Ex-vivo brain slice culture model for chronic wasting disease

Authors: KONDRU, NAVEEN - Iowa State University; MANNE, SIREESHA - Iowa State University; Kokemuller, Robyn; Greenlee, Justin; WEST GREENLEE, M - Iowa State University; NICHOLS, TRACY - US Department Of Agriculture (USDA); KONG, QINGZHONG - Case Western Reserve University (CWRU); ANANTHARAM, VELLAREDDY - Iowa State University; KANTHASAMY, ARTHI - Iowa State University; HALBUR, PATRICK - Iowa State University; KANTHASAMY, ANUMANTHA - Iowa State University

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2020
Publication Date: 5/6/2020
Citation: Kondru, N., Manne, S., Kokemuller, R., Greenlee, J.J., West Greenlee, M.H., Nichols, T., Kong, Q., Anantharam, V., Kanthasamy, A., Halbur, P., Kanthasamy, A. 2020. Ex-vivo brain slice culture model for chronic wasting disease. Scientific Reports. 10:7640. https://doi.org/10.1038/s41598-020-64456-9.
DOI: https://doi.org/10.1038/s41598-020-64456-9

Interpretive Summary: Prion diseases are invariably fatal neurologic diseases for which there is no known prevention or cure. Because of long incubation times and knowledge gaps in how the disease progresses, there is not a well-defined model for testing potential cures or preventative measures. This manuscript describes an ultrasensitive in vitro modeling system for chronic wasting disease (CWD) infectivity of samples from deer or elk. In the first step, prion agents are cultured on a brain slice derived from a prion-susceptible mouse. In the second step, an in vitro prion amplification technique (Real-Time Quaking Induced Conversion or RT-QuIC) is used to test for infectivity of the slices. This paper demonstrates the slice cultures are able to accumulate CWD prions that could be detected by RT-QuIC and more traditional laboratory methods such as mouse bioassay and immunohistochemistry. In addition, three compounds with potential anti-prion properties were screened using slice culture and RT-QuIC indicating that this model may be useful in developing potential treatment schemes for prion disease. Because mechanisms of neurodegeneration in prion disease are similar to other protein misfolding diseases such as Alzheimer’s disease and Parkinson’s disease, use of this model could have a major impact on improving treatments for other neurodegenerative diseases.

Technical Abstract: Modeling diseases using the ex-vivo platform accelerates the study of prions and other protein misfolding diseases (PMDs) that have long incubation times. Chronic wasting disease (CWD) is a prion disease of cervids that has an incubation period between 18 and 36 months. CWD has been rapidly spreading in the past few decades, yet it remains difficult to diagnose, treat, or control. We have recently developed an integrated organotypic slice culture assay for sensitive detection of scrapie prions using ultrasensitive prion seeding. However, this model is not established for CWD prions as CWD prions have a strong transmission barrier from deer to standard laboratory mice (Mus musculus). Therefore, we utilized a transgenic mouse model that expresses the elk prion protein gene (PRNP) (Tg12; prnp+/-) to develop and characterize the ex-vivo brain slice culture model for CWD. We tested for CWD infectivity in the cultured slices using sensitive seeding assays such as the real-time quaking-induced conversion (RT-QuIC) assay and protein misfolding cyclic amplification (PMCA), along with conventional methods such as western blot and immunohistochemistry. Slice cultures from the brains of Tg12 mice tested positive for CWD, but slice cultures from the prnp-/- mice did not. The CWD prions generated in slices were transmitted efficiently to transgenic mice and subsequently passed into a second generation producing a reduction in the incubation period. Further, we established the activity of anti-prion compounds and the diagnostic utility of this CWD slice culture model. Our results demonstrate this integrated brain slice model of CWD provides a means to study the mechanisms as well as the implications of CWD diagnosis.