Sensitivity of protein misfolding cyclic amplification versus immunohistochemistry in ante-mortem detection of chronic wasting disease

As the only prion disease affecting free-ranging animals, ante-mortem identification of affected cervids has become paramount in understanding chronic wasting disease (CWD) pathogenesis, prevalence and control of horizontal or vertical transmission. To seek maximal sensitivity in ante-mortem detection of CWD infection, this study used paired tonsil biopsy samples collected at various time points from 48 CWD-exposed cervids to compare blinded serial protein misfolding cyclic amplification (sPMCA) with the assay long considered the ‘gold standard’ for CWD detection, immunohistochemistry (IHC). sPMCA-negative controls (34% of the samples evaluated) included tissues from mock-inoculated animals and unspiked negative controls, all of which tested negative throughout the course of the study. It was found that sPMCA on tonsil biopsies detected CWD infection significantly earlier (2.78 months, 95% confidence interval 2.40–3.15) than conventional IHC. Interestingly, a correlation was observed between early detection by sPMCA and host PRNP genotype. These findings demonstrate that in vitro-amplification assays provide enhanced sensitivity and advanced detection of CWD infection in the peripheral tissues of cervids, with a potential role for spike or substrate genotype in sPMCA amplification efficiency.