scholarly journals Rift Valley Fever Virus Nonstructural Protein NSs Promotes Viral RNA Replication and Transcription in a Minigenome System

2005 ◽  
Vol 79 (9) ◽  
pp. 5606-5615 ◽  
Author(s):  
Tetsuro Ikegami ◽  
C. J. Peters ◽  
Shinji Makino
Keyword(s):  
Rift Valley Fever ◽  
Rna Synthesis ◽  
Nonstructural Protein ◽  
Rift Valley Fever Virus ◽  
Rna Replication ◽  
Valley Fever ◽  
Rna Transcripts ◽  
L Proteins ◽  
Bunyamwera Virus ◽  
Minigenome System

ABSTRACT Rift Valley fever virus (RVFV), which belongs to the genus Phlebovirus, family Bunyaviridae, has a tripartite negative-strand genome (S, M, and L segments) and is an important mosquito-borne pathogen for domestic animals and humans. We established an RVFV T7 RNA polymerase-driven minigenome system in which T7 RNA polymerase from an expression plasmid drove expression of RNA transcripts for viral proteins and minigenome RNA transcripts carrying a reporter gene between both termini of the M RNA segment in 293T cells. Like other viruses of the Bunyaviridae family, replication and transcription of the RVFV minigenome required expression of viral N and L proteins. Unexpectedly, the coexpression of an RVFV nonstructural protein, NSs, with N and L proteins resulted in a significant enhancement of minigenome RNA replication. Coexpression of NSs protein with N and L proteins also enhanced minigenome mRNA transcription in the cells expressing viral-sense minigenome RNA transcripts. NSs protein expression increased the RNA replication of minigenomes that originated from S and L RNA segments. Enhancement of minigenome RNA synthesis by NSs protein occurred in cells lacking alpha/beta interferon (IFN-α/β) genes, indicating that the effect of NSs protein on minigenome RNA replication was unrelated to a putative NSs protein-induced inhibition of IFN-α/β production. Our finding that RVFV NSs protein augmented minigenome RNA synthesis was in sharp contrast to reports that Bunyamwera virus (genus Bunyavirus) NSs protein inhibits viral minigenome RNA synthesis, suggesting that RVFV NSs protein and Bunyamwera virus NSs protein have distinctly different biological roles in viral RNA synthesis.

scholarly journals The S Segment of Rift Valley Fever Phlebovirus (Bunyaviridae) Carries Determinants for Attenuation and Virulence in Mice

2000 ◽  
Vol 74 (3) ◽  
pp. 1538-1543 ◽  
Author(s):  
P. Vialat ◽  
A. Billecocq ◽  
A. Kohl ◽  
M. Bouloy
Keyword(s):  
Rift Valley ◽  
Rift Valley Fever ◽  
Nonstructural Protein ◽  
Rift Valley Fever Virus ◽  
Virulent Strain ◽  
Coding Region ◽  
Valley Fever ◽  
Attenuated Virus ◽  
Infected Cells

ABSTRACT Unlike all the other Rift Valley fever virus strains (Bunyaviridae, Phlebovirus) studied so far, clone 13, a naturally attenuated virus, does not form the filaments composed of the NSs nonstructural protein in the nuclei of infected cells (R. Muller, J. F. Saluzzo, N. Lopez, T. Drier, M. Turell, J. Smith, and M. Bouloy, Am. J. Trop. Med. Hyg. 53:405–411, 1995). This defect is correlated with a large in-frame deletion in the NSs coding region of the S segment of the tripartite genome. Here, we show that the truncated NSs protein of clone 13 is expressed and remains in the cytoplasm, where it is degraded rapidly by the proteasome. Through the analysis of reassortants between clone 13 and a virulent strain, we localized the marker(s) of attenuation in the S segment of this attenuated virus. This result raises questions regarding the role of NSs in pathogenesis and highlights, for the first time in theBunyaviridae family, a major role of the S segment in virulence and attenuation, possibly associated with a defect in the nonstructural protein.

Protection against Rift Valley fever virus infection in mice upon administration of interferon-inducing RNA transcripts from the FMDV genome

2014 ◽  
Vol 109 ◽  
pp. 64-67 ◽  
Author(s):  
Gema Lorenzo ◽  
Miguel Rodríguez-Pulido ◽  
Elena López-Gil ◽  
Francisco Sobrino ◽  
Belén Borrego ◽  
...  
Keyword(s):  
Virus Infection ◽  
Rift Valley ◽  
Rift Valley Fever ◽  
Rift Valley Fever Virus ◽  
Fever Virus ◽  
Valley Fever ◽  
Rna Transcripts

scholarly journals The Nonstructural Protein NSs Induces a Variable Antibody Response in Domestic Ruminants Naturally Infected with Rift Valley Fever Virus

2011 ◽  
Vol 19 (1) ◽  
pp. 5-10 ◽  
Author(s):  
José-Carlos Fernandez ◽  
Agnès Billecocq ◽  
Jean Paul Durand ◽  
Catherine Cêtre-Sossah ◽  
Eric Cardinale ◽  
...  
Keyword(s):  
Antibody Response ◽  
Rift Valley ◽  
Rift Valley Fever ◽  
Nonstructural Protein ◽  
Rift Valley Fever Virus ◽  
High Rate ◽  
Antibody Detection ◽  
Enzyme Linked Immunosorbent Assay ◽  
Valley Fever ◽  
Wide Range

ABSTRACTRift Valley fever (RVF) is an emerging zoonosis in Africa which has spread to Egypt, the Arabian Peninsula, Madagascar, and Comoros. RVF virus (RVFV) (Bunyaviridaefamily,Phlebovirusgenus) causes a wide range of symptoms in humans, from benign fever to fatal hemorrhagic fever. Ruminants are severely affected by the disease, which leads to a high rate of mortality in young animals and to abortions and teratogenesis in pregnant females. Diagnostic tests include virus isolation and genome or antibody detection. During RVFV infection, the nucleoprotein encapsidating the tripartite RNA genome is expressed in large amounts and raises a robust antibody response, while the envelope glycoproteins elicit neutralizing antibodies which play a major role in protection. Much less is known about the antigenicity/immunogenicity of the nonstructural protein NSs, which is a major virulence factor. Here we have developed a competitive enzyme-linked immunosorbent assay (ELISA) enabling detection of low levels of NSs-specific antibodies in naturally infected or vaccinated ruminants. Detection of the NSs antibodies was validated by Western blotting. Altogether, our data showed that the NSs antibodies were detected in only 55% of animals naturally infected by RVFV, indicating that NSs does not induce a consistently high immune response. These results are discussed in light of differentiation between infected and vaccinated animals (DIVA) tests distinguishing naturally infected animals and those vaccinated with NSs-defective vaccines.

scholarly journals A ΩXaV motif in the Rift Valley fever virus NSs protein is essential for degrading p62, forming nuclear filaments and virulence

2015 ◽  
Vol 112 (19) ◽  
pp. 6021-6026 ◽  
Author(s):  
Normand Cyr ◽  
Cynthia de la Fuente ◽  
Lauriane Lecoq ◽  
Irene Guendel ◽  
Philippe R. Chabot ◽  
...  
Keyword(s):  
Rift Valley ◽  
Rift Valley Fever ◽  
Excision Repair ◽  
Rna Virus ◽  
Nonstructural Protein ◽  
Rift Valley Fever Virus ◽  
Hemorrhagic Fever ◽  
Fever Virus ◽  
Valley Fever ◽  
Infected Cells

Rift Valley fever virus (RVFV) is a single-stranded RNA virus capable of inducing fatal hemorrhagic fever in humans. A key component of RVFV virulence is its ability to form nuclear filaments through interactions between the viral nonstructural protein NSs and the host general transcription factor TFIIH. Here, we identify an interaction between a ΩXaV motif in NSs and the p62 subunit of TFIIH. This motif in NSs is similar to ΩXaV motifs found in nucleotide excision repair (NER) factors and transcription factors known to interact with p62. Structural and biophysical studies demonstrate that NSs binds to p62 in a similar manner as these other factors. Functional studies in RVFV-infected cells show that the ΩXaV motif is required for both nuclear filament formation and degradation of p62. Consistent with the fact that the RVFV can be distinguished from otherBunyaviridae-family viruses due to its ability to form nuclear filaments in infected cells, the motif is absent in the NSs proteins of otherBunyaviridae-family viruses. Taken together, our studies demonstrate that p62 binding to NSs through the ΩXaV motif is essential for degrading p62, forming nuclear filaments and enhancing RVFV virulence. In addition, these results show how the RVFV incorporates a simple motif into the NSs protein that enables it to functionally mimic host cell proteins that bind the p62 subunit of TFIIH.

scholarly journals Evaluation of the Efficacy, Potential for Vector Transmission, and Duration of Immunity of MP-12, an Attenuated Rift Valley Fever Virus Vaccine Candidate, in Sheep

2015 ◽  
Vol 22 (8) ◽  
pp. 930-937 ◽  
Author(s):  
Myrna M. Miller ◽  
Kristine E. Bennett ◽  
Barbara S. Drolet ◽  
Robbin Lindsay ◽  
James O. Mecham ◽  
...  
Keyword(s):  
Rift Valley ◽  
Neutralizing Antibodies ◽  
Rift Valley Fever ◽  
Nonstructural Protein ◽  
Rift Valley Fever Virus ◽  
Clinical Signs ◽  
Fever Virus ◽  
Vector Transmission ◽  
Valley Fever ◽  
Virulent Challenge

ABSTRACTRift Valley fever virus (RVFV) causes serious disease in ruminants and humans in Africa. In North America, there are susceptible ruminant hosts and competent mosquito vectors, yet there are no fully licensed animal vaccines for this arthropod-borne virus, should it be introduced. Studies in sheep and cattle have found the attenuated strain of RVFV, MP-12, to be both safe and efficacious based on early testing, and a 2-year conditional license for use in U.S. livestock has been issued. The purpose of this study was to further determine the vaccine's potential to infect mosquitoes, the duration of humoral immunity to 24 months postvaccination, and the ability to prevent disease and viremia from a virulent challenge. Vaccination experiments conducted in sheep found no evidence of a potential for vector transmission to 4 North American mosquito species. Neutralizing antibodies were elicited, with titers of >1:40 still present at 24 months postvaccination. Vaccinates were protected from clinical signs and detectable viremia after challenge with virulent virus, while control sheep had fever and high-titered viremia extending for 5 days. Antibodies to three viral proteins (nucleocapsid N, the N-terminal half of glycoprotein GN, and the nonstructural protein from the short segment NSs) were also detected to 24 months using competitive enzyme-linked immunosorbent assays. This study demonstrates that the MP-12 vaccine given as a single dose in sheep generates protective immunity to a virulent challenge with antibody duration of at least 2 years, with no evidence of a risk for vector transmission.

scholarly journals Genetic Evidence for an Interferon-Antagonistic Function of Rift Valley Fever Virus Nonstructural Protein NSs

2001 ◽  
Vol 75 (3) ◽  
pp. 1371-1377 ◽  
Author(s):  
Michèle Bouloy ◽  
Christian Janzen ◽  
Pierre Vialat ◽  
Huot Khun ◽  
Jovan Pavlovic ◽  
...  
Keyword(s):  
Rift Valley ◽  
Rift Valley Fever ◽  
Nonstructural Protein ◽  
Rift Valley Fever Virus ◽  
Fever Virus ◽  
Sub Saharan Africa ◽  
Wild Type ◽  
Valley Fever ◽  
Viral Virulence ◽  
Deficient Mice

ABSTRACT Rift Valley fever virus (RVFV), a phlebovirus of the family Bunyaviridae, is a major public health threat in Egypt and sub-Saharan Africa. The viral and host cellular factors that contribute to RVFV virulence and pathogenicity are still poorly understood. All pathogenic RVFV strains direct the synthesis of a nonstructural phosphoprotein (NSs) that is encoded by the smallest (S) segment of the tripartite genome and has an undefined accessory function. In this report, we show that MP12 and clone 13, two attenuated RVFV strains with mutations in the NSs gene, were highly virulent in IFNAR−/− mice lacking the alpha/beta interferon (IFN-α/β) receptor but remained attenuated in IFN-γ receptor-deficient mice. Both attenuated strains proved to be excellent inducers of early IFN-α/β production. In contrast, the virulent strain ZH548 failed to induce detectable amounts of IFN-α/β and replicated extensively in both IFN-competent and IFN-deficient mice. Clone 13 has a defective NSs gene with a large in-frame deletion. This defect in the NSs gene results in expression of a truncated protein which is rapidly degraded. To investigate whether the presence of the wild-type NSs gene correlated with inhibition of IFN-α/β production, we infected susceptible IFNAR−/− mice with S gene reassortant viruses. When the S segment of ZH548 was replaced by that of clone 13, the resulting reassortants became strong IFN inducers. When the defective S segment of clone 13 was exchanged with the wild-type S segment of ZH548, the reassortant virus lost the capacity to stimulate IFN-α/β production. These results demonstrate that the ability of RVFV to inhibit IFN-α/β production correlates with viral virulence and suggest that the accessory protein NSs is an IFN antagonist.

scholarly journals Rift Valley fever virus: a new avenue of research on the biological functions of amyloids?

2021 ◽  
Author(s):  
Ke Peng ◽  
Pierre-Yves Lozach
Keyword(s):  
Rift Valley ◽  
Rift Valley Fever ◽  
Biological Function ◽  
Nonstructural Protein ◽  
Rift Valley Fever Virus ◽  
Febrile Illness ◽  
Fever Virus ◽  
Biological Functions ◽  
Valley Fever ◽  
Great Rift Valley

Rift Valley fever is a mosquito-borne viral zoonosis that was first discovered in the Great Rift Valley, Kenya, in 1930. Rift Valley fever virus (RVFV) primarily infects domestic animals and humans, with clinical outcomes ranging from self-limiting febrile illness to acute hepatitis and encephalitis. The virus left Africa a few decades ago, and there is a risk of introduction into southern Europe and Asia. From this perspective, we introduce RVFV and focus on the capacity of its virulence factor, the nonstructural protein NSs, to form amyloid-like fibrils. Here, we discuss the implications for the NSs biological function, the ability of RVFV to evade innate immunity, and RVFV virulence and neurotoxicity.

scholarly journals Rift Valley fever virus minigenome system for investigating the role of L protein residues in viral transcription and replication

2019 ◽  
Author(s):  
Hanna Jérôme ◽  
Martin Rudolf ◽  
Michaela Lelke ◽  
Meike Pahlmann ◽  
Carola Busch ◽  
...  
Keyword(s):  
Rift Valley Fever ◽  
Rift Valley Fever Virus ◽  
Regulatory Elements ◽  
Viral Transcription ◽  
Valley Fever ◽  
Replication Complex ◽  
L Protein ◽  
Minigenome System ◽  
Transcription And Replication

AbstractReplicon systems are important molecular tools for investigating the function of virus proteins and regulatory elements involved in viral RNA synthesis. We developed an ambisense minigenome system for Rift Valley fever virus (RVFV) to dissect the effects of L gene mutations on viral transcription versus replication. The S RNA segment with regulatory elements for ambisense gene expression served as backbone for the minigenome. Expression of the luciferase reporter gene allowed the overall activity of the RVFV replication complex to be assessed, while northern blot analysis enabled differentiation between synthesis of viral mRNA and replication intermediates. The functionality of the system was demonstrated by probing residues predictably involved in the active site of the cap-snatching endonuclease in the N-terminus of the L protein. Corresponding mutations led to a selective defect in the viral mRNA synthesis as described for other viruses of theBunyaviralesorder. The analysis of further L gene mutants revealed an essential and specific role of a C-terminal region in the RVFV L protein in viral transcription. In summary, the established minigenome system is suitable for functional testing of the relevance of residues for viral transcription and replication. It may be used to validate hypotheses arising from structural or biochemical investigations of the RVFV replication complex.

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