Lack of prion transmission by sexual or parental routes in experimentally infected hamsters

Nasal bots carry relevant titers of CWD prions in naturally infected white-tailed deer

Chronic wasting disease (CWD) is a prion disease affecting farmed and free-ranging cervids. CWD is rapidly expanding across North America and its mechanisms of transmission are not completely understood. Considering that cervids are commonly afflicted by nasal bot flies, we tested the potential of these parasites to transmit CWD. Parasites collected from naturally infected white-tailed deer were evaluated for their prion content using the protein misfolding cyclic amplification (PMCA) technology and bioassays. Here, we describe PMCA seeding activity in nasal bot larvae collected from naturally infected, nonclinical deer. These parasites efficiently infect CWD-susceptible mice in ways suggestive of high infectivity titers. To further mimic environmental transmission, bot larvae homogenates were mixed with soils, and plants were grown on them. We show that both soils and plants exposed to CWD-infected bot homogenates displayed seeding activity by PMCA. This is the first report describing prion infectivity in a naturally occurring deer parasite. Our data also demonstrate that CWD prions contained in nasal bots interact with environmental components and may be relevant for disease transmission.

Detection of CWD prions in naturally infected white-tailed deer fetuses and gestational tissues by PMCA

Chronic wasting disease (CWD) is a prevalent prion disease affecting cervids. CWD is thought to be transmitted through direct animal contact or by indirect exposure to contaminated environmental fomites. Other mechanisms of propagation such as vertical and maternal transmissions have also been suggested using naturally and experimentally infected animals. Here, we describe the detection of CWD prions in naturally-infected, farmed white-tailed deer (WTD) fetal tissues using the Protein Misfolding Cyclic Amplification (PMCA) technique. Prion seeding activity was identified in a variety of gestational and fetal tissues. Future studies should demonstrate if prions present in fetuses are at sufficient quantities to cause CWD after birth. This data confirms previous findings in other animal species and furthers vertical transmission as a relevant mechanism of CWD dissemination.

In Vitro detection of Chronic Wasting Disease (CWD) prions in semen and reproductive tissues of white tailed deer bucks (Odocoileus virginianus)

Chronic Wasting Disease (CWD) is a prion disease affecting several cervid species. Among them, white-tailed deer (WTD) are of relevance due to their value in farming and game hunting. The exact events involved in CWD transmission in captive and wild animals are still unclear. An unexplored mechanism of CWD spread involves transmissions through germplasm, such as semen. Surprisingly, the presence and load of CWD prions in semen and male sexual tissues from WTD has not been explored. Here, we described the detection of CWD prions in semen and sexual tissues of WTD bucks utilizing the Protein Misfolding Cyclic Amplification (PMCA) technology. Samples were obtained post-mortem from farmed pre-clinical, CWD positive WTD bucks possessing polymorphisms at position 96 of the PRNP gene. Our results show that overall CWD detection in these samples had a sensitivity of 59.3%, with a specificity of 97.2%. The data indicate that the presence of CWD prions in male sexual organs and fluids is prevalent in late stage, pre-clinical, CWD-infected WTD (80%-100% of the animals depending on the sample type analyzed). Our findings reveal the presence of CWD prions in semen and sexual tissues of prion infected WTD bucks. Future studies will be necessary to determine whether sexual contact and/or artificial inseminations are plausible means of CWD transmission in susceptible animal species.

The Endoplasmic Reticulum Chaperone GRP78/BiP Modulates Prion Propagation in vitro and in vivo

Prion diseases are fatal neurodegenerative disorders affecting several mammalian species, characterized by the accumulation of the misfolded form of the prion protein, which is followed by the induction of endoplasmic reticulum (ER) stress and the activation of the unfolded protein response (UPR). GRP78, also called BiP, is a master regulator of the UPR, reducing ER stress levels and apoptosis due to an enhancement of the cellular folding capacity. Here, we studied the role of GRP78 in prion diseases using several in vivo and in vitro approaches. Our results show that a reduction in the expression of this molecular chaperone accelerates prion pathogenesis in vivo. In addition, we observed that prion replication in cell culture was inversely related to the levels of expression of GRP78 and that both proteins interact in the cellular context. Finally, incubation of PrP^Sc with recombinant GRP78 led to the dose-dependent reduction of protease-resistant PrP^Scin vitro. Our results uncover a novel role of GRP78 in reducing prion pathogenesis, suggesting that modulating its levels/activity may offer a novel opportunity for designing therapeutic approaches for these diseases. These findings may also have implications for other diseases involving the accumulation of misfolded proteins.

Diagnosing Sporadic Creutzfeldt-Jakob Disease by the Detection of Abnormal Prion Protein in Patient Urine

IMPORTANCE

Creutzfeldt-Jakob disease (CJD) is a fatal neurodegenerative disorder associated with the accumulation of infectious abnormal prion protein through a mechanism of templated misfolding. A recent report has described the detection of abnormal prion protein in the urine of patients with variant CJD (vCJD) using protein misfolding by cyclic amplification, which was apparently absent in the more common sporadic form of CJD (sCJD). A noninvasive diagnostic test could improve early diagnosis of sCJD and, by screening donations, mitigate the potential risks of prion transmission through human urine-derived pharmaceuticals. Here, we describe the adaptation of the direct detection assay, developed originally as a blood test for vCJD, for the detection of disease-associated prion protein in urine samples from patients with sCJD.

OBJECTIVE

To determine the feasibility of sCJD diagnosis by adaptation of an established vCJD diagnostic blood test to urine.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective, cross-sectional study included anonymized urine samples from healthy nonneurological control individuals (n = 91), patients with non-prion neurodegenerative diseases (n = 34), and patients with prion disease (n = 37) of which 20 had sCJD. Urine samples obtained during the Medical Research Council PRION-1 Trial, the National Prion Monitoring Cohort Study, and/or referred to the National Prion Clinic or Dementia Research Centre at the National Hospital for Neurology and Neurosurgery in the United Kingdom.

MAIN OUTCOMES AND MEASURES

Presence of sCJD infection determined by an assay that captures, enriches, and detects disease-associated prion protein isoforms.

RESULTS

A total of 162 samples were analyzed, composed of 91 normal control individuals (51 male, 33 female, and 7 not recorded), 34 neurological disease control individuals (19 male and 15 female), and 37 with prion disease (22 male and 15 female). The assay's specificity for prion disease was 100% (95% CI, 97%-100%), with no false-positive reactions from 125 control individuals, including 34 from a range of neurodegenerative diseases. In contrast to a previous study, which used a different method, sensitivity to vCJD infection was low (7.7%; 95% CI, 0.2%-36%), with only 1 of 13 patients with positive test results, while sensitivity to sCJD was unexpectedly high at 40% (95% CI, 19%-64%).

CONCLUSIONS AND RELEVANCE

We determined 40% of sCJD urine sample results as positive. To our knowledge, this is the first demonstration of an assay that can detect sCJD infection in urine or any target analyte outside of the central nervous system. Urine detection could allow the development of rapid, molecular diagnostics for sCJD and has implications for other neurodegenerative diseases where disease-related assemblies of misfolded proteins might also be present in urine.

Secretin receptor involvement in prion-infected cells and animals

The cellular mechanisms behind prion biosynthesis and metabolism remain unclear. Here we show that secretin signaling via the secretin receptor regulates abnormal prion protein formation in prion-infected cells. Animal studies demonstrate that secretin receptor deficiency slightly, but significantly, prolongs incubation time in female but not male mice. This gender-specificity is consistent with our finding that prion-infected cells are derived from females. Therefore, our results provide initial insights into the reasons why age of disease onset in certain prion diseases is reported to occur slightly earlier in females than males.