Transmission studies of chronic wasting disease to transgenic mice overexpressing human prion protein using the RT-QuIC assay

Abstract

Chronic wasting disease (CWD) is a fatal prion disease which infects deer, elk and moose. CWD was first described as a wasting syndrome in captive deer in Colorado and Wyoming wildlife facilities from 1967 to 1979. Currently, CWD has been reported in 26 states of the USA, three Canadian provinces, South Korea, Norway and Finland. Since human consumption of cervids is common, it is critical to determine if CWD can infect humans. Published research, including epidemiologic studies and transmission studies using animal models, including transgenic mice that express human prion protein, have suggested existence of a strong species barrier between cervid CWD and humans. In the current study, we tested CWD transmission into two additional strains of transgenic mice (tg66 and tgRM). These mice over-express human prion protein at high levels and are highly sensitive to infection by human-tropic prions. One hundred and eight mice were inoculated intracerebrally with three different sources of CWD. After long periods of observation, brain tissues from CWD-inoculated mice were screened for evidence of prion infection by RT-QuIC, immunohistochemistry (IHC) and immunoblot. No IHC or immunoblot evidence was found to suggest transmission had occurred, and most mice were negative by RT-QuIC assay. However, four mice with inconsistent positive RT-QuIC reactions were detected. The seeding activity detected in these mice may represent a low level of CWD agent, suggesting a possible transfer of CWD infection. Alternatively, these results might be due to false positive reactions or residual CWD inoculum.Electronic supplementary materialThe online version of this article (10.1186/s13567-019-0626-2) contains supplementary material, which is available to authorized users.

Transmission characteristics of heterozygous cases of Creutzfeldt-Jakob disease with variable abnormal prion protein allotypes

“…For both mouse strains, the majority of cases inoculated caused clinical disease in at least some of the mice. As expected, disease incubation times were generally shorter in the tg66 mice which express higher levels of human PrP C -M129 when compared to the tgRM mice [38]. Only two samples, case 4 and the CC sample from case 9, failed to cause any clinical disease within the lifetime of the host, although neuropathology and PrP Sc deposition were observed in a few mice suggesting that clinical disease may have eventually developed in those animals.…”

Update on chronic wasting disease (CWD) III

“…Nevertheless, Race et al. () recently published a study performed with two lineages of humanised mice that provided intriguing results. They exposed tgRM and tg66 mice, which overexpress MM human PrP at levels two‐ to fourfold and 8‐ to 16‐fold higher than the physiological levels, respectively, to different CWD sources.…”

“…These two models harbour the highest levels of PrP c expression among all those that have been tested in these studies. Among these mice, 7% (3/45) tgRM and 30% (15/52) tg66 mice fitted the ‘criteria as prion disease suspects’ that the authors considered to be relevant and that correspond to ‘signs of wasting, weakness, neurologic disease and behavioural changes’ (Race et al., ). Extensive analyses of the brains of these animals did not provide any lesional, biochemical or immunohistochemical element that could confirm the diagnosis of prion disease and the authors expressed some reservations about the relevance of those observations because of the advanced age of these animals (> 500 days of incubation).…”

“…PMCA Efficient conversion of human PrP by CWD from elk and experimentally challenged reindeer, depending on human genotype, cervid genotype and cervid species Barria et al (2018) Chronic Wasting Disease (CWD) III Nevertheless, Race et al (2019) recently published a study performed with two lineages of humanised mice that provided intriguing results. They exposed tgRM and tg66 mice, which overexpress MM human PrP at levels two-to fourfold and 8-to 16-fold higher than the physiological levels, respectively, to different CWD sources.…”

Alpha-synuclein seeds in olfactory mucosa of patients with isolated rapid-eye-movement sleep behaviour disorder

“…OM sampling provides direct access to olfactory neurons and thus to one of the sites, that is currently regarded as one of the potential initiation points of seeding and spread of pathological α-syn assemblies in Parkinson's disease. RT-QuIC for α-syn detects disease-associated α-syn aggregates in billion-fold diluted brain tissue preparations from different α-synucleinopathies (Groveman et al, 2018) with a higher sensitivity than conventional immunohistochemistry, as shown in prion diseases (Race et al, 2019). RT-QuIC results are classified as negative or positive based on the extent of α-syn aggregates seeding and do not depend on observer evaluation, as occurs for -syn immunohistochemistry in skin biopsies of patients with iRBD (Donadio et al, 2019).…”