Natural and experimental Borna disease virus infections--neuropathology and pathogenetic considerations

Comparative study of virus and lymphocyte distribution with clinical data suggests early high dose immunosuppression as potential key factor for the therapy of patients with BoDV-1 infection

ABSTRACTBorna disease virus 1 (BoDV-1) was just recently shown to cause predominantly fatal encephalitis in humans. Despite its rarity, bornavirus encephalitis (BVE) can be considered a model disease for encephalitic infections caused by neurotropic viruses and understanding its pathomechanism is of utmost relevance. Aim of this study was to compare the extent and distribution pattern of cerebral inflammation with the clinical course of disease, and individual therapeutic procedures. For this, autoptic brain material from seven patients with fatal BVE was included in this study. Tissue was stained immunohistochemically for pan-lymphocytic marker CD45, the nucleoprotein of BoDV-1, as well as glial marker GFAP and microglial marker Iba1. Sections were digitalized and counted for CD45-positive and BoDV-1-positive cells. For GFAP and Iba1, a semiquantitative score was determined. Furthermore, detailed information about the individual clinical course and therapy were retrieved and summarized in a standardized way. Analysis of the distribution of lymphocytes shows interindividual patterns. In contrast, when looking at the BoDV-1-positive glial cells and neurons, a massive viral involvement in the brain stem was noticeable. Three of the seven patients received early high-dose steroids, which led to a significantly lower lymphocytic infiltration of the central nervous tissue and a longer survival compared to the patients who were treated with steroids later in the course of disease. This study highlights the potential importance of early high-dose immunosuppressive therapy in BVE. Our findings hint at a promising treatment option which should be corroborated in future observational or prospective therapy studies.ABBREVIATIONS: BoDV-1: Borna disease virus 1; BVE: bornavirus encephalitis; Cb: cerebellum; CNS: central nervous system; FL: frontal lobe; GFAP: glial fibrillary acid protein; Hc: hippocampus; Iba1: ionized calcium-binding adapter molecule 1; Iba1act: general activation of microglial cells; Iba1nod: formation of microglial nodules; IL: insula; Me: mesencephalon; Mo: medulla oblongata; OL: occipital lobe; pASS: per average of 10 screenshots; patearly: patients treated with early high dose steroid shot; patlate: patients treated with late or none high dose steroid shot; Po: pons; So: stria olfactoria; Str: striatum.

Exploring New Mechanism of Depression from the Effects of Virus on Nerve Cells

Depression is a common neuropsychiatric disorder with long-term recurrent depressed mood, pain and despair, pessimism and anxiety, and even suicidal tendencies as the main symptoms. Depression usually induces or aggravates the development of other related diseases, such as sleep disorders and endocrine disorders. In today's society, the incidence of depression is increasing worldwide, and its pathogenesis is complex and generally believed to be related to genetic, psychological, environmental, and biological factors. Current studies have shown the key role of glial cells in the development of depression, and it is noteworthy that some recent evidence suggests that the development of depression may be closely related to viral infections, such as SARS-CoV-2, BoDV-1, ZIKV, HIV, and HHV6, which infect the organism and cause some degree of glial cells, such as astrocytes, oligodendrocytes, and microglia. This can affect the transmission of related proteins, neurotransmitters, and cytokines, which in turn leads to neuroinflammation and depression. Based on the close relationship between viruses and depression, this paper provides an in-depth analysis of the new mechanism of virus-induced depression, which is expected to provide a new perspective on the mechanism of depression and a new idea for the diagnosis of depression in the future.

Word recognition memory and serum levels of Borna disease virus specific circulating immune complexes in obsessive-compulsive disorder

BACKGROUND

Borna disease virus 1 (BoDV-1) is a non-segmented, negative-strand RNA virus that persistently infects mammals including humans. BoDV-1 worldwide occurring strains display highly conserved genomes with overlapping genetic signatures between those of either human or animal origin. BoDV-1 infection may cause behavioral and cognitive disturbances in animals but has also been found in human major depression and obsessive-compulsive disorder (OCD). However, the impact of BoDV-1 on memory functions in OCD is unknown.

METHOD

To evaluate the cognitive impact of BoDV-1 in OCD, event-related brain potentials (ERPs) were recorded in a continuous word recognition paradigm in OCD patients (n = 16) and in healthy controls (n = 12). According to the presence of BoDV-1-specific circulating immune complexes (CIC), they were divided into two groups, namely group H (high) and L (low), n = 8 each. Typically, ERPs to repeated items are characterized by more positive waveforms beginning approximately 250 ms post-stimulus. This "old/new effect" has been shown to be relevant for memory processing. The early old/new effect (ca. 300-500 ms) with a frontal distribution is proposed to be a neural correlate of familiarity-based recognition. The late old/new effect (post-500 ms) is supposed to reflect memory recollection processes.

RESULTS

OCD patients were reported to show a normal early old/new effect and a reduced late old/new effect compared to normal controls. In our study, OCD patients with a high virus load (group H) displayed exactly these effects, while patients with a low virus load (group L) did not differ from healthy controls.

CONCLUSION

These results confirmed that OCD patients had impaired memory recollection processes compared to the normal controls which may to some extent be related to their BoDV-1 infection.

Bornavirus Encephalitis Shows a Characteristic Magnetic Resonance Phenotype in Humans

OBJECTIVE

The number of diagnosed fatal encephalitis cases in humans caused by the classical Borna disease virus (BoDV-1) has been increasing, ever since it was proved that BoDV-1 can cause human infections. However, awareness of this entity is low, and a specific imaging pattern has not yet been identified. We therefore provide the first comprehensive description of the morphology of human BoDV-1 encephalitis, with histopathological verification of imaging abnormalities.

METHODS

In an institutional review board-approved multicenter study, we carried out a retrospective analysis of 55 magnetic resonance imaging (MRI) examinations of 19 patients with confirmed BoDV-1 encephalitis. Fifty brain regions were analyzed systematically (T1w, T2w, T2*w, T1w + Gd, and DWI), in order to discern a specific pattern of inflammation. Histopathological analysis of 25 locations in one patient served as correlation for MRI abnormalities.

RESULTS

Baseline imaging, acquired at a mean of 11 ± 10 days after symptom onset, in addition to follow-up scans of 16 patients, revealed characteristic T2 hyperintensities with a predilection for the head of the caudate nucleus, insula, and cortical spread to the limbic system, whereas the occipital lobes and cerebellar hemispheres were unaffected. This gradient was confirmed by histology. Nine patients (47.4%) developed T1 hyperintensities of the basal ganglia, corresponding to accumulated lipid phagocytes on histology and typical for late-stage necrosis.

INTERPRETATION

BoDV-1 encephalitis shows a distinct pattern of inflammation in both the early and late stages of the disease. Its appearance can mimic sporadic Creutzfeldt-Jakob disease on MRI and should be considered a differential diagnosis in the case of atypical clinical presentation. ANN NEUROL 2020;88:723-735.

Obesity induced by Borna disease virus in rats: key roles of hypothalamic fast-acting neurotransmitters and inflammatory infiltrates

Human obesity epidemic is increasing worldwide with major adverse consequences on health. Among other possible causes, the hypothesis of an infectious contribution is worth it to be considered. Here, we report on an animal model of virus-induced obesity which might help to better understand underlying processes in human obesity. Eighty Wistar rats, between 30 and 60 days of age, were intracerebrally inoculated with Borna disease virus (BDV-1), a neurotropic negative-strand RNA virus infecting an unusually broad host spectrum including humans. Half of the rats developed fatal encephalitis, while the other half, after 3-4 months, continuously gained weight. At tripled weights, rats were sacrificed by trans-cardial fixative perfusion. Neuropathology revealed prevailing inflammatory infiltrates in the median eminence (ME), progressive degeneration of neurons of the paraventricular nucleus, the entorhinal cortex and the amygdala, and a strikingly high-grade involution of the hippocampus with hydrocephalus. Immune histology revealed that major BDV-1 antigens were preferentially present at glutamatergic receptor sites, while GABAergic areas remained free from BDV-1. Virus-induced suppression of the glutamatergic system caused GABAergic predominance. In the hypothalamus, this shifted the energy balance to the anabolic appetite-stimulating side governed by GABA, allowing for excessive fat accumulation in obese rats. Furthermore, inflammatory infiltrates in the ME and ventro-medial arcuate nucleus hindered free access of appetite-suppressing hormones leptin and insulin. The hormone transport system in hypothalamic areas outside the ME became blocked by excessively produced leptin, leading to leptin resistance. The resulting hyperleptinemic milieu combined with suppressed glutamatergic mechanisms was a characteristic feature of the found metabolic pathology. In conclusion, the study provided clear evidence that BDV-1 induced obesity in the rat model is the result of interdependent structural and functional metabolic changes. They can be explained by an immunologically induced hypothalamic microcirculation-defect, combined with a disturbance of neurotransmitter regulatory systems. The proposed mechanism may also have implications for human health. BDV-1 infection has been frequently found in depressive patients. Independently, comorbidity between depression and obesity has been reported, either. Future studies should address the exciting question of whether BDV-1 infection could be a link, whatsoever, between these two conditions.

Antiviral treatment perspective against Borna disease virus 1 infection in major depression: a double-blind placebo-controlled randomized clinical trial

Background

Whether Borna disease virus (BDV-1) is a human pathogen remained controversial until recent encephalitis cases showed BDV-1 infection could even be deadly. This called to mind previous evidence for an infectious contribution of BDV-1 to mental disorders. Pilot open trials suggested that BDV-1 infected depressed patients benefitted from antiviral therapy with a licensed drug (amantadine) which also tested sensitive in vitro. Here, we designed a double-blind placebo-controlled randomized clinical trial (RCT) which cross-linked depression and BDV-1 infection, addressing both the antidepressant and antiviral efficacy of amantadine.

Methods

The interventional phase II RCT (two 7-weeks-treatment periods and a 12-months follow-up) at the Hannover Medical School (MHH), Germany, assigned currently depressed BDV-1 infected patients with either major depression (MD; N = 23) or bipolar disorder (BD; N = 13) to amantadine sulphate (PK-Merz®; twice 100 mg orally daily) or placebo treatment, and contrariwise, respectively. Clinical changes were assessed every 2–3 weeks by the 21-item Hamilton rating scale for depression (HAMD) (total, single, and combined scores). BDV-1 activity was determined accordingly in blood plasma by enzyme immune assays for antigens (PAG), antibodies (AB) and circulating immune complexes (CIC).

Results

Primary outcomes (≥25% HAMD reduction, week 7) were 81.3% amantadine vs. 35.3% placebo responder (p = 0.003), a large clinical effect size (ES; Cohen’s d) of 1.046, and excellent drug tolerance. Amantadine was safe reducing suicidal behaviour in the first 2 weeks. Pre-treatment maximum infection levels were predictive of clinical improvement (AB, p = 0.001; PAG, p = 0.026; HAMD week 7). Respective PAG and CIC levels correlated with AB reduction (p = 0,001 and p = 0.034, respectively). Follow-up benefits (12 months) correlated with dropped cumulative infection measures over time (p < 0.001). In vitro, amantadine concentrations as low as 2.4–10 ng/mL (50% infection-inhibitory dose) prevented infection with human BDV Hu-H1, while closely related memantine failed up to 100,000-fold higher concentration (200 μg/mL).

Conclusions

Our findings indicate profound antidepressant efficacy of safe oral amantadine treatment, paralleling antiviral effects at various infection levels. This not only supports the paradigm of a link of BDV-1 infection and depression. It provides a novel possibly practice-changing low cost mental health care perspective for depressed BDV-1-infected patients addressing global needs.

Trial registration

The trial was retrospectively registered in the German Clinical Trials Registry on 04th of March 2015. The trial ID is DRKS00007649; https://www.drks.de/drks_web/setLocale_EN.do

The neuropathology of fatal encephalomyelitis in human Borna virus infection

After many years of controversy, there is now recent and solid evidence that classical Borna disease virus 1 (BoDV-1) can infect humans. On the basis of six brain autopsies, we provide the first systematic overview on BoDV-1 tissue distribution and the lesion pattern in fatal BoDV-1-induced encephalitis. All brains revealed a non-purulent, lymphocytic sclerosing panencephalomyelitis with detection of BoDV-1-typical eosinophilic, spherical intranuclear Joest–Degen inclusion bodies. While the composition of histopathological changes was constant, the inflammatory distribution pattern varied interindividually, affecting predominantly the basal nuclei in two patients, hippocampus in one patient, whereas two patients showed a more diffuse distribution. By immunohistochemistry and RNA in situ hybridization, BoDV-1 was detected in all examined brain tissue samples. Furthermore, infection of the peripheral nervous system was observed. This study aims at raising awareness to human bornavirus encephalitis as differential diagnosis in lymphocytic sclerosing panencephalomyelitis. A higher attention to human BoDV-1 infection by health professionals may likely increase the detection of more cases and foster a clearer picture of the disease.

Distribution of Viral Antigen and Inflammatory Lesions in the Central Nervous System of Cockatiels ( Nymphicus hollandicus) Experimentally Infected with Parrot Bornavirus 2

Neurotropism is a striking characteristic of bornaviruses, including parrot bornavirus 2 (PaBV-2). Our study evaluated the distribution of inflammatory foci and viral nucleoprotein (N) antigen in the brain and spinal cord of 27 cockatiels ( Nymphicus hollandicus) following experimental infection with PaBV-2 by injection into the pectoral muscle. Tissue samples were taken at 12 timepoints between 5 and 114 days post-inoculation (dpi). Each experimental group had approximately 3 cockatiels per group and usually 1 negative control. Immunolabeling was first observed within the ventral horns of the thoracic spinal cord at 20 dpi and in the brain (thalamic nuclei and hindbrain) at 25 dpi. Both inflammation and viral antigen were restricted to the central core of the brain until 40 dpi. The virus then spread quickly at 60 dpi to both gray and white matter of all analyzed sections of the central nervous system (CNS). Encephalitis was most severe in the thalamus and hindbrain, while myelitis was most prominent in the gray matter and equally distributed in the cervical, thoracic, and lumbosacral spinal cord. Our results demonstrate a caudal to rostral spread of virus in the CNS following experimental inoculation of PABV-2 into the pectoral muscle, with the presence of viral antigen and inflammatory lesions first in the spinal cord and progressing to the brain.

Identification of suitable reference genes for BDV-infected primary rat hippocampal neurons

Borna disease virus (BDV) is a neurotropic RNA virus that infects the limbic system of mammals and results in behavioral disorders. The hippocampus is a core region in the limbic system, which contributes to memory and learning and is important in the regulation of emotion. However, no validated microRNA housekeeping genes have yet been identified in BDV‑infected rat primary hippocampal neurons. Proper normalization is key in accurate miRNA expression analysis. The present study used reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) to evaluate the expression stability of 10 commonly used reference genes [miR‑92a, 5S, U6, miR‑103, miR‑101a, miR-let-7a, miR‑16, E2 small nucleolar RNA (snoRNA), U87 and miR‑191] in BDV‑infected rat hippocampal neurons and non‑infected controls across 12 days post‑infection. The data was analyzed by four statistical algorithms: geNorm, NormFinder, BestKeeper, and the comparative Δ‑Ct method. Subsequently, the most suitable reference genes (miR‑101a and U87) and the least suitable (snoRNA) were determined by the RankAggreg package. miR‑155 was selected as a standard by which to evaluate the most and least suitable reference genes. When normalized to the most stable reference gene there were significant differences between the two groups. However, when the data were normalized to the less stably expressed gene, the results were not significant. miR‑101a was recommended as a suitable reference gene for BDV-infected rat primary hippocampal neurons.

The pathogenesis of bornaviral diseases in mammals

Natural bornavirus infections and their resulting diseases are largely restricted to horses and sheep in Central Europe. The disease also occurs naturally in cats, and can be induced experimentally in laboratory rodents and numerous other mammals. Borna disease virus-1 (BoDV-1), the cause of most cases of mammalian Borna disease, is a negative-stranded RNA virus that replicates within the nucleus of target cells. It causes severe, often lethal, encephalitis in susceptible species. Recent events, especially the discovery of numerous new species of bornaviruses in birds and a report of an acute, lethal bornaviral encephalitis in humans, apparently acquired from squirrels, have revived interest in this remarkable family of viruses. The clinical manifestations of the bornaviral diseases are highly variable. Thus, in addition to acute lethal encephalitis, they can cause persistent neurologic disease associated with diverse behavioral changes. They also cause a severe retinitis resulting in blindness. In this review, we discuss both the pathological lesions observed in mammalian bornaviral disease and the complex pathogenesis of the neurologic disease. Thus infected neurons may be destroyed by T-cell-mediated cytotoxicity. They may die as a result of excessive inflammatory cytokine release from microglia. They may also die as a result of a ‘glutaminergic storm’ due to a failure of infected astrocytes to regulate brain glutamate levels.

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 infection impacts microRNAs associated with nervous system development, cell differentiation, proliferation and apoptosis in the hippocampi of neonatal rats

MicroRNAs (miRNAs) regulate gene expression by inhibiting transcription or translation and are involved in diverse biological processes, including development, cellular differentiation and tumor generation. miRNA microarray technology is a high‑throughput global analysis tool for miRNA expression profiling. Here, the hippocampi of four borna disease virus (BDV)‑infected and four non‑infected control neonatal rats were selected for miRNA microarray and bioinformatic analysis. Reverse transcription quantitative polymerase chain reaction (RT‑qPCR) analysis was subsequently performed to validate the dysregulated miRNAs. Seven miRNAs (miR‑145*, miR‑146a*, miR‑192*, miR‑200b, miR‑223*, miR‑449a and miR‑505), showed increased expression, whereas two miRNAs (miR‑126 and miR‑374) showed decreased expression in the BDV‑infected group. By RT‑qPCR validation, five miRNAs (miR‑126, miR‑200b, miR‑374, miR‑449a and miR‑505) showed significantly decreased expression (P<0.05) in response to BDV infection. Biocarta pathway analysis predicted target genes associated with 'RNA', 'IGF1mTOR', 'EIF2', 'VEGF', 'EIF', 'NTHI', 'extrinsic', 'RB', 'IL1R' and 'IGF1' pathways. Gene Ontology analysis predicted target genes associated with 'peripheral nervous system development', 'regulation of small GTPase-mediated signal transduction', 'regulation of Ras protein signal transduction', 'aerobic respiration', 'membrane fusion', 'positive regulation of cell cycle', 'cellular respiration', 'heterocycle metabolic process', 'protein tetramerization' and 'regulation of Rho protein signal transduction' processes. Among the five dysregulated miRNAs identified by RT‑qPCR, miR‑126, miR‑200b and miR‑449a showed a strong association with nervous system development, cell differentiation, proliferation and apoptosis.

Let’s save our nurses and doctors!

Introduction: Several studies have shown that healthcare service is a dangerous workplace, but the reasons have been remained unexplained. Aim: The aim of the authors was to obtain data on the health condition of health care professionals and identify the underlying risk factors for the increased morbidity. Method: Health care data obtained from 276 bedside nurses in 2004 and 1250 hospital employees in 2009 were analysed. In addition, the fate of department directors of Szent György University Hospital in Székesfehérvár between 1979 and 2010 was recorded and the data were compared to those obtained from a smaller hospital in Budapest during the same time period. Results: The body mass index of bedside nurses between the age of 30–35 years reached the upper limit of normal (which occurred 5–10 years earlier as compared to the average population) and then it increased continuously above the average value. In hospital employees the increase of body mass index was accompanied by an increase in the frequency of chronic diseases such as hypertension, allergy, thyroid dysfunction, rheumatologic diseases, diabetes, peptic ulcer, cancer and depression. When the cause of death of the department directors who died between 1979 and 2010 was analyzed the authors found that cancer death occurred in 77% and 82% of department directors in Székesfehérvár and Budapest hospitals, respectively, while cancer death rate in 2011 was 25.4% in Hungary. Conclusions: The authors propose that continuous psychological stress, night shifts, nonstop standby and surcharge may all suppress the activity of the immune system. This proposal seems to be supported by novel psycho-neuro-immunological research data. The solution could be early prevention using stress control. Orv. Hetil., 2014, 155(52), 2082–2092.

Real-time qPCR identifies suitable reference genes for Borna disease virus-infected rat cortical neurons

Quantitative real-time reverse transcription polymerase chain reaction (RT-qPCR) is the most commonly-used technique to identify gene expression profiles. The selection of stably expressed reference genes is a prerequisite to properly evaluating gene expression. Here, the suitability of commonly-used reference genes in normalizing RT-qPCR assays of mRNA expression in cultured rat cortical neurons infected with Borna disease virus (BDV) was assessed. The expressions of eight commonly-used reference genes were comparatively analyzed in BDV-infected rat cortical neurons and non-infected control neurons mainly across 9 and 12 days post-infection. These reference genes were validated by RT-qPCR and separately ranked by four statistical algorithms: geNorm, NormFinder, BestKeeper and the comparative delta-Ct method. Then, the RankAggreg package was used to construct consensus rankings. ARBP was found to be the most stable internal control gene at Day 9, and ACTB at Day 12. As the assessment of the validity of the selected reference genes confirms the suitability of applying a combination of the two most stable references genes, combining the two most stable genes for normalization of RT-qPCR studies in BDV-infected rat cortical neurons is recommended at each time point. This study can contribute to improving BDV research by providing the means by which to obtain more reliable and accurate gene expression measurements.

Glutamate and lipid metabolic perturbation in the hippocampi of asymptomatic borna disease virus-infected horses

Borna disease virus (BDV) is a neurotropic, enveloped, non-segmented, negative-stranded RNA virus that infects a wide variety of vertebrate species from birds to humans across a broad global geographic distribution. Animal symptomatology range from asymptomatic infection to behavioral abnormalities to acute meningoencephalitis. Asymptomatic BDV infection has been shown to be more frequent than conventionally estimated. However, the molecular mechanism(s) underyling asymptomatic BDV infection remain largely unknown. Here, based on real-time quantitative PCR and Western blotting, a total of 18 horse hippocampi were divided into BDV-infected (n = 8) and non-infected control (n = 10) groups. A gas chromatography coupled with mass spectrometry (GC-MS) metabolomic approach, in conjunction with multivariate statistical analysis, was used to characterize the hippocampal metabolic changes associated with asymptomatic BDV infection. Multivariate statistical analysis showed a significant discrimination between the BDV-infected and control groups. BDV-infected hippocampi were characterized by lower levels of D-myo-inositol-1-phosphate, glutamate, phosphoethanolamine, heptadecanoic acid, and linoleic acid in combination with a higher level of ammonia. These differential metabolites are primarily involved in glutamate and lipid metabolism. These finding provide an improved understanding of hippocampal changes associated with asymptomatic BDV infection.

Borna disease virus infection in cats

Bornaviruses are known to cause neurological disorders in a number of animal species. Avian Bornavirus (ABV) causes proventricular dilatation disease (PDD) in birds and Borna disease virus (BDV) causes Borna disease in horses and sheep. BDV also causes staggering disease in cats, characterised by ataxia, behavioural changes and loss of postural reactions. BDV-infection markers in cats have been reported throughout the world. This review summarizes the current knowledge of Borna disease viruses in cats, including etiological agent, clinical signs, pathogenesis, epidemiology and diagnostics, with comparisons to Bornavirus infections in other species.

Comprehensive analysis of endogenous bornavirus-like elements in eukaryote genomes

Bornaviruses are the only animal RNA viruses that establish a persistent infection in their host cell nucleus. Studies of bornaviruses have provided unique information about viral replication strategies and virus-host interactions. Although bornaviruses do not integrate into the host genome during their replication cycle, we and others have recently reported that there are DNA sequences derived from the mRNAs of ancient bornaviruses in the genomes of vertebrates, including humans, and these have been designated endogenous borna-like (EBL) elements. Therefore, bornaviruses have been interacting with their hosts as driving forces in the evolution of host genomes in a previously unexpected way. Studies of EBL elements have provided new models for virology, evolutionary biology and general cell biology. In this review, we summarize the data on EBL elements including what we have newly identified in eukaryotes genomes, and discuss the biological significance of EBL elements, with a focus on EBL nucleoprotein elements in mammalian genomes. Surprisingly, EBL elements were detected in the genomes of invertebrates, suggesting that the host range of bornaviruses may be much wider than previously thought. We also review our new data on non-retroviral integration of Borna disease virus.

Antigen tissue distribution of Avian bornavirus (ABV) in psittacine birds with natural spontaneous proventricular dilatation disease and ABV genotype 1 infection

Tissues of 10 psittacines from aviary 1 ("case birds") and 5 psittacines from different aviaries were investigated for the presence of Avian bornavirus (ABV) antigen by immunohistochemistry using a polyclonal serum specific for the viral nucleocapsid (N) protein. Seven of 10 case birds had clinical signs, and necropsy findings consistent with proventricular dilatation disease (PDD) while 3 case birds and the 5 birds from other aviaries did not exhibit signs and lesions of this disease. In birds with clinical signs of PDD, ABV antigen was largely limited to neuroectodermal cells including neurons, astroglia, and ependymal cells of the central nervous system, neurons of the peripheral nervous system, and adrenal cells. ABV antigen was present in the nuclei and cytoplasm of infected cells. In 2 case birds that lacked signs and lesions of PDD, viral antigen had a more widespread distribution and was present in nuclei and cytoplasm of epithelial cells of the alimentary and urogenital tract, retina, heart, skeletal muscle, and skin in addition to the mentioned neuroectodermal cells. ABV RNA was identified by reverse transcription polymerase chain reaction (RT-PCR) in tissues of all 7 case birds available for testing from aviary 1, including 4 birds with PDD lesions and the 3 birds without PDD lesions. Sequencing and phylogenetic analysis indicated the presence of ABV genotype 1 in all cases. Findings further substantiate a role of ABV in PDD of psittacine bird species.

Exacerbation of chronic inflammatory diseases by infectious agents: Fact or fiction?

Chronic inflammatory diseases caused by obesity represent critical public health concerns worldwide. In these diseases such as metabolic syndrome, diabetes and atherosclerosis, adipose tissue acts as an endocrine organ that releases large quantities of inflammatory mediators into circulation. Besides classically recognized effectors on the development of obesity and resultant conditions, infection has attracted attention as an enhancer of chronic inflammatory diseases. Infectious diseases have long been associated with obesity, metabolic syndrome, diabetes and atherosclerosis. However, the infectious hypothesis for chronic inflammatory diseases has been challenged by inconclusive clinical trials. Nevertheless, the large body of evidence accumulated over decades on the association of infectious diseases with obesity, diabetes and cardiovascular disease should not be disregarded. Instead, re-formulation of hypotheses of the mechanisms by which microbes affect obesity-associated diseases may be required with an emphasis on the early events in the progression of such diseases and the multifactorial nature of pathogen-host interactions. This review focuses on pathogens that directly promote obesity and on pathogens that cause chronic infections and thereby enhance metabolic diseases in obese patients. A new perspective on the interaction between infections and obesity-related diseases may improve management of chronic inflammatory diseases that rank high among global threats to human health.