LPS-induced systemic inflammation reveals an immunomodulatory role for the prion protein at the blood-brain interface.

BACKGROUND: The cellular prion protein (PrPC) is an evolutionary conserved protein abundantly expressed not only in the central nervous system but also peripherally including the immune system. A line of Norwegian dairy goats naturally devoid of PrPC (PRNP Ter/Ter) provides a novel model for studying PrPC physiology. METHODS: In order to explore putative roles for PrPC in acute inflammatory responses, we performed a lipopolysaccharide (LPS, Escherichia coli O26:B6) challenge of 16 goats (8 PRNP +/+ and 8 PRNP Ter/Ter) and included 10 saline-treated controls (5 of each PRNP genotype). Clinical examinations were performed continuously, and blood samples were collected throughout the trial. Genome-wide transcription profiles of the choroid plexus, which is at the blood-brain interface, and the hippocampus were analyzed by RNA sequencing, and the same tissues were histologically evaluated. RESULTS: All LPS-treated goats displayed clinical signs of sickness behavior, which were of significantly (p < 0.01) longer duration in animals without PrPC. In the choroid plexus, a substantial alteration of the transcriptome and activation of Iba1-positive cells were observed. This response included genotype-dependent differential expression of several genes associated with the immune response, such as ISG15, CXCL12, CXCL14, and acute phase proteins, among others. Activation of cytokine-responsive genes was skewed towards a more profound type I interferon response, and a less obvious type II response, in PrPC-deficient goats. The magnitude of gene expression in response to LPS was smaller in the hippocampus than in the choroid plexus. Resting state expression profiles revealed a few differences between the PRNP genotypes. CONCLUSIONS: Our data suggest that PrPC acts as a modulator of certain pathways of innate immunity signaling, particularly downstream of interferons, and probably contributes to protection of vulnerable tissues against inflammatory damage.

Early neonatal lamb mortality: postmortem findings.

An investigation of stillbirth and early neonatal lamb mortality was conducted in sheep flocks in Norway. Knowledge of actual causes of death are important to aid the interpretation of results obtained during studies assessing the risk factors for lamb mortality, and when tailoring preventive measures at the flock, ewe and individual lamb level. This paper reports on the postmortem findings in 270 liveborn lambs that died during the first 5 days after birth. The lambs were from 17 flocks in six counties. A total of 27% died within 3 h after birth, 41% within 24 h and 80% within 2 days. Most lambs (62%) were from triplet or higher order litters. In 81% of twin and larger litters, only one lamb died. The most frequently identified cause of neonatal death was infectious disease (n=97, 36%); 48% (n=47) of these died from septicaemia, 25% (n=24) from pneumonia, 22% (n=21) from gastrointestinal infections and 5% (n=5) from other infections. Escherichia coli accounted for 65% of the septicaemic cases, and were the most common causal agent obtained from all cases of infection (41%). In total, 14% of neonatal deaths resulted from infection by this bacterium. Traumatic lesions were the primary cause of death in 20% (n=53) of the lambs. A total of 46% of these died within 3 h after birth and 66% within 24 h. Severe congenital malformations were found in 10% (n=27) of the lambs, whereas starvation with no concurrent lesions was the cause of death in 6% (n=17). In 16% (n=43) of the lambs, no specific cause of death was identified, lambs from triplet and higher order litters being overrepresented among these cases. In this study, the main causes of neonatal lamb mortality were infection and traumatic lesions. Most neonatal deaths occurred shortly after birth, suggesting that events related to lambing and the immediate post-lambing period are critical for lamb survival.

Acute and Chronic Erysipelothrix rhusiopathiae Infection in Lambs.

Polyarthritis caused by Erysipelothrix rhusiopathiae is a relatively common infection in lambs characterized by low mortality and high morbidity. E. rhusiopathiae is a ubiquitous Gram-positive bacterium that is both a commensal and a pathogen of vertebrates. The disease was studied during an outbreak in a Norwegian Spæl sheep flock. In the acute phase, 48 of 230 (20%) lambs developed clinical signs and 4 died (1.7%). One acute case was necropsied and E. rhusiopathiae was cultured from all major organs investigated and from joints. There was a fibrinous polyarthritis, increased presence of monocytes in vessels, and necrosis of Purkinje cells. Sixteen of the diseased animals (33%) developed a chronic polyarthritis. Eight of these lambs were necropsied; all had lesions in major limb joints, and 3 of 8 also had lesions in the atlanto-occipital joint. At this stage, E. rhusiopathiae was cultured only from the joints in 7 of 8 (87.5%) lambs, but by real-time polymerase chain reaction, we showed persistence of the bacterium in several organs. Pulsed-field gel electrophoresis typing of the bacterial isolates indicated that the same strain caused the acute and chronic disease. Five of 6 (83%) chronically affected animals had amyloidosis of the spleen, and 6 of 8 (75%) had amyloidosis of the liver. All chronically affected animals had a glomerulonephritis, and 6 of 8 (75%) had sparse degeneration in the brain. Ceruloplasmin and haptoglobin were significantly increased in the chronically diseased lambs. These results show that chronic ovine erysipelas is not restricted to joints but is a multisystemic disease.

Abnormal prion protein is associated with changes of plasma membranes and endocytosis in bovine spongiform encephalopathy (BSE)-affected cattle brains.

AIMS: Transmissible spongiform encephalopathies (TSEs) or prion diseases are fatal neurodegenerative diseases of man and animals characterized by vacuolation and gliosis of neuropil and the accumulation of abnormal isoforms of a host protein known as prion protein (PrP). It is widely assumed that the abnormal isoforms of PrP (PrP(d), disease-specific form of PrP) are the proximate cause of neurodegeneration. METHODS: To determine the nature of subcellular changes and their association with PrP(d) we perfusion-fixed brains of eight bovine spongiform encephalopathy (BSE)-affected cows and three control cattle for immunogold electron microscopy at two different neuroanatomical sites. RESULTS: All affected cattle presented plasma membrane alterations of dendrites and astrocytes that were labelled for PrP(d). PrP(d) on membranes of dendrites and occasionally of neuronal perikarya was associated with abnormal endocytotic events, including bizarre coated pits and invagination of the plasma membrane. BSE-affected cattle also presented excess and abnormal multivesicular bodies, sometimes associated to the plasma membrane perturbations. In contrast, two TSE-specific lesions, vacuolation and rare tubulovesicular bodies, were not labelled for PrP(d) as were a number of other nonspecific lesions, such as autophagy and dystrophic neurites. At least two different morphological pathways to vacuoles were recognized. CONCLUSIONS: When compared with other TSEs, these changes are common to those of sheep and rodent scrapie and shows that there are consistent membrane toxicity properties of PrP(d). This toxicity involves an aberration of endocytosis. However, it is by no means clear that the lesions are of sufficient severity to result in clinical deficits.

Mapping PrPSc propagation in experimental and natural scrapie in sheep with different PrP genotypes.

Twenty-one orally inoculated and seven naturally infected sheep with scrapie were examined for PrP(Sc) in peripheral tissues and in the central nervous system (CNS), using immunohistochemistry. In the inoculated group, VRQ (valine at codon 136, arginine at codon 154 and glutamine at codon 171)/VRQ sheep generally had a greater accumulation of the pathologic form of prion protein (PrP(Sc)) in peripheral tissues, as compared with VRQ/ARQ (alanine at codon 136, arginine at codon 154, and glutamine at codon 171) animals at corresponding time points after inoculation. PrP(Sc) was not detected in the ileal Peyer's patch, the spleen, the superficial cervical lymph node, and peripheral nervous tissues of several inoculated VRQ/ARQ animals. All inoculated VRQ/VRQ sheep, but only one of eight inoculated VRQ/ARQ animals, were PrP(Sc)-positive in the CNS. Thus, the propagation of PrP(Sc) seemed slower and more limited in VRQ/ARQ animals. Tissue and cellular localization of PrP(Sc) suggested that PrP(Sc) was disseminated through three different routes. PrP(Sc)-positive cells in lymph node sinuses and in lymphatics indicated spreading by lymph. The sequential appearance of PrP(Sc) in the peripheral nervous system and the CNS, with satellite cells as early targets, suggested the periaxonal transportation of PrP(Sc) through supportive cells. Focal areas of vascular amyloid-like PrP(Sc) in the brain of five sheep, suggested the hematogenous dissemination of PrP(Sc). There was a poor correlation between the amount of PrP(Sc) in the CNS and clinical signs. One subclinically affected sheep showed widespread PrP(Sc) accumulation in the CNS, whereas three sheep had early clinical signs without detectable PrP(Sc) in the CNS. A VV(136) (homozygous for valine at codon 136) sheep inoculated with ARQ/ARR (alanine at codon 136, arginine at codon 154, and arginine at codon 171) tissue succumbed to disease, demonstrating successful heterologous transmission. Less susceptible sheep receiving VRQ/VRQ or ARQ/ARR material were PrP(Sc)-negative by immunohistochemistry, enzyme-linked immunosorbent assay, and western blot.

Accumulation of pathogenic prion protein (PrPSc) in nervous and lymphoid tissues of sheep with subclinical scrapie.

All sheep older than 1 year of age from a flock of the Rygja breed in which clinical scrapie was detected for the first time in two animals (4%) were examined for accumulation of pathogenic prion protein (PrPSc) by immunohistochemistry in the obex, the cerebellum, and the medial retrophayngeal lymph node. In addition, six lambs, 2-3 months old, all offspring of PrPSc-positive dams, were examined for PrPSc in the ileal Peyers' patch (IPP), the distal jejunal lymph node, the spleen, and the medial retropharyngeal lymph node (RPLN). In this flock, 35% (17/48) of the adult sheep showed accumulation of PrPSc, an eightfold increase compared with clinical disease. All positives carried susceptible PrP genotypes. Three sheep had deposits of PrPSc in the RPLN and not in the brain, suggesting that this organ, easily accessible at slaughter, is suitable for screening purposes. Two 7-year-old clinically healthy homozygous V136Q171 ewes showed sparse immunostaining in the central nervous system and may have been infected as adults. Further, two littermates, 86-days-old, showed PrPSc in the IPP. Interestingly, one of these lambs had the intermediate susceptible PrP genotype, VA136QR171. In addition to early immunolabeling in the dorsal motor nucleus of the vagal nerve, a few of the sheep had early involvement of the cerebellum. In fact, a 2-year-old sheep had sparse deposits of PrPSc in the cerebellum only. Because experimental bovine spongiform encephalopathy (BSE) in sheep seems to behave in a similar manner as natural scrapie, these results, particularly regarding spread of infectivity, may have implications for the handling of BSE should it be diagnosed in sheep.

An epidemiological study of cataracts in seawater farmed Atlantic salmon Salmo salar.

Cataracts in farmed Atlantic salmon have been known for many years, but the aetiology and importance of the disease have not been clarified. A cross-sectional field study of 51 cages of Atlantic salmon at 49 randomly selected sea sites was performed during the summer of 1998. The target population was spring and autumn entry groups of the 1997 generation salmon. Approximately 15 fish from each cage, altogether 777 fish, were autopsied by the same person. Each eye of the fish was scored for cataracts on a scale from 0 to 4 using an otoscope lamp with magnification. The weight and length of each fish were measured. The prevalence of cataracts was 83 % and 79% in spring entry groups and autumn entry groups, respectively. The overall mean cataract index (mean score of both eyes) was 1.23, being significantly higher in the spring entry groups (1.36) than the autumn entry groups (0.85). The final results in the spring entry groups showed that the fish groups with higher weight at sea transfer also had a higher cataract index at inspection. The risk of development of cataracts varied significantly among the offspring from the 5 strains represented in the study. Fish from sites located in 2 counties in the southern part of Norway had a significantly higher cataract index than fish farmed in the northernmost county in the study. For the autumn entry groups none of the explanatory variables was significant. In the spring entry groups a significant negative relationship was observed between the cataract score and the weight of the fish at the time of inspection (Pearson's r = -0.17), while the corresponding correlation for the autumn released groups was r = -0.10. Among the spring entry groups the average weight of the fish with the highest cataract score was estimated to about a third of the weight of the fish with no visible cataracts.