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1
Soi, Reuben K., Fred R. Rurangirwa, Travis C. McGuire, Paul M. Rwambo, James C. DeMartini e Timothy B. Crawford. "Protection of Sheep against Rift Valley Fever Virus and Sheep Poxvirus with a Recombinant Capripoxvirus Vaccine". Clinical and Vaccine Immunology 17, n. 12 (dicembre 2010): 1842–49. http://dx.doi.org/10.1128/cvi.00220-10.
Testo completoAbstract (sommario):
ABSTRACT Rift Valley fever (RVF) is an epizootic viral disease of sheep that can be transmitted from sheep to humans, particularly by contact with aborted fetuses. A capripoxvirus (CPV) recombinant virus (rKS1/RVFV) was developed, which expressed the Rift Valley fever virus (RVFV) Gn and Gc glycoproteins. These expressed glycoproteins had the correct size and reacted with monoclonal antibodies (MAb) to native glycoproteins. Mice vaccinated with rKS1/RVFV were protected against RVFV challenge. Sheep vaccinated with rKS1/RVFV twice developed neutralizing antibodies and were significantly protected against RVFV and sheep poxvirus challenge. These findings further document the value of CPV recombinants as ruminant vaccine vectors and support the inclusion of RVFV genes encoding glycoproteins in multivalent recombinant vaccines to be used where RVF occurs.
2
Shiell, Brian J., Siying Ye, Jennifer A. Harper, Brenda van der Heide, Gary Beddome, Adam J. Foord, Wojtek P. Michalski, John Bingham e Grantley R. Peck. "Reagents for detection of Rift Valley fever virus infection in sheep". Journal of Veterinary Diagnostic Investigation 32, n. 4 (25 maggio 2020): 577–80. http://dx.doi.org/10.1177/1040638720926476.
Testo completoAbstract (sommario):
Rift Valley fever virus (RVFV) causes Rift Valley fever (RVF), resulting in morbidity and mortality in humans and ruminants. Evidence of transboundary outbreaks means that RVFV remains a threat to human health and livestock industries in countries that are free from the disease. To enhance surveillance capability, methods for detection of RVFV are required. The generation of reagents suitable for the detection of RVFV antigen in formalin-fixed, paraffin-embedded tissues from infected animals have been developed and are described herein. Recombinant nucleoprotein (rNP) was expressed in Escherichia coli and purified using immobilized metal ion affinity chromatography. Purified rNP was used as an immunogen to produce anti-NP polyclonal antisera in rabbits for use in detection of RVFV NP in experimentally infected animals by immunohistochemistry. Antisera raised in rabbits against rNP were able to recognize viral NP antigen in fixed infected Vero cell pellets and sheep liver. Therefore, the methods and reagents described herein are useful in assays for detection of RVFV infections in animals, for research and surveillance purposes.
3
Ayari-Fakhfakh, Emna, Tânia Zaverucha do Valle, Laurent Guillemot, Jean-Jacques Panthier, Michèle Bouloy, Abdeljelil Ghram, Emmanuel Albina e Catherine Cêtre-Sossah. "MBT/Pas mouse: a relevant model for the evaluation of Rift Valley fever vaccines". Journal of General Virology 93, n. 7 (1 luglio 2012): 1456–64. http://dx.doi.org/10.1099/vir.0.042754-0.
Testo completoAbstract (sommario):
Currently, there are no worldwide licensed vaccines for Rift Valley fever (RVF) that are both safe and effective. Development and evaluation of vaccines, diagnostics and treatments depend on the availability of appropriate animal models. Animal models are also necessary to understand the basic pathobiology of infection. Here, we report the use of an inbred MBT/Pas mouse model that consistently reproduces RVF disease and serves our purpose for testing the efficacy of vaccine candidates; an attenuated Rift Valley fever virus (RVFV) and a recombinant RVFV–capripoxvirus. We show that this model is relevant for vaccine testing.
4
Bingham, John, e Petrus Jansen van Vuren. "Rift Valley fever: a review". Microbiology Australia 41, n. 1 (2020): 28. http://dx.doi.org/10.1071/ma20008.
Testo completoAbstract (sommario):
Rift Valley fever (RVF) is a mosquito-borne viral disease, principally of ruminants, that is endemic to Africa. The causative Phlebovirus, Rift Valley fever virus (RVFV), has a broad host range and, as such, also infects humans to cause primarily a self-limiting febrile illness. A small number of human cases will also develop severe complications, including haemorrhagic fever, encephalitis and visual impairment. In parts of Africa, it is a major disease of domestic ruminants, causing epidemics of abortion and mortality. It infects and can be transmitted by a broad range of mosquitos, with those of the genus Aedes and Culex thought to be the major vectors. Therefore, the virus has the potential to become established beyond Africa, including in Australia, where competent vector hosts are endemic. Vaccines for humans have not yet been developed to the commercial stage. This review examines the threat of this virus, with particular reference to Australia, and assesses gaps in our knowledge that may benefit from research focus.
5
Lancelot, Renaud, Marina Béral, Vincent Michel Rakotoharinome, Soa-Fy Andriamandimby, Jean-Michel Héraud, Caroline Coste, Andrea Apolloni et al. "Drivers of Rift Valley fever epidemics in Madagascar". Proceedings of the National Academy of Sciences 114, n. 5 (17 gennaio 2017): 938–43. http://dx.doi.org/10.1073/pnas.1607948114.
Testo completoAbstract (sommario):
Rift Valley fever (RVF) is a vector-borne viral disease widespread in Africa. The primary cycle involves mosquitoes and wild and domestic ruminant hosts. Humans are usually contaminated after contact with infected ruminants. As many environmental, agricultural, epidemiological, and anthropogenic factors are implicated in RVF spread, the multidisciplinary One Health approach was needed to identify the drivers of RVF epidemics in Madagascar. We examined the environmental patterns associated with these epidemics, comparing human and ruminant serological data with environmental and cattle-trade data. In contrast to East Africa, environmental drivers did not trigger the epidemics: They only modulated local Rift Valley fever virus (RVFV) transmission in ruminants. Instead, RVFV was introduced through ruminant trade and subsequent movement of cattle between trade hubs caused its long-distance spread within the country. Contact with cattle brought in from infected districts was associated with higher infection risk in slaughterhouse workers. The finding that anthropogenic rather than environmental factors are the main drivers of RVF infection in humans can be used to design better prevention and early detection in the case of RVF resurgence in the region.
6
Kwaśnik, Małgorzata, Wojciech Rożek e Jerzy Rola. "Rift Valley fever – a growing threat to humans and animals". Journal of Veterinary Research 65, n. 1 (26 gennaio 2021): 7–14. http://dx.doi.org/10.2478/jvetres-2021-0009.
Testo completoAbstract (sommario):
Abstract Rift Valley fever (RVF) is a zoonotic, vector-borne infectious disease of ruminants and camels transmitted mainly by the Aedes and Culex mosquito species. Contact with the blood or organs of infected animals may infect humans. Its etiological factor is the Rift Valley fever virus (RVFV) of the Phlebovirus genus and Bunyaviridae family. Sheep and goats are most susceptible to infection and newborns and young individuals endure the most severe disease course. High abortion rates and infant mortality are typical for RVF; its clinical signs are high fever, lymphadenitis, nasal and ocular secretions and vomiting. Conventional diagnosis is done by the detection of specific IgM or IgG antibodies and RVFV nucleic acids and by virus isolation. Inactivated and live-attenuated vaccines obtained from virulent RVFV isolates are available for livestock. RVF is endemic in sub-Saharan Africa and the Arabian Peninsula, but in the last two decades, it was also reported in other African regions. Seropositive animals were detected in Turkey, Tunisia and Libya. The wide distribution of competent vectors in non-endemic areas coupled with global climate change threaten to spread RVF transboundarily. The EFSA considers the movement of infected animals and vectors to be other plausible pathways of RVF introduction into Europe. A very low risk both of introduction of the virus through an infected animal or vector and of establishment of the virus, and a moderate risk of its transmission through these means was estimated for Poland. The risk of these specific modes of disease introduction into Europe is rated as very low, but surveillance and response capabilities and cooperation with the proximal endemic regions are recommended.
7
Yang, Ze Xiao, Bo Wang, Qiu Mei Xu, Xue Ping Yao, Ling Zhu, Zhi Wen Xu, Kai Yu Wang, Gui Li Li, Shan Zhen Peng e Yin Wang. "Design and Evaluation of the Primers for Rift Valley Fever (RVF) Virus RT-PCR Detection". Advanced Materials Research 989-994 (luglio 2014): 1115–19. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.1115.
Testo completoAbstract (sommario):
Rift Valley Fever (RVF) is a notifiable multiple species diseases in the OIE list, and causes human and agricultural losses in endemic regions. To develop the rapid method for detecting of RVF, 2 specific primers for reverse transcriptase polymerase chain reaction (RT-PCR) and 7 overlapping oligo primers were designed according to the nucleotide sequence information of RVFV published in GenBank, and a DNA fragment about 318 bp of the segment S was synthesized in vitro by overlap extension PCR to construct the recombinant plasmid pMD19-T-RVFVS. Then, the 2 specific primers were evaluated via a serial of tests, including reaction temperature optimization test, sensitivity and specificity tests. The results showed that the 2 designed primers are suitable for RVFV RT-PCR detection which is a rapid method with good specificity and sensitivity, the detection limit was approximately 85 copies of the cloned viral genomic fragments (pMD19-T-RVFVS) as well as resulted in no cross-reaction for peste des petits ruminants virus (PPRV), Epidemic encephalitis B virus, E.coli , Salmonella and Pasteurella multocida etc common pathogens isolated from ruminants detection.
8
Cosseddu, Gian Mario, Kudakwashe Magwedere, Umberto Molini, Chiara Pinoni, Sigfried Khaiseb, Massimo Scacchia, Maurilia Marcacci et al. "Genetic Diversity of Rift Valley Fever Strains Circulating in Namibia in 2010 and 2011". Viruses 12, n. 12 (16 dicembre 2020): 1453. http://dx.doi.org/10.3390/v12121453.
Testo completoAbstract (sommario):
Outbreaks of Rift Valley fever (RVF) occurred in Namibia in 2010 and 2011. Complete genome characterization was obtained from virus isolates collected during disease outbreaks in southern Namibia in 2010 and from wildlife in Etosha National Park in 2011, close to the area where RVF outbreaks occurred in domestic livestock. The virus strains were sequenced using Sanger sequencing (Namibia_2010) or next generation sequencing (Namibia_2011). A sequence-independent, single-primer amplification (SISPA) protocol was used in combination with the Illumina Next 500 sequencer. Phylogenetic analysis of the sequences of the small (S), medium (M), and large (L) genome segments of RVF virus (RVFV) provided evidence that two distinct RVFV strains circulated in the country. The strain collected in Namibia in 2010 is genetically similar to RVFV strains circulating in South Africa in 2009 and 2010, confirming that the outbreaks reported in the southern part of Namibia in 2010 were caused by possible dissemination of the infection from South Africa. Isolates collected in 2011 were close to RVFV isolates from 2010 collected in humans in Sudan and which belong to the large lineage containing RVFV strains that caused an outbreak in 2006–2008 in eastern Africa. This investigation showed that the RVFV strains circulating in Namibia in 2010 and 2011 were from two different introductions and that RVFV has the ability to move across regions. This supports the need for risk-based surveillance and monitoring.
9
Terasaki, Kaori, e Shinji Makino. "Interplay between the Virus and Host in Rift Valley Fever Pathogenesis". Journal of Innate Immunity 7, n. 5 (2015): 450–58. http://dx.doi.org/10.1159/000373924.
Testo completoAbstract (sommario):
Rift Valley fever virus (RVFV) belongs to the genus Phlebovirus, family Bunyaviridae, and carries single-stranded tripartite RNA segments. The virus is transmitted by mosquitoes and has caused large outbreaks among ruminants and humans in sub-Saharan African and Middle East countries. The disease is characterized by a sudden onset of fever, headache, muscle pain, joint pain, photophobia, and weakness. In most cases, patients recover from the disease after a period of weeks, but some also develop retinal or macular changes, which result in vision impairment that lasts for an undefined period of time, and severe disease, characterized by hemorrhagic fever or encephalitis. The virus also causes febrile illness resulting in a high rate of spontaneous abortions in ruminants. The handling of wild-type RVFV requires high-containment facilities, including biosafety level 4 or enhanced biosafety level 3 laboratories. Nonetheless, studies clarifying the mechanisms of the RVFV-induced diseases and preventing them are areas of active research throughout the world. By primarily referring to recent studies using several animal model systems, protein expression systems, and specific mutant viruses, this review describes the current knowledge about the mechanisms of pathogenesis of RVF and biological functions of various viral proteins that affect RVFV pathogenicity.
10
HEISE, M. T., A. WHITMORE, J. THOMPSON, M. PARSONS, A. A. GROBBELAAR, A. KEMP, J. T. PAWESKA et al. "An alphavirus replicon-derived candidate vaccine against Rift Valley fever virus". Epidemiology and Infection 137, n. 9 (27 gennaio 2009): 1309–18. http://dx.doi.org/10.1017/s0950268808001696.
Testo completoAbstract (sommario):
SUMMARYRift Valley fever virus (RVFV) is a mosquito-transmitted bunyavirus (genusPhlebovirus) associated with severe disease in livestock and fatal encephalitis or haemorrhagic fever in a proportion of infected humans. Although live attenuated and inactivated vaccines have been used in livestock, and on a limited scale in humans, there is a need for improved anti-RVFV vaccines. Towards this goal, Sindbis virus replicon vectors expressing the RVFV Gn and Gc glycoproteins, as well as the non-structural nsM protein, were constructed and evaluated for their ability to induce protective immune responses against RVFV. These replicon vectors were shown to produce the RVFV glycoproteins to high levelsin vitroand to induce systemic anti-RVFV antibody responses in immunized mice, as determined by RVFV-specific ELISA, fluorescent antibody tests, and demonstration of a neutralizing antibody response. Replicon vaccination also provided 100% protection against lethal RVFV challenge by either the intraperitoneal or intranasal route. Furthermore, preliminary results indicate that the replicon vectors elicit RVFV-specific neutralizing antibody responses in vaccinated sheep. These results suggest that alphavirus-based replicon vectors can induce protective immunity against RVFV, and that this approach merits further investigation into its potential utility as a RVFV vaccine.
11
Zhang, Hao, Feng, Jin, Yan, Chi, Wang et al. "Genetically Modified Rabies Virus Vector-Based Rift Valley Fever Virus Vaccine is Safe and Induces Efficacious Immune Responses in Mice". Viruses 11, n. 10 (8 ottobre 2019): 919. http://dx.doi.org/10.3390/v11100919.
Testo completoAbstract (sommario):
Rift Valley fever virus (RVFV), which causes Rift Valley fever (RVF), is a mosquito-borne zoonotic pathogen that causes serious morbidity and mortality in livestock and humans. RVF is a World Health Organization (WHO) priority disease and, together with rabies, is a major health burden in Africa. Here, we present the development and characterization of an inactivated recombinant RVFV and rabies virus (RABV) vaccine candidate (rSRV9-eGn). Immunization with rSRV9-eGn stimulated the production of RVFV-specific IgG antibodies and induced humoral and cellular immunity in mice but did not induce the production of neutralizing antibodies. IgG1 and IgG2a were the main isotypes observed by IgG subtype detection, and IgG3 antibodies were not detected. The ratios of IgG1/IgG2a > 1 indicated a Type 2 humoral immune response. An effective vaccine is intended to establish a long-lived population of memory T cells, and mice generated memory cells among the proliferating T cell population after immunization with rSRV9-eGn, with effector memory T cells (TEM) as the major population. Due to the lack of prophylactic treatment experiments, it is impossible to predict whether this vaccine can protect animals from RVFV infection with only high titres of anti-RVFV IgG antibodies and no neutralizing antibodies induced, and thus, protection confirmation needs further verification. However, this RVFV vaccine designed with RABV as the vector provides ideas for the development of vaccines that prevent RVFV and RABV infections.
12
Moreno, Sandra, Eva Calvo-Pinilla, Stephanie Devignot, Friedemann Weber, Javier Ortego e Alejandro Brun. "Recombinant Rift Valley fever viruses encoding bluetongue virus (BTV) antigens: Immunity and efficacy studies upon a BTV-4 challenge". PLOS Neglected Tropical Diseases 14, n. 12 (4 dicembre 2020): e0008942. http://dx.doi.org/10.1371/journal.pntd.0008942.
Testo completoAbstract (sommario):
Background Many ruminant diseases of viral aetiology can be effectively prevented using appropriate vaccination measures. For diseases such as Rift Valley fever (RVF) the long inter-epizootic periods make routine vaccination programs unfeasible. Coupling RVF prophylaxis with seasonal vaccination programmes by means of multivalent vaccine platforms would help to reduce the risk of new RVF outbreaks. Methodology/Principal findings In this work we generated recombinant attenuated Rift Valley fever viruses (RVFVs) encoding in place of the virulence factor NSs either the VP2 capsid protein or a truncated form of the non-structural NS1 protein of bluetongue virus serotype 4 (BTV-4). The recombinant viruses were able to carry and express the heterologous BTV genes upon consecutive passages in cell cultures. In murine models, a single immunization was sufficient to protect mice upon RVFV challenge and to elicit a specific immune response against BTV-4 antigens that was fully protective after a BTV-4 boost. In sheep, a natural host for RVFV and BTV, both vaccines proved immunogenic although conferred only partial protection after a virulent BTV-4 reassortant Morocco strain challenge. Conclusions/Significance Though additional optimization will be needed to improve the efficacy data against BTV in sheep, our findings warrant further developments of attenuated RVFV as a dual vaccine platform carrying heterologous immune relevant antigens for ruminant diseases in RVF risk areas.
13
Petrova, Velislava, Paul Kristiansen, Gunnstein Norheim e Solomon A. Yimer. "Rift valley fever: diagnostic challenges and investment needs for vaccine development". BMJ Global Health 5, n. 8 (agosto 2020): e002694. http://dx.doi.org/10.1136/bmjgh-2020-002694.
Testo completoAbstract (sommario):
Rift valley fever virus (RVFV) is a causative agent of a viral zoonosis that constitutes a major clinical burden in wild and domestic ruminants. The virus causes major outbreaks in livestock (sheep, goats, cattle and camels) and can be transmitted to humans by contaminated animal products or via arthropod vectors. Human-to-human transmission has not been reported to date, but spill-over events from animals have led to outbreaks in humans in Africa and the Arabian Peninsula. Currently, there is no licensed human vaccine against RVFV and the virus is listed as a priority pathogen by the World Health Organisation (WHO) due to the high epidemic potential and the lack of effective countermeasures. Multiple large RVFV outbreaks have been reported since the virus was discovered. During the last two decades, over 4000 cases and ~1000 deaths have been reported. The lack of systematic surveillance to estimate the true burden and incidence of human RVF disease is a challenge for planning future vaccine efficacy evaluation. This creates a need for robust diagnostic methodologies that can be deployed in remote regions to aid case confirmation, assessment of seroprevalence as well as pathogen surveillance required for the different stages of vaccine evaluation. Here, we perform comprehensive landscaping of the available diagnostic solutions for detection of RVFV in humans. Based on the identified gaps in the currently available in-house and commercially available methods, we highlight the specific investment needs for diagnostics that are critical for accelerating the development of effective vaccines against RVFV.
14
Wichgers Schreur, Paul J., Nadia Oreshkova, Frank Harders, Alex Bossers, Rob J. M. Moormann e Jeroen Kortekaas. "Paramyxovirus-based production of Rift Valley fever virus replicon particles". Journal of General Virology 95, n. 12 (1 dicembre 2014): 2638–48. http://dx.doi.org/10.1099/vir.0.067660-0.
Testo completoAbstract (sommario):
Replicon-particle-based vaccines combine the efficacy of live-attenuated vaccines with the safety of inactivated or subunit vaccines. Recently, we developed Rift Valley fever virus (RVFV) replicon particles, also known as nonspreading RVFV (NSR), and demonstrated that a single vaccination with these particles can confer sterile immunity in target animals. NSR particles can be produced by transfection of replicon cells, which stably maintain replicating RVFV S and L genome segments, with an expression plasmid encoding the RVFV glycoproteins, Gn and Gc, normally encoded by the M-genome segment. Here, we explored the possibility to produce NSR with the use of a helper virus. We show that replicon cells infected with a Newcastle disease virus expressing Gn and Gc (NDV-GnGc) were able to produce high levels of NSR particles. In addition, using reverse genetics and site-directed mutagenesis, we were able to create an NDV-GnGc variant that lacks the NDV fusion protein and contains two amino acid substitutions in, respectively, Gn and HN. The resulting virus uses a unique entry pathway that facilitates the efficient production of NSR in a one-component system. The novel system provides a promising alternative for transfection-based NSR production.
15
Hao, Meng, Guanying Zhang, Shengnan Zhang, Zhengshan Chen, Xiangyang Chi, Yunzhu Dong, Pengfei Fan et al. "Characterization of Two Neutralizing Antibodies against Rift Valley Fever Virus Gn Protein". Viruses 12, n. 3 (27 febbraio 2020): 259. http://dx.doi.org/10.3390/v12030259.
Testo completoAbstract (sommario):
The Rift Valley fever virus (RVFV) is an arthropod-borne virus that can not only cause severe disease in domestic animals but also in humans. However, the licensed vaccines or available therapeutics for humans do not exist. Here, we report two Gn-specific neutralizing antibodies (NAbs), isolated from a rhesus monkey immunized with recombinant human adenoviruses type 4 expressing Rift Valley fever virus Gn and Gc protein (rHAdV4-GnGcopt). The two NAbs were both able to protect host cells from RVFV infection. The interactions between NAbs and Gn were then characterized to demonstrate that these two NAbs might preclude RVFV glycoprotein rearrangement, hindering the exposure of fusion loops in Gc to endosomal membranes after the virus invades the host cell. The target region for the two NAbs is located in the Gn domain III, implying that Gn is a desired target for developing vaccines and neutralizing antibodies against RVFV.
16
EVANS, A., F. GAKUYA, J. T. PAWESKA, M. ROSTAL, L. AKOOLO, P. J. VAN VUREN, T. MANYIBE et al. "Prevalence of antibodies against Rift Valley fever virus in Kenyan wildlife". Epidemiology and Infection 136, n. 9 (8 novembre 2007): 1261–69. http://dx.doi.org/10.1017/s0950268807009806.
Testo completoAbstract (sommario):
SUMMARYRift Valley fever virus (RVFV) is an arbovirus associated with periodic outbreaks, mostly on the African continent, of febrile disease accompanied by abortion in livestock, and a severe, fatal haemorrhagic syndrome in humans. However, the maintenance of the virus during the inter-epidemic period (IEP) when there is low or no disease activity detected in livestock or humans has not been determined. This study report prevalence of RVFV-neutralizing antibodies in sera (n=896) collected from 16 Kenyan wildlife species including at least 35% that were born during the 1999–2006 IEP. Specimens from seven species had detectable neutralizing antibodies against RVFV, including African buffalo, black rhino, lesser kudu, impala, African elephant, kongoni, and waterbuck. High RVFV antibody prevalence (>15%) was observed in black rhinos and ruminants (kudu, impala, buffalo, and waterbuck) with the highest titres (up to 1:1280) observed mostly in buffalo, including animals born during the IEP. All lions, giraffes, plains zebras, and warthogs tested were either negative or less than two animals in each species had low (⩽1:16) titres of RVFV antibodies. Of 249 sera collected from five wildlife species during the 2006–2007 outbreak, 16 out of 19 (84%) of the ruminant (gerenuk, waterbuck, and eland) specimens had RVFV-neutralizing titres ⩾1:80. These data provide evidence that wild ruminants are infected by RVFV but further studies are required to determine whether these animals play a role in the virus maintenance between outbreaks and virus amplification prior to a noticeable outbreak.
17
Niu, Tianchan, Holly D. Gaff, Yiannis E. Papelis e David M. Hartley. "An Epidemiological Model of Rift Valley Fever with Spatial Dynamics". Computational and Mathematical Methods in Medicine 2012 (2012): 1–12. http://dx.doi.org/10.1155/2012/138757.
Testo completoAbstract (sommario):
As a category A agent in the Center for Disease Control bioterrorism list, Rift Valley fever (RVF) is considered a major threat to the United States (USA). Should the pathogen be intentionally or unintentionally introduced to the continental USA, there is tremendous potential for economic damages due to loss of livestock, trade restrictions, and subsequent food supply chain disruptions. We have incorporated the effects of space into a mathematical model of RVF in order to study the dynamics of the pathogen spread as affected by the movement of humans, livestock, and mosquitoes. The model accounts for the horizontal transmission of Rift Valley fever virus (RVFV) between two mosquito and one livestock species, and mother-to-offspring transmission of virus in one of the mosquito species. Space effects are introduced by dividing geographic space into smaller patches and considering the patch-to-patch movement of species. For each patch, a system of ordinary differential equations models fractions of populations susceptible to, incubating, infectious with, or immune to RVFV. The main contribution of this work is a methodology for analyzing the likelihood of pathogen establishment should an introduction occur into an area devoid of RVF. Examples are provided for general and specific cases to illustrate the methodology.
18
Odendaal, Lieza, Sarah J. Clift, Geoffrey T. Fosgate e A. Sally Davis. "Lesions and Cellular Tropism of Natural Rift Valley Fever Virus Infection in Adult Sheep". Veterinary Pathology 56, n. 1 (21 ottobre 2018): 61–77. http://dx.doi.org/10.1177/0300985818806049.
Testo completoAbstract (sommario):
Rift Valley fever (RVF) is a mosquito-borne disease that affects both ruminants and humans, with epidemics occurring more frequently in recent years in Africa and the Middle East, probably as a result of climate change and intensified livestock trade. Sheep necropsied during the 2010 RVF outbreak in South Africa were examined by histopathology and immunohistochemistry (IHC). A total of 124 sheep were available for study, of which 99 cases were positive for RVF. Multifocal-random, necrotizing hepatitis was confirmed as the most distinctive lesion of RVF cases in adult sheep. Of cases where liver, spleen, and kidney tissues were available, 45 of 70 had foci of acute renal tubular epithelial injury in addition to necrosis in both the liver and spleen. In some cases, acute renal injury was the most significant RVF lesion. Immunolabeling for RVFV was most consistent and unequivocal in liver, followed by spleen, kidney, lung, and skin. RVFV antigen-positive cells included hepatocytes, adrenocortical epithelial cells, renal tubular epithelial cells, macrophages, neutrophils, epidermal keratinocytes, microvascular endothelial cells, and vascular smooth muscle. The minimum set of specimens to be submitted for histopathology and IHC to confirm or exclude a diagnosis of RVFV are liver, spleen, and kidney. Skin from areas with visible crusts and lung could be useful additional samples. In endemic areas, cases of acute renal tubular injury should be investigated further if other more common causes of renal lesions have already been excluded. RVFV can also cause an acute infection in the testis, which requires further investigation.
19
Lubisi, Baratang, Phumudzo Ndouvhada, Donald Neiffer, Mary-Louise Penrith, Donald-Ray Sibanda e Armanda Bastos. "Evaluation of a Virus Neutralisation Test for Detection of Rift Valley Fever Antibodies in Suid Sera". Tropical Medicine and Infectious Disease 4, n. 1 (25 marzo 2019): 52. http://dx.doi.org/10.3390/tropicalmed4010052.
Testo completoAbstract (sommario):
Rift Valley fever (RVF) is a vector-borne viral disease of ruminants mainly, and man, characterized by abortions and neonatal deaths in animals and flu-like to more severe symptoms that can result in death in humans. The disease is endemic in Africa, Saudi Arabia and Yemen, and outbreaks occur following proliferation of RVF virus (RVFV) infected mosquito vectors. Vertebrate animal maintenance hosts of RVFV, which serve as a source of virus during inter-epidemic periods remain unknown, with wild and domestic suids being largely overlooked. To address this, we evaluated the virus neutralization test (VNT) for RVF antibody detection in suid sera, as a first step in assessing the role of suids in the epidemiology of RVF in Africa. Testing of experimental and field sera from domestic pigs and warthogs with a commercial RVF competitive antibody ELISA, served as a reference standard against which the VNT results were compared. Results indicate that VNT can detect anti-RVFV antibodies within three days post-infection, has an analytical specificity of 100% and diagnostic sensitivity and specificity of 80% and 97%, respectively. Although labour-intensive and time-consuming, the VNT proved suitable for screening suid sera and plasma for presence of RVFV antibodies in viraemic and recovered animals.
20
Odendaal, Lieza, A. Sally Davis, Geoffrey T. Fosgate e Sarah J. Clift. "Lesions and Cellular Tropism of Natural Rift Valley Fever Virus Infection in Young Lambs". Veterinary Pathology 57, n. 1 (17 dicembre 2019): 66–81. http://dx.doi.org/10.1177/0300985819882633.
Testo completoAbstract (sommario):
A clear distinction can be made regarding the susceptibility to and the severity of lesions in young lambs when compared to adult sheep. In particular, there are important differences in the lesions and tropism of Rift Valley fever virus (RVFV) in the liver, kidneys, and lymphoid tissues of young lambs. A total of 84 lambs (<6 weeks old), necropsied during the 2010 to 2011 Rift Valley fever (RVF) outbreak in South Africa, were examined by histopathology and immunohistochemistry (IHC). Of the 84 lambs, 71 were positive for RVFV. The most striking diagnostic feature in infected lambs was diffuse necrotizing hepatitis with multifocal liquefactive hepatic necrosis (primary foci) against a background of diffuse hepatocellular death. Lymphocytolysis was present in all lymphoid organs except for the thymus. Lesions in the kidney rarely progressed beyond hydropic change and occasional pyknosis or karyolysis in renal tubular epithelial cells. Viral antigen was diffusely present in the cytoplasm of hepatocytes, but this labeling was noticeably sparse in primary foci. Immunolabeling for RVFV in young lambs was also detected in macrophages, vascular smooth muscle cells, adrenocortical epithelial cells, renal tubular epithelial cells, renal perimacular cells, and cardiomyocytes. RVFV immunolabeling was also often present in capillaries and small blood vessels either as non-cell-associated viral antigen, as antigen in endothelial cells, or intravascular cellular debris. Specimens from the liver, spleen, kidney, and lungs were adequate to confirm a diagnosis of RVF. Characteristic lesions were present in these organs with the liver and spleen being the most consistently positive for RVFV by IHC.
21
Ritter, Marcus, Michèle Bouloy, Pierre Vialat, Christian Janzen, Otto Haller e Michael Frese. "Resistance to Rift Valley fever virus in Rattus norvegicus: genetic variability within certain ‘inbred’ strains". Journal of General Virology 81, n. 11 (1 novembre 2000): 2683–88. http://dx.doi.org/10.1099/0022-1317-81-11-2683.
Testo completoAbstract (sommario):
Rift Valley fever virus (RVFV) is the causative agent of Rift Valley fever, a widespread disease of domestic animals and humans in sub-Saharan Africa. Laboratory rats have frequently been used as an animal model for studying the pathogenesis of Rift Valley fever. It is shown here that Lewis rats (LEW/mol) are susceptible to infection with RVFV, whereas Wistar–Furth (WF/mol) rats are resistant to RVFV infection. LEW/mol rats developed acute hepatitis and died after infection with RVFV strain ZH548, whereas WF/mol rats survived the infection. Cross-breeding of resistant WF/mol rats with susceptible LEW/mol rats demonstrated that resistance is segregated as a single dominant gene. Primary hepatocytes but not glial cells from WF/mol rats showed the resistant phenotype in cell culture, indicating that resistance was cell type-specific. Moreover, when cultured hepatocytes were stimulated with interferon (IFN) type I there was no indication of a regulatory role of IFN in the RVFV-resistance gene expression in WF/mol rats. Interestingly, previous reports have shown that LEW rats from a different breeding stock (LEW/mai) are resistant to RVFV infections, whereas WF/mai rats are susceptible. Thus, inbred rat strains seem to differ in virus susceptibility depending on their breeding histories. A better genetic characterization of inbred rat strains and a revision in nomenclature is needed to improve animal experimentation in the future.
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Freiberg, Alexander N., Michael B. Sherman, Marc C. Morais, Michael R. Holbrook e Stanley J. Watowich. "Three-Dimensional Organization of Rift Valley Fever Virus Revealed by Cryoelectron Tomography". Journal of Virology 82, n. 21 (20 agosto 2008): 10341–48. http://dx.doi.org/10.1128/jvi.01191-08.
Testo completoAbstract (sommario):
ABSTRACT Rift Valley fever virus (RVFV) is a member of the Bunyaviridae virus family (genus Phlebovirus) and is considered to be one of the most important pathogens in Africa, causing viral zoonoses in livestock and humans. Here, we report the characterization of the three-dimensional structural organization of RVFV vaccine strain MP-12 by cryoelectron tomography. Vitrified-hydrated virions were found to be spherical, with an average diameter of 100 nm. The virus glycoproteins formed cylindrical hollow spikes that clustered into distinct capsomeres. In contrast to previous assertions that RVFV is pleomorphic, the structure of RVFV MP-12 was found to be highly ordered. The three-dimensional map was resolved to a resolution of 6.1 nm, and capsomeres were observed to be arranged on the virus surface in an icosahedral lattice with clear T=12 quasisymmetry. All icosahedral symmetry axes were visible in self-rotation functions calculated using the Fourier transform of the RVFV MP-12 tomogram. To the best of our knowledge, a triangulation number of 12 had previously been reported only for Uukuniemi virus, a bunyavirus also within the Phlebovirus genus. The results presented in this study demonstrate that RVFV MP-12 possesses T=12 icosahedral symmetry and suggest that other members of the Phlebovirus genus, as well as of the Bunyaviridae family, may adopt icosahedral symmetry. Knowledge of the virus architecture may provide a structural template to develop vaccines and diagnostics, since no effective anti-RVFV treatments are available for human use.
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Nelson, Corey R., Tyler Mrozowich, Sean M. Park, Simmone D’souza, Amy Henrickson, Justin R. J. Vigar, Hans-Joachim Wieden, Raymond J. Owens, Borries Demeler e Trushar R. Patel. "Human DDX17 Unwinds Rift Valley Fever Virus Non-Coding RNAs". International Journal of Molecular Sciences 22, n. 1 (23 dicembre 2020): 54. http://dx.doi.org/10.3390/ijms22010054.
Testo completoAbstract (sommario):
Rift Valley fever virus (RVFV) is a mosquito-transmitted virus from the Bunyaviridae family that causes high rates of mortality and morbidity in humans and ruminant animals. Previous studies indicated that DEAD-box helicase 17 (DDX17) restricts RVFV replication by recognizing two primary non-coding RNAs in the S-segment of the genome: the intergenic region (IGR) and 5′ non-coding region (NCR). However, we lack molecular insights into the direct binding of DDX17 with RVFV non-coding RNAs and information on the unwinding of both non-coding RNAs by DDX17. Therefore, we performed an extensive biophysical analysis of the DDX17 helicase domain (DDX17135–555) and RVFV non-coding RNAs, IGR and 5’ NCR. The homogeneity studies using analytical ultracentrifugation indicated that DDX17135–555, IGR, and 5’ NCR are pure. Next, we performed small-angle X-ray scattering (SAXS) experiments, which suggested that DDX17 and both RNAs are homogenous as well. SAXS analysis also demonstrated that DDX17 is globular to an extent, whereas the RNAs adopt an extended conformation in solution. Subsequently, microscale thermophoresis (MST) experiments were performed to investigate the direct binding of DDX17 to the non-coding RNAs. The MST experiments demonstrated that DDX17 binds with the IGR and 5’ NCR with a dissociation constant of 5.77 ± 0.15 µM and 9.85 ± 0.11 µM, respectively. As DDX17135–555 is an RNA helicase, we next determined if it could unwind IGR and NCR. We developed a helicase assay using MST and fluorescently-labeled oligos, which suggested DDX17135–555 can unwind both RNAs. Overall, our study provides direct evidence of DDX17135–555 interacting with and unwinding RVFV non-coding regions.
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Anthony, Tasneem, Antoinette van Schalkwyk, Marco Romito, Lieza Odendaal, Sarah J. Clift e A. Sally Davis. "Vaccination with Rift Valley fever virus live attenuated vaccine strain Smithburn caused meningoencephalitis in alpacas". Journal of Veterinary Diagnostic Investigation 33, n. 4 (27 maggio 2021): 777–81. http://dx.doi.org/10.1177/10406387211015294.
Testo completoAbstract (sommario):
Rift Valley fever (RVF) is a zoonotic, viral, mosquito-borne disease that causes considerable morbidity and mortality in humans and livestock in Africa and the Arabian Peninsula. In June 2018, 4 alpaca inoculated subcutaneously with live attenuated RVF virus (RVFV) Smithburn strain exhibited pyrexia, aberrant vocalization, anorexia, neurologic signs, and respiratory distress. One animal died the evening of inoculation, and 2 at ~20 d post-inoculation. Concern regarding potential vaccine strain reversion to wild-type RVFV or vaccine-induced disease prompted autopsy of the latter two. Macroscopically, both alpacas had severe pulmonary edema and congestion, myocardial hemorrhages, and cyanotic mucous membranes. Histologically, they had cerebral nonsuppurative encephalomyelitis with perivascular cuffing, multifocal neuronal necrosis, gliosis, and meningitis. Lesions were more severe in the 4-mo-old cria. RVFV antigen and RNA were present in neuronal cytoplasm, by immunohistochemistry and in situ hybridization (ISH) respectively, and cerebrum was also RVFV positive by RT-rtPCR. The virus clustered in lineage K (100% sequence identity), with close association to Smithburn sequences published previously (identity: 99.1–100%). There was neither evidence of an aberrant immune-mediated reaction nor reassortment with wild-type virus. The evidence points to a pure infection with Smithburn vaccine strain as the cause of the animals’ disease.
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Bron, Gebbiena M., Kathryn Strimbu, Hélène Cecilia, Anita Lerch, Sean M. Moore, Quan Tran, T. Alex Perkins e Quirine A. ten Bosch. "Over 100 Years of Rift Valley Fever: A Patchwork of Data on Pathogen Spread and Spillover". Pathogens 10, n. 6 (5 giugno 2021): 708. http://dx.doi.org/10.3390/pathogens10060708.
Testo completoAbstract (sommario):
During the past 100 years, Rift Valley fever virus (RVFV), a mosquito-borne virus, has caused potentially lethal disease in livestock, and has been associated with significant economic losses and trade bans. Spillover to humans occurs and can be fatal. Here, we combined data on RVF disease in humans (22 countries) and animals (37 countries) from 1931 to 2020 with seroprevalence studies from 1950 to 2020 (n = 228) from publicly available databases and publications to draw a more complete picture of the past and current RVFV epidemiology. RVFV has spread from its original locus in Kenya throughout Africa and into the Arabian Peninsula. Throughout the study period seroprevalence increased in both humans and animals, suggesting potentially increased RVFV exposure. In 24 countries, animals or humans tested positive for RVFV antibodies even though outbreaks had never been reported there, suggesting RVFV transmission may well go unnoticed. Among ruminants, sheep were the most likely to be exposed during RVF outbreaks, but not during periods of cryptic spread. We discuss critical data gaps and highlight the need for detailed study descriptions, and long-term studies using a one health approach to further convert the patchwork of data to the tale of RFV epidemiology.
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Doyle, Joshua D., Dominique J. Barbeau, Haley N. Cartwright e Anita K. McElroy. "#41: Mechanistic Immune Correlates of Protection Following Vaccination Against Rift Valley Fever Virus". Journal of the Pediatric Infectious Diseases Society 10, Supplement_2 (1 giugno 2021): S14. http://dx.doi.org/10.1093/jpids/piab031.030.
Testo completoAbstract (sommario):
Abstract Background Rift Valley fever virus (RVFV) is a zoonotic arbovirus endemic to large areas of Africa and the Arabian peninsula that causes a significant annual burden of disease in ruminant animals, and is associated with periodic outbreaks in human populations. RVFV causes a wide spectrum of disease in infected patients ranging from a self-limiting febrile illness to hepatitis, encephalitis, hemorrhagic fever, and death. Despite the significant economic and public health impact of RVFV, there are no currently available vaccines or therapeutics available for RVFV. Methods Previous work has established that vaccination with an attenuated strain of RVFV, RVFV-ΔNSs, confers protection against subsequent lethal challenge in a murine model of infection. To characterize mechanistic immune correlates of protection, we vaccinated C57BL/6 mice with RVFV-ΔNSs then depleted vaccinated mice of various memory lymphocyte subsets, including CD4+, CD8+, CD4+/CD8+ T-cells before challenging mice with a lethal dose of WT RVFV. To assess for the role of antibodies in providing protection, we depleted mice of their B cells prior to vaccination with RVFV-ΔNSs, confirmed the lack of RVFV specific antibodies, and then challenged them with lethal WT RVFV. To determine the minimal immunologic factors required for protection, we vaccinated a series of donor mice, transferred either immunoglobulins or splenocytes to naïve recipient mice, then challenged them with WT RVFV. Results Vaccination with RVFV-ΔNSs protected mice from subsequent challenge, and this protection was not abrogated by depletion of CD4+, CD8+, or combined CD4+ and CD8+ lymphocytes, suggesting that RVFV-specific T-cells are dispensable for protection in the presence of virus specific antibodies. Vaccinated mice depleted of CD20+ B-cells were also protected against WT challenge, suggesting that B-cells/antibodies are also dispensable for protection in the presence of an intact T-cell response. Passive transfer of antibodies from vaccinated mice to recipient mice protected them against subsequent WT challenge, demonstrating that antibodies are sufficient for protection. Adoptive transfer of total splenocytes protected mice against subsequent WT challenge, indicating that lymphocytes are also sufficient to mediate protection. Conclusions In this study we defined the mechanistic immune correlates of protection following vaccination with attenuated RVFV-ΔNSs against WT RVFV in a murine model. Here, we have shown that both humoral and cellular immunity are sufficient to mediate protection in recipient animals, and can compensate for each other when one is missing. These results further our understanding of the protective immunologic response to infection by RVFV, and will help inform further vaccine development efforts against this important emerging pathogen.
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Grossi-Soyster, Elysse N., e A. Desiree LaBeaud. "Rift Valley Fever: Important Considerations for Risk Mitigation and Future Outbreaks". Tropical Medicine and Infectious Disease 5, n. 2 (2 giugno 2020): 89. http://dx.doi.org/10.3390/tropicalmed5020089.
Testo completoAbstract (sommario):
Rift Valley fever virus (RVFV) is a zoonotic phlebovirus of the Phenuiviridae family with great opportunity for emergence in previously unaffected regions, despite its current geographical limits. Outbreaks of RVFV often infect humans or domesticated animals, such as livestock, concurrently and occur sporadically, ranging from localized outbreaks in villages to multi-country events that spread rapidly. The true burden of Rift Valley fever (RVF) is not well defined due to underreporting, misdiagnosis caused by the broad spectrum of disease presentation, and minimal access for rapid and accurate laboratory confirmation. Severe symptoms may include hemorrhagic fever, loss of vision, psychological impairment or disturbances, and organ failure. Those living in endemic areas and travelers should be aware of the potential for exposure to ongoing outbreaks or interepidemic transmission, and engage in behaviors to minimize exposure risks, as vaccinations in humans are currently unavailable and animal vaccinations are not used routinely or ubiquitously. The lack of vaccines approved for use in humans is concerning, as RVFV has proven to be highly pathogenic in naïve populations, causing severe disease in a large percent of confirmed cases, which could have considerable impact on human health.
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Hickerson, Brady, Jonna Westover, Arnaud Van Wettere, Johanna Rigas, Jinxin Miao, Bettina Conrad, Neil Motter, Zhongde Wang e Brian Gowen. "Pathogenesis of Rift Valley Fever Virus Aerosol Infection in STAT2 Knockout Hamsters". Viruses 10, n. 11 (19 novembre 2018): 651. http://dx.doi.org/10.3390/v10110651.
Testo completoAbstract (sommario):
Rift Valley fever virus (RVFV) is an emerging pathogen capable of causing severe disease in livestock and humans and can be transmitted by multiple routes including aerosol exposure. Several animal models have been developed to gain insight into the pathogenesis associated with aerosolized RVFV infection, but work with these models is restricted to high containment biosafety level (BSL) laboratories limiting their use for antiviral and vaccine development studies. Here, we report on a new RVFV inhalation infection model in STAT2 KO hamsters exposed to aerosolized MP-12 vaccine virus by nose-only inhalation that enables a more accurate delivery and measurement of exposure dose. RVFV was detected in hepatic and other tissues 4–5 days after challenge, consistent with virus-induced lesions in the liver, spleen and lung. Furthermore, assessment of blood chemistry and hematological parameters revealed alterations in several liver disease markers and white blood cell parameters. Our results indicate that STAT2 KO hamsters develop a disease course that shares features of disease observed in human cases and in other animal models of RVFV aerosol exposure, supporting the use of this BSL-2 infection model for countermeasure development efforts.
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Georges, Tshilenge M., Masumu Justin, Mbao Victor, Kayembe Jean Marie, Rweyemamu Mark e Mulumba Mfumu K. Léopold. "Seroprevalence and Virus Activity of Rift Valley Fever in Cattle in Eastern Region of Democratic Republic of the Congo". Journal of Veterinary Medicine 2018 (28 giugno 2018): 1–8. http://dx.doi.org/10.1155/2018/4956378.
Testo completoAbstract (sommario):
Rift Valley fever (RVF) is a zoonotic disease that is characterized by periodic and severe outbreaks in humans and animals. Published information on the occurrence of RVF in domestic animals is very scarce in the Democratic Republic of the Congo (DRC). To assess possible circulation of Rift Valley fever virus (RVFV) in cattle in the eastern province of DRC, 450 sera collected from cattle in North Kivu, South Kivu, and Ituri provinces were analyzed using the enzyme-linked immunosorbent assay (ELISA), for the detection of viral Immunoglobulin (Ig) G and M, and reverse transcriptase polymerase chain reaction (RT-PCR), for detection of viral RVF RNA. A cumulative anti-RVF IgG prevalence of 6.22% (95% CI 4.25–8.97) was recorded from the three provinces sampled. In North Kivu and Ituri provinces the anti-RVF IgG prevalence was 12.67% [95% CI 7.80–19.07] and 6% [95% CI 2.78–11.08], respectively, while all the sera collected from South Kivu province were negative for anti-RVF IgG antibodies. Anti-RVF IgM prevalence of 1.8% was obtained among sampled animals in the three provinces. None of the positive anti-RVF IgM samples (n=8) was positive for viral RVFV RNA using RT-PCR. Our findings suggest that RVFV is widely distributed among cattle in eastern province of DRC particularly in North Kivu and Ituri provinces although the epidemiological factors supporting this virus circulation remain unknown in these areas.
30
RISSMANN, M., M. EIDEN, B. O. EL MAMY, K. ISSELMOU, B. DOUMBIA, U. ZIEGLER, T. HOMEIER-BACHMANN, B. YAHYA e M. H. GROSCHUP. "Serological and genomic evidence of Rift Valley fever virus during inter-epidemic periods in Mauritania". Epidemiology and Infection 145, n. 5 (28 dicembre 2016): 1058–68. http://dx.doi.org/10.1017/s0950268816003022.
Testo completoAbstract (sommario):
SUMMARYRift Valley fever virus (RVFV) is an emerging pathogen of major concern throughout Africa and the Arabian Peninsula, affecting both livestock and humans. In the past recurrent epidemics were reported in Mauritania and studies focused on the analysis of samples from affected populations during acute outbreaks. To verify characteristics and presence of RVFV during non-epidemic periods we implemented a multi-stage serological and molecular analysis. Serum samples of small ruminants, cattle and camels were obtained from Mauritania during an inter-epidemic period in 2012–2013. This paper presents a comparative analysis of potential variations and shifts of antibody presence and the capability of inter-epidemic infections in Mauritanian livestock. We observed distinct serological differences between tested species (seroprevalence: small ruminants 3·8%, cattle 15·4%, camels 32·0%). In one single bovine from Nouakchott, a recent RVF infection could be identified by the simultaneous detection of IgM antibodies and viral RNA. This study indicates the occurrence of a low-level enzootic RVFV circulation in livestock in Mauritania. Moreover, results indicate that small ruminants can preferably act as sentinels for RVF surveillance.
31
Sall, A. A., P. M. de A. Zanotto, O. K. Sene, H. G. Zeller, J. P. Digoutte, Y. Thiongane e M. Bouloy. "Genetic Reassortment of Rift Valley Fever Virus in Nature". Journal of Virology 73, n. 10 (1 ottobre 1999): 8196–200. http://dx.doi.org/10.1128/jvi.73.10.8196-8200.1999.
Testo completoAbstract (sommario):
ABSTRACT Rift Valley fever virus (RVFV), a phlebovirus of theBunyaviridae family, is an arthropod-borne virus which emerges periodically throughout Africa, emphasizing that it poses a major threat for animal and human populations. To assess the genetic variability of RVFV, several isolates from diverse localities of Africa were investigated by means of reverse transcription-PCR followed by direct sequencing of a region of the small (S), medium (M), and large (L) genomic segments. Phylogenetic analysis showed the existence of three major lineages corresponding to geographic variants from West Africa, Egypt, and Central-East Africa. However, incongruences detected between the L, M, and S phylogenies suggested that genetic exchange via reassortment occurred between strains from different lineages. This hypothesis, depicted by parallel phylogenies, was further confirmed by statistical tests. Our findings, which strongly suggest exchanges between strains from areas of endemicity in West and East Africa, strengthen the potential existence of a sylvatic cycle in the tropical rain forest. This also emphasizes the risk of generating uncontrolled chimeric viruses by using live attenuated vaccines in areas of endemicity.
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Rissmann, Melanie, Nils Kley, Reiner Ulrich, Franziska Stoek, Anne Balkema-Buschmann, Martin Eiden e Martin H. Groschup. "Competency of Amphibians and Reptiles and Their Potential Role as Reservoir Hosts for Rift Valley Fever Virus". Viruses 12, n. 11 (23 ottobre 2020): 1206. http://dx.doi.org/10.3390/v12111206.
Testo completoAbstract (sommario):
Rift Valley fever phlebovirus (RVFV) is an arthropod-borne zoonotic pathogen, which is endemic in Africa, causing large epidemics, characterized by severe diseases in ruminants but also in humans. As in vitro and field investigations proposed amphibians and reptiles to potentially play a role in the enzootic amplification of the virus, we experimentally infected African common toads and common agamas with two RVFV strains. Lymph or sera, as well as oral, cutaneous and anal swabs were collected from the challenged animals to investigate seroconversion, viremia and virus shedding. Furthermore, groups of animals were euthanized 3, 10 and 21 days post-infection (dpi) to examine viral loads in different tissues during the infection. Our data show for the first time that toads are refractory to RVFV infection, showing neither seroconversion, viremia, shedding nor tissue manifestation. In contrast, all agamas challenged with the RVFV strain ZH501 carried virus genomes in the spleens at 3 dpi, but the animals displayed neither viremia nor virus shedding. In conclusion, the results of this study indicate that amphibians are not susceptible and reptiles are only susceptible to a low extent to RVFV, indicating that both species play, if at all, rather a subordinate role in the RVF virus ecology.
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Won, Sungyong, Tetsuro Ikegami, C. J. Peters e Shinji Makino. "NSm Protein of Rift Valley Fever Virus Suppresses Virus-Induced Apoptosis". Journal of Virology 81, n. 24 (3 ottobre 2007): 13335–45. http://dx.doi.org/10.1128/jvi.01238-07.
Testo completoAbstract (sommario):
ABSTRACT Rift Valley fever virus (RVFV) is a member of the genus Phlebovirus within the family Bunyaviridae. It can cause severe epidemics among ruminants and fever, myalgia, a hemorrhagic syndrome, and/or encephalitis in humans. The RVFV M segment encodes the NSm and 78-kDa proteins and two major envelope proteins, Gn and Gc. The biological functions of the NSm and 78-kDa proteins are unknown; both proteins are dispensable for viral replication in cell cultures. To determine the biological functions of the NSm and 78-kDa proteins, we generated the mutant virus arMP-12-del21/384, carrying a large deletion in the pre-Gn region of the M segment. Neither NSm nor the 78-kDa protein was synthesized in arMP-12-del21/384-infected cells. Although arMP-12-del21/384 and its parental virus, arMP-12, showed similar growth kinetics and viral RNA and protein accumulation in infected cells, arMP-12-del21/384-infected cells induced extensive cell death and produced larger plaques than did arMP-12-infected cells. arMP-12-del21/384 replication triggered apoptosis, including the cleavage of caspase-3, the cleavage of its downstream substrate, poly(ADP-ribose) polymerase, and activation of the initiator caspases, caspase-8 and -9, earlier in infection than arMP-12. NSm expression in arMP-12-del21/384-infected cells suppressed the severity of caspase-3 activation. Further, NSm protein expression inhibited the staurosporine-induced activation of caspase-8 and -9, demonstrating that other viral proteins were dispensable for NSm's function in inhibiting apoptosis. RVFV NSm protein is the first identified Phlebovirus protein that has an antiapoptotic function.
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Riblett, Amber M., Vincent A. Blomen, Lucas T. Jae, Louis A. Altamura, Robert W. Doms, Thijn R. Brummelkamp e Jason A. Wojcechowskyj. "A Haploid Genetic Screen Identifies Heparan Sulfate Proteoglycans Supporting Rift Valley Fever Virus Infection". Journal of Virology 90, n. 3 (18 novembre 2015): 1414–23. http://dx.doi.org/10.1128/jvi.02055-15.
Testo completoAbstract (sommario):
ABSTRACTRift Valley fever virus (RVFV) causes recurrent insect-borne epizootics throughout the African continent, and infection of humans can lead to a lethal hemorrhagic fever syndrome. Deep mutagenesis of haploid human cells was used to identify host factors required for RVFV infection. This screen identified a suite of enzymes involved in glycosaminoglycan (GAG) biogenesis and transport, including several components of thecis-oligomeric Golgi (COG) complex, one of the central components of Golgi complex trafficking. In addition, disruption ofPTAR1led to RVFV resistance as well as reduced heparan sulfate surface levels, consistent with recent observations that PTAR1-deficient cells exhibit altered Golgi complex morphology and glycosylation defects. A variety of biochemical and genetic approaches were utilized to show that both pathogenic and attenuated RVFV strains require GAGs for efficient infection on some, but not all, cell types, with the block to infection being at the level of virion attachment. Examination of other members of theBunyaviridaefamily for GAG-dependent infection suggested that the interaction with GAGs is not universal among bunyaviruses, indicating that these viruses, as well as RVFV on certain cell types, employ additional unidentified virion attachment factors and/or receptors.IMPORTANCERift Valley fever virus (RVFV) is an emerging pathogen that can cause severe disease in humans and animals. Epizootics among livestock populations lead to high mortality rates and can be economically devastating. Human epidemics of Rift Valley fever, often initiated by contact with infected animals, are characterized by a febrile disease that sometimes leads to encephalitis or hemorrhagic fever. The global burden of the pathogen is increasing because it has recently disseminated beyond Africa, which is of particular concern because the virus can be transmitted by widely distributed mosquito species. There are no FDA-licensed vaccines or antiviral agents with activity against RVFV, and details of its life cycle and interaction with host cells are not well characterized. We used the power of genetic screening in human cells and found that RVFV utilizes glycosaminoglycans to attach to host cells. This furthers our understanding of the virus and informs the development of antiviral therapeutics.
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Grossi-Soyster, Elysse N., e A. Desiree LaBeaud. "Rift Valley fever virus: future emergence and the impact on One Health". Biochemist 39, n. 3 (1 giugno 2017): 22–25. http://dx.doi.org/10.1042/bio03903022.
Testo completoAbstract (sommario):
Rift Valley fever virus (RVFV) is a mosquito-borne Bunyavirus that currently affects livestock and humans, causing a wide spectrum of symptoms. RVFV was confined to the African continent for many decades and spread to the Arabian Peninsula in recent history. The potential for widespread emergence into new regions and populations is possible and likely, as many outbreaks are driven by human behaviour and livestock trade. While many imported human cases have been detected, establishment of the virus in new geographic areas will depend on amplification in dense animal populations. Western and European countries have identified a substantial risk for the emergence of RVFV, as agricultural industries constitute a large percentage of the global economy.
36
Zouaghi, Khaoula, Ali Bouattour, Hajer Aounallah, Rebecca Surtees, Eva Krause, Janine Michel, Aymen Mamlouk, Andreas Nitsche e Youmna M’ghirbi. "First Serological Evidence of Crimean-Congo Hemorrhagic Fever Virus and Rift Valley Fever Virus in Ruminants in Tunisia". Pathogens 10, n. 6 (18 giugno 2021): 769. http://dx.doi.org/10.3390/pathogens10060769.
Testo completoAbstract (sommario):
Crimean-Congo hemorrhagic fever virus (CCHFV, Nairoviridae family) and Rift Valley fever virus (RVFV, Phenuiviridae family) are zoonotic vector-borne pathogens with clinical relevance worldwide. Our study aimed to determine seroprevalences of these viruses and potential risk factors among livestock (cattle, sheep, and goats) in Tunisia. Sera were tested for antibodies against CCHFV (n = 879) and RVFV (n = 699) using various enzyme-linked immunosorbent assays (ELISAs) and indirect immunofluorescence assays (IIFA). The overall seroprevalence of IgG antibodies was 8.6% (76/879) and 2.3% (16/699) against CCHFV and RVFV, respectively. For CCHF seropositivity bioclimatic zones and breed were potential risk factors for the three tested animal species; while the season was associated with cattle and sheep seropositivity, tick infestation was associated with cattle and goats seropositivity and age as a risk factor was only associated with cattle seropositivity. Age and season were significantly associated with RVFV seropositivity in sheep. Our results confirm the circulation of CCHFV and RVFV in Tunisia and identified the principal risk factors in ruminants. This knowledge could help to mitigate the risk of ruminant infections and subsequently also human infections.
37
McMillen, Cynthia M., Nitin Arora, Devin A. Boyles, Joseph R. Albe, Michael R. Kujawa, Jeffrey F. Bonadio, Carolyn B. Coyne e Amy L. Hartman. "Rift Valley fever virus induces fetal demise in Sprague-Dawley rats through direct placental infection". Science Advances 4, n. 12 (dicembre 2018): eaau9812. http://dx.doi.org/10.1126/sciadv.aau9812.
Testo completoAbstract (sommario):
Rift Valley fever virus (RVFV) infections in pregnant livestock cause high rates of fetal demise; miscarriage in pregnant women has also been associated with RVFV infection. To address how RVFV infection during pregnancy causes detrimental effects on the fetus, we developed a pregnant rodent model of RVFV infection. We found that pregnant rats were more susceptible to RVFV-induced death than their nonpregnant counterparts and that RVFV infection resulted in intrauterine fetal death and severe congenital abnormalities, even in pups from infected asymptomatic pregnant rats. Virus distribution in infected dams was widespread, with a previously unrecognized preference for infection, replication, and tissue damage in the placenta. In human mid-gestation placental tissue, RVFV directly infected placental chorionic villi, with replication detected in the outermost syncytial layer. Our work identifies direct placental infection by RVFV as a mechanism for vertical transmission. This is the first study to show vertical transmission of RVFV with a lethal outcome in a species other than livestock. This study highlights the potential impact of a future epidemic of this emerging mosquito-borne virus.
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Anderson, G. W., T. W. Slone e C. J. Peters. "Pathogenesis of Rift Valley fever virus (RVFV) in inbred rats". Microbial Pathogenesis 2, n. 4 (aprile 1987): 283–93. http://dx.doi.org/10.1016/0882-4010(87)90126-4.
Testo completo
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Rissmann, Melanie, Matthias Lenk, Franziska Stoek, Claudia A. Szentiks, Martin Eiden e Martin H. Groschup. "Replication of Rift Valley Fever Virus in Amphibian and Reptile-Derived Cell Lines". Pathogens 10, n. 6 (31 maggio 2021): 681. http://dx.doi.org/10.3390/pathogens10060681.
Testo completoAbstract (sommario):
Rift Valley fever phlebovirus (RVFV) is a zoonotic arthropod-borne virus, which has led to devastating epidemics in African countries and on the Arabian Peninsula. Results of in-vivo, in-vitro and field studies suggested that amphibians and reptiles may play a role as reservoir hosts of RVFV, promoting its maintenance during inter-epidemic periods. To elucidate this hypothesis, we examined two newly established reptile-derived cell lines (Egyptian cobra and Chinese pond turtle) and five previously generated reptile- and amphibian-derived cell lines for their replicative capacity for three low- and high-pathogenic RVFV strains. At different time points after infection, viral loads (TCID50), genome loads and the presence of intracellular viral antigen (immunofluorescence) were assessed. Additionally, the influence of temperatures on the replication was examined. Except for one cell line (read-eared slider), all seven cell lines were infected by all three RVFV strains. Two different terrapin-derived cell lines (Common box turtle, Chinese pond turtle) were highly susceptible. A temperature-dependent replication of RVFV was detected for both amphibian and reptile cells. In conclusion, the results of this study indicate the general permissiveness of amphibian and reptile cell lines to RVFV and propose a potential involvement of terrapins in the virus ecology.
40
Bergren, Nicholas A., Erin M. Borland, Daniel A. Hartman e Rebekah C. Kading. "Laboratory demonstration of the vertical transmission of Rift Valley fever virus by Culex tarsalis mosquitoes". PLOS Neglected Tropical Diseases 15, n. 3 (22 marzo 2021): e0009273. http://dx.doi.org/10.1371/journal.pntd.0009273.
Testo completoAbstract (sommario):
Rift Valley fever virus (RVFV) is a mosquito-transmitted virus with proven ability to emerge into naïve geographic areas. Limited field evidence suggests that RVFV is transmitted vertically from parent mosquito to offspring, but until now this mechanism has not been confirmed in the laboratory. Furthermore, this transmission mechanism has allowed for the prediction of RVFV epizootics based on rainfall patterns collected from satellite information. However, in spite of the relevance to the initiation of epizootic events, laboratory confirmation of vertical transmission has remained an elusive research aim for thirty-five years. Herein we present preliminary evidence of the vertical transmission of RVFV by Culex tarsalis mosquitoes after oral exposure to RVFV. Progeny from three successive gonotrophic cycles were reared to adults, with infectious RVFV confirmed in each developmental stage. Virus was detected in ovarian tissues of parental mosquitoes 7 days after imbibing an infectious bloodmeal. Infection was confirmed in progeny as early as the first gonotrophic cycle, with infection rates ranging from 2.0–10.0%. Virus titers among progeny were low, which may indicate a host mechanism suppressing replication.
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Wilson, William C., Bonto Faburay, Jessie D. Trujillo, Izabela Ragan, Sun-Young Sunwoo, Igor Morozov, Vinay Shivanna et al. "Preliminary Evaluation of a Recombinant Rift Valley Fever Virus Glycoprotein Subunit Vaccine Providing Full Protection against Heterologous Virulent Challenge in Cattle". Vaccines 9, n. 7 (6 luglio 2021): 748. http://dx.doi.org/10.3390/vaccines9070748.
Testo completoAbstract (sommario):
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.
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Ikegami, Tetsuro, Sungyong Won, C. J. Peters e Shinji Makino. "Characterization of Rift Valley Fever Virus Transcriptional Terminations". Journal of Virology 81, n. 16 (30 maggio 2007): 8421–38. http://dx.doi.org/10.1128/jvi.02641-06.
Testo completoAbstract (sommario):
ABSTRACT Rift Valley fever virus (RVFV) (genus Phlebovirus, family Bunyaviridae) has a tripartite negative-strand genome and causes a mosquito-borne disease among humans and livestock in sub-Saharan African and Arabian Peninsula countries. Phlebovirus L, M, and N mRNAs are synthesized from the virus-sense RNA segments, while NSs mRNA is transcribed from the anti-virus-sense S segment. The present study determined the 3′ termini of all RVFV mRNAs. The 3′ termini of N and NSs mRNAs were mapped within the S-segment intergenic region and were complementary to each other by 30 to 60 nucleotides. The termini of M and L mRNAs were mapped within 122 to 107 nucleotides and 16 to 41 nucleotides, respectively, from the 5′ ends of their templates. Viral RNA elements that control phlebovirus transcriptional terminations are largely unknown. Our studies suggested the importance of a pentanucleotide sequence, CGUCG, for N, NSs, and M mRNA transcription terminations. Homopolymeric tracts of C sequences, which were located upstream of the pentanucleotide sequence, promoted N and M mRNA terminations. Likewise, the homopolymeric tracts of G sequences that are found upstream of the pentanucleotide sequence promoted NSs mRNA termination. The L-segment 5′-untranslated region (L-5′ UTR) had neither the pentanucleotide sequence nor homopolymeric sequences, yet replacement of the S-segment intergenic region with the L-5′ UTR exerted N mRNA termination in an infectious virus. The L-5′ UTR contained two 13-nucleotide-long complete complementary sequences, and their sequence complementarities were important for L mRNA termination. A computer-mediated RNA secondary structure analysis further suggested that RNA secondary structures formed by the sections of the two 13-nucleotide-long sequences and by the sequence between them may have a role in L mRNA termination. Our data demonstrated that viral RNA elements that govern L mRNA termination differed from those that regulate mRNA terminations in the M and S segments.
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Odendaal, Lieza, A. Sally Davis e Estelle H. Venter. "Insights into the Pathogenesis of Viral Haemorrhagic Fever Based on Virus Tropism and Tissue Lesions of Natural Rift Valley Fever". Viruses 13, n. 4 (20 aprile 2021): 709. http://dx.doi.org/10.3390/v13040709.
Testo completoAbstract (sommario):
Rift Valley fever phlebovirus (RVFV) infects humans and a wide range of ungulates and historically has caused devastating epidemics in Africa and the Arabian Peninsula. Lesions of naturally infected cases of Rift Valley fever (RVF) have only been described in detail in sheep with a few reports concerning cattle and humans. The most frequently observed lesion in both ruminants and humans is randomly distributed necrosis, particularly in the liver. Lesions supportive of vascular endothelial injury are also present and include mild hydropericardium, hydrothorax and ascites; marked pulmonary congestion and oedema; lymph node congestion and oedema; and haemorrhages in many tissues. Although a complete understanding of RVF pathogenesis is still lacking, antigen-presenting cells in the skin are likely the early targets of the virus. Following suppression of type I IFN production and necrosis of dermal cells, RVFV spreads systemically, resulting in infection and necrosis of other cells in a variety of organs. Failure of both the innate and adaptive immune responses to control infection is exacerbated by apoptosis of lymphocytes. An excessive pro-inflammatory cytokine and chemokine response leads to microcirculatory dysfunction. Additionally, impairment of the coagulation system results in widespread haemorrhages. Fatal outcomes result from multiorgan failure, oedema in many organs (including the lungs and brain), hypotension, and circulatory shock. Here, we summarize current understanding of RVF cellular tropism as informed by lesions caused by natural infections. We specifically examine how extant knowledge informs current understanding regarding pathogenesis of the haemorrhagic fever form of RVF, identifying opportunities for future research.
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Khafagy, Heba A., Heba MG Abdel Aziz, Amal AM, Barghooth WM e Nermeen G. Shafik. "Correlation Between Rift Valley Fever Virus (RVFV) Neutralizing Antibody Titers in Vaccinated Sheep and Effective Dose 50 (ED50) in Vaccinated Mice". INDIAN JOURNAL OF VETERINARY SCIENCES AND BIOTECHNOLOGY 15, n. 03 (9 marzo 2020): 01–04. http://dx.doi.org/10.21887/ijvsbt.15.3.1.
Testo completoAbstract (sommario):
Rift valley fever is an arthropod-born, multispecies zoonotic viral disease. Control of RVF disease depends mainly on vector control and vaccination of susceptible animals. The present work aims to detect the correlation between Rift Valley Fever Virus (RVFV) neutralizing antibody titers in vaccinated sheep using Serum Neutralization test as in vitro test and effective dose fifty in vaccinated mice as in vivo potency test and determine if they can be alternative to each other. In this work,17 inactivated RVFV vaccine batches were evaluated, applying SNT for serum samples of vaccinated sheep and ED50 in vaccinated mice. The two models of tests showed compatible results, where the same 14 vaccine batches showed satisfactory results [(SNT >1.5) and (ED50 less than 0.02)], while the other three batches revealed unsatisfactory results in both two tests. Statistical analysis of results using Wilcoxon’s test was (0.0001), indicating a significant correlation between the tests so it could be recommended to depend on SNT instead of mice inoculation in the evaluation of RVF vaccine to reduce the numbers of animals being used and to avoid the possible public health hazard.
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Indran, Sabarish V., Olga A. Lihoradova, Inaia Phoenix, Nandadeva Lokugamage, Birte Kalveram, Jennifer A. Head, Bersabeh Tigabu et al. "Rift Valley fever virus MP-12 vaccine encoding Toscana virus NSs retains neuroinvasiveness in mice". Journal of General Virology 94, n. 7 (1 luglio 2013): 1441–50. http://dx.doi.org/10.1099/vir.0.051250-0.
Testo completoAbstract (sommario):
Rift Valley fever is a mosquito-borne zoonotic disease endemic to sub-Saharan Africa. Rift Valley fever virus (RVFV; genus Phlebovirus, family Bunyaviridae) causes high rates of abortion and fetal malformation in pregnant ruminants, and haemorrhagic fever, neurological disorders or blindness in humans. The MP-12 strain is a highly efficacious and safe live-attenuated vaccine candidate for both humans and ruminants. However, MP-12 lacks a marker to differentiate infected from vaccinated animals. In this study, we originally aimed to characterize the efficacy of a recombinant RVFV MP-12 strain encoding Toscana virus (TOSV) NSs gene in place of MP-12 NSs (rMP12-TOSNSs). TOSV NSs promotes the degradation of dsRNA-dependent protein kinase (PKR) and inhibits interferon-β gene up-regulation without suppressing host general transcription. Unexpectedly, rMP12-TOSNSs increased death in vaccinated outbred mice and inbred BALB/c or C57BL/6 mice. Immunohistochemistry showed diffusely positive viral antigens in the thalamus, hypothalamus and brainstem, including the medulla. No viral antigens were detected in spleen or liver, which is similar to the antigen distribution of moribund mice infected with MP-12. These results suggest that rMP12-TOSNSs retains neuroinvasiveness in mice. Our findings demonstrate that rMP12-TOSNSs causes neuroinvasion without any hepatic disease and will be useful for studying the neuroinvasion mechanism of RVFV and TOSV.
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Accardi, Luisa, Christophe Prehaud, Paola Di Bonito, Stefania Mochi, Michèle Bouloy e Colomba Giorgi. "Activity of Toscana and Rift Valley fever virus transcription complexes on heterologous templates". Journal of General Virology 82, n. 4 (1 aprile 2001): 781–85. http://dx.doi.org/10.1099/0022-1317-82-4-781.
Testo completoAbstract (sommario):
A transcription system for Toscana virus (TOSV) (a member of the family Bunyaviridae, genus Phlebovirus) was constructed. For in vivo expression, the TOSV transcription system uses the viral N and L proteins and an S-like RNA genome containing the chloramphenicol acetyltransferase reporter gene in the antisense orientation flanked by the viral genomic 5′- and 3′-terminal S sequences. It was found that the N and L proteins represent the minimal protein requirement for an active transcription complex. To investigate the possibility of reassortment between TOSV and Rift Valley fever virus (RVFV), the activity of their polymerase complexes was tested on their heterologous S-like RNA genomes and this showed that both virus complexes were active. Moreover, hybrid transcriptase complexes with protein components originating from the two viruses were tested on both virus templates and only the combination RVFV L + TOSV N on RVFV S-like RNA was found to be active in this assay. These results suggest that virus reassortants might be generated whenever the two viruses infect the same host.
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Rostal, Melinda K., Sarah Cleaveland, Claudia Cordel, Lara van Staden, Louise Matthews, Assaf Anyamba, William B. Karesh, Janusz T. Paweska, Daniel T. Haydon e Noam Ross. "Farm-Level Risk Factors of Increased Abortion and Mortality in Domestic Ruminants during the 2010 Rift Valley Fever Outbreak in Central South Africa". Pathogens 9, n. 11 (4 novembre 2020): 914. http://dx.doi.org/10.3390/pathogens9110914.
Testo completoAbstract (sommario):
(1) Background: Rift Valley fever (RVF) outbreaks in domestic ruminants have severe socio-economic impacts. Climate-based continental predictions providing early warnings to regions at risk for RVF outbreaks are not of a high enough resolution for ruminant owners to assess their individual risk. (2) Methods: We analyzed risk factors for RVF occurrence and severity at the farm level using the number of domestic ruminant deaths and abortions reported by farmers in central South Africa during the 2010 RVF outbreaks using a Bayesian multinomial hurdle framework. (3) Results: We found strong support that the proportion of days with precipitation, the number of water sources, and the proportion of goats in the herd were positively associated with increased severity of RVF (the numbers of deaths and abortions). We did not find an association between any risk factors and whether RVF was reported on farms. (4) Conclusions: At the farm level we identified risk factors of RVF severity; however, there was little support for risk factors of RVF occurrence. The identification of farm-level risk factors for Rift Valley fever virus (RVFV) occurrence would support and potentially improve current prediction methods and would provide animal owners with critical information needed in order to assess their herd’s risk of RVFV infection.
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Birungi, Doreen, Freda Loy Aceng, Lilian Bulage, Innocent Herbert Nkonwa, Bernadette Basuta Mirembe, Claire Biribawa, Denis Okethwangu et al. "Sporadic Rift Valley Fever Outbreaks in Humans and Animals in Uganda, October 2017–January 2018". Journal of Environmental and Public Health 2021 (20 settembre 2021): 1–8. http://dx.doi.org/10.1155/2021/8881191.
Testo completoAbstract (sommario):
Introduction. Rift Valley fever (RVF) is a mosquito-borne viral zoonosis. The Uganda Ministry of Health received alerts of suspected viral haemorrhagic fever in humans from Kiruhura, Buikwe, Kiboga, and Mityana districts. Laboratory results from Uganda Virus Research Institute indicated that human cases were positive for Rift Valley fever virus (RVFV) by polymerase chain reaction. We investigated to determine the scope of outbreaks, identify exposure factors, and recommend evidence-based control and prevention measures. Methods. A suspected case was defined as a person with acute fever onset, negative malaria test result, and at least two of the following symptoms: headache, muscle or joint pain, bleeding, and any gastroenteritis symptom (nausea, vomiting, abdominal pain, diarrhoea) in a resident of Kiruhura, Buikwe, Mityana, and Kiboga districts from 1st October 2017 to 30th January 2018. A confirmed case was defined as a suspected case with laboratory confirmation by either detection of RVF nucleic acid by reverse-transcriptase polymerase chain reaction (RT-PCR) or demonstration of serum IgM or IgG antibodies by ELISA. Community case finding was conducted in all affected districts. In-depth interviews were conducted with human cases that were infected with RVF who included herdsmen and slaughterers/meat handlers to identify exposure factors for RVF infection. A total of 24 human and 362 animal blood samples were tested. Animal blood samples were purposively collected from farms that had reported stormy abortions in livestock and unexplained death of animals after a short illness (107 cattle, 83 goats, and 43 sheep). Convenient sampling for the wildlife (10 zebras, 1 topi, and 1 impala) was conducted to investigate infection in animals from Kiruhura, Buikwe, Mityana, and Kiboga districts. Human blood was tested for anti-RVFV IgM and IgG and animal blood for anti-RVFV IgG. Environmental assessments were conducted during the outbreaks in all the affected districts. Results. Sporadic RVF outbreaks occurred from mid-October 2017 to mid-January 2018 affecting humans, domestic animals, and wildlife. Human cases were reported from Kiruhura, Buikwe, Kiboga, and Mityana districts. Of the 24 human blood samples tested, anti-RVFV IgG was detected in 7 (29%) human samples; 1 human sample had detectable IgM only, and 6 had both IgM and IgG. Three of the seven confirmed human cases died among humans. Results from testing animal blood samples obtained from Kiruhura district indicated that 44% (64/146) cattle, 46% (35/76) goats, and 45% (9/20) sheep tested positive for RVF. Among wildlife, (1/10) zebras, (1/1) topi, and (1/1) impala tested positive for RVFV by serological tests. One blood sample from sheep in Kiboga district tested RVFV positive. All the human cases were exposed through contact or consumption of meat from infected animals. Conclusion. RVF outbreaks occurred in humans and animals in Kiruhura, Buikwe, Mityana, and Kiboga districts. Human cases were potentially infected through contact with infected animals and their products.
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Odendaal, Lieza, Sarah J. Clift, Geoffrey T. Fosgate e A. Sally Davis. "Ovine Fetal and Placental Lesions and Cellular Tropism in Natural Rift Valley Fever Virus Infections". Veterinary Pathology 57, n. 6 (4 settembre 2020): 791–806. http://dx.doi.org/10.1177/0300985820954549.
Testo completoAbstract (sommario):
Infection with Rift Valley fever phlebovirus (RVFV) causes abortion storms and a wide variety of outcomes for both ewes and fetuses. Sheep fetuses and placenta specimens were examined during the 2010–2011 River Valley fever (RVF) outbreak in South Africa. A total of 72 fetuses were studied of which 58 were confirmed positive for RVF. Placenta specimens were available for 35 cases. Macroscopic lesions in fetuses were nonspecific and included marked edema and occasional hemorrhages in visceral organs. Microscopically, multifocal hepatic necrosis was present in 48 of 58 cases, and apoptotic bodies, foci of liquefactive hepatic necrosis (primary foci), and eosinophilic intranuclear inclusions in hepatocytes were useful diagnostic features. Lymphocytolysis was present in all lymphoid organs examined with the exception of thymus and Peyer’s patches, and pyknosis or karyorrhexis was often present in renal glomeruli. The most significant histologic lesion in the placenta was necrosis of trophoblasts and endothelial cells in the cotyledonary and intercotyledonary chorioallantois. Immunolabeling for RVFV was most consistent in trophoblasts of the cotyledon or caruncle. Other antigen-positive cells included hepatocytes, renal tubular epithelial, juxtaglomerular and extraglomerular mesangial cells, vascular smooth muscle, endothelial and adrenocortical cells, cardiomyocytes, Purkinje fibers, and macrophages. Fetal organ samples for diagnosis must minimally include liver, kidney, and spleen. From the placenta, the minimum recommended specimens for histopathology include the cotyledonary units and caruncles from the endometrium, if available. The diagnostic investigation of abortion in endemic areas should always include routine testing for RVFV, and a diagnosis during interepidemic periods might be missed if only limited specimens are available for examination.
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Kolawole, Olatunji M., Ajibola O. Ayodeji e Jeremiah I. Ogah. "Prevalence of Rift Valley Fever Virus in Febrile Malaria Patients using Serological and Molecular-based Evidence". Annals of Science and Technology 3, n. 1 (1 giugno 2018): 1–6. http://dx.doi.org/10.2478/ast-2018-0008.
Testo completoAbstract (sommario):
AbstractRift Valley fever virus (RVFV) is a zoonotic virus classified as category A priority pathogen. Rift Valley fever (RVF) has been poorly investigated in Nigeria with the infection among Nigerians last reported in 1996. Two hundred (200) febrile subjects with symptoms of malaria attending local hospitals in Ilorin, Nigeria were investigated for malaria, malaria positive subjects were investigated for the presence of RVF. Malaria screening was done using CarestartTM malaria HRP2(pf), while RVF antibodies were tested for using anti-RVF IgM ELISA. Molecular identification of the viral genome was carried out using RNA extraction (QIAGEN) and quantitative Polymerase Chain Reaction (qPCR). Of the 200 subjects tested for malaria infection, 93 (46.5%) were positive, while 20 (21.5%) of the 93 subjects were seropositive for RVF. RVF virus genome was found in 5 (25%) of the 20 positive subjects. The high prevalence of RVF among malaria positive subjects show that there is a risk of a RVF outbreak if its prevalence remains unchecked.