scholarly journals Rift Valley Fever Virus MP-12 Vaccine Is Fully Attenuated by a Combination of Partial Attenuations in the S, M, and L Segments

2015 ◽  
Vol 89 (14) ◽  
pp. 7262-7276 ◽  
Author(s):  
Tetsuro Ikegami ◽  
Terence E. Hill ◽  
Jennifer K. Smith ◽  
Lihong Zhang ◽  
Terry L. Juelich ◽  
...  
Keyword(s):  
United States ◽  
Rift Valley ◽  
Rift Valley Fever ◽  
Rift Valley Fever Virus ◽  
The United States ◽  
Fever Virus ◽  
Pathogenic Strain ◽  
Wild Type ◽  
Valley Fever ◽  
Content Type

ABSTRACTRift Valley fever (RVF) is a mosquito-borne zoonotic disease endemic to Africa and characterized by a high rate of abortion in ruminants and hemorrhagic fever, encephalitis, or blindness in humans. RVF is caused by Rift Valley fever virus (RVFV; familyBunyaviridae, genusPhlebovirus), which has a tripartite negative-stranded RNA genome (consisting of the S, M, and L segments). Further spread of RVF into countries where the disease is not endemic may affect the economy and public health, and vaccination is an effective approach to prevent the spread of RVFV. A live-attenuated MP-12 vaccine is one of the best-characterized RVF vaccines for safety and efficacy and is currently conditionally licensed for use for veterinary purposes in the United States. Meanwhile, as of 2015, no other RVF vaccine has been conditionally or fully licensed for use in the United States. The MP-12 strain is derived from wild-type pathogenic strain ZH548, and its genome encodes 23 mutations in the three genome segments. However, the mechanism of MP-12 attenuation remains unknown. We characterized the attenuation of wild-type pathogenic strain ZH501 carrying a mutation(s) of the MP-12 S, M, or L segment in a mouse model. Our results indicated that MP-12 is attenuated by the mutations in the S, M, and L segments, while the mutations in the M and L segments confer stronger attenuation than those in the S segment. We identified a combination of 3 amino acid changes, Y259H (Gn), R1182G (Gc), and R1029K (L), that was sufficient to attenuate ZH501. However, strain MP-12 with reversion mutations at those 3 sites was still highly attenuated. Our results indicate that MP-12 attenuation is supported by a combination of multiple partial attenuation mutations and a single reversion mutation is less likely to cause a reversion to virulence of the MP-12 vaccine.IMPORTANCERift Valley fever (RVF) is a mosquito-transmitted viral disease that is endemic to Africa and that has the potential to spread into other countries. Vaccination is considered an effective way to prevent the disease, and the only available veterinary RVF vaccine in the United States is a live-attenuated MP-12 vaccine, which is conditionally licensed. Strain MP-12 is different from its parental pathogenic RVFV strain, strain ZH548, because of the presence of 23 mutations. This study determined the role of individual mutations in the attenuation of the MP-12 strain. We found that full attenuation of MP-12 occurs by a combination of multiple mutations. Our findings indicate that a single reversion mutation will less likely cause a major reversion to virulence of the MP-12 vaccine.

scholarly journals Susceptibility and barriers to infection of Colorado mosquitoes with Rift Valley fever virus

2021 ◽  
Vol 15 (10) ◽  
pp. e0009837
Author(s):  
Daniel A. Hartman ◽  
Nicholas A. Bergren ◽  
Therese Kondash ◽  
William Schlatmann ◽  
Colleen T. Webb ◽  
...  
Keyword(s):  
United States ◽  
Vertical Transmission ◽  
Rift Valley ◽  
Rift Valley Fever ◽  
Rift Valley Fever Virus ◽  
Plaque Assay ◽  
The United States ◽  
Fever Virus ◽  
Sub Saharan Africa ◽  
Valley Fever

Rift Valley fever virus (RVFV) causes morbidity and mortality in humans and domestic ungulates in sub-Saharan Africa, Egypt, and the Arabian Peninsula. Mosquito vectors transmit RVFV between vertebrates by bite, and also vertically to produce infectious progeny. Arrival of RVFV into the United States by infected mosquitoes or humans could result in significant impacts on food security, human health, and wildlife health. Elucidation of the vectors involved in the post-introduction RVFV ecology is paramount to rapid implementation of vector control. We performed vector competence experiments in which field-collected mosquitoes were orally exposed to an epidemic strain of RVFV via infectious blood meals. We targeted floodwater Aedes species known to feed on cattle, and/or deer species (Aedes melanimon Dyar, Aedes increpitus Dyar, Aedes vexans Meigen). Two permanent-water-breeding species were targeted as well: Culiseta inornata Williston of unknown competence considering United States populations, and Culex tarsalis Coquillett as a control species for which transmission efficiency is known. We tested the potential for midgut infection, midgut escape (dissemination), ovarian infection (vertical transmission), and transmission by bite (infectious saliva). Tissues were assayed by plaque assay and RT-qPCR, to quantify infectious virus and confirm virus identity. Tissue infection data were analyzed using a within-host model under a Bayesian framework to determine the probabilities of infection ‘outcomes’ (midgut-limited infection, disseminated infection, etc.) while estimating barriers to infection between tissues. Permanent-water-breeding mosquitoes (Cx. tarsalis and Cs. inornata) exhibited more efficient horizontal transmission, as well as potential for vertical transmission, which is contrary to the current assumptions of RVFV ecology. Barrier estimates trended higher for Aedes spp., suggesting systemic factors in the differences between these species and Cx. tarsalis and Cs. inornata. These data indicate higher potential for vertical transmission than previously appreciated, and support the consensus of RVFV transmission including a broad range of potential vectors.

scholarly journals NSs Virulence Factor of Rift Valley Fever Virus Engages the F-Box Proteins FBXW11 and β-TRCP1 To Degrade the Antiviral Protein Kinase PKR

2016 ◽  
Vol 90 (13) ◽  
pp. 6140-6147 ◽  
Author(s):  
Markus Kainulainen ◽  
Simone Lau ◽  
Charles E. Samuel ◽  
Veit Hornung ◽  
Friedemann Weber
Keyword(s):  
Protein Kinase ◽  
Host Cell ◽  
Rift Valley ◽  
Rift Valley Fever ◽  
Rift Valley Fever Virus ◽  
Substrate Recognition ◽  
Fever Virus ◽  
Valley Fever ◽  
Content Type ◽  
F Box Protein

ABSTRACTRift Valley fever virus (RVFV, familyBunyaviridae, genusPhlebovirus) is a relevant pathogen of both humans and livestock in Africa. The nonstructural protein NSs is a major virulence factor known to suppress the type I interferon (IFN) response by inhibiting host cell transcription and by proteasomal degradation of a major antiviral IFN effector, the translation-inhibiting protein kinase PKR. Here, we identified components of the modular SCF (Skp1, Cul1, F-box protein)-type E3 ubiquitin ligases as mediators of PKR destruction by NSs. Small interfering RNAs (siRNAs) against the conserved SCF subunit Skp1 protected PKR from NSs-mediated degradation. Consequently, RVFV replication was severely reduced in Skp1-depleted cells when PKR was present. SCF complexes have a variable F-box protein subunit that determines substrate specificity for ubiquitination. We performed an siRNA screen for all (about 70) human F-box proteins and found FBXW11 to be involved in PKR degradation. The partial stabilization of PKR by FBXW11 depletion upregulated PKR autophosphorylation and phosphorylation of the PKR substrate eIF2α and caused a shutoff of host cell protein synthesis in RVFV-infected cells. To maximally protect PKR from the action of NSs, knockdown of structurally and functionally related FBXW1 (also known as β-TRCP1), in addition to FBXW11 deletion, was necessary. Consequently, NSs was found to interact with both FBXW11 and β-TRCP1. Thus, NSs eliminates the antiviral kinase PKR by recruitment of SCF-type E3 ubiquitin ligases containing FBXW11 and β-TRCP1 as substrate recognition subunits. This antagonism of PKR by NSs is essential for efficient RVFV replication in mammalian cells.IMPORTANCERift Valley fever virus is a pathogen of humans and animals that has the potential to spread from Africa and the Arabian Peninsula to other regions. A major virulence mechanism is the proteasomal degradation of the antiviral kinase PKR by the viral protein NSs. Here, we demonstrate that NSs requires E3 ubiquitin ligase complexes of the SCF (Skp1, Cul1, F-box protein) type to destroy PKR. SCF-type complexes can engage variant ubiquitination substrate recognition subunits, and we found the F-box proteins FBXW11 and β-TRCP1 to be relevant for the action of NSs against PKR. Thus, we identified the host cell factors that are critically needed by Rift Valley fever virus to uphold its replication against the potent antiviral kinase PKR.

scholarly journals Dicer-2- and Piwi-Mediated RNA Interference in Rift Valley Fever Virus-Infected Mosquito Cells

2012 ◽  
Vol 87 (3) ◽  
pp. 1631-1648 ◽  
Author(s):  
P. Léger ◽  
E. Lara ◽  
B. Jagla ◽  
O. Sismeiro ◽  
Z. Mansuroglu ◽  
...  
Keyword(s):  
Rna Interference ◽  
Rift Valley ◽  
Rift Valley Fever ◽  
Rift Valley Fever Virus ◽  
Acute Infection ◽  
Antiviral Response ◽  
Fever Virus ◽  
Infected Mosquito ◽  
Valley Fever ◽  
Content Type

ABSTRACTRift Valley fever virus(RVFV) is aPhlebovirus(Bunyaviridaefamily) transmitted by mosquitoes. It infects humans and ruminants, causing dramatic epidemics and epizootics in Africa, Yemen, and Saudi Arabia. While recent studies demonstrated the importance of the nonstructural protein NSs as a major component of virulence in vertebrates, little is known about infection of mosquito vectors. Here we studied RVFV infection in three different mosquito cell lines, Aag2 cells fromAedes aegyptiand U4.4 and C6/36 cells fromAedes albopictus. In contrast with mammalian cells, where NSs forms nuclear filaments, U4.4 and Aag2 cells downregulated NSs expression such that NSs filaments were never formed in nuclei of U4.4 cells and disappeared at an early time postinfection in the case of Aag2 cells. On the contrary, in C6/36 cells, NSs nuclear filaments were visible during the entire time course of infection. Analysis of virus-derived small interfering RNAs (viRNAs) by deep sequencing indicated that production of viRNAs was very low in C6/36 cells, which are known to be Dicer-2 deficient but expressed some viRNAs presenting a Piwi signature. In contrast, Aag2 and U4.4 cells produced large amounts of viRNAs predominantly matching the S segment and displaying Dicer-2 and Piwi signatures. Whereas 21-nucleotide (nt) Dicer-2 viRNAs were prominent during early infection, the population of 24- to 27-nt Piwi RNAs (piRNAs) increased progressively and became predominant later during the acute infection and during persistence. In Aag2 and U4.4 cells, the combined actions of the Dicer-2 and Piwi pathways triggered an efficient antiviral response permitting, among other actions, suppression of NSs filament formation and allowing establishment of persistence. In C6/36 cells, Piwi-mediated RNA interference (RNAi) appeared to be sufficient to mount an antiviral response against a secondary infection with a superinfecting virus. This study provides new insights into the role of Dicer and Piwi in mosquito antiviral defense and the development of the antiviral response in mosquitoes.

scholarly journals T7 RNA polymerase-dependent and -independent systems for cDNA-based rescue of Rift Valley fever virus

2008 ◽  
Vol 89 (9) ◽  
pp. 2157-2166 ◽  
Author(s):  
Matthias Habjan ◽  
Nicola Penski ◽  
Martin Spiegel ◽  
Friedemann Weber
Keyword(s):  
Rna Polymerase ◽  
Rift Valley ◽  
Rift Valley Fever ◽  
Cell Clone ◽  
Rift Valley Fever Virus ◽  
Fever Virus ◽  
T7 Rna Polymerase ◽  
Wild Type ◽  
Valley Fever ◽  
Pol I

Rift Valley fever virus (RVFV) is responsible for large and recurrent outbreaks of acute febrile illness among humans and domesticated animals in Africa. It belongs to the family Bunyaviridae, genus Phlebovirus, and its negative-stranded RNA genome consists of three segments. Here, we report the establishment and characterization of two different systems to rescue the RVFV wild-type strain ZH548. The first system is based on the BHK-21 cell clone BSR-T7/5, which stably expresses T7 RNA polymerase (T7 pol). Rescue of wild-type RVFV was achieved with three T7 pol-driven cDNA plasmids representing the viral RNA segments in the antigenomic sense. The second system involves 293T cells transfected with three RNA pol I-driven plasmids for the viral segments and two RNA pol II-driven support plasmids to express the viral polymerase components L and N. It is known that the 5′ triphosphate group of T7 pol transcripts strongly activates the antiviral interferon system via the intracellular RNA receptor RIG-I. Nonetheless, both the T7 pol and the pol I/II system were of similar efficiency. This was even true for the rescue of a RVFV mutant lacking the interferon antagonist nonstructural proteins. Further experiments demonstrated that the unresponsiveness of BHK-21 and BSR-T7/5 cells to T7 pol transcripts is most probably due to a deficiency in the RIG-I pathway. Our reverse genetics systems now enable us to manipulate the genome of RVFV and study its virulence mechanisms. Moreover, the finding that BHK-derived cell lines have a compromised RIG-I pathway may explain their suitability for propagating and rescuing a wide variety of viruses.

scholarly journals Preliminary Evaluation of a Recombinant Rift Valley Fever Virus Glycoprotein Subunit Vaccine Providing Full Protection against Heterologous Virulent Challenge in Cattle

Vaccines ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 748
Author(s):  
William C. Wilson ◽  
Bonto Faburay ◽  
Jessie D. Trujillo ◽  
Izabela Ragan ◽  
Sun-Young Sunwoo ◽  
...  
Keyword(s):  
Rift Valley ◽  
Subunit Vaccine ◽  
Rift Valley Fever ◽  
Rift Valley Fever Virus ◽  
The United States ◽  
Fever Virus ◽  
Sub Saharan Africa ◽  
Preliminary Evaluation ◽  
Vaccine Platform ◽  
Valley Fever

Rift Valley fever virus (RVFV) is a mosquito-borne zoonotic pathogen that causes periodic outbreaks of abortion in ruminant species and hemorrhagic disease in humans in sub-Saharan Africa. These outbreaks have a significant impact on veterinary and public health. Its introduction to the Arabian Peninsula in 2003 raised concerns of further spread of this transboundary pathogen to non-endemic areas. These concerns are supported by the presence of competent vectors in many non-endemic countries. There is no licensed RVF vaccine available for humans and only a conditionally licensed veterinary vaccine available in the United States. Currently employed modified live attenuated virus vaccines in endemic countries lack the ability for differentiating infected from vaccinated animals (DIVA). Previously, the efficacy of a recombinant subunit vaccine based on the RVFV Gn and Gc glycoproteins, derived from the 1977 human RVFV isolate ZH548, was demonstrated in sheep. In the current study, cattle were vaccinated subcutaneously with the Gn only, or Gn and Gc combined, with either one or two doses of the vaccine and then subjected to heterologous virus challenge with the virulent Kenya-128B-15 RVFV strain, isolated from Aedes mosquitoes in 2006. The elicited immune responses by some vaccine formulations (one or two vaccinations) conferred complete protection from RVF within 35 days after the first vaccination. Vaccines given 35 days prior to RVFV challenge prevented viremia, fever and RVFV-associated histopathological lesions. This study indicates that a recombinant RVFV glycoprotein-based subunit vaccine platform is able to prevent and control RVFV infections in target animals.

scholarly journals Further Characterization of Rio Grande Virus and Potential for Cross Reactivity with Rift Valley Fever Virus Assays

Viruses ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1719
Author(s):  
Mitchell S. Szymczak ◽  
Will K. Reeves ◽  
Myrna M. Miller
Keyword(s):  
Rift Valley ◽  
Rift Valley Fever ◽  
Rift Valley Fever Virus ◽  
Rio Grande ◽  
The United States ◽  
Fever Virus ◽  
Ovis Aries ◽  
Sand Fly ◽  
Antibody Detection ◽  
Valley Fever

Phleboviruses (genus Phlebovirus, family Phenuiviridae) are emerging pathogens of humans and animals. Sand-fly-transmitted phleboviruses are found in Europe, Africa, the Middle East, and the Americas, and are responsible for febrile illness and nervous system infections in humans. Rio Grande virus (RGV) is the only reported phlebovirus in the United States. Isolated in Texas from southern plains woodrats, RGV is not known to be pathogenic to humans or domestic animals, but serologic evidence suggests that sheep (Ovis aries) and horses (Equus caballus) in this region have been infected. Rift Valley fever virus (RVFV), a phlebovirus of Africa, is an important pathogen of wild and domestic ruminants, and can also infect humans with the potential to cause severe disease. The introduction of RVFV into North America could greatly impact U.S. livestock and human health, and the development of vaccines and countermeasures is a focus of both the CDC and USDA. We investigated the potential for serologic reagents used in RVFV diagnostic assays to also detect cells infected with RGV. Western blots and immunocytochemistry assays were used to compare the antibody detection of RGV, RVFV, and two other New World phlebovirus, Punta Toro virus (South and Central America) and Anhanga virus (Brazil). Antigenic cross-reactions were found using published RVFV diagnostic reagents. These findings will help to inform test interpretation to avoid false positive RVFV diagnoses that could lead to public health concerns and economically costly agriculture regulatory responses, including quarantine and trade restrictions.

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