K. Frese

Axonal transport of Borna disease virus along olfactory pathways in spontaneously and experimentally infected rats

In this study it has been shown that infection of mother rats by Borna disease virus (BDV) from infected newborns led to a fatal disease. This differed both in clinical symptoms and in histological alterations from the form of the disease which occurred after intracerebral (i.c.) infection. Both parameters were, however, similar to those seen after experimental intranasal (i.n.) infection of adult rats. Detailed immunohistological studies showed clearly that after experimental i.n. infection, the infecting virus migrates intraaxonally from the neuroreceptors in the olfactory epithelium into the brain. It is therefore suggested that i.n. transmission is an important route of natural BDV infection.

Borna disease, a possible hazard for man?

SummaryEvidence is presented that Borna disease (BD) virus, which is known to cause encephalopathy in horses, sheep, and a broad range of experimental animals, or a related agent, can infect man and may induce mental disorders. BD virus-specific antibodies could be demonstrated in 4–7% of sera (depending on origin) from more than 5000 psychiatric or neurological patients from Germany, U.S.A. and Japan. Antibodies from seropositive patients reacted with a BD virus-specific protein translated by RNAs which were transcribed from a cDNA clone obtained from BD virus-infected tissues. When the cerebrospinal fluid from three seropositive patients was inoculated into rabbits or rabbit embryonic brain cell cultures, evidence was obtained that suggests the presence of BD virus or a related agent.

Replication of Borna disease virus in rats: age-dependent differences in tissue distribution

There are age-dependent differences in the tissue distribution of Borna disease (BD) virus in rats infected intracerebrally. While in adult rats BD virus replication is restricted to neural cells, in neonatally infected rats infectious virus or viral antigens were found in the cells of most organs. The possibility that differences in the immune status between newborn and adult animals are responsible for different tissue susceptibility could be excluded.

Determination of immune cells and expression of major histocompatibility complex class II antigen in encephalitic lesions of experimental borna disease

SummaryAfter intracerebral infection with Borna disease virus adult Lewis rats develop a virus-induced immunopathological reaction resulting in severe neurological symptoms and a non-purulent meningoencephalitis. The composition of inflammatory cells and major histocompatibility complex (MHC) class II antigen expression during the course of the infection was investigated using immunocytochemistry with a panel of monoclonal antibodies (mAb). Macrophages and lymphocytes of the T helper phenotype (CD4+) were dominant at all stages of infection, whereas T suppressor/cytotoxic lymphocytes (CD8+) were less frequent. B lymphocytes and plasma cells occurred mainly during later stages of the disease and marked parenchymal deposition of immunoglobulin developed. Beginning 10 days after infection massive expression of MHC class II antigen was noted up to the termination of experiments 70 days after infection. Besides lymphatic cells and macrophages, cells morphologically resembling microglia expressed this antigen. Furthermore, ependymal cells were found positive for MHC class II expression during infection whereas astrocytes remained negative. These findings are consistent with previous results which provide evidence for a delayed-type hypersensitivity reaction being operative in the pathogenesis of Borna disease.

Spontaneous and Experimental Glycoprotein Storage Disease of Goats Induced by Ipomoea carnea subsp fistulosa (Convolvulaceae)

Spontaneous and experimental poisoning with the swainsonine-containing and calystegine-containing plant Ipomoea carnea subsp fistulosa is described. Three of 8 goats presenting with emaciation, weakness, symmetrical ataxia, posterior paresis, proprioceptive deficits, abnormal posture, abnormal postural reaction, and muscle hypertonia were necropsied. I fistulosa was suspected to be the cause of the neurologic disease in all cases. An experiment was conducted to confirm the diagnosis using 12 goats and diets containing 3 different concentrations of the plant. All goats fed I fistulosa developed neurological signs that were similar to those observed in the spontaneous intoxication. Muscle atrophy and pallor were the only macroscopic changes observed in spontaneous and in experimental intoxication. Histological lesions of spontaneous and experimental animals were similar. The most prominent lesion was cytoplasmic vacuolation in neurons of the central and the autonomous nervous system, pancreatic acinar cells, hepatocytes, Kupffer cells, follicular epithelial cells of the thyroid gland, and macrophages of the lymphatic tissues. Neuronal necrosis, axonal spheroids formation, and astrogliosis were additionally observed in the brain. Ultrastructurally, the cytoplasmic vacuoles consisted of distended lysosomes surrounded by a single-layered membrane. Nonreduced end-rests or sequence of α-Man, α-Glc, β(1–4)-GlcNAc, and NeuNAc on lysosomal membrane were revealed by lectin histochemistry. Samples of plants used in the experimental trial contained swainsonine and calystegine and their intermediary derivate. We conclude that I fistulosa induces a glycoprotein storage disease primarily based on the inhibition of the lysosomal α-mannosidase by the alkaloid swainsonine.

Distribution of Borna disease virus in the brain of rats infected with an obesity-inducing virus strain.

Experimental infection of Lewis rats with Borna disease virus (BDV), a nonsegmented, single‐stranded RNA virus, usually causes an immune‐mediated biphasic neurobehavioral disorder. Such animals develop a persistent infection of the CNS with viral antigen expression in all brain regions and a disseminated nonpurulent meningoencephalitis. Interestingly, intracerebral infection of Lewis rats with a BDV‐variant (BDV‐ob) causes a rapid increase of body weight with the development of an obesity syndrome without obvious neurological signs. The obese phenotype is correlated with a characteristic distribution of inflammatory lesions and BDV‐antigen in the rat brain. Infiltration with mononuclear immune cells and viral antigen expression are restricted to the septum, hippocampus, amygdala and ventromedian tuberal hypothalamus. Therefore, infection with the obesity‐inducing BDV‐ob results most likely in neuroendocrine dysregulations leading to the development of an obesity syndrome. This might be due to the restriction of viral antigen expression and inflammatory lesions to brain areas which are involved in the regulation of body weight and food intake. The BDV‐induced obesity syndrome represents a model for the study of immune‐mediated neuroendocrine disorders caused by viral infections of the CNS.

Borna disease virus-induced meningoencephalomyelitis caused by a virus-specific CD4 + T cell-mediated immune reaction

After intracerebral inoculation of Borna disease virus (BDV). Lewis rats develop a persistent infection of the central nervous system which is pathohistologically represented by perivascular encephalitic lesions predominantly in the grey matter. In previous studies it has been shown that a cell-mediated immune response causes Borna disease (BD). In order to define further the immune cell responsible for this immunopathological disease, a BDV-specific T cell line, NM1, was established and cultured in vitro. Phenotypically this T cell line was characterized by cytofluorometry as CD4-positive (CD4+). Proliferation assays with syngeneic and allogeneic antigen-presenting cells, and blocking experiments with monoclonal antibodies, revealed major histocompatibility complex class II antigens to be restriction elements. After passive transfer of this virus-specific CD4+ T cell into immunosuppressed BDV-infected recipients, full-blown disease could be induced. Immunohistological examination of the cells involved in perivascular inflammatory infiltrates in BDV-infected rats and in recipients of the NM1 T cell line revealed a dominance of macrophages and CD4+ T cells. The presence of these cells in encephalitic lesions strongly suggests a delayed type of hypersensitivity reaction as the pathogenetic mechanism of BD.

Effect of Borna disease virus infection on athymic rats.

Homozygous athymic nude rats (rnu/rnu) infected intracerebrally with Borna disease virus produced relatively high titres of infectious virus in the central nervous system. However, no clinical signs of disease or pathological alterations could be found during a 100 day observation period. In contrast, heterozygous euthymic albino littermates (rnu/+), which were used as controls, reacted in a similar manner to immunocompetent Lewis rats. They developed behavioural alterations which coincided with encephalitis and retinitis. The results obtained confirm our previous concept that the genesis of Borna disease, at least in rats, is attributed to a cellular immune response.

Studies on the genetic control of resistance of black hooded rats to Borna disease

In contrast to Lewis (LEW) and Wistar rats, black hooded (BH) rats inoculated with Borna disease (BD) virus developed neither encephalitis nor clinical disease despite persistent replication of the virus in the central nervous system. In comparison to LEW rats, production of virus-specific antibodies was significantly delayed in BD-resistant BH rats, even though identical titres were finally reached. The different susceptibility in LEW and BH rats was studied further by investigating responses of F1 hybrid animals. Although these rats developed encephalitis, they did not become sick. The differences in host responses for BD virus were found to be genetically determined but were independent of class I or class II major histocompatibility complex gene products or to genes responsible for lymphocyte differentiation.

Clinical and Morphologic Changes in Ewes and Fetuses Poisoned by Ipomoea Carnea Subspecies Fistulosa

Intoxication with Ipomoea carnea has been reported in goats, sheep, and cattle in tropical regions worldwide. The disease has been characterized only in goats; therefore, the present study was conducted in sheep. Nine animals were fed feed rations that contained 3 different concentrations of Ipomoea carnea subsp. fistulosa. Individual intake varied between 10.5 and 135.2 g of fresh plant per kilogram of body weight (BW) per day. Animals first showed clinical signs between day 43 and day 63. The maximum survival time was 133 days. Sheep presented with weight loss and neurologic abnormalities. Neurologic signs were dominated by marked depression, abnormal behavior, and musculoskeletal weakness, with poorly defined motor and proprioceptive deficits. In mature animals, cytoplasmic vacuolation, consistent with accumulation of secondary lysosomes, affected neurons, astrocytes, exocrine pancreatic acinar epithelia, hepatocytes and Kupffer cells, renal tubular epithelia, thyroid follicular epithelia, cortical adrenal epithelia, endothelia and perivascular cells, and macrophages in lymph nodes and spleen. In the central nervous system, there was axonal degeneration and astrogliosis. Abortion was observed as early as day 22 of the trial. In fetal tissues and placenta of chronically poisoned ewes, cytoplasmic vacuolation was histologically detected in neurons, exocrine pancreatic acinar epithelia, hepatocytes, renal tubular epithelia, and thyroid follicular epithelia. All the sheep developed a glycoprotein storage disease, with lysosomal accumulation of N-glycosidically linked oligosaccharides, which was indistinguishable from that induced by the alkaloid swainsonine alone.