ISG12a mediates cell response to Newcastle disease viral infection

Molecular Circuits of Immune Sensing and Response to Oncolytic Virotherapy

Oncolytic virotherapy is a promising immunotherapy approach for cancer treatment that utilizes viruses to preferentially infect and eliminate cancer cells while stimulating the immune response. In this review, we synthesize the current literature on the molecular circuits of immune sensing and response to oncolytic virotherapy, focusing on viral DNA or RNA sensing by infected cells, cytokine and danger-associated-signal sensing by neighboring cells, and the subsequent downstream activation of immune pathways. These sequential sense-and-response mechanisms involve the triggering of molecular sensors by viruses or infected cells to activate transcription factors and related genes for a breadth of immune responses. We describe how the molecular signals induced in the tumor upon virotherapy can trigger diverse immune signaling pathways, activating both antigen-presenting-cell-based innate and T cell-based adaptive immune responses. Insights into these complex mechanisms provide valuable knowledge for enhancing oncolytic virotherapy strategies.

ISG12a promotes immunotherapy of HBV-associated hepatocellular carcinoma through blocking TRIM21/AKT/β-catenin/PD-L1 axis

Hepatitis B virus (HBV) infection generally elicits weak type-I interferon (IFN) immune response in hepatocytes, covering the regulatory effect of IFN-stimulated genes. In this study, low level of IFN-stimulated gene 12a (ISG12a) predicted malignant transformation and poor prognosis of HBV-associated hepatocellular carcinoma (HCC), whereas high level of ISG12a indicated active NK cell phenotypes. ISG12a interacts with TRIM21 to inhibit the phosphorylation activation of protein kinase B (PKB, also known as AKT) and β-catenin, suppressing PD-L1 expression to block PD-1/PD-L1 signaling, thereby enhancing the anticancer effect of NK cells. The suppression of PD-1-deficient NK-92 cells on HBV-associated tumors was independent of ISG12a expression, whereas the anticancer effect of PD-1-expressed NK-92 cells on HBV-associated tumors was enhanced by ISG12a and treatments of atezolizumab and nivolumab. Thus, tumor intrinsic ISG12a promotes the anticancer effect of NK cells by regulating PD-1/PD-L1 signaling, presenting the significant role of innate immunity in defending against HBV-associated HCC.

Longitudinal home self-collection of capillary blood using homeRNA correlates interferon and innate viral defense pathways with SARS-CoV-2 viral clearance

Blood transcriptional profiling is a powerful tool to evaluate immune responses to infection; however, blood collection via traditional phlebotomy remains a barrier to precise characterization of the immune response in dynamic infections (e.g., respiratory viruses). Here we present an at-home self-collection methodology, homeRNA, to study the host transcriptional response during acute SARS-CoV-2 infections. This method uniquely enables high frequency measurement of the host immune kinetics in non-hospitalized adults during the acute and most dynamic stage of their infection. COVID-19+ and healthy participants self-collected blood every other day for two weeks with daily nasal swabs and symptom surveys to track viral load kinetics and symptom burden, respectively. While healthy uninfected participants showed remarkably stable immune kinetics with no significant dynamic genes, COVID-19+ participants, on the contrary, depicted a robust response with over 418 dynamic genes associated with interferon and innate viral defense pathways. When stratified by vaccination status, we detected distinct response signatures between unvaccinated and breakthrough (vaccinated) infection subgroups; unvaccinated individuals portrayed a response repertoire characterized by higher innate antiviral responses, interferon signaling, and cytotoxic lymphocyte responses while breakthrough infections portrayed lower levels of interferon signaling and enhanced early cell-mediated response. Leveraging cross-platform longitudinal sampling (nasal swabs and blood), we observed that IFI27, a key viral response gene, tracked closely with SARS-CoV-2 viral clearance in individual participants. Taken together, these results demonstrate that at-home sampling can capture key host antiviral responses and facilitate frequent longitudinal sampling to detect transient host immune kinetics during dynamic immune states.

Knockdown of NEAT1 restricts dengue virus replication by augmenting interferon alpha-inducible protein 27 via the RIG-I pathway

The lncRNA NEAT1 plays a vital role in mitochondrial function and antiviral response. We have previously identified NEAT1 as dysregulated lncRNAs and found an inverse correlation with interferon alpha-inducible protein 27 (IFI27) expression associated with developing dengue severity. However, the role of NEAT1 in dengue virus (DV) infection remains elusive. Here, we undertook a study to evaluate the functional consequences of NEAT1 and IFI27 modulation on antiviral response and viral replication in dengue infection. We observed that the knockdown of NEAT1 augmented IFI27 expression and antiviral response via the RIG-I pathway. Increased antiviral response leads to a decrease in dengue viral replication. Further study suggested that the knockdown of IFI27 augmented expression of the activating transcription factor 3 (ATF3), a negative regulator of antiviral response, and increased dengue virus replication suggesting an important role played by IFI27 in mediating antiviral response. RNA sequencing study confirmed several mitochondrial genes significantly altered upon knockdown of NEAT1 in DV-infected cells. We further verified the effect of NEAT1 knockdown on mitochondrial functions. We observed a reduced level of phospho-DRP1(S616) expression along with elongated mitochondria in DV2-infected cells. Further, NEAT1 knockdown or ectopic expression of IFI27 increased mitochondrial ROS production and cell death via activation of caspase 3. Our study points to the crucial role of NEAT1 and IFI27 in mediating antiviral response and mitochondrial dysfunction in dengue infection.

The role of interferons in ovarian cancer progression: Hinderer or promoter?

Ovarian cancer (OC) is a common gynecologic malignancy with poor prognosis and high mortality. Changes in the OC microenvironment are closely related to the genesis, invasion, metastasis, recurrence, and drug-resistance. The OC microenvironment is regulated by Interferons (IFNs) known as a type of important cytokines. IFNs have a bidirectional regulation for OC cells growth and survival. Meanwhile, IFNs positively regulate the recruitment, differentiation and activation of immune cells. This review summarizes the secretion and the role of IFNs. In particular, we mainly elucidate the actions played by IFNs in various types of therapy. IFNs assist radiotherapy, targeted therapy, immunotherapy and biotherapy for OC, except for some IFN pathways that may cause chemo-resistance. In addition, we present some advances in OC treatment with the help of IFN pathways. IFNs have the ability to powerfully modulate the tumor microenvironment and can potentially provide new combination strategies for OC treatment.

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.

MiR-942-5p targeting the IFI27 gene regulates HCT-8 cell apoptosis via a TRAIL-dependent pathway during the early phase of Cryptosporidium parvum infection

BACKGROUND

MicroRNAs (miRNAs) are involved in the regulation of both the innate and adaptive immune response to Cryptosporidium parvum infection. We previously reported that C. parvum upregulated miR‑942‑5p expression in HCT‑8 cells via TLR2/TLR4‑NF‑κB signaling. In the present study, the role of miRNA-942-5p in the regulation of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated HCT-8 cell apoptosis induced by C. parvum was investigated.

METHODS

Quantitative real-time polymerase chain reaction, western blotting, flow cytometry, and immunofluorescence were used for analysis.

RESULTS

Forced expression of miRNA-942-5p resulted in decreased apoptosis and an increased C. parvum burden in HCT-8 cells. The opposite results were observed using the suppressed expression of miRNA-942-5p. The miRNA-942-5p led to the translational suppression of IFI27 gene through targeting the 3'-untranslated region of the IFI27 gene. Moreover, overexpression of the IFI27 gene produced a high apoptotic ratio and low C. parvum burden. In contrast, a low apoptotic ratio and a high C. parvum burden were observed following downregulation of the IFI27 gene. Both miR-942-5p and the IFI27 gene influenced TRAIL and caspase-8 expression induced by C. parvum in HCT-8 cells. Moreover, TRAIL promoted HCT-8 cell apoptosis in a concentration-dependent manner.

CONCLUSIONS

These data suggested that C. parvum induced the downregulation of IFI27 via relief of miR-942-5p-mediated translational suppression. IFI27 downregulation was affected the burden of C. parvum by regulating HCT-8 cell apoptosis through TRAIL-dependent pathways. Future studies should determine the mechanisms by which C. parvum infection increases miR-942-5p expression and the role of miR-942-5p in hosts' anti-C. parvum immunity in vivo.

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

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

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.

Chicken ISG12(2) attenuates Newcastle disease virus and enhances the efficiency of Newcastle disease vaccine via activating immune pathways

Low virulence and strong immunogenicity are quite important for Newcastle disease virus (NDV) producing Newcastle disease (ND) living-attenuated vaccine. However, immunogenicity of NDV positively correlates to its virulence. Usually, the velogenic NDV induces stronger immune responses of poultry than the lentogenic strain, but virulent NDV poses a risk for chicken. In this study, we identified the chicken interferon (IFN)-stimulated gene 12-2 (ISG12(2)) not only attenuated NDV, but also increased immunogenicity of ND vaccine strain. Firstly, we found that NDV infection or IFNs stimulation induced expression of chicken ISG12(2) that reinforced expression of IFNs. Overexpression or knockdown proved that chicken ISG12(2) inhibited NDV replication. Then, recombinant NDV LaSota strains (rLaSota/Fmut/ISG12(2) and rLaSota/ISG12(2)), expressing ISG12(2), were rescued. Pathogenicity tests showed that ISG12(2) expression attenuated NDV. RNA-seq or RT-qPCR demonstrated that, comparing to rLaSota/Fmut and rLaSota, rLaSota/Fmut/ISG12(2) and rLaSota/ISG12(2) induced hosts to produce cytokines enriching in innate and adaptive immune pathways in vitro and in vivo. Finally, we showed that rLaSota/ISG12(2) vaccination improved immune condition of chicken to quickly response NDV infection and then enhance protection. These results suggest that chicken ISG12(2) is a potential novel molecular adjuvant to regulate immune responses, which decrease virulence and increase immunogenicity of NDV. The chicken ISG12(2) may contribute to development of high efficient poultry vaccine. This article is protected by copyright. All rights reserved.

Antiviral Activity of Interferon Alpha-Inducible Protein 27 Against Hepatitis B Virus Gene Expression and Replication

Despite the availability of effective vaccines, hepatitis B virus (HBV) is still a major health issue, and approximately 350 million people have been chronically infected with HBV throughout the world. Interferons (IFNs) are the key molecules in the innate immune response that restrict several kinds of viral infections via the induction of hundreds of IFN-stimulated genes (ISGs). The objective of this study was to confirm if interferon alpha-inducible protein 27 (IFI27) as an ISG could inhibit HBV gene expression and DNA replication both in cell culture and in a mouse model. In human hepatoma cells, IFI27 was highly induced by the stimulation of IFN-alpha (IFN-α), and it potentiated the anti-HBV activity. The overexpression of IFI27 inhibited, while its silencing enhanced the HBV replication in HepG2 cell. However, the knocking out of IFI27 in HepG2 cells robustly increases the formation of viral DNA, RNA, and proteins. Detailed mechanistic analysis of the HBV genome showed that a sequence [nucleotide (nt) 1715-1815] of the EnhII/Cp promoter was solely responsible for viral inhibition. Similarly, the hydrodynamic injection of IFI27 expression constructs along with the HBV genome into mice resulted in a significant reduction in viral gene expression and DNA replication. In summary, our studies suggested that IFI27 contributed a vital role in HBV gene expression and replication and IFI27 may be a potential antiviral agent for the treatment of HBV.

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.

Molecular cloning and transcriptional regulation of Indian peafowl (Pavo cristatus) IFN-α gene

Interferon-α (IFN-α) resists viral infections by triggering the transcription of a diverse range of antiviral IFN-stimulated genes (ISGs). However, information about the Indian peafowl (Pavo cristatus) IFN-α (PcIFN-α) has not been reported. In this study, a PcIFN-α gene was amplified, which encoded a protein of 193 amino acids with a 26-amino acid signal peptide sharing 72.16-95.70% identity with other avians in Aves. After expression in prokaryote, PcIFN-α was analyzed for its physicochemical property and antiviral activity. Intriguingly, compared with chicken IFN-α, an effective viral infection therapeutic agent, PcIFN-α showed superior anti-VSV, NDV, and AIV activities, which were then abrogated by rabbit anti-PcIFN-α antibodies in vitro. Moreover, PcIFN-α was shown to be highly sensitive to trypsin; however, it remained stable despite changes in pH and temperature. Additionally, PcIFN-α induced the transcriptional or translational levels of Mx1 and ISG12 genes time-dependently. Overall, the present study revealed that PcIFN-α is a potential novel effective therapeutic agent in antiviral defense responses in peafowl, improving understanding of its involvement in bird antiviral defense.

High level expression of ISG12(1) promotes cell apoptosis via mitochondrial-dependent pathway and so as to hinder Newcastle disease virus replication

Newcastle disease (ND), caused by virulent Newcastle disease virus (NDV), poses a considerable risk for the poultry industry. A comprehensive understanding of the interaction between NDV and its host is therefore critical for control of this disease. Previously, we found that chicken ISG12(1) was among the significantly upregulated interferon-stimulated genes (ISGs) in embryos and the bursa of Fabricius of chickens infected by NDV, based on transcriptome sequencing. However, its antiviral effects and function were poorly understood. In this study, we aimed to determine the effects of chicken ISG12(1) on NDV replication. First, we confirmed that NDV infection stimulated high level expression of chicken ISG12(1) in vivo and in vitro based on RT-qPCR. Next, through overexpression and knockdown experiments, the antiviral activity of ISG12(1) was investigated. As expected, this protein was found to hinder NDV replication. In addition, we showed that ISG12(1) localized to the mitochondria; promoted the redistribution of Bax, a proapoptotic protein causing irreversible loss of mitochondrial function, from the cytoplasm to the mitochondria; and therefore induced cell apoptosis. In conclusion, elucidation of the role of chicken ISG12(1) in combatting NDV infection contributes to our understanding of the responses of poultry to viruses and may facilitate the generation of more efficient vaccines to control ND.

Long Non-coding RNAs: Regulators of Viral Infection and the Interferon Antiviral Response

Interferons (IFNs) are a family of cytokines providing a robust first line of host innate defense against pathogenic infection, and have now been part of the standard treatment for viral infection. However, IFN based therapy can best be described as modestly effective. Long non-coding RNAs (lncRNAs) are a novel class of non-protein-coding RNAs that are capable of regulating gene expression at different levels, including chromatin, transcription, post-transcription, and translation. Recently, lncRNAs are found to be deregulated upon viral infection or IFN treatment, and some of them can modulate viral infection in an IFN-dependent or -independent manner. Due to the crucial roles of lncRNAs in viral infection and the IFN antiviral response, the modulation of specific lncRNAs may be involved to increase the IFN antiviral response and improve the clinical result of IFN-based therapy. In this review, we summarize lncRNAs that are deregulated by viral infection, with special focus on the functions and underlying mechanisms of some essential lncRNAs, and discuss their roles in viral infection and the antiviral response of IFN.

TRIM21 Promotes Innate Immune Response to RNA Viral Infection through Lys27-Linked Polyubiquitination of MAVS

Human innate immunity responds to viral infection by activating the production of interferons (IFNs) and proinflammatory cytokines. The mitochondrial adaptor molecule MAVS plays a critical role in innate immune response to viral infection. In this study, we show that TRIM21 (tripartite motif-containing protein 21) interacts with MAVS to positively regulate innate immunity. Under viral infection, TRIM21 is upregulated through the IFN/JAK/STAT signaling pathway. Knockdown of TRIM21 dramatically impairs innate immune response to viral infection. Moreover, TRIM21 interacts with MAVS and catalyzes its K27-linked polyubiquitination, thereby promoting the recruitment of TBK1 to MAVS. Specifically, the PRY-SPRY domain of TRIM21 is the key domain for its interaction with MAVS, while the RING domain of TRIM21 facilitates the polyubiquitination chains of MAVS. In addition, the MAVS-mediated innate immune response is enhanced by both the PRY-SPRY and RING domains of TRIM21. Mutation analyses of all the lysine residues of MAVS further revealed that Lys325 of MAVS is catalyzed by TRIM21 for the K27-linked polyubiquitination. Overall, this study reveals a novel mechanism by which TRIM21 promotes the K27-linked polyubiquitination of MAVS to positively regulate innate immune response, thereby inhibiting viral infection.IMPORTANCE Activation of innate immunity is essential for host cells to restrict the spread of invading viruses and other pathogens. MAVS plays a critical role in innate immune response to RNA viral infection. In this study, we demonstrated that TRIM21 targets MAVS to positively regulate innate immunity. Notably, TRIM21 targets and catalyzes K27-linked polyubiquitination of MAVS and then promotes the recruitment of TBK1 to MAVS, leading to upregulation of innate immunity. Our study outlines a novel mechanism by which the IFN signaling pathway blocks RNA virus to escape immune elimination.

Transcriptome sequencing of neurologic diseases associated genes in HHV-6A infected human astrocyte

Human Herpesvirus 6 (HHV-6) has been involved in the development of several central nervous system (CNS) diseases, such as Alzheimer's disease, multiple sclerosis and glioma. In order to identify the pathogenic mechanism of HHV-6A infection, we carried out mRNA-seq study of human astrocyte HA1800 cell with HHV-6A GS infection. Using mRNA-seq analysis of HA1800-control cells with HA1800-HHV-6A GS cells, we identified 249 differentially expressed genes. After investigating these candidate genes, we found seven genes associated with two or more CNS diseases: CTSS, PTX3, CHI3L1, Mx1, CXCL16, BIRC3, and BST2. This is the first transcriptome sequencing study which showed the significant association of these genes between HHV-6A infection and neurologic diseases. We believe that our findings can provide a new perspective to understand the pathogenic mechanism of HHV-6A infection and neurologic diseases.

Porcine Interferon Stimulated Gene 12a Restricts Porcine Reproductive and Respiratory Syndrome Virus Replication in MARC-145 Cells

Porcine reproductive and respiratory syndrome virus (PRRSV) causes severe losses in the global pig industry. In the present study, we investigated the molecular characterization of porcine interferon stimulated gene 12a (ISG12A) and confirmed its anti-PRRSV ability for the first time. We found that porcine ISG12A was localized in mitochondria and significantly decreased the number of cells in G2/S phase. Porcine ISG12A mRNA was up-regulated in cells/tissues of Tongcheng (TC) pigs and Large White (LW) pigs after PRRSV challenge. More importantly, the ectopic overexpression of ISG12A could significantly suppress PRRSV replication at 24, 36 and 48 h post challenge (hpc), which was confirmed by detecting PRRSV ORF7 mRNA with quantitative reverse transcription polymerase chain reaction (qRT-PCR) and PRRSV N protein with indirect immunofluorescence assay (IFA) in MARC-145 cells. Meanwhile, knockdown of endogenic ISG12A could obviously facilitate PRRSV replication in MARC-145 cells at 36 hpc. The results will lead to a better understanding of the interaction between host immune system and PRRSV, which may help us develop novel therapeutic tools to control PRRSV.

Mesenchymal stem cells enhance the oncolytic effect of Newcastle disease virus in glioma cells and glioma stem cells via the secretion of TRAIL

Background

Newcastle disease virus (NDV) is an avian paramyxovirus, which selectively exerts oncolytic effects in cancer cells. Mesenchymal stem cells (MSCs) have been reported to affect tumor growth and deliver anti-tumor agents to experimental glioblastoma (GBM). Here, we explored the effects of NDV-infected MSCs derived from different sources, on glioma cells and glioma stem cells (GSCs) and the mechanisms involved in their effects.

Methods

The glioma cell lines (A172 and U87) and primary GSCs that were generated from GBM tumors were used in this study. MSCs derived from bone marrow, adipose tissue or umbilical cord were infected with NDV (MTH-68/H). The ability of these cells to deliver the virus to glioma cell lines and GSCs and the effects of NDV-infected MSCs on cell death and on the stemness and self-renewal of GSCs were examined. The mechanisms involved in the cytotoxic effects of the NDV-infected MSCs and their influence on the radiation sensitivity of GSCs were examined as well.

Results

NDV induced a dose-dependent cell death in glioma cells and a low level of apoptosis and inhibition of self-renewal in GSCs. MSCs derived from bone marrow, adipose and umbilical cord that were infected with NDV delivered the virus to co-cultured glioma cells and GSCs. Conditioned medium of NDV-infected MSCs induced higher level of apoptosis in the tumor cells compared with the apoptosis induced by their direct infection with similar virus titers. These results suggest that factor(s) secreted by the infected MSCs sensitized the glioma cells to the cytotoxic effects of NDV. We identified TRAIL as a mediator of the cytotoxic effects of the infected MSCs and demonstrated that TRAIL synergized with NDV in the induction of cell death in glioma cells and GSCs. Moreover, conditioned medium of infected MSCs enhanced the sensitivity of GSCs to γ-radiation.

Conclusions

NDV-infected umbilical cord-derived MSCs may provide a novel effective therapeutic approach for targeting GSCs and GBM and for sensitizing these tumors to γ-radiation.

ALV-J strain SCAU-HN06 induces innate immune responses in chicken primary monocyte-derived macrophages

Avian leucosis virus subgroup J (ALV-J) can cause lifelong infection and can escape from the host immune defenses in chickens. Since macrophages act as the important defense line against invading pathogens in host innate immunity, we investigated the function and innate immune responses of chicken primary monocyte-derived macrophages (MDM) after ALV-J infection in this study. Our results indicated that ALV-J was stably maintained in MDM cells but that the viral growth rate was significantly lower than that in DF-1 cells. We also found that ALV-J infection significantly increased nitric oxide (NO) production, but had no effect on MDM phagocytic capacity. Interestingly, infection with ALV-J rapidly promoted the expression levels of Myxovirus resistance 1 (Mx) (3 h, 6 h), ISG12 (6 h), and interleukin-1β (IL-1β) (3 h, 12 h) at an early infection stage, whereas it sharply decreased the expression of Mx (24 h, 36 h), ISG12 (36 h), and made little change on IL-1β (24 h, 36 h) production at a late infection stage in MDM cells. Moreover, the protein levels of interferon-β (IFN-β) and interleukin-6 (IL-6) had sharply increased in infected MDM cells from 3 to 36 h post infection (hpi) of ALV-J. And, the protein level of interleukin-10 (IL-10) was dramatically decreased at 36 hpi in MDM cells infected with ALV-J. These results demonstrate that ALV-J can induce host innate immune responses and we hypothesize that macrophages play an important role in host innate immune attack and ALV-J immune escape.

ISG12a Restricts Hepatitis C Virus Infection through the Ubiquitination-Dependent Degradation Pathway

Interferons (IFNs) restrict various kinds of viral infection via induction of hundreds of IFN-stimulated genes (ISGs), while the functions of the majority of ISGs are broadly unclear. Here, we show that a high-IFN-inducible gene, ISG12a (also known as IFI27), exhibits a nonapoptotic antiviral effect on hepatitis C virus (HCV) infection. Viral NS5A protein is targeted specifically by ISG12a, which mediates NS5A degradation via a ubiquitination-dependent proteasomal pathway. K374R mutation in NS5A domain III abrogates ISG12a-induced ubiquitination and degradation of NS5A. S-phase kinase-associated protein 2 (SKP2) is identified as an ubiquitin E3 ligase for NS5A. ISG12a functions as a crucial adaptor that promotes SKP2 to interact with and degrade viral protein. Moreover, the antiviral effect of ISG12a is dependent on the E3 ligase activity of SKP2. These findings uncover an intriguing mechanism by which ISG12a restricts viral infection and provide clues for understanding the actions of innate immunity.

IMPORTANCE

Upon virus invasion, IFNs induce numerous ISGs to control viral spread, while the functions of the majority of ISGs are broadly unclear. The present study shows a novel antiviral mechanism of ISGs and elucidated that ISG12a recruits an E3 ligase, SKP2, for ubiquitination and degradation of viral protein and restricts viral infection. These findings provide important insights into exploring the working principles of innate immunity.

The Interferon-Stimulated Gene Ifi27l2a Restricts West Nile Virus Infection and Pathogenesis in a Cell-Type- and Region-Specific Manner

The mammalian host responds to viral infections by inducing expression of hundreds of interferon-stimulated genes (ISGs). While the functional significance of many ISGs has yet to be determined, their cell type and temporal nature of expression suggest unique activities against specific pathogens. Using a combination of ectopic expression and gene silencing approaches in cell culture, we previously identified Ifi27l2a as a candidate antiviral ISG within neuronal subsets of the central nervous system (CNS) that restricts infection by West Nile virus (WNV), an encephalitic flavivirus of global concern. To investigate the physiological relevance of Ifi27l2a in the context of viral infection, we generated Ifi27l2a(-/-) mice. Although adult mice lacking Ifi27l2a were more vulnerable to lethal WNV infection, the viral burden was greater only within the CNS, particularly in the brain stem, cerebellum, and spinal cord. Within neurons of the cerebellum and brain stem, in the context of WNV infection, a deficiency of Ifi27l2a was associated with less cell death, which likely contributed to sustained viral replication and higher titers in these regions. Infection studies in a primary cell culture revealed that Ifi27l2a(-/-) cerebellar granule cell neurons and macrophages but not cerebral cortical neurons, embryonic fibroblasts, or dendritic cells sustained higher levels of WNV infection than wild-type cells and that this difference was greater under conditions of beta interferon (IFN-β) pretreatment. Collectively, these findings suggest that Ifi27l2a has an antiviral phenotype in subsets of cells and that at least some ISGs have specific inhibitory functions in restricted tissues.

IMPORTANCE

The interferon-stimulated Ifi27l2a gene is expressed differentially within the central nervous system upon interferon stimulation or viral infection. Prior studies in cell culture suggested an antiviral role for Ifi27l2a during infection by West Nile virus (WNV). To characterize its antiviral activity in vivo, we generated mice with a targeted gene deletion of Ifi27l2a. Based on extensive virological analyses, we determined that Ifi27l2a protects mice from WNV-induced mortality by contributing to the control of infection of the hindbrain and spinal cord, possibly by regulating cell death of neurons. This antiviral activity was validated in granule cell neurons derived from the cerebellum and in macrophages but was not observed in other cell types. Collectively, these data suggest that Ifi27l2a contributes to innate immune restriction of WNV in a cell-type- and tissue-specific manner.

Expression of Raf kinase inhibitor protein is downregulated in response to Newcastle disease virus infection to promote viral replication

Newcastle disease virus (NDV) causes a severe and economically significant disease affecting almost the entire poultry industry worldwide. However, factors that affect NDV replication in host cells are poorly understood. Raf kinase inhibitory protein (RKIP) is a physiological inhibitor of c-RAF kinase and NF-κB signalling, known for their functions in the control of immune response as well as tumour invasion and metastasis. In the present study, we investigated the consequences of overexpression of host RKIP during viral infection. We demonstrate that NDV infection represses RKIP expression thereby promoting virus replication. Experimental upregulation of RKIP in turn acts as a potential antiviral defence mechanism in host cells that restricts NDV replication by repressing the activation of Raf/MEK/ERK and IκBα/NF-κB signalling pathways. Our results not only extend the concept of linking NDV-host interactions, but also reveal RKIP as a new class of protein-kinase-inhibitor protein that affects NDV replication with therapeutic potential.