Induction and suppression of tick cell antiviral RNAi responses by tick-borne flaviviruses

Schnettler, Esther; Tykalová, Hana; Watson, Michael; Sharma, Madhu; Sterken, Mark G.; Obbard, Darren J.; Lewis, Samuel H.; McFarlane, Melanie; Bell‐Sakyi, Lesley; Barry, Gerald; Weisheit, Sabine; Best, Sonja M.; Kühn, Richard; Pijlman, Gorben P.; Chase-Topping, Margo; Gould, Ernest A.; Grubhoffer, Libor; Fazakerley, John K.; Kohl, Alain

doi:10.1093/nar/gku657

Cited by 127 publications

(189 citation statements)

References 65 publications

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“…Needless to say that antiviral RNAi was reported also from other hexapods, such as silk moth Zografidis et al, 2015). Antiviral RNAi was also reported for Chelicerata (ticks and mites (Schnettler et al, 2014;Hoy et al, 2016)) or Crustacea (shrimps (Huang and Zhang, 2013;Sabin and Cherry, 2013;Yang et al, 2014b;Jariyapong et al, 2015;Maralit et al, 2015;Hoy et al, 2016).…”

Section: Antiviral Rnaimentioning

confidence: 88%

“…RNAi is functional across other arthropods subphyla, including Chelicerata (ticks and mites (Kurscheid et al, 2009;Schnettler et al, 2014;Hoy et al, 2016)) and Crustacea (shrimps Huang and Zhang, 2013;Sabin and Cherry, 2013;Yang et al, 2014b;Jariyapong et al, 2015;Maralit et al, 2015;Hoy et al, 2016). We did not find published functional RNAi data for Myriapoda but genomic analyses show that they have the necessary machinery (Palmer and Jiggins, 2015).…”

Section: Rnai Pathway In Arthropodsmentioning

confidence: 99%

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Literature review of baseline information to support the risk assessment of RNAi‐based GM plants

Pačes

Nič²,

Novotný³

et al. 2017

EFS3

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This report is the outcome of an EFSA procurement aiming at investigating and summarising the state of knowledge on (I) the mode-of-action of dsRNA and miRNA pathways, (II) the potential for nontarget gene regulation by dsRNA-derived siRNAs or miRNAs, (III) the determination of siRNA pools in plant tissues and the importance of individual siRNAs for silencing. The report is based on a comprehensive and systematic literature search, starting with the identification and retrieval of~190,000 publications related to the research area and further filtered down with keywords to produce focused collections used for subsequent screening of titles and abstracts. The report is comprised of an (I) Introduction to the field of small RNAs, (II) a Data and Methodologies section containing strategies used for literature search and study selection, and (III) the Results of the literature review organized according to the three main procurement tasks. The outcome of the first task reviews dsRNA and miRNA pathways in mammals (including humans), birds, fish, arthropods, annelids, molluscs, nematodes, and plants. Eight taxon-dedicated chapters are based on~1,400 cumulative references chosen from~10,000 inspected titles and abstracts. We review conserved and divergent aspects of small RNA pathways and dsRNA responses in animals and plants including structure and function of key proteins as well as four basic mechanisms: genome-encoded posttranscriptional regulations (miRNA), degradation of RNAs by short interfering RNA pools generated from long dsRNA (RNAi), transcriptional silencing, and sequence-independent responses to dsRNA. The outcome of the second task focuses on base pairing between small RNAs and their target RNAs and predictability of biological effects of small RNAs in animals and plants. The outcome of the last task reviews methodology, siRNA pools, and movement of small RNAs in plants. Potential transfer of small RNAs between species and circulating miRNAs in mammals is described in the final chapter.

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Section: Antiviral Rnaimentioning

confidence: 88%

Section: Rnai Pathway In Arthropodsmentioning

confidence: 99%

Literature review of baseline information to support the risk assessment of RNAi‐based GM plants

Pačes

Nič²,

Novotný³

et al. 2017

EFS3

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“…In Culex mosquitoes-the predominant group of WNV vectors-virus-specific siRNAs are highly abundant, whereas viral piRNAs (vpiRNAs) appear to be absent (14,21). For flaviviruses, three putative viral suppressors of RNAi (VSRs) have been identified in vitro: the NS4B and NS3 proteins of DENV type 2 (DENV-2) and the noncoding subgenomic flavivirus RNA (sfRNA) for WNV (22)(23)(24).…”

mentioning

confidence: 99%

“…The conservation of sfRNA production by MBFs, TBFs, and ISFs emphasizes the putative importance of sfRNA production in arthropods (35). So far, it has been demonstrated that sfRNA acts as a suppressor of miRNA-and siRNA-mediated RNAi in vitro in both mammalian and arthropod cells (23,37). The highly abundant sfRNA most likely acts as a decoy substrate for Dicer to prevent it from cleaving other double-stranded RNA (dsRNA) molecules.…”

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confidence: 99%

Noncoding Subgenomic Flavivirus RNA Is Processed by the Mosquito RNA Interference Machinery and Determines West Nile Virus Transmission by Culex pipiens Mosquitoes

Göertz

Fros

Miesen

et al. 2016

J Virol

114

163

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Flaviviruses, such as Zika virus, yellow fever virus, dengue virus, and West Nile virus (WNV), are a serious concern for human health. Flaviviruses produce an abundant noncoding subgenomic flavivirus RNA (sfRNA) in infected cells. sfRNA results from stalling of the host 5=-3= exoribonuclease XRN1/Pacman on conserved RNA structures in the 3= untranslated region (UTR) of the viral genomic RNA. sfRNA production is conserved in insect-specific, mosquito-borne, and tick-borne flaviviruses and flaviviruses with no known vector, suggesting a pivotal role for sfRNA in the flavivirus life cycle. Here, we investigated the function of sfRNA during WNV infection of Culex pipiens mosquitoes and evaluated its role in determining vector competence. An sfRNA1-deficient WNV was generated that displayed growth kinetics similar to those of wild-type WNV in both RNA interference (RNAi)-competent and -compromised mosquito cell lines. Small-RNA deep sequencing of WNV-infected mosquitoes indicated an active small interfering RNA (siRNA)-based antiviral response for both the wild-type and sfRNA1-deficient viruses. Additionally, we provide the first evidence that sfRNA is an RNAi substrate in vivo. Two reproducible small-RNA hot spots within the 3= UTR/sfRNA of the wild-type virus mapped to RNA stem-loops SL-III and 3= SL, which stick out of the three-dimensional (3D) sfRNA structure model. Importantly, we demonstrate that sfRNA-deficient WNV displays significantly decreased infection and transmission rates in vivo when administered via the blood meal. Finally, we show that transmission and infection rates are not affected by sfRNA after intrathoracic injection, thereby identifying sfRNA as a key driver to overcome the mosquito midgut infection barrier. This is the first report to describe a key biological function of sfRNA for flavivirus infection of the arthropod vector, providing an explanation for the strict conservation of sfRNA production. IMPORTANCEUnderstanding the flavivirus transmission cycle is important to identify novel targets to interfere with disease and to aid development of virus control strategies. Flaviviruses produce an abundant noncoding viral RNA called sfRNA in both arthropod and mammalian cells. To evaluate the role of sfRNA in flavivirus transmission, we infected mosquitoes with the flavivirus West Nile virus and an sfRNA-deficient mutant West Nile virus. We demonstrate that sfRNA determines the infection and transmission rates of West Nile virus in Culex pipiens mosquitoes. Comparison of infection via the blood meal versus intrathoracic injection, which bypasses the midgut, revealed that sfRNA is important to overcome the mosquito midgut barrier. We also show that sfRNA is processed by the antiviral RNA interference machinery in mosquitoes. This is the first report to describe a pivotal biological function of sfRNA in arthropods. The results explain why sfRNA production is evolutionarily conserved. Viruses from the genus Flavivirus (family Flaviviridae), such as the highly pathogenic dengue virus (DENV...

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“…Although specific Ixodes spp. transcripts have been implicated in TBFV infection in tick cell cultures (46)(47)(48), ex vivo organ cultures can provide a means to more precisely probe tissue-specific vector interactions.…”

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confidence: 99%

Flavivirus Infection ofIxodes scapularis(Black-Legged Tick)Ex VivoOrganotypic Cultures and Applications for Disease Control

Grabowski¹,

Tsetsarkin

Long³

et al. 2017

mBio

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Ixodes scapularis ticks transmit many infectious agents that cause disease, including tick-borne flaviviruses (TBFVs). TBFV infections cause thousands of human encephalitis cases worldwide annually. In the United States, human TBFV infections with Powassan virus (POWV) are increasing and have a fatality rate of 10 to 30%. Additionally, Langat virus (LGTV) is a TBFV of low neurovirulence and is used as a model TBFV. TBFV replication and dissemination within I. scapularis organs are poorly characterized, and a deeper understanding of virus biology in this vector may inform effective countermeasures to reduce TBFV transmission. Here, we describe short-term, I. scapularis organ culture models of TBFV infection. Ex vivo organs were metabolically active for 9 to 10 days and were permissive to LGTV and POWV replication. Imaging and videography demonstrated replication and spread of green fluorescent protein-expressing LGTV in the organs. Immunohistochemical staining confirmed LGTV envelope and POWV protein synthesis within the infected organs.LGTV-and POWV-infected organs produced infectious LGTV and POWV; thus, the ex vivo cultures were suitable for study of virus replication in individual organs. LGTVand POWV-infected midgut and salivary glands were subjected to double-stranded RNA (dsRNA) transfection with dsRNA to the LGTV 3= untranslated region (UTR), which reduced infectious LGTV and POWV replication, providing a proof-of-concept use of RNA interference in I. scapularis organ cultures to study the effects on TBFV replication. The results contribute important information on TBFV localization within ex vivo I. scapularis organs and provide a significant translational tool for evaluating recombinant, live vaccine candidates and potential tick transcripts and proteins for possible therapeutic use and vaccine development to reduce TBFV transmission.IMPORTANCE Tick-borne flavivirus (TBFV) infections cause neurological and/or hemorrhagic disease in humans worldwide. There are currently no licensed therapeutics or vaccines against Powassan virus (POWV), the only TBFV known to circulate in North America. Evaluating tick vector targets for antitick vaccines directed at reducing TBFV infection within the arthropod vector is a critical step in identifying efficient approaches to controlling TBFV transmission. This study characterized infection of female Ixodes scapularis tick organ cultures of midgut, salivary glands, and synganglion with the low-neurovirulence Langat virus (LGTV) and the more pathogenic POWV. Cell types of specific organs were susceptible to TBFV infection, and a difference in LGTV and POWV replication was noted in TBFV-infected organs. This tick organ culture model of TBFV infection will be useful for various applications,

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Induction and suppression of tick cell antiviral RNAi responses by tick-borne flaviviruses

Cited by 127 publications

References 65 publications

Literature review of baseline information to support the risk assessment of RNAi‐based GM plants

Literature review of baseline information to support the risk assessment of RNAi‐based GM plants

Noncoding Subgenomic Flavivirus RNA Is Processed by the Mosquito RNA Interference Machinery and Determines West Nile Virus Transmission by Culex pipiens Mosquitoes

Flavivirus Infection ofIxodes scapularis(Black-Legged Tick)Ex VivoOrganotypic Cultures and Applications for Disease Control

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