Cloning,expression, and antiviral activity of interferon β from the Chinese microbat,Myotis davidii

Bats are natural reservoir hosts for many viruses that produce no clinical symptoms in bats.Therefore, bats may have evolved effective mechanisms to control viral replication. However, little information is available on bat immune responses to viral infection. Type I interferon(IFN) plays a key role in controlling viral infections. In this study, we report the cloning, expression, and biological activity of interferon β(IFNβ) from the Chinese microbat species, Myotis davidii. We demonstrated the upregulation of IFNB and IFN-stimulated genes in a kidney cell line derived from M. davidii after treatment with poly I:C or infection with Sendai virus. Furthermore, the recombinant IFNβ inhibited vesicular stomatitis virus and bat adenovirus replication in cell lines from two bat species, M. davidii and Rhinolophus sinicus. We provide the first in vitro evidence of IFNβ antiviral activity in microbats, which has important implications for virus interactions with these hosts.     

Generation of A Stable GFP-reporter Zika Virus System for High-throughput Screening of Zika Virus Inhibitors

Zika virus(ZIKV) is associated with severe birth defects and Guillain-Barre′ syndrome and no approved vaccines or specific therapies to combat ZIKV infection are currently available. To accelerate anti-ZIKV therapeutics research, we developed a stable ZIKV GFP-reporter virus system with considerably improved GFP visibility and stability. In this system a BHK-21 cell line expressing DC-SIGNR was established to facilitate the proliferation of GFP-reporter ZIKV. Using this reporter virus system, we established a high-throughput screening assay and screened a selected plant-sourced compounds library for their ability to block ZIKV infection. More than 31 out of 974 tested compounds effectively decreased ZIKV reporter infection. Four selected compounds, homoharringtonine(HHT), bruceine D(BD), dihydroartemisinin(DHA) and digitonin(DGT), were further validated to inhibit wild-type ZIKV infection in cells of BHK-21 and human cell line A549.The FDA-approved chronic myeloid leukemia treatment drug HHT and BD were identified as broad-spectrum flavivirus inhibitors. DHA, another FDA-approved antimalarial drug effectively inhibited ZIKV infection in BHK-21 cells. HHT, BD and DHA inhibited ZIKV infection at a post-entry stage. Digitonin was found to have inhibitory activity in the early stage of viral infection. Our research provides an efficient high-throughput screening assay for ZIKV inhibitors. The active compounds identified in this study represent potential therapies for the treatment of ZIKV infection.     

Japanese Encephalitis Virus NS1′ Protein Antagonizes Interferon Beta Production

Japanese encephalitis virus(JEV) is a mosquito-borne virus and the major cause of viral encephalitis in Asia. NS1', a52-amino acid C-terminal extension of NS1, is generated with a-1 programmed ribosomal frameshift and is only present in members of the Japanese encephalitis serogroup of flaviviruses. Previous studies demonstrated that NS1' plays a vital role in virulence, but the mechanism is unclear. In this study, an NS1' defected(rG66A) virus was generated. We found that rG66A virus was less virulent than its parent virus(pSA14) in wild-type mice. However, similar mortality caused by the two viruses was observed in an IFNAR knockout mouse model. Moreover, we found that rG66A virus induced a greater type Ⅰ interferon(IFN) response than that by pSA14, and JEV NS1' significantly inhibited the production of IFN-b and IFN-stimulated genes. Taken together, our results reveal that NS1' plays a vital role in blocking type I IFN production to help JEV evade antiviral immunity and benefit viral replication.     

A fresh look at an antiviral helicase

In order to survive, all organisms must guard against viral infections. Recognition of viruses is accomplished via multiple sensors. Many mammalian proteins can recognize viral products, such as double-stranded RNA （dsRNA）, yet few of them are known to induce interferon, the central antiviral messenger. Since interferon is indispensable for successful antiviral defense [1], the interferon-inducing sensors have been of particular interest. However, a clear understanding of such sensors has been elusive, and the first well-established sensor family, the toll-like receptors （TLRs）, was described relatively recently [2]. Antiviral TLRs are positioned in the endosomes, where they report the appearance of viral genetic material （DNA, single-and double-stranded RNA）. However, the question of potential virus sensors in the cytoplasm was left open. Given the particular effectiveness ofintracellular dsRNA at inducing interferon, it was suspected that dsRNA-binding sensor molecules would be found in the cytoplasm.[第一段]     

Trans Complementation of Replication-defective Omsk Hemorrhagic Fever Virus for Antiviral Study

Omsk hemorrhagic fever virus(OHFV) is a tick-borne flavivirus classified as a biosafety level-4(BSL4) pathogen. Studies of OHFV are restricted to be conducted within BSL4 laboratories. Currently, no commercial vaccines or antiviral drugs are available against OHFV infection. In this study, we recovered a replication-deficient OHFV with an NS1 deletion(OHFVDNS1) and reporter virus replacing NS1 with the Gaussia luciferase(Gluc)(OHFV-ΔNS1-Gluc). Both the defective OHFVDNS1 and OHFV-ΔNS1-Gluc virus could only replicate efficiently in the BHK21 cell line expressing NS1(BHK21_(NS1)) but not in na?ve BHK21 cells. The Gluc reporter gene of OHFV-ΔNS1-Gluc virus was maintained stably after serial passaging of BHK21_(NS1) cells and was used to surrogate the replication of OHFV. Using NITD008, OHFV-ΔNS1-Gluc virus was validated for antiviral screening, and high-throughput screening parameters were optimized in a 96-well plate format with a calculated Z0 value above 0.5. The OHFV-ΔNS1-Gluc reporter virus is a powerful tool for antiviral screening as well as viral replication and pathogenesis studies in BSL2 laboratories.     

Herpesviruses and the Type Ⅲ Interferon System

Type Ⅲ interferons (IFNs) represent the most recently discovered group of IFNs.Together with type Ⅰ IFNs (e.g.IFN-α/β),type Ⅲ IFNs (IFN-λ) are produced as part of the innate immune response to virus infection,and elicit an anti-viral state by inducing expression of interferon stimulated genes (ISGs).It was initially thought that type Ⅰ IFNs and type Ⅲ IFNs perform largely redundant functions.However,it has become evident that type Ⅲ IFNs particularly play a major role in antiviral protection of mucosal epithelial barriers,thereby serving an important role in the first-line defense against virus infection and invasion at contact areas with the outside world,versus the generally more broad,potent and systemic antiviral effects of type Ⅰ IFNs.Herpesviruseses are large DNA viruses,which enter their host via mucosal surfaces and establish lifelong,latent infections.Despite the importance of mucosal epithelial cells in the pathogenesis of herpesviruses,our current knowledge on the interaction of herpesviruses with type Ⅲ IFN is limited and largely restricted to studies on the alphaherpesvirus herpes simplex virus (HSV).This review summarizes the current understanding about the role of IFN-λ in the immune response against herpesvirus infections.     

Recent Advances in Animal Models of Zika Virus Infection

An infection by Zika virus(ZIKV), a mosquito-borne flavivirus, broke out in South American regions in 2015, and recently showed a tendency of spreading to North America and even worldwide. ZIKV was first detected in 1947 and only 14 human infection cases were reported until 2007. This virus was previously observed to cause only mild flu-like symptoms.However, recent ZIKV infections might be responsible for the increasing cases of neurological disorders such as GuillainBarre′ syndrome and congenital defects, including newborn microcephaly. Therefore, researchers have established several animal models to study ZIKV transmission and pathogenesis, and test therapeutic candidates. This review mainly summarizes the reported animal models of ZIKV infection, including mice and non-human primates.     

Viral suppression of innate immunity via spatial isolation of TBK1/IKKε from mitochondrial antivirai platform

For antiviral signaling mediated by retinoic acid-inducible gene I （RiG-I）-like receptors （RLRs）, the recruitment of cytosoUc RLRs and downstream molecules （such as TBK1 and IKKε） to mitochondriaL platform is a central event that facilitates the establishment of host antiviral state. Here, we present an example of viral targeting for immune evasion through spatial isolation of TBK1/IKKε from mitochond riai antiviral platform, which was employed by severe fever with thrombocytopenia syndrome virus （SFTSV）, a deadly bunyavirus emerging recently. We showed that SFTSV nonstructural protein NSs functions as the interferon （IFN） antagonist, mainly via suppressing TBK1/IKKε-IRF3 signaling. NSs mediates the formation of cytoplasmic inclusion bodies （IBs）, and the blockage of IB formation impairs IFN-inhibiting activity of NSs. We next demonstrate that I Bs are utilized to compartmentalize TBK1/I KKε. The compartmentalization results in spatial isolation of the kinases from mitochondria, and deprived TBK1/IKKε may participate in antiviral complex assembly, leadingto the blockage of lFN ind uction. This study proposes a new role of viral I Bs as virus-built＇jail＇ for imprisoning cellular factors and presents a novel and likely common mechanism of viral immune evasion through spatial isolation of critical signaling molecules from the mitochondrial antiviral platform.     

Duck egg drop syndrome virus: an emerging Tembusu-related flavivirus in China

Duck egg drop syndrome virus(DEDSV) is a newly emerging pathogenic flavivirus isolated from ducks in China.DEDSV infection mainly results in severe egg drop syndrome in domestic poultry,which leads to huge economic losses.Thus,the discovery of ways and means to combat DEDSV is urgent.Since 2010,a remarkable amount of progress concerning DEDSV research has been achieved.Here,we review current knowledge on the epidemiology,symptomatology,and pathology of DEDSV.A detailed dissection of the viral genome and polyprotein sequences,comparative analysis of viral antigenicity and the corresponding potential immunity against the virus are also summarized.Current findings indicate that DEDSV should be a distinct species from Tembusu virus.Moreover,the adaption of DEDSV in wildlife and its high homology to pathogenic flaviviruses(e.g.,West Nile virus,Japanese encephalitis virus,and dengue virus),illustrate its reemergence and potential to become a zoonotic pathogen that should not be overlooked.Detailed insight into the antigenicity and corresponding immunity against the virus is of clear significance for the development of vaccines and antiviral drugs specific for DEDSV.     

Epidemiological and etiological investigation of dengue fever in the Fujian province of China during 2004–2014

Dengue fever(DF) is a vector-borne disease and a tremendous socioeconomic burden on tropical and subtropical countries worldwide. To explore the characteristics of DF epidemic in the Fujian province, information of DF cases in Fujian during 2004–2014 was collected and analyzed. The complete E genes of 48 viral isolates were amplified and sequenced for phylogenetic analysis. A total of 733 cases was reported, of which 612(83.5%) occurred during the peak period from August to October. Additionally, 76%(190/250) of imported cases originated from Southeast Asia countries, by the epidemiological investigation. Phylogenetic analysis of the 48 viral isolates revealed that three genotypes(I, IV, V) of DENV1, and one genotype each of DENV2(cosmopolitan) and DENV3(I) circulated in Fujian during 2004–2014. Similar to the results of the epidemiological investigations, the source of most of the viral isolates, including imported and indigenous cases, may be Southeast Asia countries; however, importation from adjacent provinces was also observed in recent years. Overall, DF is considered an imported epidemic disease in Fujian. Increasing diversity of the viral source and geographic expansion of the area affected by DF in recent years highlights the necessity for strengthening surveillance of the DF epidemic and developing strategies for DF prevention and control in Fujian.     

Roles of HIV-1 auxiliary proteins in viral pathogenesis and host-pathogen interactions

Active host-pathogen interactions take place during infection of human immunodeficiency virus type 1 （HIV-1）. Outcomes of these interactions determine the efficiency of viral infection and subsequent disease progression. HIV-infected cells respond to viral invasion with various defensive strategies such as innate, cellular and humoral immune antiviral mechanisms. On the other hand, the virus has also developed various offensive tactics to suppress these host cellular responses. Among many of the viral offensive strategies, HIV-1 viral auxiliary proteins （Tat, Rev, Nef, Vif, Vpr and Vpu） play important roles in the host-pathogen interaction and thus have significant impacts on the outcome of HIV infection. One of the best examples is the interaction of Vif with a host cytidine deaminase APOBEC3G. Although specific roles of other auxiliary proteins are not as well described as Vif-APOBEC3G interaction, it is the goal of this brief review to summarize some of the preliminary findings with the hope to stimulate further discussion and investigation in this exhilarating area of research.     

Identification of one peptide which inhibited infectivity of avian infectious bronchitis virus in vitro

Purified avian infectious bronchitis virus (IBV) was used to screen a random phage display peptide library. After the fourth panning, 10 positive phages were sequenced and characterized. The phages specifically inhibited IBV infectivity in HeLa cells and blocked IBV haemagglutination. One linear peptide “GSH HRH VHS PFV” from the positive phages with the highest neutralization titer was synthesized and this peptide inhibited IBV infection in HeLa as well. The results may contribute to development of antiviral therapeutics for IBV and studying the determinants for viral and cell interac-tion.     

COVER

正Recent large outbreaks of Zika vrius (ZIKV)in Oceania's islands and the Americas have linked the ZIKV infection with occurrence of microcephaly in newborns.The virus can be passed from a pregnant woman to her fetus.Even worse,ZIKV has now spread to nearly 30 areas worldwide and become     

Responses of the Toll-like receptor and melanoma differentiation-associated protein 5 signaling pathways to avian infectious bronchitis virus infection in chicks

Avian infectious bronchitis virus(IBV) is a Gammacoronavirus in the family Coronaviridae and causes highly contagious respiratory disease in chickens. Innate immunity plays significant roles in host defense against IBV. Here, we explored the interaction between IBV and the host innate immune system. Severe histopathological lesions were observed in the tracheal mucosa at 3–5days post inoculation(dpi) and in the kidney at 8 dpi, with heavy viral loads at 1–11 and 1–28 dpi,respectively. The expression of m RNAs encoding Toll-like receptor(TLR) 3 and TLR7 were upregulated at 3–8 dpi, and that of TIR-domain-containing adapter-inducing interferon(IFN) β(TRIF) was upregulated at 21 dpi in the trachea and kidney. Myeloid differentiation primary response protein 88(My D88) was upregulated in the trachea during early infection. Tumor necrosis factor receptor-associated factor(TRAF) 3 and TRAF6 were upregulated expression in both tissues.Moreover, melanoma differentiation-associated protein 5(MDA5), laboratory of genetics and physiology 2(LGP2), stimulator of IFN genes(STING), and mitochondrial antiviral signaling protein(MAVS), as well as TANK binding kinase 1(TBK1), inhibitor of kappa B kinase(IKK) ?, IKKα, IKKβ,IFN regulatory factor(IRF) 7, nuclear factor of kappa B(NF-κB), IFN-α, IFN-β, various interleukins(ILs), and macrophage inflammatory protein-1β(MIP-1β) were significantly upregulated in the trachea and downregulated in the kidney. These results suggested that the TLR and MDA5 signaling pathways and innate immune cytokine were induced after IBV infection. Additionally,consistent responses to IBV infection were observed during early infection, with differential and complicated responses in the kidney.     

Characterization of viromes within mosquito species in China

正Mosquitoes are vectors of multiple disease-causing agents that cause worldwide outbreaks of serious infectious diseases in both humans and animals. These arboviral agents include Dengue virus (DENV), Zika virus (ZIKV), chikungunya virus, yellow fever virus, Japanese encephalitis virus (JEV),and Rift Valley fever virus. Thus, mosquitoes are key to the study of viral origin, spread, and the epidemic tendency of these infectious diseases (Hall and Macdonald, 2016). To the     

The Restrictome of Flaviviruses

Flaviviruses are a genus of mostly arthropod-borne RNA viruses that cause a range of pathologies in humans. Basic knowledge on flaviviruses is rapidly expanding, partly due to their status as frequent emerging or re-emerging pathogens.Flaviviruses include the dengue, Zika, West Nile, tick-borne encephalitis and yellow fever viruses(DENV, ZIKV, WNV,TBEV and YFV, respectively). As is the case with other families of viruses, the success of productive infection of human cells by flaviviruses depends in part on the antiviral activity of a heterogeneous group of cellular antiviral proteins called restriction factors. Restriction factors are the effector proteins of the cell-autonomous innate response against viruses, an immune pathway that also includes virus sensors as well as intracellular and extracellular signal mediators such as type I interferons(IFN-I). In this review, I summarize recent progress toward the identification and characterization of flavivirus restriction factors. In particular, I focus on IFI6, Schlafen 11, FMRP, OAS-RNase L, RyDEN, members of the TRIM family of proteins(TRIM5α, TRIM19, TRIM56, TRIM69 and TRIM79α) and a new mechanism of action proposed for viperin. Recent and future studies on this topic will lead to a more complete picture of the flavivirus restrictome, defined as the ensemble of cellular factors with demonstrated anti-flaviviral activity.     

In Vitro Anti-hepatitis B Virus Activity of 2',3'-Dideoxyguanosine

2',3'-dideoxyguanosine(DoG) has been demonstrated to inhibit duck hepatitis B virus(DHBV) replication in vivo in a duck model of HBV infection. In the current study, the in vitro antiviral effects of DoG on human and animal hepadnaviruses were investigated. Our results showed that DoG effectively inhibited HBV, DHBV, and woodchuck hepatitis virus(WHV)replication in hepatocyte-derived cells in a dose-dependent manner, with 50% effective concentrations(EC50) of 0.3 ± 0.05, 6.82 ± 0.25, and 23.0 ± 1.5 lmol/L, respectively. Similar to other hepadnaviral DNA polymerase inhibitors,DoG did not alter the levels of intracellular viral RNA but induced the accumulation of a less-than-full-length viral RNA species, which was recently demonstrated to be generated by RNase H cleavage of pgRNA. Furthermore, using a transient transfection assay, DoG showed similar antiviral activity against HBV wild-type, 3TC-resistant rtA181 V, and adefovirresistant rtN236T mutants. Our results suggest that DoG has potential as a nucleoside analogue drug with anti-HBV activity.     

Molecular epidemiology demonstrates that imported and local strains circulated during the 2014 dengue outbreak in Guangzhou,China

The dengue virus(DENV) is a vital global public health issue. The 2014 dengue epidemic in Guangzhou, China, caused approximately 40,000 cases of infection and five deaths. We carried out a comprehensive investigation aimed at identifying the transmission sources in this dengue epidemic. To analyze the phylogenetics of the 2014 dengue strains, the envelope(E) gene sequences from 17 viral strains isolated from 168 dengue patient serum samples were sequenced and a phylogenetic tree was reconstructed. All 17 strains were serotype Ⅰ strains, including 8genotype Ⅰ and 9 genotype V strains. Additionally, 6 genotype Ⅰ strains that were probably introduced to China from Thailand before 2009 were widely transmitted in the 2013 and 2014 epidemics, and they continued to circulate until 2015, with one affinis strain being found in Singapore. The other 2 genotype Ⅰ strains were introduced from the Malaya Peninsula in 2014. The transmission source of the 9 genotype Ⅴ strains was from Malaysia in 2014. DENVs of different serotypes and genotypes co-circulated in the 2014 dengue outbreak in Guangzhou. Moreover, not only had DENV been imported to Guangzhou, but it had also been gradually exported, as the viruses exhibited an enzootic transmission cycle in Guangzhou.