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

Application of antibodies against Borna disease virus phosphoprotein and nucleoprotein on paraffin sections

In order to study the application of antibodies against recombinant proteins for detecting Borna disease virus (BDV) phosphoprotein (p24) and nucleoprotein (p40) (BDV‑p24/p40) on paraffin sections by immunohistochemistry. The purified fusion p24 and p40 proteins were used for the preparation of polyclonal and monoclonal anti‑p24 and anti‑40 antibodies, which were confirmed by ELISA and western blotting. Paraffin sections were made from BDV‑infected Sprague‑Dawley (SD) rats (n=20), PBS‑injected SD rats (n=20), normal SD rats (n=20) and normal C57 mice (n=20). Immunohistochemical staining was performed according to the EnVision™ two‑step protocol. Heat‑mediated antigen retrieval was performed using the retrieval buffer sodium citrate (1 mM; pH 6.0). All the antibodies against recombinant proteins exhibited good sensitivity and specificity. There were significant differences between the BDV‑infected group and the BDV‑uninfected group for poly‑ and monoclonal anti‑p24 and ‑p40 antibodies. These antibodies against recombinant proteins may be used effectively to detect BDV p24 and p40 in paraffin sections.

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.

Slowly progressive lymphohistiocytic meningoencephalomyelitis in 21 adult cats presenting with peculiar neurological signs

Twenty-one cats presented with a history of slowly progressive neurological signs characterised by a stiff extended tail, behavioural changes, and spastic and ataxic gait. All cats had outdoor access and lived in the same geographical rural area in north-east Scotland. Histological findings were consistent with lymphohistiocytic meningoencephalomyelitis. Immunohistochemistry ruled out 15 pathogens and showed a significant expression of the interferon-inducible Mx protein, suggesting an as yet unidentified infective or environmental immunogenic trigger as the possible causative agent. The late age at onset (mean 9 years), the very slow progression of clinical signs (mean 11 months) and the peculiar clinical presentation (particularly the posture of the tail) have not been reported previously in cats with lymphohistiocytic meningoencephalomyelitis.

CNS disease in the cat: current knowledge of infectious causes

PRACTICAL RELEVANCE

Neurological disease is a relatively common reason for referral, constituting approximately 10% of the feline referral caseload. Nearly one-third to one-half of these cases may be infectious in origin. As such, an awareness of infectious diseases causing central nervous system (CNS) signs in cats, and their clinical diagnosis and management, is relevant to anyone dealing with cats on a regular basis.

GLOBAL IMPORTANCE

Some conditions (eg, rabies) are more common in certain countries than others. Conditions such as feline infectious peritonitis (FIP) and toxoplasmosis are of global significance.

PATIENT GROUP

Many infectious diseases may affect any feline population. Some, such as FIP, are more common in pedigree households, whereas others such as toxoplasmosis, feline immunodeficiency virus (FIV) or feline leukaemia virus (FeLV) infections, are more likely to affect a single cat with an outdoor lifestyle.

EQUIPMENT

All patients benefit from thorough history taking and clinical, neurological and ophthalmic examinations, which all require minimal equipment. Infectious diseases may often be diagnosed on blood samples; however, definitive diagnosis may require more extensive investigation involving cerebrospinal fluid analysis or advanced imaging necessitating access to computed tomography or magnetic resonance imaging.

EVIDENCE BASE

The information in this review, which summarises current knowledge of infectious diseases affecting the CNS, is collated from publications on the infectious diseases comprising previous research papers, review articles, case series, case reports and textbooks, supplemented by the clinical experience of the authors.

Borna disease virus antibody and RNA from peripheral blood mononuclear cells of race horses and jockeys in Korea

OBJECTIVE

During the last two decades, Borna disease virus (BDV) has received much attention as a possible zoonotic agent, particularly as a cause of psychiatric disease. Although several studies have shown that BDV is present in Asia, BDV has not been detected in Korea. This study was designed to further investigate the presence of BDV infection in Korea.

METHODS

Blood samples were taken from 39 race horses and 48 jockeys. Antibody to BDV was detected by indirect immunofluorescence antibody test and RNA of BDV by real time reverse transcriptase PCR (rRT-PCR).

RESULTS

No evidence of BDV was detected in either the horses or the jockeys group.

CONCLUSION

Our results suggest that BDV infection may not be endemic in Korea. Further studies with novel diagnostic tools are required to clarify the prevalence of BDV infection in Korea.

Prevalence of Borna disease virus antibodies in healthy Japanese black cattle in Kyushu

Epidemiological studies have demonstrated that asymptomatic infection of Borna disease virus (BDV) is found in various species of animals in Japan. Recent reports have also revealed that neurological diseases caused by this virus could exist in horses, cattle, a dog, and cats in this country. In this study, we investigated seroprevalence of BDV antibodies in Japanese black cows reared in Kyushu, the southernmost main island of Japan, using ELISA and Western-immunoblotting. Of 101 serum samples, 11 (10.9%) and 21(20.7%) sera were identified as having antibodies to the BDV N and P antigens, respectively. Among the positive sera, three cows (2.9%) were seropositive for both of the antigens. Furthermore, interestingly, only female cows showed antibodies to P, whereas N antibodies were detected in male and female cows with a comparative ratio. Together with previous studies, our results indicate that BDV might be widely spread in cattle raised in Japan. Furthermore, this is the first report to show that beef cattle, Japanese black cattle, have antibodies against a possible zoonotic pathogen, BDV.

Infectious diseases of the central nervous system

Neurologic disease is seen commonly in cats, with infectious causes accounting for 30-45% of cases. However, since a specific infection cannot be identified in 12-40% of these cases, it is essential that we try to understand these cases better in the hope that we can eventually identify the cause(s), and so determine how best to treat and/or prevent them.

2'-fluoro-2'-deoxycytidine inhibits Borna disease virus replication and spread

Borna disease virus (BDV) causes neurological diseases in a variety of warm-blooded animal species, possibly including humans. To date, there is no effective treatment against BDV infection. Recently, we reported on the antiviral activity of 1-beta-D-arabinofuranosylcytosine (Ara-C). However, Ara-C's cytotoxic side effects are a major obstacle for its therapeutic use. Herein, we demonstrate that the nucleoside analog 2'-fluoro-2'-deoxycytidine (2'-FdC) exhibits potent antiviral activity against BDV. Importantly, 2'-FdC-associated cytotoxicity is negligible, indicating 2'-FdC as an excellent candidate for the development of antiviral therapy against BDV.

Humoral immune response against Borna disease virus (BDV) in experimentally and naturally infected cats

In order to investigate the peripheral and intracerebral humoral immune response against Borna disease virus (BDV) in cats, serum and cerebrospinal fluid (CSF) samples from experimentally and naturally BDV-infected cats were analysed in two different test systems (indirect enzyme-linked immunosorbent assay and indirect immunofluorescent test). The experimentally infected cats developed high antibody titres against the major immunogenic BDV-proteins, p24 and p40. In contrast, the naturally infected cats showed a comparatively weak humoral immune response. The experimentally infected cats were inoculated with either BDV laboratory strain V or a feline BDV-isolate. Some differences existed between the two groups of cats. The former group developed a higher response against p40, whereas the latter group showed, beside the p40-response, a more pronounced p24-response, similar to the situation in the naturally infected cats.

Borna disease in a dog in Japan

Borna disease (BD) was diagnosed in a 3-year-old male Welsh corgi suffering from a severe and acute progressive disorder of the central nervous system. Histopathologically, neuronal lesions were characterized by a non-suppurative encephalomyelitis dominated by large perivascular cuffs consisting of lymphocytes, macrophages and plasma cells; also present were inflammatory cell infiltrates in the neural parenchyma, neuronophagia and focal gliosis. Strong immunolabelling with BD virus (BDV) p40 antibody was diffusely distributed in the cytoplasm of small and large neurons in areas of the brain with and without inflammatory changes, and also in the spinal cord. Positive hybridization signals with BDV p40 sense and antisense riboprobes were seen in the nucleus and cytoplasm of the neurons throughout the whole brain and spinal cord. BDV p24 RNA in formalin-fixed brain tissue was detected by reverse transcriptase (RT)-nested polymerase chain reaction (PCR). BDV p24 RNA-positive signals were detected in the temporal lobe. This is the first report of spontaneous canine BD in Japan.

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.

Detection of antibodies to Borna disease virus in Turkish cats by using recombinant p40

Recombinant p40 produced by baculovirus was used in an ELISA to screen samples of serum taken from 80 cats in Istanbul. The sera were also analysed for feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV). Antibodies to Borna disease virus- (BDV) p40 were detected in 34 (42-5 per cent) of the 80 cats. Seventy-three per cent of the sera which were positive for FIV and 26 per cent of the sera which were negative for FIV had antibodies to BDV. There was no difference in the percentage of sera which were positive for BDV between the cats that were positive or negative for FeLV. Three of the cats had neurological disease and two of these had antibodies to BDV. Six sera with low, medium or high optical densities (ODS) by ELISA were analysed by Western blotting. Only the sera with medium and high ODS reacted specifically with p40 at a dilution of 1 in 1,000.

Detection of anti-borna disease virus antibodies from cats in Asian countries, Japan, Philippines and Indonesia using electrochemiluminescence immunoassay

Anti-Borna disease virus (BDV) antibodies were detected from cats in Japan, Philippines and Indonesia by using electrochemiluminescence immunoassay. Positive rates were 3.1%, 3.8% and 2.0% in Japan, Philippines and Indonesia, respectively. There was no differences in the positive rate of anti-BDV antibodies between male and female cats and among habitats. While, a significantly (P<0.05) higher prevalence (6.5%) was found in the oldest age group (more than 6 years) cats.

Neurological diseases and viral dynamics in the brains of neonatally borna disease virus-infected gerbils

Borna disease virus (BDV) is a noncytolytic, neurotropic RNA virus that causes a chronic neurological disease in a wide variety of animal species. To develop a better understanding of the correlation between neurological disorders caused by BDV infection and virus distribution in the brain, we investigated viral dynamics in the central nervous system (CNS) of neonatally BDV-infected gerbils during the late stage of infection. Despite the severe symptoms and aggressive proliferation of BDV in the infected gerbils, no apparent neuroanatomical abnormalities or neuronal cell loss was observed in the infected gerbil brain. Furthermore, no or only minimal infiltration was observed in the infected gerbil brain. By in situ hybridization and real-time PCR analyses, we demonstrated that the predominant area of expression of BDV mRNA, as well as the protein, was shifted in the brain in association with progression of disease. In nondiseased gerbils, the virus replication was predominantly detected in the cerebral cortex and hippocampus of the CNS. On the other hand, diseased animals showed a high level of expression in the lower brain stem and cerebellum, especially in Purkinje cell neurons. These observations suggested that significant replication of the virus in specific areas of the CNS is critical for development of the neurological disorders in BDV-infected neonatal gerbils.

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.