Family Peribunyaviridae Research Articles

DdPCR for the Detection and Absolute Quantification of Oropouche Virus.

Oropouche virus (OROV) is a segmented RNA virus belonging to the genus Orthobunyavirus in the family Peribunyaviridae. Herein, an in-house droplet digital PCR (ddPCR) assay was used for the detection and quantification of OROV. The ddPCR reaction was assessed as duplex assay using the human housekeeping gene RPP30. Limit of detection (LoD) analysis was performed in whole blood, serum, and urine. The assay was executed on a total of 28 clinical samples (whole blood n = 9, serum n = 11, and urine n = 8), of which 16 specimens were tested positive at the routine molecular diagnostics (endpoint and real-time PCRs). The LoD of the ddPCR performed using 10-fold serial dilution of OROV detected up to 1 cp/µL in all the biological matrices. Compared to the routine molecular diagnostics, the ddPCR assay showed 100% sensitivity for whole blood and serum and 75% for urine, highlighting higher positive rate of ddPCR. We have established a quantitative RNA detection method of OROV with high sensitivity and specificity based on ddPCR. This test is capable of quantitatively monitoring the viral load of OROV and can contribute, in addition to laboratory diagnosis, to shed light on the pathogenesis, filling in the knowledge gaps of this neglected disease and to the vector control programs.

Rab27a GTPase and its effector Myosin Va are host factors required for efficient Oropouche virus cell egress.

Oropouche fever, a debilitating illness common in South America, is caused by Oropouche virus (OROV), an arbovirus. OROV belongs to the Peribunyaviridae family, a large group of RNA viruses. Little is known about the biology of Peribunyaviridae in host cells, especially assembly and egress processes. Our research reveals that the small GTPase Rab27a mediates intracellular transport of OROV induced compartments and viral release from infected cells. We show that Rab27a interacts with OROV glycoproteins and colocalizes with OROV during late phases of the infection cycle. Moreover, Rab27a activity is required for OROV trafficking to the cell periphery and efficient release of infectious particles. Consistently, depleting Rab27a's downstream effector, Myosin Va, or inhibiting actin polymerization also hinders OROV compartments targeting to the cell periphery and infectious viral particle egress. These data indicate that OROV hijacks Rab27a activity for intracellular transport and cell externalization. Understanding these crucial mechanisms of OROV's replication cycle may offer potential targets for therapeutic interventions and aid in controlling the spread of Oropouche fever.

Characterization of a natural 'dead-end' variant of Schmallenberg virus.

Schmallenberg virus (SBV) belongs to the Simbu serogroup within the family Peribunyaviridae, genus Orthobunyavirus and is transmitted by Culicoides biting midges. Infection of naïve ruminants in a critical phase of gestation may lead to severe congenital malformations. Sequence analysis from viremic animals revealed a very high genome stability. In contrast, sequence variations are frequently described for SBV from malformed fetuses. In addition to S segment mutations, especially within the M segment encoding the major immunogen Gc, point mutations or genomic deletions are also observed. Analysis of the SBV_D281/12 isolate from a malformed fetus revealed multiple point mutations in all three genome segments. It also has a large genomic deletion in the antigenic domain encoded by the M segment compared to the original SBV reference strain 'BH80/11' isolated from viremic blood in 2011. Interestingly, SBV_D281/12 showed a marked replication deficiency in vitro in Culicoides sonorensis cells (KC cells), but not in standard baby hamster kidney cells (BHK-21). We therefore generated a set of chimeric viruses of rSBV_D281/12 and wild-type rSBV_BH80/11 by reverse genetics, which were characterized in both KC and BHK-21 cells. It could be shown that the S segment of SBV_D281/12 is responsible for the replication deficit and that it acts independently from the large deletion within Gc. In addition, a single point mutation at position 111 (S to N) of the nucleoprotein was identified as the critical mutation. Our results suggest that virus variants found in malformed fetuses and carrying characteristic genomic mutations may have a clear 'loss of fitness' for their insect hosts in vitro. It can also be concluded that such mutations lead to virus variants that are no longer part of the natural transmission cycle between mammalian and insect hosts. Interestingly, analysis of a series of SBV sequences confirmed the S111N mutation exclusively in samples of malformed fetuses and not in blood from viremic animals. The characterization of these changes will allow the definition of protein functions that are critical for only one group of hosts.

Replication of Akabane virus and related orthobunyaviruses in a fetal-bovine-brain-derived cell line.

Akabane virus (AKAV), Aino virus, Peaton virus, Sathuperi virus, and Shamonda virus are arthropod-borne viruses belonging to the order Elliovirales, family Peribunyaviridae, genus Orthobunyavirus. These viruses cause or may cause congenital malformations in ruminants, including hydranencephaly, poliomyelitis, and arthrogryposis, although their pathogenicity may vary among field cases. AKAV may cause relatively severe congenital lesions such as hydranencephaly in calves. Furthermore, strains of AKAV genogroups I and II exhibit different disease courses. Genogroup I strains predominantly cause postnatal viral encephalomyelitis, while genogroup II strains are primarily detected in cases of congenital malformation. However, the biological properties of AKAV and other orthobunyaviruses are insufficiently investigated in hosts in the field and in vitro. Here, we used an immortalized bovine brain cell line (FBBC-1) to investigate viral replication efficiency, cytopathogenicity, and host innate immune responses. AKAV genogroup II and Shamonda virus replicated to higher titers in FBBC-1 cells compared with the other viruses, and only AKAV caused cytopathic effects. These results may be associated with the severe congenital lesions in the brain caused by AKAV genogroup II. AKAV genogroup II strains replicated to higher titers in FBBC-1 cells than AKAV genogroup I strains, suggesting that genogroup II strains replicated more efficiently in fetal brain cells, accounting for the detection of the latter strains mainly in fetal infection cases. Therefore, FBBC-1 cells may serve as a valuable tool for investigating the virulence and tropism of the orthobunyaviruses for bovine neonatal brain tissues in vitro.

Evaluating the mosquito vector range for two orthobunyaviruses: Oya virus and Ebinur Lake virus

BackgroundMosquito-borne viruses cause various infectious diseases in humans and animals. Oya virus (OYAV) and Ebinur Lake virus (EBIV), belonging to the genus Orthobunyavirus within the family Peribunyaviridae, are recognized as neglected viruses with the potential to pose threats to animal or public health. The evaluation of vector competence is essential for predicting the arbovirus transmission risk.MethodsTo investigate the range of mosquito vectors for OYAV (strain SZC50) and EBIV (strain Cu20-XJ), the susceptibility of four mosquito species (Culex pipiens pallens, Cx. quinquefasciatus, Aedes albopictus, and Ae. aegypti) was measured through artificial oral infection. Then, mosquito species with a high infection rate (IR) were chosen to further evaluate the dissemination rate (DR), transmission rate (TR), and transmission efficiency. The viral RNA in each mosquito sample was determined by RT-qPCR.ResultsThe results revealed that for OYAV, Cx. pipiens pallens had the highest IR (up to 40.0%) among the four species, but the DR and TR were 4.8% and 0.0%, respectively. For EBIV, Cx. pipiens pallens and Cx. quinquefasciatus had higher IR compared to Ae. albopictus (1.7%). However, the EBIV RNA and infectious virus were detected in Cx. pipiens pallens, with a TR of up to 15.4% and a transmission efficiency of 3.3%.ConclusionsThe findings indicate that Cx. pipiens pallens was susceptible to OYAV but had an extremely low risk of transmitting the virus. Culex pipiens pallens and Cx. quinquefasciatus were susceptible to EBIV, and Cx. pipiens pallens had a higher transmission risk to EBIV than Cx. quinquefasciatus.Graphical

Favipiravir Treatment Prolongs Survival in a Lethal BALB/c Mouse Model of Ebinur Lake Virus Infection.

Orthobunyavirus is the largest and most diverse genus in the family Peribunyaviridae. Orthobunyaviruses are widely distributed globally and pose threats to human and animal health. Ebinur Lake virus (EBIV) is a newly classified Orthobunyavirus detected in China, Russia, and Kenya. This study explored the antiviral effects of two broad-spectrum antiviral drugs, favipiravir and ribavirin, in a BALB/c mouse model. Favipiravir significantly improved the clinical symptoms of infected mice, reduced viral titer and RNA copies in serum, and extended overall survival. The median survival times of mice in the vehicle- and favipiravir-treated groups were 5 and 7 days, respectively. Favipiravir significantly reduced virus titers 10- to 100-fold in sera at all three time points compared to vehicle-treated mice. And favipiravir treatment effectively reduced the virus copies by approximately 10-fold across the three time points, relative to vehicle-treated mice. The findings expand the antiviral spectrum of favipiravir for orthobunyaviruses in vivo.

Isolation and whole-genome sequence analysis of Balagodu virus in Japan.

Whole-genome sequencing of a virus isolated from Culicoides biting midges in southern Japan in 2020 revealed that it is a strain of Balagodu virus (BLGV; genus Orthobunyavirus; family Peribunyaviridae; order Bunyavirales). A solitary instance of BLGV isolation occurred in India in 1963. All assembled segments comprise complete protein-coding sequences that are similar to those of other orthobunyaviruses. The consensus 3'- and 5'-terminal sequences of orthobunyaviruses' genomic RNAs are also conserved in the Japanese BLGV strain. Here, we update the geographic distribution of BLGV and provide its complete sequence, contributing to the clarification of orthobunyavirus phylogeny.

Revisiting the Importance of Orthobunyaviruses for Animal Health: A Scoping Review of Livestock Disease, Diagnostic Tests, and Surveillance Strategies for the Simbu Serogroup.

Orthobunyaviruses (order Bunyavirales, family Peribunyaviridae) in the Simbu serogroup have been responsible for widespread epidemics of congenital disease in ruminants. Australia has a national program to monitor arboviruses of veterinary importance. While monitoring for Akabane virus, a novel orthobunyavirus was detected. To inform the priority that should be given to this detection, a scoping review was undertaken to (1) characterise the associated disease presentations and establish which of the Simbu group viruses are of veterinary importance; (2) examine the diagnostic assays that have undergone development and validation for this group of viruses; and (3) describe the methods used to monitor the distribution of these viruses. Two search strategies identified 224 peer-reviewed publications for 33 viruses in the serogroup. Viruses in this group may cause severe animal health impacts, but only those phylogenetically arranged in clade B are associated with animal disease. Six viruses (Akabane, Schmallenberg, Aino, Shuni, Peaton, and Shamonda) were associated with congenital malformations, neurological signs, and reproductive disease. Diagnostic test interpretation is complicated by cross-reactivity, the timing of foetal immunocompetence, and sample type. Serological testing in surveys remains a mainstay of the methods used to monitor the distribution of SGVs. Given significant differences in survey designs, only broad mean seroprevalence estimates could be provided. Further research is required to determine the disease risk posed by novel orthobunyaviruses and how they could challenge current diagnostic and surveillance capabilities.

The search for an antiviral lead molecule to combat the neglected emerging Oropouche virus

Oropouche virus (OROV) is a member of the Peribunyaviridae family and the causative agent of a dengue-like febrile illness transmitted by mosquitoes. Although mild symptoms generally occur, complications such as encephalitis and meningitis may develop. A lack of proper diagnosis, makes it a potential candidate for new epidemics and outbreaks like other known arboviruses such as Dengue, Yellow Fever and Zika virus. The study of natural molecules as potential antiviral compounds is a promising alternative for antiviral therapies. Wedelolactone (WDL) has been demonstrated to inhibit some viral proteins and virus replication, making it useful to target a wide range of viruses. In this study, we report the in silico effects of WDL on the OROV N-terminal polymerase and its potential inhibitory effects on several steps of viral infection in mammalian cells in vitro, which revealed that WDL indeed acts as a potential inhibitor molecule against OROV infection.

Metatranscriptomics Reveals the RNA Virome of Ixodes Persulcatus in the China-North Korea Border, 2017.

In recent years, numerous viruses have been identified from ticks, and some have been linked to clinical cases of emerging tick-borne diseases. Chinese northeast frontier is tick infested. However, there is a notable lack of systematic monitoring efforts to assess the viral composition in the area, leaving the ecological landscape of viruses carried by ticks not clear enough. Between April and June 2017, 7101 ticks were collected to perform virus surveillance on the China-North Korea border, specifically in Tonghua, Baishan, and Yanbian. A total of 2127 Ixodes persulcatus were identified. Further investigation revealed the diversity of tick-borne viruses by transcriptome sequencing of Ixodes persulcatus. All ticks tested negative for tick-borne encephalitis virus. Transcriptome sequencing expanded 121 genomic sequence data of 12 different virus species from Ixodes persulcatus. Notably, a new segmented flavivirus, named Baishan Forest Tick Virus, were identified, closely related to Alongshan virus and Harz mountain virus. Therefore, this new virus may pose a potential threat to humans. Furthermore, the study revealed the existence of seven emerging tick-borne viruses dating back to 2017. These previously identified viruses included Mudanjiang phlebovirus, Onega tick phlebovirus, Sara tick phlebovirus, Yichun mivirus, and three unnamed viruses (one belonging to the Peribunyaviridae family and the other two belonging to the Phenuiviridae family). The existence of these emerging tick-borne viruses in tick samples collected in 2017 suggests that their history may extend further than previously recognized. This study provides invaluable insights into the virome of Ixodes persulcatus in the China-North Korea border region, enhancing our ongoing efforts to manage the risks associated with tick-borne viruses.

Antiviral Activity and Molecular Dynamics Simulation of Hops Compounds against Oropouche Virus (Peribunyaviridae).

The Oropouche virus (OROV) is a member of the family Peribunyaviridae (order Bunyavirales) and the cause of a dengue-like febrile illness transmitted mainly by biting midges and mosquitoes. In this study, we aimed to explore acylphloroglucinols and xanthohumol from hops (Humulus lupulus L.) as a promising alternative for antiviral therapies. The evaluation of the inhibitory potential of hops compounds on the viral cycle of OROV was performed through two complementary approaches. The first approach applies cell-based assay post-inoculation experiments to explore the inhibitory potential on the latest steps of the viral cycle, such as genome translation, replication, virion assembly, and virion release from the cells. The second part covers in silico methods evaluating the ability of those compounds to inhibit the activity of the endonuclease domain, which is essential for transcription, binding, and cleaving RNA. In conclusion, the beta acids showed strongest inhibitory potential in post-treatment assay (EC50 = 26.7 µg/mL). Xanthohumol had the highest affinity for OROV endonuclease followed by colupulone and cohumulone. This result contrasts with that observed for docking and MM/PBSA analysis, where cohumulone was found to have a higher affinity. Finally, among the three tested ligands, Lys92 and Arg33 exhibited the highest affinity with the protein.

Differential role of NSs genes in the neurovirulence of two genogroups of Akabane virus causing postnatal encephalomyelitis.

Akabane virus (AKAV) is a member of the genus Orthobunyavirus, family Peribunyaviridae. In addition to AKAV strains that cause fetal Akabane disease, which is characterized by abortion in ruminants, some AKAV strains cause postnatal infection characterized by nonsuppurative encephalomyelitis in ruminants. Here, we focused on the NSs protein, a virulence factor for most viruses belonging to the genus Orthobunyavirus, and we hypothesized that this protein would act as a neurovirulence factor in AKAV strains causing postnatal encephalomyelitis. We generated AKAV strains that were unable to produce the NSs protein, derived from two different genogroups, genogroups I and II, and then examined the role of their NSs proteins by inoculating mice intracerebrally with these modified viruses. Our results revealed that the neurovirulence of genogroup II strains is dependent on the NSs protein, whereas that of genogroup I strains is independent of this protein. Notably, infection of primary cultured bovine cells with these viruses suggested that the NSs proteins of both genogroups suppress innate immune-related gene expression with equal efficiency. These results indicate differences in the determinants of virulence of orthobunyaviruses.

Development and evaluation of RT-qPCR assays for two neglected orthobunyaviruses: Oya virus and Ebinur Lake virus

ObjectivesOya virus (OYAV) and Ebinur lake virus (EBIV) belong to the genus Orthobunyavirus within the Peribunyaviridae family, and both are recognized as the novel virus with potential threat to the animal or public health. Given their potential to cause outbreaks and their detection in diverse samples across different regions, the need for a reliable and efficient molecular detection method for OYAV and EBIV becomes imperative. MethodsThe S-segment of OYAV and EBIV was used for designing specific primer and probe sets, which were employed in a real-time reverse transcription quantitative PCR (RT-qPCR) assay. The analytical performance of these assays, encompassing specificity, sensitivity, reproducibility, and fitness for purpose, was thoroughly evaluated across various sample matrices. ResultsThe developed RT-qPCR assays were very specific to their respective targets. Both assays were highly reproducible (%CV<3) and sensitive with the 95% limit of detection (LOD) of 0.80 PFU/mL for OYAV primer probe set and 0.37 PFU/mL for EBIV primer probe set. Furthermore, the assays fitness for purpose was good as it could detect the specific viruses in virus-spiked serum samples, virus-inoculated mosquito samples, field caught mosquitoes and biting midge samples. ConclusionsOur study has successfully developed specific, sensitive, and reliable RT-qPCR assays for the detection of OYAV and EBIV. These assays hold great promise for their potential application in clinical and field samples in the future.

Snowshoe hare virus: discovery, distribution, vector and host associations, and medical significance.

Snowshoe hare virus (SSHV), within the California serogroup of the genus Orthobunyavirus, family Peribunyaviridae, was first isolated from a snowshoe hare (Lepus americanus) in Montana, United States, in 1959. The virus, closely related to LaCrosse virus (LACV) and Chatanga virus (CHATV), occurs across Canada and the northern latitudes of the United States, primarily in the northern tier of states bordering Canada. Reports of SSHV in northern Europe and Asia are probably the closely related to CHATV, or the less closely related Tahyna virus. Vertebrate associations include snowshoe hares and ground squirrels, demonstrated by field isolation of virus from wild-caught animals, seroconversion of snowshoe hares, seroconversion of sentinel rabbits, isolation of virus from sentinel rabbits, and experimental infections demonstrating viremia. Isolations of virus from field populations of mosquitoes include primarily univoltine and boreal mosquitoes of the genus Aedes, Culiseta impatiens and Culiseta inornata; and, rarely, certain multivoltine floodwater Aedes species. Experimental transmission studies in mosquitoes show infection in and transmission by boreal Aedes and Culiseta inornata. Isolation of SSHV from larval Aedes on three occasions, and experimentation in Culiseta inornata, reveal transovarial transmission of the virus in mosquitoes. Serosurveys reveal exposure to SSHV in human and domestic animals, with rates of seropositivity commonly high in some settings in Alaska and Canada, but disease in humans or horses has rarely been reported, only in Canada.

Identification and Molecular Characterization of Shamonda Virus in an Aborted Goat Fetus in South Africa.

Viruses in the Orthobunyavirus genus, Peribunyaviridae family, are associated with encephalitis, birth defects and fatalities in animals, and some are zoonotic. Molecular diagnostic investigations of animals with neurological signs previously identified Shuni virus (SHUV) as the most significant orthobunyavirus in South Africa (SA). To determine if other orthobunyaviruses occur in SA, we screened clinical specimens from animals with neurological signs, abortions, and acute deaths from across SA in 2021 using a small (S) segment Simbu serogroup specific TaqMan real-time reverse transcription polymerase chain reaction (RT-PCR). Positive cases were subjected to Sanger sequencing and phylogenetic analysis to identify specific viruses involved, followed by next-generation sequencing (NGS) and additional PCR assays targeting the medium (M) segment and the large (L) segment. In total, 3/172 (1.7%) animals were PCR positive for Simbu serogroup viruses, including two horses with neurological signs and one aborted goat fetus in 2021. Phylogenetic analyses confirmed that the two horses were infected with SHUV strains with nucleotide pairwise (p-) distances of 98.1% and 97.6% to previously identified strains, while the aborted goat fetus was infected with a virus closely related to Shamonda virus (SHAV) with nucleotide p-distances between 94.7% and 91.8%. Virus isolation was unsuccessful, likely due to low levels of infectious particles. However, phylogenetic analyses of a larger fragment of the S segment obtained through NGS and partial sequences of the M and L segments obtained through RT-PCR and Sanger sequencing confirmed that the virus is likely SHAV with nucleotide p-distances between 96.6% and 97.8%. This is the first detection of SHAV in an aborted animal in SA and suggests that SHAV should be considered in differential diagnosis for abortion in animals in Southern Africa.

The First Serological Detection and Risk Factors Analysis of Akabane Virus in Egyptian Cattle.

Akabane virus (AKAV) is an insect-borne virus belonging to the genus Orthobunyavirus of the family Peribunyaviridae. It is the etiologic agent of Akabane disease (AD), which emerged in Asia, Australia, and the Middle East causing severe economic losses among domestic and wild animals. AKAV has not received enough attention in Egypt, and its evidence among Egyptian animals has never been reported. Therefore, this study used ELISA assay to investigate the seroprevalence of AKAV among Egyptian dairy and beef cattle in eight localities of Beheira province, north Egypt. Out of 368 investigated plasma samples, the overall AKAV seroprevalence was 54.3% (95% CI: 50.8-61.4). AKAV antibodies were detected in all examined cattle farms (7/7) and the majority of abattoirs (8/9). Age, sex, breed, and location of the tested cattle were analyzed as risk factors for AKAV infection. A higher significant increase in seropositivity was obtained in cattle who were aged >5 years (p < 0.0001; OR = 9.4), females (p < 0.0001, OR = 8.3), or Holstein breed (p < 0.0001, OR = 22.6) than in younger ages, males, and Mixed and Colombian zebu breeds, respectively. Moreover, a significant variation in AKAV seroprevalence between the tested locations was noticed. Ultimately, a multivariable analysis concluded that age (p = 0.002, OR = 3.32, 95% CI = 1.57-7.04) and breed (p = 0.03, OR = 1.69, 95% CI = 1.05-2.72) were significant risks for AKAV infection. In conclusion, this study is the first to detect AKAV infection in Egyptian animals.

Immunization with a small fragment of the Schmallenberg virus nucleoprotein highly conserved across the Orthobunyaviruses of the Simbu serogroup reduces viremia in SBV challenged IFNAR-/- mice.

Schmallenberg Virus (SBV), an arbovirus from the Peribunyaviridae family and Orthobunyavirus genus, was discovered in late 2011 in Germany and has been circulating in Europe, Asia and Africa ever since. The virus causes a disease associated with ruminants that includes fever, fetal malformation, drop in milk production, diarrhoea and stillbirths, becoming a burden for small and large farms. Building on previous studies on SBV nucleoprotein (SBV-N) as a promising vaccine candidate, we have investigated the possible protein regions responsible for protection. Based on selective truncation of domains designed from the available crystal structure of the SBV-N, we identified both the N-terminal domain (N-term; Met1 - Thr133) and a smaller fragment within (C4; Met1 - Ala58) as vaccine prototypes. Two injections of the N-term and C4 polypeptides protected mice knockout for type I interferon (IFN) receptors (IFNAR-/-) challenged with virulent SBV, opposite to control groups that presented severe signs of morbidity and weight loss. Viremia analyses along with the presence of IFN-γ secreted from splenocytes re-stimulated with the N-terminal region of the protein corroborate that these two portions of SBV-N can be employed as subunit vaccines. Apart from both proteinaceous fragments being easily produced in bacterial cells, the C4 polypeptide shares a high sequence homology (∼87.1 %) with the corresponding region of nucleoproteins of several viruses of the Simbu serogroup, a group of Orthobunyaviruses that comprises SBV and veterinary pathogens like Akabane virus and human infecting viruses like Oropouche. Thus, we propose that this smaller fragment is better suited for vaccine nanoparticle formulation, and it paves the way to further research with other related Orthobunyaviruses.

Anti-Schmallenberg Virus Activities of Type I/III Interferons-Induced Mx1 GTPases from Different Mammalian Species.

Mx proteins are key factors of the innate intracellular defense mechanisms that act against viruses induced by type I/III interferons. The family Peribunyaviridae includes many viruses of veterinary importance, either because infection results in clinical disease or because animals serve as reservoirs for arthropod vectors. According to the evolutionary arms race hypothesis, evolutionary pressures should have led to the selection of the most appropriate Mx1 antiviral isoforms to resist these infections. Although human, mouse, bat, rat, and cotton rat Mx isoforms have been shown to inhibit different members of the Peribunyaviridae, the possible antiviral function of the Mx isoforms from domestic animals against bunyaviral infections has, to our knowledge, never been studied. Herein, we investigated the anti-Schmallenberg virus activity of bovine, canine, equine, and porcine Mx1 proteins. We concluded that Mx1 has a strong, dose-dependent anti-Schmallenberg activity in these four mammalian species.

RNA Encapsulation Mode and Evolutionary Insights from the Crystal Structure of Emaravirus Nucleoprotein.

Enveloped RNA viruses are rare among plant viruses. Fimoviridae is a newly founded family of plant viruses within the Bunyavirales order that inflicts diverse crop losses worldwide. The fig mosaic virus (FMV), the representative member of the Fimoviridae family, was shown to be a causative agent for the fig mosaic disease. Like all bunyaviruses, FMV has a segmented, negative-sense, single-stranded RNA (ssRNA) genome that is encapsulated by the viral nucleoprotein (N). Here, we present high-resolution crystal structures of FMV N in its RNA-free and RNA-bound forms, revealing a "paper fortune teller" structural transition between the two states. The tightly packed tetramer of FNV N is similar to the structures of other N proteins of different members of the Bunyavirales order. In its RNA-bound form, the tetramer reorganizes to adopt a more open state that allows the accommodation of the RNA. Despite the low sequence similarity to N proteins of animal-infecting bunyaviruses, there is a striking structural resemblance between FMV N and nucleoproteins from members of the Peribunyaviridae, an animal-infecting family of viruses. This structural homology implies that enveloped plant viruses and animal-infecting viruses might have a common ancestor from which they diverged. IMPORTANCE Most insect-born viruses circulate within the Animalia kingdom, whereas plant-infecting RNA viruses are cross-kingdom pathogens. Many plant-infecting viruses cause devastating crop damage that leads to food security endangerment. The evolutionary crossroads of interkingdom circulation and infection are poorly understood. Thus, we took the structural approach to understand the similarities and differences between interkingdom-infecting viruses and viruses that circulate within one kingdom of life. Using our structures of FMV N in its free form and in complex with a single-stranded RNA (ssRNA), we dissected the mechanism by which FMV N binds to the RNA and revealed the conformational changes associated with the binding. The resemblance of our structure to N proteins from members of the Peribunyaviridae family and their recently published ribonucleoprotein (RNP) pseudoatomic resolution assembly model suggests that the FMV genome is similarly encapsulated. Thus, our finding unveils yet another bridge by which plant- and animal-infecting viruses are interconnected.

Whole Genome Sequencing Analysis of African Orthobunyavirus Isolates Reveals Naturally Interspecies Segments Recombinations between Bunyamwera and Ngari Viruses.

Bunyamwera virus is the prototype of the Bunyamwera serogroup, which belongs to the order Bunyavirales of the Orthobunyavirus genus in the Peribunyaviridae family. Bunyamwera is a negative-sense RNA virus composed of three segments S, M, and L. Genetic recombination is possible between members of this order as it is already documented. Additionally, it can lead to pathogenic or host range improvement, if it occurs with viruses of public health and agricultural importance such as Rift Valley fever virus and Crimea-Congo hemorrhagic fever virus. Here, we characterize five African Orthobunyavirus viruses from different geographical regions. Our results suggest that the five newly characterized strains are identified as Bunyamwera virus strains. Furthermore, two of the five strains sequenced in this study are recombinant strains, as fragments of their segments are carried by Ngari and Bunyamwera strains. Further investigations are needed to understand the functional impact of these recombinations.