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Biomedical subjects

M Vandevelde

Publications and source records attributed to M Vandevelde.

At least 55 records · Page 3Linked to original sources
PubMed1997

Determinants of persistence in canine distemper viruses.

Viral persistence in the central nervous system is the driving force behind the chronic progressive disease caused by natural canine distemper virus (CDV) infection in dogs. Persistence of CDV is associated with non-cytolytic spread and impaired viral budding. Since budding is to a large extend dependent on the nucleocapsid-(N) and matrixproteins (M) of the virus, we analyzed the nucleotide- and deduced amino acid sequences of the corresponding genes of a spectrum of CDV strains, that differ with respect to virulence and persistence in vivo and in vitro. The wild type CDV (A75/17), which is capable of causing a persistent infection in vivo was compared to two tissue culture adapted CDV strains (passaged A75/17-CDV and Rockborn-CDV), which CDV strains, that differ with respect to virulence and persistence in vivo and in vitro. The wild type CDV (A75/17), which is capable of causing a persistent infection in vivo was compared to two tissue culture adapted CDV strains (passaged A75/17-CDV and Rockborn-CDV), which retain a residual virulence and the capacity to spontaneously persist in vitro. A modified distemper virus (Snyder Hill-CDV), which is neurovirulent but not capable of causing a persistent infection in vivo, and an avianized virus (Onderstepoort-CDV) which is completely apathogenic and spreads by budding in cell cultures were also examined. Differences were found in the C-terminal of the nucleocapsid protein, which--comparing the two extremes of the spectrum (wild A75/17-CDV and OP-CDV)--lead to changes of the predicted protein structure. Such changes could affect the budding process and thus play a role in persistence. Marked changes in the M-gene were found in its non-coding region: the nucleotide sequences of the SH-CDV and OP-CDV differed considerably from the other three strains. Moreover, an additional second open reading frame was detected in the 'non-coding' region of the M gene in the wild A75-CDV, the two tissue culture adapted CDV strains and SH-CDV, but not in OP-CDV. The presence of this additional open reading frame correlated with the ability to cause a spontaneous persistent infection in vitro. Our findings support the notion that both N- and M-genes of CDV harbor determinants of viral persistence.

Amino Acid Sequence↗
PubMed1997

Comparison of inducible nitric oxide synthase expression in the brains of Listeria monocytogenes-infected cattle, sheep, and goats and in macrophages stimulated in vitro.

The expression of inducible nitric oxide synthase (iNOS) was studied in the brains of cattle, sheep, and goat that succumbed to a natural infection with Listeria monocytogenes. The lesions in infected brains are characterized by microabscesses, perivascular cuffs, gliosis, glial nodules, and large areas of malacia. Using immunocytochemistry, we detected bacteria in microabscesses, particularly in sheep and goats, and in areas without signs of inflammation, but not in perivascular infiltrates. iNOS was expressed by macrophage (Mphi)-type cells of microabscesses and glial nodules but rarely by Mphi in areas of malacia, as determined by immunohistochemistry with iNOS-specific antibodies. iNOS was not detected in perivascular cuffs. Major histocompatibility complex class II molecules (MHC-II), another marker of cell activation, showed a different pattern of distribution. Perivascular cuffs contained high numbers of MHC-II-positive cells, including some with Mphi characteristics. Microabscesses in sheep and goats showed low expression of MHC-II, particularly in iNOS-expressing cells. In cattle, the expression of markers for activated or recruited phagocytes, the calcium-binding proteins S100A8 and S100A9 (formerly called MRP-8 and MRP-14, respectively), was largely restricted to cells showing weak or undetectable iNOS expression; iNOS-positive Mphi showed a low expression of S100A8 and S100A9. Thus, iNOS is expressed by a restricted subset of Mphi in listeric encephalitis. In cultured sheep and goat Mphi, a low proportion of cells expressed iNOS upon activation by L. monocytogenes and gamma interferon, resulting in nitrite generation at least 1 order of magnitude lower than that in similarly treated cattle Mphi. Since these species differences were much less obvious in vivo, it appears that the well-known species variation in iNOS expression by Mphi could reflect an in vitro phenomenon.

Animals↗
PubMed1997

[Frequency of neurologic diseases in cattle].

The cases of neurological diseases at the Institute of Animal Neurology, University of Berne, from 1985-1994 were assessed. During this period 532 cattle with neurological symptoms were examined. After 1980 differential diagnostic investigation of rabies negative brains were not pursued anymore and the number of examined cattle brains had declined to 25-30 per year. With the occurrence of bovine spongiform encephalopathy (BSE) in 1990 in Switzerland the number of cattle brains examined has increased to 75-80 yearly. The most frequently diagnosed neurological diseases found are BSE, followed by listeriosis and viral encephalitides.

Animals↗
PubMed1996

Neuronal degeneration in brain stem nuclei in bovine spongiform encephalopathy.

In 57% of 151 BSE positive brains of Swiss cattle, degenerating neurons were found in BSE predilection sites, either single scattered (34%) or involving large parts of brain stem nuclei (23%). The lesion consisted of central chromatolysis, shrinkage, karyolysis or nuclear pyknosis. In 43% of the BSE positive brains no neuronal changes besides vacuolation were present. Neuronal degeneration other than vacuolation alone is not pathognomonic for BSE but, according to our findings, seems to be of some importance together with the typical vacuolation of neuropil and neurons. There is no correlation between extent of these degenerative changes and accumulation of PrPSc protein, determined by immunohistochemistry. The significance remains obscure, yet as it had not been seen in cattle brains before the outbreak of BSE in Switzerland in 1990 it certainly is linked to the disease. Possible pathogenetic mechanisms are discussed.

Animals↗
PubMed1995

Restricted infection with canine distemper virus leads to down-regulation of myelin gene transcription in cultured oligodendrocytes.

Canine distemper virus (CDV) induces oligodendroglial degeneration and multifocal demyelination in the central nervous system. The mechanism of oligodendrocyte degeneration is not understood but it has been shown that there is a restricted infection of these cells without viral protein production. Using a combination of immunocytochemistry and in situ hybridization we were able to demonstrate the transcription of the entire virus genome throughout the whole observation period (7-35 days after infection) in oligodendrocytes in CDV-infected brain cell cultures. Therefore, the lack of viral protein and particle production can not be explained on the basis of a defective viral transcription. The present study also shows that a restricted infection of oligodendrocytes with CDV down-regulates the transcription of the major myelin genes coding for proteolipid protein, myelin basic protein (MBP) and myelin-associated glycoprotein in a very similar way. Using densitometry for in situ hybridization products of MBP in populations of normal and infected oligodendrocytes, an effect could be observed long before morphological changes were detectable. The present results strongly suggest that demyelination in distemper is induced by a restricted CDV infection of oligodendrocytes which down-regulates the expression of a variety of cellular genes, in particular those coding for myelin proteins. Consequently, the infected cells are no longer able to synthesize all the membrane compounds which are necessary for maintaining their structural integrity.

Animals↗
PubMed1995

Studies on canine distemper virus persistence in the central nervous system.

Chronic progressive demyelination in canine distemper virus (CDV) infection is associated with persistence of the virus in the nervous system. We studied persistence by examining expression of CDV mRNA corresponding to all genes of the virus as well as genomic CDV RNA in brain sections of dogs with acute and chronic demyelinating disease. All virus mRNAs were expressed in acute demyelinating lesions in a way similar to that seen in lymphoid tissues, the primary replication site of CDV. Their distribution corresponded very well with immunohistochemical detection of virus protein. In contrast, much more CDV mRNA than virus protein was found in gray matter areas suggesting that translation of CDV can be impaired in nervous distemper. Virus protein and RNA were cleared from chronic inflammatory demyelinating lesions. mRNA corresponding to the distal genes (F; H; L) of CDV disappeared first in inflammatory lesions for technical reasons associated with the particular mode of transcription of morbilliviruses. CDV RNA and protein persisted in chronically ill dogs in other areas of the CNS in which inflammation had not occurred. Our results suggest that persistence of CDV is favored by non-cytolytic spread of the virus and restricted infection of certain cells with reduced viral protein expression. Both tend to delay immune recognition of the virus.

Animals↗
PubMed1995

Neuroimmunological studies in steroid-responsive meningitis-arteritis in dogs.

The clinical and pathological expression of steroid-responsive meningitis-arteritis (SRMA) is predominantly neurological and the present study was therefore mostly concerned with the intrathecal humoral immune responses of 13 dogs suffering from the disease. All the dogs synthesised IgG intrathecally, indicating that the immune response in SRMA is in part specifically directed towards the central nervous system (CNS). Half of the dogs also had high levels of IgM only in the cerebrospinal fluid (CSF) and nearly all of them had high levels of IgA in the CSF as well as in the serum. Six of the dogs had circulating immune complexes in the serum, but not in the CSF. Neither IgM nor IgA rheumatoid factors were found. A chemotaxis assay revealed enhanced migration of neutrophils into the CSF in three cases. All the dogs had marked meningeal inflammation and arterial lesions of the meningeal blood vessels. Only one dog had arterial involvement outside the CNS. The acute vascular lesions consisted mostly of degenerative changes of the media and periarterial inflammation, and there was no evidence of immune complex deposition. Chronic lesions were mostly characterised by stenosis, adventitial thickening and periarteritis. Focal deposits of IgA were found in the vascular wall of one chronic case. It was concluded that the meningeal lesions in SRMA are a primary event, rather than the result of a generalised immune complex disease. These lesions are associated with an intrathecal humoral immune response, in which IgA appears to play a central role.(ABSTRACT TRUNCATED AT 250 WORDS)

Albumins↗
PubMed1995

The neurobiology of canine distemper virus infection.

Canine distemper virus (CDV) invades the nervous system and replicates in neurons and glial cell of the white matter during a period of severe viral induced immunosuppression. Demyelination occurs in infected white matter areas in the absence of inflammation. The mechanism of demyelination is not apparent because there is no ultrastructural evidence of viral replication in the oligodendrocytes, the myelin producing cells. However, brain tissue culture studies have shown that oligodendrocytes support transcription of all CDV genes and later on degenerate, although no viral proteins can be found in these cells. It remains to be shown how such a restricted infection leads to demyelination. Concomitant with immunologic recovery during the further course of the disease, inflammation occurs in the demyelinating lesions with progression of the lesions in some animals. A series of experiments in vitro suggested that chronic demyelination is due to a bystander mechanism associated with the virus-induced immune response in which antibody dependent cell-mediated reactions play an important role. The progressive, or even relapsing, course of the disease is associated with viral persistence in the nervous system. Persistence of CDV in the brain appears to be due to non-cytolytic selective spread of the virus with very limited budding. In this way CDV escaped immune surveillance.

Acute Disease↗
PubMed1995

Selective spread and reduced virus release leads to canine distemper virus persistence in the nervous system.

In primary dog brain cell cultures (DBCC) the attenuated canine distemper virus (CDV) is cytolytic, whereas virulent CDV is not. Thus, the question why cytolysis does or does not occur appears to be intimately associated with the mechanism of persistence. Persistence is most likely related to the way these viruses replicate. In the present study we used morphological and immunocytochemical approaches to compare several aspects of virus replication between a cytolytic and a virulent CDV strain using DBCC to study both strains. Quantitative measurements did not detect a difference in the rate of virus protein synthesis at the level of the single cell, between the two types of infection. Electron microscopical results and virus titration experiments showed marked differences in virus spread and virus release. Immunocytochemical studies showed differences in the distribution of the nucleocapsid and matrix proteins between the two infections. Budding and cytolysis are strongly limited in the virulent A75/17-CDV infection as compared to attenuated viruses. This is probably due to structural changes in the virus proteins leading to modifications of virus assembly. Thus the present study supports a mechanism of CDV persistence through a type of virus maturation and spread by which very little virus is released outside of the cell.

Animals↗
PubMed1995

In situ hybridization and immunohistochemistry for prion protein (PrP) in bovine spongiform encephalopathy (BSE).

In about 5% of the cows showing clinical signs of bovine spongiform encephalopathy (BSE) the histopathological examination is not conclusive. In order to rule out BSE in these cases, additional methods are necessary. For that reason, non-radioactive in situ hybridization (ISH) was performed using a riboprobe against the messenger RNA coding for the prion protein (PrP). In addition, a polyclonal antibody for immunohistochemistry (IHC) was generated against a synthetic peptide derived from bovine PrP. ISH and IHC were used to analyse brain sections of cattle suffering from BSE and various neurological diseases including four cows with clinically suspect but histologically unconfirmed BSE. ISH revealed no differences in localization, distribution and neuronal levels of PrP mRNA between BSE positive and negative cattle. However, there was a BSE-specific staining pattern in IHC allowing to exclude BSE the four suspected cases. Additionally, IHC for PrP is an elegant alternative to search for scrapie associated fibrils by electron microscopy.

Animals↗
PubMed1995

Canine distemper virus persistence in the nervous system is associated with noncytolytic selective virus spread.

Canine distemper virus (CDV), a negative-strand RNA morbillivirus, causes a progressive demyelinating disease in which virus persistence plays an essential role. The antiviral immune response leads to virus clearance in the inflammatory lesions. However, CDV can replicate and persist outside these inflammatory lesions within the brain. How CDV is capable of persisting in the presence of an effective antiviral immune response is poorly understood. In the present investigation, we studied several aspects of virus replication in primary dog brain cell cultures (DBCC), comparing an attenuated CDV strain and a virulent CDV strain. Confluent DBCC were infected with either virulent A75/17-CDV or attenuated Onderstepoort-CDV and monitored for 60 days. Persistence was not associated with defective virus production, because all mRNAs and corresponding proteins were continuously expressed in the noncytolytic infection. Quantitative measurements did not detect a difference between the two types of infection in the rate of virus transcription and protein synthesis at the level of the single cell. However, electron microscopy and virus titration experiments showed that in the persistent CDV infection virus budding is strongly limited compared with that of the attenuated virus. Morphometry and immunocytochemistry showed profound differences in the way the two viruses spread in the culture. The attenuated CDV spread randomly to immediately adjacent cells, whereas persistent CDV spread selectively to more-distant cells by way of cell processes. In conclusion, the present study supports a mechanism of CDV persistence through selective spread by way of cell processes, enabling virulent CDV to invade the central nervous system without the need of releasing much virus into the extracellular space.

Animals↗
PubMed1994

Intrathecal synthesis of major immunoglobulin classes in inflammatory diseases of the canine CNS.

The IgG index, IgM and IgA contents in cerebrospinal fluid and serum were examined retrospectively using an enzyme-linked immunosorbent assay (ELISA) in 69 dogs with inflammatory central nervous system (CNS) diseases of various aetiologies. Fifteen normal dogs were used as controls. After measuring IgG and albumin contents in serum and cerebrospinal fluid (CSF), the IgG index was calculated according to the formula of Link and Tibbling to demonstrate intrathecal immunoglobulin synthesis. A surprisingly high number of animals with encephalitis, including dogs with protracted diseases such as chronic distemper encephalitis and granulomatous meningoencephalomyelitis, showed in addition to an elevated IgG production evidence of intrathecal IgM and IgA production. The highest values of intrathecal as well as systemic IgA levels were found in dogs suffering from steroid responsive meningitis-arteritis. It was concluded that the control of the humoral immune response in the brain differs from that in other tissues. Because of striking similarities between dogs and humans in respect to humoral neuroimmunological reactions, the dog can be considered to be a useful animal model for the study of the intrathecal humoral immune response.

Animals↗
PubMed1994

A chemiluminescence assay to detect antibodies to brain surface antigens in human sera.

A chemiluminescence assay was developed based on the interaction between antibodies binding to the surface of living brain cells in culture and macrophages. Such interaction leads to production of reactive oxygen radicals which can be measured by a chemiluminescence assay. This assay was used to detect anti brain antibodies in serum samples from humans with various neurological diseases. Such antibody activity was found in a high proportion of these patients. Subsequent experiments with purified IgG fractions and corresponding F(ab')2 fragments showed that the observed reactions were highly specific. It was concluded that the chemiluminescence assay is a sensitive and useful technique to detect autoantibodies in neurological diseases.

Animals↗
PubMed1993

Determination of the IgG index for the detection of intrathecal immunoglobulin synthesis in dogs using an ELISA.

The IgG index is a calculated quotient using IgG and albumin contents of cerebrospinal fluid (CSF) and serum to detect intrathecal IgG synthesis, which is important in the diagnosis of inflammatory infectious diseases of the central nervous system (CNS). An ELISA to measure IgG and albumin contents in blood and CSF was developed to determine the IgG index. Twenty-three normal dogs and 98 dogs with various neurological diseases were examined. In most dogs with infectious inflammatory diseases, with the exception of the acute form of nervous canine distemper, there was an elevation of the IgG index. Tumours of the CNS had an IgG index within the normal range. An elevation was found in lymphoid tumours or meningiomas with secondary cellular infiltration. Degenerative diseases, spinal cord compression and ischaemic myelopathy due to fibrocartilagenous embolism had normal or only slightly elevated IgG indices. In seven cases with inflammatory lesions there was no obvious CSF pleocytosis but the IgG index was elevated. In 17 cases in which infectious inflammatory disease was suspected, based on elevated CSF cell counts, inflammation could be excluded after determination of the IgG index. The reproducibility of the technique was found to be good and, considering the limited amount of time, expense and effort required, the determination of the IgG index in dogs is a useful extension of the conventional CSF examination.

Animals↗
PubMed1993

Saponin treatment for in situ hybridization maintains good morphological preservation.

The commonly used procedures for in situ hybridization require treatment of the tissue with non-ionic detergents and proteolytic enzymes, resulting in considerable loss of morphological detail. In this study proteinase pre-treatment of the tissue was replaced by saponin, a highly surface-active plant glycoside. This saponin treatment allowed good preservation of tissue morphology, as determined by differential interference and contrast enhanced video microscopy. Saponin pre-treatment resulted in an equal or even better hybridization sensitivity with probes recognizing viral (canine distemper virus) and cellular (myelin) nucleic acid sequences in tissue cultures as well as in paraffin sections. Probable mechanisms of how saponin allows probe penetration while maintaining the morphological details are discussed.

Animals↗