Selective gene transfer in vitro to tumor cells via recombinant Newcastle disease virus

Current strategies to circumvent the antiviral immunity to optimize cancer virotherapy

Cancer virotherapy is a paradigm-shifting treatment modality based on virus-mediated oncolysis and subsequent antitumor immune responses. Clinical trials of currently available virotherapies showed that robust antitumor immunity characterizes the remarkable and long-term responses observed in a subset of patients. These data suggest that future therapies should incorporate strategies to maximize the immunotherapeutic potential of oncolytic viruses. In this review, we highlight the recent evidence that the antiviral immunity of the patients may limit the immunotherapeutic potential of oncolytic viruses and summarize the most relevant approaches to strategically redirect the immune response away from the viruses and toward tumors to heighten the clinical impact of viro-immunotherapy platforms.

Employing RNA viruses to fight cancer: novel insights into oncolytic virotherapy

Within recent decades, viruses that specifically target tumor cells have emerged as novel therapeutic agents against cancer. These viruses do not only act via their cell-lytic properties, but also harbor immunostimulatory features to re-direct the tumor microenvironment and stimulate tumor-directed immune responses. Furthermore, oncolytic viruses are considered to be superior to classical cancer therapies due to higher selectivity towards tumor cell destruction and, consequently, less collateral damage of non-transformed healthy tissue. In particular, the field of oncolytic RNA viruses is rapidly developing since these agents possess alternative tumor-targeting strategies compared to established oncolytic DNA viruses. Thus, oncolytic RNA viruses have broadened the field of virotherapy facilitating new strategies to fight cancer. In addition to several naturally occurring oncolytic viruses, genetically modified RNA viruses that are armed to express foreign factors such as immunostimulatory molecules have been successfully tested in early clinical trials showing promising efficacy. This review aims to provide an overview of the most promising RNA viruses in clinical development, to summarize the current knowledge of clinical trials using these viral agents, and to discuss the main issues as well as future perspectives of clinical approaches using oncolytic RNA viruses.

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.

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

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.

Avian paramyxovirus serotype-1: a review of disease distribution, clinical symptoms, and laboratory diagnostics

Avian paramyxovirus serotype-1 (APMV-1) is capable of infecting a wide range of avian species leading to a broad range of clinical symptoms. Ease of transmission has allowed the virus to spread worldwide with varying degrees of virulence depending on the virus strain and host species. Classification systems have been designed to group isolates based on their genetic composition. The genetic composition of the fusion gene cleavage site plays an important role in virulence. Presence of multiple basic amino acids at the cleavage site allows enzymatic cleavage of the fusion protein enabling virulent viruses to spread systemically. Diagnostic tests, including virus isolation, real-time reverse-transcription PCR, and sequencing, are used to characterize the virus and identify virulent strains. Genetic diversity within APMV-1 demonstrates the need for continual monitoring for changes that may arise requiring modifications to the molecular assays to maintain their usefulness for diagnostic testing.

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.

Retargeting of viruses to generate oncolytic agents

Oncolytic virus therapy is based on the ability of viruses to effectively infect and kill tumor cells without destroying the normal tissues. While some viruses seem to have a natural preference for tumor cells, most viruses require the modification of their tropism to specifically enter and replicate in such cells. This review aims to describe the transductional targeting strategies currently employed to specifically redirect viruses towards surface receptors on tumor cells. Three major strategies can be distinguished; they involve (i) the incorporation of new targeting specificity into a viral surface protein, (ii) the incorporation of a scaffold into a viral surface protein to allow the attachment of targeting moieties, and (iii) the use of bispecific adapters to mediate targeting of a virus to a specified moiety on a tumor cell. Of each strategy key features, advantages and limitations are discussed and examples are given. Because of their potential to cause sustained, multiround infection—a desirable characteristic for eradicating tumors—particular attention is given to viruses engineered to become self-targeted by the genomic expression of a bispecific adapter protein.

Use of attenuated paramyxoviruses for cancer therapy

Paramyxoviruses, measles virus (MV), mumps virus (MuV) and Newcastle disease virus (NDV), are well known for causing measles and mumps in humans and Newcastle disease in birds. These viruses have been tamed (attenuated) and successfully used as vaccines to immunize their hosts. Remarkably, pathogenic MuV and vaccine strains of MuV, MV and NDV efficiently infect and kill cancer cells and are consequently being investigated as novel cancer therapies (oncolytic virotherapy). Phase I/II clinical trials have shown promise but treatment efficacy needs to be enhanced. Technologies being developed to increase treatment efficacy include: virotherapy in combination with immunosuppressive drugs (cyclophosphamide); retargeting of viruses to specific tumor types or tumor vasculature; using infected cell carriers to protect and deliver the virus to tumors; and genetic manipulation of the virus to increase viral spread and/or express transgenes during viral replication. Transgenes have enabled noninvasive imaging or tracking of viral gene expression and enhancement of tumor destruction.

[Anti-tumor immunity of Newcastle disease virus HN protein is influenced by differential subcellular targeting]

BACKGROUND AND OBJECTIVE

Hemagglutinin-neuraminidase (HN) protein of newcastle disease virus is an important immunogen for oncolysis. We designed three different expression plasmids encoding the HN protein targeted to different subcellular compartments: cytoplasmic (Cy-HN), secreted (Sc-HN) and membrane-anchored (M-HN). On the basis of antitumor effect in vitro, the aim of this study is to investigate the anti-tumor immunity effect of HN protein in vivo.

METHODS

In the present study, we developed a mouse model in order to evaluate the anti-tumor effect of the intratumorally injected modified HN proteins and the anti-tumor immunity by lymphocyte proliferative response and CTL activity test.

RESULTS

Although all three DNA constructs elicited an immune response, tumor-bearing mice intratumorally injected with M-HN demonstrated a significantly better anti-tumor effect than those injected with Cy-HN or Sc-HN (Day 18: P=0.022; Day 21: P<0.01). It also showed that this anti-tumor effect was mediated by higher lymphocyte proliferative response and CTL activity in mice intratumorally injected with M-HN [M-HN vs Cy-HN, P=0.019; M-HN vs Sc-HN, P=0.043; M-HN vs pcDNA3.1(+), P<0.01].

CONCLUSION

The anti-tumor immunity of Newcastle disease virus HN protein is influenced by differential subcellular targeting. The membrane-anchored form of the HN protein appears to be an ideal candidate to improve the specific cellular immunity.

The anti-tumor effect of Newcastle disease virus HN protein is influenced by differential subcellular targeting

BACKGROUND

Immunotherapy is emerging as a major player in the current standard of care for aggressive cancers such as non-small cell lung cancer (NSCLC). The Newcastle disease virus with its tumor-specific replicative and oncolytic abilities is a promising immunotherapeutic candidate. A DNA vaccine expressing the major immunogenic hemagglutinin-neuraminidase (HN) protein of this virus has shown promising results as an immunotherapeutic agent.

METHODS

In the present study, three different DNA vaccine constructs encoding differentially targeted HN proteins (cytoplasmic or Cy-HN, secreted or Sc-HN and membrane-anchored or M-HN) were generated to evaluate their anti-tumor effect in vitro and in vivo.

RESULTS

Although all three DNA constructs elicited an immune response, tumor-bearing mice intratumorally injected with M-HN demonstrated a significantly better anti-tumor effect than those injected with Cy-HN or Sc-HN. We also showed that this anti-tumor effect was mediated by higher lymphocyte proliferative response and CTL activity in mice intratumorally injected with M-HN.

CONCLUSION

The membrane-anchored form of the HN protein appears to be an ideal candidate to develop as an immunotherapeutic agent for NSCLC.

Newcastle disease virus represses the activation of human hepatic stellate cells and reverses the development of hepatic fibrosis in mice

BACKGROUND/AIMS

Activated hepatic stellate cells (HSCs) are the crucial factor responsible for liver fibrosis and involved in development of hepatocellular carcinoma (HCC) by interaction with tumour cells. Newcastle disease virus (NDV) has the oncolytic characteristics of intrinsically selective replication in neoplasia cells and transformed cells. But, NDV replication in HSCs and effects on hepatic fibrosis have not been reported.

METHODS

We detected the effect of conditioned medium (CM) from human HCC cells on the activation of human HSC line, LX-2 by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and reverse transcriptase-polymerase chain reaction (RT-PCR). The replication of NDV was evaluated in LX-2 cells and primary-cultured mouse HSCs by flow cytometry or by a fluorescence microscope. Indices for hepatic fibrosis were determined in HSCs and a hepatic fibrosis mouse model by gelatin zymography, RT-PCR, Western blot and Sirius red staining after NDV infection. Colocalization of NDV virions and alpha-smooth muscle actin (alpha-SMA) were detected by double immunofluorescence staining. Detection of apoptosis was carried out in liver tissues of NDV-treated mice by the TdT-mediated dUTP nick-end labelling assay.

RESULTS

Tumour-CM and transforming growth factor-beta1 (TGF-beta1) could promote the proliferation and activation of LX-2 cells, indicated by the enhanced expression of alpha-SMA, collagen I, tissue inhibitor of metalloproteinase (TIMP)-1 and TGF-beta1. Activated HSCs facilitated the replication of NDV, thereby repressing the secretion of MMP, the expression of these indices for hepatic fibrosis and the expression of alpha-SMA and collagen fibrils in hepatic fibrosis of the mouse induced by carbon tetrachloride.

CONCLUSIONS

HCC cells promote the activation of HSCs and NDV attenuates the activation and represses the hepatic fibrosis by selective replication in activated HSCs.

Newcastle disease virus: a promising vector for viral therapy, immune therapy, and gene therapy of cancer

This review deals with the avian paramyxovirus Newcastle disease virus (NDV) and describes properties that explain its oncolytic activity, its tumor-selective replication behavior, and its immune-stimulatory capacity with human cells. The strong interferon response of normal cells upon contact with NDV appears to be the basis for the good tolerability of the virus in cancer patients and for its immune stimulatory properties, whereas the weak interferon response of tumor cells explains the tumor selectivity of replication and oncolysis. Various concepts for the use of this virus for cancer treatment are pointed out and results from clinical studies are summarized. Reverse genetics technology has made it possible recently to clone the genome and to introduce new foreign genes thus generating new recombinant viruses. These can, in the future, be used to transfer new therapeutic genes into tumors and also to immunize against new emerging pathogens. The modular nature of gene transcription, the undetectable rate of recombination, and the lack of a DNA phase in the replication cycle make NDV a suitable candidate for the rational design of a safe and stable vaccine and gene therapy vector.

Generation of a recombinant oncolytic Newcastle disease virus and expression of a full IgG antibody from two transgenes

The most advanced oncolytic Newcastle disease virus (NDV) strains that are used in clinical trials for the treatment of cancer are wild-type mesogenic strains. These virus strains have an inherent, nongenetically engineered, oncolytic activity and selectively replicate in tumor cells but not in normal human cells. To date no investigations have been performed with genetically engineered mesogenic NDV regarding the oncolytic activity. We describe here the generation of recombinant viruses of the mesogenic naturally oncolytic NDV strain MTH68. We show that not only one, but also two additional transgenes coding for amino-acid chains with a molecular weight of 25 and 50 kDa can be inserted into the viral genome without affecting viral growth, oncolytic potency or tumor-selective replication of the virus. Transgenic expression of the heavy and light chains of a monoclonal antibody, as separate additional transcriptional cassettes, leads to the expression of full immunoglobulin G (IgG) monoclonal antibody by recombinant NDV. Infection of tumor cells with antibody-transgenic viruses results in the efficient production and secretion of a functional full size IgG antibody by the tumor cells, that specifically binds to its target-antigen in tumor tissue. This approach will allow to combine the advantages of oncolytic RNA viruses and monoclonal antibodies in a single powerful anticancer agent with improved or even new therapeutic properties.

Expression of transgenes from newcastle disease virus with a segmented genome

Paramyxoviruses belong to the Paramyxoviridae family of the order Mononegavirales. They have a nonsegmented negative-stranded RNA genome and can cause a number of diseases in humans and animals. We generated a recombinant Newcastle disease virus (NDV) possessing a two-segmented genome. Each genomic segment is flanked by authentic NDV 3' and 5' noncoding termini allowing for efficient replication and transcription. A reporter gene encoding green fluorescent protein (GFP) was inserted into one segment, and a red fluorescent protein dsRed gene was inserted into the other segment in order to easily detect the replication and transcription of segments in infected cells. The rescued viruses grew well and were stable in embryonated chicken eggs over multiple passages. We were able to detect the expression of both reporter genes in the same cell infected with the virus possessing a segmented genome, and viral particles can contain either one or two types of RNA segments. We also rescued a two-segmented virus expressing GFP and the severe acute respiratory syndrome-associated coronavirus spike S protein, which is about 200 kDa. The chimeric virus extends the coding capacity of NDV by 30%, suggesting that the two-segmented NDV can be used for development of vaccines or gene therapy vectors carrying long and multiple transgenes.

Generation of a velogenic Newcastle disease virus from cDNA and expression of the green fluorescent protein

Newcastle disease virus (NDV) is a pathogen that is important in the poultry industry worldwide. Specifically, the virulent (velogenic) NDV is a particular threat because it has now occurred frequently worldwide. The outbreaks caused by highly virulent NDV in waterfowl and especially in goose flocks, have led to greater concern in recent years as aquatic birds were previously resistant to most virulent NDV strains from chickens. The molecular determinants of host tropism, virulence and emergence of NDV isolated from diseased goose flocks are poorly understood. In the present study, we rescued a highly virulent NDV isolated from a goose using the reverse genetics approach. Infectious virus was successfully generated by cotransfection of a full-length cDNA clone of the NDV strain ZJ1 with helper plasmids. The recombinant NDV was indistinguishable from the parental wild-type virus with respect to its growth kinetics in cell culture as well as its biological properties. A recombinant NDV expressing green fluorescent protein (GFP) was generated, and GFP was subsequently detected in cells and various organs from the infected chickens.

Tumor selective replication of Newcastle disease virus: association with defects of tumor cells in antiviral defence

To investigate tumor-selective viral replication, we compared several tumorigenic human cell lines to nontumorigenic human cells from the blood for the sensitivity to become infected by a recombinant lentogenic strain of Newcastle Disease Virus (NDV) with incorporated transgene EGFP (NDFL-EGFP). Although fluorescence signals in nontumorigenic cells were only weak or missing completely, a massive and long-lasting transgene-expression was observed in all tumor cell lines. The majority of tumor cells (50-95%) could be infected, and viral replication was associated with an increase in the cell surface density of viral antigens. To clarify the underlying mechanism of the observed difference in virus susceptibility we examined the kinetics of interferon-induced antiviral enzymes because NDV is a strong type-I interferon inducer. This analysis revealed several defects of tumor cells in their antiviral defence responses: They showed no response to UV-inactivated NDV, whereas nontumorigenic cells reacted with induction of high-levels of the antiviral enzymes PKR and MxA. Upon coincubation with live NDV, tumor cells showed a delayed response in the increased expression of the antiviral enzymes in comparison with PBMC. In nontumorigenic cells the replication cycle of NDV stopped after the production of positive-strand RNA, while tumor cells continued in the replication cycle and copied viral genomes 10-50 hr after infection. These results can explain the tumor selective replication behavior of this interesting antineoplastic virus.