Epistemic_Statements  

CORD-19:07e78e218a159c35e9599e3751a99551a271597b JSONTXT 9 Projects

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Id Subject Object Predicate Lexical cue
T1 221-373 Epistemic_statement denotes Human can be infected through mucosal exposure to aerosols, or by direct contact of abrade skin with infectious material, derived from infected rodents.
T2 374-516 Epistemic_statement denotes Several arena-viruses cause hemorrhagic fever (HF) disease in humans and pose a great public health concern within the virus endemic regions .
T3 1317-1544 Epistemic_statement denotes Thus, LASV is estimated to infect several hundred thousand individuals yearly in its endemic regions of West Africa, resulting in a high number of Lassa fever (LF) cases associated with high morbidity and significant mortality.
T4 1864-2025 Epistemic_statement denotes Notably, increased traveling to and from endemic regions has led to the importation of LF into non-endemic metropolitan areas around the globe (Isaacson, 2001) .
T5 2026-2311 Epistemic_statement denotes Moreover, compelling evidence indicates that the globally distributed prototypic arenavirus LCMV is a neglected human pathogen of clinical significance, especially in cases of congenital infection leading to hydrocephalus, mental retardation and chorioretinitis (Barton et al., 2002) .
T6 3173-3426 Epistemic_statement denotes This provides investigators with a unique model system to investigate parameters that critically influence many aspects of virus-host interaction including the heterogeneity of phenotypic manifestations often associated with infection by the same virus.
T7 4952-5131 Epistemic_statement denotes The NP, the most abundant viral polypeptide both in infected cells and virions, is the main structural element of the viral RNP and plays an essential role in viral RNA synthesis.
T8 5132-5263 Epistemic_statement denotes Recent evidence indicates that NP exhibits also a type I interferon (IFN-I) counteracting activity (Martinez-Sobrido et al., 2009 .
T9 5461-5633 Epistemic_statement denotes The N-terminal domain has a potential cap-binding activity that could provide the host-derived primers to initiate transcription by the virus polymerase (Qi et al., 2010) .
T10 5634-5831 Epistemic_statement denotes In contrast, the C-terminal domain has a folding that mimics that of the DEDDH family of 3′-5′ exoribonucleases like the one associated with SARS Corona virus nsp14 protein (Eckerle et al., 2010) .
T11 6732-7077 Epistemic_statement denotes This assertion, however, is difficult to reconcile with the lack of anti-IFN activity associated with the NP of TACV (Martinez-Sobrido et al., 2007) and the finding that an LCMV with a mutant NP lacking the 3′-5′ exoribonuclease had a large decrease in fitness during its replication in IFN-deficient Vero cells (Martinez-Sobrido et al., 2009) .
T12 7342-7502 Epistemic_statement denotes GPC contains a 58amino-acid signal peptide (SSP) that is expressed as a stable polypeptide in infected cells and it remains associated to the GP complex (GPcx).
T13 8042-8497 Epistemic_statement denotes In LCMV-infected cells Z has been shown to interact with several cellular proteins including the promyelocytic leukemia (PML) protein and the eukaryote translation initiation factor 4E (eIF4E), which have been proposed to contribute to the noncytolytic nature of LCMV infection and repression of cap-dependent translation, respectively (Borden et al., 1998a (Borden et al., , 1998b Campbell Dwyer et al., 2000; Djavani et al., 2001; Volpon et al., 2010) .
T14 8498-8739 Epistemic_statement denotes Z has been shown to be the arenavirus counterpart of the M protein found in many other NS enveloped RNA viruses that plays a critical role in assembly and cell release of mature infectious virions Strecker et al., 2003; Urata et al., 2006) .
T15 9129-9478 Epistemic_statement denotes Subsequent bioinformatic analysis together with biochemical and MG-based functional studies have shown that LASV L protein is likely organized into three distinct structural domains and that at specific amino acid positions LASV L can be split into an N-and C-parts that are able to functionally trans-complement each other (Brunotte et al., 2011) .
T16 9479-9718 Epistemic_statement denotes Notably, the recent electron microscopy characterization of a functional MACV L protein has reveal a core ring-domain decorated by appendages, which may reflect a modular organization of the arenavirus polymerase (Kranzusch et al., 2010) .
T17 9989-10226 Epistemic_statement denotes However, many arenaviruses appear to use an alternative receptor (Kunz et al., 2004) , and human transferrin receptor 1 was identified as a cellular receptor used for entry of NW HF arenaviruses JUNV and MACV (Radoshitzky et al., 2007) .
T18 10594-10781 Epistemic_statement denotes LCMV mRNAs have 4-5 non-templated nt and a cap structure at their 5′-ends, which are likely obtained from cellular mRNAs via capsnatching mechanisms whose details remain to be determined.
T19 10782-10934 Epistemic_statement denotes A recently described endonuclease activity associated with the arenavirus L polymerase could play a critical role in this process (Morin et al., 2010) .
T20 10935-11230 Epistemic_statement denotes Transcription termination of subgenomic non-polyadenylated viral mRNAs were mapped to multiple sites within the distal side of the IGR (Meyer and Southern, 1994; Tortorici et al., 2001) , which suggested that the IGR acts as a bona fide transcription termination signal for the virus polymerase.
T21 12329-12591 Epistemic_statement denotes This reflects the fact that the template of the polymerases of NS RNA viruses is exclusively a nucleocapsid consisting of the genomic RNA tightly encapsidated by the NP, which associated with the virus polymerase proteins forms a ribonucleoprotein (RNP) complex.
T22 12883-13148 Epistemic_statement denotes However, following the pioneering work of Palese's group (Luytjes et al., 1989) , significant progress has been made in this area and for all NS RNA viruses, short model genomes (aka minigenomes (MG)) could be encapsidated and expressed by plasmid-encoded proteins.
T23 13149-13299 Epistemic_statement denotes Moreover, it has become possible to rescue infectious virus entirely from cloned cDNAs for members of all families of NS RNA viruses (Kawaoka, 2004) .
T24 13491-13950 Epistemic_statement denotes In addition, the possibility to generate predetermined specific mutations within the virus genome and analyze their phenotypic expression in vivo in the context of the virus natural infection is contributing very significantly to the elucidation of the molecular mechanisms underlying virus-host interactions at the cellular and molecular levels, which has provided investigators with novel and powerful approaches for the investigation of viral pathogenesis.
T25 14978-15321 Epistemic_statement denotes The use of MG-based assays facilitated mutation-function studies involving conserved acidic and basic amino acid residues within the N-and C-termini of LASV L protein uncovered several residues within the Nterminus of L that played a critical role in synthesis of viral mRNA but not in RNA replication (Hass et al., 2008; Lelke et al., 2010) .
T26 17165-17584 Epistemic_statement denotes Interestingly, arenaviruses do not have an obvious counterpart of M. However, Z has been shown to be the main driving force of arenavirus budding Strecker et al., 2003; Urata et al., 2006) , a process mediated by the Z late (L) domain motifs: PTAP and PPPY similar to those known to control budding of several other viruses including HIV and Ebola virus, via interaction with specific host cell proteins (Freed, 2002) .
T27 17934-18092 Epistemic_statement denotes Results derived from cryo-electron microscopy of arenavirus particles (Neuman et al., 2005) were also consistent with the role of Z as a functional M protein.
T28 18537-18684 Epistemic_statement denotes Subsequently the virus polymerase can adopt a replicase mode and moves across the IGR to generate a copy of the full-length antigenome RNA (agRNA).
T29 18685-18771 Epistemic_statement denotes This agRNA will serve as template for the synthesis of the GP (agS) and Z (agL) mRNAs.
T30 18893-19356 Epistemic_statement denotes The ability to generate recombinant arenaviruses with predetermined specific mutations and analyze their phenotypic expression in the context of the natural course of infection has opened new opportunities to investigate arenavirus-host interactions that influence a variable infection outcome, ranging from virus control and clearance by the host defenses to long-term chronic infection associated with subclinical disease, and severe acute disease including HF.
T31 19762-19972 Epistemic_statement denotes The supernatant from infected cells contained a mix of WT LCMV and rLCMV/VSVG and selection of rLCMV/VSVG was done via passages in S1P-deficient cells, where the LCMV WT could not produce an infectious progeny.
T32 19973-20091 Epistemic_statement denotes This approach was limited to the generation of rLCMV for the S segment and required a timeconsuming selection process.
T33 20092-20529 Epistemic_statement denotes These limitations were overcome by the rescue of infectious LCMV progeny entirely from cloned cDNAs using either a T7 RNA polymerase (RP) (Sanchez and de la Torre, 2006) or pol-I RP (Flatz et al., 2006) system to launch intracellular synthesis of S and L genome, or antigenome, RNA species that were subsequently replicated and transcribed by the virus polymerase complex reconstituted intracellularly via plasmid-supplied L and NP (Fig.
T34 20926-21367 Epistemic_statement denotes Intriguingly, the rescue of PICV and JUNV using the T7RP-based system did not require plasmid-supplied viral NP and L proteins (Albarino et al., 2009; Lan et al., 2009; Liang et al., 2009) , indicating that T7RP-mediated RNA synthesis produced both viral antigenome RNA species that were substrate for encapsidation and replication, and mRNAs that serve as template to produce levels of NP and L sufficiently high to facilitate virus rescue.
T35 21832-21987 Epistemic_statement denotes Reverse genetic approaches similar to those used to rescue infectious LCMV, PICV and JUNV from cloned cDNAs should be now applicable to other arenaviruses.
T36 22108-22226 Epistemic_statement denotes However, the T7RP has to be also provided either via transfection or by the use of a cell line stably expressing T7RP.
T37 22227-22496 Epistemic_statement denotes The non-templated G found at the 5′-end of arenavirus genome RNA species Raju et al., 1990) does not pose a problem as truncated T7RP promoters that direct RNA synthesis by T7RP starting with exhibit good levels of transcriptional activity (Sousa and Mukherjee, 2003) .
T38 22679-22980 Epistemic_statement denotes The generation of authentic 3′end viral genome termini using the T7RP is facilitated by the incorporation of the HDV ribozyme downstream to the T7RP termination sequence Sanchez and de la Torre, 2006) , but variability in the ribozyme cleavage efficiency could negatively affect the rescue efficiency.
T39 22981-23167 Epistemic_statement denotes T7RP-mediated transcription can trigger the IFN-I response, via RIG-I (Habjan et al., 2008) , which could compromise the rescue recombinant viruses with enhanced susceptibility to INF-I.
T40 23348-23714 Epistemic_statement denotes The pol I-based system was first used with influenza virus, whose replication occurs in the nucleus of infected cells (Neumann and Kawaoka, 2004) , but subsequently it has been used for the rescue of a variety of NS RNA viruses including bunyaviruses, filoviruses and arenaviruses (Flatz et al., 2006; Groseth et al., 2005; Habjan et al., 2008; Ogawa et al., 2007) .
T41 23715-23928 Epistemic_statement denotes A limitation of the pol-I system is the species-specific activity of the promoter (Comai, 2004; Neumann and Kawaoka, 2004) , which would prevent the use of a given pol-I construct with every cell line of interest.
T42 24151-24373 Epistemic_statement denotes Besides their pros and cons, both T7RP and pol-I systems have been proven to be similar efficient for the rescue of arenaviruses (Sanchez and de la Torre, 2006) , and other negativesense RNA viruses (Habjan et al., 2008) .
T43 24535-24717 Epistemic_statement denotes These cis-acting regulatory sequences play a critical role in the control of RNA synthesis by the virus polymerase, and minimal changes within them would likely prevent virus rescue.
T44 24908-25371 Epistemic_statement denotes The ability to generate recombinant arenaviruses with predetermined specific mutations and analyze their phenotypic expression in the context of the natural course of infection has opened new opportunities to investigate arenavirus-host interactions that influence a variable infection outcome, ranging from virus control and clearance by the host defenses to long-term chronic infection associated with subclinical disease, and severe acute disease including HF.
T45 25626-25924 Epistemic_statement denotes Likewise, rLCMV/VSVG was very instrumental in facilitating studies aimed at understanding the regulation of CD8+ T cell function within the infected brain , as well as how viruses can induce organspecific immune disease in the absence of molecular mimicry and without disruption of self tolerance .
T46 26104-26435 Epistemic_statement denotes Likewise, studies aimed at examining the critical role played by the S1Pmediated processing of arenavirus GPC in the virus life cycle were aided by the use of recombinant viruses where the S1P cleavage site within GPC was replaced by a canonical furin cleavage site (Albarino et al., 2009; Rojek et al., 2010; Urata et al., 2011) .
T47 26660-26830 Epistemic_statement denotes Despite the facile generation of these recombinant arenaviruses, the ability to rescue arenaviruses expressing additional genes of interest posed unexpected difficulties.
T48 27035-27141 Epistemic_statement denotes This problem was overcome by the generation of tri-segmented rLCMV (r3LCMV) containing 1L and 2S segments.
T49 27259-27485 Epistemic_statement denotes The rationale behind this approach was that the physical separation of GP and NP into two different S segments would represent a strong selective pressure to select and maintain a virus capable of packaging 1L and 2S segments.
T50 27564-27859 Epistemic_statement denotes Depending on the GOI expressed (protein function, size of the gene), these r3LCMV showed little or no attenuation in cultured cells and they exhibited long-term genetic stability as reflected by unaltered expression levels during serial virus passages of the GOI incorporated into the S segment.
T51 27860-28130 Epistemic_statement denotes The use of r3LCMV expressing appropriate reporter genes should facilitate the development of chemical screens to identify antiviral drugs, as well as siRNAbased genetic screens to identify host cell genes contributing to the different steps of the arenavirus life cycle.
T52 28131-28411 Epistemic_statement denotes In contrast, the use of r3LCMV to study virus-host interactions in mice has encountered some limitations due to the observation that even r3LCMV with WT growth properties in cultured cells exhibited an attenuated phenotype in the mouse due to reasons that remain to be determined.
T53 28714-28933 Epistemic_statement denotes Importantly, Rib reduced both morbidity and mortality in humans associated with LASV infection, and experimentally in MACV and JUNV infections, if given early in the course of clinical disease (Damonte and Coto, 2002) .
T54 28934-29107 Epistemic_statement denotes The mechanisms by which Rib exerts its anti-arenaviral action remain poorly understood, but likely involve targeting different steps of the virus life cycle (Parker, 2005) .
T55 29108-29295 Epistemic_statement denotes Two important limitations of the use of Rib therapy are the need of intravenous administration for optimal efficacy and significant side effects including anemia and congenital disorders.
T56 29559-29675 Epistemic_statement denotes However, these compounds displayed only modest and rather non-specific effects associated with significant toxicity.
T57 29676-29753 Epistemic_statement denotes Therefore there is a pressing need for novel effective anti-arenaviral drugs.
T58 30189-30381 Epistemic_statement denotes These findings illustrate how screening of complex chemical libraries using appropriate assays represents a powerful tool to identify candidate antiviral drugs with highly specific activities.
T59 30626-30940 Epistemic_statement denotes Targeting the biosynthetic processes, RNA replication and gene transcription, directed by the arenavirus polymerase complex Results from mutation-function studies have identified the core of the arenavirus genome promoter and uncover that both sequence specificity and structure are critical for promoter activity.
T60 30941-31214 Epistemic_statement denotes Disruption of the interaction between the arenavirus genome promoter and the virus polymerase complex would interfere with the essential biosynthetic processes of viral transcription and replication, which is expected to have a strong deleterious impact on virus viability.
T61 31215-31326 Epistemic_statement denotes Hence, small molecules that interfere specifically with this interaction could be efficacious antiviral agents.
T62 31327-31427 Epistemic_statement denotes Effector small molecules targeted at RNA may interfere with RNA functions by a number of mechanisms.
T63 31428-31553 Epistemic_statement denotes They can alter the functional three-dimensional structure of the RNA molecule, so that interaction with proteins is affected.
T64 31554-31660 Epistemic_statement denotes Also, as interface inhibitors, they may directly prevent the formation of competent RNA-protein complexes.
T65 31940-32157 Epistemic_statement denotes The potential of aminoglycosides as antiviral molecules by acting on RNA has been illustrated by their ability to disrupt selectively the HIV-1 Rev-RRE (Wang et al., 1997) and Tat-TAR (Wang et al., 1998) interactions.
T66 32158-32280 Epistemic_statement denotes Similar approaches should be applicable to inhibit the interaction between the arenavirus promoter and polymerase complex.
T67 32873-33025 Epistemic_statement denotes This finding has uncovered the possibility of using small molecules to disrupt L-L interaction as a novel strategy to inhibit arenavirus multiplication.
T68 33332-33552 Epistemic_statement denotes Intriguingly, studies on LCMV and JUNV infection of cells deficient in S1P indicated that the appearance of viral variants capable of growing independently of S1P-mediated processing of GPC appears to be highly unlikely.
T69 33553-33725 Epistemic_statement denotes These findings strongly support the idea that inhibitors of S1P-mediated processing of GPC would represent promising anti-arenaviral drug candidates (Rojek et al., , 2010 .
T70 34266-34438 Epistemic_statement denotes Several peptide and non-peptide-based S1P inhibitors have been documented but their lack of cell permeability would pose severe limitations to their use as antiviral drugs.
T71 34439-34634 Epistemic_statement denotes Recently, decanoylated chloromethylketone (CMK)-derivatized peptides containing the RRLL recognition sequence of S1P have been shown to act as potent suicide inhibitors of S1P catalytic activity.
T72 34635-34821 Epistemic_statement denotes These drugs cause irreversible inhibition of the catalytic activity of S1P against host cell and pathogen derived targets, which might result in unacceptable levels of cellular toxicity.
T73 34984-35216 Epistemic_statement denotes In addition, PF-429242 was shown to inhibit efficiently S1P-mediated processing of arenavirus GPC, which correlated with the drug's ability to interfere with propagation of both LCMV and LASV in cultured cells (Urata et al., 2011) .
T74 35347-35580 Epistemic_statement denotes For many characterized viral budding proteins, their budding activity requires interaction, via its L domains, with specific host cellular factors including members of the ESCRT machinery within the endosomal/MVB pathway of the cell.
T75 35581-35716 Epistemic_statement denotes In this regard TSG101, a member of the ESCRT-I complex, has been identified as a host cellular protein required for Z-mediated budding.
T76 36097-36323 Epistemic_statement denotes Knowledge from these studies may uncover novel targets and facilitate the development of screening processes to indentify small molecules capable of disrupting these interactions and thereby interfering with virus propagation.
T77 36324-36588 Epistemic_statement denotes The ESCRT machinery participates in a variety of processes required for normal cell physiology (Carlton, 2010; Morita et al., 2010) and therefore longterm disruption of the normal function of ESCRT components is likely to result in unacceptable levels of toxicity.
T78 36589-36786 Epistemic_statement denotes However, arenavirus induced HF are acute disease processes, and it is plausible that short term inhibition of ESCRT members to combat an acute HF arenaviral disease may cause only limited toxicity.
T79 37369-37455 Epistemic_statement denotes Despite its success, there are some limitations associated with the Candid #1 vaccine.
T80 37456-37641 Epistemic_statement denotes Key concerns relate to the lack of information about the genetic composition of the Candid #1 vaccine and limited knowledge regarding the viral genetic determinants of JUNV attenuation.
T81 37719-37925 Epistemic_statement denotes Therefore, every amplification step to increase vaccine production may result in the appearance or enrichment within the virus population of genotypes within the potential of exhibiting increased virulence.
T82 37926-38120 Epistemic_statement denotes As the genetic markers associated with Candid #1 attenuation are not clearly established, the emergence of potentially pathogenic variants within the Candid #1 population is difficult to assess.
T83 38121-38460 Epistemic_statement denotes The potential genetic instability of Candid #1 is illustrated by the observation that Candid #1 isolates obtained from blood mononuclear cells of vaccinated rhesus monkeys showed a 1000 fold range of virulence, with some isolates exhibiting up to~100 fold higher virulence compared to the parental Candid #1 (Enria and Barrera Oro, 2002) .
T84 38461-38775 Epistemic_statement denotes Reverse genetic approaches could facilitate the development of a safer vaccine against AHF, and other HF arenaviral diseases, by facilitating the generation of molecular clones of genetically well-defined live-attenuated vaccine strains with the ability to induce strong protective immunity (Emonet et al., 2011) .
T85 39012-39142 Epistemic_statement denotes This finding led to examine the potential of LCMV as a viral vector system for immunization against non-LCMV antigens of interest.
T86 39143-39436 Epistemic_statement denotes These studies showed that LCMV GPC could be replaced by a protein antigen of interest and the corresponding rLCMV, grown in cells expressing GPC, were able to induce good immune responses against the foreign protein while immunized mice remained free of disease symptoms (Flatz et al., 2010) .
T87 39437-39573 Epistemic_statement denotes However, the potential problem associated with pre-existing immunity against LCMV in human populations may limit the use of this system.
T88 39838-39911 Epistemic_statement denotes A similar strategy could be implemented to increase the safety Candid #1.
T89 39912-40029 Epistemic_statement denotes Among HF arenaviruses, LASV poses the main concern due to its vast endemic region and size of the population at risk.
T90 40030-40293 Epistemic_statement denotes The geographic and socio-economic conditions intrinsic to the LASV endemic regions would pose significant difficulties for individuals at risk to have ready access to medical care, including antiviral drugs, to be treated against symptoms of LASV induced disease.
T91 40294-40396 Epistemic_statement denotes Therefore, vaccination of the population at risk would be likely to provide a more effective strategy.
T92 40397-40563 Epistemic_statement denotes However, a vaccination approach against LF similar to the one used against AHF is currently unfeasible because an attenuated strain for LASV has not been established.
T93 40771-40953 Epistemic_statement denotes Recombinant vaccinia viruses expressing LASV NP or GP have been shown to provide cellmediated immunity against LASV in guinea pigs and non-human primates (Fisher-Hoch et al., 2000) .
T94 40954-41092 Epistemic_statement denotes However, this approach would face the problem of the risk of using a vaccinia virus based vector in a population with high HIV prevalence.
T95 41386-41557 Epistemic_statement denotes Likewise, the alphavirus Venezuelan equine encephalitis virus (Lee et al., 2005) , and the 17D Yellow fever vaccine (Bredenbeek et al., 2006) have shown promising results.
T96 41558-41791 Epistemic_statement denotes Whether these recombinant vaccines provide long-term protection remains to be determined, an issue highly relevant in the case of LF due to a cumulative lifetime risk of exposure to LF vaccine within the West Africa human population.
T97 41946-42188 Epistemic_statement denotes Thus, a reassortant (called ML29) between Mopeia, an OW arenavirus considered to be non-pathogenic to humans, and LASV has shown some promising results (Carrion et al., 2007) , but detailed safety and efficacy studies have not been completed.
T98 42189-42465 Epistemic_statement denotes An alternative approach for the development of a LF vaccine would be the use of reverse genetics to generate biologically contained versions of LASV in a similar way as described for Ebola virus (Halfmann et al., 2008) and influenza (Martinez-Sobrido and Garcia-Sastre, 2010).
T99 42621-42789 Epistemic_statement denotes Likewise, the use of live-attenuated tri-segmented Candid #1 expressing relevant LASV T-cell epitopes could be used to induce protective immunity against JUNV and LASV.
T100 43227-43672 Epistemic_statement denotes The ability to manipulate the LCMV genome and generate rLCMV with predetermined mutations would allow investigators to gain a detailed understanding of the roles played by the different viral genes in virus-host interactions resulting in very different phenotypic outcomes ranging from an acute and fatal meningitis to immunosuppression and chronic infections that although clinically silent can be associated with neurobehavioral abnormalities.
T101 44291-44641 Epistemic_statement denotes Likewise, the implementation of siRNA-based screens in the context of cell-based MG assays should facilitate the identification of host cell proteins that play key roles in arenavirus RNA replication and gene expression and thereby open potential for discovering novel targets that could be used in the development of effective anti-arenaviral drugs.