Humanized Transgenic Mice Are Resistant to Chronic Wasting Disease Prions From Norwegian Reindeer and Moose

Abstract

Chronic wasting disease (CWD) is the transmissible spongiform encephalopathy or prion disease affecting cervids. In 2016, the first cases of CWD were reported in Europe in Norwegian wild reindeer and moose. The origin and zoonotic potential of these new prion isolates remain unknown. In this study to investigate zoonotic potential we inoculated brain tissue from CWD-infected Norwegian reindeer and moose into transgenic mice overexpressing human prion protein. After prolonged postinoculation survival periods no evidence for prion transmission was seen, suggesting that the zoonotic potential of these isolates is low.

Keywords: chronic wasting disease (CWD); moose; prion; prion disease; prion protein; reindeer; transgenic mice; transmissible spongiform encephalopathy (TSE).

Figure 1.

Immunoblot analyses of CWD-negative and CWD-infected Norwegian reindeer and moose brain. A and B, Immunoblots of brain homogenates analyzed with anti-PrP monoclonal antibody ICSM 35 and high-sensitivity enhanced chemiluminescence. A, Brain homogenates, 10% (w/v), from a CWD-negative reindeer (16-04-V176; normal) and CWD-infected reindeer (16-04-V142; CWD) analyzed before (−) or after (+) digestion with PK (50 µg/mL final protease concentration, 1 hour, 37°C). The provenance of the brain sample is designated above each lane. Loading volumes for the immunoblot were 2.5 µL of PK− and 10 µL of PK+ 10% (w/v) brain homogenate. B, Brain homogenates, 10% (w/v), from a CWD-negative moose (16-60-P195; normal), and CWD-infected moose (16-60-P153 and 16-60-P138; CWD). The provenance of the brain sample is designated above each lane. Samples were analyzed with (+) or without (−) PK digestion (50 µg/mL final protease concentration, 1 hour, 37°C) and with (+) or without (−) preconcentration by NaPTA precipitation (from 100 µL 10% (w/v) brain homogenate). The volume equivalent of 10% (w/v) brain homogenates loaded for the immunoblots was 5 µL of PK−/NaPTA−, 5 µL of PK+/NaPTA−, and 100 µL of PK+/NaPTA+. The normal cellular isoform of PrP (PrP^C) present in both normal and CWD-infected brain homogenate is completely degraded by PK, whereas the scrapie or disease-associated isoform of PrP (PrP^Sc) comprises aggregated assemblies with the C-terminal two-thirds of the protein showing marked resistance to proteolytic degradation, generating 3 bands corresponding to N-terminally truncated fragments of di-, mono-, and nonglycosylated PrP. The concentration of PrP^Sc in 10% (w/v) brain homogenate from CWD-infected moose 16-60-P153 was about 5-fold higher than CWD-infected moose 16-60-P138. Exposure times were varied to show comparable signal strength. Abbreviations: CWD, chronic wasting disease; NaPTA, sodium phosphotungstic acid; PK, proteinase K; PrP, prion protein.