scholarly journals N6-Methyladenosine modification of hepatitis B and C viral RNAs attenuates host innate immunity via RIG-I signaling

2020 ◽  
Vol 295 (37) ◽  
pp. 13123-13133 ◽  
Author(s):  
Geon-Woo Kim ◽  
Hasan Imam ◽  
Mohsin Khan ◽  
Aleem Siddiqui
Keyword(s):  
Innate Immunity ◽  
Hepatitis B ◽  
Viral Infections ◽  
Type I ◽  
Rna Recognition ◽  
Single Nucleotide ◽  
Viral Rnas ◽  
Dual Functional ◽  
Nucleotide Mutation ◽  
Host Innate Immunity

N6-Methyladenosine (m6A), the methylation of the adenosine base at the nitrogen 6 position, is the most common epitranscriptomic modification of mRNA that affects a wide variety of biological functions. We have previously reported that hepatitis B viral RNAs are m6A-modified, displaying a dual functional role in the viral life cycle. Here, we show that cellular m6A machinery regulates host innate immunity against hepatitis B and C viral infections by inducing m6A modification of viral transcripts. The depletion of the m6A writer enzymes (METTL3 and METTL14) leads to an increase in viral RNA recognition by retinoic acid–inducible gene I (RIG-I), thereby stimulating type I interferon production. This is reversed in cells in which m6A METTL3 and METTL14 are overexpressed. The m6A modification of viral RNAs renders RIG-I signaling less effective, whereas single nucleotide mutation of m6A consensus motif of viral RNAs enhances RIG-I sensing activity. Importantly, m6A reader proteins (YTHDF2 and YTHDF3) inhibit RIG-I–transduced signaling activated by viral RNAs by occupying m6A-modified RNAs and inhibiting RIG-I recognition. Collectively, our results provide new insights into the mechanism of immune evasion via m6A modification of viral RNAs.

scholarly journals Non-segmented negative-sense RNA viruses utilize N6-methyladenosine (m6A) as a common strategy to evade host innate immunity

2021 ◽  
Author(s):  
Mijia Lu ◽  
Miaoge Xue ◽  
Hai-Tao Wang ◽  
Elizabeth L. Kairis ◽  
Sadeem Ahmad ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Signaling Pathway ◽  
Type I Interferon ◽  
Rna Viruses ◽  
Viral Rna ◽  
Type I ◽  
Viral Rnas ◽  
Common Strategy ◽  
Host Innate Immunity ◽  
Negative Sense

N6-methyladenosine (m6A) is the most abundant internal RNA modification catalyzed by host RNA methyltransferases. As obligate intracellular parasites, many viruses acquire m6A methylation in their RNAs. However, the biological functions of viral m6A methylation are poorly understood. Here, we found that viral m6A methylation serves as a molecular marker for host innate immunity to discriminate self from nonself RNA and that this novel biological function of viral m6A methylation is universally conserved in several families in non-segmented negative-sense (NNS) RNA viruses. Using m6A methyltransferase (METTL3)-knockout cells, we produced m6A-deficient virion RNA from the representative members of the families Pneumoviridae, Paramyxoviridae, and Rhabdoviridae and found that these m6A-deficient viral RNAs triggered significantly higher levels of type I interferon compared to the m6A-sufficient viral RNAs, in a RIG-I dependent manner. Reconstitution of the RIG-I pathway revealed that m6A-deficient virion RNA induced higher expression of RIG-I, bound to RIG-I more efficiently, enhanced RIG-I ubiquitination, and facilitated RIG-I conformational rearrangement and oligomerization. Furthermore, the m6A binding protein YTHDF2 is essential for suppression of type I interferon signaling pathway included by virion RNA. Collectively, our results suggest that several families in NNS RNA viruses acquire m6A in viral RNA as a common strategy to evade host innate immunity. IMPORTANCE The non-segmented negative-sense (NNS) RNA viruses share many common replication and gene expression strategies. There is no vaccine or antiviral drugs for many of these viruses. We found that representative members in the families of Pneumoviridae, Paramyxoviridae, and Rhabdoviridae in NNS RNA viruses acquire m6A methylation in their genome and antigenome as a means to escape the recognition by host innate immunity via a RIG-I dependent signaling pathway. Viral RNA lacking m6A methylation induces a significantly higher type I interferon compared to m6A sufficient viral RNA. In addition to uncovering m6A methylation as a common mechanism for many NNS RNA viruses to evade host innate immunity, this study discovered a novel strategy to enhance type I interferon responses, which may have important applications in vaccine development, as a robust innate immunity will likely promote the subsequent adaptive immunity.

scholarly journals Single-nucleotide methylation specifically represses type I interferon in antiviral innate immunity

2021 ◽  
Vol 218 (3) ◽  
Author(s):  
Zheng-jun Gao ◽  
Wen-ping Li ◽  
Xin-tao Mao ◽  
Tao Huang ◽  
Hao-li Wang ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Innate Immunity ◽  
Viral Infections ◽  
Critical Role ◽  
Endogenous Retrovirus ◽  
Type I ◽  
Single Nucleotide ◽  
Antiviral Immune Response ◽  
Genome Bisulfite Sequencing ◽  
Antiviral Innate Immunity

Frequent outbreaks of viruses have caused a serious threat to public health. Previous evidence has revealed that DNA methylation is correlated with viral infections, but its role in innate immunity remains poorly investigated. Additionally, DNA methylation inhibitors promote IFN-I by upregulating endogenous retrovirus; however, studies of intrinsically demethylated tumors do not support this conclusion. This study found that Uhrf1 deficiency in myeloid cells significantly upregulated Ifnb expression, increasing resistance to viral infection. We performed whole-genome bisulfite sequencing and found that a single-nucleotide methylation site in the Ifnb promoter region disrupted IRF3 recruitment. We used site-specific mutant knock-in mice and a region-specific demethylation tool to confirm that this methylated site plays a critical role in regulating Ifnb expression and antiviral responses. These findings provide essential insight into DNA methylation in the regulation of the innate antiviral immune response.

scholarly journals Immunological Aspects Related to Viral Infections in Severe Asthma and the Role of Omalizumab

Biomedicines ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 348
Author(s):  
Francesco Menzella ◽  
Giulia Ghidoni ◽  
Carla Galeone ◽  
Silvia Capobelli ◽  
Chiara Scelfo ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Severe Asthma ◽  
Viral Infections ◽  
Respiratory Infections ◽  
Antiviral Effect ◽  
Point Of View ◽  
Type I ◽  
Effector Cells ◽  
Viral Spread ◽  
Increased Risk

Viral respiratory infections are recognized risk factors for the loss of control of allergic asthma and the induction of exacerbations, both in adults and children. Severe asthma is more susceptible to virus-induced asthma exacerbations, especially in the presence of high IgE levels. In the course of immune responses to viruses, an initial activation of innate immunity typically occurs and the production of type I and III interferons is essential in the control of viral spread. However, the Th2 inflammatory environment still appears to be protective against viral infections in general and in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections as well. As for now, literature data, although extremely limited and preliminary, show that severe asthma patients treated with biologics don’t have an increased risk of SARS-CoV-2 infection or progression to severe forms compared to the non-asthmatic population. Omalizumab, an anti-IgE monoclonal antibody, exerts a profound cellular effect, which can stabilize the effector cells, and is becoming much more efficient from the point of view of innate immunity in contrasting respiratory viral infections. In addition to the antiviral effect, clinical efficacy and safety of this biological allow a great improvement in the management of asthma.

scholarly journals Hepatitis B virus X protein recruits methyltransferases to affect cotranscriptional N6-methyladenosine modification of viral/host RNAs

2021 ◽  
Vol 118 (3) ◽  
pp. e2019455118
Author(s):  
Geon-Woo Kim ◽  
Aleem Siddiqui
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Nuclear Export ◽  
Nuclear Export Signal ◽  
Ectopic Expression ◽  
Viral Rnas ◽  
Dual Functional ◽  
Chronic Hepatitis B Virus ◽  
B Virus

Chronic hepatitis B virus (HBV) infections are one of the leading causes of cirrhosis and hepatocellular carcinoma. N6-methyladenosine (m6A) modification of cellular and viral RNAs is the most prevalent internal modification that occurs cotranscriptionally. Previously, we reported the dual functional role of m6A modification of HBV transcripts in the viral life cycle. Here, we show that viral HBV X (HBx) protein is responsible for the m6A modifications of viral transcripts. HBV genomes defective in HBx failed to induce m6A modifications of HBV RNAs during infection/transfection, while ectopic expression of HBx restores m6A modifications of the viral RNAs but not the mutant HBx carrying the nuclear export signal. Using chromatin immunoprecipitation assays, we provide evidence that HBx and m6A methyltransferase complexes are localized on the HBV minichromosome to achieve cotranscriptional m6A modification of viral RNAs. HBx interacts with METTL3 and 14 to carry out methylation activity and also modestly stimulates their nuclear import. This role of HBx in mediating m6A modification also extends to host phosphatase and tensin homolog (PTEN) mRNA. This study provides insight into how a viral protein recruits RNA methylation machinery to m6A-modify RNAs.

scholarly journals Virus Caused Imbalance of Type I IFN Responses and Inflammation in COVID-19

2021 ◽  
Vol 12 ◽  
Author(s):  
Jintao Zhang ◽  
Chunyuan Zhao ◽  
Wei Zhao
Keyword(s):  
Innate Immunity ◽  
Innate Immune System ◽  
Innate Immune ◽  
Type I Interferons ◽  
Type I ◽  
Type I Ifn ◽  
Antiviral Responses ◽  
Public Health Challenges ◽  
Host Innate Immunity ◽  
Efficient Elimination

The global expansion of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged as one of the greatest public health challenges and imposes a great threat to human health. Innate immunity plays vital roles in eliminating viruses through initiating type I interferons (IFNs)-dependent antiviral responses and inducing inflammation. Therefore, optimal activation of innate immunity and balanced type I IFN responses and inflammation are beneficial for efficient elimination of invading viruses. However, SARS-CoV-2 manipulates the host’s innate immune system by multiple mechanisms, leading to aberrant type I IFN responses and excessive inflammation. In this review, we will emphasize the recent advances in the understanding of the crosstalk between host innate immunity and SARS-CoV-2 to explain the imbalance between inflammation and type I IFN responses caused by viral infection, and explore potential therapeutic targets for COVID-19.

scholarly journals When human guanylate-binding proteins meet viral infections

2021 ◽  
Vol 28 (1) ◽  
Author(s):  
Rongzhao Zhang ◽  
Zhixin Li ◽  
Yan-Dong Tang ◽  
Chenhe Su ◽  
Chunfu Zheng
Keyword(s):  
Innate Immunity ◽  
Viral Infection ◽  
Binding Proteins ◽  
Molecular Mechanisms ◽  
Viral Infections ◽  
Innate Immune ◽  
Type I Interferons ◽  
Type I ◽  
Downstream Signaling ◽  
Antiviral Innate Immunity

AbstractInnate immunity is the first line of host defense against viral infection. After invading into the cells, pathogen-associated-molecular-patterns derived from viruses are recognized by pattern recognition receptors to activate the downstream signaling pathways to induce the production of type I interferons (IFN-I) and inflammatory cytokines, which play critical functions in the host antiviral innate immune responses. Guanylate-binding proteins (GBPs) are IFN-inducible antiviral effectors belonging to the guanosine triphosphatases family. In addition to exerting direct antiviral functions against certain viruses, a few GBPs also exhibit regulatory roles on the host antiviral innate immunity. However, our understanding of the underlying molecular mechanisms of GBPs' roles in viral infection and host antiviral innate immune signaling is still very limited. Therefore, here we present an updated overview of the functions of GBPs during viral infection and in antiviral innate immunity, and highlight discrepancies in reported findings and current challenges for future studies, which will advance our understanding of the functions of GBPs and provide a scientific and theoretical basis for the regulation of antiviral innate immunity.

scholarly journals Immunological Aspects Related to Viral Infections in Severe Asthma and the Role of Omalizumab

2021 ◽  
Author(s):  
Francesco Menzella ◽  
Giulia Ghidoni ◽  
Carla Galeone ◽  
Silvia Capobelli ◽  
Chiara Scelfo ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Severe Asthma ◽  
Viral Infections ◽  
Respiratory Infections ◽  
Antiviral Effect ◽  
Point Of View ◽  
Type I ◽  
Effector Cells ◽  
Viral Spread ◽  
Increased Risk

Viral respiratory infections are recognized risk factors for the loss of control of allergic asthma and the induction of exacerbations, both in adults and children. Severe asthma is more susceptible to virus-induced asthma exacerbations, especially in the presence of high IgE levels. In the course of immune responses to viruses, an initial activation of innate immunity typically occurs and the production of type I and III interferons is essential in the control of viral spread. However, the Th2 inflammatory environment still appears to be protective against viral infections in general and in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections as well. As for now, literature data, although very limited and preliminary, show that severe asthma patients treated with biologics don’t have an increased risk of SARS-CoV-2 infection or progression to severe forms compared to the non-asthmatic population. Omalizumab, an anti-IgE monoclonal antibody, exerts a profound cellular effect, which is able to stabilize the effector cells becoming much more efficient from the point of view of innate immunity in contrasting respiratory viral infections. In addition to the antiviral effect, clinical efficacy and safety of this biological allows a great improvement in the management of asthma.

The transmembrane serine protease hepsin suppresses type I interferon induction by cleaving STING

2021 ◽  
Vol 14 (687) ◽  
pp. eabb4752
Author(s):  
Fu Hsin ◽  
Yu-Chen Hsu ◽  
Yu-Fei Tsai ◽  
Shu-Wha Lin ◽  
Helene Minyi Liu
Keyword(s):  
Innate Immunity ◽  
Viral Infections ◽  
Ectopic Expression ◽  
Type I ◽  
Adapter Proteins ◽  
Type I Ifn ◽  
Chronic Viral Infections ◽  
Viral Proteases ◽  
Transmembrane Serine Protease ◽  
Antiviral Innate Immunity

Many viral proteases mediate the evasion of antiviral innate immunity by cleaving adapter proteins in the interferon (IFN) induction pathway. Host proteases are also involved in innate immunity and inflammation. Here, we report that the transmembrane protease hepsin (also known as TMPRSS1), which is predominantly present in hepatocytes, inhibited the induction of type I IFN during viral infections. Knocking out hepsin in mouse embryonic fibroblasts (MEFs) increased the viral infection–induced expression of Ifnb1, an Ifnb1 promoter reporter, and an IFN-sensitive response element promoter reporter. Ectopic expression of hepsin in cultured human hepatocytes and HEK293T cells suppressed the induction of IFNβ during viral infections by reducing the abundance of STING. These effects depended on the protease activity of hepsin. We identified a putative hepsin target site in STING and showed that mutating this site protected STING from hepsin-mediated cleavage. In addition to hepatocytes, several hepsin-producing prostate cancer cell lines showed reduced STING-mediated type I IFN induction and responses. These results reveal a role for hepsin in suppressing STING-mediated type I IFN induction, which may contribute to the vulnerability of hepatocytes to chronic viral infections.

scholarly journals Antiviral Efficacy and Host Innate Immunity Associated with SB 9200 Treatment in the Woodchuck Model of Chronic Hepatitis B

PLoS ONE ◽  
2016 ◽  
Vol 11 (8) ◽  
pp. e0161313 ◽  
Author(s):  
Kyle E. Korolowicz ◽  
Radhakrishnan P. Iyer ◽  
Stefanie Czerwinski ◽  
Manasa Suresh ◽  
Junming Yang ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Chronic Hepatitis ◽  
Hepatitis B ◽  
Chronic Hepatitis B ◽  
Antiviral Efficacy ◽  
Host Innate Immunity ◽  
Woodchuck Model

scholarly journals PARP1 Enhances Influenza A Virus Propagation by Facilitating Degradation of Host Type I Interferon Receptor

2020 ◽  
Vol 94 (7) ◽  
Author(s):  
Chuan Xia ◽  
Jennifer J. Wolf ◽  
Chuankai Sun ◽  
Mengqiong Xu ◽  
Caleb J. Studstill ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Influenza Virus ◽  
Molecular Mechanism ◽  
Influenza A Virus ◽  
Influenza A ◽  
Type I Interferon ◽  
Type I ◽  
Type I Ifn ◽  
Host Type ◽  
Host Innate Immunity

ABSTRACT Influenza A virus (IAV) utilizes multiple strategies to confront or evade host type I interferon (IFN)-mediated antiviral responses in order to enhance its own propagation within the host. One such strategy is to induce the degradation of type I IFN receptor 1 (IFNAR1) by utilizing viral hemagglutinin (HA). However, the molecular mechanism behind this process is poorly understood. Here, we report that a cellular protein, poly(ADP-ribose) polymerase 1 (PARP1), plays a critical role in mediating IAV HA-induced degradation of IFNAR1. We identified PARP1 as an interacting partner for IAV HA through mass spectrometry analysis. This interaction was confirmed by coimmunoprecipitation analyses. Furthermore, confocal fluorescence microscopy showed altered localization of endogenous PARP1 upon transient IAV HA expression or during IAV infection. Knockdown or inhibition of PARP1 rescued IFNAR1 levels upon IAV infection or HA expression, exemplifying the importance of PARP1 for IAV-induced reduction of IFNAR1. Notably, PARP1 was crucial for the robust replication of IAV, which was associated with regulation of the type I IFN receptor signaling pathway. These results indicate that PARP1 promotes IAV replication by controlling viral HA-induced degradation of host type I IFN receptor. Altogether, these findings provide novel insight into interactions between influenza virus and the host innate immune response and reveal a new function for PARP1 during influenza virus infection. IMPORTANCE Influenza A virus (IAV) infections cause seasonal and pandemic influenza outbreaks, which pose a devastating global health concern. Despite the availability of antivirals against influenza, new IAV strains continue to persist by overcoming the therapeutics. Therefore, much emphasis in the field is placed on identifying new therapeutic targets that can more effectively control influenza. IAV utilizes several tactics to evade host innate immunity, which include the evasion of antiviral type I interferon (IFN) responses. Degradation of type I IFN receptor (IFNAR) is one known method of subversion, but the molecular mechanism for IFNAR downregulation during IAV infection remains unclear. Here, we have found that a host protein, poly(ADP-ribose) polymerase 1 (PARP1), facilitates IFNAR degradation and accelerates IAV replication. The findings reveal a novel cellular target for the potential development of antivirals against influenza, as well as expand our base of knowledge regarding interactions between influenza and the host innate immunity.

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