Primary Postnatal Dorsal Root Ganglion Culture from Conventionally Slaughtered Calves

Neurological disorders in ruminants have an important impact on veterinary health, but very few host-specific in vitro models have been established to study diseases affecting the nervous system. Here we describe a primary neuronal dorsal root ganglia (DRG) culture derived from calves after being conventionally slaughtered for food consumption. The study focuses on the in vitro characterization of bovine DRG cell populations by immunofluorescence analysis. The effects of various growth factors on neuron viability, neurite outgrowth and arborisation were evaluated by morphological analysis. Bovine DRG neurons are able to survive for more than 4 weeks in culture. GF supplementation is not required for neuronal survival and neurite outgrowth. However, exogenously added growth factors promote neurite outgrowth. DRG cultures from regularly slaughtered calves represent a promising and sustainable host specific model for the investigation of pain and neurological diseases in bovines.

Überwachung von TSE bei kleinen Wiederkäuern und Schweinen: Eine Pilotstudie

Switzerland is controlling Transmissible Spongiform Encephalopathies (TSE) in cattle (BSE) and small ruminants (scrapie). Since BSE is potentially transmissible to sheep, goats or pigs through feeding of contaminated meat and bone meal, implementation of an active surveillance programme for TSE in these species is discussed. The aim of this pilot study was to obtain preliminary data on the prevalence ofTSE and other neurological disorders in these populations. For that purpose, a total of 398 perished and 825 slaughtered adult small ruminants and pigs was examined for the presence of neuropathological changes. None of these animals revealed positive for TSE. However, the investigations demonstrated that perished sheep and goats exhibited a higher prevalence of relevant neuropathological changes when compared with slaughtered animals. From these results, it is concluded that perished small ruminants are probably a risk population for TSE and should be considered as target populations for an active surveillance programme.

Scrapie-Überwachung in der Schweiz. I. Klinische Aspekte von neurologischen Erkrankungen bei Schaf und Ziege

Small ruminants infected with scrapie show a large range of often unspecific clinical symptoms. The most-often described signs, locomotion, sensibility and behavioural disorders and emaciation, rarely occur together, and cases have been described in which only one of those signs was detectable.Thus, formulating a well-circumscribed definition of a clinical suspect case is difficult. Most animals with CNS-effecting diseases such as listeriosis, polioencephalomacia, cerebrospinal nematidiasis and enterotoxemia will, in a thorough neurological examination, show at least some scrapie-like symptoms. Among the 22 neurological field cases examined in this study, a goat with cerebral gliomatosis and hair lice showed the closest similarity to clinical scrapie. The unilateral deficiency of the cerebral nerves has potential as an clinical exclusion criterion for scrapie. However, the laboratory confirmation--or exclusion--of scrapie remains important. It thus needs to be realized that a consistent and thorough examination of neurologically diseased small ruminants (including fallen stock) is the backbone of a good surveillance system for these diseases. This should be a motivation for submitting adult sheep and goats for neuropathological examination.

Scrapie-Überwachung in der Schweiz. II. Epidemiologische Aspekte der Erfassung von neurologischen Erkrankungen bei Schaf und Ziege

Monitoring of transmissible spongiform encephalopathy (TSE) in Swiss sheep and goats is based on the examination of animals from different sources. In this study, frequencies and proportions of the different diagnoses were compared between routinely submitted sheep and goats, notified scrapie suspects as well as fallen stock. Meningitis/ encephalitis cases were significantly more frequent (OR = 2.2) in the scrapie suspect group when compared to the routine submissions. Metabolic-toxic encephalopathy was seen more frequently within the fallen stock. Rare neurological diagnoses were more frequent among scrapie suspects and routine submissions when compared to fallen stock. Listeriosis was diagnosed equally frequent among the scrapie suspects and routine submissions but less frequent in fallen stock. Scrapie prevalence among the fallen stock and the routine submissions was 0 (zero), with 95% certainty that prevalence is < 1%. The examined animals are representative for most of the Swiss regions with considerable sheep and goat production. Continuation of the detailed neuropathological examination of small ruminants from these three groups, substituted by actively testing a sufficiently large sample of fallen stock and possibly also healthy-slaughtered adult sheep and goats for transmissible spongiform encephalopathies would ensure a good surveillance within the small ruminant population.

The distribution of E-cadherin expression in listeric rhombencephalitis of ruminants indicates its involvement in Listeria monocytogenes neuroinvasion

AIM

To investigate the expression of E-cadherin, a major host cell receptor for Listeria monocytogenes (LM) internalin A, in the ruminant nervous system and its putative role in brainstem invasion and intracerebral spread of LM in the natural disease.

METHODS

Immunohistochemistry and double immunofluorescence was performed on brains, cranial nerves and ganglia of ruminants with and without natural LM rhombencephalitis using antibodies against E-cadherin, protein gene product 9.5, myelin-associated glycoprotein and LM.

RESULTS

In the ruminant brain, E-cadherin is expressed in choroid plexus epithelium, meningothelium and restricted neuropil areas of the medulla, but not in the endothelium. In cranial nerves and ganglia, E-cadherin is expressed in satellite cells and myelinating Schwann cells. Expression does not differ between ruminants with or without listeriosis and does not overlap with the presence of microabscesses in the medulla. LM is observed in phagocytes, axons, Schwann cells, satellite cells and ganglionic neurones.

CONCLUSION

Our results support the view that the specific ligand-receptor interaction between LM and host E-cadherin is involved in the neuropathogenesis of ruminant listeriosis. They suggest that oral epithelium and Schwann cells expressing E-cadherin provide a port of entry for free bacteria offering a site of primary intracellular replication, from where the bacterium may invade the axonal compartment by cell-to-cell spread. As E-cadherin expression in the ruminant central nervous system is weak, only very locally restricted and not related to the presence of microabscesses, it is likely that further intracerebral spread is independent of E-cadherin and relies primarily on axonal spread.

Molecular analysis of carbohydrate N-acetylgalactosamine 4-O sulfotransferase 8 (CHST8) as a candidate gene for bovine spongiform encephalopathy susceptibility

Endogenous prion proteins (PrP) play the central role in the pathogenesis of transmissible spongiform encephalopathies. The carbohydrate N-acetylgalactosamine 4-O sulfotransferase 8 (CHST8) promotes the conversion of the cellular PrP(C) into the pathogenic PrP(d). Six sequence variants within the CHST8 gene were identified by comparative sequencing and genotyped for a sample of 623 animals comprising bovine spongiform encephalopathy (BSE)-affected and healthy control cows representing German Fleckvieh (German Simmental), German Holstein (Holstein-Friesian) and Brown Swiss. Significant differences in the allele, genotype and haplotype frequencies between BSE-affected and healthy cows indicate an association of sequence variant g.37254017G>T with the development of the disease in Brown Swiss cattle.

Evaluation of an in vitro sulphidoleukotriene release test for diagnosis of insect bite hypersensitivity in horses

REASONS FOR PERFORMING STUDY

Insect bite hypersensitivity (IBH) is an IgE-mediated allergic dermatitis caused by bites of Culicoides and Simulium species, and improved means of diagnosis are required.

OBJECTIVES

The cellular antigen simulation test (CAST) with C. nubeculosus and S. vittatum extracts was assessed in a population of IBH-affected and healthy horses. Variations in test results over a one year period and possible cross-reactivity between different insect extracts was studied.

METHODS

A total of 314 mature horses were studied using the CAST. Influence of severity of clinical signs, gender and age were evaluated, and 32 horses were tested repeatedly over one year. The kappa reliability test was used to assess agreement of the test results with different insect extracts.

RESULTS

Horses with IBH had significantly higher sLT release than controls with C. nubeculosus and S. vittatum. The highest diagnostic sensitivity and specificity levels were attained when using adult C. nubeculosus extracts with the CAST (78% and 97%, respectively), suggesting that most horses with IBH are sensitised against Culicoides allergens. A proportion of IBH-affected horses was found to be sensitised to allergens of Simulium spp. in addition to those of C. nubeculosus. The CAST with C. nubeculosus had positive and negative predictive values > or = 80% for a true prevalence of IBH of 12-52%. In the follow-up study, the proportion of IBH-affected horses with a positive test result ranged from 90% in November to 68% in March. Severity of clinical signs or age did not influence test results significantly. However, IBH-affected males achieved significantly more positive test results than IBH-affected females.

CONCLUSIONS

The CAST with adult C. nubeculosus has high specificity and good sensitivity for diagnosis of IBH. Horses with IBH are mainly sensitised to Culicoides allergens, and some horses are additionally also sensitised to allergens in Simulium spp.

POTENTIAL RELEVANCE

The CAST is likely to be a useful test for diagnosis of IBH, even allowing the identification of IBH-affected but asymptomatic horses. This test may also help in further characterisation of allergens involved in this condition.

Immunohistochemical demonstration of the putative canine distemper virus receptor CD150 in dogs with and without distemper

Signaling lymphocyte activation molecule (SLAM) or CD150 can function as a receptor for the canine distemper virus (CDV) in vitro. The expression of SLAM was studied using immunohistochemistry in order to evaluate the presence and distribution of the receptor in dogs in vivo. Additionally, receptor expression was assessed after experimental infection of dogs with CDV. In 7 control dogs without distemper virus, the receptor was found in various tissues, mostly on cells morphologically identified as lymphocytes and macrophages. In 7 dogs with early distemper lesions characterized by presence of the virus, higher numbers of SLAM-expressing cells were found in multiple tissues recognized as targets of CDV compared with those in control dogs. These findings suggest that SLAM, a putative distemper receptor, is expressed in dogs in vivo. Additionally, virus infection is associated with up-regulation of SLAM, potentially causing an amplification of virus in the host.

Differential expression of CD45 on canine microglial cells

CD45, also called leucocyte common antigen is a transmembrane protein tyrosine phosphatase on the surface of nearly all white blood cells and has a functional role in signal transduction. In the brain, the expression of CD45 can be used to distinguish microglial cells with a characteristic phenotype of CD11b/c+ and CD45(low) from other central nervous system (CNS) macrophages which show an expression of CD11b/c+ and CD45(high). In the course of pathological changes in the CNS, microglia in rodents is known to readily upregulate expression of various surface molecules, such as CD45. Understanding the mechanisms that regulate expression of surface molecules is essential to study the pathogenesis of CNS diseases. In the present study, the expression of CD45 on microglia of 42 dogs was examined ex vivo by means of flow cytometry. The dogs were classified in two groups according to the histopathological diagnosis in the CNS. All dogs without changes in the CNS (group I; n = 22) only showed low percentages of CD45+ microglial cells. In group II consisting of 20 dogs with different intracranial diseases varying results were obtained. Thirteen dogs showed a low percentage of CD45+ microglial cells whereas seven dogs exhibited high percentages of microglial cells expressing CD45. Evaluation of expression intensity in these seven dogs revealed two subpopulations of CD45+ microglial cells: a large subpopulation with CD45(low) and a small subpopulation with CD45(high). The expression intensity of CD45(high) was comparable with that of canine monocytes. It was attempted to correlate these findings to age of the animals, underlying disease, duration of clinical signs, medical treatment, occurrence of seizure activity and the expression of other surface molecules. It appeared that dogs with high percentages of CD45+ suffered from long-lasting CNS disease with seizures. In future studies, the reason and consequences for upregulated CD45 in long-lasting CNS diseases has to be further evaluated.

Equine insect bite hypersensitivity: immunoblot analysis of IgE and IgG subclass responses to Culicoides nubeculosus salivary gland extract

Insect bite hypersensitivity (IBH) is an allergic dermatitis of horses caused by IgE-mediated reactions to bites of Culicoides and sometimes Simulium spp. The allergens causing IBH are probably salivary gland proteins from these insects, but they have not yet been identified. The aim of our study was to identify the number and molecular weight of salivary gland extract (SGE) proteins derived from Culicoides nubeculosus which are able to bind IgE antibodies (ab) from the sera of IBH-affected horses. Additionally, we sought to investigate the IgG subclass (IgGa, IgGb and IgGT) reactivity to these proteins. Individual IgE and IgG subclass responses to proteins of C. nubeculosus SGE were evaluated by immunoblot in 42 IBH-affected and 26 healthy horses belonging to different groups (Icelandic horses born in Iceland, Icelandic horses and horses from different breeds born in mainland Europe). Additionally, the specific antibody response was studied before exposure to bites of Culicoides spp. and over a period of 3 years in a cohort of 10 Icelandic horses born in Iceland and imported to Switzerland. Ten IgE-binding protein bands with approximate molecular weights of 75, 66, 52, 48, 47, 32, 22/21, 19, 15, 13/12 kDa were found in the SGE. Five of these bands bound IgE from 50% or more of the horse sera. Thirty-nine of the 42 IBH-affected horses but only 2 of the 26 healthy horses showed IgE-binding to the SGE (p<0.000001). Similarly, more IBH-affected than healthy horses had IgGa ab binding to the Culicoides SGE (19/22 and 9/22, respectively, p<0.01). Sera of IBH-affected horses contained IgE, IgGa and IgGT but not IgGb ab against significantly more protein bands than the sera of the healthy horses. The cohort of 10 Icelandic horses confirmed these results and showed that Culicoides SGE specific IgE correlates with onset of IBH. IBH-affected horses that were born in Iceland had IgGa and IgGT ab (p< or =0.01) as well as IgE ab (p=0.06) against a significantly higher number of SGE proteins than IBH-affected horses born in mainland Europe. The present study shows that Culicoides SGE contains at least 10 potential allergens for IBH and that IBH-affected horses show a large variety of IgE-binding patterns in immunoblots. These findings are important for the future development of a specific immunotherapy with recombinant salivary gland allergens.

Canine distemper virus associated proliferation of canine footpad keratinocytes in vitro

Infection of canine footpads with canine distemper virus (CDV) can result in so-called hard pad disease characterized by footpad epidermal proliferation and hyperkeratosis. Cultured canine footpad keratinocytes (CFK) were inoculated with a virulent canine distemper virus strain (A75/17-CDV) to study the effects of CDV-infection on keratinocyte proliferation. Infection was analyzed by immunohistochemistry and in situ hybridization for CDV nucleoprotein (N-protein) antigen and mRNA. CDV caused a persistent, non-cytocidal infection with spread from single cells to infection of the confluent cell layer 7 days post infection (p.i.). Absolute cell numbers were significantly higher in infected cultures compared to control cultures from day 4 until day 6 p.i. Infected cultures contained significantly more total DNA on day 5 p.i. compared to controls. Immunohistochemical investigation of proliferation markers Ki67 and BrdU demonstrated a nearly two-fold increase in numbers of positive cells on day 5 p.i. compared to controls. These findings demonstrate that canine distemper virus infection of canine footpad keratinocytes in vitro was associated with proliferation.

Cytokine profiles of peripheral blood and airway CD4 and CD8 T lymphocytes in horses with recurrent airway obstruction

Equine recurrent airway obstruction (RAO) is thought to result from an aberrant immune response to inhaled antigens, modulated by T lymphocytes via the secretion of pro-inflammatory cytokines. However data relating to the phenotypes of the T lymphocytes present in peripheral blood and bronchoalveolar lavage fluid of RAO horses and their cytokine profiles are contradictory. The aim of this study was to further investigate the cytokine (IL-4, IL-5, IL-13 and INF-gamma) mRNA expression profile in peripheral blood lymphocytes and bronchoalveolar lavage lymphocytes from RAO and control horses, before and at 48 h after horses were exposed to hay/straw. In contrast to previous studies, cytokine expression was quantified in populations of CD4 and CD8 T lymphocytes which were purified using magnetic bead antibody cell separation. Hay/straw exposure induced clinical airway obstruction, airway neutrophilia and airway lymphocytosis in RAO horses, and, induced a mild, but significant, airway neutrophilia in controls. However, hay/straw exposure had no significant effect on peripheral blood lymphocyte or bronchoalveolar lavage lymphocyte cytokine expression in either group. In conclusion, RAO was not associated with alterations in lymphocyte cytokine expression that are consistent with Th1 or Th2 responses, but rather with a general down-regulation in expression of the measured cytokines in peripheral blood lymphocytes and bronchoalveolar lavage lymphocytes.

An mRNA region of the canine distemper virus fusion protein gene lacking AUG codons can promote protein expression

Canine distemper virus (CDV) produces a glycosylated type I fusion protein (F) with an internal hydrophobic signal sequence beginning around 115 residues downstream of the first AUG used for translation initiation. Cleavage of the signal sequence yields the F0 molecule, which is cleaved into the F1 and F2 subunits. Surprisingly, when all in-frame AUGs located in the first third of the F gene were mutated a protein of the same molecular size as the F0 molecule was still expressed from both the Onderstepoort (OP) and A75/17-CDV F genes. We designated this protein, which is initiated from a non-AUG codon protein Fx. Site-directed mutagenesis allowed to identify codon 85, a GCC codon coding for alanine, as the most likely position from which translation initiation of Fx occurs in OP-CDV. Deletion analysis demonstrated that at least 60 nucleotides upstream of the GCC codon are required for efficient Fx translation. This sequence is GC-rich, suggesting extensive folding. Secondary structure may therefore be important for translation initiation at codon 85.

Reduced Nuclear Translocation of Nuclear Factor (NF)-κB p65 in the Footpad Epidermis of Dogs Infected with Distemper Virus

Infection of canine footpads with the canine distemper virus (CDV) can cause massive epidermal thickening (hard pad disease), as a consequence of increased proliferation of keratinocytes and hyperkeratosis. Keratinocytes of canine footpad epidermis containing detectable CDV nucleoprotein antigen and CDV mRNA were shown previously to have increased proliferation indices. Because various proteins that play a role in the proliferation of epidermal cells are viral targets, the potential participation of such proteins in CDV-associated keratinocyte proliferation was investigated. Transforming growth factor-alpha (TGF-alpha), cell cycle regulatory proteins p21, p27 and p53, and nuclear factor (NF)-kappaB transcription factor components p50 and p65 were studied in the footpad epidermis from the following groups of dogs inoculated with CDV: group 1, consisting of seven dogs with clinical distemper and CDV in the footpad epidermis; group 2, consisting of four dogs with clinical distemper but no CDV in the footpad epidermis; group 3, consisting of eight dogs with neither clinical distemper nor CDV in the footpad epithelium. Group 4 consisted of two uninoculated control dogs. The expression of TGF-alpha, p21, p27 and p53, and p50 in the basal layer, lower and upper spinous layers, and in the granular layer did not differ statistically between CDV-positive (group 1) and CDV-negative (groups 2-4) footpad epidermis. However, there were differences in the levels of nuclear and cytoplasmic p65 expression between group 1 dogs and the other three groups. Thus, footpads from group 1 dogs had more keratinocytes containing p65 in the cytoplasm and, conversely, fewer nuclei that were positive for p65. These findings indicate that p65 translocation into the nucleus is reduced in CDV-infected footpad epidermis. Such decreased translocation of p65 may help to explain increased keratinocyte proliferation in hard pad disease and suggests interference of CDV with the NF-kappaB pathway.

Rabies in Red Foxes (Vulpes vulpes) Experimentally Infected with European Bat Lyssavirus Type 1

The susceptibility of red foxes (Vulpes vulpes) to European bat lyssavirus type 1 (EBLV-1) infection was examined. Eight foxes were inoculated intramuscularly (i.m.) with 10(4.9) foci-forming units (FFU) (n = 4) and 10(5.1) FFU (n = 4) and observed for up to 90 days. All foxes showed manifestations of a neurologic disorder (e.g. seizures, myoclonus, agitation), starting as early as 5 days post-infection (p.i.). Subsequently, all animals showed improvement followed by one or more relapses. One fox was killed 3 days after it recovered, 26 days post-infection. Two other foxes were also killed 38 and 54 days post-infection after severe neurologic signs returned. All foxes developed a humoral immune response against EBLV-1 as determined in serum and brain tissues. However, no rabies virus antigen was detected in the brain, other tissues and secretions examined (e.g. salivary gland, saliva, tonsils, lungs) by using different standard diagnostic techniques [fluorescent antibody test, reverse transcription polymerase chain reaction (RT-PCR), rabies tissue culture inoculation test], with the exception of one fox in which EBLV-1 RNA was detected by RT-PCR in only the spinal cord. Brain tissues showed moderate to severe multifocal, mononuclear encephalomyelitis in the three foxes that were killed during the observation period, although no EBLV-1 virus was detectable in these tissues.

Canine distemper virus infection: proliferation of canine footpad keratinocytes

The proliferation of footpad keratinocytes of canine distemper virus (CDV)-infected dogs was investigated. Footpads of 19 dogs inoculated experimentally with a virulent distemper strain (A75/17) and of two noninoculated control dogs were collected at necropsy. Dogs were divided into four groups according to results of the postmortem examination: dogs with severe distemper (group 1), dogs with mild distemper (group 2), inoculated dogs without distemper (group 3) and noninoculated dogs (group 4). There was no distinct difference of epidermal thickness among the four groups. Infection of the footpad epidermis with CDV was demonstrated using immunohistochemistry for viral nucleoprotein and in situ hybridization for nucleoprotein messenger ribonucleic acid (mRNA). Only group 1 dogs had viral antigen and mRNA in the footpad epidermis with the same distribution. Footpad epidermis of group 1 dogs had more mitotic figures in the basal layer, and significantly more basal keratinocytes were positive for the proliferation markers Ki-67 and proliferating cell nuclear antigen. Double-staining for Ki-67 and viral nucleoprotein identified rare double-labeled basal keratinocytes. These findings suggest that the presence of CDV particles in the footpad epidermis is associated with keratinocyte proliferation.

Geographical clustering of cases of bovine spongiform encephalopathy (BSE) born in Switzerland after the feed ban

Over one-third of the cases of BSE in Switzerland have been born after the feed ban of December 1, 1990. Evidence for the geographical clustering of these cases emerged in two distinct regions. All the 354 BSE cases recorded until June 30, 2000 (set A), and the 376 cases recorded up to May 14, 2001 (set B), were georeferenced to the centres of the communities in which the herds of origin were located, and control populations were georeferenced to the centres of the communities in which these herds were located at the time of the census. The latitudes and longitudes of these centres were used in the statistical analysis of the spatial clustering. The Cuzick-Edwards test and the spatial scan statistics were applied to assess the significance of the clusters, while controlling for the spatial distribution of the underlying cattle population. There was global clustering of the cases born after the ban, and distinct and significant (P<0.05) spatial clusters were repeatedly identified in the two case datasets, and in several control populations (all cases born before the feed ban on a random sample of control farms) in terms of cattle density by region or cow density by region. Differential reporting was excluded as the underlying reason for the observed clusters.

Demyelination precedes oligodendrocyte loss in canine distemper virus-induced encephalitis

Canine distemper virus (CDV), a negative-stranded RNA morbillivirus, causes a persistent infection within the central nervous system resulting in a progressive, multifocal demyelinating disease. Demyelination is thought to be caused by a selective alteration of the myelin-producing oligodendrocytes. Metabolic impairment and morphological changes of the oligodendrocytes after CDV infection have previously been observed in vitro as well as in vivo. Until now it has been suggested that the oligodendrocytes completely disappear from CDV-induced demyelinating lesions. However, ultrastructural analysis in brain tissue sections and immunohistochemical examination of oligodendrocytes in dog brain cell cultures contradicted these observations. In this study oligodendrocytes from different categories of CDV-induced lesions were examined by in situ hybridization for proteolipid protein mRNA and--as a new tool employed on canine brain tissue sections--by immunohistochemistry using a monoclonal antibody against 2',3'-cyclic nucleotide 3'-phosphodiesterase, a myelin-specific enzyme. A down-regulation in the myelin gene transcription was detected already before demyelination occurred. However, a decrease in the number of oligodendrocytes was not observed until demyelination became evident. Although there was further depletion of oligodendrocytes in plaques with progressive demyelination, we demonstrated for the first time that these cells were still present in a significant amount even in chronic, completely demyelinated distemper lesions.

Partial protection and intrathecal invasion of CD8(+) T cells in acute canine distemper virus infection

Initial non-inflammatory demyelination in canine distemper virus infection (CDV) develops against a background of severe immunosuppression and is therefore, thought to be virus-induced. However, recently we found a marked invasion of T cells throughout the central nervous system (CNS) in dogs with acute distemper despite drastic damage to the immune system. In the present study, this apparent paradox was further investigated by immunophenotyping of lymphocytes, following experimental CDV challenge in vaccinated and non-vaccinated dogs. In contrast to CDV infected, unprotected dogs, vaccinated dogs did not become immunosuppressed and exhibited a strong antiviral immune response following challenge with virulent CDV. In unprotected dogs rapid and drastic lymphopenia was initially due to depletion of T cells. In peripheral blood, CD4(+) T cells were more sensitive and depleted earlier and for a longer time than CD8(+) cells which recovered soon. In the cerebrospinal fluid (CSF) we could observe an increase in the T cell to B cell and CD8(+) to CD4(+) ratios. Thus, partial protection of the CD8(+) cell population could explain why part of the immune function in acute distemper is preserved. As found earlier, T cells invaded the CNS parenchyma in these dogs but also in the protected challenged dogs, which did not develop any CNS disease at all. Since markers of T cell activation were upregulated in both groups of animals, this phenomenon could in part be related to non-specific penetration of activated T cells through the blood brain barrier. However, in diseased animals much larger numbers of T cells were found in the CNS than in the protected dogs, suggesting that massive invasion of T cells in the brain requires CDV expression in the CNS.

Immunoglobulin-E-bearing cells in skin biopsies of horses with insect bite hypersensitivity

The aim of the present study was to investigate, with immunohistochemistry and in situ hybridisation, if immunoglobulin-E (IgE) and mast cells are involved in the pathogenesis of insect bite hypersensitivity (IBH), an allergic dermatitis of horses. In tissue sections fixed in paraformaldehyde (PFA) for <24 h, significantly more IgE protein-bearing cells were found in the dermis and epidermis of acute and chronic IBH lesions than in skin biopsies from healthy horses (medians = 466, 236 and 110 cells/mm2, respectively; P < or = 0.01). More IgE-mRNA positive (+) cells were observed in the dermis of acute IBH lesions than in the dermis of healthy skin (median = 2.8 vs. 0.0 cells/mm2; P < or = 0.01). Significantly, more mast cells were detected with metachromatic (median = 160 vs. 62 cells/mm2; P < or = 0.001) and tryptase-specific stainings (median = 120 vs. 69 cells/mm2; P < or = 0.001) in the dermis of acute IBH biopsies compared to healthy skin. No chymase+ mast cells were found in any skin biopsy. IBH lesions fixed in PFA for >24 h were compared to dermatomycosis (DM) lesions; IBH biopsies contained a similar number of IgE-protein+ cells to DM biopsies (median = 249 vs. 192 cells/mm2; P = 0.08) but had significantly more IgE-mRNA+, metachromatic and tryptase+ mast cells than DM biopsies. This study suggests an involvement of IgE-mediated immune reactions in the pathogenesis of IBH as well as, sometimes, in dermatomycosis. Using double labelling, cells which expressed IgE protein and contained mast cell enzymes were detected.

[Occurrence of scrapie in Switzerland: an anonymous cross-sectional study]

Scrapie is a transmissible spongiform encephalopathy of sheep and goats, which leads to neurological signs and ends with the death of the infected animal. In Switzerland only a few cases were reported since 1982. In 1999, a questionnaire survey was conducted to increase information about neurological diseases in sheep and goat breeding farms. The aim was to estimate the frequency of neurological disorders including Scrapie and to increase the disease awareness of sheep and goat breeders. The main goal of the study was to increase the reporting of suspect cases of Scrapie and its differential diagnoses. Out of a database of all registered farms with at least five breeding sheep or breeding goats a random sample of 4711 was drawn to which anonymous questionnaires were sent. The return rate was 36%. In a parallel study, 150 voluntarily participants were interviewed using the same questionnaire. The results of both parts of the survey coincided. For the years 1997 and 1998, on average 1.0% of the breeding sheep and breeding goats showed neurological signs. 7.7% of the breeders indicated to have observed animals with neurological symptoms in their flock. At the population level, a total of 1954-2336 animals with neurological signs are observed in 691-929 flocks. The minority is reported to the veterinary authorities.

Alpha1c- and beta2-adrenergic receptor mRNA distribution in the bovine mammary gland detected by competitive RT-PCR

Milk ejection and milk removal is considerably influenced by the sympathetic nervous system. Stimulation of α-adrenergic receptors by administration of α-adrenergic agonists inhibits alveolar milk ejection and milk removal in dairy cows due to smooth muscle contraction (Blum et al. 1989; Bruckmaier et al. 1991). However, contraction of the teat in response to α-adrenergic receptor stimulation has no influence on milk flow as long as milk is available in the cistern (Bruckmaier et al. 1997). Therefore, α-adrenergic stimulation causes inhibition of transport of alveolar milk into the cistern. On the contrary, the stimulation of β-adrenergic receptors facilitates milk ejection and milk removal in dairy cows (Bernabé & Peeters, 1980; Bruckmaier et al. 1991) because of muscle relaxation. Therefore, the distribution of α- and β-adrenergic receptors plays an important role in the milkability of dairy cows. However, from these in vivo studies it is not possible to distinguish between the different α1- and α2- and β2-receptor subtypes owing to the non-specific nature of the pharmacological agents used.

To date, the precise tissue distribution of these different subtypes, in bovine mammary tissue, is unknown. Using molecular techniques, we were interested in the expression of genes that encode α1c and β2 as a preliminary study towards the understanding of noradrenergic receptor-gene expression and regulation in this important system.

In addition, α1c- and β2-adrenergic receptors were determined in front and rear quarters of the mammary gland to investigate differences in receptor distribution within the udder and possible relations between adrenergic receptor distribution and the higher milk flow rates in rear than in front quarters (Rothenanger et al. 1995).

GM1-gangliosidosis in Alaskan huskies: clinical and pathologic findings

Three Alaskan Huskies, two females and one male, were diagnosed with GM1-gangliosidosis. Clinically, diseased animals exhibited proportional dwarfism and developed progressive neurologic impairment with signs of cerebellar dysfunction at the age of 5-7 months. Skeletal lesions characterized by retarded enchondral ossification of vertebral epiphyses were revealed by radiographs of the male dog at 5.5 months of age. Histologic examination of the central nervous system (CNS) revealed that most neurons were enlarged with a foamy to granular cytoplasm due to tightly packed vacuoles that displaced the Nissl substance. Vacuoles in paraffin-embedded sections stained positively with Luxol fast blue and Grocott's method, and in frozen sections vacuoles were periodic acid-Schiff positive. Foamy vacuolation also occurred within neurons of the autonomic ganglia. Extracerebral cells such as macrophages and peripheral lymphocytes also displayed foamy cytoplasm and vacuolation. In the CNS of diseased animals, a mild demyelination and axonal degeneration was accompanied by a significant astrogliosis (P < 0.05) in the gray matter as compared with age- and sex-matched control dogs. There was also a significant loss (P < 0.05) of oligodendrocytes in the gray and white matter of affected animals as compared with controls. Ultrastructurally, the neuronal storage material consisted of numerous circular to concentric whorls of lamellated membranes or stacks of membranes in parallel arrays. GM1-gangliosidosis in Alaskan Huskies resembles beta-galactosidase deficiency in other canine breeds, and these CNS disorders may be a consequence of neuronal storage and disturbed myelin processing.

Targeted screening of high-risk cattle populations for BSE to augment mandatory reporting of clinical suspects

In Switzerland, the first case of bovine spongiform encephalopathy (BSE) was diagnosed in November 1990. Case numbers peaked in 1995, with a total of 352 BSE cases identified by 30 April 2000. Reporting of clinically suspect cattle is currently the most commonly used method world-wide to detect BSE cases. The effectiveness of mandatory reporting depends on a variety of factors; for other diseases passive surveillance underestimates the incidence of clinical cases. The efficiency of passive surveillance systems for BSE will remain unknown until screening tests able to identify clinically affected cattle have been applied in several countries. This paper provides the first detailed description of a targeted screening programme for BSE. Two populations of cows >24 months of age were included in the targeted screening: (i) cows found dead or culled on site where the carcass was submitted to rendering (fallen stock) and (ii) cows with health-related problems unfit for routine slaughter that were slaughtered under emergency procedures (emergency slaughter). Between 1992 and 1999, on average 81 clinical BSE suspects per year were reported to the veterinary authorities (passive surveillance), of which 43% were confirmed with BSE. A total of 30 clinical cases were captured by passive surveillance and an additional 20 BSE cases detected by targeted screening between May 1999 and April 2000. The odds of finding a BSE case was 49 times higher in the fallen stock and 58 times higher in emergency-slaughtered cattle when compared to passive surveillance. The targeted screening of fallen stock and emergency-slaughtered cattle considerably increased the number of detected cases in this 12-month period. Targeted-screening cases were on average 4 months younger than the clinical suspect cases. In conclusion, post-mortem testing of fallen stock and emergency-slaughtered cows >24 months for BSE is an important active surveillance element within a total surveillance system that principally is based on mandatory reporting of clinical suspect cases. Without ante-mortem screening tests to detect BSE-infected cattle during the incubation period, a combination of effectively functioning passive and active BSE surveillance strategies might be the only approach to assess the BSE situation reliably in a given country or region - and it is necessary to substantiate claims of freedom from the disease.

High constitutional nitrate status in young cattle

Nitrate or nitrite can be ingested or endogenously produced from nitric oxide. They can cause intoxication and are of general concern for health because they relate to various diseases. Our goal was to study ontogenetic and nutritional effects on the nitrate+nitrite (NOx-) status in cattle, particularly calves. NOx- concentration in blood plasma, cerebrospinal fluid, saliva, and urine was measured based on nitrate conversion by added nitrate reductase to nitrite, which was then determined by the Griess reaction. Concentrations of nitrate were the result of the difference between NOx- and nitrite values. Nitrate in blood plasma, saliva and urine was > or =97% and in cerebrospinal fluid of calves was approximately 35% of NOx-. Preprandial plasma NOx- in calves born after shortened or normal lengths of pregnancy (277 and 290 days) was 470 and 830 micromol/l, respectively, decreased within 4-7 days to 40-60 micromol/l, remained in this range up to 4 months, was < or =5 micromol/l in heifers and no longer measurable in 3-8-year-old cows. Cerebrospinal NOx- in 8-day-old calves was 14 micromol/l and approximately 11-fold lower than in blood plasma. Salivary NOx- decreased postnatally from 600 to 200 micromol/l at 2 days and to 25 micromol/l at 4 weeks. Urinary NOx- excretion decreased from 125 or 16 micromol/l per kg x 24 h in 5-day-old calves to 45 or 8 micromol/kg x 24 h between 10 and 115 days of life and was undetectable in urine of heifers and cows. Feeding neonatal calves no or variable amounts of colostrum, delaying colostrum intake by 24 h after birth or feeding at different feeding intensity had no effect on the NOx- status. In conclusion, the high plasma, salivary and urinary NOx- concentrations especially in newborn calves, ingesting but insignificant amounts of nitrite or nitrate, indicated marked endogenous formation of nitrate, which decreased with age. The high nitrate status may contribute to enhanced susceptibility of young calves to exogenous nitrite+nitrite ingestion.

The humoral immune response to recombinant nucleocapsid antigen of canine distemper virus in dogs vaccinated with attenuated distemper virus or DNA encoding the nucleocapsid of wild-type virus

This study compared the humoral immune response against the nucleocapsid-(N) protein of canine distemper virus (CDV) of dogs vaccinated with a multivalent vaccine against parvo-, adeno-, and parainfluenza virus and leptospira combined with either the attenuated CDV Onderstepoort strain (n = 15) or an expression plasmid containing the N-gene of CDV (n = 30). The vaccinations were applied intramuscularly three times at 2-week intervals beginning at the age of 6 weeks. None of the pre-immune sera recognized the recombinant N-protein, confirming the lack of maternal antibodies at this age. Immunization with DNA vaccine for CDV resulted in positive serum N-specific IgG response. However, their IgG (and IgA) titres were lower than those of CDV-vaccinated dogs. Likewise, DNA-vaccinated dogs did not show an IgM peak. There was no increase in N-specific serum IgE titres in either group. Serum titres to the other multivalent vaccine components were similar in both groups.

Disappearance of beta2-adrenergic receptors on astrocytes in canine distemper encephalitis: possible implications for the pathogenesis of multiple sclerosis

It has been reported that astrocytes in the white matter of patients with multiple sclerosis (MS) lack beta2-adrenergic receptors. This abnormality might explain why astrocytes in active MS plaques aberrantly express major histocompatibility (MHC) class II molecules, which play an important role in the immunological cascade leading to myelin destruction. Canine distemper (CD) virus primarily infects astrocytes and causes a demyelinating disease in dogs that closely resembles MS. In control dogs, including three dogs with another inflammatory disease, beta2-adrenergic receptor immunoreactivity was observed on both neurons and astrocytes. In dogs with CD encephalitis, beta2-adrenergic receptors were present on neurons, but were absent on astrocytes in acute lesions, demyelinated lesions, and normal-appearing white matter. Similar to MS, several astrocytes in demyelinated lesions expressed MHC class II. These findings suggest that MS and the demyelinating stages of CD encephalitis have a common pathogenetic factor, and that the loss of astrocytic beta2-adrenergic receptors in MS might be induced by a viral infection of astrocytes.

Quantitative assessment of mast cells and expression of IgE protein and mRNA for IgE and interleukin 4 in the gastrointestinal tract of healthy dogs and dogs with inflammatory bowel disease

OBJECTIVE

To characterize the mucosal IgE network in dogs affected with inflammatory bowel disease (IBD) and compare it with that for healthy dogs.

ANIMALS

9 healthy dogs and 20 dogs with IBD.

PROCEDURE

In situ hybridization of mRNA specific for IgE and interleukin 4 (IL-4) and immunohistochemical analysis for IgE protein and 2 markers of mast cells (ie, tryptase and chymase) were performed on tissue sections obtained from the gastrointestinal (GI) tract and lymph nodes of dogs.

RESULTS

Dogs with IBD had significantly more cells positive for IgE protein and more mast cells in the GI mucosa than healthy dogs. Despite this significant increase in number of cells positive for IgE, cells positive for IgE mRNA were rarely detected in the GI mucosa; most cells positive for IgE mRNA were found in mesenteric lymph nodes. Signal pattern of IL-4 mRNA was similar to that of IgE mRNA.

CONCLUSIONS AND CLINICAL RELEVANCE

The increased numbers of cells positive for IgE and mast cells in dogs with IBD suggest hypersensitivity such as hypersensitivity to bacterial or dietary-derived antigens in the intestinal lumen. Future studies need to elucidate whether this represents a cause of inflammation or is a result of the inflammatory process of IBD.

A negative search for a paramyxoviral etiology of Paget's disease of bone: molecular, immunological, and ultrastructural studies in UK patients

Paget's disease of bone is a common bone disease characterized by increased and disorganized bone remodeling at focal sites throughout the skeleton. The etiology of the disease is unresolved. A persistent viral infection has long been suggested to cause the disease. Antigen and/or nucleic acid sequences of paramyxoviruses (in particular measles virus [MV], canine distemper virus [CDV], and respiratory syncytial virus [RSV]) have been reported in pagetic bone by a number of groups; however, others have been unable to confirm this and so far no virus has been isolated from patients. Here, we reexamined the question of viral involvement in Paget's disease in a study involving 53 patients with established disease recruited from seven centers throughout the United Kingdom. Thirty-seven patients showed clear signs of active disease by bone scan and/or histological assessment of the bone biopsy specimens and 12 of these had not received any therapy before samples were taken. Presence of paramyxovirus nucleic acid sequences was sought in bone biopsy specimens, bone marrow, or peripheral blood mononuclear cells using reverse-transcription polymerase chain reaction (RT-PCR) with a total of 18 primer sets (7 of which were nested), including 10 primer sets (including 3 nested sets) specifically for MV or CDV. For each patient at least one sample was tested with all primer sets by RT-PCR and no evidence for the presence of paramyxovirus RNA was found in any patient. In 6 patients, bone biopsy specimens with clear histological evidence of active disease tested negative for presence of measles and CDV using immunocytochemistry (ICC) and in situ hybridization (ISH). Intranuclear inclusion bodies, similar to those described by others previously, were seen in pagetic osteoclasts. The pagetic inclusions were straight, smooth tubular structures packed tightly in parallel bundles and differed from nuclear inclusions, known to represent MV nucleocapsids, in a patient with subacute sclerosing panencephalitis (SSPE) in which undulating, diffuse structures were found, arranged loosely in a nonparallel fashion. In the absence of amplification of viral sequences from tissues that contain frequent nuclear inclusions and given that identical inclusions are found in other bone diseases with a proven genetic, rather than environmental, etiology, it is doubtful whether the inclusions in pagetic osteoclasts indeed represent viral nucleocapsids. Our findings in this large group of patients recruited from throughout the United Kingdom do not support a role for paramyxovirus in the etiology of Paget's disease.

A monomer-dimer equilibrium of a cellular prion protein (PrPC) not observed with recombinant PrP

Both the purified normal (protease-sensitive) isoform of the prion protein (PrP(C)) (Pergami, P., Jaffe, H., and Safar, J. (1996) Anal. Biochem. 236, 63-73) and recombinant prion protein (PrP) have been found to be in monomeric form (Mehlhorn, I., Groth, D., Stockel, J., Moffat, B., Reilly, D., Yansura, D., Willet, W. S., Baldwin, M., Fletterick, R., Cohen, F. E., Vandlen, R., Henner, D., and Prusiner, S. B. (1996) Biochemistry 35, 5528-5537; and this paper), and therefore PrP(C)-PrP(C) interactions were previously unknown. In this report we confirm recombinant PrP to be a monomer by analytical ultracentrifugation. However, by three lines of evidence (enzyme-linked immunosorbent assay (ELISA), cross-linking experiments, and size exclusion chromatography) we could also demonstrate that, under native conditions, at least part of the native bovine PrP(C) exists as a monomer-dimer equilibrium. A bovine PrP(C)-specific immuno-sandwich ELISA was developed and calibrated with recombinant PrP (Meyer, R. K., Oesch, B., Fatzer, R., Zurbriggen, A., and Vandevelde, M. (1999) J. Virol. 73, 9386-9392). By this ELISA we identified a distinct PrP(C) fraction and partially purified this protein. When serial dilutions of brain homogenate or partially purified PrP(C) were measured, using the peptide antibody C15S, a nonlinear dose-response curve was obtained. This nonlinearity was shown not to be due to an artifact of the procedure but to a monomer-dimer equilibrium of PrP(C) with preferential binding of the antibody to the dimer. From the curvature we could deduce the association constant (3.9 x 10(8) M(-1) at 37 degrees C). Accordingly, DeltaG degrees of the reaction was calculated (-48.6 kJ M(-1)), and DeltaH degrees (9.5 kJ M(-1)) as well as DeltaS degrees (0.2 kJ K(-1) M(-1)) were extrapolated from the van't Hoff plot. When serial dilutions of monomeric recombinant PrP were tested, only a straight line was obtained, supporting our hypothesis. Additional evidence of dimer formation was revealed by Western blotting of partially purified PrP(C) cross-linked by the homobifunctional cross-linker BS(3). Finally, size exclusion chromatography of partially purified PrP(C) fractions revealed an additional shoulder not observed with recombinant PrP. The difference in respect of dimer formation between native PrP(C) and recombinant PrP could be explained by the lack of glycosylation of the latter.

mRNA of insulin-like growth factor (IGF) quantification and presence of IGF binding proteins, and receptors for growth hormone, IGF-I and insulin, determined by reverse transcribed polymerase chain reaction, in the liver of growing and mature male cattle

Plasma insulin-like growth factor-I (IGF-I) concentrations were related to hepatic levels of IGF-I mRNA measured by competitive reverse transcription polymerase chain reaction (PCR) (RT-PCR) in neonatal (8 d old) calves, veal calves, fattened castrated bulls and mature intact bulls. Furthermore, the presence of mRNAs of IGF-II and of receptors for IGF-I (IGF-IR), growth hormone (GHR) and insulin (IR), as well as mRNAs of IGF binding proteins (IGFBP-1, -2 and -3) were assessed by RT-PCR. Hepatic IGF-I mRNA levels and plasma IGF-I concentrations in veal calves, fattened castrated bulls and in intact bulls were 4 to 8 times higher than in 8-d old calves and were 2 to 3 times higher in calves fed colostrum than in calves fed only milk replacer. Hepatic IGF-I mRNA concentrations were closely correlated (r = 0.92) with plasma IGF-I concentrations, suggesting that hepatic IGF-I production largely determines plasma IGF-I levels. The presence of IGF II, IGF-IR, GHR, IR and IGFBP-1, -2 and -3 mRNA was confirmed in the liver of 8-d old calves and older cattle as well, and among newborn calves their presence was independent of differences in nutrition. In conclusion, the major hepatic components of the GH-IGF axis were present in neonatal calves, but the IGF-I expression and therefore also plasma IGF-I levels were relatively low.

Antibodies to CD9, a tetraspan transmembrane protein, inhibit canine distemper virus-induced cell-cell fusion but not virus-cell fusion

Canine distemper virus (CDV) causes a life-threatening disease in several carnivores including domestic dogs. Recently, we identified a molecule, CD9, a member of the tetraspan transmembrane protein family, which facilitates, and antibodies to which inhibit, the infection of tissue culture cells with CDV (strain Onderstepoort). Here we describe that an anti-CD9 monoclonal antibody (MAb K41) did not interfere with binding of CDV to cells and uptake of virus. In addition, in single-step growth experiments, MAb K41 did not induce differences in the levels of viral mRNA and proteins. However, the virus release of syncytium-forming strains of CDV, the virus-induced cell-cell fusion in lytically infected cultures, and the cell-cell fusion of uninfected with persistently CDV-infected HeLa cells were strongly inhibited by MAb K41. These data indicate that anti-CD9 antibodies selectively block virus-induced cell-cell fusion, whereas virus-cell fusion is not affected.

DNA vaccine encoding nucleocapsid and surface proteins of wild type canine distemper virus protects its natural host against distemper

Canine distemper virus (CDV), a member of the genus Morbillivirus induces a highly infectious, frequently lethal disease in dogs and other carnivores. Current vaccines against canine distemper consisting of attenuated viruses have been in use for many years and have greatly reduced the incidence of distemper in the dog population. However, certain strains may not guarantee adequate protection and others can induce post vaccinal encephalitis. We tested a DNA vaccine for its ability to protect dogs, the natural host of CDV, against distemper. We constructed plasmids containing the nucleocapsid, the fusion, and the attachment protein genes of a virulent canine distemper virus strain. Mice inoculated with these plasmids developed humoral and cellular immune responses against CDV antigens. Dogs immunized with the expression plasmids developed virus-neutralizing antibodies. Significantly, vaccinated dogs were protected against challenge with virulent CDV, whereas unvaccinated animals succumbed to distemper.

Feline infectious pneumonia: a short literature review and a retrospective immunohistological study on the involvement of Chlamydia spp. and distemper virus

A short literature review of feline infectious pneumonia, feline Chlamydia and Paramyxoviridae is presented. In a retrospective study (from 1987 to 1996) 245 cases of feline pneumonia or conjunctivitis/rhinitis were investigated: histological diagnoses and aetiologies were compared; all lungs were examined immunohistologically for the occurrence of chlamydia and of canine distemper virus (CDV), but neither pathogen could be demonstrated. The results confirm previous reports indicating that feline chlamydia is not a primarily pulmonary pathogen and that CDV is not a causative agent of pneumonia in cats as it is in large felids. The review provides a summary of the known causes and pathology of infectious pneumonia in cats (in order of frequency), although some remain aetiologically uncertain. It focuses on chlamydia and distemper virus - a recognized and as yet unknown cause of feline pneumonia. The role and especially the frequency of chlamydia as a cause of feline pneumonia are controversial but distemper virus, known to cause pneumonia in dogs and large felids, has not as yet been demonstrated in cats. The aims of the retrospective study were to determine the occurrence of chlamydia in 245 cases of feline pneumonia or conjunctivitis/rhinitis, and to investigate the presence of CDV in these lungs.

Detection of bovine spongiform encephalopathy-specific PrP(Sc) by treatment with heat and guanidine thiocyanate

The conversion of a ubiquitous cellular protein (PrP(C)), an isoform of the prion protein (PrP), to the pathology-associated isoform PrP(Sc) is one of the hallmarks of transmissible spongiform encephalopathies such as bovine spongiform encephalopathy (BSE). Accumulation of PrP(Sc) has been used to diagnose BSE. Here we describe a quantitative enzyme-linked immunosorbent assay (ELISA) that involves antibodies against epitopes within the protease-resistant core of the PrP molecule to measure the amount of PrP in brain tissues from animals with BSE and normal controls. In native tissue preparations, little difference was found between the two groups. However, following treatment of the tissue with heat and guanidine thiocyanate (Gh treatment), the ELISA discriminated BSE-specific PrP(Sc) from PrP(C) in bovine brain homogenates. PrP(Sc) was identified by Western blot, centrifugation, and protease digestion experiments. It was thought that folding or complexing of PrP(Sc) is most probably reversed by the Gh treatment, making hidden antigenic sites accessible. The digestion experiments also showed that protease-resistant PrP in BSE is more difficult to detect than that in hamster scrapie. While the concentration of PrP(C) in cattle is similar to that in hamsters, PrP(Sc) sparse in comparison. The detection of PrP(Sc) by a simple physicochemical treatment without the need for protease digestion, as described in this study, could be applied to develop a diagnostic assay to screen large numbers of samples.

Nuclear DNA fragmentation and immune reactivity in bovine spongiform encephalopathy

To investigate whether apoptosis contributes to neuronal degeneration in bovine spongiform encephalopathy (BSE), morphological changes consistent with apoptosis were sought and in-situ end labelling (ISEL) was applied, in a series of 20 BSE cases and 10 age-matched normal control cattle. Apoptotic changes were not found in neurons but were occasionally seen in glial cells. Relatively few ISEL-positive neurons were found, but many labelled nuclei were seen in glial cells in certain areas. None of the labelled cells showed morphological features of apoptosis. ISEL(+)cells occurred in areas of spongiform change and other areas of grey matter lacking spongiform change. Some association was found between degree of cellular DNA fragmentation and accumulation of abnormal prion protein (PrP(Sc)). Interestingly, small or moderate numbers of T lymphocytes, not present in the normal central nervous system (CNS), were detected in the CNS parenchyma in most BSE cases. There was a pronounced astrogliosis, but markers of macrophage or microglial activation were only slightly increased. The results indicate that nuclear DNA vulnerability is enhanced in certain neuroanatomical areas in BSE, but evidence that apoptosis plays a role in neuronal loss in BSE was very limited. 1999 Harcourt Publishers Ltd.

Restricted virus protein translation in canine distemper virus inclusion body polioencephalitis

In this study, inclusion body polioencephalitis, an uncommon form of canine distemper virus (CDV)-induced encephalitis, was investigated for viral protein and mRNA expression by immunohistochemistry (IH) and in situ hybridization and, in addition, infiltrating cells were characterized by IH. Lesions were predominantly found in the grey matter of the brain stem and the immune response, dominated by T cells, was associated with a strong MHC II upregulation. Abundant expression of all viral protein mRNAs and reduced or lacking protein translation, especially of the matrix protein were the most important findings, indicating that restricted virus infection in the grey matter might represent a mechanism for viral persistence in distemper polioencephalitis.

Oligodendroglial degeneration in distemper: apoptosis or necrosis?

Canine distemper virus (CDV) causes a multifocal demyelinating disease in dogs. It was previously shown that the initial demyelinating lesions are directly virus induced since a correlation between the occurrence of demyelination and CDV replication in white matter cells was observed. During the course of infection oligodendrocytes undergo distinct morphological alterations, partly due to a restricted CDV infection of these cells, and eventually disappear from the lesions. This phenomenon has been described in vivo as well as in vitro. However, the reason for the morphological alterations and the following oligodendroglial depletion remained unclear. Since virus infection can induce cell death, it was investigated whether apoptosis or necrosis plays a role in the pathogenesis of demyelination in canine distemper. In brain tissue sections from dogs with acute distemper apoptotic cells were not detected within the demyelinating lesions using morphological and biochemical cell death criteria. In chronic distemper, apoptotic cells - presumably inflammatory cells - were seen within the perivascular cuffs. These in vivo findings were correlated to the in vitro situation using CDV-infected primary dog brain cell cultures as well as Vero cells. Infection with culture-adapted CDV lead to massive necrosis but not to apoptosis. After infection with virulent CDV neither apoptosis nor necrosis was a predominant feature in either culture system. These findings suggest that virus-induced demyelination in canine distemper is not the direct consequence of apoptosis or necrosis. It is speculated that another mechanism must be responsible for the observed morphological alterations of oligodendrocytes, ultimately leading to demyelination.

Detection of IgM antibodies against a recombinant nucleocapsid protein of canine distemper virus in dog sera using a dot-blot assay

A dot-blot assay for the detection of IgM antibodies (ABs) against canine distemper virus (CDV) in canine serum is described. The diagnostic potential of this technique was evaluated by analysing sera from three test groups: (i) specific pathogen-free (SPF) beagle dogs experimentally infected with virulent CDV; (ii) SPF dogs immunized with a combined vaccine containing CDV, and (iii) SPF dogs immunized with a CDV-free vaccine. As antigen for the dot-blot assay we used the recombinant nucleocapsid protein (N protein) of the virulent A75/17 CDV strain. All 12 dogs of group 1, infected with virulent CDV, showed detectable CDV-specific IgM levels in their serum. All dogs of group 2 were also positive for anti-CDV IgM after the first immunization with the CDV-containing vaccine. The four dogs immunized with a CDV-free vaccine (group iii) remained negative throughout the course of the experiment. From these results, we conclude that the IgM detection test, which requires only a single serum sample, is a useful method for diagnosing current or recent CDV infection in CDV-infected or CDV-immunized dogs under experimental conditions.

Sequence analysis and expression of the attachment and fusion proteins of canine distemper virus wild-type strain A75/17

The biological properties of wild-type A75/17 and cell culture-adapted Onderstepoort canine distemper virus differ markedly. To learn more about the molecular basis for these differences, we have isolated and sequenced the protein-coding regions of the attachment and fusion proteins of wild-type canine distemper virus strain A75/17. In the attachment protein, a total of 57 amino acid differences were observed between the Onderstepoort strain and strain A75/17, and these were distributed evenly over the entire protein. Interestingly, the attachment protein of strain A75/17 contained an extension of three amino acids at the C terminus. Expression studies showed that the attachment protein of strain A75/17 had a higher apparent molecular mass than the attachment protein of the Onderstepoort strain, in both the presence and absence of tunicamycin. In the fusion protein, 60 amino acid differences were observed between the two strains, of which 44 were clustered in the much smaller F2 portion of the molecule. Significantly, the AUG that has been proposed as a translation initiation codon in the Onderstepoort strain is an AUA codon in strain A75/17. Detailed mutation analyses showed that both the first and second AUGs of strain A75/17 are the major translation initiation sites of the fusion protein. Similar analyses demonstrated that, also in the Onderstepoort strain, the first two AUGs are the translation initiation codons which contribute most to the generation of precursor molecules yielding the mature form of the fusion protein.

Lymphocyte subset distribution in steroid responsive meningitis-arteriitis in comparison to different canine encephalitides

Steroid responsive meningitis-arteriitis (SRMA) is a well-known disease in dogs, but the aetiology and pathogenesis are not yet understood. In the peripheral blood an overrepresentation of B cells was found. In the present study we therefore evaluated the distribution of lymphocyte subsets in SRMA in paraffin-embedded tissue sections directly at the lesion sites and compared the results to different canine encephalitides. An intriguing finding was that the B cell/T cell distribution varied depending on the aetiology of the disease: in viral encephalitides, T cells were the predominant cell population in perivascular cuffs, whereas in protozoal and bacterial diseases B cells prevailed. In SRMA an overrepresentation of B cells occurred in meningeal lesions, as already found in the peripheral blood. The distribution of lymphocyte subsets was similar to bacterial and protozoal diseases and was not a unique phenomenon for this specific inflammatory lesion in the canine central nervous system (CNS). Multiple mechanisms seem to be responsible for recruitment and activation of different leukocyte subsets after alteration of the CNS tissue by an environmental factor. A specific finding in SRMA was that the distribution of T and B cells depended also on the lesion site. In contrast to meningeal lesions, in inflamed arteries T cells were the only lymphocyte population found. In these vessels, diffuse infiltration with immunoglobulins was revealed. Inactivated or resting lymphocytes and large granular lymphocytes occurred in each of the diseases examined. These similarities between SRMA and infectious CNS diseases of the dog support earlier suggestions that the disease is somehow triggered by a hitherto unknown environmental factor which leads to the dysregulation of the immune system.

Early T cell response in the central nervous system in canine distemper virus infection

The initial demyelinating lesions in canine distemper virus (CDV) infection develop during a period of severe immunosuppression in the absence of inflammation. In vitro and in vivo studies suggest that early demyelination is due to directly virus-induced oligodendroglial changes. In the present spatiotemporal study in experimentally CDV-infected dogs we observed diffuse up-regulation of T cells throughout the central nervous system (CNS) and T cell invasion in early demyelinating lesions. Invasion of T cells in the CNS occurred despite severe immunosuppression and without any perivascular cuffing. However, the major fraction of invading T cells correlated with sites of viral replication and coincided with the demonstration of an early immune response against the nucleocapsid protein of CDV. Activation of microglial cells was thought to have elicited the migration of T cells to the CNS by secretion of chemokines: marked IL-8 activity was found in the CSF of dogs with acute lesions. In areas of early demyelination, large numbers of CD3+ cells accumulated in the tissue in the absence of any morphological sign of inflammation. Whether the T cells at lesion sites contribute to the development of acute demyelination remains uncertain at this stage. Antiviral cytotoxicity was not apparent since viral clearance in demyelinating lesions is only effective when B cells and concurring antiviral antibody production appeared in the subacute and chronic inflammatory stage of the disease. CD3+ cells appear to persist for several weeks after infection since they were also found in recovered dogs that did not develop demyelination. Accumulation of immune cells, including a significant proportion of resting T cells (CD45RA+) in the CNS in the early stages of the disease may facilitate the later development of the intrathecal immune response and associated immunopathological complications.

Dose-dependent priming or desensitization induced by chemotactic agents in chemiluminescence experiments with canine and human neutrophils

We explored whether receptor-specific desensitization in repeated stimulation offers an opportunity to identify chemotactic factors particularly in species, e.g. the dog, for which immunochemical methods to determine chemotactic factors are not commercially available. Complement fragment 5a and interleukin-8 act via distinct receptors. They were used as test agents for neutrophils in luminol-dependent chemiluminescence. These experiments led to the observation that exposure of human and canine neutrophils to low concentrations of a chemotactic agent shows an increased response when stimulated again with the same agent (priming). In the heterologous system even cross-priming could be observed after a second stimulation with another agent. The concentration at which priming rather than desensitization occurred were lower for homologous factor-cell combinations (<10-20 nM) than for heterologous combinations (<45-60 nM). The mechanism underlying this phenomenon is unknown. However, it raises the possibility that it subserves an important function in the recruitment and activation of cells by low agonist concentration. This study shows that despite the phenomenon of priming receptor-specific desensitization may be used to determine chemotactic agents in the homologous system.

Neuropathological and aetiological studies of sporadic non-suppurative meningoencephalomyelitis of cattle

Sporadically occurring non-suppurative encephalitis appears to be a frequent condition of Swiss cattle. Fifty-one such cases diagnosed over a period of 10 years were examined retrospectively to investigate whether they constituted one or more distinct diseases, and to search for aetiological agents. Three cases were characterised by periventricular granulomatous encephalitis, and most probably represented a different disease, but the remaining 48 cases had disseminated non-suppurative encephalitis with widespread neuronal changes. Neuronal degeneration was very marked in the hippocampus of 10 cases and in the cerebellar Purkinje cells of 11. It was thought that the latter cases represented morphological variations of the same disease rather than a different disease because of their overlapping morphological features. The 48 cases had the following features in common: the disease had primarily neurological signs affecting mostly adult cattle, it was a sporadic condition, and there was a clear tendency for it to have a subacute to chronic course. Polymerase chain reaction (PCR) amplification for chlamydial DNA was negative except in one of 32 specimens, and immunohistochemistry did not demonstrate the presence of chlamydial antigens either in the one PCR-positive case or in the other cases examined. Immunohistochemistry for rabies virus, Borna disease virus, and central European tickborne encephalitis virus was negative. In four cases, immunolabelled cells were found in the lesions with antibodies against paramyxovirus antigens.