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Research Project: Rapid Antemortem Tests for the Early Detection of Transmissible Spongiform Encephalopathies and Other Animal Diseases

Location: Produce Safety and Microbiology Research

Title: Quantifying the molecular properties of the Elk Chronic Wasting Disease Agent with mass spectrometry

Author
item Silva, Christopher
item Erickson-Beltran, Melissa
item Cassmann, Eric
item Greenlee, Justin

Submitted to: Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2024
Publication Date: 11/16/2024
Citation: Silva, C.J., Erickson-Beltran, M.L., Cassmann, E.D., Greenlee, J.J. 2024. Quantifying the molecular properties of the Elk Chronic Wasting Disease Agent with mass spectrometry. Pathogens. 13(11). Article 1008. https://doi.org/10.3390/pathogens13111008.
DOI: https://doi.org/10.3390/pathogens13111008

Interpretive Summary: Chronic wasting disease (CWD) is rapidly spreading among wild and farmed elk. The CWD contagion replicates by inducing a protein to adopt the CWD shape. An amino acid at position 132 (either leucine (L) or methionine (M)) in CWD determines how CWD progresses. A sensitive analytical technique was used to analyze CWD from six infected elk. These elk had either two Ls (LL132), two Ms (MM132) or one L and one M (LM132) at position 132. CWD from these six samples was processed for analysis to yield six protein fragments. These protein fragments were used to determine the amount of CWD in each sample, the proportion of M and L in the two samples with one L and one M, and the amount of oxidation in each protein fragment. The MM132 sample contained 540 units of CWD, the ML132 samples contained 330 or 360 units, and the three LL132 samples contained either 20, 70 or 20 units. ML132 CWD contained 41% L and 59% M. Oxidized protein fragments were present in all six samples. This work showed that this analytical technique can be used to characterize CWD at a molecular level that cannot be done by other means.

Technical Abstract: Chronic wasting disease (CWD) is a prion disease afflicting wild and farmed elk. CWD prions (PrPSc) are infectious protein conformations that replicate by inducing a natively expressed prion protein (PrPC) to adopt a prion conformation. Mass spectrometry was used to study the prions resulting from a previously described experimental inoculation of MM132, ML 132 and LL 132 elk with a common CWD inoculum. Chymotryptic digestion times and instrument parameters were optimized to yield a set of six peptides, TNMK,MLGSAMSRPL, LLGSAMSRPL, ENMYR, MMER, and WEQMCITQYQR. These peptides were used to quantify the amount, the M132 and L 132 polymorphic composition, and the extent of methionine oxidation of elk PrPSc. The amount (ng/g brain tissue) of PrPSc present in each sample was calculated as: MM132 (5.4 x 102 ± 7 x101 ), ML 132 (3.3 x 102 ± 6 x101 and 3.6 x 102 ± 3 x101 ) and LL 132 (0.7 x 102 ± 1 x101, 0.2 x 102 ± 0.2 x101,and 0.2 x 102 ± 0.5 x101 ). The proportion of L 132 polymorphism in ML 132 (heterozygous) PrPSc from CWDinfected elk was determined to be 41% ± 4%. Methionine oxidation was detected and quantified for the M132 and L 132 polymorphisms in the samples. In this way mass spectrometry can be used to characterize prion strains at a molecular level.