A Field-Deployable Diagnostic Assay for the Visual Detection of Misfolded Prions

Abstract

AbstractDiagnostic tools for the detection of protein-misfolding diseases (i.e., proteopathies) are limited. Gold nanoparticles (AuNPs) facilitate sensitive diagnostic techniques via visual color change for the detection of a variety of targets. In parallel, recently developed quaking-induced conversion (QuIC) assays leverage protein-amplification and fluorescent signaling for the accurate detection of misfolded proteins. Here, we combine AuNP and QuIC technologies for the visual detection of amplified misfolded prion proteins from tissues of wild white-tailed deer infected with chronic wasting disease (CWD), a prion disease of cervids. Our newly developed assay, MN-QuIC™, enables both naked-eye and light-absorbance measurements for detection of misfolded prions. MN-QuIC™ leverages basic laboratory equipment that is cost-effective and portable, thus facilitating real-time prion diagnostics across a variety of settings. To test the portability of our assay, we deployed to a rural field-station in southeastern Minnesota and tested for CWD on site. We successfully demonstrated that MN-QuIC™ is functional in a non-traditional laboratory setting by performing a blinded analysis in the field and correctly identifying all CWD positive and CWD not detected deer at the field site in less than 24 hours, thus documenting the portability of the assay. Additionally, we show that electrostatic forces help govern the AuNP/prion interactions. Importantly, all of our white-tailed deer (n=37) were independently tested using ELISA, IHC, and/or RT-QuIC technologies and results secured with MN-QuIC™ were 100% consistent with these tests. We conclude that hybrid AuNP and QuIC assays, such as MN-QuIC™, have great potential for sensitive, field-deployable diagnostics of a variety of protein misfolding diseases.Statement of SignificancePortable diagnostic tools for the detection of prion and protein-misfolding diseases are limited. Using chronic wasting disease (CWD) as a model, we demonstrate the functionality of a gold nanoparticle (AuNP)-based assay for the field-based detection of prion diseases. CWD is spreading through cervid populations across North America and the disease poses significant threats to a number of economic sectors, with global implications. Our newly developed diagnostic assay leverages the visible color change of AuNPs to detect the presence of CWD-causing prions. The assay can be performed using lowcost equipment and reagents, thus having great potential to expand prion disease surveillance efforts and prevent infectious prions from entering the human food chain.