cells. Without immunization the mean survival time after intracerebral implantation of 1x10(4) TZ363 or RG2 glioma cells was 9 and 29 days respectively. After s.c. immunization with either NDV-infected or non-infected TZ363 cells only 25% or less of challenged animals developed tumors in the brain. Immunization with NDV only had no effect. In RG2 glioma, s.c. immunization had no effect on tumor growth in the central nervous system and on survival time, no matter what kind of vaccine was used. These results clearly show, that in principle the efferent arm of the anti-tumor response can be effective accross the blood-brain barrier and extend into the microenvironment of the central nervous system. Whether or not glioma lines can induce this immunity and respond to it, seems to depend on their individual immunobiological characteristics.

Newcastle disease virus induces pro-inflammatory conditions and type I interferon for counter-acting Treg activity

Newcastle disease virus (NDV) is a negative sense RNA paramyxovirus of birds which in human tumor cells, in contrast to human non-tumor cells, has shown replication competence leading to tumor cell death (i.e., tumor selectivity and viral oncolysis). Our study demonstrates that this virus induces high levels of pro-inflammatory cytokines in the bronchial lavage fluid of mice after nasal application and also in vitro in human dendritic cells (DCs). NDV is known as a very efficient inductor of type I interferon (IFN). The presented data show the key role played by the cell surface receptor to type I IFN (IFNAR) but not by the interferon transcription factors IRF-3 and IRF-7 in the induction of the important pro-inflammatory cytokine IL-12 upon transcription of NDV genes in DCs. We show that NDV activates in infected cells the helicase RIG-I. In Tregs, the activation of RIG-I was shown in other studies to inhibit the suppressive function of these cells. We thus conclude that NDV in tumor therapy may help to stimulate T effector cells but also to block Treg cells, thereby alleviating a brake to antitumor activity.

Analysis of three properties of Newcastle disease virus for fighting cancer: tumor-selective replication, antitumor cytotoxicity, and immunostimulation

Newcastle disease virus (NDV), a bird paramyxovirus, is an antitumor agent which has shown benefits to cancer patients. Its antineoplastic efficacy appears to be associated with three properties of the virus: 1. Selective replication in tumor cells. This feature can be studied at the RNA level, for example by RT-PCR, and at the protein level by immunochemistry. 2. Oncolytic properties (of some strains). The use of cultures of tumor cell lines represents a selective model to study direct viral oncolysis at the cellular level. The capacity of NDV to lyse tumor cells can be analyzed in vitro using cytotoxic assays based on the WST1 chemical reagent. The endoplasmic reticulum stress, which is induced by infection with the oncolytic NDV strain MTH-68/H and which plays an important role in the viral oncolytic effects, can be analyzed by Western blotting using specific monoclonal antibodies. Such stress appears as a key component of NDV cytotoxicity. 3. Immunostimulatory capacity. We describe an in vitro test called "Tumor Neutralisation Assay" which allows the analysis of bystander antitumor immune effects induced in human peripheral blood mononuclear cells by NDV. There are two variants, one for oncolytic NDV strains and the other one for nonlytic NDV strains. NDV may use several mechanisms to exert its tumor-killing action: direct cytotoxicity against cancer cells but also nonspecific as well as active-specific antitumor immune responses from the host organism. All the methods described here allow to evaluate the different oncolytic and immunostimulatory capacities of various strains of NDV. They are crucial to harness optimal antitumor activity by appropriate combinations of virus strains and application regimens.

Importance of retinoic acid-inducible gene I and of receptor for type I interferon for cellular resistance to infection by Newcastle disease virus

Newcastle disease virus (NDV) is an avian paramyxovirus with oncolytic properties which shows promising effects in the treatment of cancer. Anti-cancer effects are due to the virus ability: i) to replicate in and kill tumor cells, leading finally to their selective elimination; and ii) to induce the stimulation of antitumor activities in immune cells. NDV does not harm normal cells and has a high safety profile. In this study, we first report a direct correlation between the degree of cell resistance to NDV infection and the cellular expression of the retinoic acid-inducible gene I (RIG-I) which is a cytosolic viral RNA receptor. RIG-I plays an important role in the recognition of and response to infection by RNA viruses. We also demonstrate that impairment of the interferon (IFN) pathway through deletion of the receptor for type I IFN (IFNR1) in primary macrophages leads to NDV replication. In tumor cells, addition of exogenous IFN-α4 is shown to lead to tumor growth reduction and inhibition of viral replication. Finally, increase of the RIG-I concentration of tumor cells via plasmid transfection is shown to be associated with a stronger resistance to NDV infection. These findings shed new light on the crucial role played by the cytosolic receptor RIG-I and the plasma membrane receptor IFNR1 as key molecules to protect cells against infection by NDV.

Important role of interferon regulatory factor (IRF)-3 in the interferon response of mouse macrophages upon infection by Newcastle disease virus

Newcastle disease virus (NDV) is an interesting agent for activating innate immune activity in macrophages including secretion of TNF-α and IFN-α, upregulation of TRAIL and activation of NF-κB and iNOS. However, the molecular mechanism of such cellular activities remains largely unknown. Tumor selectivity of replication of NDV has been described to be linked to deviations in tumor cells of the type I interferon response. We therefore focused on the interferon response to NDV of macrophages as part of innate anti-viral and anti-tumor activity. In particular, we investigated the functional significance of the interferon regulatory factor genes (IRF)-3 and IRF-7. Deletion of the IRF-3 or IRF-7 gene was found to increase susceptibility of mouse macrophages to virus infection. Surprisingly, NDV replicated better in IRF-3 KO than in IRF-7 KO macrophages. Further analysis showed that IRF-3 KO macrophages have a lower basal and NDV-induced RIG-I expression in comparison to IRF-7 KO macrophages. This might explain why, in IRF-3 KO macrophages, the secretion of type I interferons after NDV infection is delayed, when compared to IRF-7 KO and wild-type macrophages. In addition, IRF-3 KO cells showed reduced NDV-induced levels of IRF-7. This effect could be prevented by priming the cells first by interferon-α. Further results indicated that an early production of type I interferon rather than high maximal levels at later time points are important for resistance to infection by NDV. In conclusion, these results demonstrate an important role of IRF-3 for the innate anti-viral response to NDV of mouse macrophages.