RESUMO
Bunyaviruses are negative sense, single-strand RNA viruses that infect a wide range of vertebrate, invertebrate and plant hosts. WHO lists three bunyavirus diseases as priority diseases requiring urgent development of medical countermeasures highlighting their high epidemic potential. While the viral large (L) protein containing the RNA-dependent RNA polymerase is a key enzyme in the viral replication cycle and therefore a suitable drug target, our knowledge on the structure and activities of this multifunctional protein has, until recently, been very limited. However, in the last few years, facilitated by the technical advances in the field of cryogenic electron microscopy, many structures of bunyavirus L proteins have been solved. These structures significantly enhance our mechanistic understanding of bunyavirus genome replication and transcription processes and highlight differences and commonalities between the L proteins of different bunyavirus families. Here, we provide a review of our current understanding of genome replication and transcription in bunyaviruses with a focus on the viral L protein. Further, we compare within bunyaviruses and with the related influenza virus polymerase complex and highlight open questions.
Assuntos
Bunyaviridae , Orthobunyavirus , Bunyaviridae/genética , Bunyaviridae/metabolismo , Orthobunyavirus/genética , RNA , Proteínas Virais/genética , Proteínas Virais/metabolismo , Replicação Viral/genéticaRESUMO
Phytophthora cactorum is an important oomycetous plant pathogen with numerous host plant species, including garden strawberry (Fragaria × ananassa) and silver birch (Betula pendula). P. cactorum also hosts mycoviruses, but their phenotypic effects on the host oomycete have not been studied earlier. In the present study, we tested polyethylene glycol (PEG)-induced water stress for virus curing and created an isogenic virus-free isolate for testing viral effects in pair with the original isolate. Phytophthora cactorum bunya-like viruses 1 and 2 (PcBV1 & 2) significantly reduced hyphal growth of the P. cactorum host isolate, as well as sporangia production and size. Transcriptomic and proteomic analyses revealed an increase in the production of elicitins due to bunyavirus infection. However, the presence of bunyaviruses did not seem to alter the pathogenicity of P. cactorum. Virus transmission through anastomosis was unsuccessful in vitro.
Assuntos
Bunyaviridae , Orthobunyavirus , Phytophthora , Proteômica , Perfilação da Expressão Gênica , Betula , PlantasRESUMO
Bunyaviruses represent the largest group of RNA viruses and are the causative agent of a variety of febrile and hemorrhagic illnesses. Originally characterized as a single serotype in Africa, the number of described bunyaviruses now exceeds over 500, with its presence detected around the world. These predominantly tri-segmented, single-stranded RNA viruses are transmitted primarily through arthropod and rodent vectors and can infect a wide variety of animals and plants. Although encoding for a small number of proteins, these viruses can inflict potentially fatal disease outcomes and have even developed strategies to suppress the innate antiviral immune mechanisms of the infected host. This short review will attempt to provide an overall description of the order Bunyavirales, describing the mechanisms behind their infection, replication, and their evasion of the host immune response. Furthermore, the historical context of these viruses will be presented, starting from their original discovery almost 80 years ago to the most recent research pertaining to viral replication and host immune response.
Assuntos
Bunyaviridae , Orthobunyavirus , Vírus de RNA , Animais , Bunyaviridae/fisiologia , Replicação Viral , AntiviraisRESUMO
Members of the order Bunyavirales infect a wide variety of host species, including plants, animals and humans, and pose a threat to public health. Major families in this order have tri-segmented negative-sense RNA genomes, the 5' and 3' ends of which form complementary strands that serve as a replication promoter. Elucidation of the mechanisms by which viral polymerases recognize the promoter to initiate RNA synthesis is important for understanding viral replication and pathogenesis, and developing antivirals. A list of replication promoter configuration patterns may provide details on the differences in the replication mechanisms among bunyaviruses. By using public sequence data of all known bunyavirus species, we constructed a comprehensive list of the replication promoters comprising 40 nucleotides in both the 5' and 3' ends of the genome that form a specific complementary strand. Among tri-segmented bunyaviruses, members of the family Nairoviridae, including the highly pathogenic Crimean-Congo hemorrhagic fever virus, have evolved a GC-rich promoter structure differing from that of other families. The unique promoter structure might be related to the large genome size of the family Nairoviridae among bunyaviruses, and the large genome architecture might confer pathogenic advantages. The promoter list provided in this report is useful for predicting the virus family-specific replication mechanisms of bunyaviruses.
Assuntos
Bunyaviridae , Vírus da Febre Hemorrágica da Crimeia-Congo , Vírus de RNA , Animais , Bunyaviridae/química , Bunyaviridae/genética , Vírus da Febre Hemorrágica da Crimeia-Congo/genética , Humanos , RNA , Vírus de RNA/genética , Replicação Viral/genéticaRESUMO
Bunyaviruses cause diseases in vertebrates, arthropods, and plants. Here, we used high-throughput RNA-seq to identify a bunya-like virus in rice plants showing the dwarfing symptom, which was tentatively named rice dwarf-associated bunya-like virus (RDaBV). The RDaBV genome consists of L, M, and S segments. The L segment has 6562 nt, and encodes an RdRp with a conserved Bunya_RdRp super family domain. The M segment has 1667 nt and encodes a nonstructural protein (NS). The complementary strand of the 1120 nt S segment encodes a nucleocapsid protein (N), while its viral strand encodes a small nonstructural protein (NSs). The amino acid (aa) sequence identities of RdRp, NS, and N between RDaBV and viruses from the family Discoviridae were the highest. Surprisingly, the RDaBV NSs protein did not match any viral proteins. Phylogenetic analysis based on RdRp indicated that RDaBV is evolutionarily close to viruses in the family Discoviridae. The PVX-expressed system indicated that RDaBV N and NS may be symptom determinants of RDaBV. Our movement complementation and callose staining experiment results confirmed that RDaBV NSs is a viral movement protein in plants, while an agro-infiltration experiment found that RDaBV NS is an RNA silencing suppressor. Thus, we determined that RDaBV is a novel rice-infecting bunya-like virus.
Assuntos
Bunyaviridae , Oryza , Vírus não Classificados , Animais , Bunyaviridae/genética , Vírus de DNA/genética , Genoma Viral , Genômica , Oryza/genética , Filogenia , RNA Viral/genética , RNA Polimerase Dependente de RNA , Reoviridae , Proteínas Virais/química , Proteínas Virais/genética , Vírus não Classificados/genéticaRESUMO
The Bunyavirales contain many important human pathogens that lack an antiviral therapy. The cap-snatching endonuclease (EN) of segmented negative-strand RNA viruses is an attractive target for broad-spectrum antivirals due to its essential role in initiating viral transcription. L-742,001, a previously reported diketo acid inhibitor against influenza virus EN, demonstrated potent EN inhibition and antiviral activity on various bunyaviruses. However, the precise inhibitory mechanism of the compound is still poorly understood. We recently characterized a highly active EN from Ebinur Lake virus (EBIV), a newly identified member of the Orthobunyavirus genus, and obtained its high-resolution structures, paving the way for structure-guided inhibitor development. Here, nine L-742,001 derivatives were designed and synthesized de novo, and their structure-activity relationship with EBIV EN was studied. In vitro biochemical data showed that the compounds inhibited the EBIV EN activity with different levels and could be divided into three categories. Five representative compounds were selected for further cell-based antiviral assay, and the results largely agreed with those of the EN assays. Furthermore, the precise binding modes of L-742,001 and its derivatives in EN were revealed by determining the high-resolution crystal structures of EN-inhibitor complexes, which suggested that the p-chlorobenzene is essential for the inhibitory activity and the flexible phenyl has the greatest exploration potential. This study provides an important basis for the structure-based design and optimization of inhibitors targeting EN of segmented negative-strand RNA viruses. IMPORTANCE The Bunyavirales contain many important human pathogens such as Crimean-Congo hemorrhagic fever virus and Lassa virus that pose serious threats to public health; however, currently there are no specific antiviral drugs against these viruses. The diketo acid inhibitor L-742,001 is a potential drug as it inactivates the cap-snatching endonuclease (EN) encoded by bunyaviruses. Here, we designed and synthesized nine L-742,001 derivatives and assessed the structure-activity relationship using EN of the newly identified Ebinur Lake virus (EBIV) as a research model. Our results revealed that the p-chlorobenzene of this broad-spectrum EN inhibitor is crucial for the inhibitory activity and the flexible phenyl "arm" has the best potential for further optimization. As cap-snatching ENs are present not only in bunyaviruses but also in influenza viruses, our data provide important guidelines for the development of novel and more potent diketo acid-based antiviral drugs against those viruses.
Assuntos
Antivirais , Bunyaviridae , Endonucleases , Proteínas Virais , Antivirais/síntese química , Antivirais/farmacologia , Antivirais/uso terapêutico , Bunyaviridae/enzimologia , Infecções por Bunyaviridae/tratamento farmacológico , Infecções por Bunyaviridae/virologia , Endonucleases/metabolismo , Ativação Enzimática/efeitos dos fármacos , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/farmacologia , Inibidores Enzimáticos/uso terapêutico , Humanos , Hidroxibutiratos/química , Hidroxibutiratos/farmacologia , Hidroxibutiratos/uso terapêutico , Piperidinas/química , Piperidinas/farmacologia , Piperidinas/uso terapêutico , Relação Estrutura-Atividade , Proteínas Virais/metabolismoRESUMO
Heartland bandavirus (HRTV), which is an emerging tick-borne virus first identified in Missouri in 2009, causes fever, fatigue, decreased appetite, headache, nausea, diarrhea, and muscle or joint pain in humans. HRTV is genetically close to Dabie bandavirus, which is the causative agent of severe fever with thrombocytopenia syndrome (SFTS) in humans and is known as SFTS virus (SFTSV). The generation of infectious HRTV entirely from cloned cDNAs has not yet been reported. The absence of a reverse genetics system for HRTV has delayed efforts to understand its pathogenesis and to generate vaccines and antiviral drugs. Here, we developed a reverse genetics system for HRTV, which employs an RNA polymerase I-mediated expression system. A recombinant nonstructural protein (NSs)-knockout HRTV (rHRTV-NSsKO) was generated. We found that NSs interrupted signaling associated with innate immunity in HRTV-infected cells. The rHRTV-NSsKO was highly attenuated, indicated by the apparent absence of symptoms in a mouse model of HRTV infection. Moreover, mice immunized with rHRTV-NSsKO survived a lethal dose of HRTV. These findings suggest that NSs is a virulence factor of HRTV and that rHRTV-NSsKO could be a vaccine candidate for HRTV. IMPORTANCE Heartland bandavirus (HRTV) is a tick-borne virus identified in the United States in 2009. HRTV causes fever, fatigue, decreased appetite, headache, nausea, diarrhea, and muscle or joint pain in humans. FDA-approved vaccines and antiviral drugs are unavailable. The lack of a reverse genetics system hampers efforts to develop such antiviral therapeutics. Here, we developed a reverse genetics system for HRTV that led to the generation of a recombinant nonstructural protein (NSs)-knockout HRTV (rHRTV-NSsKO). We found that NSs interrupted signaling associated with innate immunity in HRTV-infected cells. Furthermore, rHRTV-NSsKO was highly attenuated and immunogenic in a mouse model. These findings suggest that NSs is a virulence factor of HRTV and that rHRTV-NSsKO could be a vaccine candidate for HRTV.
Assuntos
Phlebovirus , Genética Reversa , Proteínas não Estruturais Virais , Animais , Antivirais/metabolismo , Artralgia , Bunyaviridae/genética , Bunyaviridae/imunologia , Bunyaviridae/patogenicidade , Diarreia , Fadiga , Cefaleia , Humanos , Imunidade Inata/imunologia , Camundongos , Náusea , Phlebovirus/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/imunologia , Genética Reversa/métodos , Transdução de Sinais/imunologia , Proteínas não Estruturais Virais/genética , Proteínas não Estruturais Virais/imunologia , Virulência/genética , Fatores de Virulência/genéticaRESUMO
Kabuto Mountain virus (KAMV), the new member of the genus Uukuvirus, was isolated from the tick Haemaphysalis flava in 2018 in Japan. To date, there is no information on KAMV infection in human and animals. Therefore, serological surveillance of the infection among humans and wild mammals was conducted by virus-neutralization (VN) test and indirect immunofluorescence assay (IFA). Sera of 24 humans, 59 monkeys, 171 wild boars, 233 Sika deer, 7 bears, and 27 nutria in Yamaguchi Prefecture were analyzed by VN test. The positive ratio of humans, monkeys, wild boars, and Sika deer were 20.8%, 3.4%, 33.9% and 4.7%, respectively. No positive samples were detected in bears and nutria. The correlation coefficients between VN test and IFA in human, monkey, wild boar, and Sika deer sera were 0.5745, 0.7198, 0.9967 and 0.9525, respectively. In addition, KAMV was detected in one pool of Haemaphysalis formosensis ticks in Wakayama Prefecture. These results indicated that KAMV or KAMV-like virus is circulating among many wildlife and ticks, and that this virus incidentally infects humans.
Assuntos
Bunyaviridae/classificação , Carrapatos , Animais , Bunyaviridae/isolamento & purificação , Humanos , Japão , Filogenia , Carrapatos/virologiaRESUMO
A key step during the entry of enveloped viruses into cells is the merger of viral and cell lipid bilayers. This process is driven by a dedicated membrane fusion protein (MFP) present at the virion surface, which undergoes a membrane-fusogenic conformational change triggered by interactions with the target cell. Viral MFPs have been extensively studied structurally, and are divided into three classes depending on their three-dimensional fold. Because MFPs of the same class are found in otherwise unrelated viruses, their intra-class structural homology indicates horizontal gene exchange. We focus this review on the class II fusion machinery, which is composed of two glycoproteins that associate as heterodimers. They fold together in the ER of infected cells such that the MFP adopts a conformation primed to react to specific clues only upon contact with a target cell, avoiding premature fusion in the producer cell. We show that, despite having diverged in their 3D fold during evolution much more than the actual MFP, the class II accompanying proteins (AP) also derive from a distant common ancestor, displaying an invariant core formed by a ß-ribbon and a C-terminal immunoglobulin-like domain playing different functional roles-heterotypic interactions with the MFP, and homotypic AP/AP contacts to form spikes, respectively. Our analysis shows that class II APs are easily identifiable with modern structural prediction algorithms, providing useful information in devising immunogens for vaccine design.
Assuntos
Alphavirus/fisiologia , Bunyaviridae/fisiologia , Genoma Viral/genética , Glicoproteínas/química , Proteínas Virais de Fusão/química , Internalização do Vírus , Alphavirus/genética , Animais , Evolução Biológica , Bunyaviridae/genética , Glicoproteínas/metabolismo , Humanos , Bicamadas Lipídicas/metabolismo , Modelos Estruturais , Multimerização Proteica , Proteínas Virais de Fusão/metabolismo , VírionRESUMO
Barleria cristata L. has become naturalized in South Africa, where it is commonly used as an ornamental. In 2019, plants of B. cristata showing putative viral symptoms were collected from two locations in Gauteng, South Africa. RNAtag-seq libraries were prepared and sequenced using an Illumina HiSeq 2500 platform. De novo assembly of the resulting data revealed the presence of a novel member of the family Tospoviridae associated with the plants from both locations, and this virus was given the tentative name "barleria chlorosis-associated virus". Segments L, M, and S have lengths of 8752, 4760, and 2906 nt, respectively. Additionally, one of the samples was associated with a novel polerovirus, provisionally named "barleria polerovirus 1", with a complete genome length of 6096 nt. This is the first study to show the association of viruses with a member of the genus Barleria.
Assuntos
Bunyaviridae/genética , Bunyaviridae/isolamento & purificação , Genoma Viral , Genômica , Luteoviridae/genética , Luteoviridae/isolamento & purificação , Vírus de Plantas/genética , Vírus de Plantas/isolamento & purificação , Sequência de Aminoácidos , Sequência de Bases , Bunyaviridae/classificação , Luteoviridae/classificação , Fases de Leitura Aberta , Filogenia , Doenças das Plantas/virologia , Vírus de Plantas/classificação , Vírus de RNA/genética , RNA Viral , África do SulRESUMO
Negative-strand (-) RNA viruses (NSVs) comprise a large and diverse group of viruses that are generally divided in those with non-segmented and those with segmented genomes. Whereas most NSVs infect animals and humans, the smaller group of the plant-infecting counterparts is expanding, with many causing devastating diseases worldwide, affecting a large number of major bulk and high-value food crops. In 2018, the taxonomy of segmented NSVs faced a major reorganization with the establishment of the order Bunyavirales. This article overviews the major plant viruses that are part of the order, i.e., orthospoviruses (Tospoviridae), tenuiviruses (Phenuiviridae), and emaraviruses (Fimoviridae), and provides updates on the more recent ongoing research. Features shared with the animal-infecting counterparts are mentioned, however, special attention is given to their adaptation to plant hosts and vector transmission, including intra/intercellular trafficking and viral counter defense to antiviral RNAi.
Assuntos
Bunyaviridae/genética , Doenças das Plantas/virologia , Vírus de Plantas/genética , Bunyaviridae/patogenicidade , Vírus de Plantas/patogenicidade , Plantas/virologia , Vírus de RNA/genética , Vírus de RNA/patogenicidadeRESUMO
The Bunyavirales order comprises more than 500 viruses (generally defined as bunyaviruses) classified into 12 families. Some of these are highly pathogenic viruses infecting different hosts, including humans, mammals, reptiles, arthropods, birds, and/or plants. Host cell sensing of infection activates the innate immune system that aims at inhibiting viral replication and propagation. Upon recognition of pathogen-associated molecular patterns (PAMPs) by cellular pattern recognition receptors (PRRs), numerous signaling cascades are activated, leading to the production of interferons (IFNs). IFNs act in an autocrine and paracrine manner to establish an antiviral state by inducing the expression of hundreds of IFN-stimulated genes (ISGs). Some of these ISGs are known to restrict bunyavirus infection. Along with other constitutively expressed host cellular factors with antiviral activity, these proteins (hereafter referred to as "restriction factors") target different steps of the viral cycle, including viral entry, genome transcription and replication, and virion egress. In reaction to this, bunyaviruses have developed strategies to circumvent this antiviral response, by avoiding cellular recognition of PAMPs, inhibiting IFN production or interfering with the IFN-mediated response. Herein, we review the current knowledge on host cellular factors that were shown to restrict infections by bunyaviruses. Moreover, we focus on the strategies developed by bunyaviruses in order to escape the antiviral state developed by the infected cells.
Assuntos
Infecções por Bunyaviridae/virologia , Bunyaviridae/fisiologia , Interações Hospedeiro-Patógeno , Animais , Biomarcadores , Bunyaviridae/classificação , Infecções por Bunyaviridae/imunologia , Infecções por Bunyaviridae/metabolismo , Genoma Viral , Genômica/métodos , Interações Hospedeiro-Patógeno/genética , Interações Hospedeiro-Patógeno/imunologia , Humanos , Tolerância Imunológica , Imunidade Inata , Interferon Tipo I/metabolismo , Receptores de Reconhecimento de Padrão/metabolismo , Vírion , Replicação ViralRESUMO
We report the complete nucleotide sequence of the genome of a novel virus in ringspot-diseased common oak (Quercus robur L.). The newly identified pathogen is associated with leaf symptoms such as mottle, chlorotic spots and ringspots on diseased trees. High-throughput sequencing (HTS, Illumina RNASeq) was used to explore the virome of a ringspot-diseased oak that had chlorotic ringspots of suspected viral origin on leaves for several years. Bioinformatic analysis of the HTS dataset followed by RT-PCR enabled us to determine complete sequences of four RNA genome segments of a novel virus. These sequences showed high similarity to members of the genus Emaravirus, which includes segmented negative-stranded RNA viruses of economic importance. To verify the ends of each RNA, we conducted rapid amplification of cDNA ends (RACE). We identified an additional genome segment (RNA 5) by RT-PCR using a genus-specific primer (PDAP213) to the conserved 3´ and 5´termini in order to amplify full-length genome segments. RNA 5 encodes a 21-kDa protein that is homologous to the silencing suppressor P8 of High Plains wheat mosaic virus. The five viral RNAs were consistently detected by RT-PCR in ringspot-diseased oaks in Germany, Sweden, and Norway. We conclude that the virus represents a new member of the genus Emaravirus affecting oaks in Germany and in Scandinavia, and we propose the name "common oak ringspot-associated emaravirus" (CORaV).
Assuntos
Bunyaviridae/classificação , Bunyaviridae/genética , Genoma Viral/genética , Vírus de Plantas/genética , Quercus/virologia , Sequência de Aminoácidos , Sequência de Bases , Bunyaviridae/isolamento & purificação , Alemanha , Sequenciamento de Nucleotídeos em Larga Escala , Noruega , Filogenia , Doenças das Plantas/virologia , Folhas de Planta/virologia , Vírus de Plantas/classificação , RNA Viral/genética , Alinhamento de Sequência , SuéciaRESUMO
Many mosquito-borne viruses (arboviruses) are endemic in Africa, contributing to systemic and neurological infections in various geographical locations on the continent. While most arboviral infections do not lead to neuroinvasive diseases of the central nervous system, neurologic diseases caused by arboviruses include flaccid paralysis, meningitis, encephalitis, myelitis, encephalomyelitis, neuritis, and post-infectious autoimmune or memory disorders. Here we review endemic members of the Flaviviridae and Togaviridae families that cause neurologic infections, their neuropathogenesis and host neuroimmunological responses in Africa. We also discuss the potential for neuroimmune responses to aide in the development of new diagnostics and therapeutics, and current knowledge gaps to be addressed by arbovirus research.
Assuntos
Infecções por Arbovirus/imunologia , Arbovírus/imunologia , Sistema Nervoso Central/imunologia , Encefalite por Arbovirus/imunologia , África/epidemiologia , Animais , Infecções por Arbovirus/epidemiologia , Infecções por Arbovirus/virologia , Arbovírus/classificação , Arbovírus/fisiologia , Bunyaviridae/imunologia , Bunyaviridae/fisiologia , Sistema Nervoso Central/virologia , Encefalite por Arbovirus/epidemiologia , Encefalite por Arbovirus/virologia , Epidemias , Flaviviridae/imunologia , Flaviviridae/fisiologia , Humanos , Togaviridae/imunologia , Togaviridae/fisiologiaRESUMO
A significant increase in the number of viruses causing unexpected illnesses and epidemics among humans, wildlife and livestock has been observed in recent years. These new or re-emerging viruses have often caught the scientific community off-guard, without sufficient knowledge to combat them, as shown by the current coronavirus pandemic. The bunyaviruses, together with the flaviviruses and filoviruses, are the major etiological agents of viral hemorrhagic fever, and several of them have been listed as priority pathogens by the World Health Organization for which insufficient countermeasures exist. Based on new techniques allowing rapid analysis of the repertoire of protective antibodies induced during infection, combined with atomic-level structural information on viral surface proteins, structural vaccinology is now instrumental in the combat against newly emerging threats, as it allows rapid rational design of novel vaccine antigens. Here, we discuss the contribution of structural vaccinology and the current challenges that remain in the search for an efficient vaccine against some of the deadliest bunyaviruses.
Assuntos
Infecções por Bunyaviridae/imunologia , Bunyaviridae/imunologia , Vacinologia , Vacinas Virais/imunologia , Antígenos Virais/química , Antígenos Virais/genética , Antígenos Virais/imunologia , Infecções por Bunyaviridae/prevenção & controle , Modelos Moleculares , Pesquisa , Relação Estrutura-Atividade , Vacinologia/métodos , Proteínas Virais/química , Proteínas Virais/genética , Proteínas Virais/imunologiaRESUMO
Ticks are the primary vector of arboviruses in temperate climates worldwide. They are both the vector of these pathogens to humans and an integral component of the viral sylvatic cycle. Understanding the tick-pathogen interaction provides information about the natural maintenance of these pathogens and informs the development of countermeasures against human infection. In this review, we discuss currently available information on tick-viral interactions within the broader scope of general tick immunology. While the tick immune response to several pathogens has been studied extensively, minimal work centres on responses to viral infection. This is largely due to the high pathogenicity of tick-borne viruses; this necessitates high-containment laboratories or low-pathogenicity substitute viruses. This has biased most research towards tick-borne flaviviruses. More work is required to fully understand the role of tick-virus interaction in sylvatic cycling and transmission of diverse tick-borne viruses.
Assuntos
Carrapatos/fisiologia , Fenômenos Fisiológicos Virais/imunologia , Vírus/classificação , Animais , Bunyaviridae/fisiologia , Flaviviridae/fisiologia , Humanos , Imunidade Inata/fisiologia , Orthomyxoviridae/fisiologia , Interferência de RNA/fisiologia , Reoviridae/fisiologia , Carrapatos/genética , Carrapatos/imunologia , Fenômenos Fisiológicos Virais/genéticaRESUMO
Chinese jujube (Ziziphus jujuba Mill.) is a native fruit crop in China. Leaf mottle and dapple fruit disease is prevalent in cultivated jujube plants grown at Aksu in Xinjiang Uygur Autonomous Region of China. Jujube yellow mottle-associated virus (JYMaV), a tentative member in the genus Emaravirus, was recently identified from mottle-diseased jujube plants grown in Liaoning Province in China, but its incidence and genetic diversity in China is unknown. In this study, the genome sequences of three JYMaV isolates from two jujube cultivars and one jujube variant were determined by high-throughput sequencing (HTS) for small RNA and rRNA-depleted RNA coupled with RT-PCR assays. Comparison of these sequences together with sequences of the viral RNA segments derived by primer set 3C/5H-based RT-PCR revealed that genetic diversity was present in the virus populations and high sequence variation occurred at the non-translational regions of each of the viral genomic segments. Field investigation confirmed the close association of the virus with leaf mottle symptoms of jujube plants. Furthermore, this study revealed that P5 encoded in the viral RNA5 displayed a nuclear localization feature differing from the plasmodesma (PD) subcellular localization of the virus movement protein (P4), and the two proteins could interact with each other in the BiFC assays. Our study provides a snapshot of JYMaV genetic diversity in its natural hosts.
Assuntos
Bunyaviridae/classificação , Bunyaviridae/genética , Ziziphus/virologia , Bunyaviridae/isolamento & purificação , Bunyaviridae/ultraestrutura , China , Variação Genética , Genoma Viral , Genômica/métodos , Sequenciamento de Nucleotídeos em Larga Escala , Fases de Leitura Aberta , Fenótipo , Filogenia , Doenças das Plantas/virologia , Folhas de Planta/virologia , Vírus de RNA/genética , RNA Viral , Análise de Sequência de RNARESUMO
Kasokero virus (KASV; genus Orthonairovirus) was first isolated in 1977 at Uganda Virus Research Institute from serum collected from Rousettus aegyptiacus bats captured at Kasokero Cave, Uganda. During virus characterization studies at the institute, 4 laboratory-associated infections resulted in mild to severe disease. Although orthonairoviruses are typically associated with vertebrate and tick hosts, a tick vector of KASV never has been reported. We tested 786 Ornithodoros (Reticulinasus) faini tick pools (3,930 ticks) for KASV. The ticks were collected from a large R. aegyptiacus bat roosting site in western Uganda. We detected KASV RNA in 43 tick pools and recovered 2 infectious isolates, 1 of which was derived from host blood-depleted ticks. Our findings suggest that KASV is maintained in an enzootic transmission cycle involving O. (R.) faini ticks and R. aegyptiacus bats and has the potential for incidental virus spillover to humans.
Assuntos
Bunyaviridae , Quirópteros , Ornithodoros , Vírus , Animais , Humanos , Filogenia , Uganda/epidemiologiaRESUMO
A possible etiological link between the onset of endemic pemphigus in Tunisia and bites of Phlebotomus papatasi, the vector of zoonotic cutaneous leishmaniasis, has been previously suggested. We hypothesized that the immunodominant P. papatasi salivary protein PpSP32 binds to desmogleins 1 and 3 (Dsg1 and Dsg3), triggering loss of tolerance to these pemphigus target autoantigens. Here, we show using far-Western blot that the recombinant PpSP32 protein (rPpSP32) binds to epidermal proteins with a MW of approximately 170 kDa. Coimmunoprecipitation revealed the interaction of rPpSP32 with either Dsg1 or Dsg3. A specific interaction between PpSP32 and Dsg1 and Dsg3 was further demonstrated by ELISA assays. Finally, mice immunized with rPpSP32 twice per week exhibited significantly increased levels of anti-Dsg1 and -Dsg3 antibodies from day 75 to 120. Such antibodies were specific for Dsg1 and Dsg3 and were not the result of cross-reactivity to PpSP32. In this study, we demonstrated for the first time to our knowledge a specific binding between PpSP32 and Dsg1 and Dsg3, which might underlie the triggering of anti-Dsg antibodies in patients exposed to sand fly bites. We also confirmed the development of specific anti-Dsg1 and -Dsg3 antibodies in vivo after PpSP32 immunization in mice. Collectively, our results provide evidence that environmental factors, such as the exposure to P. papatasi bites, can trigger the development of autoimmune antibodies.
Assuntos
Desmogleínas/imunologia , Pênfigo/etiologia , Phlebotomus/imunologia , Adulto , Animais , Autoanticorpos/imunologia , Autoantígenos/imunologia , Bunyaviridae/imunologia , Bunyaviridae/patogenicidade , Infecções por Bunyaviridae/imunologia , Caderinas , Desmogleínas/metabolismo , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Tolerância Imunológica/imunologia , Imunoglobulina G , Masculino , Camundongos , Pênfigo/imunologia , Psychodidae/imunologia , Proteínas Recombinantes , Tunísia/epidemiologiaRESUMO
Several fatal bunyavirus infections lack specific treatment. Here, we show that diketo acids engage a panel of bunyavirus cap-snatching endonucleases, inhibit their catalytic activity and reduce viral replication of a taxonomic representative in vitro. Specifically, the non-salt form of L-742,001 and its derivatives exhibited EC50 values between 5.6 and 6.9 µM against a recombinant BUNV-mCherry virus. Structural analysis and molecular docking simulations identified traits of both the class of chemical entities and the viral target that could help the design of novel, more potent molecules for the development of pan-bunyavirus antivirals.
