Epidemiological Survey of Severe Fever with Thrombocytopenia Syndrome Virus in Ticks in Nagasaki, Japan

Hayasaka, Daisuke; Shimada, Satoshi; Aoki, Kotaro; Takamatsu, Yuki; Uchida, Leo; Horio, Masahiro; Yu, Fangfang; Morita, Kouichi

doi:10.2149/tmh.2015-01

Cited by 19 publications

(15 citation statements)

References 11 publications

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“…The severe fever with thrombocytopenia syndrome virus (SFTSV) is a tick-borne emerging pathogen, causing high fever and drastic loss of leukocytes and platelets and multiorgan failure with high mortality in severe patients (12). There have been over 3000 cases reported in China since 2009 (13), and the virus has also been isolated recently in Japan and Korea and from patients and ticks (14,15). SFTSV possesses a genome with three ssRNA segments of negative sense, L, M, and S. Whereas the L segment encodes an RNA-dependent RNA polymerase, and M encodes two envelope proteins, Gn and Gc, the S segment, is an ambisense RNA with two opposite open reading frames encoding a nucleoprotein (NP) and a nonstructural protein (NSs) (12).…”

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confidence: 99%

Suppression of the IFN-α and -β Induction through Sequestering IRF7 into Viral Inclusion Bodies by Nonstructural Protein NSs in Severe Fever with Thrombocytopenia Syndrome Bunyavirus Infection

Bai

et al. 2019

The Journal of Immunology

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Induction of type I IFNs during viral infection is crucial for host defense. IRF 3 and IRF7 play a critical role as key transcription factors in the activation of the IFN induction. Viruses have evolved a variety of strategies to evade innate immunity. Our previous studies have shown that the nonstructural protein (NSs) of the severe fever with thrombocytopenia syndrome virus (SFTSV) can suppress the IFN-β induction through its interaction with tank-binding kinase-1 and sequestering the inhibitor of nuclear factor kappa B kinase(IKK) complex into the inclusion bodies formed by NSs. In this study, we characterized the unique function of IRF7 in innate immunity and its role in inducing IFN-α in particular, regulated by NSs during the SFTSV infection in several cell types of human origin. Whereas IRF3 is constitutively expressed, IRF7 was significantly induced differentially in various cell types in response to SFTSV infection, promoted the induction of IFN-α2 and -α4, and further induced IFN-β, thus contributing to suppressing the viral replication. Our data indicate that NSs directly interacted with and sequestered IRF7 into the inclusion bodies, which is different from IRF3 indirectly interacting with NSs. Although interaction of NSs with IRF7 did not inhibit IRF7 phosphorylation, p-IRF7 was trapped in the inclusion bodies, resulting in a significant reduction of the IFN-α2 and -α4 induction and therefore enhanced viral replication. Interaction of the viral NSs with both IRF7 and IRF3 and subsequent sequestration of these transcription factors into viral inclusion bodies, a unique strategy used by this phlebovirus, may ensure effective evasion and suppression of host innate immunity.

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confidence: 99%

Suppression of the IFN-α and -β Induction through Sequestering IRF7 into Viral Inclusion Bodies by Nonstructural Protein NSs in Severe Fever with Thrombocytopenia Syndrome Bunyavirus Infection

Bai

et al. 2019

The Journal of Immunology

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“…SFTS caused by SFTSV infection was first emerged in China in 2009 [ 3 ], followed by reports from other Asian countries. At present no effective therapies or vaccines are available, and SFTS is associated with high rates of fatality [ 1 , 5 , 30 ]. In addition to reducing rates of tick bite, early diagnosis and treatment are important.…”

Section: Discussionmentioning

confidence: 99%

Establishment of national reference for bunyavirus nucleic acid detection kits for diagnosis of SFTS virus

Dongting

2017

Virol J

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BackgroundSevere fever with thrombocytopenia syndrome (SFTS) caused by SFTS virus (SFTSV) usually have a high fatality. At present no effective therapy or vaccine are available, so early diagnosis of SFTS is crucial to prevent and control SFTSV infection. This study aimed to establish a national reference for these diagnostic kits of SFTSV genome and make the diagnosis of the disease effective.MethodsSix SFTSV strains isolated from different regions, and five relative viruses with similar clinical manifestations were selected as positive and negative references and assessed using real time quantitative PCR (q-PCR) using specific primers and probe and two commercial kits. The stability of the references was also assessed at 37 °C, room temperature or -70 °C for 8 days, 14 days or 8 months respectively, or following several cycles of freezing-thawing. Collaborative calibration of the references was performed by three labs.ResultsThe references indicated good accuracy and specificity. The lowest detection limit was 102 U/mL. The accuracy was coefficient of variation less than 5%. The references were highly stable at high temperatures and after long storing and freezing-thawing treatment.ConclusionsWe successfully established a national reference with good accuracy, high specificity, sensitivity and stability, which can be applied for quality control of commercial SFTSV diagnostic kits, thus preventing and controlling SFTS.Trial registrationThe references have been finished and it was retrospectively registered in the following article.Electronic supplementary materialThe online version of this article (doi:10.1186/s12985-017-0682-z) contains supplementary material, which is available to authorized users.

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“…SFTSV was also detected in I. nipponensis ticks in South Korea [3]. A study in Japan suggested that SFTSV positivity rates were considered to be very low in ticks and viral loads were also very limited, as SFTSV was not detected in 2222 adult and nymph ticks collected from vegetation [26]. These results suggested that several tick species might act as vectors for SFTSV, however, the presence of viral RNA in ticks does not verify that the tick can transmit the virus.…”

Section: Transmission Of Sftsv To Animals By Ticksmentioning

confidence: 92%

Role of three tick species in the maintenance and transmission of Severe Fever with Thrombocytopenia Syndrome Virus

Zhang

Liu

et al. 2020

PLoS Negl Trop Dis

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Severe fever with thrombocytopenia syndrome virus (SFTSV) is a novel phlebovirus in the Bunyaviridae family, causing SFTS with high mortality rate. Haemaphysalis longicornis ticks has been demonstrated as a competent vector of SFTSV by experimental transmission study and field study. However, there has been query whether other tick species that infest human beings in the SFTS endemic regions are capable of transmitting the pathogen. Here by performing experimental transmission study, we compared the capable of transmitting SFTSV among Ixodes sinensis, Ixodes persulcatus and Dermacentor silvarum ticks. The transovarial transmission was seen in the I. sinensis ticks with a rate of 40%, but neither in I. persulcatus nor in D. silvarum ticks. I. sinensis ticks also have the ability to transmit SFTSV horizontally to uninfected mice at 7 days after feeding, but not for I. persalcatus or D. silvarum ticks. In the transstadial transmission of I. persulcatus and D. silvarum ticks, I. persulcatus ticks were tested negative from larvae to adults. But the D. silvarum ticks were tested positive from larvae to nymphs, with the positive rate of 100% (10/10) for engorged larval ticks and 81.25% (13/16) for molted nymphs. However, the mice bitten by SFTSV-infected D. silvarum nymphs were negative for SFTSV detection. Therefore, there is not enough evidence to prove the transstadial transmission of SFTSV in I. persalcatus and D. silvarum ticks.

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Epidemiological Survey of Severe Fever with Thrombocytopenia Syndrome Virus in Ticks in Nagasaki, Japan

Cited by 19 publications

References 11 publications

Suppression of the IFN-α and -β Induction through Sequestering IRF7 into Viral Inclusion Bodies by Nonstructural Protein NSs in Severe Fever with Thrombocytopenia Syndrome Bunyavirus Infection

Suppression of the IFN-α and -β Induction through Sequestering IRF7 into Viral Inclusion Bodies by Nonstructural Protein NSs in Severe Fever with Thrombocytopenia Syndrome Bunyavirus Infection

Establishment of national reference for bunyavirus nucleic acid detection kits for diagnosis of SFTS virus

Role of three tick species in the maintenance and transmission of Severe Fever with Thrombocytopenia Syndrome Virus

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