Complete sequence determination and genetic analysis of Banna virus and Kadipiro virus: proposal for assignment to a new genus (Seadornavirus) within the family Reoviridae

Cryo-EM structures of Banna virus in multiple states reveal stepwise detachment of viral spikes

Banna virus (BAV) is the prototype Seadornavirus, a class of reoviruses for which there has been little structural study. Here, we report atomic cryo-EM structures of three states of BAV virions-surrounded by 120 spikes (full virions), 60 spikes (partial virions), or no spikes (cores). BAV cores are double-layered particles similar to the cores of other non-turreted reoviruses, except for an additional protein component in the outer capsid shell, VP10. VP10 was identified to be a cementing protein that plays a pivotal role in the assembly of BAV virions by directly interacting with VP2 (inner capsid), VP8 (outer capsid), and VP4 (spike). Viral spikes (VP4/VP9 heterohexamers) are situated on top of VP10 molecules in full or partial virions. Asymmetrical electrostatic interactions between VP10 monomers and VP4 trimers are disrupted by high pH treatment, which is thus a simple way to produce BAV cores. Low pH treatment of BAV virions removes only the flexible receptor binding protein VP9 and triggers significant conformational changes in the membrane penetration protein VP4. BAV virions adopt distinct spatial organization of their surface proteins compared with other well-studied reoviruses, suggesting that BAV may have a unique mechanism of penetration of cellular endomembranes.

Full genome characterization and evolutionary analysis of Banna virus isolated from Culicoides, mosquitoes and ticks in Yunnan, China

Introduction

Banna virus (BAV), a potential pathogen that may cause human encephalitis, is the prototype species of genus Seadornaviru within the family Reoviridae, and has been isolated from a variety of blood-sucking insects and mammals in Asia.

Methods

Culicoides, Mosquitoes, and Ticks were collected overnight in Yunnan, China, during 2016-2023 using light traps. Virus was isolated from these collected blood-sucking insects and grown using Aedes albopictus (C6/36) cells. Preliminary identification of the virus was performed by agarose gel electrophoresis (AGE). The full genome sequences of the BAVs were determined by full-length amplification of cDNAs (FLAC) and sequenced using next-generation sequencing.

Results

In this study, 13 strains BAV were isolated from Culicoides, Mosquitoes and Ticks. Their viral genome consisted of 12 segments of double-stranded RNA (dsRNA), and with three distinct distribution patterns. Sequence analysis showed that Seg-5 of four strains (SJ_M46, SJ_M49, JC_M19-13 and JC_C24-13) has 435 bases nucleotide sequence insertions in their ORF compared to other BAVs, resulting in the length of Seg-5 up to 2128 nt. There are 34 bases sequence deletion in Seg-9 of 3 strains (WS_T06, MS_M166 and MS_M140). Comparison of the coding sequences of VP1, VP2, VP5, VP9 and VP12 of the 13 BAV strains, the results show that VP1, VP2 and VP12 are characterised by high levels of sequence conservation, while VP9 is highly variable, under great pressure to adapt and may be correlated with serotype. While also variable, VP5 appears to be under less adaptive pressure than VP9. Additionally, phylogenetic analysis indicates that the 13 BAV strains locate in the same evolutionary cluster as BAVs isolated from various blood-sucking insects, and are clustered according to geographical distribution.

Conclusion

The data obtained herein would be beneficial for the surveillance of evolutionary characteristics of BAV in China and neighboring countries as well as extend the knowledge about its genomic diversity and geographic distribution.

Nonenveloped Avian Reoviruses Released with Small Extracellular Vesicles Are Highly Infectious

Vesicle-encapsulated nonenveloped viruses are a recently recognized alternate form of nonenveloped viruses that can avoid immune detection and potentially increase systemic transmission. Avian orthoreoviruses (ARVs) are the leading cause of various disease conditions among birds and poultry. However, whether ARVs use cellular vesicle trafficking routes for egress and cell-to-cell transmission is still poorly understood. We demonstrated that fusogenic ARV-infected quail cells generated small (~100 nm diameter) extracellular vesicles (EVs) that contained electron-dense material when observed by transmission electron microscope. Cryo-EM tomography indicated that these vesicles did not contain ARV virions or core particles, but the EV fractions of OptiPrep gradients did contain a small percent of the ARV virions released from cells. Western blotting of detergent-treated EVs revealed that soluble virus proteins and the fusogenic p10 FAST protein were contained within the EVs. Notably, virus particles mixed with the EVs were up to 50 times more infectious than virions alone. These results suggest that EVs and perhaps fusogenic FAST-EVs could contribute to ARV virulence.

An atlas of the blood virome in healthy individuals

Emerging evidence indicates that gut virome plays a role in human health and disease, however, much less is known about the viral communities in blood. Here we conducted a direct metatranscriptomic sequencing of virus-like-particles in blood from 1200 healthy individuals, without prior amplification to avoid potential amplification bias and with a strictly bioinformatic and manual check for candidate viral reads to reduce false-positive matches. We identified 55 different viruses from 36 viral families, including 24 human DNA, RNA and retroviruses in 70% of the studied pools. The study showed that anelloviruses are widely distributed and dominate the blood virome in healthy individuals. Human herpesviruses and pegivirus-1 are commonly prevalent in asymptomatic humans. We identified the prevalence of RNA viruses often causing acute infection, like HEV, HPIV, RSV and HCoV-HKU1, revealing of a transmissible risk of asymptomatic infection. Several viruses possible related to transfusion safety were identified, including human Merkel cell polyomavirus, papillomavirus, parvovirus B19 and herpesvirus 8 in addition to HBV. In addition, phages in Caudovirales and Microviridae, were commonly found in pools of samples with a very low abundance; a few sequences for invertebrate, plant and giant viruses were found in some of individuals; however, the remaining 31 viruses mostly reflect extensive contamination from commercial reagents and the work environments. In conclusion, this study is the first comprehensive investigation of blood virome in healthy individuals by metatranscriptomic sequencing of VLP in China. Further investigation of potential false positives representing a major challenge for the identification of novel viruses in mNGS, will offer a systemic idea and means to reveal true viral infections of human.

Avian Reovirus σB Interacts with Caveolin-1 in Lipid Rafts during Dynamin-Dependent Caveolae-Mediated Endocytosis

Caveolin-1 (Cav-1) is the basic component of caveolae, a specialized form of lipid raft that plays an essential role in endocytic viral entry. However, the evidence of direct involvement of caveolae and Cav-1 in avian reovirus (ARV) entry remains insufficient. In this study, the membrane lipid rafts were isolated as detergent-resistant microdomains (DRMs) by sucrose gradient centrifugation, and the capsid protein σB of ARV was found to associate with Cav-1 in DRMs fractions. Additionally, the interaction between ARV σB protein and Cav-1 was demonstrated by immunofluorescence co-localization and co-immunoprecipitation assays. Furthermore, we found that the internalization of ARV is sensitive to caveolae and dynamin inhibitors, while it is insensitive to clathrin inhibitors. In conclusion, these results indicate that the ARV σB protein interacts with Cav-1 during dynamin-dependent caveolae-mediated endocytosis for the entry of ARV.

Full Genome Sequencing of Three Sedoreoviridae Viruses Isolated from Culicoides spp. (Diptera, Ceratopogonidae) in China

Sedoreoviridae is a family of viruses belonging to the order Reovirales and comprises six genera, two of which, Orbivirus and Seadornavirus, contain arboviruses that cause disease in humans and livestock. Areas such as Yunnan Province in southwestern China, have high arboviral activity due in part to warm and wet summers, which support high populations of biting flies such as mosquitoes and Culicoides. Three viral isolates previously obtained from Culicoides collected at cattle farms in Shizong County of Yunnan Province, China, between 2019 and 2020 were completely sequenced and identified as Banna virus (BAV) genotype A of Seadornavirus and serotypes 1 and 7 of epizootic hemorrhagic disease virus (EHDV) of Orbivirus. These results suggest that Culicoidestainanus and C. orientalis are potential vectors of BAV and EHDV, respectively, and represent the first association of a BAV with C. tainanus and of an arbovirus with C. orientalis. Analysis using VP9 generally agreed with the current groupings within this genus based on VP12, although the classification for some strains should be corrected. Furthermore, the placement of Kadipiro virus (KDV) and Liao ning virus (LNV) in Seadornavirus may need confirmation as phylogenetic analysis placed these viruses as sister to other species in the genus.

Genomic Evaluation of the Genus Coltivirus Indicates Genetic Diversity among Colorado Tick Fever Virus Strains and Demarcation of a New Species

The type species of the genus Coltivirus, Colorado tick fever virus (CTFV), was discovered in 1943 and is the most common tick-borne viral infection in the Western US. Despite its long history, very little is known about the molecular diversity of viruses classified within the species Colorado tick fever coltivirus. Previous studies have suggested genetic variants and potential serotypes of CTFV, but limited genetic sequence information is available for CTFV strains. To address this knowledge gap, we report herein the full-length genomes of five strains of CTFV, including Salmon River virus and California hare coltivirus (CTFV-Ca). The sequence from the full-length genome of Salmon River virus identified a high genetic identity to the CTFV prototype strain with >90% amino acid identity in all the segments except segment four, suggesting Salmon River virus is a strain of the species Colorado tick fever coltivirus. Additionally, analysis suggests that segment four has been associated with reassortment in at least one strain. The CTFV-Ca full-length genomic sequence was highly variable from the prototype CTFV in all the segments. The genome of CTFV-Ca was most similar to the Eyach virus, including similar segments six and seven. These data suggest that CTFV-Ca is not a strain of CTFV but a unique species. Additional sequence information of CTFV strains will improve the molecular surveillance tools and provide additional taxonomic resolution to this understudied virus.

Full-Genome Sequences of Alphacoronaviruses and Astroviruses from Myotis and Pipistrelle Bats in Denmark

Bat species worldwide are receiving increased attention for the discovery of emerging viruses, cross-species transmission, and zoonoses, as well as for characterizing virus infections specific to bats. In a previous study, we investigated the presence of coronaviruses in faecal samples from bats at different locations in Denmark, and made phylogenies based on short, partial ORF1b sequences. In this study, selected samples containing bat coronaviruses from three different bat species were analysed, using a non-targeted approach of next-generation sequencing. From the resulting metagenomics data, we assembled full-genome sequences of seven distinct alphacoronaviruses, three astroviruses, and a polyomavirus, as well as partial genome sequences of rotavirus H and caliciviruses, from the different bat species. Comparisons to published sequences indicate that the bat alphacoronaviruses belong to three different subgenera-i.e., Pedacovirus, Nyctacovirus, and Myotacovirus-that the astroviruses may be new species in the genus Mamastrovirus, and that the polyomavirus could also be a new species, but unassigned to a genus. Furthermore, several viruses of invertebrates-including two Rhopalosiphum padi (aphid) viruses and a Kadipiro virus-present in the faecal material were assembled. Interestingly, this is the first detection in Europe of a Kadipiro virus.

Origin and evolution of emerging Liao ning Virus (genus Seadornavirus, family Reoviridae)

Background

Liao ning virus (LNV) is a member of the genus Seadornavirus, family Reoviridae and has been isolated from kinds of vectors in Asia and Australia. However, there are no systematic studies describe the molecular genetic evolution and migration of LNVs. With the development of bioinformatics, viral genetic data combining the information of virus isolation time and locations could be integrated to infer the virus evolution and spread in nature.

Methods

Here, a phylogenetic and phylogeographic analysis using Bayesian Markov chain Monte Carlo simulations was conducted on the LNVs isolated from a variety of vectors during 1990–2014 to identify the evolution and migration patterns of LNVs.

Results

The results demonstrated that the LNV could be divided into 3 genotypes, of which genotype 1 mainly composed of LNVs isolated from Australia during 1990 to 2014 and the original LNV strain (LNV-NE97–31) isolated from Liaoning province in northern China in 1997, genotype 2 comprised of the isolates all from Xinjiang province in western China and genotype 3 consisted the isolates from Qinghai and Shanxi province of central China. LNVs emerged about 272 years ago and gradually evolved into three lineages in the order genotype 1, genotype 2 and genotype 3. Following phylogeographic analysis, it shows genotype 1 LNVs transmitted from Australia (113°E-153°E,10°S-42°S) to Liaoning province (118°E-125°E,38°N-43°N) in Northeast Asian continent then further spread across the central part of China to western China (75°E-95°E,35°N-50°N).

Conclusion

LNVs were initially isolated from Liaoning province of China in the Northeast Asia, however, the present study revealed that LNVs were first appeared in Australia in the South Pacific region and transmitted to mainland China then rapidly spread across China and evolved three different genotypes. The above results suggested that LNV had the characteristics of long-distance transmission and there were great genetic diversity existed in the LNV population. Notably, current information of 80 strains of LNVs are limited. It is of great importance to strengthen the surveillance of LNVs to explore its real origin in nature and monitoring of the LNVs’ population variation and maintain vigilance to avoid LNV breaking through the species barrier and further clarify its relationship to human and animal infection.

Mosquito-borne viruses, insect-specific flaviviruses (family Flaviviridae, genus Flavivirus), Banna virus (family Reoviridae, genus Seadornavirus), Bogor virus (unassigned member of family Permutotetraviridae), and alphamesoniviruses 2 and 3 (family Mesoniviridae, genus Alphamesonivirus) isolated from Indonesian mosquitoes

Mosquitoes transmit many kinds of arboviruses (arthropod-borne viruses), and numerous arboviral diseases have become serious problems in Indonesia. In this study, we conducted surveillance of mosquito-borne viruses at several sites in Indonesia during 2016-2018 for risk assessment of arbovirus infection and analysis of virus biodiversity in mosquito populations. We collected 10,015 mosquitoes comprising at least 11 species from 4 genera. Major collected mosquito species were Culex quinquefasciatus, Aedes albopictus, Culex tritaeniorhynchus, Aedes aegypti, and Armigeres subalbatus. The collected mosquitoes were divided into 285 pools and used for virus isolation using two mammalian cell lines, Vero and BHK-21, and one mosquito cell line, C6/36. Seventy-two pools showed clear cytopathic effects only in C6/36 cells. Using RT-PCR and next-generation sequencing approaches, these isolates were identified as insect flaviviruses (family Flaviviridae, genus Flavivirus), Banna virus (family Reoviridae, genus Seadornavirus), new permutotetravirus (designed as Bogor virus) (family Permutotetraviridae, genus Alphapermutotetravirus), and alphamesoniviruses 2 and 3 (family Mesoniviridae, genus Alphamesonivirus). We believed that this large surveillance of mosquitoes and mosquito-borne viruses provides basic information for the prevention and control of emerging and re-emerging arboviral diseases.

Endemic and Emerging Arboviruses in Domestic Ruminants in East Asia

Epizootic congenital abnormalities caused by Akabane, Aino, and Chuzan viruses have damaged the reproduction of domestic ruminants in East Asia for many years. In the past, large outbreaks of febrile illness related to bovine ephemeral fever and Ibaraki viruses severely affected the cattle industry in that region. In recent years, vaccines against these viruses have reduced the occurrence of diseases, although the viruses are still circulating and have occasionally caused sporadic and small-scaled epidemics. Over a long-term monitoring period, many arboviruses other than the above-mentioned viruses have been isolated from cattle and Culicoides biting midges in Japan. Several novel arboviruses that may infect ruminants (e.g., mosquito- and tick-borne arboviruses) were recently reported in mainland China based on extensive surveillance. It is noteworthy that some are suspected of being associated with cattle diseases. Malformed calves exposed to an intrauterine infection with orthobunyaviruses (e.g., Peaton and Shamonda viruses) have been observed. Epizootic hemorrhagic disease virus serotype 6 caused a sudden outbreak of hemorrhagic disease in cattle in Japan. Unfortunately, the pathogenicity of many other viruses in ruminants has been uncertain, although these viruses potentially affect livestock production. As global transportation grows, the risk of an accidental incursion of arboviruses is likely to increase in previously non-endemic areas. Global warming will also certainly affect the distribution and active period of vectors, and thus the range of virus spreads will expand to higher-latitude regions. To prevent anticipated damages to the livestock industry, the monitoring system for arboviral circulation and incursion should be strengthened; moreover, the sharing of information and preventive strategies will be essential in East Asia.

A viral metagenomic analysis reveals rich viral abundance and diversity in mosquitoes from pig farms

Mosquitoes harbour a diversity of viruses and are responsible for several mosquito-borne viral diseases of humans and animals, thereby leading to major public health concerns, and significant economic losses across the globe. Viral metagenomics offers a great opportunity for bulk analysis of viral genomes retrieved directly from environmental samples. In this study, we performed a viral metagenomic analysis of five pools of mosquitoes belonging to Aedes, Anopheles and Culex species, collected from different pig farms in the vicinity of Shanghai, China, to explore the viral community carried by mosquitoes. The resulting metagenomic data revealed that viral community in the mosquitoes was highly diverse and varied in abundance among pig farms, which comprised of more than 48 viral taxonomic families, specific to vertebrates, invertebrates, plants, fungi, bacteria and protozoa. In addition, a considerable number of viral reads were related to viruses that are not classified by host. The read sequences related to animal viruses included parvoviruses, anelloviruses, circoviruses, flavivirus, rhabdovirus and seadornaviruses, which might be taken up by mosquitoes from viremic animal hosts during blood feeding. Notably, sample G1 contained the most abundant sequence related to Banna virus, which is of public health interest because it causes encephalitis in humans. Furthermore, non-classified viruses also shared considerable virus sequences in all the samples, presumably belonging to unexplored virus category. Overall, the present study provides a comprehensive knowledge of diverse viral populations carried by mosquitoes at pig farms, which is a potential source of diseases for mammals including humans and animals. These viral metagenomic data are valuable for assessment of emerging and re-emerging viral epidemics.

A combinatorial approach of structure-based virtual screening and molecular dynamics simulation towards the discovery of a highly selective inhibitor for VP9 coat protein of Banna virus

Structure based virtual screening of two libraries containing 27,628 numbers of antiviral compounds was used to discover a few of the potent inhibitor molecules against Banna virus (BAV). Cross-docking studies with many common interfering proteins provided five of the highly selective inhibitor for BAV. Analyses of the leading molecules with ADME-Tox filtering tool and atomistic molecular dynamics simulation studies finally discovered a benzoxazolone derivative as one of the most promising molecules towards the highly selective inhibition of BAV. The theoretical calculations are also supported by the experimental evidences where the interactions between the hit ligand and a model peptide sequence, mimicking the VP9 protein of BAV, were studied. Overall the development of a personalized therapeutic towards the highly selective inhibition of BAV is discussed herein for the first time in literature.

First Isolation and Characterization of a Group C Banna Virus (BAV) from Anopheles sinensis Mosquitoes in Hubei, China

Banna virus (BAV) is considered to be an emerging human pathogen that is transmitted by blood-sucking insects. BAV was isolated from various species of mosquitoes, midges, and livestock. It is widely distributed geographically, since it was identified in China, Vietnam, and Indonesia. Previously reported evolution studies of BAV indicated that BAV can be divided into two groups, including isolates from China and Vietnam clustered in group A, and Indonesian isolates in group B. In this study, we report the isolation of a new strain of BAV named HB14-71-01 from Anopheles sinensis mosquitoes from Hubei, China. An in vitro comparison study of the HB14-71-01 isolate and the group A BAV revealed differences based on observed cytopathic effect, plaque size, and viral growth rates. Additionally, the phylogenetic analysis indicated that the Hubei isolate belongs to a novel genotype of BAV and emerged nearly 105 years ago (95% highest posterior density (HPD): 35–434), unlike the two previously reported genotypes A and B. Our findings extend the knowledge about the genomic diversity and potential vectors/hosts of BAVs and will improve understanding of the relationships between genetic variation and pathogenicity.

Identification and genetic analysis of Kadipiro virus isolated in Shandong province, China

Background

Kadipiro virus (KDV) belongs to the Reoviridae family, which consists of segmented, non-enveloped, double-stranded RNA viruses. It has previously been isolated from Culex, Anopheles, Armigeres and Aedes mosquitoes in Indonesia and China. Here, we describe the isolation and characterization of SDKL1625 from Anopheles sinensis mosquitoes in Shandong province, China.

Methods

In this study, we isolated Kadipiro virus in Aedes albopictus C6/36 cell culture and the complete genome sequencing was made by next generation sequencing.

Results

We isolated and characterized a Kadipiro virus from Anopheles sinensis mosquitoes in 2016 in Shandong province, China. Nucleotide and amino acid homology analysis of SDKL1625 showed higher levels of sequence identity with QTM27331 (Odonata, China, 2016) than with JKT-7075 (Culex fuscocephalus, Indonesia, 1981). The SDKL1625 has 86–97% amino acid identity with the JKT-7075, 88–99% amino acid identity with the QTM27331. Among the 12 fragments, VP1, VP2, VP4, VP6, VP7, VP9 and VP12 showed high amino acid identity (> 90%) and VP5 showed the lowest identity (86% and 88%).

Conclusions

This is the first identification of KDV from mosquito in China. Virus morphology and genome organization were also determined, which will further enrich our understanding of the molecular biological characteristics of KDV and seadornaviruses.

New genotypes of Liao ning virus (LNV) in Australia exhibit an insect-specific phenotype

Liao ning virus (LNV) was first isolated in 1996 from mosquitoes in China, and has been shown to replicate in selected mammalian cell lines and to cause lethal haemorrhagic disease in experimentally infected mice. The first detection of LNV in Australia was by deep sequencing of mosquito homogenates. We subsequently isolated LNV from mosquitoes of four genera (Culex, Anopheles, Mansonia and Aedes) in New South Wales, Northern Territory, Queensland and Western Australia; the earliest of these Australian isolates were obtained from mosquitoes collected in 1988, predating the first Chinese isolates. Genetic analysis revealed that the Australian LNV isolates formed two new genotypes: one including isolates from eastern and northern Australia, and the second comprising isolates from the south-western corner of the continent. In contrast to findings reported for the Chinese LNV isolates, the Australian LNV isolates did not replicate in vertebrate cells in vitro or in vivo, or produce signs of disease in wild-type or immunodeficient mice. A panel of human and animal sera collected from regions where the virus was found in high prevalence also showed no evidence of LNV-specific antibodies. Furthermore, high rates of virus detection in progeny reared from infected adult female mosquitoes, coupled with visualization of the virus within the ovarian follicles by immunohistochemistry, suggest that LNV is transmitted transovarially. Thus, despite relatively minor genomic differences between Chinese and Australian LNV strains, the latter display a characteristic insect-specific phenotype.

Mosquito-Associated Viruses in China

Mosquitoes are classified into approximately 3500 species and further grouped into 41 genera. Epidemiologically, they are considered to be among the most important disease vectors in the world and they can harbor a wide variety of viruses. Several mosquito viruses are considered to be of significant medical importance and can cause serious public health issues throughout the world. Such viruses are Japanese encephalitis virus (JEV), dengue virus (DENV), chikungunya virus (CHIKV), and Zika virus (ZIKV). Others are the newly recognized mosquito viruses such as Banna virus (BAV) and Yunnan orbivirus (YNOV) with unclear medical significance. The remaining mosquito viruses are those that naturally infect mosquitoes but do not appear to infect humans or other vertebrates. With the continuous development and improvement of mosquito and mosquito-associated virus surveillance systems in China, many novel mosquito-associated viruses have been discovered in recent years. This review aims to systematically outline the history, characteristics, distribution, and/or current epidemic status of mosquito-associated viruses in China.

Arboviruses and their related infections in China: A comprehensive field and laboratory investigation over the last 3 decades

Since the 1980s, a comprehensive field and laboratory investigation has been conducted throughout China, and a total of 29 virus species belonging to 7 families and 13 genera were identified through virological, morphological, and immunological methods, as well as whole-genome sequencing and molecular genetic analyses. Most of the virus isolates belong to 9 genera in the families Flaviviridae, Bunyaviridae, Togaviridae, and Reoviridae. Among them, 4 genera (Orthobunyavirus, Bunyavirus, Phlebovirus, and Nairovirus) belong to the family Bunyaviridae and 3 genera (Seadonavirus, Orbivirus, and Cypovirus) belong to the family Reoviridae. Analyses of the relationships between viruses and human/animal diseases indicated that Japanese encephalitis virus, dengue virus, severe fever with thrombocytopenia syndrome virus, tick-borne encephalitis virus, Crimean-Congo hemorrhagic fever virus, West Nile virus, and Tahyna virus can cause human and animal infections and disease epidemics in China. This review systematically introduces the current status of the diversity and geographical distribution of arboviruses and vectors in China. In addition, our results provide strong technical support for the prevention and control of arboviral diseases, the treatment of epidemics, and the early warning and prediction of diseases, and so they are significant for the control and prevention of arboviral diseases in Asia and around the world.

Genome sequencing and phylogenetic analysis of Banna virus (genus Seadornavirus, family Reoviridae) isolated from Culicoides

In an investigation of blood-sucking insects and arboviruses, a virus (YN12243) was isolated from Culicoides samples collected in the Sino-Burmese border region of Yunnan Province, China. The virus caused cytopathic effect (CPE) in C6/36 cells and passaged stably. Polyacrylamide gel analysis showed that the genome of YN12243 was composed of 12 segments of double-stranded RNA (dsRNA), with a distribution pattern of 6-6. The nucleotide and amino acid sequences of the coding region (1‒12 segments) were 17,803 bp and 5,925 amino acids in length, respectively. The phylogenetic analysis of VP1 protein (RdRp) revealed that YN12243 belonged to genus Seadornavirus of family Reoviridae, and further analysis indicated that YN12243 belongs to the Banna virus (BAV) genotype A2. Additionally, YN12243 was located in the same evolutionary cluster as BAV strains isolated from different mosquito species, suggesting that the BAV isolated from Culicoides does not have species barriers. These results indicate that Culicoides can also be a vector for BAV. In view of the hematophagous habits of Culicoides on cattle, horses, deer, and other large animals, as well as the possibility of spreading and causing a variety of animal arboviral diseases, it is important to improve infection detection and monitor the BAV in large livestock.

An RNA Virome Associated to the Golden Orb-Weaver Spider Nephila clavipes

The golden orb-weaver spider Nephila clavipes, known for its sexual size dimorphism, is abundant and widespread in the New World. The first annotated genome of orb-weaver spiders, exploring N. clavipes, has recently been reported. The study, focused primarily on the diversity of silk specific genes, shed light into the complex evolutionary history of spiders. Furthermore, a robust transcriptome analysis provided a massive resource for N. clavipes RNA survey. Here, I present evidence of viral sequences corresponding to the first 10 extant virus species associated to N. clavipes and indeed, nephilids. The putatively new species are linked to ssRNA positive-strand viruses, such as Picornavirales, and to ssRNA negative-strand and dsRNA viruses. In addition, I detected sequence data of new strains of two recently reported arthropod viruses, which complemented and extended the corresponding sequence references. The identified viruses appear to be complete, potentially functional, and presenting the typical architecture and consistent viral domains. The intrinsic nature of the detected sequences and their absence in the recently generated genome assembly, suggest that they correspond to bona fide RNA virus sequences. The available RNA data allowed for the first time to address a tissue/organ specific analysis of virus loads/presence in spiders, suggesting a complex spatial and differential distribution of the tentative viruses, encompassing the spider brain and also silk and venom glands. Until recently, the virus landscape associated to spiders remained elusive. The discovered viruses described here provide only a fragmented glimpse of the potential magnitude of the Aranea virosphere. Future studies should focus not only on complementing and expanding these findings, but also on addressing the potential ecological role of these viruses, which might influence the biology of these outstanding arthropod species.

Genomes of viral isolates derived from different mosquitos species

Eleven viral isolates derived mostly in albopictus C6/36 cells from mosquito pools collected in Southeast Asia and the Americas between 1966 and 2014 contained particles with electron microscopy morphology typical of reoviruses. Metagenomics analysis yielded the near complete genomes of three novel reoviruses, Big Cypress orbivirus, Ninarumi virus, and High Island virus and a new tetravirus, Sarawak virus. Strains of previously characterized Sathuvarachi, Yunnan, Banna and Parry's Lagoon viruses (Reoviridae), Bontang virus (Mesoniviridae), and Culex theileri flavivirus (Flaviviridae) were also characterized. The availability of these mosquito virus genomes will facilitate their detection by metagenomics or PCR to better determine their geographic range, extent of host tropism, and possible association with arthropod or vertebrate disease.

Commensal Viruses of Mosquitoes: Host Restriction, Transmission, and Interaction with Arboviral Pathogens

Recent advances in virus detection strategies and deep sequencing technologies have enabled the identification of a multitude of new viruses that persistently infect mosquitoes but do not infect vertebrates. These are usually referred to as insect-specific viruses (ISVs). These novel viruses have generated considerable interest in their modes of transmission, persistence in mosquito populations, the mechanisms that restrict their host range to mosquitoes, and their interactions with pathogens transmissible by the same mosquito. In this article, we discuss studies in our laboratory and others that demonstrate that many ISVs are efficiently transmitted directly from the female mosquito to their progeny via infected eggs, and, moreover, that persistent infection of mosquito cell cultures or whole mosquitoes with ISVs can restrict subsequent infection, replication, and transmission of some mosquito-borne viral pathogens. This suggests that some ISVs may act as natural regulators of arboviral transmission. We also discuss viral and host factors that may be responsible for their host restriction.

The plasma virome of febrile adult Kenyans shows frequent parvovirus B19 infections and a novel arbovirus (Kadipiro virus)

Viral nucleic acids present in the plasma of 498 Kenyan adults with unexplained fever were characterized by metagenomics analysis of 51 sample pools. The highest to lowest fraction of plasma pools was positive for parvovirus B19 (75 %), pegivirus C (GBV-C) (67 %), alpha anellovirus (59 %), gamma anellovirus (55 %), beta anellovirus (41 %), dengue virus genotype 2 (DENV-2) (16 %), human immunodeficiency virus type 1 (6 %), human herpesvirus 6 (6 %), HBV (4 %), rotavirus (4 %), hepatitis B virus (4 %), rhinovirus C (2 %), Merkel cell polyomavirus (MCPyV; 2 %) and Kadipiro virus (2 %). Ranking by overall percentage of viral reads yielded similar results. Characterization of viral nucleic acids in the plasma of a febrile East African population showed a high frequency of parvovirus B19 and DENV infections and detected a reovirus (Kadipiro virus) previously reported only in Asian Culex mosquitoes, providing a baseline to compare with future virome studies to detect emerging viruses in this region.

Optimized polypeptide for a subunit vaccine against avian reovirus

Avian reovirus (ARV) is a disease-causing agent. The disease is prevented by vaccination with a genotype-specific vaccine while many variants of ARV exist in the field worldwide. Production of new attenuated vaccines is a long-term process and in the case of fast-mutating viruses, an impractical one. In the era of molecular biology, vaccines may be produced by using only the relevant protein for induction of neutralizing antibodies, enabling fast adjustment to the emergence of new genetic strains. Sigma C (SC) protein of ARV is a homotrimer that facilitates host-cell attachment and induce the production and secretion of neutralizing antibodies. The aim of this study was to identify the region of SC that will elicit a protective immune response. Full-length (residues 1-326) and two partial fragments of SC (residues 122-326 and 192-326) were produced in Escherichia coli. The SC fragment of residues 122-326 include the globular head, shaft and hinge domains, while eliminating intra-capsular region. This fragment induces significantly higher levels of anti-ARV antibodies than the shorter fragment or full length SC, which neutralized embryos infection by the virulent strain to a higher extent compared with the antibodies produced in response to the whole virus vaccine. Residues 122-326 fragment is assumed to be folded correctly, exposing linear as well as conformational epitopes that are identical to those of the native protein, while possibly excluding suppressor sequences. The results of this study may serve for the development of a recombinant subunit vaccine for ARV.

Genome Sequence Analysis of CsRV1: A Pathogenic Reovirus that Infects the Blue Crab Callinectes sapidus Across Its Trans-Hemispheric Range

The blue crab, Callinectes sapidus Rathbun, 1896, which is a commercially important trophic link in coastal ecosystems of the western Atlantic, is infected in both North and South America by C. sapidus Reovirus 1 (CsRV1), a double stranded RNA virus. The 12 genome segments of a North American strain of CsRV1 were sequenced using Ion Torrent technology. Putative functions could be assigned for 3 of the 13 proteins encoded in the genome, based on their similarity to proteins encoded in other reovirus genomes. Comparison of the CsRV1 RNA-dependent RNA polymerase (RdRP) sequence to genomes of other crab-infecting reoviruses shows that it is similar to the mud crab reovirus found in Scylla serrata and WX-2012 in Eriocheir sinensis, Chinese mitten crab, and supports the idea that there is a distinct “Crabreo” genus, different from Seadornavirus and Cardoreovirus, the two closest genera in the Reoviridae. A region of 98% nucleotide sequence identity between CsRV1 and the only available sequence of the P virus of Macropipus depurator suggests that these two viruses may be closely related. An 860 nucleotide region of the CsRV1 RdRP gene was amplified and sequenced from 15 infected crabs collected from across the geographic range of C. sapidus. Pairwise analysis of predicted protein sequences shows that CsRV1 strains in Brazil can be distinguished from those in North America based on conserved residues in this gene. The sequencing, annotation, and preliminary population metrics of the genome of CsRV1 should facilitate additional studies in diverse disciplines, including structure-function relationships of reovirus proteins, investigations into the evolution of the Reoviridae, and biogeographic research on the connectivity of C. sapidus populations across the Northern and Southern hemispheres.

Molecular characterization of a novel reovirus isolated from Pekin ducklings in China

The complete genome sequence of a novel duck orthoreovirus, designated DRV strain TH11(DRV-TH11), was determined and characterized. The DRV-TH11 genome is comprised of 23,417 bp and its genome organization is more similar to that of avian orthoreoviruses (ARVs) of chicken origin than other reoviruses. The results of comparative sequence analysis and dendrograms based on the µB- and σC-encoding genes indicated that TH11 may be derived from the reassortment of ARVs and classic Muscovy duck reovirus (MDRV). A possible recombinant event was identified using the SimPlot program, and it occurred in the M2 segment. The results indicated that reassortment and mutation play a role in the evolution of duck reovirus.

Tibet Orbivirus, a novel Orbivirus species isolated from Anopheles maculatus mosquitoes in Tibet, China

Background

The genus Orbivirus includes a number of important pathogenic viruses, including Bluetongue virus (BTV), African horse sickness virus (AHSV), and Epizootic hemorrhagic disease virus (EHDV). In this study we describe the isolation and characterization of an Orbivirus strain isolated from Anopheles maculatus mosquitoes collected in Tibet, China.

Methods and Results

Initial viral screening identified a viral strain (XZ0906) that caused significant cytopathic effect (CPE) in BHK-21 cells, including rounding, cell rupture, and floating. Although CPE was not observed in insect cells (C6/36), these cells supported viral replication. Polyacrylamide gel analysis revealed a genome consisting of 10 segments of double-stranded RNA (dsRNA), with a distribution pattern of 3-3-3-1. 454 high throughput sequencing of culture supernatant was used for viral identification. Complete genome sequencing was performed by Sanger sequencing in combination with 5′-RACE and 3′-RACE. Sequence analysis demonstrated that all 5′- and 3′- untranslated regions (UTRs) for each of the 10 genome segments contained a series of six highly conserved nucleotides. In addition, homology analysis and phylogenetic analysis based on amino acid sequence was completed, and all results show that virus XZ0906 was not a member of any known species or serotype of Orbivirus, indicating it to be a new species within the genus Orbivirus.

Conclusions

The isolated Orbivirus strain was designated Tibet Orbivirus, TIBOV to denote the location from which it was isolated. TIBOV is a novel orbivirus species which is isolated from Anopheles maculatus mosquitoes collected in Tibet, China.

Full-genome characterisation of Orungo, Lebombo and Changuinola viruses provides evidence for co-evolution of orbiviruses with their arthropod vectors

The complete genomes of Orungo virus (ORUV), Lebombo virus (LEBV) and Changuinola virus (CGLV) were sequenced, confirming that they each encode 11 distinct proteins (VP1-VP7 and NS1-NS4). Phylogenetic analyses of cell-attachment protein 'outer-capsid protein 1' (OC1), show that orbiviruses fall into three large groups, identified as: VP2(OC1), in which OC1 is the 2nd largest protein, including the Culicoides transmitted orbiviruses; VP3(OC1), which includes the mosquito transmitted orbiviruses; and VP4(OC1) which includes the tick transmitted viruses. Differences in the size of OC1 between these groups, places the T2 'subcore-shell protein' as the third largest protein 'VP3(T2)' in the first of these groups, but the second largest protein 'VP3(T2)' in the other two groups. ORUV, LEBV and CGLV all group with the Culicoides-borne VP2(OC1)/VP3(T2) viruses. The G+C content of the ORUV, LEBV and CGLV genomes is also similar to that of the Culicoides-borne, rather than the mosquito-borne, or tick borne orbiviruses. These data suggest that ORUV and LEBV are Culicoides- rather than mosquito-borne. Multiple isolations of CGLV from sand flies suggest that they are its primary vector. OC1 of the insect-borne orbiviruses is approximately twice the size of the equivalent protein of the tick borne viruses. Together with internal sequence similarities, this suggests its origin by duplication (concatermerisation) of a smaller OC1 from an ancestral tick-borne orbivirus. Phylogenetic comparisons showing linear relationships between the dates of evolutionary-separation of their vector species, and genetic-distances between tick-, mosquito- or Culicoides-borne virus-groups, provide evidence for co-evolution of the orbiviruses with their arthropod vectors.

Culicoides midge bites modulate the host response and impact on bluetongue virus infection in sheep

Many haematophagous insects produce factors that help their blood meal and coincidently favor pathogen transmission. However nothing is known about the ability of Culicoides midges to interfere with the infectivity of the viruses they transmit. Among these, Bluetongue Virus (BTV) induces a hemorrhagic fever- type disease and its recent emergence in Europe had a major economical impact. We observed that needle inoculation of BTV8 in the site of uninfected C. nubeculosus feeding reduced viraemia and clinical disease intensity compared to plain needle inoculation. The sheep that developed the highest local inflammatory reaction had the lowest viral load, suggesting that the inflammatory response to midge bites may participate in the individual sensitivity to BTV viraemia development. Conversely compared to needle inoculation, inoculation of BTV8 by infected C. nubeculosus bites promoted viraemia and clinical symptom expression, in association with delayed IFN- induced gene expression and retarded neutralizing antibody responses. The effects of uninfected and infected midge bites on BTV viraemia and on the host response indicate that BTV transmission by infected midges is the most reliable experimental method to study the physio-pathological events relevant to a natural infection and to pertinent vaccine evaluation in the target species. It also leads the way to identify the promoting viral infectivity factors of infected Culicoides in order to possibly develop new control strategies against BTV and other Culicoides transmitted viruses.

Mobuck virus genome sequence and phylogenetic analysis: identification of a novel Orbivirus isolated from a white-tailed deer in Missouri, USA

The genus Orbivirus includes a diverse group of segmented dsRNA viruses that are transmitted via arthropods, have a global distribution and affect a wide range of hosts. A novel orbivirus was co-isolated with epizootic haemorrhagic disease virus (EHDV) from a white-tailed deer (Odocoileus virginianus) exhibiting clinical signs characteristic of EHDV. Using antiserum generated against EHDV, a pure isolate of the novel non-cytopathic orbivirus was obtained in Aedes albopictus cell culture. Genomic sequencing and phylogenetic analysis of predicted ORFs showed that eight of the ten ORFs were most homologous to Peruvian horse sickness virus (PHSV), with amino acid identities of 44.3–73.7 %. The remaining two ORFs, VP3 and VP5, were most similar to Middle Point orbivirus (35.9 %) and Yunnan orbivirus (59.8 %), respectively. Taxonomic classification of orbiviruses is largely based on homology of the major subcore structural protein VP2(T2), encoded by segment 2 for mobuck virus. With only 69.1 % amino acid identity to PHSV, we propose mobuck virus as the prototype of a new species of Orbivirus.

Identification and genomic characterization of a novel fish reovirus, Hubei grass carp disease reovirus, isolated in 2009 in China

A novel fish reovirus, Hubei grass carp disease reovirus (HGDRV; formerly grass carp reovirus strain 104, GCRV104), was isolated from diseased grass carp in China in 2009 and the full genome sequence was determined. This reovirus was propagated in a grass carp kidney cell line with a typical cytopathic effect. The total size of the genome was 23 706 bp with a 51 mol% G+C content, and the 11 dsRNA segments encoded 12 proteins (two proteins encoded by segment 11). A nucleotide sequence similarity search using blastn found no significant matches except for segment 2, which partially matched that of the RNA-dependent RNA polymerase (RdRp) from several viruses in the genera Aquareovirus and Orthoreovirus of the family Reoviridae. At the amino acid level, seven segments (Seg-1 to Seg-6, and Seg-8) matched with species in the genera Aquareovirus (15-46 % identities) and Orthoreovirus (12-44 % identities), while for four segments (Seg-7, Seg-9, Seg-10 and Seg-11) no similarities in these genera were found. Conserved terminal sequences, 5'-GAAUU----UCAUC-3', were found in each HGDRV segment at the 5' and 3' ends, and the 5'-terminal nucleotides were different from any known species in the genus Aquareovirus. Phylogenetic analysis based on RdRp amino acid sequences from members of the family Reoviridae showed that HGDRV clustered with aquareoviruses prior to joining a branch common with orthoreoviruses. Based on these observations, we propose that HGDRV is a new species in the genus Aquareovirus that is distantly related to any known species within this genus.

Isolates of Liao ning virus from wild-caught mosquitoes in the Xinjiang province of China in 2005

Liao ning virus (LNV) is related to Banna virus, a known human-pathogen present in south-east Asia. Both viruses belong to the genus Seadornavirus, family Reoviridae. LNV causes lethal haemorrhage in experimentally infected mice. Twenty seven isolates of LNV were made from mosquitoes collected in different locations within the Xinjiang province of north-western China during 2005. These mosquitoes were caught in the accommodation of human patients with febrile manifestations, or in animal barns where sheep represent the main livestock species. The regions where LNV was isolated are affected by seasonal encephalitis, but are free of Japanese encephalitis (JE). Genome segment 10 (Seg-10) (encoding cell-attachment and serotype-determining protein VP10) and Seg-12 (encoding non-structural protein VP12) were sequenced for multiple LNV isolates. Phylogenetic analyses showed a less homogenous Seg-10 gene pool, as compared to segment 12. However, all of these isolates appear to belong to LNV type-1. These data suggest a relatively recent introduction of LNV into Xinjiang province, with substitution rates for LNV Seg-10 and Seg-12, respectively, of 2.29×10⁻⁴ and 1.57×10⁻⁴ substitutions/nt/year. These substitution rates are similar to those estimated for other dsRNA viruses. Our data indicate that the history of LNV is characterized by a lack of demographic fluctuations. However, a decline in the LNV population in the late 1980s - early 1990s, was indicated by data for both Seg-10 and Seg-12. Data also suggest a beginning of an expansion in the late 1990s as inferred from Seg-12 skyline plot.

Newly recognized mosquito-associated viruses in mainland China, in the last two decades

There are four principal arboviruses in mainland China. Two kinds of them are mosquito-borne viruses, namely Japanese encephalitis virus and dengue virus, which lead to Japanese encephalitis, and dengue fever/dengue hemorrhagic fever respectively; the other two are tick-borne viruses, namely tick-borne encephalitis virus and Crimean-Congo hemorrhagic fever virus (also known as Xinjiang hemorrhagic fever virus), which contribute to tick-borne encephalitis and Xinjiang hemorrhagic fever respectively. With exception of these four main arboviruses, many other mosquito-associated viruses have been isolated and identified in recent years. These newly isolated and identified mosquito-associated viruses are probably responsible for human and animal infections and diseases. The purpose of this review is to describe the newly isolated mosquito-associated viruses in mainland China which belong to five viral families, including their virological properties, phylogenetic relationships, serological evidence, as well as to appeal the public health concentration worldwide.

Nucleotide sequences of four RNA segments of a reovirus isolated from the mud crab Scylla serrata provide evidence that this virus belongs to a new genus in the family Reoviridae

This is the first sequence-based characterization of mud crab (Scylla serrata) reovirus (SsRV), which causes severe disease of cultured mud crabs in southern China. We sequenced and analyzed genome segments S1, S2, S3, and S7, which were 4,327, 2,721, 2,715, and 1,517 nucleotides long, respectively. Conserved motifs were found at the 5' (AUAAAU) and 3' (AACGAU) ends of each segment. RNA segments S1, S2, S3, and S7 each contained a single open reading frame (ORF) that encoded predicted proteins of 160, 100, 96, and 46 kDa, respectively. The ORFs of segments S1 and S2 showed distant homologies (< 25%) with cognate genes of other reoviruses, whereas the ORFs of segments S3 and S7 had no homologies with any other viral genes. Based on these observations, we propose that SsRV should be considered a member of a new genus in the family Reoviridae.

A versatile molecular tagging method for targeting proteins to avian reovirus muNS inclusions. Use in protein immobilization and purification

Background

Avian reoviruses replicate in viral factories, which are dense cytoplasmic compartments estabilished by protein-protein interactions. The non-structural protein muNS forms the factory scaffold that attracts other viral components in a controlled fashion. To create such a three-dimensional network, muNS uses several different self-interacting domains.

Methodology/Principal Findings

In this study we have devised a strategy to identify muNS regions containing self-interacting domains, based on the capacity of muNS-derived inclusions to recruit muNS fragments. The results revealed that the muNS region consisting of residues 477–542 was recruited with the best efficiency, and this raised the idea of using this fragment as a molecular tag for delivering foreign proteins to muNS inclusions. By combining such tagging system with our previously established method for purifying muNS inclusions from baculovirus-infected insect cells, we have developed a novel protein purification protocol.

Conclusions/Significance

We show that our tagging and inclusion-targeting system can be a simple, versatile and efficient method for immobilizing and purifying active proteins expressed in baculovirus-infected cells. We also demonstrate that muNS inclusions can simultaneously recruit several tagged proteins, a finding which may be used to generate protein complexes and create multiepitope particulate material for immunization purposes.

IC-tagging and protein relocation to ARV muNS inclusions: a method to study protein-protein interactions in the cytoplasm or nucleus of living cells

Background

Characterization of protein-protein interactions is essential for understanding cellular functions. Although there are many published methods to analyze protein-protein interactions, most of them present serious limitations. In a different study we have characterized a novel avian reovirus muNS-based protein tagging and inclusion targeting method, and demonstrated its validity to purify free an immobilized protein.

Methodology/Principal Findings

Here we present a method to identify protein-protein interactions inside living eukaryotic cells (tested in primate and avian cells). When p53 was tagged with Intercoil (IC; muNS residues 477–542), it not only got integrated into muNS cytoplasmic inclusions, but also attracted its known ligand SV40 large T antigen (TAg) to these structures. We have also adapted this system to work within the cell nucleus, by creating muNS-related protein chimeras that form nuclear inclusions. We show that nuclear muNS-derived inclusions are as efficient as cytoplasmic ones in capturing IC-tagged proteins, and that the proteins targeted to nuclear inclusions are able to interact with their known ligands.

Conclusions/Significance

Our protein redistribution method does not present the architectural requirement of re-constructing a transcription factor as any of the two-hybrid systems do. The method is simple and requires only cell transfection and a fluorescence microscope. Our tagging method can be used either in the cytoplasm or the nucleus of living cells to test protein-protein interactions or to perform functional studies by protein ligand sequestration.

Complete sequence of Great Island virus and comparison with the T2 and outer-capsid proteins of Kemerovo, Lipovnik and Tribec viruses (genus Orbivirus, family Reoviridae)

The complete nucleotide sequence of Great Island virus (GIV) genome was determined, along with genome segments (Seg) 1, 2 and 6 of Kemerovo (KEMV), Lipovnik (LIPV) and Tribec (TRBV) viruses. All four viruses, together with Broadhaven virus, are currently classified within the species Great Island virus and have been isolated from ticks, birds or humans. Sequence comparisons showed that Seg-4 of GIV encoded the outer-capsid protein responsible for cell attachment, although it was approximately half the length of its counterpart in the Culicoides or mosquito-transmitted orbiviruses. A second overlapping ORF (in the +2 reading frame) was identified in Seg-9 of GIV, encoding a putative dsRNA-binding protein. Phylogenetic analyses of the RNA-dependent RNA polymerase (Pol) and T2 protein amino acid sequences indicated that the tick-borne orbiviruses represent an ancestral group from which the mosquito-borne orbiviruses have evolved. This mirrors the evolutionary relationships between the arthropod vectors of these viruses, supporting a co-speciation hypothesis for these arboviruses and their arthropod-vectors. Phylogenetic analyses of the T2 proteins of KEMV, LIPV, TRBV and GIV (showing 82% amino acid identity) correlated with the early classification of Great Island viruses as two distinct serocomplexes (Great Island and Kemerovo serocomplexes). Amino acid identity levels in the VP1(Pol) and T2 proteins between the two serocomplexes were 73 and 82%, respectively, whilst those between previously characterized Orbivirus species are 53-73% and 26-83%, respectively. These data suggest that, despite limited genome segment reassortment between these two groups, their current classification within the same Orbivirus species could be re-evaluated.

Distribution of arboviruses and mosquitoes in northwestern Yunnan Province, China

From July to September in 2005 and 2006, a survey was conducted to identify mosquito species and mosquito-borne arboviruses at elevations ranging from 900-3280 m between 24 degrees 00' N and 29 degrees 00' N latitude in the northwestern part of Yunnan Province, China. A total of 54,879 mosquitoes representing 15 species and 4 genera was collected using UV light traps at 59 sites. Culex tritaeniorhynchus and Anopheles sinensis were the most abundant species. The density of mosquitoes as well as the diversity of species decreased with increasing altitude. A total of 21,008 mosquitoes in 281 pools representing all of the 15 species was tested for the presence of viruses using cell culture. Viruses identified included Japanese encephalitis virus (13 isolates), Getah virus (five isolates), Banna virus (three isolates), Kadipiro virus (five isolates), and Densovirus (seven isolates). These isolates were obtained from Culex tritaeniorhynchus (20 isolates), Anopheles sinensis (three isolates), Armigeres subalbatus (six isolates), Culex pipiens quinquefasciatus (two isolates), and from unidentified, mixed mosquitoes (two isolates). Most of the isolates were from collections made at elevations below 2,500 m. Vector Borne Zoonotic Dis. 0, 000-000.

Broome virus, a new fusogenic Orthoreovirus species isolated from an Australian fruit bat

This report describes the discovery and characterization of a new fusogenic orthoreovirus, Broome virus (BroV), isolated from a little red flying-fox (Pteropus scapulatus). The BroV genome consists of 10 dsRNA segments, each having a 3' terminal pentanucleotide sequence conserved amongst all members of the genus Orthoreovirus, and a unique 5' terminal pentanucleotide sequence. The smallest genome segment is bicistronic and encodes two small nonstructural proteins, one of which is a novel fusion associated small transmembrane (FAST) protein responsible for syncytium formation, but no cell attachment protein. The low amino acid sequence identity between BroV proteins and those of other orthoreoviruses (13-50%), combined with phylogenetic analyses of structural and nonstructural proteins provide evidence to support the classification of BroV in a new sixth species group within the genus Orthoreovirus.

Avian reovirus microNS protein forms homo-oligomeric inclusions in a microtubule-independent fashion, which involves specific regions of its C-terminal domain

Members of the genus Orthoreovirus replicate in cytoplasmic inclusions termed viral factories. Compelling evidence suggests that the nonstructural protein microNS forms the matrix of the factories and recruits specific viral proteins to these structures. In the first part of this study, we analyzed the properties of avian reovirus factories and microNS-derived inclusions and found that they are nonaggresome cytoplasmic globular structures not associated with the cytoskeleton which do not require an intact microtubule network for formation and maturation. We next investigated the capacity of avian reovirus microNS to form inclusions in transfected and baculovirus-infected cells. Our results showed that microNS is the main component of the inclusions formed by recombinant baculovirus expression. This, and the fact that microNS is able to self-associate inside the cell, suggests that microNS monomers contain all the interacting domains required for inclusion formation. Examination of the inclusion-forming capacities of truncated microNS versions allowed us to identify the region spanning residues 448 to 635 of microNS as the smallest that was inclusion competent, although residues within the region 140 to 380 seem to be involved in inclusion maturation. Finally, we investigated the roles that four different motifs present in microNS(448-635) play in inclusion formation, and the results suggest that the C-terminal tail domain is a key determinant in dictating the initial orientation of monomer-to-monomer contacts to form basal oligomers that control inclusion shape and inclusion-forming efficiency. Our results contribute to an understanding of the generation of structured protein aggregates that escape the cellular mechanisms of protein recycling.

Candidates in Astroviruses, Seadornaviruses, Cytorhabdoviruses and Coronaviruses for +1 frame overlapping genes accessed by leaky scanning

BACKGROUND

Overlapping genes are common in RNA viruses where they serve as a mechanism to optimize the coding potential of compact genomes. However, annotation of overlapping genes can be difficult using conventional gene-finding software. Recently we have been using a number of complementary approaches to systematically identify previously undetected overlapping genes in RNA virus genomes. In this article we gather together a number of promising candidate new overlapping genes that may be of interest to the community.

RESULTS

Overlapping gene predictions are presented for the astroviruses, seadornaviruses, cytorhabdoviruses and coronaviruses (families Astroviridae, Reoviridae, Rhabdoviridae and Coronaviridae, respectively).

Full-length sequencing and genetic characterization of Breu Branco virus (Reoviridae, Orbivirus) and two related strains isolated from Anopheles mosquitoes

Breu Branco virus (BE AR 492347) was isolated from Anopheles (Nyssorhynchus) triannulatus mosquitoes captured in Tucuruí, Pará State, northern Brazil, in 1988. No cross-reactivity by complement-fixation tests was observed between Breu Branco virus and other known arboviruses. Results of electron microscopy and physicochemical tests suggested that Breu Branco virus may be a member of the family Reoviridae. In order to elucidate its taxonomic status, a comprehensive genetic characterization was conducted for Breu Branco virus and related strains (BE AR 494475 and BE AR 486204) that were also isolated from Anopheles mosquitoes in the same area. This included full-length genome sequencing, determination of genetic traits and phylogenetic analysis. Breu Branco virus showed a similar genome organization to members of the genus Orbivirus, family Reoviridae. Genetically, Breu Branco virus was indistinguishable from strains BE AR 494475 and BE AR 486204. Phylogenetic analysis suggested that Breu Branco virus BE AR 492347 and its related strains constitute a novel species of the genus Orbivirus. Breu Branco virus is the first Brazilian orbivirus and the fifth orbivirus in the world to be sequenced fully.

Sequence analysis of four double-stranded RNA genomic segments reveals an orthoreovirus with a unique genotype infecting psittaciformes

This paper describes the characterization of four double-stranded ribonucleic acid segments, S1, S2, S3, and S4, of a newly identified pathogenic reovirus from parrots. The four segments share a unique 5' terminus GCUUUUC. The amino-acid sequences of the conserved sigma A and sigma NS proteins show less than 60% sequence similarity, whereas those of the outer capsid proteins sigma B and sigma C have at most 47% sequence similarity to their counterparts in other bird or bat reoviruses. In a phylogenetic analysis of the amino-acid sequences, the proteins coded for by the S1 segment, P10, P17, and sigma C, group with their homologous proteins in other avian reoviruses, whereas the major capsid protein, sigma B, and the nonstructural protein, sigma NS, show more sequence similarity to their bat reoviral counterparts. The phylogenetic relationship of sigma A with the homologous avian and bat sequences is unresolved. The possibility that the parrot reovirus has evolved from an ancestral, more batlike reovirus is discussed. It is proposed to designate this unique virus as PsRV.

Isolation and molecular characterization of Banna virus from mosquitoes, Vietnam

We isolated and characterized a Banna virus from mosquitoes in Vietnam; 5 strains were isolated from field-caught mosquitoes at various locations; Banna virus was previously isolated from encephalitis patients in Yunnan, China, in 1987. Together, these findings suggest widespread distribution of this virus throughout Southeast Asia.