The novel human coronavirus disease COVID-19 has become the fifth documented pandemic since the 1918 flu pandemic. COVID-19 was first reported in Wuhan, China, and subsequently spread worldwide. The ...coronavirus was officially named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by the International Committee on Taxonomy of Viruses based on phylogenetic analysis. SARS-CoV-2 is believed to be a spillover of an animal coronavirus and later adapted the ability of human-to-human transmission. Because the virus is highly contagious, it rapidly spreads and continuously evolves in the human population. In this review article, we discuss the basic properties, potential origin, and evolution of the novel human coronavirus. These factors may be critical for studies of pathogenicity, antiviral designs, and vaccine development against the virus.
Taiwan experienced two waves of imported infections with Coronavirus Disease 2019 (COVID-19). This study aimed at investigating the genomic variation of severe acute respiratory syndrome coronavirus ...2 (SARS-CoV-2) in Taiwan and compared their evolutionary trajectories with the global strains. We performed culture and full-genome sequencing of SARS-CoV-2 strains followed by phylogenetic analysis. A 382-nucleotides deletion in open reading frame 8 (ORF8) was found in a Taiwanese strain isolated from a patient on February 4, 2020 who had a travel history to Wuhan. Patients in the first wave also included several sporadic, local transmission cases. Genomes of 5 strains sequenced from clustered infections were classified into a new clade with ORF1ab-V378I mutation, in addition to 3 dominant clades ORF8-L84S, ORF3a-G251V and S-D614G. This highlighted clade also included some strains isolated from patients who had a travel history to Turkey and Iran. The second wave mostly resulted from patients who had a travel history to Europe and Americas. All Taiwanese viruses were classified into various clades. Genomic surveillance of SARS-CoV-2 in Taiwan revealed a new ORF8-deletion mutant and a virus clade that may be associated with infections in the Middle East, which contributed to a better understanding of the global SARS-CoV-2 transmission dynamics.
Enterovirus A71 (EV-A71) belongs to the genus Enterovirus of the Picornaviridae family and often causes outbreaks in Asia. EV-A71 infection usually causes hand, foot, and mouth disease and can even ...affect the central nervous system, causing neurological complications or death. The 5'-untranslated region (5'-UTR) of EV-A71 contains an internal ribosome entry site (IRES) that is responsible for the translation of viral proteins. IRES-transacting factors can interact with the EV-A71 5'-UTR to regulate IRES activity. Heterogeneous nuclear ribonucleoprotein (hnRNP) A3 is a member of the hnRNP A/B protein family of RNA-binding proteins and is involved in RNA transport and modification. We found that hnRNP A3 knockdown promoted the replication of EV-A71 in neural calls. Conversely, increasing the expression of hnRNP A3 within cells inhibits the growth of EV-A71. HnRNP A3 can bind to the EV-A71 5'-UTR, and knockdown of hnRNP A3 enhances the luciferase activity of the EV-A71 5'-UTR IRES. The localization of hnRNP A3 shifts from the nucleus to the cytoplasm of infected cells during viral infection. Additionally, EV-A71 infection can increase the protein expression of hnRNP A3, and the protein level is correlated with efficient viral growth. Based on these findings, we concluded that hnRNP A3 plays a negative regulatory role in EV-A71 replication within neural cells.
Induction of type-I interferons (IFNs), IFN-α/β, is crucial to innate immunity against RNA virus infection. Cytoplasmic retinoic acid-inducible gene I (RIG-I)-like receptors, including RIG-I and ...melanoma differentiation-associated gene 5 (MDA5), are critical pathogen sensors for activation of type-I IFN expression in response to RNA virus infection. MDA5 is required for type-I IFN expression in mouse models in response to infection by picornaviruses, such as encephalomyocarditis virus (EMCV) and coxsackievirus B3. Enterovirus 71 (EV71) belongs to picornaviridae and contains positive-stranded RNA genome that is linked with VPg protein at the 5' end. Although a recent study showed that EV71 3C protease could suppress RIG-I-mediated IFN-β response, the cytoplasmic RIG-I-like receptor that is directly involved in the recognition of EV71 RNA remains unclear. Using EV71-derived RNA as an agonist, we demonstrate that MDA5 is involved in EV71 RNA-mediated IRF3 activation and IFN-β transcription. Our data also show that overexpression of the MDA5 protein reverses the suppression of IRF3 activation caused by EV71 infection. These results indicate that MDA5 is an important factor for EV71 RNA-activated type-I IFN expression. Furthermore, we also show that EV71 infection enhances MDA5 degradation and that the degradation could be inhibited by a broad spectrum caspase inhibitor.
The viral ribonucleoprotein (vRNP) of influenza A virus is formed by virion RNA (vRNA), viral polymerase complex, and nucleoprotein (NP). The NP plays an important role in facilitating the ...replication and stabilization of viral RNA. To explore host factors that may be involved in the regulation of viral replication through interactions with NP, we conducted an immunoprecipitation experiment followed by mass spectrometry to identify NP-associated cellular proteins. Here, we demonstrate that NP can interact and colocalize with heterogeneous nuclear ribonucleoprotein (hnRNP) A2/B1 in mammalian cells and that the interaction may occur via direct binding to the glycine-rich domain (GRD) of hnRNP A2/B1. In addition, two residues in the tail loop of NP, F412 and R422, are required for the interaction of hnRNP A2/B1. Because the knockdown of hnRNP A2/B1 expression reduces viral RNP activity, hnRNP A2/B1 may act as a positive regulator in viral RNA synthesis of influenza A virus. More importantly, the findings in this research demonstrate that host proteins can regulate the replication of influenza A virus by interacting with NP.
Neural stem cells (NSCs) residing in the central nervous system play an important role in neurogenesis. Several viruses can infect these neural progenitors and cause severe neurological diseases. The ...innate immune responses against the neurotropic viruses in these tissue-specific stem cells remain unclear.
Human NSCs were transfected with viral RNA mimics or infected with neurotropic virus for detecting the expression of antiviral interferons (IFNs) and downstream IFN-stimulated antiviral genes.
NSCs are able to produce interferon-β (IFN-β) (type I) and λ1 (type III) after transfection with poly(I:C) and that downstream IFN-stimulated antiviral genes, such as ISG56 and MxA, and the viral RNA sensors RIG-I, MDA5, and TLR3, can be expressed in NSCs under poly(I:C) or IFN-β stimulation. In addition, our results show that the pattern recognition receptors RIG-I and MDA5, as well as the endosomal pathogen recognition receptor TLR3, but not TLR7 and TLR8, are involved in the activation of IFN-β transcription in NSCs. Furthermore, NSCs infected with the neurotropic viruses, Zika and Japanese encephalitis viruses, are able to induce RIG-I-mediated IFN-β expression.
Human NSCs have the ability to activate IFN signals against neurotropic viral pathogens.
ISG15 is an IFN-α/β-induced, ubiquitin-like protein that is conjugated to a wide array of cellular proteins through the sequential action of three conjugation enzymes that are also induced by ...IFN-α/β. Recent studies showed that ISG15 and/or its conjugates play an important role in protecting cells from infection by several viruses, including influenza A virus. However, the mechanism by which ISG15 modification exerts antiviral activity has not been established. Here we extend the repertoire of ISG15 targets to a viral protein by demonstrating that the NS1 protein of influenza A virus (NS1A protein), an essential, multifunctional protein, is ISG15 modified in virus-infected cells. We demonstrate that the major ISG15 acceptor site in the NS1A protein in infected cells is a critical lysine residue (K41) in the N-terminal RNA-binding domain (RBD). ISG15 modification of K41 disrupts the association of the NS1A RBD domain with importin-α, the protein that mediates nuclear import of the NS1A protein, whereas the RBD retains its double-stranded RNA-binding activity. Most significantly, we show that ISG15 modification of K41 inhibits influenza A virus replication and thus contributes to the antiviral action of IFN-β. We also show that the NS1A protein directly and specifically binds to Herc5, the major E3 ligase for ISG15 conjugation in human cells. These results establish a "loss of function" mechanism for the antiviral activity of the IFN-induced ISG15 conjugation system, namely, that it inhibits viral replication by conjugating ISG15 to a specific viral protein, thereby inhibiting its function.
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•Development of a paper-based enzyme-free sandwich immunoassay.•Optimization of the conditions of paper-based immunoassay.•Detecting and subtyping of influenza viruses with the ...detection limits of 2.7×103pfu/assay for H1 detection and 2.7×104pfu/assay for H3 detection.•Demonstration of influenza screening with less sample and reagent volume (5μL) in shorter period of time (around 1h).•Evaluation of the paper-based immunoassay using infected cell lysate and clinical samples.
Development of rapid screening in the ambulatory environment is the most pressing needs for the control of spread of infectious disease. Despite there are many methods to detect the immunoassay results, quantitative measurement in rapid disease screening is still a great challenge for point-of-care applications. In this work, based on the internal structural protein, i.e., nucleoprotein (NP), and outer surface glycoproteins, i.e., H1 and H3, of the influenza viruses, specific and sensitive immunoassay on paper-based platform was evaluated and confirmed. Detection and subtyping of influenza A H1N1 and H3N2 viruses found in people were demonstrated by colorimetric paper-based sandwich immunoassay. Concentration-dependent response to influenza viruses was shown and the detection limits could achieve 2.7×103pfu/assay for H1 detection and 2.7×104pfu/assay for H3 detection, which are within the clinical relevant level. Moreover, detection of influenza virus from infected cell lysate and clinical samples was demonstrated to further confirm the reliability of the paper-based immunoassay. The use of paper for the development of diagnostic devices has the advantages of lightweight, ease-of-use, and low cost and paper-based immunoassay is appropriate to apply for rapid screening in point-of-care applications.
Elimination of serious side effects is a desired feature of cancer therapy. Alternating electric field treatment is one approach to the non-invasive treatment of cancer. The efficacy and safety of ...this novel therapy are confirmed for the treatment of glioblastoma multiforme. In the current study, we co-cultured cancer cells and normal cells to investigate the selectivity and chemosensitivity enhancement of an electric field treatment. Cancer cells (cell line: HeLa and Huh7) and fibroblasts (cell line: HEL299) were cultured in an in-house–developed cell culture device embedded with stimulating electrodes. A low-intensity alternating electric field was applied to the culture. The field significantly induced proliferation arrest of the cancer cells, while had limited influence on the fibroblasts. Moreover, in combination with the anti-cancer drug, damage to the cancer cells was enhanced by the electric field. Thus, a lower dosage of the drug could be applied to achieve the same treatment effectiveness. This study provides evidence that low-intensity electric field treatment selectively induced proliferation arrest and enhanced the chemosensitivity of the cancer cells. This electro-chemotherapy could be developed and applied as a regional cancer therapy with minimal side effects.
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