Five cases of scrapie with unusual features have been diagnosed in Norway since 1998. The affected sheep showed neurological signs dominated by ataxia, and had the PrP genotypes homozygous A136 H154 Q171/ A136H154Q171 or heterozygous A136H154Q171/A136R154Q171, which are rarely associated with scrapie. Brain histopathology revealed neuropil vacuolisation essentially in the cerebellar and cerebral cortices; vacuolation was less prominent in the brainstem, and no lesions were observed at the level of the obex. The deposits of PrPSc were mainly in the cortex of the cerebellum and cerebrum, and no PrPSC was detectable by immunohistochemistry and ELISA in the lymphoid tissues investigated. Western blot analysis showed that the glycotype was different from other known scrapie strains and from the BSE strain. From a diagnostic point of view, these features indicate that this type of scrapie, designated Nor98, could have been overlooked and may be of significance for sampling in scrapie surveillance programmes.

The immune system is known to be involved in the early phase of scrapie pathogenesis. However, the infection route of naturally occurring scrapie and its spread within the host are not entirely known. In this study, the pathogenesis of scrapie was investigated in sheep of three PrP genotypes, from 2 to 9 months of age, which were born and raised together in a naturally scrapie-affected Romanov flock. The kinetics of PrP Sc accumulation in sheep organs were determined by immunohistochemistry. PrP Sc was detected only in susceptible VRQ/VRQ sheep, from 2 months of age, with an apparent entry site at the ileal Peyer's patch as well as its draining mesenteric lymph node. At the cellular level, PrP Sc deposits were associated with CD68-positive cells of the dome area and B follicles before being detected in follicular dendritic cells. In 3-to 6-month-old sheep, PrP Sc was detected in most of the gut-associated lymphoid tissues (GALT) and to a lesser extent in more systemic lymphoid formations such as the spleen or the mediastinal lymph node. All secondary lymphoid organs showed a similar intensity of PrP Sc -immunolabelling at 9 months of age. At this time-point, PrPSc was also detected in the autonomic myenteric nervous plexus and in the nucleus parasympathicus nervi X of the brain stem. These data suggest that natural scrapie infection occurs by the oral route via infection of the Peyer's patches followed by replication in the GALT. It may then spread to the central nervous system through the autonomic nervous fibres innervating the digestive tract.

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The Mycobacterium tuberculosis complex (MTBC) is the collective term given to the group of bacteria that cause tuberculosis (TB) in mammals. It has been reported that M. tuberculosis H37Rv, a standard reference MTBC strain, is attenuated in cattle compared to Mycobacterium bovis. However, as M. tuberculosis H37Rv was isolated in the early 1930s, and genetic variants are known to exist, we sought to revisit this question of attenuation of M. tuberculosis for cattle by performing a bovine experimental infection with a recent M. tuberculosis isolate. Here we report infection of cattle using M. bovis AF2122/97, M. tuberculosis H37Rv, and M. tuberculosis BTB1558, the latter isolated in 2008 during a TB surveillance project in Ethiopian cattle. We show that both M. tuberculosis strains caused reduced gross pathology and histopathology in cattle compared to M. bovis. Using M. tuberculosis H37Rv and M. bovis AF2122/97 as the extremes in terms of infection outcome, we used RNA-Seq analysis to explore differences in the peripheral response to infection as a route to identify biomarkers of progressive disease in contrast to a more quiescent, latent infection. Our work shows the attenuation of M. tuberculosis strains for cattle, and emphasizes the potential of the bovine model as a ‘One Health’ approach to inform human TB biomarker development and post-exposure vaccine development.

Abstract. 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.

Cellular prion protein (Prp(C)) is a glycoprotein usually associated with membranes via its glycosylphosphatidylinositol (GPI) anchor. The trans-conformational form of this protein (Prp(SC)) is the suggested agent responsible for transmissible neurodegenerative spongiform encephalopathies. This protein has been shown on sperm and in the reproductive fluids of males. Antibodies directed against the C-terminal sequence near the GPI-anchor site, an N-terminal sequence, and against the whole protein showed that the Prp isoforms were compartmentalized within the reproductive tract of the ram. Immunoblotting with the three antibodies showed that the complete protein and both N- and C-terminally truncated and glycosylated isoforms are present within cauda epididymal fluid and seminal plasma. Moreover, we demonstrate that in these fluids, the Prp(C) isoforms are both in a soluble state as well as associated with small membranous vesicles (epididymosomes). We also report that only one major glycosylated 25 kDa C-terminally truncated Prp(C) isoform is associated with sperm from the testis, cauda epididymis, and semen, and this form is also present in the sperm cytoplasmic droplets that are released during maturation. In sperm, this C-terminal truncated form was found to be associated with membrane lipid rafts present in the mature sperm, suggesting a role for it in the terminal stages of sperm maturation.