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Background: Severe fever with thrombocytopenia syndrome (SFTS) was an emerging hemorrhagic fever that was caused by a tick-borne bunyavirus, SFTSV. Although SFTSV nonstructural protein can inhibit type I interferon (IFN-I) production Ex Vivo and IFN-I played key role in resistance SFTSV infection in animal model, the role of IFN-I in patients is not investigated. Methods: We have assayed the concentration of IFN-α, a subtype of IFN-I as well as other cytokines in the sera of SFTS patients and the healthy population with CBA (Cytometric bead array) assay. Results: The results showed that IFN-α, tumor necrosis factor (TNF-α), granulocyte colony-stimulating factor (G-CSF), interferon-γ (IFN-γ), macrophage inflammatory protein (MIP-1α), interleukin-6 (IL-6), IL-10, interferon-inducible protein (IP-10), monocyte chemoattractant protein (MCP-1) were significantly higher in SFTS patients than in healthy persons (p < 0.05); the concentrations of IFN-α, IFN-γ, G-CSF, MIP-1α, IL-6, and IP-10 were significant higher in severe SFTS patients than in mild SFTS patients (p < 0.05). Conclusion: The concentration of IFN-α as well as other cytokines (IFN-γ, G-CSF, MIP-1α, IL-6, and IP-10) is correlated with the severity of SFTS, suggesting that type I interferon may not be significant in resistance SFTSV infection in humans and it may play an import role in cytokine storm. [ABSTRACT FROM AUTHOR]

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Severe fever with thrombocytopenia syndrome (SFTS) is an emerging hemorrhagic fever in East Asia caused by SFTS virus (SFTSV), a newly discovered phlebovirus. The Haemaphysalis longicornis tick has been suspected to be the vector of SFTSV. To determine whether SFTSV can be transmitted among ticks, from ticks to animals, and from animals to ticks, we conducted transmission studies between developmental stages of H. longicornis ticks and between ticks and mice. Using reverse transcription PCR, we also analyzed the prevalence of SFTSV infection among H. longicornis ticks collected from vegetation in Shandong Province, China. Our results showed a low prevalence of SFTSV among collected ticks (0.2%, 8/3,300 ticks), and we showed that ticks fed on SFTSV-infected mice could acquire the virus and transstadially and transovarially transmit it to other developmental stages of ticks. Furthermore, SFTSV-infected ticks could transmit the virus to mice during feeding. Our findings indicate ticks could serve as a vector and reservoir of SFTSV. [ABSTRACT FROM AUTHOR]

Background: The complete genome of Rana grylio virus (RGV) was sequenced and analyzed recently, which revealed that RGV 50L had homologues in many iridoviruses with different identities; however, the characteristics and functions of 50L have not been studied yet. Methodology/Principal Findings: We cloned and characterized RGV50L, and revealed 50L functions in virus assembly and gene regulation. 50L encoded a 499-amino acid structural protein of about 85 kDa in molecular weight and contained a nuclear localization signal (NLS) and a helix- extension-helix motif. Drug inhibition assay demonstrated that 50L was an immediate-early (IE) gene. Immuno-fluorescence assay revealed that 50L appeared early and persisted in RGV-infected cells following two distribution patterns. One pattern was that 50L exhibited a cytoplasm-nucleus- viromatrix distribution pattern, and mutagenesis of the NLS motif revealed that localization of 50L in the nucleus was NLS-dependent; the other was that 50L co-localized with viral matrix which plays important roles in virus assembly and the life circle of viruses. Conclusions/Significance: RGV 50L is a novel iridovirus IE gene encoded structural protein which plays important roles in virus assembly. [ABSTRACT FROM AUTHOR]

Background: Envelope protein 53R was identified from frog Rana grylio virus (RGV), a member of the family Iridoviridae, and it plays an important role in the virus assembly. Although inhibition of iridovirus major capsid protein (MCP) by small hairpin RNAs (shRNAs) has been shown to cause resistance to viral infection in vitro, RNA interference (RNAi) to inhibit aquatic animal virus envelope protein gene product has not been reported. Methodology: We devised artificial microRNAs (amiRNAs) that target a viral envelope protein gene RGV 53R. By incorporating sequences encoding amiRNAs specific to 53R of RGV into pre-miRNA155 (pSM155) vectors, which use the backbone of natural miR-155 sequence and could intracellularly express 53R-targeted pre-amiRNAs. The pre-amiRNAs could be processed by the RNase III-like enzyme Dicer into 21-25 nt amiRNAs (amiR-53Rs) in fish cell lines. The levels of 53R expression were analyzed through real-time PCR and RGV virions assembly were observed by electronic microscopy in fish cells transfected with or without amiR-53Rs at 72 h of RGV infection. Conclusion/Significance: The results argue that viral envelope protein RGV 53R can be silenced and the virions assembly was deficient by amiR-53R-1, and further identified the first amiRNA of envelope protein gene from iridovirus that was able to cause resistance to virus infection in fish cells. The data demonstrate that the viral infection is efficiently suppressed (58%) by amiR-53R-1 targeting positon 36-57 of RGV 53R. Moreover, electron microscopic observations revealed virion assembly defect or reduced virions assembly capacity was closely correlated to expression of amiR-53R-1. Based on real time PCR of the Mx gene, we found no evidence of activation of IFN by amiR-53R-1. [ABSTRACT FROM AUTHOR]