Borna disease virus RNA detected in Japanese macaques (Macaca fuscata)

Borna disease in an adult free-ranging Eurasian beaver (Castor fiber albicus)

Borna disease (BD) associated with a peracute bacterial septicaemia with Escherichia coli was diagnosed in an adult female, naturally infected, free-ranging Eurasian beaver of the subspecies Castor fiber albicus, clinically characterized by weight loss, depression, weakness and gurgled peristaltic sounds. The beaver was euthanized humanely. Necropsy and light microscopy revealed a non-purulent meningoencephalitis with typical mononuclear perivascular cuffs and parenchymal infiltrates. The diagnosis of BD was confirmed by detection of viral antigen and RNA by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). The PCR product was sequenced and cluster analysis revealed a close relationship between endemic clusters in Saxony-Anhalt. This is the first report of naturally occurring BD in a free-ranging Eurasian beaver.

Genetic stability of the open reading frame 2 (ORF2) of borna disease virus 1 (BoDV-1) distributed in cattle in Hokkaido

Borna disease virus (BoDV) is a neurotropic virus that causes several infections in humans and neurological diseases in a wide range of animals worldwide. BoDV-1 has been molecularly and serologically detected in many domestic and wild animals in Japan; however, the genetic diversity of this virus and the origin of its infection are not fully understood. In this study, we investigated BoDV-1 infection and genetic diversity in samples collected from animals in Hokkaido between 2006 and 2020. The analysis was performed by focusing on the P region of BoDV-1 for virus detection. The presence of BoDV-1 RNA was observed in samples of brain tissue and various organs derived from persistently infected cattle. Moreover, after inoculation, BoDV-positive brains were isolated from neonatal rats. The gene sequences of the P region of BoDV obtained from the rat brain were in the same cluster as the P region of the virus isolated from the original bovine. Thus, genetic variation in BoDV-1 was extremely low. The phylogenetic analysis revealed that BoDV-1 isolates obtained in this study were part of the same cluster, which suggested that BoDV-1 of the same cluster was widespread among animals in Hokkaido.

Full-length genomic sequencing and characterization of Borna disease virus 1 isolates: Lessons in epidemiology

Borna disease virus 1 (BoDV-1) is a nonsegmented, negative-strand RNA virus that infects mammals including humans. BoDV-1 strains occur globally, dominate the species Mammalian 1 bornavirus, and display highly conserved genomes and persistent infection (brain, blood). Subclinical infections prevail but the rare fatal outcomes even in people need awareness and risk assessment. Although BoDV-1 strains were successfully isolated, only limited full genomic sequences are available. In this study, the entire genomes of two natural BoDV-1 isolates (Hu-H2, Equ-Cres) and one vaccine strain (DessVac) were sequenced. They were compared with 20 genomes and 20 single-gene sequences (N and P) of worldwide human strains from psychiatric and neurologic patients and animal strains from horses with Borna disease available at GenBank. Phylogenetic analyses confirmed a low divergence not exceeding 5.55%, 5.34%, and 4.94% at the genome, P-gene, and N-gene level, respectively, characteristic of BoDV-1. Human viruses tended to cluster at the country level but appeared to be independent of hosts' diseases and/or time of isolation. Notably, our data also indicated that human viruses provided individual genetic signatures but exhibited no distinct genotypes that separated them from animal strains. Sequence similarities thus occurred between different host species and distant geographic regions, supporting global BoDV-1 prevalence. Overall low genetic divergence among BoDV-1 viruses shown here also argued against zoonotic concepts, requiring further clarification beyond sequence similarities. Finally, unlike shared sequence conservation, phenotyping of natural and laboratory variants revealed that they manipulated host cells differently, underpinning the authenticity of the human BoDV-1 strains.

Viral Equine Encephalitis, a Growing Threat to the Horse Population in Europe?

Neurological disorders represent an important sanitary and economic threat for the equine industry worldwide. Among nervous diseases, viral encephalitis is of growing concern, due to the emergence of arboviruses and to the high contagiosity of herpesvirus-infected horses. The nature, severity and duration of the clinical signs could be different depending on the etiological agent and its virulence. However, definite diagnosis generally requires the implementation of combinations of direct and/or indirect screening assays in specialized laboratories. The equine practitioner, involved in a mission of prevention and surveillance, plays an important role in the clinical diagnosis of viral encephalitis. The general management of the horse is essentially supportive, focused on controlling pain and inflammation within the central nervous system, preventing injuries and providing supportive care. Despite its high medical relevance and economic impact in the equine industry, vaccines are not always available and there is no specific antiviral therapy. In this review, the major virological, clinical and epidemiological features of the main neuropathogenic viruses inducing encephalitis in equids in Europe, including rabies virus (Rhabdoviridae), Equid herpesviruses (Herpesviridae), Borna disease virus (Bornaviridae) and West Nile virus (Flaviviridae), as well as exotic viruses, will be presented.

Different inhibitory effects on the proliferation and apoptosis of human and laboratory Borna disease virus‑infected human neuroblastoma SH‑SY5Y cells in vitro

Borna disease virus (BDV) is a neurotropic and non‑cytolytic virus, which causes behavioral disorders in a wide range of warm‑blooded species. It is well established that BDV induces neurodegeneration by impairing neurogenesis and interfering with neuronal functioning in the limbic system. In the present study, the potential role of BDV infection in SH‑SY5Y cells was identified, and comparisons of two original BDV strains (the human Hu‑H1 and the laboratory Strain V) were performed to further elucidate the phenotypes of BDV pathogenesis with strain differences. Cell Counting Kit‑8 and flow cytometric analyses revealed that the two BDV strain‑infected groups exhibited marked anti‑proliferation and cell cycle arrest compared with the control group, and the Hu‑H1 strain caused more evident effects. However, the Hu‑H1 strain did not exert effects on the apoptosis of SH‑SH5Y cells, while Strain V led to a marked increase in apoptosis upon initial infection. Western blot analysis confirmed the upregulation of apoptosis regulator BAX protein and the downregulation of apoptosis regulator Bcl‑2 protein caused by the two BDV strains. The results of the present study provided evidence that infection with BDV suppressed SH‑SY5Y cellular functioning and exhibited divergent antiproliferative and apoptotic roles in cells between the two strains. The present study provided an insight for future investigation of strain differences and underlying pathomechanisms.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): Borna disease

Borna disease has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of Borna disease to be listed, Article 9 for the categorisation of Borna disease according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to Borna disease. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, Borna disease cannot be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL because there was no compliance on criterion 5 A(v). Consequently, the assessment on compliance of Borna disease with the criteria as in Annex IV of the AHL, for the application of the disease prevention and control rules referred to in Article 9(1) is not applicable, as well as which animal species can be considered to be listed for Borna disease according to Article 8(3) of the AHL.

Sero-epidemiological analysis of vertical transmission relative risk of Borna disease virus infection in dairy herds

Borna disease virus (BDV) is a virus that causes a neurological disease in domestic animals, including a variety of animal species in Japan. Few studies have examined the mode of transmission of this virus in cattle, and the exact mechanisms underlying the transmission of the virus need to be elucidated. This study aimed to examine the contribution of vertical transmission of the virus, which occurs when the virus is transmitted from the mother to offspring during gestation or birth. We used an epidemiological approach. The relative risk (RR) was calculated for cattle born to BDV sero-positive cows from farms with a higher within-herd prevalence of BDV (56.8%). We tested the sera of 1,122 dairy cattle from 24 dairy herds in Hokkaido Prefecture, Japan, for BDV infection using the ELISA and western blotting method. The overall level of BDV sero-prevalence was 22.1%. Seroprevalence was significantly higher in closed-breeding herds that do not have buying in cows (39.7%) than in farms that restock cattle by buying in cows (4.4%, P<0.01). The overall RR of BDV vertical transmission from infected mothers to their daughters was 1.86 (95% confidence interval (CI): 1.54-2.56). Our results show that vertical transmission contributes significantly to BDV transmission in the farms tested in this study.

GC-MS-Based Metabonomic Profiling Displayed Differing Effects of Borna Disease Virus Natural Strain Hu-H1 and Laboratory Strain V Infection in Rat Cortical Neurons

Borna disease virus (BDV) persists in the central nervous systems of a wide variety of vertebrates and causes behavioral disorders. Previous studies have revealed that metabolic perturbations are associated with BDV infection. However, the pathophysiological effects of different viral strains remain largely unknown. Rat cortical neurons infected with human strain BDV Hu-H1, laboratory BDV Strain V, and non-infected control (CON) cells were cultured in vitro. At day 12 post-infection, a gas chromatography coupled with mass spectrometry (GC–MS) metabonomic approach was used to differentiate the metabonomic profiles of 35 independent intracellular samples from Hu-H1-infected cells (n = 12), Strain V-infected cells (n = 12), and CON cells (n = 11). Partial least squares discriminant analysis (PLS-DA) was performed to demonstrate discrimination between the three groups. Further statistical testing determined which individual metabolites displayed significant differences between groups. PLS-DA demonstrated that the whole metabolic pattern enabled statistical discrimination between groups. We identified 31 differential metabolites in the Hu-H1 and CON groups (21 decreased and 10 increased in Hu-H1 relative to CON), 35 differential metabolites in the Strain V and CON groups (30 decreased and 5 increased in Strain V relative to CON), and 21 differential metabolites in the Hu-H1 and Strain V groups (8 decreased and 13 increased in Hu-H1 relative to Strain V). Comparative metabonomic profiling revealed divergent perturbations in key energy and amino acid metabolites between natural strain Hu-H1 and laboratory Strain V of BDV. The two BDV strains differentially alter metabolic pathways of rat cortical neurons in vitro. Their systematic classification provides a valuable template for improved BDV strain definition in future studies.

Borna disease virus phosphoprotein impairs the developmental program controlling neurogenesis and reduces human GABAergic neurogenesis

It is well established that persistent viral infection may impair cellular function of specialized cells without overt damage. This concept, when applied to neurotropic viruses, may help to understand certain neurologic and neuropsychiatric diseases. Borna disease virus (BDV) is an excellent example of a persistent virus that targets the brain, impairs neural functions without cell lysis, and ultimately results in neurobehavioral disturbances. Recently, we have shown that BDV infects human neural progenitor cells (hNPCs) and impairs neurogenesis, revealing a new mechanism by which BDV may interfere with brain function. Here, we sought to identify the viral proteins and molecular pathways that are involved. Using lentiviral vectors for expression of the bdv-p and bdv-x viral genes, we demonstrate that the phosphoprotein P, but not the X protein, diminishes human neurogenesis and, more particularly, GABAergic neurogenesis. We further reveal a decrease in pro-neuronal factors known to be involved in neuronal differentiation (ApoE, Noggin, TH and Scg10/Stathmin2), demonstrating that cellular dysfunction is associated with impairment of specific components of the molecular program that controls neurogenesis. Our findings thus provide the first evidence that a viral protein impairs GABAergic human neurogenesis, a process that is dysregulated in several neuropsychiatric disorders. They improve our understanding of the mechanisms by which a persistent virus may interfere with brain development and function in the adult.

When a virus enters the brain, it most often induces inflammation, fever, and brain injury, all signs that are indicative of acute encephalitis. Under certain conditions, however, some neurotropic viruses may cause disease in a subtler manner. The Borna disease virus (BDV) is an excellent example of this second class of viruses, as it impairs neural function without cell lysis and induces neurobehavioral disturbances. Recently, we have shown that BDV infects human neural progenitor cells (hNPCs) and impairs neurogenesis, revealing a new mechanism by which BDV may interfere with brain function. In the present study, we identify that a singled-out BDV protein called P causes similar impairment of human neurogenesis, and further show that it leads to diminution in the genesis of a particular neuronal subtype, the GABAergic neurons. We have also found that the expression of several genes involved in the generation and the maturation of neurons is dysregulated by this viral protein, which strongly suggests their implication in P-induced impairment of GABAergic neurogenesis. This study is the first to demonstrate that a viral protein interferes with human GABAergic neurogenesis, a process that is frequently impaired in neuropsychiatric disorders. It may thus contribute to elucidating the molecular bases of psychiatric disorders.

Evidence for natural Borna disease virus infection in healthy domestic animals in three areas of western China

Borna disease virus (BDV) is a non-cytolytic, neurotropic RNA virus that can infect many vertebrate species, including humans. To date, BDV infection has been reported in a range of animal species across a broad global geographic distribution. However, a systematic epidemiological survey of BDV infection in domesticated animals in China has yet to be performed. In current study, BDV RNA and antibodies in 2353 blood samples from apparently healthy animals of eight species (horse, donkey, dog, pig, rabbit, cattle, goat, sheep) from three areas in western China (Xinjiang province, Chongqing municipality, and Ningxia province) were assayed using reverse transcription qPCR (RT-qPCR) and ELISA assay. Brain tissue samples from a portion of the BDV RNA- and/or antibody-positive animals were subjected to RT-qPCR and western blotting. As a result, varying prevalence of BDV antibodies and/or RNA was demonstrated in various animal species from three areas, ranging from 4.4 % to 20.0 %. Detection of BDV RNA and/or antibodies in Chongqing pigs (9.2 %) provided the first known evidence of BDV infection in this species. Not all brain tissue samples from animals whose blood was BDV RNA and/or antibody positive contained BDV RNA and protein. This study provides evidence that BDV infection among healthy domestic animal species is more widespread in western China than previously believed.

Epidemiology and host spectrum of Borna disease virus infections

Borna disease virus (BDV) has gained lot of interest because of its zoonotic potential, ability to introduce cDNA of its RNA transcripts into host genomes, and ability to cause severe neurobehavioural diseases. Classical Borna disease is a progressive meningoencephalomyelitis in horses and sheep, known in central Europe for centuries. According to current knowledge, BDV or a close relative also infects several other species, including humans at least occasionally, in central Europe and elsewhere, but the existence of potential 'human Borna disease' with its suspected neuropsychiatric symptoms is highly controversial. The recent detection of endogenized BDV-like genes in primate and various other vertebrate genomes confirms that at least ancient bornaviruses did infect our ancestors. The epidemiology of BDV is largely unknown, but accumulating evidence indicates vectors and reservoirs among small wild mammals. The aim of this review is to bring together the current knowledge on epidemiology of BDV infections. Specifically, geographical and host distribution are addressed and assessed in the critical light of the detection methods used. We also review some salient clinical aspects.

[Bornaviruses]

Bornaviridae is an enveloped animal virus carrying an 8.9 kb non-segmented, negative-strand RNA genome. The genus bornavirus contains two members infecting vertebrates, Borna disease virus (BDV) and avian bornavirus (ABV), which could preferably infect the nervous systems. BDV causes classical Borna disease, a progressive meningoencephalomyelitis, in horses and sheep, and ABV is known to induce proventricular dilatation disease, a fatal disease characterized by a lymphocytic, plasmacytic inflammation of central and peripheral nervous tissues, in multiple avian species. Recent evidences have demonstrated that bornavirus is unique among RNA viruses as they not only establish a long-lasting, persistent infection in the nucleus, but also integrate their own DNA genome copy into the host chromosome. In this review, I outline the recent knowledge about the unique virological characteristics of bornaviruses, as well as the diseases caused by the infection of BDV and ABV.

Borna disease virus infects human neural progenitor cells and impairs neurogenesis

Understanding the complex mechanisms by which infectious agents can disrupt behavior represents a major challenge. The Borna disease virus (BDV), a potential human pathogen, provides a unique model to study such mechanisms. Because BDV induces neurodegeneration in brain areas that are still undergoing maturation at the time of infection, we tested the hypothesis that BDV interferes with neurogenesis. We showed that human neural stem/progenitor cells are highly permissive to BDV, although infection does not alter their survival or undifferentiated phenotype. In contrast, upon the induction of differentiation, BDV is capable of severely impairing neurogenesis by interfering with the survival of newly generated neurons. Such impairment was specific to neurogenesis, since astrogliogenesis was unaltered. In conclusion, we demonstrate a new mechanism by which BDV might impair neural function and brain plasticity in infected individuals. These results may contribute to a better understanding of behavioral disorders associated with BDV infection.

The influence of Borna disease viral infection on dairy cow reproduction

We investigated the influence of Borna disease virus (BDV) infection on the clinical state of dairy cows. Sera from 149 cows were examined using enzyme-linked immunosorbent assay and western blotting detect antibodies to the BDV-nucleoprotein antigen. Among 149 investigated cows, 25 (16.8%) showed a positive reaction to BDV antigen. No significant difference existed in milk production or medical history between seropositive and seronegative cows. Although the estrus cycle appeared normal even in the seropositive cows, the frequency of artificial insemination and calving-to-conception intervals significantly increased in seropositive cows. Therefore, fertilization failure was recognized in the BDV-antibody positive cows.

Borna disease virus in Raccoons (Procyon lotor) in Japan

We have examined the seroprevalence of BDV in wild Raccoons (Procyon lotor) in Hokkaido, Japan. Serum samples from raccoons were examined using ELISA and Western blot assays to detect the presence of serum antibodies that react specifically to BDV antigens. Among 549 investigated individuals, eleven (2.0%) showed a positive reaction to BDV antigens. Brain tissue samples from five individuals were subjected to RT-PCR, which detected BDV sequences in three of them. Sequence analysis revealed a high degree of genetic conservation between BDV sequences derived from raccoons and previously published sequences derived from other animal species.