Clinical, Serologic, and Histopathologic Characterization of Experimental Borna Disease in Ponies

Abstract

Abstract. Borna disease was originally described as an equine neurologic syndrome over 200 years ago, although the infectious etiology of the disorder was unproven until the early 20th century. Borna disease virus (BDV) was finally isolated from horses dying of the disorder, and that virus has been used to experimentally reproduce Borna disease in several species of laboratory animals. However, BDV has never been inoculated back into horses to experimentally and etiologically confirm the classic clinical, pathologic, and serologic characteristics of the disease in that species. Three ponies were intracerebrally inoculated with different amounts of BDV and were evaluated clinically, serologically, and neurohistopathologically. All 3 animals developed the clinical signs characteristically described for naturally occurring Borna disease, including ataxia, torticollis, postural unawareness, rhythmic repetitive motor activities, muscle fasciculation, and cutaneous hyperesthesia and hypoesthesia over several body surfaces. Two ponies died after rapid onset of these signs 28-30 days postinoculation. The third animal made a nearly complete clinical recovery. Seroconversion occurred only after the onset of signs and to a marked degree only in the convalescent animal. Virus was recovered postmortem from 2 of the 3 ponies, and a BDV-specific nucleic acid sequence was detectable in all 3 animals using a reverse transcription-polymerase chain reaction procedure. Gross neural lesions were absent, but histopathologically there was generalized intense mononuclear perivascular cuffing, glial nodule formation, and astrocytosis in all 3 brains. Confirming a diagnosis of Borna disease is difficult and perhaps best accomplished using a combination of the clinical, serologic, and histopathologic indicators of this unusual disease supported by positive reverse transcription-polymerase chain reaction findings.Borna disease (BD) was originally described as a sporadic, usually fatal neurologic affliction of horses and sheep in southern Germany. 16 The viral etiology of the disease was eventually proven, and the etiologic agent, Borna disease virus (BDV), was propagated in cell cultures. 16 In recent years, however, natural or experimental infections with BDV have been confirmed or suspected in a much wider range of host species, including cattle, cats, ostriches, rodents, rabbits, and possibly humans. 2,4,8,[13][14][15] In vitro understanding of BDV has also increased dramatically in the last decade as cell culture and molecular techniques have been used to study the virus. [5][6][7]14 BDV is an 8.9-kilobase negative polarity, nonsegmented, enveloped RNA virus that encodes 5 open reading frames (ORF). 7 At least 3 of these ORFs are expressed in infected animals and cell cultures, and animals may respond serologically to these 3 expressed proteins: p14, p24, and p38-40. 3,14 There are no published reports of experimental Received for publication October 9, 1997.BDV infections in horses, which have historically been considered the prototyp...

Enhanced Neurovirulence of Borna Disease Virus Variants Associated with Nucleotide Changes in the Glycoprotein and L Polymerase Genes

“…Following hematoxylin and eosin (H/E) staining of 8-m-thick sections, the severity of the encephalitic response (SOE score) was scored in a blinded fashion with a 0-to-4 scoring system as described previously (44). To examine viral antigen distribution in the brain, sections from each brain were stained by avidin-biotin immunohistochemistry (Vector, Burlingame, Calif.) by using horse anti-BDV serum (29) followed by biotinylated anti-horse immunoglobulin G (Vector) as described previously (7).…”

“…After 4 days at 37°C, a fluorescent focus-forming unit (FFU) assay was performed to visualize infected cells (7). The cells were fixed with cold acetone for 10 min and analyzed for immunofluorescent signal by using BDV-infected horse serum (29). Virus titers were calculated by assuming that each fluorescent focus of infected cells originated from infection with a single replication-competent virus particle.…”

Borna disease: current knowledge and virus detection in France

“…Antibody titers are usually very low in BDV-infected animals and their detection requires particularly sensitive techniques [36,62]. Antibodies are detectable in 100% cases during the acute phase of the disease but they are hardly detectable in a subacute or chronic disease.…”

Construction of an internal standard used in RT nested PCR for Borna Disease Virus RNA detection in biological samples

“…Its natural hosts are classically described as horses and sheep but infections in donkeys, cattle, rabbits, cats and ostriches have also been described [10]. If serological data are abundant about BDV infections in various animals and humans presenting neurological disorders [6,12,13,15,17], BDV RNA detection by in vitro genomic amplification is one of the most efficient methods to detect viral infection. To detect the virus genome in infected tissues, it is often necessary to use the Polymerase Chain Reaction (PCR) method in two rounds of amplifications, i.e.…”