Isolation and genomic characterization of a novel avian orthoreovirus strain in Korea, 2014

Characterization and pathogenicity of a novel avian orthoreovirus in China

Introduction

Avian orthoreovirus (ARV) is a significant pathogen causing viral arthritis, leading to substantial economic losses in the poultry industry worldwide.

Methods

A novel ARV strain, designated FJ202311, was isolated from a broiler farm in Fujian Province, China. Whole-genome sequencing was conducted using next-generation sequencing with MGI technology, and phylogenetic analysis of the sigma C amino acid sequence was performed. Comparative sequence analysis identified unique genetic features of FJ202311. Pathogenicity studies were carried out by inoculating broilers with the isolated strain and monitoring clinical signs, weight gain, and histopathological changes.

Results

The complete genome of FJ202311 was determined to be 23,495 base pairs in length, encoding 12 major proteins. Phylogenetic analysis revealed that FJ202311 forms a distinct genotypic cluster, exhibiting only 47.1% to 59.3% sequence identity to 16 reference ARV strains. Notably, 50 unique amino acid substitutions were identified in the sigma C protein. Pathogenicity tests demonstrated that FJ202311 caused severe arthritis and tenosynovitis in broilers. Infected birds exhibited significant weight loss compared to controls, with reductions of 11.78% and 8.93% at 14 and 21 days post-infection, respectively.

Discussion

This study highlights the unique molecular and pathogenic characteristics of the novel ARV strain FJ202311, contributing to our understanding of ARV diversity and epidemiology in China. These findings underscore the importance of continuous monitoring and provide insights for developing improved prevention and control strategies against ARV.

A Snapshot on the Genomic Epidemiology of Turkey Reovirus Infections, Hungary

Reovirus infections in turkeys are associated with arthritis and lameness. Viral genome sequence data are scarce, which makes an accurate description of the viral evolution and epidemiology difficult. In this study, we isolated and characterized turkey reoviruses from Hungary. The isolates were identified in 2016; these isolates were compared with earlier Hungarian turkey reovirus strains and turkey reoviruses isolated in the 2010s in the United States. Gene-wise sequence and phylogenetic analyses identified the cell-receptor binding protein and the main neutralization antigen, σC, to be the most conserved. The most genetically diverse gene was another surface antigen coding gene, μB. This gene was shown to undergo frequent reassortment among chicken and turkey origin reoviruses. Additional reassortment events were found primarily within members of the homologous turkey reovirus clade. Our data showed evidence for low variability among strains isolated from independent outbreaks, a finding that suggests a common source of turkey reoviruses in Hungarian turkey flocks. Given that commercial vaccines are not available, identification of the source of these founder virus strains would permit a more efficient prevention of disease outbreaks before young birds are settled to fattening facilities.

Nelson Bay Reovirus Isolated from Bats and Blood-Sucking Arthropods Collected in Yunnan Province, China

Nelson Bay reovirus (NBV) is an emerging zoonotic virus that can cause acute respiratory disease in humans. These viruses are mainly discovered in Oceania, Africa, and Asia, and bats have been identified as their main animal reservoir. However, despite recent expansion of diversity for NBVs, the transmission dynamics and evolutionary history of NBVs are still unclear. This study successfully isolated two NBV strains (MLBC1302 and MLBC1313) from blood-sucking bat fly specimens (Eucampsipoda sundaica) and one (WDBP1716) from the spleen specimen of a fruit bat (Rousettus leschenaultii), which were collected at the China-Myanmar border area of Yunnan Province. Syncytia cytopathic effects (CPE) were observed in BHK-21 and Vero E6 cells infected with the three strains at 48 h postinfection. Electron micrographs of ultrathin sections showed numerous spherical virions with a diameter of approximately 70 nm in the cytoplasm of infected cells. The complete genome nucleotide sequence of the viruses was determined by metatranscriptomic sequencing of infected cells. Phylogenetic analysis demonstrated that the novel strains were closely related to Cangyuan orthoreovirus, Melaka orthoreovirus, and human-infecting Pteropine orthoreovirus HK23629/07. Simplot analysis revealed the strains originated from complex genomic reassortment among different NBVs, suggesting the viruses experienced a high reassortment rate. In addition, strains successfully isolated from bat flies also implied that blood-sucking arthropods might serve as potential transmission vectors. IMPORTANCE Bats are the reservoir of many viral pathogens with strong pathogenicity, including NBVs. Nevertheless, it is unclear whether arthropod vectors are involved in transmitting NBVs. In this study, we successfully isolated two NBV strains from bat flies collected from the body surface of bats, which implies that they may be vectors for virus transmission between bats. While the potential threat to humans remains to be determined, evolutionary analyses involving different segments revealed that the novel strains had complex reassortment histories, with S1, S2, and M1 segments highly similar to human pathogens. Further experiments are required to determine whether more NBVs are vectored by bat flies, their potential threat to humans, and transmission dynamics.

Characterization and pathogenicity evaluation of recombinant novel duck reovirus isolated from Southeast China

The novel duck reovirus (NDRV) emerged in southeast China in 2005. The virus causes severe liver and spleen hemorrhage and necrosis in various duck species, bringing serious harm to waterfowl farming. In this study, three strains of NDRV designated as NDRV-ZSS-FJ20, NDRV-LRS-GD20, and NDRV-FJ19 were isolated from diseased Muscovy ducks in Guangdong and Fujian provinces. Pairwise sequence comparisons revealed that the three strains were closely related to NDRV, with nucleotide sequence identities for 10 genomic fragments ranging between 84.8 and 99.8%. In contrast, the nucleotide sequences of the three strains were only 38.9–80.9% similar to the chicken-origin reovirus and only 37.6–98.9% similar to the classical waterfowl-origin reovirus. Similarly, phylogenetic analysis revealed that the three strains clustered together with NDRV and were significantly different from classical waterfowl-origin reovirus and chicken-origin reovirus. In addition, the analyses showed that the L1 segment of the NDRV-FJ19 strain was a recombinant of 03G and J18 strains. Experimental reproduction of the disease showed that the NDRV-FJ19 strain was pathogenic to both ducks and chickens and could lead to symptoms of hemorrhage and necrosis in the liver and spleen. This was somewhat different from previous reports that NDRV is less pathogenic to chickens. In conclusion, we speculated that the NDRV-FJ19 causing duck liver and spleen necrosis is a new variant of a duck orthoreovirus that is significantly different in pathogenicity from any previously reported waterfowl-origin orthoreovirus.

Epidemiological Analysis of Avian Reovirus in China and Research on the Immune Protection of Different Genotype Strains from 2019 to 2020

Avian reovirus (ARV) is the primary pathogen responsible for viral arthritis. In this study, 2340 samples with suspected viral arthritis were collected from 2019 to 2020 in 16 provinces of China to investigate the prevalence of ARV in China and to characterize the molecular genetic evolution of epidemic strains. From 113 samples analyzed by RT-PCR, 46 strains of avian reovirus were successfully isolated and identified. The genetic evolution of the σC gene showed that 46 strains were distributed in 1-5 branches, with the largest number of strains in branches 1 and 2. The σC gene homology among the strains was low, with approximately 62% homology in branches 4 and 5 and about 55% in the remaining branches. The strains circulating during the ARV epidemic in different provinces were distributed in different branches. The SPF chickens were immunized with inactivated vaccines containing strains from branches 1 and 4 to analyze the cross-immune protection elicited by different branches of ARV strains. A challenge protection test was performed using strains in branches 1, 2, 4, and 5. Our results showed that inactivated vaccines containing strains from branches 1 and 4 could fully protect from strains in branches 1, 4, and 5. The results of this study revealed the genetic diversity among the endemic strains of ARV in China from 2019 to 2020. Each genotype strain elicited partial cross-protection, providing a scientific basis for the prevention and control of ARV.

Avian Reoviruses in Poultry Farms from Brazil

Avian reovirus (ARV) is highly disseminated in commercial Brazilian poultry farms, causing arthritis/tenosynovitis, runting-stunting syndrome, and malabsorption syndrome in different meat- and egg-type birds (breeders, broilers, grillers, and layers). In Brazil, ARV infection was first described in broilers in the 1970s but was not considered an important poultry health problem for decades. A more concerning outcome of field infections has been observed in recent years, including condemnations at slaughterhouses because of the unsightly appearance of chicken body parts, mainly the legs. Analyses of the performance of poultry flocks have further evidenced economic losses to farms. Genetic and antigenic characterization of ARV field strains from Brazil demonstrated a high diversity of lineages circulating in the entire country, including four of the five main phylogenetic groups previously described (I, II, III, and V). It is still unclear if all of them are associated with different diseases affecting flocks' performance in Brazilian poultry. ARV infections have been controlled in Brazilian poultry farms by immunization of breeders and young chicks with classical commercial live vaccine strains (S1133, 1733, 2408, and 2177) used elsewhere in the Western Hemisphere. However, genetic and antigenic variations of the field isolates have prevented adequate protection against associated diseases, so killed autogenous vaccines are being produced from isolates obtained on specific farms. In conclusion, ARV field variants are continuously challenging poultry farming in Brazil. Epidemiological surveillance combined with molecular biological analyses from the field samples, as well as the development of vaccine strains directed toward the ARV circulating variants, are necessary to control this economically important poultry pathogen.

Genetic diversity, reassortment, and recombination of mammalian orthoreoviruses from Japanese porcine fecal samples

Mammalian orthoreoviruses (MRVs) are non-enveloped double-stranded RNA viruses with a broad host range. MRVs are prevalent worldwide, and in Japan, they have been isolated from various hosts, including humans, dogs, cats, wild boars, and pigs, and they have also been found in sewage. However, Japanese porcine MRVs have not been genetically characterized. While investigating porcine enteric viruses including MRV, five MRVs were isolated from the feces of Japanese pigs using MA104 cell culture. Genetic analysis of the S1 gene revealed that the Japanese porcine MRV isolates could be classified as MRV-2 and MRV-3. Whole genome analysis showed that Japanese porcine MRVs exhibited genetic diversity, although they shared sequence similarity with porcine MRV sequences in the DDBJ/EMBL/GenBank database. Several potential intragenetic reassortment events were detected among MRV strains from pigs, sewage, and humans in Japan, suggesting zoonotic transmission. Furthermore, homologous recombination events were identified in the M1 and S1 genes of Japanese porcine MRV. These findings imply that different strains of Japanese porcine MRV share a porcine MRV genomic backbone and have evolved through intragenetic reassortment and homologous recombination events.

Isolation and Genomic Characterization of Avian Reovirus From Wild Birds in South Korea

Avian reoviruses (ARVs) cause severe arthritis, tenosynovitis, pericarditis, and depressed growth in chickens, and these conditions have become increasingly frequent in recent years. Studies on the role of wild birds in the epidemiology of ARVs are insufficient. This study provides information about currently circulating ARVs in wild birds by gene detection using diagnostic RT-PCR, virus isolation, and genomic characterization. In this study, we isolated and identified 10 ARV isolates from 7,390 wild birds' fecal samples, including migratory bird species (bean goose, Eurasian teal, Indian spot-billed duck, and mallard duck) from 2015 to 2019 in South Korea. On comparing the amino acid sequences of the σC-encoding gene, most isolates, except A18-13, shared higher sequence similarity with the commercial vaccine isolate S1133 and Chinese isolates. However, the A18-13 isolate is similar to live attenuated vaccine av-S1133 and vaccine break isolates (SD09-1, LN09-1, and GX110116). For the p10- and p17-encoding genes, all isolates have identical fusion associated small transmembrane (FAST) protein and nuclear localization signal (SNL) motif to chicken-origin ARVs. Phylogenetic analysis of the amino acid sequences of the σC-encoding gene revealed that all isolates were belonged to genotypic cluster I. For the p10- and p17-encoding genes, the nucleotide sequences of all isolates indicated close relationship with commercial vaccine isolate S1133 and Chinese isolates. For the σNS-encoding gene, the nucleotide sequences of all isolates indicated close relationship with the Californian chicken-origin isolate K1600657 and belonged to chicken-origin ARV cluster. Our data indicates that wild birds ARVs were derived from the chicken farms. This finding suggests that wild birds serve as natural carriers of such viruses for domestic poultry.

Isolation and Molecular Characteristics of a Novel Recombinant Avian Orthoreovirus From Chickens in China

In recent years, the emergence of avian orthoreovirus (ARV) has caused significant losses to the poultry industry worldwide. In this study, a novel ARV isolate, designated as AHZJ19, was isolated and identified from domestic chicken with viral arthritis syndrome in China. AHZJ19 can cause typical syncytial cytopathic effect in the chicken hepatocellular carcinoma cell line, LMH. High-throughput sequencing using Illumina technology revealed that the genome size of AHZJ19 is about 23,230 bp, which codes 12 major proteins. Phylogenetic tree analysis found that AHZJ19 was possibly originated from a recombination among Hungarian strains, North American strains, and Chinese strains based on the sequences of the 12 proteins. Notably, the σC protein of AHZJ19 shared only about 50% homology with that of the vaccine strains S1133 and 1733, which also significantly differed from other reported Chinese ARV strains. The isolation and molecular characteristics of AHZJ19 provided novel insights into the molecular epidemiology of ARV and laid the foundation for developing efficient strategies for control of ARV in China.

Discovery of a novel recombinant avian orthoreovirus in China

In mid-2020, using next-generation sequencing (NGS) technology, we identified a recombinant cluster 2 avian orthoreovirus (ARV) variant named PHC-2020-0545, isolated from tendons of 33-day-old broilers with leg swelling in China. Complete genomic sequencing and analyses demonstrated that the isolate was genetically significantly distinct from known ARV strains in M1 and M3 genes and its σC coding gene had an extremely high variability, compared with the identified ARV strains grouped into other genotyping cluster. Further analysis showed that many base substitutions were silent and non-silent substitutions are most likely to occur in the first positions of codons. Multiple segmental recombination, intra-segmental recombination and accumulation of point mutations might contribute to the emergence of this isolate. The PHC-2020-0545 strain had a strong replication ability in 1-day-old broilers, and mainly affected the movement, digestion and metabolism of broilers. In addition, the infection route of the isolate is related to its pathogenicity to broilers. Therefore, combined with its unique genetic characteristics and potential origin, we determined that the PHC-2020-0545 field strain is a novel recombinant ARV strain, which has certain reference value for the preparation and evaluation of new vaccines.

Isolation and characterization of mammalian orthoreovirus type 3 from a fecal sample from a wild boar in Japan

Mammalian orthoreoviruses (MRVs) have been identified in various mammalian species, including humans, bats, and pigs. However, isolation and complete genome sequences of MRVs from wild boars have not yet been reported. In this study, we isolated, sequenced, and analyzed an MRV from a free-living wild boar in Japan using the porcine-sapelovirus-resistant cell line N1380. Complete and empty virus particles were obtained from the N1380 cell culture supernatants, and complete genome sequences were obtained from complete virus particles. Sequence analysis revealed that the isolated MRV, named TY-14, could be classified as MRV3 and had a close genetic relationship to an MRV2 isolate from a lion in a Japanese zoo (L2, L3, and M3 genes) and a human MRV2 isolate from Japan (S2 gene). Phylogenetic analysis showed that TY-14 clustered only with bat MRVs in the M1 phylogenetic tree but formed a cluster with several animal MRVs in the M2 and S3 phylogenetic trees and branched independently in the L1, S1, and S4 phylogenetic trees, suggesting a genetic relationship to viruses of unknown origin. Recombination events were identified in the M2 gene. These results suggest that TY-14 was generated by reassortment and recombination events involving MRVs circulating in Japan, viruses from bats, and other viruses of unknown origin.

Genomic sequences and pathogenic characteristics of two variant duck reoviruses associated with spleen necrosis

Emerging variant novel duck reovirus (NDRV) strains that cause spleen swelling and necrosis have seriously threatened the waterfowl industry since 2017. However, there is no report about the complete genomic sequence of emerging variant strains isolated from Cherry valley ducks. In this study, we acquired the complete genome sequences of two variant NDRV strains, SD19/6201 and SD19/6202, and analyzed their genetic and evolutionary relationship with other orthoreoviruses. The phylogenetic analysis of σC showed that all the Chinese NDRVs were clustered into two distinct branches. The SD19/6201 strain located in branch I with most of the Chinese NDRVs, while SD19/6202 was clustered in branch II with significantly different from the existing strains. Within the branch I, the NDRVs isolated in 2017 and thereafter clustered in a new subgroup. Comparison analysis of σC amino acid sequences indicated that ten amino acid differences were found between SD19/6201 and SD19/6202. Apart from the SD19/6201 and SD19/6202 strains, isolates in 2017 and thereafter had specific mutations at residues 132A, 138R, 158H, and 258A. These two NDRV strains showed different pathogenicity in SPF duck embryos and ducks. The viral loads in the spleen of infected ducks were significantly higher than those of other organs, which might be the reason why NDRV could cause obvious spleen necrosis in ducks. This study will help us to formulate effective prevention and control strategies against NDRV and enrich our understanding of the intra- and inter-species relationships of orthoreoviruses.

Establishment of a Real-Time Recombinase Polymerase Amplification Assay for the Detection of Avian Reovirus

Avian reovirus (ARV) infection results in multiple disease manifestations in chicken. A rapid detection method will contribute to early diagnosis and control of the virus infection. The recombinase polymerase amplification (RPA) technology is a nucleic acid amplification method which is experiencing rapid development. In present study, a real-time reverse transcription (RT)-RPA assay was developed for the detection of ARV. The limit of detection of the real-time RT-RPA was 10² copies/μL of ARV genomic RNA standard in 95% of cases. The RT-RPA assay also exhibited remarkable specificity. When the nucleic acids of CRV and other common avian pathogens were subjected to the RT-RPA test, only ARV tested positive, all the other pathogens tested negative. Furthermore, the practicality of the RT-RPA assay in field was confirmed by testing 86 clinical samples. The clinical samples were also detected by qRT-PCR. The detection result by RT-RPA was 96.5% agreement with that of qRT-PCR. As a result of the simplicity and convenience of the assay with high sensitivity and specificity, the probe-based RT-RPA will be an alternative diagnostic assay for the detection of ARV in resource-limited settings.

Molecular characterization of an emerging reassortant mammalian orthoreovirus in China

Mammalian orthoreoviruses (MRVs) infect almost all mammals, and there are some reports on MRVs in China. In this study, a novel strain was identified, which was designated as HLJYC2017. The results of genetic analysis showed that MRV HLJYC2017 is a reassortant strain. According to biological information analysis, different serotypes of MRV contain specific amino acid insertions and deletions in the σ1 protein. Neutralizing antibody epitope analysis revealed partial cross-protection among MRV1, MRV2, and MRV3 isolates from China. L3 gene recombination in MRV was identified for the first time in this study. The results of this study provide valuable information on MRV reassortment and evolution.

Sequencing and phylogenetic analysis of partial S1 genes of avian orthoreovirus isolates in Shandong province during 2015-2017

Outbreaks of avian orthoreovirus (ARV) infection with primary symptoms of arthritis/tenosynovitis syndrome have been occurring more frequently in broiler flocks in China in recent years. This study aimed to investigate the genetic characteristics of ARV field strains in broiler flocks exhibiting arthritis/tenosynovitis syndrome from 9 cities in Shandong province during 2015 to 2017. A total of 64 synovial and tendon samples were obtained from broilers with significant arthritis/tenosynovitis syndrome, and 21 ARV field strains were obtained. Phylogenetic analysis of the σC nt/aa sequences revealed that only 4 isolates were clustered in genotype I, including vaccine strains S1133, 1733, and most of the ARV field strains identified previously in China. Eleven and 6 ARV field isolates were identified in genotypes II and V, sharing 70.9 to 76.0% and 53.0 to 55.2% nt identities with the vaccine strains, respectively. Previous studies in China have not reported these 2 serotypes of field strains, and prevalence of these ARV variants may be increasing in Chinese broiler flocks. Results of this study suggest that large-scale investigation of epidemic ARV should be conducted to explore the genetic diversity of ARV field isolates in China.

Characterization of Monoclonal Antibodies against σA Protein and Cross-Reactive Epitope Identification and Application for Detection of Duck and Chicken Reovirus Infections

Although σA is an important major core protein of duck reovirus (DRV), the B-cell epitopes of this protein remain unknown to reseacrhers. Six monoclonal antibodies (MAbs) (1A7, 3F4, 5D2, 4E2, 3C7, and 2B7) were developed by using prokaryotic-expressed recombinant His-σA protein. Five of six MAbs (1A7, 3F4, 4E2, 3C7, and 2B7) reacted with His-σA protein in a conformation-independent manner, while 5D2 reacted with σA in a conformation-dependent manner. Immunofluorescence assays showed that the MAbs could specifically bind to DRV infected BHK-21 cells. The MAbs were delineated as three groups by a competitive binding assay. By using 12-mer peptide phage display and mutagenesis, MAb 4E2 was identified to recognize minimal epitope ⁵⁶EAPYPG⁶¹ and MAb 1A7 recognize ³⁴¹WVV/MAGLI/V³⁴⁷, residues ³⁴¹V/M and ³⁴⁷I/V are replaceable. Dot blotting and sequence analysis confirmed that EAPYPG and WVV/MAGLI/V are cross-reactive epitopes in both DRV and avian reovirus (ARV). An enzyme-linked immunosorbent assay (ELISA) based on two expressed EAPYPG and WVVAGLI as antigen demonstrated its diagnostic potential by specific reacting with serum samples from DRV- or ARV-infected birds. Based on these observations, an epitope-based ELISA could be potentially used for DRV or ARV surveillance. These findings provide insights into the organization of epitopes on σA protein that might be valuable for the development of epitope-based serological diagnostic tests for DRV and ARV infection.

Pathogenicity and genomic characterization of a novel avian orthoreovius variant isolated from a vaccinated broiler flock in China

Avian orthoreovirus (ARV) infections of broiler flocks cause arthritis/tenosynovitis syndrome and significant economic losses. ARV variants were detected in the USA and Canada. Viral arthritis/tenosynovitis syndrome has occurred frequently in China in recent years. In this study, a variant ARV strain associated with viral arthritis/tenosynovitis syndrome was isolated from broilers and designated as LY383. Genomic sequence and phylogenetic analysis of the σC nucleic acid and amino acid sequences revealed that the isolate was closely related to ARV field strains Reo/PA/Layer/01224B/14, Reo/PA/Broiler/1551/13, GA/14602/2014, GA/13569/2013 and GA/13542/2013, in cluster V, but distinct from most Chinese field strains or commercial vaccine strains. Experimental challenge showed that the isolate could cause arthritis/tenosynovitis syndrome in broilers, which possessed a high level of maternal antibodies induced by commercial ARV vaccines (S1133, 1733 and T98). Furthermore, viral nucleic acid could be detected in cloacal swabs of all challenged birds throughout the entire test from 5 dpi onward. These results suggest that a novel ARV genotype emerges and might become prevalent in broiler flocks in China. RESEARCH HIGHLIGHTS A variant avian orthoreovirus was isolated from a vaccinated broiler flock in North China. The ARV field strain was distinct from previous China-origin ARV isolates and vaccine strains. The current commercial ARV vaccine could not provide effective protection of broilers against the field isolate infection. These findings indicated that variant ARV field strains might become frequent in broiler flocks in China and effective measures should be conducted to prevent and control the disease.