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

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

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

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

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

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

Complete genome sequences of Sathuperi and Shamonda viruses isolated in Japan.

Sathuperi virus (SATV) and Shamonda virus (SHAV) (family Peribunyaviridae, genus Orthobunyavirus, species Schmallenberg orthobunyavirus) have been suggested to cause congenital abnormalities in ruminants. In this study, we determined the complete genome sequences of SATV KSB-6/C/02 and SHAV KSB-2/C/08 strains, which were obtained from Culicoides biting midges in Japan, by next-generation sequencing and Sanger sequencing. The 3'- and 5'-untranslated region sequences of the M segment of SHAV KSB-2/C/08 strains are distinctly different from those of SATV KSB-6/C/02 and Schmallenberg viruses. This study provides the genome characterization of Japanese strains of SATV and SHAV and presented the genetic variation in the untranslated regions of Schmallenberg orthobunyavirus M segments.

Complete genome sequences of epizootic hemorrhagic disease virus serotypes 5 and 6 isolated in Japan.

Here, we report the complete genome sequences of epizootic hemorrhagic disease (EHD) virus serotypes 5 (EHDV-5) and 6 (EHDV-6) isolated in the Yaeyama Islands of Okinawa Prefecture, Japan. The EHDV-5 strain, ON-11/E/16, which was isolated in 2016, is, to our knowledge, the second EHDV-5 strain to be isolated after the first was isolated in Australia in 1977. In each of the genome segments, ON-11/E/16 was most closely related to EHDV strains of different serotypes isolated in Australia and Japan. Our results support the idea that various serotypes of EHDV have been circulating while causing reassortment in the Asia-Pacific region. In all genome segments, the EHDV-6 strain, ON-3/E/14, which was isolated in 2014, was highly similar to EHDV-6 strain HG-1/E/15, which was detected in affected cattle during the EHD epidemic in Hyogo prefecture in 2015. Therefore, these two EHDV-6 strains, ON-3/E/14 and HG-1/E/15, may have the same origin. However, it is unclear whether EHDV-6 was transmitted directly between the locations where those strains were isolated/detected (approx. 1,500 km apart) or whether EHDV-6 strains of the same origin entered each location at different times. In addition, we cannot rule out the possibility that EHDV-6 infection has spread unnoticed through asymptomatic cattle in other areas of Japan. Therefore, further investigation into EHDV infection in cattle is necessary for a more detailed understanding of the ecology of EHDV in Japan.

Whole-genome sequence analysis of a novel orthobunyavirus isolated in Japan in the 1980s.

Two viruses isolated from Culicoides biting midges in Japan and preserved in a frozen state for over three decades were genetically characterized by next-generation sequencing. The viruses have a tripartite RNA genome with the typical coding strategy of orthobunyaviruses. They also share a high level of genetic similarity and are thus regarded as isolates of the same virus. Pairwise sequence comparisons and phylogenetic analysis including viruses of the Simbu serogroup demonstrated that the new viruses are members of clade A of this serogroup. In addition, a discrepancy in the phylogenetic trees indicated that a genetic reassortment had occurred in the evolution of the studied viruses. The L protein of the virus reported here showed no more than 94.6% amino acid sequence identity to that of any other Simbu serogroup virus, indicating that it should be regarded as a novel virus according to a criterion for species definition in the genus Orthobunyavirus. Therefore, this novel virus is tentatively named 'Taniyama virus' based on the location where the infected midges were collected.

Current research and future directions for realizing the ideal One-Health approach: A summary of key-informant interviews in Japan and a literature review.

The COVID-19 pandemic has highlighted the importance of the One Health (OH) approach, which considers the health of humans, animals, and the environment in preventing future pandemics. A wide range of sustainable interdisciplinary collaborations are required to truly fulfill the purpose of the OH approach. It is well-recognized, however, that such collaborations are challenging. In this study, we undertook key-informant interviews with a panel of stakeholders from Japan to identify their perceived needs and challenges related to OH research. This panel included scientists, government officials, journalists, and industry stakeholders. By combining a thematic analysis of these interviews and a literature review, we summarized two key themes pertinent to the effective implementation of OH research: types of required research and systems to support that research. As a technological issue, interviewees suggested the importance of research and development of methodologies that can promote the integration and collaboration of research fields that are currently fragmented. An example of such a methodology would allow researchers to obtain high-resolution metadata (e.g. ecological and wildlife data) with high throughput and then maximize the use of the obtained metadata in research, such as in environmental DNA analysis, database construction, or the use of computational algorithms to find novel viral genomes. In terms of systems surrounding OH research, some interviewees stressed the importance of creating a sustainable research system, such as one that has continuous budget support and allows researchers to pursue their academic careers and interests. These perceptions and challenges held by Japanese stakeholders may be common to others around the world. We hope this review will encourage more researchers and others to work together to create a resilient society against future pandemics.

Characterization of Keterah orthonairovirus and evaluation of therapeutic candidates against Keterah orthonairovirus infectious disease.

The species Keterah orthonairovirus is a member of the genus Orthonairovirus. Few studies have focused on this species, and there remains no treatment for Issyk-Kul fever, an infectious disease caused by a Keterah orthonairovirus. This study was performed to characterize this species using two viruses, Issyk-Kul virus (ISKV) and Soft tick bunyavirus (STBV), in cell culture and type I interferon receptor knockout (IFNAR-/-) mice and to evaluate the efficacy of serum transfusion using a mouse model of ISKV infection. The two viruses replicated in many kinds of mammal- and tick-derived cell lines but showed few different characteristics in tropism and antigenicity against anti-viral sera in cell culture. Neither virus caused clinical signs in wild-type mice, but both caused lethal infection in IFNAR-/- mice. ISKV caused more acute death than STBV in IFNAR-/- mice. In both viral infections in IFNAR-/- mice, macroscopic abnormalities were prominent in the liver. Similar levels of viral genome between ISKV- and STBV-infected IFNAR-/- mice were observed in blood, liver, lymphoid tissues and adrenal gland at moribund stages. Hematologic abnormalities in IFNAR-/- mice infected with these viruses, including leukopenia and thrombocytopenia, and biochemical abnormalities indicating liver damage were prominent. In addition, blood levels of many kinds of cytokines and chemokines such as granulocyte colony-stimulating factor, interleukin-6, tumor necrosis factor-α, interferon gamma-induced protein 10 and monocyte chemoattractant protein-1 were elevated. ISKV-immunized serum transfusion after infection delayed the time to death of IFNAR-/- mice. Thus, the present study showed that the species Keterah orthonairovirus could proliferate in most mammal-derived cell lines and cause severe liver lesions and death in IFNAR-/- mice and that serum transfusion might be effective in treatment against Issyk-Kul fever.

Isolation of Culicoides- and Mosquito-Borne Orbiviruses in the Southwestern Islands of Japan Between 2014 and 2019.

The circulation of arboviruses in livestock ruminants has often gone unrecognized owing to the fact that a significant percentage of arboviruses probably induce subclinical infections and/or negligible symptoms in infected animals. To determine the current situation of arbovirus circulation in the Yaeyama Islands, attempts to isolate viruses from bovine blood samples collected between 2014 and 2019 have been made. In total, 308 blood samples were collected during the study period, and 43 of them induced cytopathic effects (CPEs) in cell cultures. The identification of the CPE agents was performed by reported RT-PCR assays and a high-throughput analysis with a next-generation sequencing platform. The obtained viruses consisted of an orthobunyavirus (Peaton virus), Culicoides-borne orbiviruses (bluetongue virus serotypes 12 and 16, epizootic hemorrhagic disease virus [EHDV] serotypes 5, 6, and 7, D'Aguilar virus, and Bunyip Creek virus), and potential mosquito-borne orbiviruses (Yunnan orbivirus, Guangxi orbivirus, and Yonaguni orbivirus). Most of the orbiviruses were recovered from washed blood cells with mosquito cell cultures, suggesting that this combination was more efficient than other combinations such as plasma/blood cells and hamster cell lines. This marked the first time that the isolation of EHDV serotypes 5 and 6 and three potential mosquito-borne orbiviruses was recorded in Japan, showing a greater variety of orbiviruses on the islands than previously known. Genetic analysis of the isolated orbiviruses suggested that the Yaeyama Islands and its neighboring regions were epidemiologically related. Some of the viruses, especially the potential mosquito-borne orbiviruses, were isolated during several consecutive years, indicating their establishment on the islands.

Genomic analysis of putative novel serotypes of Tibet orbivirus isolated in Japan.

Tibet orbivirus (TIBOV) was initially isolated in Tibet in 2009 and subsequently in Guangdong, Hunan, and Yunnan, China. We document the first isolation of TIBOV outside of China: two TIBOV isolates from Culicoides collected in 2009 and 2010 in Kagoshima, Japan. Their complete genome sequences were also determined. Our results suggest that the two virus isolates are of novel serotypes, evident by variability within genome segment 2 encoding VP2. These new putative TIBOV serotypes will help with future virus surveillance and with the evaluation of its potential to cause disease in domestic ruminants.

Systemic and intestinal porcine epidemic diarrhea virus-specific antibody response and distribution of antibody-secreting cells in experimentally infected conventional pigs.

Porcine epidemic diarrhea (PED) is a coronavirus disease characterized by the rapid spread of severe diarrhea among pigs. PED virus (PEDV) infects and replicates mainly in the epithelial cells of the duodenum, jejunum, ileum and colon. Serum or mucosal IgA antibody levels have been used to predict both vaccine efficacy and the level of protective immunity to enteric infectious diseases in individuals or herds. Details of the B-cell immune response upon PEDV infection, such as the systemic and mucosal PEDV IgA antibody response, the distribution of IgA antibody-secreting cells (ASCs), and their role in virus clearance are not yet clear. In this experimental infection study, we observed similar fluctuations in PEDV IgA antibody levels in serum and intestinal contents of the upper and lower jejunum and ileum, but not fecal samples, over the 4-week experimental course. ASCs that actively secrete PEDV IgA antibody without in vitro stimulation were distributed mainly in the upper jejunum, whereas memory B cells that showed enhanced PEDV IgA antibody production upon in vitro stimulation were observed in mesenteric lymph nodes and the ileum. Our findings will contribute to the development of effective vaccines and diagnostic methods for PEDV.

Identification and characterization of a novel orbivirus, Yonaguni orbivirus, isolated from cattle on the westernmost island of Japan.

A novel orbivirus (genus Orbivirus, family Reoviridae), designated Yonaguni orbivirus (YONOV), was isolated from bovine blood collected on a subtropical island of Japan in 2015. The YONOV genome (20,054 nucleotides in total) has a coding arrangement similar to those of mosquito-borne orbiviruses. YONOV has a close genetic relationship to mosquito-borne orbiviruses, especially to Mobuck virus (MBV), which was isolated in North America. However, YONOV and MBV share less than 74% nucleotide sequence identity in the major subcore protein (T2) coding sequence, which satisfies the criterion for species demarcation. It is still uncertain whether YONOV should be assigned to a novel species in the genus Orbivirus.

Terminal Genome Sequences of the Soft Tick Bunyavirus.

The complete genome sequence of the soft tick bunyavirus (STBV) was obtained using the Sanger sequencing technique. Comparison with other viral sequences revealed that STBV has unique sequences in the terminal regions that are highly conserved among the genus Orthonairovirus.

Bovine viral diarrhea virus non-structural protein NS4B induces autophagosomes in bovine kidney cells.

Bovine viral diarrhea virus (BVDV) is an important pathogen in cattle that causes economic losses in livestock industries. Autophagy is an essential cell system for the maintenance of homeostasis and is induced by various triggers, including infection by viruses. BVDV infection leads to autophagy in order to enhance its replication in cells. In this study, we investigated the effect of BVDV non-structural proteins on the induction of autophagosomes. We found that NS4B alone could induce autophagosomes, suggesting a novel and important function of NS4B in BVDV replication.

The Development of a Novel Diagnostic Assay That Utilizes a Pseudotyped Vesicular Stomatitis Virus for the Detection of Neutralizing Activity against Crimean-Congo Hemorrhagic Fever Virus.

Crimean-Congo hemorrhagic fever virus is a risk group 4 pathogen, which mandates the use of maximum containment facilities, often termed biosafety level 4 or containment level 4 when working with infectious materials. Diagnostic and research work involving live viruses in such laboratories is time-consuming and inconvenient, resulting in delays. Herein, we show that serum neutralizing activity against the virus can be measured in low-containment laboratories using a pseudotyped virus.

Severe Fever with Thrombocytopenia Syndrome Virus Antigen Detection Using Monoclonal Antibodies to the Nucleocapsid Protein.

BACKGROUND: Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne infectious disease with a high case fatality rate, and is caused by the SFTS virus (SFTSV). SFTS is endemic to China, South Korea, and Japan. The viral RNA level in sera of patients with SFTS is known to be strongly associated with outcomes. Virological SFTS diagnosis with high sensitivity and specificity are required in disease endemic areas. METHODOLOGY/PRINCIPAL FINDINGS: We generated novel monoclonal antibodies (MAbs) against the SFTSV nucleocapsid (N) protein and developed a sandwich antigen (Ag)-capture enzyme-linked immunosorbent assay (ELISA) for the detection of N protein of SFTSV using MAb and polyclonal antibody as capture and detection antibodies, respectively. The Ag-capture system was capable of detecting at least 350-1220 TCID50/100 µl/well from the culture supernatants of various SFTSV strains. The efficacy of the Ag-capture ELISA in SFTS diagnosis was evaluated using serum samples collected from patients suspected of having SFTS in Japan. All 24 serum samples (100%) containing high copy numbers of viral RNA (>105 copies/ml) showed a positive reaction in the Ag-capture ELISA, whereas 12 out of 15 serum samples (80%) containing low copy numbers of viral RNA (<105 copies/ml) showed a negative reaction in the Ag-capture ELISA. Among these Ag-capture ELISA-negative 12 samples, 9 (75%) were positive for IgG antibodies against SFTSV. CONCLUSIONS: The newly developed Ag-capture ELISA is useful for SFTS diagnosis in acute phase patients with high levels of viremia.

Analysis of the entry mechanism of Crimean-Congo hemorrhagic fever virus, using a vesicular stomatitis virus pseudotyping system.

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne disease causing severe hemorrhagic symptoms with a nearly 30 % case-fatality rate in humans. The experimental use of CCHF virus (CCHFV), which causes CCHF, requires high-biosafety-level (BSL) containment. In contrast, pseudotyping of various viral glycoproteins (GPs) onto vesicular stomatitis virus (VSV) can be used in facilities with lower BSL containment, and this has facilitated studies on the viral entry mechanism and the measurement of neutralizing activity, especially for highly pathogenic viruses. In the present study, we generated high titers of pseudotyped VSV bearing the CCHFV envelope GP and analyzed the mechanisms involved in CCHFV infection. A partial deletion of the CCHFV GP cytoplasmic domain increased the titer of the pseudotyped VSV, the entry mechanism of which was dependent on the CCHFV envelope GP. Using the pseudotype virus, DC-SIGN (a calcium-dependent [C-type] lectin cell-surface molecule) was revealed to enhance viral infection and act as an entry factor for CCHFV.

Phylogenetic and Geographic Relationships of Severe Fever With Thrombocytopenia Syndrome Virus in China, South Korea, and Japan.

BACKGROUND: Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne acute infectious disease caused by the SFTS virus (SFTSV). SFTS has been reported in China, South Korea, and Japan as a novel Bunyavirus. Although several molecular epidemiology and phylogenetic studies have been performed, the information obtained was limited, because the analyses included no or only a small number of SFTSV strains from Japan. METHODS: The nucleotide sequences of 75 SFTSV samples in Japan were newly determined directly from the patients' serum samples. In addition, the sequences of 7 strains isolated in vitro were determined and compared with those in the patients' serum samples. More than 90 strains that were identified in China, 1 strain in South Korea, and 50 strains in Japan were phylogenetically analyzed. RESULTS: The viruses were clustered into 2 clades, which were consistent with the geographic distribution. Three strains identified in Japan were clustered in the Chinese clade, and 4 strains identified in China and 26 in South Korea were clustered in the Japanese clade. CONCLUSIONS: Two clades of SFTSV may have evolved separately over time. On rare occasions, the viruses were transmitted overseas to the region in which viruses of the other clade were prevalent.

Effects of ribavirin on severe fever with thrombocytopenia syndrome virus in vitro.

Severe fever with thrombocytopenia syndrome (SFTS) is a disease with a high case fatality rate that is caused by infection with the recently identified tick-borne SFTS virus (SFTSV), for which there are no specific countermeasures. We examined the effects of ribavirin and mizoribine, which are nucleoside analogue drugs with broad antiviral activities, on SFTSV proliferation in vitro. When 3 cell lines were treated with these drugs before and during infection with a Chinese SFTSV strain, the 99% effective concentrations (EC99) of ribavirin were 19-64 µg/ml (78-262 µM); in contrast, the EC99 of mizoribine was >500 µg/ml (1,929 µM). Similar levels of inhibitory effects of ribavirin were observed with 4 Japanese SFTSV strains. However, when Vero cells were treated with ribavirin 3 days after inoculation, the inhibitory effect was dramatically decreased, indicating that ribavirin did not effectively reduce virus production in pre-infected cells. These results suggest that ribavirin could be used as post-exposure prophylaxis for the prevention of SFTS.