Demonstration of human Borna disease virus RNA in human peripheral blood mononuclear cells

Nucleoprotein (P40) Binding to 5HT2C Receptors (5HT2CR) is the Key Point in the Pathogenesis of BoDV-1-Infected Hosts

Nucleoprotein (P40) is one of the most important proteins of Borna disease virus 1 (BoDV-1), but which proteins it would bind to in the pathogenesis of BoDV-1-infected hosts is unknown. We used lentivirus LV5-P40 overexpressing P40 to infect primary hippocampal neurons and characterized the interactome of P40 with co-immunoprecipitation (Co-IP) followed by mass spectrometry (MS) analysis. These interacting protein partners revealed the pathogenesis of BoDV-1-infected hosts. We also show for the first time that P40 interacts with 5HT2CR in rat neurons, which may be the molecular basis leading to neuropsychiatric diseases such as anxiety disorders and behavioral abnormalities after BoDV-1 infection of hosts.

Borna disease virus - fact and fantasy

The occasion of Brian Mahy's retirement as editor of Virus Research provides an opportunity to reflect on the work that led one of the authors (Lipkin) to meet him shortly after the molecular discovery and characterization of Borna disease virus in the late 1980s, and work with authors Briese and Hornig to investigate mechanisms of pathogenesis and its potential role in human disease. This article reviews the history, molecular biology, epidemiology, and pathobiology of bornaviruses.

Failure to detect borna disease virus antibody and RNA from peripheral blood mononuclear cells of psychiatric patients

OBJECTIVE

Borna disease virus (BDV) is a highly neurotropic agent causing various neuropsychiatric symptoms in animals. Over the past two decades, it has been suggested that BDV might be associated with human psychiatric diseases. We aimed to investigate whether BDV is associated with psychiatric patients in Korea.

METHODS

We recruited 60 normal controls and 198 psychiatric patients (98 patients with depressive disorder, 60 with schizophrenia, and 40 with bipolar disorder). We used an indirect immunofluorescence antibody (IFA) test for the BDV antibody and a real-time reverse transcriptase polymerase chain reaction (rRT-PCR) assay for p24 and p40 RNA from peripheral blood mononuclear cells (PBMCs).

RESULTS

Neither the BDV antibody nor p24, p40 RNA was detected in controls and patients groups.

CONCLUSION

Our results suggest that BDV might not be associated with psychiatric patients in Korea.

Role of Borna disease virus in neuropsychiatric illnesses: are we inching closer?

The biological cause of psychiatric illnesses continues to be under intense scrutiny. Among the various neurotropic viruses, Borna disease virus (BDV) is another virus that preferentially targets the neurons of the limbic system and has been shown to be associated with behavioural abnormalities. Presence of various BDV markers, including viral RNA, in patients with affective and mood disorders have triggered ongoing debate worldwide regarding its aetiopathogenic relationship. This article analyses its current state of knowledge and recent advances in diagnosis in order to prove or refute the association of BDV in causation of human neuropsychiatric disorders. This emerging viral causative association of behavioural disorders, which seems to be inching closer, has implication not only for a paradigm shift in the treatment and management of neuropsychiatric illnesses but also has an important impact on the public health systems.

Detection and analysis of Borna disease virus in Chinese patients with neurological disorders

BACKGROUND AND PURPOSE

Borna disease virus (BDV) is a neurotropic RNA virus that is known to cause neurological disturbances in various animal species, potentially even humans. However, the association between BDV infection and human neurological disorders remains unclear.

METHODS

Between August 2005 and March 2006, 65 patients with neurological disorders were enrolled into our study. The presence of BDV p24 RNA from peripheral blood mononuclear cells (PBMCs) was investigated by using nested reverse transcriptase PCR (RT-PCR) assay.

RESULTS

Borna disease virus p24 RNA was detected from PBMCs in six patients with viral encephalitis by using nested RT-PCR assay. However, BDV p24 RNA was not detected in patients with multiple sclerosis or peripheral nerve diseases.

CONCLUSION

There might be possible associations between BDV infection and human viral encephalitis.

Meta-analysis of putative human bornavirus sequences fails to provide evidence implicating Borna disease virus in mental illness

All Borna disease virus (BDV) sequences derived from human specimens published till date were thoroughly analysed and compared to sequences of BDV laboratory strains and to BDV sequences from animals which succumbed to classical Borna disease (BD). Despite high sequence conservation of the BDV genome, animal-derived BDV sequences clustered according to their geographic origin. However, in marked contrast, human-derived BDV sequences did not cluster according to their geographic origin but showed high sequence identities to BDV laboratory strains and animal-derived BDVs handled in the laboratories reporting the human strains. Japanese, US, Australian and French human-derived BDV sequences proved to be identical or very similar to animal-derived BDV sequences from Germany, although the human specimens were collected hundreds to thousands of miles away from the central European BD endemic regions. These findings suggest that previous studies linking BDV to human neuropsychiatric disease may have been compromised by inadvertent sample contamination.

No borna disease virus-specific RNA detected in blood of race horses and jockeys

BACKGROUND

Borna disease virus (BDV) predominantly infects horses and sheep, causing a broad range of behavioural disorders. It is controversial whether BDV infects humans and causes psychiatric disorders.

OBJECTIVES

We searched for BDV-derived nucleic acids in blood of race horses and jockeys riding the horses.

METHODS

We assayed for the BDV genome in RNA extracted from peripheral blood mononuclear cells (PBMC) of 39 race horses and 48 jockeys. Two polymerase chain reaction protocols [one-tube reverse transcription-polymerase chain reaction (RT-PCR) and two-step RT-PCR] were used to assay BDV p24 and p40 transcripts.

RESULTS

The p24 and p40 viral nucleic acid sequences were not detected in the PBMC RNAs from any of the race horses or jockeys.

CONCLUSIONS

These data do not support an epidemiological association between BDV infection, race horses and humans.

Detection of Borna disease virus p24 RNA in peripheral blood cells from Brazilian mood and psychotic disorder patients

BACKGROUND

Borna disease virus (BDV) is a virus that naturally infects a broad range of warm-blooded animals. BDV is an enveloped virus, non-segmented, negative-stranded RNA genome and has an organization characteristic of a member of Bornaviridae in the order of Mononegavirale. In the present work we investigated the presence of BDV p24 RNA in peripheral blood cells from 30 psychiatric patients (19 with mood disorder and 11 with psychotic disorder) and 30 healthy volunteers as the control group.

METHODS

All subjects were interviewed by structured diagnostic criteria categorized according to the DSM-IV, Axis I (SCID-V). The presence of BDV p24 RNA was investigated by nested reverse transcriptase PCR (RT-PCR) using specific primers to p24 from BDV. The specificity of the detection was analyzed by the sequencing of PCR products.

RESULTS

The mean duration of illness in mood and psychotic patients with p24 RNA of BDV was 25 (+/-12.3) years and the median age was 43.77 (+/-15.2) years. There were no significant differences in gender and age among patients and control group, neither duration of illness among patients with mood and psychotic disorders in the presence or absence of p24 RNA of BDV. We found a frequency of 33.33% (10/30) of BDV-RNA on patient's group and 13.33% (4/30) on control group. The given sequences revealed identity with GenBank database sequence for BDV.

CONCLUSION

The detection of a higher level of BDV-RNA in the peripheral blood cells of patients than on control group should help our understanding of the pathogenesis in the disease.

Borna disease virus and the evidence for human pathogenicity: a systematic review

BACKGROUND

Borna disease is a neurological viral disease of veterinary importance in central Europe, although Borna Disease virus (BDV) has been reported to be present in animals in most continents. The hypothesis that BDV is associated with human illness is controversial. However, should even a small fraction of mental illness be attributable to infection with BDV, this would be an important finding, not least because illness in that sub-population would, theoretically, be preventable.

METHODS

We systematically reviewed the evidence: that BDV infects humans; for the role of BDV in human neuropsychiatric illness; to assess the suitability of currently available laboratory methods for human epidemiological studies.

RESULTS

We identified 75 documents published before the end of January 2000, describing 50 human studies for BDV. There were five case studies and 44 (sero)prevalence studies, in a variety of patient groups. Nineteen prevalence studies (43%) investigated seroprevalence, 11 (25%) investigated viral prevalence and 14 (32%) investigated both. Seroprevalence ranged from 0% to 48%, and prevalence of virus or viral footprints from 0% to 82%.

DISCUSSION

Although agreed gold standard tests and evidence for test specificity are lacking, there is evidence that humans are exposed to the virus. Further epidemiological studies are required to establish whether there are associations with disease.

Borna disease virus and deficit schizophrenia

BACKGROUND

It is controversial whether Borna disease virus (BDV) infects humans and causes psychiatric disorders.

OBJECTIVES

The relationship between BDV infection and schizophrenia with deficit syndrome was investigated.

STUDY DESIGN

Using the Schedule for the Deficit Syndrome, 62 schizophrenic in-patients were selected from three psychiatric hospitals. RNA was extracted from peripheral blood mononuclear cells and analyzed using nested reverse transcriptase-polymerase chain reaction with primers to detect BDV p24 and p40.

RESULTS AND CONCLUSIONS

BDV transcripts were not detected in samples from any of the 62 schizophrenic patients. These data do not support an etiologic association between BDV infection and the deficit form of schizophrenia.

Detection of anti-Borna Disease Virus (BDV) antibodies from patients with schizophrenia and mood disorders in Japan

The relationship between infection with the Borna Disease Virus (BDV) and the clinical symptoms of schizophrenia and mood disorders (DMS-IV) was investigated. Western blotting techniques were used to examine anti-p10-BDV antibodies in serum from 32 patients with schizophrenia and 33 patients with mood disorders in Japan. The results showed that 1 out of 25 controls (4.0%), 7 out of 32 patients with schizophrenia (21.9%) and 9 out of 33 patients with mood disorders (27.3%) were positive for anti-BDV-p10 antibodies. Compared with levels of anti-BDV-p10 antibodies in controls, the production of anti-BDV-p10 antibodies failed to show a statistically significant relationship with schizophrenia but did show a significant relationship with mood disorder. The subgroup of schizophrenia patients with positive syndromes had a non-significantly higher frequency of anti-BDV-p10 antibodies than the subgroup of patients with negative syndromes. Similarly, the production of anti-BDV-p10 antibodies was non-significantly higher among patients with the unipolar subtype of mood disorder than in those with the bipolar subtype.

Modulation of Borna disease virus phosphoprotein nuclear localization by the viral protein X encoded in the overlapping open reading frame

Borna disease virus (BDV) is a nonsegmented, negative-strand RNA virus that belongs to the Mononegavirales order. Unlike other animal viruses in this order, BDV replicates and transcribes in the nucleus of infected cells. Therefore, regulation of the intracellular movement of virus components must be critical for accomplishing the BDV life cycle in mammalian cells. Previous studies have demonstrated that BDV proteins are prone to accumulate in the nucleus of cells transiently transfected with each expression plasmid of the viral proteins. In BDV infection, however, cytoplasmic distribution of the viral proteins is frequently found in cultured cells and animal brains. In this study, to understand the modulation of subcellular localization of BDV proteins, we investigated the intracellular localization of the viral phosphoprotein (P). Transient-transfection analysis with a cDNA clone corresponding to a bicistronic transcript that expresses both viral X and P revealed that P efficiently localizes in the cytoplasm only when BDV X is expressed in the cells. Furthermore, our analysis revealed that the direct binding between X and P is necessary for the cytoplasmic localization of the P. Interestingly, we showed that X is not detectably expressed in the BDV-infected cells in which P is predominantly found in the nucleus, with little or no signal in the cytoplasm. These observations suggested that BDV P can modulate their subcellular localization through binding to X and that BDV may regulate the expression ratio of each viral product in infected cells to control the intracellular movement of the viral protein complexes. The results presented here provide a new insight into the regulation of the intracellular movement of viral proteins of a unique, nonsegmented, negative-strand RNA virus.

1-beta-D-arabinofuranosylcytosine inhibits borna disease virus replication and spread

Borna disease virus (BDV) is a nonsegmented, negative-strand RNA virus that causes neurological diseases in a variety of warm-blooded animal species. There is general consensus that BDV can also infect humans, being a possible zoonosis. Although the clinical consequences of human BDV infection are still controversial, experimental BDV infection is a well-described model for human neuropsychiatric diseases. To date, there is no effective treatment against BDV. In this paper, we demonstrate that the nucleoside analog 1-beta-D-arabinofuranosylcytosine (Ara-C), a known inhibitor of DNA polymerases, inhibits BDV replication. Ara-C treatment inhibited BDV RNA and protein synthesis and prevented BDV cell-to-cell spread in vitro. Replication of other negative-strand RNA viruses such as influenza virus or measles virus was not inhibited by Ara-C, underscoring the particularity of the replication machinery of BDV. Strikingly, Ara-C treatment induced nuclear retention of viral ribonucleoparticles. These findings could not be attributed to known effects of Ara-C on the host cell, suggesting that Ara-C directly inhibits the BDV polymerase. Finally, we show that Ara-C inhibits BDV replication in vivo in the brain of infected rats, preventing persistent infection of the central nervous system as well as the development of clinical disease. These findings open the way to the development of effective antiviral therapy against BDV.

Prevalence of circulating antibodies to p10, a non-structural protein of the Borna disease virus in cats with ataxia

Japanese domestic cats were surveyed for circulating antibodies to the plO and p24 proteins of the Borna disease virus (BDV) by Western blotting. Twenty-four of 52 cats (46.2%) with ataxia and other neurologic symptoms of unknown cause were positive for antibodies to BDV p10 and/or p24. In contrast, cats without neurological symptoms gave a significantly lower prevalence of anti-BDV antibodies to p10 and/or p24 (36 of 152 cats, 23.7%). Thirty specific pathogen-free (SPF) cats tested as controls were uniformly negative to BDV pl0 and p24 antigens. These results suggest that BDV may play a role in ataxia in cats. Additionally, our results suggest that it is necessary to use both p10 and p24 as antigens to detect circulating antibodies to BDV in cats.

Borna disease virus phosphoprotein binds a neurite outgrowth factor, amphoterin/HMG-1

The Borna disease virus (BDV) p24 phosphoprotein is an abundant protein in BDV-infected cultured cells and animal brains. Therefore, there is a possibility that binding of the p24 protein to cellular factor(s) induces functional alterations of infected neural cells in the brain. To identify a cellular protein(s) that interacts with BDV p24 protein, we performed far-Western blotting with extracts from various cell lines. Using recombinant p24 protein as a probe, we detected a 30-kDa protein in all cell lines examined. Binding between the 30-kDa and BDV p24 proteins was also demonstrated using BDV p24 affinity and ion-exchange chromatography columns. Microsequence analysis of the purified 30-kDa protein revealed that its N terminus showed complete homology with rat amphoterin protein, which is a neurite outgrowth factor abundant in the brain during development. Mammalian two-hybrid and immunoprecipitation analyses also confirmed that amphoterin is a specific target for the p24 protein in vivo. Furthermore, we showed that infection by BDV, as well as purified p24 protein in the medium, significantly decreased cell process outgrowth of cells grown on laminin, indicating the functional inhibition of amphoterin by interaction with the p24 protein. Immunohistochemical analysis revealed decreased levels of amphoterin protein at the leading edges of BDV-infected cells. Moreover, the expression of the receptor for advanced glycation end products, of which the extracellular moiety is a receptor for amphoterin, was not significantly activated in BDV-infected cells during the process of extension, suggesting that the secretion of amphoterin from the cell surface is inhibited by the binding of the p24 protein. These results suggested that BDV infection may cause direct damage in the developing brain by inhibiting the function of amphoterin due to binding by the p24 phosphoprotein.

Borna disease virus infection in psychiatric patients: are we on the right track?

Animals infected with Borna disease virus (BDV) typically present with neurological dysfunction including behavioural abnormalities. Seroepidemiological surveys suggested that BDV infection can occur in human beings and is associated with mental disorders. Partly contradictory results from studies employing RT-PCR and serological screening led to debate over whether BDV can infect people at all. Critical evaluation of available data led to doubts about the diagnostic value of RT-PCR-based test results. A more consistent picture has emerged from serological studies because seropositive cases were found more frequently among psychiatric patients than among normal controls, supporting the notion that BDV might indeed be responsible for some psychiatric disorders. This view is now challenged by the observation that human BDV-reactive antibodies are of low avidity and might therefore represent cross-reacting antibodies. It remains to be shown whether these antibodies are indeed induced by BDV or by related antigens of unknown identity.

N-terminal domain of Borna disease virus G (p56) protein is sufficient for virus receptor recognition and cell entry

Borna disease virus (BDV) surface glycoprotein (GP) (p56) has a predicted molecular mass of 56 kDa. Due to extensive posttranslational glycosylation the protein migrates as a polypeptide of 84 kDa (gp84). The processing of gp84 by the cellular protease furin generates gp43, which corresponds to the C-terminal part of gp84. Both gp84 and gp43 have been implicated in viral entry involving receptor-mediated endocytosis and pH-dependent fusion. We have investigated the domains of BDV p56 involved in virus entry. For this, we used a pseudotype approach based on a recently developed recombinant vesicular stomatitis virus (VSV) in which the gene for green fluorescent protein was substituted for the VSV G protein gene (VSV Delta G*). Complementation of VSV Delta G* with BDV p56 resulted in infectious VSV Delta G* pseudotypes that contained both BDV gp84 and gp43. BDV-VSV chimeric GPs that contained the N-terminal 244 amino acids of BDV p56 and amino acids 421 to 511 of VSV G protein were efficiently incorporated into VSV Delta G* particles, and the resulting pseudotype virions were neutralized by BDV-specific antiserum. These findings indicate that the N-terminal part of BDV p56 is sufficient for receptor recognition and virus entry.

Borna disease virus infection of adult and neonatal rats: models for neuropsychiatric disease

Animal models provide unique opportunities to explore interactions between host and environment. Two models have been established based on Borna disease virus infection that provide new insights into mechanisms by which neurotropic agents and/or immune factors may impact developing or mature CNS circuitry to effect complex disturbances in movement and behavior. Note in press: Since this chapter was submitted, several manuscripts have been published that extend findings reported here and support the relevance of BDV infections of neonatal Lewis rats as models for investigating mechanisms of neurodevelopmental damage in autism. Behavioral abnormalities, including disturbed play behavior and chronic emotional overactivity, have been described by Pletnikov et al. (1999); inhibition of responses to novel stimuli were described by Hornig et al. (1999); loss of Purkinje cells following neonatal BDV infection has been demonstrated by Eisenman et al. (1999), Hornig et al. (1999), and Weissenböck et al. (2000); and alterations in cytokine gene expression have been reported by Hornig et al. (1999), Plata-Salaman et al. (1999) and Sauder et al. (1999).

Borna disease virus and human disease

The biology of Borna disease virus (BDV) strongly supports the likelihood of human infection with BDV or a variant of BDV. Thus far, the evidence supporting BDV infection in humans has initiated much controversy among basic and clinical scientists; only time and additional research will support or refute the hypothesis of human BDV infection. Until an assay of acceptable specificity and sensitivity has been developed, validated, and used to document human BDV infection, scientists cannot reasonably begin to associate BDV infection with specific disease syndromes. Clinical studies seeking causal associations between BDV infection and specific diseases must ensure the proper identification of the BDV infection status of patients and control subjects by using a validated, highly sensitive, and highly specific assay (or series of assays). For clinical studies, a highly sensitive "screening" test followed by a highly specific confirmatory test will be of significant benefit. Although it is possible to formulate hypotheses about the clinical outcomes of human BDV infection based on animal model work, to date no human disease has been causally linked to human BDV infection. Scientists all over the world are actively pursuing these issues, and with continuing advances in clinical and basic BDV research, the answers cannot be far away.

Borna disease virus and neuropsychiatric disease--a reappraisal

Despite progress in understanding the molecular biology and pathobiology of Borna disease virus, its epidemiology and role in human disease remain controversial. The challenges encountered in this field are a paradigm for the investigation of diseases potentially linked to complex host-microorganism interactions.

Borna disease virus--does it infect humans and cause psychiatric disorders?

Antibodies recognizing Borna disease virus (BDV) antigens were first demonstrated in the blood of psychiatric patients approximately 15 years ago. Since that time, a highly controversial debate arose whether BDV infects humans and whether it causes psychiatric disorders. In this review, we critically discuss the results of numerous studies that assessed this possibility by using virological and serological methods. We conclude that there is presently no strong experimental evidence supporting the notion that BDV is a human pathogen. The possibility remains, however, that an antigenically related agent is associated with human psychiatric disorders.

Low avidity of human serum antibodies for Borna disease virus antigens questions their diagnostic value

Borna disease virus (BDV) can induce neurological disease in animals. Since viral nucleic acid, infectious particles and antibodies recognizing BDV antigens were found at higher frequencies in psychiatric patients than in healthy controls, BDV is suspected to cause psychiatric disorders in humans. However, the human origin of these viruses has recently been questioned. To diagnose BDV infections, sera are usually analyzed for antiviral antibodies by indirect immunofluorescence (IFA) on virus-infected cells. This study reveals that the reactive antibodies in human sera mainly recognized the BDV phosphoprotein, whereas animal sera preferentially detected the viral nucleoprotein. Immunoglobulin (Ig) G in sera of experimentally or naturally infected animals bound to the viral antigen with high avidity, ie resisting 3 M urea, whereas reactive IgG in human sera did not. Longitudinal studies showed that reactive human antibodies persisted for many years without gaining high avidity for BDV antigens, indicating that they were probably not induced by BDV but rather by infection with an antigenically related microorganism of unknown identity or by exposure to other related immunogens.

Borna disease virus persistent infection activates mitogen-activated protein kinase and blocks neuronal differentiation of PC12 cells

Persistence of Borna disease virus (BDV) in the central nervous system causes damage to specific neuronal populations. BDV is noncytopathic, and the mechanisms underlying neuronal pathology are not well understood. One hypothesis is that infection affects the response of neurons to factors that are crucial for their proliferation, differentiation, or survival. To test this hypothesis, we analyzed the response of PC12 cells persistently infected with BDV to the neurotrophin nerve growth factor (NGF). PC12 is a neural crest-derived cell line that exhibits features of neuronal differentiation in response to NGF. We report that persistence of BDV led to a progressive change of phenotype of PC12 cells and blocked neurite outgrowth in response to NGF. Infection down-regulated the expression of synaptophysin and growth-associated protein-43, two molecules involved in neuronal plasticity, as well as the expression of the chromaffin-specific gene tyrosine hydroxylase. We showed that the block in response to NGF was due in part to the down-regulation of NGF receptors. Moreover, although BDV caused constitutive activation of the ERK1/2 pathway, activated ERKs were not translocated to the nucleus efficiently. These observations may account for the absence of neuronal differentiation of persistently infected PC12 cells treated with NGF.

Immunological and PCR analyses for Borna disease virus in psychiatric patients and blood donors in Japan

The involvement of Borna disease virus (BDV) in psychiatric diseases in humans remains controversial. T-cell memory response and seroprevalence of BDV in patients with psychiatric disorders and blood donors in Japan were evaluated collectively by Western blot (WB) analysis with inhibition test, electrochemiluminescence immunoassay, immunofluorescence assay, and T-cell proliferative response as well as detection of BDV p24 RNA in peripheral blood mononuclear cells (PBMCs). Positive proliferative responses to both BDV p40 and p24 proteins were detected in 9% of patients with mood disorders (4 of 45), 4% of schizophrenic patients (2 of 45), and 2% of blood donors (1 of 45). By WB analysis, the antibody to BDV p40 was detected only in 2% of patients with mood disorders (1 of 45). The BDV p24 antibody was detected in 2% of patients with mood disorders (1 of 45) and 9% of schizophrenic patients. (4 of 45) No plasma reacted with both BDV proteins. The finding of a lower seroprevalence than previously reported suggests the presence of false-positive cases in the previous report. BDV RNA was detected only in 2% of patients with mood disorders (1 of 45). In these three serological assays, T-cell responses, and PCR analysis, there was no significant difference in the prevalence among the three groups. However, we found three psychiatric patients who were positive for both BDV antibodies and T-cell proliferative responses and one patient who was positive for BDV RNA in PBMCs. These findings suggest the usefulness of the proliferative T-cell response and that certain individuals are infected with BDV or a BDV-related virus.

Borna disease virus

Borna disease virus (BDV) is unique amongst animal RNA viruses in its molecular biology and capacity to cause persistent, noncytolytic CNS-infection in a wide variety of host species. Unlike other non-segmented negative-strand RNA animal viruses, BDV replicates in the nucleus of the host cell where splicing is employed for expression of a very compact genome. Epidemiological studies indicate a broad host range and geographical distribution, and some investigators have proposed that human infection may result in neuropsychiatric disorders. Experimental Borna disease in neonatal and adult rats provides an intriguing model for immune-mediated disturbances of brain development and function.

Borna disease virus: a mystery as an emerging zoonotic pathogen

For Central European veterinarians, Borna disease (BD) has been known for a long time as a sporadically occurring, progressive viral polioencephalomyelitis predominantly affecting horses and sheep and-as discovered in the last decade-an increasing number of domestic and zoo animals. The aetiological agent, the Borna disease virus (BDV), a negative-sense, single-stranded RNA virus classified in the new virus family Bornaviridae within the order Mononegavirales, can induce severe clinical signs typically of a viral encephalitis with striking behavioural disturbances. After an incubation period lasting a few weeks to several months, BDV-infection causes locomotor and sensory dysfunctions followed by paralysis and death. Natural infections seem to be subclinical in most cases. BD received world-wide attention when it was reported that sera and/or cerebrospinal fluids from neuro-psychiatric patients can contain BDV-specific antibodies. Since infected animals produce BDV-specific antibodies only after virus replication, it was assumed that the broad spectrum of BDV-susceptible species also includes man. However, reports describing the presence of other BDV-markers, i.e. BDV-RNA or BDV-antigen, in peripheral blood leukocytes or brain tissue of neuro-psychiatric patients are highly controversial and, therefore, the role of BDV in human neuro-psychiatric disorders is questionable. (c) 2001 Harcourt Publishers Ltd.

Translation initiation of a bicistronic mRNA of Borna disease virus: a 16-kDa phosphoprotein is initiated at an internal start codon

We examined translational initiation of a bicistronic 0.8-kb mRNA of Borna disease virus (BDV) using a cDNA clone of the mRNA. Upon transfection with the clone, COS-7 cells produced a 16-kDa protein (P'), in addition to the previously identified products of BDV, 24- (P) and 14.5-kDa proteins. The 16-kDa product was detected by anti-P monoclonal antibody and was shown to exist in BDV-infected cell lines as well as in infected animal brain cells. Transient expression analysis of mutated cDNA clones encoding the BDV 0.8-kb mRNA revealed that the 16-kDa protein was initiated at the second AUG codon on the same open reading frame of the P protein. The mutational analysis also demonstrated that the first AUG within the 0.8-kb mRNA is not optimal, although the signal contains a better Kozak's motif. These results demonstrated the presence of three functional AUG codons in the smallest mRNA of BDV and also suggested that a leaky scanning mechanism is involved in translational initiation at AUG codons downstream of the bicistronic mRNA of BDV. Furthermore, the 16-kDa protein was located in the BDV-specific nuclear foci and was found to associate with the other viral proteins in BDV-infected cells, demonstrating an important role of the novel identified BDV protein in viral replication.

Experimental and natural borna disease virus infections: presence of viral RNA in cells of the peripheral blood

Cells of the peripheral blood of experimentally and naturally borna disease virus (BDV)-infected animals and of human psychiatric patients and healthy individuals were analyzed for the presence of viral RNA using a BDV-p40-specific nested reverse transcription-polymerase chain reaction (RT-PCR). The assay proved to be highly sensitive as 10 RNA molecules were reproducibly amplified. BDV RNA was detected in blood cells of experimentally infected immunocompetent mice and rats. Mice were persistently infected without showing clinical signs of borna disease (BD), whereas the rats suffered from acute BD. Among 19 horses examined, five were positive for viral RNA in the blood. In a flock of sheep with a history of BD, 1 out of 25 clinically healthy animals was positive. BDV RNA was also detected in cells of the peripheral blood of 10 out of 27 selected humans with psychiatric disorders, and in 2 out of 13 healthy individuals. Remarkably, BDV-specific RNA was present in some cases in the absence of BDV-specific antibodies. Sequence analysis of PCR products confirmed the specificity of the amplification system. The presence of BDV RNA in the blood of naturally and experimentally BDV-infected individuals may point to an incidental but relevant role of blood for the spread of BDV in the infected organism, as well as for the transmission of BDV to other individuals.

Borna disease in a free-ranging lynx (Lynx lynx)

A free-ranging lynx (Lynx lynx) was shot because of its abnormal behavior. Histopathological examination revealed a nonsuppurative meningoencephalitis. In situ hybridization, immunohistochemistry, and reverse transcriptase PCR analysis showed the presence of Borna disease virus infection in the brain. To our knowledge, this is the first confirmed case of Borna disease in a large felid.

Isolation of Borna disease virus from human brain tissue

Serological and molecular epidemiological studies indicate that Borna disease virus (BDV) can infect humans and is possibly associated with certain neuropsychiatric disorders. We examined brain tissue collected at autopsy from four schizophrenic patients and two healthy controls for the presence of BDV markers in 12 different brain regions. BDV RNA and antigen was detected in four brain regions of a BDV-seropositive schizophrenic patient (P2) with a very recent (2 years) onset of disease. BDV markers exhibited a regionally localized distribution. BDV RNA was found in newborn Mongolian gerbils intracranially inoculated with homogenates from BDV-positive brain regions of P2. Human oligodendroglia (OL) cells inoculated with brain homogenates from BDV-positive gerbils allowed propagation and isolation of BDVHuP2br, a human brain-derived BDV. Virus isolation was also possible by transfection of Vero cells with ribonucleoprotein complexes prepared from BDV-positive human and gerbil brain tissues. BDVHuP2br was genetically closely related to but distinct from previously reported human- and animal-derived BDV sequences.

A short leucine-rich sequence in the Borna disease virus p10 protein mediates association with the viral phospho- and nucleoproteins

Borna disease virus (BDV) is unique among the non-segmented negative-strand RNA viruses of animals and man because it transcribes and replicates its genome in the nucleus of the infected cell. It has recently been discovered that BDV expresses a gene product of 87 amino acids, the p10 protein, from an open reading frame that overlaps with the gene encoding the viral p24 phosphoprotein. In addition, the p10 protein has been localized to intranuclear BDV-specific clusters containing viral antigens. Here, characterization of p10 interactions with the viral nucleoprotein p38/p39 and the p24 phosphoprotein is reported. Immunoaffinity chromatography demonstrated the presence of high-salt stable complexes of p10 containing the p24 and p38/p39 proteins in extracts of BDV-infected cells. Analyses in the yeast two-hybrid system and biochemical co-precipitation experiments suggested that the p10 protein binds directly to the p24 phosphoprotein and indirectly to the viral nucleoprotein. Mutational analysis demonstrated that a leucine-rich stretch of amino acids at positions 8-15 within the p10 protein is critical for interaction with p24. Furthermore, binding of p10 to the viral phosphoprotein was shown to be important for association with the BDV-specific intranuclear clusters that may represent the sites of virus replication and transcription in infected cells. These findings are discussed with respect to possible roles for the p10 protein in viral RNA synthesis or ribonucleoprotein transport.

Characterization of the P protein-binding domain on the 10-kilodalton protein of Borna disease virus

The Borna disease virus (BDV) is the prototype member of the Bornaviridae, and it replicates in the cell nucleus. The BDV p24P and p40N proteins carry nuclear localization signals (NLS) and are found in the nuclei of infected cells. The BDV p10 protein does not have an NLS, but it binds with P and/or N and is translocated to the nucleus. Hence, p10 may play a role in the replication of BDV in the cell nucleus. Here, we show that the P-binding domain is located in the N terminus of p10 and that S(3) and L(16) are important for the interaction.

Synaptic pathology in Borna disease virus persistent infection

Borna disease virus (BDV) infection of newborn rats leads to a persistent infection of the brain, which is associated with behavioral and neuroanatonomical abnormalities. These disorders occur in the absence of lymphoid cell infiltrates, and BDV-induced cell damage is restricted to defined brain areas. To investigate if damage to synaptic structures anteceded neuronal loss in BDV neonatally infected rats, we analyzed at different times postinfection the expression levels of growth-associated protein 43 and synaptophysin, two molecules involved in neuroplasticity processes. We found that BDV induced a progressive and marked decrease in the expression of these synaptic markers, which was followed by a significant loss of cortical neurons. Our findings suggest that BDV persistent infection interferes with neuroplasticity processes in specific cell populations. This, in turn, could affect the proper supply of growth factors and other molecules required for survival of selective neuronal populations within the cortex and limbic system structures.

Detection of Borna disease virus in a pregnant mare and her fetus

A pregnant mare showing pyrexia, reduced appetite, ataxia and paresis was euthanized and examined for the presence of Borna disease virus (BDV). Her brain, showing multiple neuronal degeneration and necrosis with hemorrhage, and the histologically normal brain of the fetus were both positive for BDV RNA. The BDV nucleotide sequences were identical in the mare and fetus in the second open reading frame (ORF). This is the first report of the possible vertical transmission of BDV in a horse.

Amantadine in depressive patients with Borna disease virus (BDV) infection: an open trial

OBJECTIVE

Originally introduced into pharmacotherapy as an antiviral compound, amantadine was shown to also have multiple pharmacological eftfects on the central nervous system. In addition. only a few studies reported on certain antidepressive properties of amantadine. This effect was highlighted by the discovery of its antiviral effect on Borna disease virus (BDV), which is hypothesized to be an etiopathogenetic factor to subtypes of affective disorders. Therefore, the therapeutical use of amantadine in BDV-infected depressive patients was investigated.

METHODS

In this open trial, amantadine was added to antidepressive and or mood-stabilizing compounds treating BDV-infected depressed patients (n = 25) with bipolar or major depressive disorders. Amantadine was given twice a day (100-300 mg/day) for a mean of 11 weeks. Antidepressive treatment response was measured on the Hamilton rating scale for depression (HAM-D) and/or with an operationalized diagnostic criteria system (OPCRIT: version 3.31). Virological response was measured by expression of BDV infection parameters in blood samples.

RESULTS

The overall response rate of the amantadine augmentation in the BDV-infected patients with regard to depressive symptoms was 68% after a mean of 2.9 weeks of treatment. Bipolar I patients improved faster and did not show any following hypomania. In addition, the decrease of depression tended to correspond with the decrease in viral activity.

CONCLUSION

Amantadine appears to show a remarkable antidepressive efficacy in BDV-infected depressive patients. The antidepressive effect in this open trial appeared to be comparable to standard antidepressives, possibly being a result of its antiviral effect against BDV as a potentially relevant etiopathogenetic factor in these disorders.

High prevalence of Borna disease virus in domestic cats with neurological disorders in Japan

A total of 15 (T-1-T-15) domestic cats with neurological disorders in Tokyo area were examined for association with Borna disease virus (BDV). None had detectable antibodies to feline immunodeficiency virus (FIV), feline leukemia virus, feline infectious peritonitis virus and Toxoplasma gondii, and only cat T-8 had detectable antibody to FIV. Serological and molecular epidemiological studies revealed a significantly high prevalence of BDV infection in these cats: antibodies against BDV p24 and/or p40 proteins in 10/15 (66.7%) and p24 and/or p40 RNA in peripheral blood mononuclear cells in 8/15 (53.3%). Further, in situ hybridization and immunohistochemistry analyses of the autopsied brain samples derived from one of the cats (T-15) revealed BDV RNA predominantly in neuronal cells in restricted regions, such as olfactory bulb and medulla of cerebrum. Thus, BDV is present in Japanese domestic cats with neurological disorders at a high prevalence.

Borna disease virus infection in two family clusters of patients with chronic fatigue syndrome

A high rate of Borna disease virus (BDV) infection has been demonstrated in patients with chronic fatigue syndrome (CFS). Herein, we focused on BDV infection in two family clusters of patients with CFS: a father, mother, two sons and one daughter (family #1); and a father, mother, two daughters and one son (family #2). All members, except for the elder son in family #1 and the father and son in family #2, were diagnosed with CFS. The results supported that all the family members with CFS were infected with BDV, as evidenced by the presence of antibodies to viral p40, p24 and/or gp18 and BDV p24 RNA in peripheral blood mononuclear cells. The healthy members, except for the father of family #2 who was positive for antibody to p24, were all negative by both assays. Follow-up studies in family #1 continued to reveal BDV antibodies and BDV RNA, except in the mother, who lost the RNA upon slight recovery from the disease.

Borna disease virus infection in domestic cats: evaluation by RNA and antibody detection

Borna disease virus (BDV) infection has been suggested to cause spontaneous neurological disease in cats referred to as staggering disease. However the evaluation of BDV infection in neurologically asymptomatic cats remained unclear. In the present study, BDV infected, asymptomatic cats in Tokyo were surveyed both by the presence of plasma antibodies against BDV-p24 and -p40 and by RNA detection in peripheral blood mononuclear cells. Seven of 32 domestic cats (21.9%) were serologically or genetically judged to be BDV-infected. Six cats were positive for anti-BDV antibody and two cats were positive for BDV RNA. Within the 2 RNA-positive cats, only one was positive for anti-BDV antibodies. Furthermore, the findings of anti-BDV-p40 and anti-BDV-p24 antibody-positive cats did not completely overlap. These results suggest that there are neurologically asymptomatic domestic cats infected with BDV present in the Tokyo area.

Cytokine expression in the rat central nervous system following perinatal Borna disease virus infection

Borna disease virus (BDV) causes central nervous system (CNS) disease in several vertebrate species, which is frequently accompanied by behavioral abnormalities. In the adult rat, intracerebral (i.c.) BDV infection leads to immunomediated meningoencephalitis. In contrast, i.c. infection of neonates causes a persistent infection in the absence of overt signs of brain inflammation. These rats (designated PTI-NB) display distinct behavioral and neurodevelopmental abnormalities. However, the molecular mechanisms for these virally induced CNS disturbances are unknown. Cytokines play an important role in CNS function, both under normal physiological and pathological conditions. Astrocytes and microglia are the primary resident cells of the central nervous system with the capacity to produce cytokines. Strong reactive astrocytosis is observed in the PTI-NB rat brain. We have used a ribonuclease protection assay to investigate the mRNA expression levels of proinflammatory cytokines in different brain regions of PTI-NB and control rats. We show here evidence of a chronic upregulation of proinflammatory cytokines interleukin-6, tumor necrosis factor alpha, interleukins-1alpha, and -1beta in the hippocampus and cerebellum of the PTI-NB rat brain. These brain regions exhibited only a very mild and transient immune infiltration. In contrast, in addition to reactive astrocytes, a strong and sustained microgliosis was observed in the PTI-NB rat brains. Our data suggest that CNS resident cells, namely astrocytes and microglia, are the major source of cytokine expression in the PTI-NB rat brain. The possible implications of these findings are discussed.

High susceptibility of Mongolian gerbil (Meriones unguiculatus) to Borna disease virus

Borna disease virus (BDV) is a neurotropic enveloped virus with a nonsegmented, single-, negative-stranded RNA genome. This virus induced encephalitis in experimentally infected adult rats, but in newborn rats BDV established a persistent, tolerant infection with no apparent clinical signs. Here, we report evidence that newborn Mongolian gerbils (Meriones unguiculatus) are more susceptible to experimental intracranial inoculation of horse-derived BDV in persistently infected MDCK cells, compared with similar inoculation in newborn rats. All inoculated newborn gerbils, but not rats, died 30 days after infection. Reverse transcriptase-polymerase chain reaction amplified BDV-specific sequences in several regions including the brain. Histopathological analysis revealed apparent inflammatory reactions in the brains of inoculated gerbils but not rats, although similar levels of BDV RNA were detected in both gerbil and rat brains. BDV-specific antigen and RNA were identified predominantly in neurons in the brains by immunohistochemistry with antibodies to BDV and in situ hybridization with BDV-specific riboprobes, respectively. BDV in the gerbil brain was easily rescued by co-cultivation of the brain homogenate with human oligodendroglioma cells. Thus, gerbils seem to be a useful animal model for studying BDV-induced pathogenesis in the brain.

Reverse transcription-nested polymerase chain reaction for detecting p40 RNA of Borna disease virus, without risk of plasmid contamination

Several methods for the detection of Borna disease virus (BDV) RNA have been reported, one being the reverse transcription-nested polymerase chain reaction (RT-nested PCR) method. However, due to the possibility of contamination of the cloned DNA in a reaction tube, false-positive results might be obtained by RT-nested PCR. To detect only BDV RNA without anxiety of contamination, we developed an RT-nested PCR system using "mRNA selective PCR kit". Using this system, cDNA of BDV p40 in the plasmid (up to 5 x 10(7) molecules) was not amplified. BDV specific sequence was amplified from total RNA (more than 50 pg) of MDCK/BDV cells, which were persistently infected with BDV. These results indicate that this mRNA selective RT-nested PCR system can specifically amplify target RNA as distinguished from plasmid contaminated.

Fine structure and morphogenesis of Borna disease virus

Borna disease virus (BDV), a negative nonsegmented single-stranded RNA virus, has not been fully characterized morphologically. Here we present what is to our knowledge the first data on the fine ultrastructure and morphogenesis of BDV. The supernatant of MDCK cells persistently infected with BDV treated with n-butyrate contained many virus-like particles and more BDV-specific RNA than that of untreated samples. The particles were spherical, enveloped, and approximately 130 nm in diameter; had spikes 7 nm in length; and reacted with BDV p40 antibody. A thin nucleocapsid, 4 nm in width, was present peripherally in contrast to the thick nucleocapsid of hemagglutinating virus of Japan. The BDV particles reproduced by budding on the cell surface.

Detection and sequence analysis of borna disease virus p24 RNA from peripheral blood mononuclear cells of patients with mood disorders or schizophrenia and of blood donors

Borna disease virus (BDV) p24 RNA was detected in the peripheral blood mononuclear cells (PBMCs) of psychiatric patients and blood donors by nested reverse transcriptase PCR (RT-PCR). The prevalences of BDV p24 RNA in patients with mood disorders (4%) and schizophrenia (4%) were not significantly different from that in blood donors (2%). This finding was inconsistent with previous reports that showed either a high prevalence or absence of BDV p24 RNA in patients with psychiatric disorders. The differences in BDV p24 RNA prevalence in these studies may be due to differences in the criteria for positivity, the number of PBMCs used for RNA extraction, or the amount of RNA tested for nested RT-PCR or to laboratory contamination. Sequence analysis of BDV p24 RNA from the PBMCs of patients and blood donors showed a high nucleotide sequence conservation but definite nucleotide mutations compared with horse BDV p24 RNA sequences. In comparison with human BDV p24 RNA sequences previously reported from Japan and Germany, there were several positions with silent nucleotide mutations among these clones.

Case control study of feline Borna disease in Sweden

A questionnaire-based, retrospective case-control study of 174 Swedish cats was used to identify possible risk factors for feline Borna disease. The questionnaire consisted of 32 questions on a wide range of subjects, including lifestyle and possible modes of virus transmission. Two control groups were used: a healthy-control and a hospital-control. Variables with significant odds ratios in either the Borna disease:healthy-control or Borna disease:hospital-control comparison were included in multiple logistic regression analyses. Overall, the models suggested that feline Borna disease has a predominantly rural/woodland distribution, that affected cats were more likely to be males than females and intact than neutered, and that they were more likely than not to have hunted mice. The results indicate that, in contrast to other feline viral infections, Borna disease virus is not readily transmitted between cats. The natural reservoir of the virus is unknown. The fact that exposure to mice by hunting was a risk factor for the disease suggests that rodents may be subclinically infected and act as virus carriers.

Borna disease virus-induced neurological disorder in mice: infection of neonates results in immunopathology

Borna disease virus (BDV) is a neurotropic nonsegmented negative-stranded RNA virus that persistently infects warm-blooded animals. In horses and other natural animal hosts, infections with BDV cause meningoencephalitis and behavioral disturbances. Experimental infection of adult mice takes a nonsymptomatic course, an observation previously believed to indicate that this animal species is not suitable for pathogenesis studies. We now demonstrate that BDV frequently induces severe neurological disease in infected newborn mice. Signs of neurological disease were first observed 4 to 6 weeks after intracerebral infection. They included a characteristic nonphysiological position of the hind limbs at an early stage of the disease and paraparesis at a later stage. Histological examination revealed large numbers of perivascular and meningeal inflammatory cells in brains of diseased mice and, unexpectedly, no increase in immunoreactivity to glial fibrillar acidic protein. The incidence and severity of BDV-induced disease varied dramatically among mouse strains. While only 13% of the infected C57BL/6 mice showed disease symptoms, which were mostly transient, more than 80% of the infected MRL mice developed severe neurological disorder. In spite of these differences in susceptibility to disease, BDV replicated to comparable levels in the brains of mice of the various strains used. Intracerebral infections of newborn beta2-microglobulin-deficient C57BL/6 and MRL mice, which both lack CD8+ T cells, did not result in meningoencephalitis or neurological disease, indicating that the BDV-induced neurological disorder in mice is a cytotoxic T-cell-mediated immunopathological process. With this new animal model it should now be possible to characterize the disease-inducing immune response to BDV in more detail.

In vivo treatment with anti-alpha4 integrin suppresses clinical and pathological evidence of Borna disease virus infection

Borna disease virus (BDV) infection of the rat brain induces a severe T-lymphocyte mediated inflammatory response that parallels the course of clinical Borna disease. In other models of CNS inflammation, the recruitment of T-lymphocytes from the circulation to sites of inflammation is believed to be directed, in part, by the cellular adhesion molecules alpha4 beta1 integrin (expressed on T-lymphocytes) and its ligand VCAM-1 (expressed on blood brain barrier endothelium). Since BDV-specific T-lymphocytes are known to express the alpha4 beta1 integrin, we examined the effect of in vivo treatment with an anti-alpha4 integrin monoclonal antibody (GG5/3) on the development of BDV-specific encephalitis and Borna disease. Here, we report that the inhibition of alpha4 integrin provided significant clinical benefit in slowing the progression of Borna disease. Antibody treatment greatly reduced the immune cell infiltrates in the CNS of BDV-infected animals, but we found that this inhibition of the immune response did not result in enhanced viral levels.

Evaluation of serological diagnosis of Borna disease virus infection using recombinant proteins in experimentally infected rats

We produced two recombinant Borna disease virus (BDV) proteins, p40 and p24, by using a baculovirus vector as a diagnostic antigen. Antigenicities of these recombinant proteins were evaluated by immune rabbit sera. Recombinant p40 was a more sensitive antigen than p24 for the detection of antibodies in infected rats. Rats inoculated with BDV within 24 hr after birth showed higher detection rates of viral RNA and viral proteins from the brain than rats inoculated at 4 weeks-old. Depending on the age of infection and the time postinfection, the detection of BDV RNA, protein, or anti-BDV antibody did not always correlate in individuals. We suggest both serological and molecular biological methods are needed in the diagnosis of BDV infection.