Apoptosis in chicken embryo fibroblasts caused by Newcastle disease virus

Oncolytic effects of Hitchner B1 strain of newcastle disease virus against cervical cancer cell proliferation is mediated by the increased expression of cytochrome C, autophagy and apoptotic pathways

Newcastle disease virus (NDV) is a potential oncolytic virus for the cancer treatment due to its ability to replicate in tumor cells. The aim of this study was to evaluate the in vitro anticancer properties of Hitchner B1 (HB1) strain of NDV on TC-1 cell line and underlying molecular mechanisms. The cytolytic effects of oncolytic HB1 strain of NDV was determined by lactate dehydrogenase (LDH) release assay. Apoptosis, intracellular reactive oxygen species (ROS) levels, cleaved caspase-3 and autophagy were evaluated by flow cytometry. Cytochrome-C and survivin protein levels were distinguished by Enzyme-Linked Immunosorbent Assay (ELISA). Our results from LDH method showed that the viability of the TC-1 cell line following HB1 NDV infection was dose-dependent and decreased significantly with increasing the dose of HB1 NDV infection (MOIs: 5, 10, and 15). Other evaluations also revealed that HB1 strain of NDV potentially led to the ROS production, and apoptosis and autophagy induction in TC-1 cell line in a dose-dependent manner. The in vitro experiments also presented that NDV treatment significantly up-regulated the expression of cytochrome-C and down-regulated the expression of survivin, as detected by ELISA assay. Our results confirmed that the HB1 NDV could be introduced as a powerful candidate for the therapy of cervical cancer. However, further examinations are needed to explain the underlying mechanisms of the HB1 NDV against TC-1 cell line and cervical cancer.

Syncytia Formation in Oncolytic Virotherapy

Oncolytic virotherapy uses replication-competent virus as a means of treating cancer. Whereas this field has shown great promise as a viable treatment method, the limited spread of these viruses throughout the tumor microenvironment remains a major challenge. To overcome this issue, researchers have begun looking at syncytia formation as a novel method of increasing viral spread. Several naturally occurring fusogenic viruses have been shown to possess strong oncolytic potential and have since been studied to gain insight into how this process benefits oncolytic virotherapy. Whereas these naturally fusogenic viruses have been beneficial, there are still challenges associated with their regular use. Because of this, engineered/recombinant fusogenic viruses have also been created that enhance nonfusogenic oncolytic viruses with the beneficial property of syncytia formation. The purpose of this review is to examine the existing body of literature on syncytia formation in oncolytics and offer direction for potential future studies.

Newcastle disease virus-induced autophagy mediates antiapoptotic signaling responses in vitro and in vivo

In this study, we investigated the role of autophagy and apoptosis in Newcastle disease virus (NDV)-infected chicken cells and tissues. NDV-infected and starvation-induced chick embryo fibroblasts (CEF) cells showed higher autophagosome formation than mock-infected CEF cells on transmission electron microscopy. The NDV-infected CEF cells showed enhanced conversion of microtubule-associated protein 1 light chain 3-I (LC3-I) to LC3-II and degradation of p62/SQSTM1. The diminished conversion of LC3-I to LC3-II and cleaved caspase 3 and poly (ADP-ribose) polymerase (PARP) in ultraviolet-inactivated NDV-infected cells suggested that autophagosome formation was necessary for NDV replication. Inhibition of autophagy by chloroquine (CQ) enhanced apoptosis resulting in increased cleavage of caspase 3 and PARP and AnnexinV/propidium iodide staining. Autophagy induction by rapamycin resulted in upregulation of all autophagy-related genes except Beclin 1, anti-apoptosis factors, and proinflammatory cytokines in the NDV-infected spleen and lung tissues. Subsequently, decreased apoptosis was observed in NDV-infected spleens and lungs than mock-infected organs. The pan-caspase inhibitor ZVAD-FMK promoted conversion of LC3-I to LC3-II, the degradation of p62/SQSTM1, NDV replication and cell viability by inhibiting apoptosis. Our study demonstrates that apoptosis inhibition enhances autophagy and promoted cell survival and NDV replication.

Interferon regulatory factor 7- (IRF7-) mediated immune response affects Newcastle disease virus replication in chicken embryo fibroblasts

Interferon regulatory factor 7 (IRF7) is essential for the induction of an antiviral response. Previous studies have shown that virus replication causes the activation or expression of Type I interferon (IFN) in cells, which further activates IFN-stimulated genes (ISGs) to retard virus growth. In this study, after infection of chicken embryo fibroblasts (CEFs) with the lentogenic Newcastle disease virus (NDV) strain LaSota or the velogenic NDV strain GM, the mRNA and protein levels of IRF7 showed a significant increase, and part of the IRF7 protein was translocated from the cytoplasm to the nucleus. In order to further explore the effect of IRF7-mediated innate immune response on the replication of NDV in CEFs, the mRNA levels of IFN-α, IFN-β and STAT1 were measured and the replication kinetics of NDV determined. The results showed that specific siRNA could inhibit the expression of IRF7 and limit the mRNA level of IFN-α, IFN-β and STAT1 and, accordingly, the replication kinetics of both NDVs were enhanced after the inhibition of IRF7. In conclusion, IRF7 is an important nuclear transcription factor for the induction of Type I IFNs during the antiviral response, which can affect the replication of NDV and spread to CEFs in the early phase of viral infection.

Screening and identification of differentially expressed genes from chickens infected with Newcastle disease virus by suppression subtractive hybridization

Newcastle disease is an important viral infectious disease caused by Newcastle disease virus (NDV), which leads to severe economic losses in the poultry industry worldwide. The molecular mechanisms involved in the pathogenesis of NDV and the host-directed antiviral responses remain poorly understood. In this study, we screened and identified the differentially expressed transcripts from chicken spleen 36 h post NDV infection using suppression subtractive hybridization (SSH). From the SSH library, we obtained 140 significant differentially expressed sequence tags (ESTs), which could be divided into three categories: high homology genes (58), high homology ESTs (62) and novel ESTs (20). The 58 high homology genes could be grouped into nine clusters based on the best known function of their protein products, which involved signalling transduction (HSPC166, PDE7B, GRIA4, GARNL1), transcriptional regulation (ANP32A, LOC423724, SATB1, QKI, ETV6), cellular molecular dynamics (MYLK, MYO7A, DCTN6), cytoskeleton (LAMA4, LAMC1, COL4A1), stress response (DNAJC15, CIRBP), immune response (TIA1, TOX, CMIP), metabolism (RPS15A, RPL32, GLUT8, CYPR21, DPYD, LOC417295), oxidation-reduction (TXN, MSRB3, GCLC), and others. In addition, we found that the 20 novel ESTs provide a clue for the discovery of some new genes associated with infection. In summary, our findings demonstrate previously unrecognized changes in gene transcription that are associated with NDV infection in vivo, and many differentially expressed genes identified in the study clearly merit further investigation. Our data provide new insights into better understanding the molecular mechanism of host-NDV interaction.

Newcastle disease virus-induced cytopathic effect in infected cells is caused by apoptosis

The velogenic Newcastle disease virus (NDV) causes highly infectious and economically significant Newcastle disease (ND) in birds of various species. In cell culture NDV induces cytopathic effect (CPE) characterized by rounding, vacuolation, syncytia formation and cell death. Aside from cell to cell fusion caused by the F and HN glycoprotein of the virus molecular events leading to cell death are not known. In the current study, NDV-infected Vero cells, at 48 h p.i., showed nuclear condensation, cytoplasm blebbing, DNA fragmentation, and phosphatidylserine translocation to the cell surface. In addition, virus-infected cells demonstrated decreased DNA content and an increased Bax to Bcl-2 ratio, p53 level and caspase 3, 8, 9 expression compared to mock-infected cells. Based on these results, it was concluded that CPE in NDV-infected cells was caused by to the induction of apoptosis with the involvement of p53 and the Bax, dependent apoptotic pathways.

Induction of apoptosis in Vero cells by Newcastle disease virus requires viral replication, de-novo protein synthesis and caspase activation

Newcastle disease virus causes (NDV) apoptotic death of infected cells. In the present study, the stimulus that provoked the induction of apoptosis in infected cells was examined. Vero cells infected with NDV developed apoptosis as characterized by DNA fragmentation and decreased DNA content. In presence of ammonium chloride, infected cells did not show reduced DNA content indicating the requirement of virus entry for the induction of apoptosis. UV-inactivated NDV did not induce apoptosis in cells suggesting the need of virus replication. Although cycloheximide blocked NDV-induced apoptosis, actinomycin-D did not, suggesting that de-novo viral protein synthesis was critical for the induction of apoptosis. In addition, activation of caspases was also detected by flowcytometry, indirect fluorescent and colorimetric assays. Based on the results, it was concluded that NDV-induced apoptosis in Vero cells required virus replication, de-novo protein synthesis and caspase activation.

HN protein of Newcastle disease virus causes apoptosis in chicken embryo fibroblast cells

Newcastle disease virus (NDV), an avian paramyxovirus, induces apoptosis in chicken embryo fibroblast (CEF) cells. In the present investigation, the ability of haemagglutinin-neuraminidase (HN) protein of NDV to cause apoptosis in CEF cells was examined. The results revealed that cells expressing the HN protein demonstrated decreased DNA content, phosphatidylserine exposure and increased cytoplasmic vacuolation. Up-regulation of caspase-1, -9, -8, -3, loss of mitochondrial transmembrane potential and an increase in oxidative stress were also observed in cells expressing the HN protein. Based on the above results it can be concluded that HN protein of NDV causes apoptosis in CEF cells.

p53-independent endoplasmic reticulum stress-mediated cytotoxicity of a Newcastle disease virus strain in tumor cell lines

While Newcastle disease virus (NDV) causes serious infections in birds, it is apparently nonpathogenic in mammalian species, including humans. Previous observations and small-scale clinical trials indicated that NDV exerts oncolytic effects. Isolates of NDV were found to have selective affinity to transformed cells. We previously showed that the attenuated NDV strain MTH-68/H causes apoptotic cell death in cultures of PC12 rat pheochromocytoma cells. The aim of the present study was to extend MTH-68/H cytotoxicity testing with human tumor cell lines and to analyze certain biochemical aspects of its oncolytic effect. MTH-68/H was found to be able to kill a wide range of transformed cells by apoptosis. While caspase-8 and caspase-9 are not involved in MTH-68/H-induced apoptosis, activation of caspase-3 and caspase-12 was detected in virus-infected PC12 cells. A human glioblastoma cell line with repressible expression of the p53 protein did not show any difference in MTH-68/H sensitivity in its p53-expressing and p53-depleted states, indicating that the apoptotic process induced by MTH-68/H does not depend on p53. Apoptosis was accompanied by virus replication in two tumor cell lines tested (PC12 cells and HeLa human cervical cells), and signs of endoplasmic reticulum stress (phosphorylation of protein kinase R-like endoplasmic reticulum kinase and eIF2alpha) were also detected in transformed cells. In contrast, proliferation of nontransformed mouse and rat fibroblast cell lines and human primary fibroblasts was not affected by MTH-68/H treatment. MTH-68/H thus selectively kills tumor cell cultures by inducing endoplasmic reticulum stress leading to p53-independent apoptotic cell death.

Transcriptional response of avian cells to infection with Newcastle disease virus

Newcastle disease virus (NDV) causes widespread disease in poultry and wild-birds throughout the world. cDNA microarray analysis was used to examine the effect of NDV infection on host cell transcription. The results show that NDV infection causes an apparent suppression of the interferon response genes during the early stages of infection. In addition, the results reveal transcriptional silencing of cytoskeletal proteins such as the alpha, beta, and gamma types of actin, and a downregulation of the thioredoxin gene, a likely mediator of apoptosis with possible implications in NDV pathogenesis. Comparative analyses show that a majority of genes that were transcriptionally regulated during infection with another common respiratory pathogen of poultry, the avian pneumovirus, remained unaltered during NDV infection, suggesting that even phylogenetically related viruses elicit unique or "signature" patterns of host transcriptional profiles during infection of host cells.

MTH-68/H oncolytic viral treatment in human high-grade gliomas

Application of virus therapy to treat human neoplasms has over a three decade history. MTH-68/H, a live attenuated oncolytic viral strain of the Newcastle disease virus, is one of the viruses used in the treatment of different malignancies. Here we report on the administration of MTH-68/H to patients with glioblastoma multiforme, the most common and most aggressive neuroectodermal neoplasm with a poor prognosis, averaging six months to a year. Four cases of advanced high-grade glioma were treated with MTH-68/H after the conventional modalities of anti-neoplastic therapies had failed. This treatment resulted in survival rates of 5-9 years, with each patient still living today. Against all odds, each patient resumed a lifestyle that resembles their previous daily routines and enjoys a good quality of life, Each of these patients has regularly received MTH-68/H as their sole form of onco-therapy for a number of years now without interruption.

Newcastle disease virus V protein is a determinant of host range restriction

It has been demonstrated that the V protein of Newcastle disease virus (NDV) functions as an alpha/beta interferon (IFN-alpha/beta) antagonist (M. S. Park, M. L. Shaw, J. Muñoz-Jordan, J. F. Cros, T. Nakaya, N. Bouvier, P. Palese, A. García-Sastre, and C. F. Basler, J. Virol. 77:1501-1511, 2003). We now show that the NDV V protein plays an important role in host range restriction. In order to study V functions in vivo, recombinant NDV (rNDV) mutants, defective in the expression of the V protein, were generated. These rNDV mutants grow poorly in both embryonated chicken eggs and chicken embryo fibroblasts (CEFs) compared to the wild-type (wt) rNDV. However, insertion of the NS1 gene of influenza virus A/PR8/34 into the NDV V(-) genome [rNDV V(-)/NS1] restores impaired growth to wt levels in embryonated chicken eggs and CEFs. These data indicate that for viruses infecting avian cells, the NDV V protein and the influenza NS1 protein are functionally interchangeable, even though there are no sequence similarities between the two proteins. Interestingly, in human cells, the titer of wt rNDV is 10 times lower than that of rNDV V(-)/NS1. Correspondingly, the level of IFN secreted by human cells infected with wt rNDV is much higher than that secreted by cells infected with the NS1-expressing rNDV. This suggests that the IFN antagonist activity of the NDV V protein is species specific. Finally, the NDV V protein plays an important role in preventing apoptosis in a species-specific manner. The rNDV defective in V induces apoptotic cell death more rapidly in CEFs than does wt rNDV. Taken together, these data suggest that the host range of NDV is limited by the ability of its V protein to efficiently prevent innate host defenses, such as the IFN response and apoptosis.

Newcastle disease virus-induced apoptosis in PC12 pheochromocytoma cells

The avian paramyxovirus Newcastle disease virus (NDV) causes severe infections in birds. It is essentially nonpathogenic in rodents and human beings but was found to have an oncolytic potential against certain types of human malignancies. An attenuated NDV vaccine (designated MTH-68/H) was found to cause regression of various human tumors, but the mechanism of its oncolytic action and its selectivity toward malignant cells remain poorly understood. NDV was reported to cause apoptotic death in several avian cultured cell types. Programmed cell death may thus be the basis for the oncolytic effect of NDV vaccines. To test this possibility, we chose the PC12 rat pheochromocytoma cell line, a widely used model system for apoptosis. The MTH-68/H vaccine was found to cause apoptotic death of PC12 cells in a dose-dependent manner. A brief exposure of cells to the virus was found to trigger the apoptotic response. Cell death induced by the vaccine was not accompanied by significant alterations in the major mitogen-activated protein kinase pathways of these cells. Apoptotic DNA fragmentation was not affected by stimulating growth factor pathways or signaling mechanisms mediated by protein kinase C or the second messenger, calcium. In contrast, stimulation of protein kinase A by cyclic adenosine monophosphate analogs gave partial protection against the virus. PC12 cells thus provide a useful model system to study the effects of NDV on cell survival at the molecular level.

Evaluation of E1B gene-attenuated replicating adenoviruses for cancer gene therapy

Gene-attenuated replication-competent adenoviruses are emerging as a promising new modality for the treatment of cancer. For the aim of improving adenoviral vectors for cancer gene therapy, we have constructed genetically attenuated adenoviral vectors with different combinations of E1B genes and investigated the possibility of enhanced oncolytic and replication effects of these engineered replication-competent adenoviruses. We show here that the cytolytic potency of each gene-attenuated replicating adenovirus differed significantly depending on the presence or deletion of E1B 55 kDa and E1B 19 kDa function. More specifically, among the constructed vectors (Ad-deltaE1B19, Ad-deltaE1B55, Ad-deltaE1B19/55, and Ad-wt), E1B 19 kDa-inactivated adenovirus (Ad-deltaE1B19) was the most potent against all tumor cells tested, inducing the largest-sized plaques and marked CPE. Further, cells infected with either Ad-deltaE1B19 or E1B19/55 kDa-deleted adenovirus (Ad-deltaE1B19/55) showed complete cell lysis with disintegrated cellular structure, whereas cells infected with Ad-wt maintained intact cellular and nuclear membrane with properly structured organelles. TUNEL and DNA fragmentation assay also revealed that the Ad-deltaE1B19 or Ad-deltaE1B19/55 adenovirus-infected cells showed more profound induction of apoptosis in comparison to wild-type adenovirus-infected cells. The presence of E1B 55 kDa gene was required for efficient viral replication and deletion of E1B 19 kDa function in replicating adenovirus-induced apoptosis, leading to increased cytopathic effects. Moreover, Ad-deltaE1B19 adenovirus showed a better antitumor effect than other E1B-attenuated adenoviruses. Taken together, the replicating adenoviruses deleted in E1B 19 kDa function may serve as an improved vector for anticancer gene therapy in combination with apoptosis-inducing modalities such as chemotherapeutic agents and radiation therapy.

Murine polyomavirus infection of 3T6 mouse cells shows evidence of predominant necrosis as well as limited apoptosis

The current study was developed to determine if polyomavirus infected 3T6 mouse cells evoked an apoptotic or a necrotic mechanism during infection. Infected cells were analyzed by flow cytometry, transmission electron microscopy (TEM), DNA electrophoresis and by measuring caspase-3 enzymatic activity. Infected cells that were analyzed at 72 h post-infection showed the following: flow cytometry analysis revealed a 5% increase in apoptotic cells and a 46% increase in necrotic cells when compared to uninfected cells; electron microscopy showed 10% cells with characteristic apoptotic morphology and 40% with necrotic appearance; caspase-3 activity was found to increase two fold when compared to uninfected cells and DNA fragmentation (laddering) was clearly evident late in infection. It was concluded that infected cells predominantly showed necrosis, although some cells showed apoptosis in late infection. Recombinant capsid-like particles composed of the polyomavirus structural proteins were not able to induce cell death.

Growth of Newcastle disease virus in chicken macrophages

Chicken macrophages were isolated from chicken peripheral blood, cultured in vitro, and infected with Newcastle disease virus (NDV) after reaching semiconfluence. Infected macrophages supported the growth and replication of NDV. Virus-infected macrophages exhibited features of apoptosis as determined by agarose gel electrophoresis, thymidine release assays and flow cytometry. Electron microscopical examination also showed the appearance of intact virus particles, fragmented chromatin and apoptotic bodies. This evidence demonstrates that NDV infection of chicken macrophages causes chicken macrophages to undergo apoptosis.

Newcastle disease virus-induced functional impairments and biochemical changes in chicken heterophils

The GB strain of Newcastle disease virus (NDV) is used to infect chicken heterophils in vitro. Heterophils have a decreased ability to phagocytize bacteria 3 h after infection, and those that did engulfed fewer bacteria relative to non-infected heterophils. Infected heterophils have a decreased H2O2 production as shown by flow cytometry, but an increased nitric oxide production, suggesting that NDV can stimulate heterophils to produce and/or utilize nitrogen intermediates but not oxygen intermediates. DNA extracted from the infected heterophils shows a marked fragmentation, suggesting that NDV infection may cause heterophils to undergo apoptosis.