Characterization of two dog IgE-specific antibodies elicited by different recombinant fragments of the epsilon chain in hens

Two recombinant [His]6-tagged fragments of the canine immunoglobulin E (IgE) heavy chain (second domain: IgEf2 and third and fourth domains: IgEf3/4) were cloned, expressed in Escherichia coli (E. coli) as [His]6-tagged proteins, and affinity-purified over nickel-nitrilotriacetic acid columns. The recombinant proteins were used to immunize hens. The raised and affinity-purified chicken antibodies (Ab) isolated from egg yolk exhibited specific binding to the respective recombinant canine IgE fragment (IgEf) on immunoblots and displayed high titers against the IgEf in ELISA. Immunoblotting of canine serum separated by PAGE under native conditions with the IgEf2- and IgEf3/4-specific Ab resulted in staining of a protein of approximately 180 kilodaltons (kD). The IgEf3/4-specific Ab further recognized an 80 kD protein in IgEf3/4-specific Ab affinity-enriched dog serum separated under denaturing conditions. In an ELISA for the detection of antigen-specific IgE in dog serum, reduced binding of the IgEf-specific Ab was observed after heat treatment of the dog serum. The reactivity of both of the raised chicken Ab was only present in postimmune reagents and could only be inhibited by preincubation with the IgEf used for immunization and not with dog immunoglobulin G, E. coli extract, or with a nonrelevant recombinant [His]6-tagged protein. In immunohistochemistry, the IgEf3/4-specific Ab specifically recognized cells in paraffin-embedded tissue sections of lymph nodes. Furthermore, both of the IgEf-specific Ab elicited positive immediate type 1 skin reactions in dogs. Semiquantitative assessment of total serum IgE in dogs was developed using IgEf2-specific Ab as coating reagent and the biotinylated IgEf3/4-specific Ab as developing Ab in ELISA. In conclusion, both IgEf-specific Ab recognize native dog IgE with the advantages that they are directed against different and known constant domains of the IgE molecule, and that they can be used for immunohistochemistry on paraffin-embedded tissue. The two dog IgE-specific Ab could initiate clinical research on the involvement of immediate-type hypersensitivity reactions in dogs.

Generation and functional characterisation of canine bone marrow-derived macrophages

A culture of bone marrow cells from the femurs of canine pups at high concentrations of fetal calf serum under non-adherent conditions allowed the proliferation and differentiation of mononuclear phagocyte lineage cells, as evidenced by morphology and CD14 expression. Cells from other lineages progressively diminished in numbers. Cells collected between 12 and 19 days of culture expressed an array of macrophage activities including ingestion of opsonised erythrocytes, generation of superoxide, up-regulation of procoagulant activity and synthesis of tumour necrosis factor (TNF) upon appropriate stimulation. TNF production was enhanced when the cultures were simultaneously stimulated with canine recombinant, or supernatant-derived, interferon-gamma. In contrast, low levels of inducible nitric oxide (NO) synthase were expressed by only a minority of stimulated macrophages, and nitrite could not be detected in the medium. Therefore, canine macrophages generated by this novel culture system resemble human macrophages in their inefficient and restricted generation of NO upon appropriate stimulation.

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.

Spontaneous demyelinating myelopathy in aging laboratory mice

Spontaneous demyelination has been observed to occur sporadically in the thoracic spinal cord of aging laboratory mice used in routine long-term chemical safety studies. Positive immunohistochemical reaction for VP-1 (virus protein) indicated that the demyelination was associated with Theiler's murine encephalomyelitis virus infection. Although this rare spontaneous lesion has no bearing on the quality of chemical safety studies, its knowledge is essential for the appropriate interpretation of study results.

Hydrocephalus in mice infected with a Theiler's murine encephalomyelitis virus variant

The etiology of hydrocephalus is never established in the majority of clinical cases, while various agents, nutritional deficiencies, and genetic factors have been shown to play a role. Viral infection has been recognized as one of the causative factors in the development of hydrocephalus. The wild-type DA strain of Theiler's murine encephalomyelitis virus (TMEV), which belongs to the family Picornaviridae, causes a chronic demyelinating disease in mice with viral persistence that resembles multiple sclerosis. We found that a DA virus variant, hydrocephalus 101 virus (H101 virus), caused hydrocephalus in mice, a condition previously never described for TMEV. To clarify the relationship between DA virus infection and hydrocephalus, we compared H101 virus and wild-type DA virus infection in mice. Using immunohistochemistry and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL), we found that during the acute phase of infection, H101 virus caused macrocephaly and meningitis with the presence of apoptosis, while parenchymal involvement was not evident. In contrast, wild-type DA virus caused an acute polioencephalomyelitis with parenchymal infection and apoptosis. During the chronic phase, H101 virus infection caused communicating hydrocephalus without viral persistence. No demyelination and little or no anti-TMEV antibodies were observed in H101 virus-infected mice. Sequence analysis revealed that H101 virus had mutations in the 5'UTR and capsid protein coding region. Characterization of this new hydrocephalus model gives insight into the possible viral involvement in human hydrocephalus cases of obscure etiology.

Expression of cytokine mRNA in lentivirus-induced arthritis

Infection of goats with the lentivirus caprine arthritis encephalitis virus (CAEV) leads to persistent infection and development of chronic arthritis. We analyzed the expression of cytokines and viral RNA in the joints of goats at early time points after experimental infection with CAEV and in those of animals suffering from chronic arthritis as a result of natural infection. In situ hybridization experiments showed that the pattern of cytokine expression in caprine arthritis was similar to that found in rheumatoid arthritis (RA), with a few cells expressing the lymphocyte-derived cytokines interferon (IFN)-gamma and interleukin (IL)-2 and rather more cells expressing monocyte chemoattractant protein (MCP)-1, IL-6, and tumor necrosis factor (TNF)-alpha. IFN-gamma mRNA expression in experimentally infected joints peaked at day 12 and was mostly detected in areas containing viral RNA. At later time points, no IFN-gamma- or virus-expressing cells were found in inflamed joints but both were again detected in goats with severe arthritis. Interestingly, at the clinical stage of arthritis reflecting the chronic stage of infection, the inflammatory lesion was found to be immunologically compartmentalized. Humoral immune responses and cell-mediated immune responses appeared to concurrently occur in distinct areas of the synovial membrane.

In vivo and in vitro detection of canine distemper virus nucleoprotein gene with digoxigenin-labelled RNA, double-stranded DNA probes and oligonucleotides by in situ hybridization

A single-stranded RNA, two double-stranded (ds) DNA probes and 10 oligonucleotides labelled with digoxigenin were comparatively evaluated for their usefulness to detect canine distemper virus (CDV) nucleoprotein RNA in in vitro infected Vero cells and in tissues of dogs with spontaneous CDV infection by in situ hybridization (ISH). In addition, results were compared to CDV nucleoprotein antigen distribution as demonstrated by immunohistochemistry. The RNA probe was derived from the virulent A75/17 strain, the DNA and oligonucleotide probes from the avirulent Onderstepoort strain of CDV. The two DNA probes were 287 and 126 base pairs long. For ISH, various factors including fixatives, proteolytic digestion, probe concentration, hybridization conditions and detection systems were compared. All probes were suitable for demonstration of CDV RNA in in vitro infected cells, regardless of the CDV strain employed. In vivo CDV nucleic acid was detected by RNA and the dsDNA probes. However, the probes varied substantially with respect to sensitivity and specificity. The CDV RNA probe was far superior in sensitivity when compared to the DNA probes. Furthermore, the shorter DNA probe displayed a higher sensitivity, indicating that length of the probe is an important parameter when selecting probes. Oligonucleotides displayed only rarely a positive signal and caused frequently hybridization signals in the nucleus, which where considered not specific for CDV. Summarized, the present study reveals that RNA probes are currently the most sensitive tool for detection of CDV RNA in tissues.

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.

Abundant expression of viral nucleoprotein mRNA and restricted translation of the corresponding viral protein in inclusion body polioencephalitis of canine distemper

Brain and other tissues of three dogs aged 4-21 months with inclusion body polioencephalitis caused by canine distemper virus (CDV) were examined for CDV nucleoprotein (N) antigen and mRNA distribution. Two animals (nos 3 and 1) had suddenly shown central nervous system (CNS) signs 4 days and 5 months, respectively, after vaccination with a modified live CDV vaccine; animal no. 2 had shown similar signs 4 weeks after vaccination with an unknown product. Lesions in the CNS, which were restricted to the grey matter, occurred most frequently in the diencephalon, mesencephalon, medulla oblongata and, in one animal, in the cerebral cortex. Changes were characterized by mild to moderate perivascular lymphohistiocytic cuffs, loss of neurons, neuronal necrosis, glial nodules, and oedema. Intranuclear and cytoplasmic inclusion bodies, especially prominent in neurons, were observed. By in-situ hybridization, CDV N mRNA expression was confirmed with a non-radioactively labelled N-specific mRNA probe. The corresponding RNA translation product was detected immunohistochemically with a proteinspecific monoclonal antibody. Viral antigen and mRNA were observed in the same cell types and brain compartments. However, the number of cells expressing N mRNA exceeded the number of cells containing viral antigen greatly in two animals and slightly in one. Some areas with abundant viral mRNA expression were almost completely devoid of viral antigen. mRNA and the corresponding translation product were demonstrated in neurons and less frequently in astrocytes, but not in perivascular inflammatory cells. It would appear that distemper inclusion-body polioencephalitis may be due to a non-productive CDV infection of neurons, characterized by abundant expression of CDV N mRNA and reduced translation of the corresponding viral protein. These findings suggest that in distemper the pathogenesis of grey-matter lesions differs substantially from that of white-matter lesions, which constitute the most common manifestation of distemper encephalitis.

Distemper: not a new disease in lions and tigers

In light of recent canine distemper virus (CDV) epidemics, we set out to determine the historical significance of CDV infection in captive lions and tigers in Switzerland. The retrospective case material consisted of 42 lion and tiger necropsy cases from 1972 to 1992. Necropsy reports for all lions and tigers were reviewed. All existing paraffin tissues were immunohistochemically examined with a polyclonal antibody raised against CDV. The results for 19 of the 42 lions and tigers were classified as positive by immunohistochemistry; 23 results were negative or questionable. The results for four animals (three positive and one negative ) were further tested by in situ hybridization, and the results concurred with the immunohistochemistry findings. CDV infection of large cats is older and more widespread than previously thought. All large cats in captivity should be immunized even if canine distemper is not believed to be a problem for large cats in the area.

Oligodendroglial pathology in canine distemper

Canine distemper virus (CDV) causes a multifocal demyelinating disease in dogs. The mechanism of acute demyelination in distemper is still poorly understood. The initial demyelinating lesion in distemper is directly virus induced, since there is a clear correlation between the occurrence of demyelination and CDV replication in the cells of the white matter. Yet, there is little evidence for oligodendroglial infection. Changes of these cells have been reported in vitro and in vivo. The in vitro studies showed that--in contrast to other cells such as astrocytes and macrophages--oligodendrocytes hardly express CDV protein. However, we could show that these cells underwent a restricted infection with transcription of CDV RNA and that this phenomenon correlated with down-regulation of myelin gene transcription. The extension of these in vitro findings in vivo was obscured by the lack of reliable oligodendrocyte labelling techniques in canine brain tissue sections. In this study we combined immunohistochemistry with in situ hybridization to examine oligodendrocytes in demyelinating lesions and to investigate the question of oligodendrocyte infection in vivo. We could demonstrate that CDV infection leads to massive down-regulation of myelin gene expression in demyelinating lesions and that this effect correlates in part with a restricted infection of oligodendrocytes.

Expression of TNF alpha in arthritis caused by caprine arthritis encephalitis virus

Goats infected with caprine arthritis encephalitis virus (CAEV) develop chronic arthritis sharing many features with human rheumatoid arthritis (RA). TNF is thought to be a key mediator contributing to the formation of the arthritic lesion in RA. We studied this cytokine in goats suffering from chronic arthritis. TNF alpha expressing cells were detected by in situ hybridization in synovial membranes of arthritic carpal joints. Expression of TNF alpha did not correlate with the degree of viral replication as assessed by in situ hybridization for viral RNA. In line with the lack of correlation between the degree of viral replication and TNF expression in vivo, we failed to detect increased cytokine RNA in goat macrophages infected with CAE virus in vitro and no TNF protein was found in culture supernatants. In addition, virus infection failed to prime goat macrophages for enhanced TNF expression in response to lipopolysaccharide. Taken together, these findings argue against a direct role of CAE virus in increasing the expression of TNF alpha in caprine arthritis.

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.

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.

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.

Nucleotide and deduced amino acid sequences of the nucleocapsid protein of the virulent A75/17-CDV strain of canine distemper virus

Virus persistence is essential in the chronic inflammatory canine distemper virus (CDV)-induced demyelinating disease. In the case of CDV there is a close association between persistence and virulence. Virulent CDV isolated from dogs with distemper shows immediate persistence in primary dog brain cell cultures (DBCC) and in different cell lines. We have evidence that the nucleocapsid (NP) protein plays an important role in the development of persistence. The NP-protein, the most abundant structural virus protein, also influences virus assembly and has some regulatory functions in virus transcription and replication. In this study we compared the nucleotide and deduced amino acid sequence of a virulent CDV strain (A75/17-CDV) to a culture-attenuated non-virulent strain (OP-CDV). Viral RNA was extracted from DBCC infected with virulent CDV. Virulent CDV retains its in vivo properties, such as virulence and ability to cause demyelination, when propagated in these DBCC. The viral RNA was reverse transcribed and the resulting cDNA amplified by polymerase chain reaction for subsequent cloning. The nucleotide sequences of these clones were determined by the dideoxy chain termination method. The number of nucleotides and the putative NP-protein of the virulent strain matched the attenuated CDV strain. We observed a total of 105 nucleotide differences. Three were localised within the 3' and five within the 5' non-coding region of the NP-gene. The 97 nucleotide changes within the coding region resulted in 22 amino acid differences. 10 of these amino acid (AA) modifications were within the N-terminal region (AA 1 to 159) and 12 within the C-terminal area (AA 351 to 523).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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.

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.

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.

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)

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.

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.

Distribution of glycosylphosphatidylinositol-specific phospholipase D mRNA in bovine tissue sections

It has been reported that mammalian serum, and to a lower extent mammalian liver, brain, pancreas, udder, and milk, contain glycosylphosphatidylinositol-specific phospholipase D activity. However, the sites of synthesis have not been determined. In order to study in which cell(s) of the organism synthesis of glycosylphosphatidylinositol-specific phospholipase D takes place, we undertook a systematic screening of 12 different bovine tissues. In situ hybridization experiments with a specific anti-sense RNA probe, derived from a bovine liver cDNA, revealed that glycosylphosphatidylinositol-specific phospholipase D mRNA is present in mast cells of the adrenal gland, lung, and liver. On the other hand, our specific probe detected no mRNA in bovine pancreas, brain, and udder, although enzyme activity has been reported in these tissues. Northern blot analysis of total bovine liver RNA demonstrated two distinct glycosylphosphatidylinositol-specific phospholipase D mRNAs of approximately 3.3 kb and 4 kb length suggesting that two forms of the enzyme may exist.