Complete genome characterization of mosavirus (family Picornaviridae) identified in droppings of a European roller (Coracias garrulus) in Hungary

Expansion of viral genomes with viral protein genome linked copies

Virus protein-linked genome (VPg) proteins are required for replication. VPgs are duplicated in a subset of RNA viruses however their roles are not fully understood and the extent of viral genomes containing VPg copies has not been investigated in detail. Here, we generated a novel bioinformatics approach to identify VPg sequences in viral genomes using hidden Markov models (HMM) based on alignments of dicistrovirus VPg sequences. From metagenomic datasets of dicistrovirus genomes, we identified 717 dicistrovirus genomes containing VPgs ranging from a single copy to 8 tandem copies. The VPgs are classified into nine distinct types based on their sequence and length. The VPg types but not VPg numbers per viral genome followed specific virus clades, thus suggesting VPgs co-evolved with viral genomes. We also identified VPg duplications in aquamavirus and mosavirus genomes. This study greatly expands the number of viral genomes that contain VPg copies and indicates that duplicated viral sequences are more widespread than anticipated.

No Exchange of Picornaviruses in Vietnam between Humans and Animals in a High-Risk Cohort with Close Contact despite High Prevalence and Diversity

Hospital-based and community-based 'high-risk cohort' studies investigating humans at risk of zoonotic infection due to occupational or residential exposure to animals were conducted in Vietnam, with diverse viruses identified from faecal samples collected from humans, domestic and wild animals. In this study, we focus on the positive-sense RNA virus family Picornaviridae, investigating the prevalence, diversity, and potential for cross-species transmission. Through metagenomic sequencing, we found picornavirus contigs in 23% of samples, belonging to 15 picornavirus genera. Prevalence was highest in bats (67%) while diversity was highest in rats (nine genera). In addition, 22% of the contigs were derived from novel viruses: Twelve phylogenetically distinct clusters were observed in rats of which seven belong to novel species or types in the genera Hunnivirus, Parechovirus, Cardiovirus, Mosavirus and Mupivirus; four distinct clusters were found in bats, belonging to one novel parechovirus species and one related to an unclassified picornavirus. There was no evidence for zoonotic transmission in our data. Our study provides an improved knowledge of the diversity and prevalence of picornaviruses, including a variety of novel picornaviruses in rats and bats. We highlight the importance of monitoring the human-animal interface for possible spill-over events.

Dissemination of Internal Ribosomal Entry Sites (IRES) Between Viruses by Horizontal Gene Transfer

Members of Picornaviridae and of the Hepacivirus, Pegivirus and Pestivirus genera of Flaviviridae all contain an internal ribosomal entry site (IRES) in the 5'-untranslated region (5'UTR) of their genomes. Each class of IRES has a conserved structure and promotes 5'-end-independent initiation of translation by a different mechanism. Picornavirus 5'UTRs, including the IRES, evolve independently of other parts of the genome and can move between genomes, most commonly by intratypic recombination. We review accumulating evidence that IRESs are genetic entities that can also move between members of different genera and even between families. Type IV IRESs, first identified in the Hepacivirus genus, have subsequently been identified in over 25 genera of Picornaviridae, juxtaposed against diverse coding sequences. In several genera, members have either type IV IRES or an IRES of type I, II or III. Similarly, in the genus Pegivirus, members contain either a type IV IRES or an unrelated type; both classes of IRES also occur in members of the genus Hepacivirus. IRESs utilize different mechanisms, have different factor requirements and contain determinants of viral growth, pathogenesis and cell type specificity. Their dissemination between viruses by horizontal gene transfer has unexpectedly emerged as an important facet of viral evolution.

Infection Load and Prevalence of Novel Viruses Identified from the Bank Vole Do Not Associate with Exposure to Environmental Radioactivity

Bank voles (Myodes glareolus) are host to many zoonotic viruses. As bank voles inhabiting areas contaminated by radionuclides show signs of immunosuppression, resistance to apoptosis, and elevated DNA repair activity, we predicted an association between virome composition and exposure to radionuclides. To test this hypothesis, we studied the bank vole virome in samples of plasma derived from animals inhabiting areas of Ukraine (contaminated areas surrounding the former nuclear power plant at Chernobyl, and uncontaminated areas close to Kyiv) that differed in level of environmental radiation contamination. We discovered four strains of hepacivirus and four new virus sequences: two adeno-associated viruses, an arterivirus, and a mosavirus. However, viral prevalence and viral load, and the ability to cause a systemic infection, was not dependent on the level of environmental radiation.

Genetically highly divergent RNA virus with astrovirus-like (5'-end) and hepevirus-like (3'-end) genome organization in carnivorous birds, European roller (Coracias garrulus)

Astroviruses (family Astroviridae) and hepeviruses (family Hepeviridae) are small, non-enveloped viruses with genetically diverse +ssRNA genome thought to be enteric pathogens infecting vertebrates including humans. Recently, many novel astro- and hepatitis E virus-like +ssRNA viruses have been described from lower vertebrate species. The non-structural proteins of astro- and hepeviruses are highly diverse, but the structural/capsid proteins represent a common phylogenetic position shed the light of their common origin by inter-viral recombination. In this study, a novel astrovirus/hepevirus-like virus with +ssRNA genome (Er/SZAL5/HUN/2011, MK450332) was serendipitously identified and characterized from 3 (8.5%) out of 35 European roller (Coracias garrulus) faecal samples by RT-PCR in Hungary. The complete genome of Er/SZAL5/HUN/2011 (MK450332) is 8402 nt-long and potentially composed three non-overlapping open reading frames (ORFs): ORF1a (4449 nt/1482aa), ORF1b (1206 nt/401aa) and ORF2 (1491 nt/496aa). The ORF1ab has an astrovirus-like genome organization containing the non-structural conserved elements (TM, CC, NLS, VPg) and enzyme residues (trypsine-like protease, RNA-dependent RNA-polymerase) with low amino acid sequence identity, 15% (ORF1a) and 44% (ORF1b), to astroviruses. Supposedly the ORF2 is a capsid protein but neither the astrovirus-like subgenomic RNA promoter (sgRNA) nor the astrovirus-like capsid characteristics have been identifiable. However, the predicted capsid protein (ORF2) showed 26% identity to the corresponding protein of hepevirus-like novel Rana hepevirus (MH330682). This novel +ssRNA virus strain Er/SZAL5/HUN/2011 with astrovirus-like genome organization in the non-structural genome regions (ORF1a and ORF1b) and Rana hepevirus-related capsid (ORF2) protein represent a potentially recombinant virus species and supports the common origin hypothesis, although, the taxonomic position of the studied virus is still under discussion.

Asian black bear (Ursus thibetanus) picornavirus related to seal aquamavirus A

The complete genome of a bear picornavirus 1 (BePV-1) in the viscera of an Asian black bear (Ursus thibetanus) from China was characterized using viral metagenomics and RT-PCR/Sanger sequencing. The genome of BePV1 is 6703 nt long, contains a type-IV IRES 5'UTR with the '8-like' motif, encodes a 2053-aa-long polyprotein showing a 3-4-4 organization pattern and two 2A genes. BePV-1 showed the highest overall genome nucleotide sequence identity of 71.7% to a picornavirus genome from an Arctic ringed seal (Phoca hispida) from Canada, classified as a member of the species Aquamavirus A, currently the only one in the genus Aquamavirus. Phylogenetic and genetic distance analyses of P1 and 3D indicated that Asian bear picornavirus (aquamavirus B) represents the second sequenced member of the genus Aquamavirus.

Ljungan/Sebokele-like picornavirus in birds of prey, common kestrel (Falco tinnunculus) and red-footed falcon (F. vespertinus)

Ljungan and Sebokele viruses are thought to be rodent-borne (picorna)viruses in the genus Parechovirus. Using random amplification and next generation sequencing method a novel Ljungan/Sebokele-like picornavirus was identified in birds of prey. Viral RNA was detected in total of 1 (9%) of the 11 and 2 (28.6%) of the 7 faecal samples from common kestrels and red-footed falcons in Hungary, respectively. High faecal viral RNA load (4.77×10⁶ genomic copies/ml) measured by qPCR. The complete genome of picornavirus strain falcon/HA18_080/2014/HUN (KY645497) is 7964-nucleotide (nt) long including a 867-nt 5'end and a 101-nt 3'end (excluding the poly(A)-tail). Falcon/HA18_080/2014/HUN has type-II IRES related to hunnivirus IRES, encodes a polyprotein lacking a leader protein, a VP0 maturation cleavage site and it predicted to encode three 2A proteins (2A₁^NPG↓P, 2A₂^NPG↓P and 2A₃^H-Box/NC), two of them end with 'ribosome-skipping' sites (DxExNPG^↓P). Sequence analyses indicated that the ORF1 (6996nt) polyprotein (2331 amino acid - aa) of falcon/HA18_080/2014/HUN shares the highest aa identity, 59% and 57%, to the corresponding polyproteins of Ljungan and Sebokele viruses. This study reports the identification and complete genome characterization of a novel Ljungan/Sebokele-like picornavirus in faeces of birds of prey which suggests that the genetic diversity and the potential host species spectrum of Ljungan/Sebokele-like viruses in genus Parechovirus are wider than previously thought.

Identification and Genome Characterization of the First Sicinivirus Isolate from Chickens in Mainland China by Using Viral Metagenomics

Unlike traditional virus isolation and sequencing approaches, sequence-independent amplification based viral metagenomics technique allows one to discover unexpected or novel viruses efficiently while bypassing culturing step. Here we report the discovery of the first Sicinivirus isolate (designated as strain JSY) of picornaviruses from commercial layer chickens in mainland China by using a viral metagenomics technique. This Sicinivirus isolate, which contains a whole genome of 9,797 nucleotides (nt) excluding the poly(A) tail, possesses one of the largest picornavirus genome so far reported, but only shares 88.83% and 82.78% of amino acid sequence identity to that of ChPV1 100C (KF979332) and Sicinivirus 1 strain UCC001 (NC_023861), respectively. The complete 939 nt 5′UTR of the isolate strain contains at least twelve stem-loop domains (A–L), representing the highest set of loops reported within Sicinivirus genus. The conserved 'barbell-like' structure was also present in the 272 nt 3′UTR of the isolate as that in the 3′ UTR of Sicinivirus 1 strain UCC001. The 8,586 nt large open reading frame encodes a 2,862 amino acids polyprotein precursor. Moreover, Sicinivirus infection might be widely present in commercial chicken farms in Yancheng region of the Jiangsu Province as evidenced by all the tested stool samples from three different farms being positive (17/17) for Sicinivirus detection. This is the first report on identification of Sicinivirus in commercial layer chickens with a severe clinical disease in mainland China, however, further studies are needed to evaluate the pathogenic potential of this picornavirus in chickens.

Avian picornaviruses: molecular evolution, genome diversity and unusual genome features of a rapidly expanding group of viruses in birds

Picornaviridae is one of the most diverse families of viruses infecting vertebrate species. In contrast to the relative small number of mammal species compared to other vertebrates, the abundance of mammal-infecting picornaviruses was significantly overrepresented among the presently known picornaviruses. Therefore most of the current knowledge about the genome diversity/organization patterns and common genome features were based on the analysis of mammal-infecting picornaviruses. Beside the well known reservoir role of birds in case of several emerging viral pathogens, little is known about the diversity of picornaviruses circulating among birds, although in the last decade the number of known avian picornavirus species with complete genome was increased from one to at least 15. However, little is known about the geographic distribution, host spectrum or pathogenic potential of the recently described picornaviruses of birds. Despite the low number of known avian picornaviruses, the phylogenetic and genome organization diversity of these viruses were remarkable. Beside the common L-4-3-4 and 4-3-4 genome layouts unusual genome patterns (3-4-4; 3-5-4, 3-6-4; 3-8-4) with variable, multicistronic 2A genome regions were found among avian picornaviruses. The phylogenetic and genomic analysis revealed the presence of several conserved structures at the untranslated regions among phylogenetically distant avian and non-avian picornaviruses as well as at least five different avian picornavirus phylogenetic clusters located in every main picornavirus lineage with characteristic genome layouts which suggests the complex evolution history of these viruses. Based on the remarkable genetic diversity of the few known avian picornaviruses, the emergence of further divergent picornaviruses causing challenges in the current taxonomy and also in the understanding of the evolution and genome organization of picornaviruses will be strongly expected. In this review we would like to summarize the current knowledge about the taxonomy, pathogenic potential, phylogenetic/genomic diversity and evolutional relationship of avian picornaviruses.

Identification and complete genome analysis of kobuvirus in faecal samples of European roller (Coracias garrulus): for the first time in a bird

The genus Kobuvirus (Picornaviridae) consists of three species, Aichivirus A (e.g., Aichi virus, which infects humans), Aichivirus B and Aichivirus C. Kobuvirus have not been detected in non-mammal species including birds. In this study, a novel kobuvirus was identified in 3 (17 %) out of 18 faecal samples collected from European rollers (Coracias garrulus) in Hungary. The complete genome sequence of strain SZAL6-KoV/2011/HUN (KJ934637), which was determined using a novel 5'/3' RACE method (dsRNA-RACE) involving a double-stranded (ds)RNA intermediate, has a type-V IRES at the 5' end and a cis-acting element (CRE) in the 3C gene and encodes L and 2A(H-box/NC) proteins, but it does not contain the sequence forming a "barbell-like" secondary RNA structure in the 3'UTR. SZAL6-KoV/2011/HUN has 72 %, 73 %, and 81 % amino acid sequence identity to the P1, P2, and P3 protein, respectively, of Aichi virus. Evolutionary analysis showed that SZAL6-KoV/2011/HUN shares a common ancestor with other kobuviruses but belongs to a more ancient lineage in the species Aichivirus A. Investigation of the known kobuviruses in different animals and discovery of novel kobuviruses in potential host species helps to clarify the evolutionary connection and zoonotic potential of kobuviruses.