Propagation of RML Prions in Mice Expressing PrP Devoid of GPI Anchor Leads to Formation of a Novel, Stable Prion Strain

PrPC, a host protein which in prion-infected animals is converted to PrPSc, is linked to the cell membrane by a GPI anchor. Mice expressing PrPC without GPI anchor (tgGPI- mice), are susceptible to prion infection but accumulate anchorless PrPSc extra-, rather than intracellularly. We investigated whether tgGPI− mice could faithfully propagate prion strains despite the deviant structure and location of anchorless PrPSc. We found that RML and ME7, but not 22L prions propagated in tgGPI− brain developed novel cell tropisms, as determined by the Cell Panel Assay (CPA). Surprisingly, the levels of proteinase K-resistant PrPSc (PrPres) in RML- or ME7-infected tgGPI− brain were 25–50 times higher than in wild-type brain. When returned to wild-type brain, ME7 prions recovered their original properties, however RML prions had given rise to a novel prion strain, designated SFL, which remained unchanged even after three passages in wild-type mice. Because both RML PrPSc and SFL PrPSc are stably propagated in wild-type mice we propose that the two conformations are separated by a high activation energy barrier which is abrogated in tgGPI− mice

The Complete Genome Sequence of the Pathogenic Intestinal Spirochete Brachyspira pilosicoli and Comparison with Other Brachyspira Genomes

Background: The anaerobic spirochete Brachyspira pilosicoli colonizes the large intestine of various species of birds and mammals, including humans. It causes ''intestinal spirochetosis'', a condition characterized by mild colitis, diarrhea and reduced growth. This study aimed to sequence and analyse the bacterial genome to investigate the genetic basis of its specialized ecology and virulence. Methodology/Principal Findings: The genome of B. pilosicoli 95/1000 was sequenced, assembled and compared with that of the pathogenic Brachyspira hyodysenteriae and a near-complete sequence of Brachyspira murdochii. The B. pilosicoli genome was circular, composed of 2,586,443 bp with a 27.9 mol% G+C content, and encoded 2,338 genes. The three Brachyspira species shared 1,087 genes and showed evidence of extensive genome rearrangements. Despite minor differences in predicted protein functional groups, the species had many similar features including core metabolic pathways. Genes distinguishing B. pilosicoli from B. hyodysenteriae included those for a previously undescribed bacteriophage that may be useful for genetic manipulation, for a glycine reductase complex allowing use of glycine whilst protecting from oxidative stress, and for aconitase and related enzymes in the incomplete TCA cycle, allowing glutamate synthesis and function of the cycle during oxidative stress. B. pilosicoli had substantially fewer methyl-accepting chemotaxis genes than B. hyodysenteriae and hence these species are likely to have different chemotactic responses that may help to explain their different host range and colonization sites. B. pilosicoli lacked the gene for a new putative hemolysin identified in B. hyodysenteriae WA1. Both B. pilosicoli and B. murdochii lacked the rfbBADC gene cluster found on the B. hyodysenteriae plasmid, and hence were predicted to have different lipooligosaccharide structures. Overall, B. pilosicoli 95/1000 had a variety of genes potentially contributing to virulence. Conclusions/Significance: The availability of the complete genome sequence of B. pilosicoli 95/1000 will facilitate functional genomics studies aimed at elucidating host-pathogen interactions and virulence

Excretion of BSE and scrapie prions in stools from murine models

Faeces from infected animals have been suggested as a potential source of contamination and transmission of prion diseases in the environment. This work describes the development of a procedure for the detection of PrP(res) in stools which is based on a detergent-based extraction and immunoprecipitation (IP). The procedure was evaluated by analyzing TSE-spiked sheep and mice faeces, and proved to be specific for PrP(res) with sensitivities of 5-10 microg of infected brain tissue. In order to analyze the shedding of prions, we studied stools from orally inoculated mice over 4-days post-inoculation and also stools from terminally sick scrapie-infected mice. PrP(res) was only detected in stools shortly after the oral ingestion of TSE agents. The procedure described could be a useful tool for studying the excretion of prions and for evaluating potential environmental contamination by prions

Excretion of BSE and scrapie prions in stools from murine models

Faeces from infected animals have been suggested as a potential source of contamination and transmission of prion diseases in the environment. This work describes the development of a procedure for the detection of PrP(res) in stools which is based on a detergent-based extraction and immunoprecipitation (IP). The procedure was evaluated by analyzing TSE-spiked sheep and mice faeces, and proved to be specific for PrP(res) with sensitivities of 5-10 microg of infected brain tissue. In order to analyze the shedding of prions, we studied stools from orally inoculated mice over 4-days post-inoculation and also stools from terminally sick scrapie-infected mice. PrP(res) was only detected in stools shortly after the oral ingestion of TSE agents. The procedure described could be a useful tool for studying the excretion of prions and for evaluating potential environmental contamination by prions

Sheep-passaged bovine spongiform encephalopathy agent exhibits altered pathobiological properties in bovine-PrP transgenic mice.

Sheep can be experimentally infected with bovine spongiform encephalopathy (BSE), and the ensuing disease is similar to scrapie in terms of pathogenesis and clinical signs. BSE infection in sheep is an animal and human health concern. In this study, the transmission in BoPrP-Tg110 mice of prions from BSE-infected sheep was examined and compared to the transmission of original cattle BSE in cattle and sheep scrapie prions. Our results indicate no transmission barrier for sheep BSE prions to infect BoPrP-Tg110 mice, but the course of the disease is accelerated compared to the effects of the original BSE isolate. The shortened incubation period of sheep BSE in the model was conserved in subsequent passage in BoPrP-Tg110 mice, indicating that it is not related to infectious titer differences. Biochemical signature, lesion profile, and PrP(Sc) deposition pattern of both cattle and sheep BSE were similar. In contrast, all three sheep scrapie isolates tested showed an evident transmission barrier and further adaptation in subsequent passage. Taken together, those data indicate that BSE agent can be altered by crossing a species barrier, raising concerns about the virulence of this new prion towards other species, including humans. The BoPrP-Tg110 mouse bioassay should be considered as a valuable tool for discriminating scrapie and BSE in sheep