RESUMEN

Rift Valley fever virus (RVFV) is a mosquito-borne zoonotic pathogen. Its RNA genome consists of two negative-sense segments (L and M) with one gene each, and one ambisense segment (S) with two opposing genes separated by the noncoding "intergenic region" (IGR). These vRNAs and the complementary cRNAs are encapsidated by nucleoprotein (N). Using iCLIP2 (individual-nucleotide resolution UV crosslinking and immunoprecipitation) to map all N-vRNA and N-cRNA interactions, we detect N coverage along the L and M segments. However, the S segment vRNA and cRNA each contain approximately 100 non-encapsidated nucleotides stretching from the IGR into the 5'-adjacent reading frame. These exposed regions are RNase-sensitive and predicted to form stem-loop structures with the mRNA transcription termination motif positioned near the top. Moreover, optimal S segment transcription and replication requires the entire exposed region rather than only the IGR. Thus, the RVFV S segment contains a central, non-encapsidated RNA region with a functional role.

Asunto(s)

ARN Viral , Virus de la Fiebre del Valle del Rift , Virus de la Fiebre del Valle del Rift/genética , ARN Viral/genética , Animales , ADN Intergénico/genética , Genoma Viral , Replicación Viral/genética , Fiebre del Valle del Rift/virología , Fiebre del Valle del Rift/transmisión , Conformación de Ácido Nucleico , Nucleoproteínas/genética , Nucleoproteínas/metabolismo , Humanos , Transcripción Genética

RESUMEN

Rift Valley fever virus (RVFV) is a mosquito-borne RNA virus of the Phlebovirus genus in the phenuviridae family. Its genome is trisegmented with small (S), medium (M) and large (L) fragments. In nature, the virus exists as a single serotype that is responsible for outbreaks of Rift Valley fever (RVF), a zoonotic disease that often occurs in Africa and the Middle East. RVFV genomes are thought to undergo both recombination and reassortment and investigations of these events is important for monitoring the emergence of virulent strains and understanding the evolutionary characteristics of this virus. The aim of this study was to characterize the genomes of RVFV isolates from cattle, sheep, and goats collected during an interepidemic period in Kenya between June 2016 and November 2021. A total of 691 serum samples from cattle (n = 144), goats (n = 185) and sheep (n = 362) were analysed at the Central Veterinary Laboratories. The competitive IgM-capture ELISA, was used to screen the samples; 205 samples (29.67%) tested positive for RVFV. Of the 205 positive samples, 42 (20.5%) were from cattle, 57 (27.8%) from goats, and 106 (51.7%) from sheep. All the IgM-positive samples were further analyzed by qPCR, and 24 (11.71%) tested positive with Ct values ranging from 14.788 to 38.286. Two samples, 201808HABDVS from sheep and 201810CML3DVS from cattle, had Ct values of less than 20.0 and yielded whole genome sequences with 96.8 and 96.4 coverage, respectively. There was no statistically significant evidence of recombination in any of the three segments and also phylogenetic analysis showed no evidence of reassortment in the two isolated RVFV segments when compared with other isolates of different lineages from previous outbreaks whose genomes are deposited in the GenBank. No evidence of reassortment leaves room for other factors to be the most probable contributors of change in virulence, pathogenicity and emergence of highly virulent strains of the RVFV.

Asunto(s)

Enfermedades de los Bovinos , Genoma Viral , Enfermedades de las Cabras , Cabras , Filogenia , Fiebre del Valle del Rift , Virus de la Fiebre del Valle del Rift , Enfermedades de las Ovejas , Animales , Cabras/virología , Virus de la Fiebre del Valle del Rift/genética , Virus de la Fiebre del Valle del Rift/aislamiento & purificación , Ovinos , Fiebre del Valle del Rift/virología , Fiebre del Valle del Rift/epidemiología , Bovinos , Kenia/epidemiología , Enfermedades de las Cabras/virología , Enfermedades de las Cabras/epidemiología , Enfermedades de las Ovejas/virología , Enfermedades de las Ovejas/epidemiología , Enfermedades de los Bovinos/virología , Enfermedades de los Bovinos/epidemiología , Brotes de Enfermedades/veterinaria

RESUMEN

Background: The Rift Valley Fever (RVF) is an arbovirus disease responsible of regular epizootics and epidemics in sub-Saharan Africa and Arabian Peninsula. In 2016, Niger experienced its first outbreak of RVF in Tahoua region, which resulted in high consequences in animal and human health. The aim of this study was to investigate on the RVFV circulation among potential vectors of the disease. Methods: This was a cross-sectional survey carried out in Tahoua and Agadez regions in August 2021. Adult mosquitoes were collected by using the morning spray in human dwellings and the CDC light trap methods. After morphological identification, viral RNA was extracted. The RNA was extracted by using QIAamp Viral RNA Mini Kit (Qiagen). The RVFV detection was performed by using the qRT-PCR method. Results: A total of 2487 insects (1978 mosquitoes, 509 sandflies and 251 biting midges) were identified and divided into three families (Culicidae, Psychodidae and Ceratopogonidae). The Culicidae family composed of the Culex genus being the most abundant with a predominance of Cx.pipiens (31.88%; n = 793) followed by Mansonia sp (21.51%; n = 535), Anophelesgambiae s.l. (8.44%; n = 210), An. pharoensis (0.72%; n = 18), An. rufipes (0.48%; n = 12), Cx. quinquefasciatus (6.39%; n = 159), the Psychodidae with sandflies (20.46%; n = 509), and the Ceratopogonidae with Culicoides genus (10.09%; n = 251). The qRT-PCR carried out on a sample of mosquitoes (N = 96) highlighted that one individual of Cx.pipiens was found positive to RVFV. This specimen was from Tassara locality (Tahoua) and collected by CDC Light Trap method. Conclusion: This study reveals for the first time the circulation of RVFV among Cx.pipiens in Niger and highlights the possible vectorial role of this vector in the disease transmission. Further investigations should be carried out to identify the biological and ecological determinants that support the maintenance of the virus in this area in order to guide control interventions.

Asunto(s)

Culex , Fiebre del Valle del Rift , Virus de la Fiebre del Valle del Rift , Animales , Virus de la Fiebre del Valle del Rift/aislamiento & purificación , Virus de la Fiebre del Valle del Rift/genética , Culex/virología , Estudios Transversales , Fiebre del Valle del Rift/epidemiología , Fiebre del Valle del Rift/transmisión , Fiebre del Valle del Rift/virología , Niger/epidemiología , Mosquitos Vectores/virología , Humanos , Insectos Vectores/virología

RESUMEN

BACKGROUND: Rift Valley fever virus (RVFV) is a zoonotic mosquito-borne virus with serious implications for livestock health, human health, and the economy in Africa, and is suspected to be endemic in north-eastern KwaZulu-Natal (KZN), South Africa. The vectors of RVFV in this area are poorly known, although several species, such as Aedes (Neomelaniconion) mcintoshi, Aedes (Neomelaniconion) circumluteolus, Aedes (Aedimorphus) durbanensis, and Culex (Lasioconops) poicilipes may be involved. The aim of the study was to determine the vertebrate blood meal sources of potential RVFV mosquito vectors in north-eastern KZN and to characterize the host-biting network. METHODS: Blood-fed mosquitoes were collected monthly from November 2019 to February 2023 using a backpack aspirator, CO2-baited Centers for Disease Control and Prevention (CDC) miniature light traps and tent traps, in the vicinity of water bodies and livestock farming households. The mosquitoes were morphologically identified. DNA was extracted from individual mosquitoes and used as templates to amplify the vertebrate cytochrome c oxidase I (COI) and cytochrome b (cytb) genes using conventional polymerase chain reaction (PCR). Amplicons were sequenced and queried in GenBank and the Barcode of Life Data systems to identify the vertebrate blood meal sources and confirm mosquito identifications. All mosquitoes were screened for RVFV using real time reverse transcription (RT)-PCR. RESULTS: We identified the mammalian (88.8%) and avian (11.3%) blood meal sources from 409 blood-fed mosquitoes. Aedes circumluteolus (n = 128) made up the largest proportion of collected mosquitoes. Cattle (n = 195) and nyala (n = 61) were the most frequent domestic and wild hosts, respectively. Bipartite network analysis showed that the rural network consisted of more host-biting interactions than the reserve network. All mosquitoes tested negative for RVFV. CONCLUSIONS: Several mosquito species, including Ae. circumluteolus, and vertebrate host species, including cattle and nyala, could play a central role in RVFV transmission. Future research in this region should focus on these species to better understand RVFV amplification.

Asunto(s)

Aedes , Mosquitos Vectores , Fiebre del Valle del Rift , Virus de la Fiebre del Valle del Rift , Animales , Sudáfrica , Mosquitos Vectores/virología , Mosquitos Vectores/fisiología , Virus de la Fiebre del Valle del Rift/genética , Virus de la Fiebre del Valle del Rift/aislamiento & purificación , Virus de la Fiebre del Valle del Rift/fisiología , Fiebre del Valle del Rift/transmisión , Fiebre del Valle del Rift/virología , Fiebre del Valle del Rift/epidemiología , Aedes/virología , Aedes/fisiología , Aedes/genética , Aedes/clasificación , Humanos , Conducta Alimentaria , Culex/virología , Culex/fisiología , Mordeduras y Picaduras de Insectos , Femenino , Culicidae/virología , Culicidae/fisiología , Culicidae/clasificación

RESUMEN

The Rift Valley fever virus (RVFV), transmitted through mosquito bites, leads to severe illness in humans and livestock throughout Africa and the Arabian Peninsula, causing significant morbidity and mortality. As of now, there are no verified and efficacious drugs or licensed vaccines accessible for the prevention or treatment of RVFV infections in both humans and livestock. The mature RVFV virion has two envelope proteins on its surface: glycoprotein N (GN) and glycoprotein C (GC). These proteins play a significant role in facilitating the virus's entry into the host cell, making them prominent targets for entry mechanism research as well as targets for drugs and vaccine development. The initial stage in obtaining atomic-resolution structural and mechanistic information on viral entry as well as developing biochemical and biophysical research tools involves recombinant protein production. In this chapter, we describe a simplified and scalable protocol facilitating the generation of high-quality, high-titer baculovirus virus for expression and purification of RVFV GC, utilizing the baculovirus-mediated expression system in insect cells.

Asunto(s)

Baculoviridae , Proteínas Recombinantes , Virus de la Fiebre del Valle del Rift , Proteínas del Envoltorio Viral , Baculoviridae/genética , Animales , Proteínas del Envoltorio Viral/genética , Proteínas del Envoltorio Viral/aislamiento & purificación , Proteínas del Envoltorio Viral/química , Proteínas del Envoltorio Viral/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/aislamiento & purificación , Proteínas Recombinantes/metabolismo , Virus de la Fiebre del Valle del Rift/genética , Células Sf9 , Expresión Génica , Humanos , Vectores Genéticos/genética , Clonación Molecular/métodos

RESUMEN

Rift Valley fever virus (RVFV) is a pathogen transmitted to humans and livestock via mosquito bites. This virus, which was discovered in Kenya in 1930, is considered by the World Health Organization (WHO) and the World Organisation for Animal Health (WOAH) to be associated with a high risk of causing large-scale epidemics. However, means dedicated to fighting RVFV have been limited, and despite recent research efforts, the virus remains poorly understood at both the molecular and cellular levels as well as at a broader scale of research in the field and in animal and human populations. In this introductory chapter of a methods book, we aim to provide readers with a concise overview of RVFV, from its ecology and transmission to the structural and genomic organization of virions and its life cycle in host cells.

Asunto(s)

Fiebre del Valle del Rift , Virus de la Fiebre del Valle del Rift , Virus de la Fiebre del Valle del Rift/genética , Fiebre del Valle del Rift/transmisión , Fiebre del Valle del Rift/virología , Animales , Humanos , Genoma Viral

RESUMEN

RT-qPCR allows the detection of viruses and the monitoring of viral replication. This technique was extensively employed during the SARS-CoV-2 pandemic, where it demonstrated its efficiency and robustness. Here we describe the analysis of Rift Valley fever and Toscana virus infections over time, achieved through the RT-qPCR quantification of the viral genome. We further elaborate on the method to discriminate between genomic and antigenomic viral RNAs by using primers specific for each strand during the reverse transcription step.

Asunto(s)

ARN Viral , Fiebre del Valle del Rift , Virus de la Fiebre del Valle del Rift , Virus de la Fiebre del Valle del Rift/genética , ARN Viral/genética , Fiebre del Valle del Rift/virología , Fiebre del Valle del Rift/diagnóstico , Humanos , Genoma Viral , Reacción en Cadena en Tiempo Real de la Polimerasa/métodos , Replicación Viral/genética , Animales

RESUMEN

Like all the RNA viruses, Rift Valley fever virus (RVFV) encodes only few viral proteins and relies heavily on the host cellular machinery for productive infection. This dependence creates a potential "Achille's heel" that may be exploited to develop new approaches to treat RVFV infection. The recent development of lentiviral sgRNAs pool has enabled the creation of genome-scale CRISPR-Cas9 knockout libraries that has been used to identify host factors required for virus replication. In this chapter, we describe the preparation and execution of a pooled CRISPR-Cas9 loss-of-function screen using virus-induced cell death phenotypic readout. Using this technique, we outline a strategy for the identification of host factors essential for important human emerging viruses such as RVFV.

Asunto(s)

Sistemas CRISPR-Cas , Virus de la Fiebre del Valle del Rift , Humanos , Virus de la Fiebre del Valle del Rift/genética , Replicación Viral/genética , Interacciones Huésped-Patógeno/genética , Técnicas de Inactivación de Genes , ARN Guía de Sistemas CRISPR-Cas/genética

RESUMEN

The nucleocapsid protein (N) in Rift Valley fever virus is an RNA-binding protein that functions in viral transcription, replication, and packaging. In this chapter, the method for studying protein-RNA interactions in context of viral infection using individual nucleotide resolution, cross-linking, immunoprecipitation, and sequencing (iCLIP-seq) is explained. The method is useful for identifying the interactions between both host and viral RNAs with N and can identify RNA motifs that interact with the protein of interest.

Asunto(s)

Inmunoprecipitación , Proteínas de la Nucleocápside , ARN Viral , Virus de la Fiebre del Valle del Rift , Proteínas de la Nucleocápside/metabolismo , ARN Viral/metabolismo , ARN Viral/genética , Sitios de Unión , Virus de la Fiebre del Valle del Rift/genética , Virus de la Fiebre del Valle del Rift/metabolismo , Inmunoprecipitación/métodos , Unión Proteica , Humanos , Proteínas de Unión al ARN/metabolismo , Secuenciación de Nucleótidos de Alto Rendimiento/métodos

RESUMEN

Rift Valley fever (RVF) virus is widespread worldwide and poses a severe threat to human life and property. RVF viral polymerase plays a vital role in the replication and transcription of the virus. Here, we describe how to express and purify this polymerase and perform tests for its in vitro activity assays.

Asunto(s)

Virus de la Fiebre del Valle del Rift , Virus de la Fiebre del Valle del Rift/genética , Saccharomyces cerevisiae/genética , Proteínas Virales/metabolismo , Proteínas Virales/genética , Pruebas de Enzimas/métodos , Humanos , Expresión Génica , Replicación Viral/genética

RESUMEN

Rift Valley fever virus (RVFV; genus Phlebovirus, family Phenuiviridae, order Bunyavirales) is a mosquito-borne zoonotic pathogen endemic in Africa. Its negative-stranded genomic RNA (vRNA) is divided into three segments termed L, M, and S. Both vRNAs and antigenomic cRNAs are encapsidated by viral nucleoprotein (N) to form nucleocapsids, which constitute the template for genome transcription and replication. Based on a number of electron microscopy and structural studies, the viral RNAs of negative-strand RNA viruses, including phleboviruses, are commonly considered to be entirely and uniformly covered by N protein. However, high resolution data supporting this notion was missing to date.Here, we describe a method how to globally map all N-RNA interactions of RVFV by using iCLIP (individual-nucleotide resolution UV cross-linking and immunoprecipitation). The protocol is based on covalent cross-linking of direct protein-RNA interactions by UV irradiation. Following sample lysis, a selective isolation of N in complex with its RNA targets is achieved by immunoprecipitation. Then, N-RNA complexes are separated by SDS-PAGE, and after membrane transfer, RNA is isolated and subjected to library preparation and high-throughput sequencing. We explain how the standard iCLIP protocol can be adapted to RVFV N-RNA interaction studies. The protocol describes mapping of all N interactions with the vRNAs and cRNAs derived either from RVFV particles or from infected cells.

Asunto(s)

Genoma Viral , Nucleoproteínas , ARN Viral , Virus de la Fiebre del Valle del Rift , Virus de la Fiebre del Valle del Rift/genética , ARN Viral/genética , ARN Viral/metabolismo , Nucleoproteínas/metabolismo , Nucleoproteínas/genética , Mapeo Nucleótido/métodos , Inmunoprecipitación/métodos , Humanos , Fiebre del Valle del Rift/virología , Fiebre del Valle del Rift/metabolismo , Animales

RESUMEN

The genome of most bunyaviruses is divided over three (S, M, and L) single-stranded RNA segments of negative polarity. The three viral RNA segments are essential to establish a productive infection. RNA fluorescence in situ hybridization (FISH) enables the detection, localization, and quantification of RNA molecules at single-molecule resolution. This chapter describes an RNA FISH method to directly visualize individual segment-specific bunyavirus RNAs in fixed infected cells and in mature virus particles, using Rift Valley fever virus as an example. Imaging of bunyavirus RNA segments is a valuable experimental tool to investigate fundamental aspects of the bunyavirus life cycle, such as virus replication, genome packaging, and virion assembly, among others.

Asunto(s)

Genoma Viral , Hibridación Fluorescente in Situ , ARN Viral , Hibridación Fluorescente in Situ/métodos , ARN Viral/genética , Imagen Individual de Molécula/métodos , Animales , Replicación Viral/genética , Virus de la Fiebre del Valle del Rift/genética , Orthobunyavirus/genética , Humanos

RESUMEN

RNAseq is a valuable tool that can aid researchers in uncovering the transcriptional changes that occur when a viral pathogen infects a host cell. Viral infection will invariably cause differential expression of many genes, from transcription of mRNA to alternative splicing and degradation. This change in gene expression can be a result of immune activation or a direct activity of the virus to alter the host cell's environment to make it more favorable for viral replication. Studying the innate immune response to a pathogen can reveal which cellular pathways are active, indicating the steps that the host takes to halt viral infection, and detecting virus-mediated mRNA expression changes can help with identifying the pathways which may be exploited by the virus. Gene expression changes-both cell-caused and virus-caused-can be studied through RNAseq, helping to provide a clearer picture of the cellular changes that occur during viral infection. In this protocol, we outline methods to carry out mRNA sequencing in Rift Valley fever virus-infected cell cultures, from infection to library prep and analysis.

Asunto(s)

Fiebre del Valle del Rift , Virus de la Fiebre del Valle del Rift , Virus de la Fiebre del Valle del Rift/genética , Virus de la Fiebre del Valle del Rift/fisiología , Humanos , Fiebre del Valle del Rift/virología , Fiebre del Valle del Rift/genética , Interacciones Huésped-Patógeno/genética , Análisis de Secuencia de ARN/métodos , ARN Mensajero/genética , ARN Mensajero/metabolismo , Animales , Replicación Viral/genética , Empalme Alternativo , Empalme del ARN , Transcripción Genética , Línea Celular

RESUMEN

The NSs protein is a major virulence factor in bunyaviruses, crucial for viral pathogenesis. However, assessing NSs protein function can be challenging due to its inhibition of cellular RNA polymerase II, impacting NSs protein expression from plasmid DNA. The recombinant Rift Valley fever virus (RVFV) MP-12 strain (rMP-12), a highly attenuated vaccine strain, can be safely manipulated under biosafety level 2 conditions. Leveraging a reverse genetics system, we can engineer rMP-12 variants expressing heterologous NSs genes, enabling functional testing in cultured cells. Human macrophages hold a central role in viral pathogenesis, making them an ideal model for assessing NSs protein functions. Consequently, we can comprehensively compare and analyze the functional significance of various NSs proteins in human macrophages using rMP-12 NSs variants. In this chapter, we provide a detailed overview of the preparation process for rMP-12 NSs variants and introduce two distinct human macrophage models: THP-1 cells and primary macrophages. This research framework promises valuable insights into the virulence mechanisms of RVFV and other bunyaviruses and the potential for vaccine development.

Asunto(s)

Macrófagos , Virus de la Fiebre del Valle del Rift , Proteínas no Estructurales Virales , Humanos , Macrófagos/virología , Macrófagos/inmunología , Virus de la Fiebre del Valle del Rift/genética , Virus de la Fiebre del Valle del Rift/patogenicidad , Proteínas no Estructurales Virales/genética , Proteínas no Estructurales Virales/metabolismo , Células THP-1

RESUMEN

Rift Valley fever virus is able to infect multiple organs and cell types, and the course of infection varies between viral strains and between individuals in particular according to age, genetic background, and physiological status. Studies on viral and host factors involve detecting and quantifying viral load at multiple time points and in multiple tissues. While this is classically performed by genome quantification or viral titration, in vivo imaging techniques using recombinant viruses expressing a bioluminescent or fluorescent protein allow noninvasive longitudinal studies on the same group of mice over the entire course of disease and the detection of unsuspected sites of infection. Here, we describe the protocol to monitor and characterize mouse infection with Rift Valley fever virus by in vivo imaging using recombinant viruses expressing light-emitting reporter genes.

Asunto(s)

Genes Reporteros , Mediciones Luminiscentes , Virus de la Fiebre del Valle del Rift , Animales , Ratones , Mediciones Luminiscentes/métodos , Virus de la Fiebre del Valle del Rift/genética , Fiebre del Valle del Rift/virología , Fiebre del Valle del Rift/diagnóstico , Carga Viral/métodos , Modelos Animales de Enfermedad , Humanos , Proteínas Luminiscentes/genética , Proteínas Luminiscentes/metabolismo

RESUMEN

Rift Valley fever (RVF) is a mosquito-borne zoonotic viral disease endemic to Africa and the Middle East. Live-attenuated RVF vaccines have been studied for both veterinary and human use due to their strong immunogenicity and cost-effective manufacturing. The live-attenuated MP-12 vaccine has been conditionally approved for veterinary use in the U.S.A., and next-generation live-attenuated RVF vaccine candidates are being actively researched. Assessing the virulence phenotype of vaccine seeds or lots is crucial for managing vaccine safety. Previously, preweaning 19-day-old outbred CD1 mice have been used to evaluate the MP-12 strain. This study aimed to characterize the relative virulence of three live-attenuated RVF vaccine strains in 19-day-old inbred C57BL/6 mice: the recombinant MP-12 (rMP-12), the RVax-1, and the ∆NSs-∆NSm-rZH501 strains. Although this mouse model did not show dose-dependent pathogenesis, mice that succumbed to the infection exhibited distinct brain pathology. Mice infected with ∆NSs-∆NSm-rZH501 showed an infiltration of inflammatory cells associated with infected neurons, and focal lesions formed around virus-infected cells. In contrast, mice infected with rMP-12 or RVax-1 showed a minimal association of inflammatory cells in the brain, yet the virus spread diffusely. The preweaning model is likely useful for evaluating host responses to attenuated RVFV strains, although further refinement may be necessary to quantitate the virulence among different RVFV strains or vaccine lots.

Asunto(s)

Modelos Animales de Enfermedad , Ratones Endogámicos C57BL , Fiebre del Valle del Rift , Virus de la Fiebre del Valle del Rift , Vacunas Atenuadas , Vacunas Virales , Animales , Virus de la Fiebre del Valle del Rift/patogenicidad , Virus de la Fiebre del Valle del Rift/inmunología , Virus de la Fiebre del Valle del Rift/genética , Fiebre del Valle del Rift/virología , Fiebre del Valle del Rift/patología , Fiebre del Valle del Rift/prevención & control , Fiebre del Valle del Rift/inmunología , Ratones , Vacunas Atenuadas/inmunología , Vacunas Atenuadas/administración & dosificación , Vacunas Virales/inmunología , Vacunas Virales/administración & dosificación , Virulencia , Femenino

RESUMEN

Rift Valley fever (RVF) is a re-emerging vector-borne zoonosis with a high public health and veterinary impact. In West Africa, many lineages were previously detected, but since 2020, lineage H from South Africa has been the main cause of the outbreaks. In this study, clinical samples collected through national surveillance were screened for RVF virus (RVFV) acute infection by RT-PCR and IgM ELISA tests. Sequencing, genome mapping and in vitro phenotypic characterization in mammal cells were performed on RT-PCR positive samples in comparison with other epidemic lineages (G and C). Four RVFV human cases were detected in Senegal and the sequence analyses revealed that the strains belonged to lineage H. The in vitro kinetics and genome mapping showed different replication efficiency profiles for the tested RVFV lineages and non-conservative mutations, which were more common to lineage G or specific to lineage H. Our findings showed the re-emergence of lineage H in Senegal in 2022, its high viral replication efficiency in vitro and support the findings that genetic diversity affects viral replication. This study gives new insights into the biological properties of lineage H and calls for deeper studies to better assess its potential to cause a future threat in Senegal.

Asunto(s)

Genoma Viral , Filogenia , Fiebre del Valle del Rift , Virus de la Fiebre del Valle del Rift , Replicación Viral , Virus de la Fiebre del Valle del Rift/genética , Virus de la Fiebre del Valle del Rift/aislamiento & purificación , Virus de la Fiebre del Valle del Rift/clasificación , Virus de la Fiebre del Valle del Rift/fisiología , Fiebre del Valle del Rift/virología , Fiebre del Valle del Rift/epidemiología , Fiebre del Valle del Rift/transmisión , Senegal/epidemiología , Humanos , Animales , Enfermedades Transmisibles Emergentes/virología , Enfermedades Transmisibles Emergentes/epidemiología , Enfermedades Transmisibles Emergentes/veterinaria , Brotes de Enfermedades , África Occidental/epidemiología , Variación Genética , Mutación

RESUMEN

Phenuiviruses are a class of segmented negative-sense single-stranded RNA viruses, typically consisting of three RNA segments that encode four distinct proteins. The emergence of pathogenic phenuivirus strains, such as Rift Valley fever phlebovirus (RVFV) in sub-Saharan Africa, Severe Fever with Thrombocytopenia Syndrome Virus (SFTSV) in East and Southeast Asia, and Heartland Virus (HRTV) in the United States has presented considerable challenges to global public health in recent years. The innate immune system plays a crucial role as the initial defense mechanism of the host against invading pathogens. In addition to continued research aimed at elucidating the epidemiological characteristics of phenuivirus, significant advancements have been made in investigating its viral virulence factors (glycoprotein, non-structural protein, and nucleoprotein) and potential host-pathogen interactions. Specifically, efforts have focused on understanding mechanisms of viral immune evasion, viral assembly and egress, and host immune networks involving immune cells, programmed cell death, inflammation, nucleic acid receptors, etc. Furthermore, a plethora of technological advancements, including metagenomics, metabolomics, single-cell transcriptomics, proteomics, gene editing, monoclonal antibodies, and vaccines, have been utilized to further our understanding of phenuivirus pathogenesis and host immune responses. Hence, this review aims to provide a comprehensive overview of the current understanding of the mechanisms of host recognition, viral immune evasion, and potential therapeutic approaches during human pathogenic phenuivirus infections focusing particularly on RVFV and SFTSV.

Asunto(s)

Interacciones Huésped-Patógeno , Inmunidad Innata , Humanos , Interacciones Huésped-Patógeno/inmunología , Phlebovirus/inmunología , Phlebovirus/genética , Phlebovirus/patogenicidad , Evasión Inmune , Factores de Virulencia/genética , Factores de Virulencia/inmunología , Virus de la Fiebre del Valle del Rift/inmunología , Virus de la Fiebre del Valle del Rift/genética , Virus de la Fiebre del Valle del Rift/patogenicidad , Sistema Inmunológico/virología , Sistema Inmunológico/inmunología

RESUMEN

Rift Valley fever (RVF) is a mosquito-borne zoonotic disease caused by RVF virus (RVFV). RVFV infections in humans are usually asymptomatic or associated with mild febrile illness, although more severe cases of haemorrhagic disease and encephalitis with high mortality also occur. Currently, there are no licensed human vaccines available. The safety and efficacy of a genetically engineered four-segmented RVFV variant (hRVFV-4s) as a potential live-attenuated human vaccine has been tested successfully in mice, ruminants, and marmosets though the correlates of protection of this vaccine are still largely unknown. In the present study, we have assessed hRVFV-4s-induced humoral and cellular immunity in a mouse model of RVFV infection. Our results confirm that a single dose of hRVFV-4s is highly efficient in protecting naïve mice from developing severe disease following intraperitoneal challenge with a highly virulent RVFV strain and data show that virus neutralizing (VN) serum antibody titres in a prime-boost regimen are significantly higher compared to the single dose. Subsequently, VN antibodies from prime-boost-vaccinated recipients were shown to be protective when transferred to naïve mice. In addition, hRVFV-4s vaccination induced a significant virus-specific T cell response as shown by IFN-γ ELISpot assay, though these T cells did not provide significant protection upon passive transfer to naïve recipient mice. Collectively, this study highlights hRVFV-4s-induced VN antibodies as a major correlate of protection against lethal RVFV infection.

Asunto(s)

Anticuerpos Neutralizantes , Anticuerpos Antivirales , Fiebre del Valle del Rift , Virus de la Fiebre del Valle del Rift , Vacunas Atenuadas , Vacunas Virales , Animales , Virus de la Fiebre del Valle del Rift/inmunología , Virus de la Fiebre del Valle del Rift/genética , Fiebre del Valle del Rift/prevención & control , Fiebre del Valle del Rift/inmunología , Vacunas Virales/inmunología , Vacunas Virales/administración & dosificación , Ratones , Anticuerpos Antivirales/sangre , Anticuerpos Antivirales/inmunología , Anticuerpos Neutralizantes/sangre , Anticuerpos Neutralizantes/inmunología , Femenino , Vacunas Atenuadas/inmunología , Vacunas Atenuadas/administración & dosificación , Modelos Animales de Enfermedad , Inmunidad Celular , Linfocitos T/inmunología , Inmunidad Humoral , Ratones Endogámicos BALB C , Interferón gamma/inmunología , Vacunación

RESUMEN

Rift Valley fever (RVF), a mosquito-borne transboundary zoonosis, was first confirmed in Rwanda's livestock in 2012 and since then sporadic cases have been reported almost every year. In 2018, the country experienced its first large outbreak, which was followed by a second one in 2022. To determine the circulating virus lineages and their ancestral origin, two genome sequences from the 2018 outbreak, and thirty-six, forty-one, and thirty-eight sequences of small (S), medium (M), and large (L) genome segments, respectively, from the 2022 outbreak were generated. All of the samples from the 2022 outbreak were collected from slaughterhouses. Both maximum likelihood and Bayesian-based phylogenetic analyses were performed. The findings showed that RVF viruses belonging to a single lineage, C, were circulating during the two outbreaks, and shared a recent common ancestor with RVF viruses isolated in Uganda between 2016 and 2019, and were also linked to the 2006/2007 largest East Africa RVF outbreak reported in Kenya, Tanzania, and Somalia. Alongside the wild-type viruses, genetic evidence of the RVFV Clone 13 vaccine strain was found in slaughterhouse animals, demonstrating a possible occupational risk of exposure with unknown outcome for people working in meat-related industry. These results provide additional evidence of the ongoing wide spread of RVFV lineage C in Africa and emphasize the need for an effective national and international One Health-based collaborative approach in responding to RVF emergencies.

Asunto(s)

Brotes de Enfermedades , Genoma Viral , Ganado , Filogenia , Fiebre del Valle del Rift , Virus de la Fiebre del Valle del Rift , Animales , Rwanda/epidemiología , Fiebre del Valle del Rift/epidemiología , Fiebre del Valle del Rift/virología , Fiebre del Valle del Rift/transmisión , Virus de la Fiebre del Valle del Rift/genética , Virus de la Fiebre del Valle del Rift/clasificación , Virus de la Fiebre del Valle del Rift/aislamiento & purificación , Ganado/virología , Bovinos , Mataderos , Genómica/métodos