l-Arginine ethylester enhances in vitro amplification of PrPSc in macaques with atypical L-type bovine spongiform encephalopathy and enables presymptomatic detection of PrPSc in the bodily fluids

Protease-resistant, misfolded isoforms (PrPSc) of a normal cellular prion protein (PrPC) in the bodily fluids, including blood, urine, and saliva, are expected to be useful diagnostic markers of prion diseases, and nonhuman primate models are suited for performing valid diagnostic tests for human Creutzfeldt-Jakob disease (CJD). We developed an effective amplification method for PrPSc derived from macaques infected with the atypical L-type bovine spongiform encephalopathy (l-BSE) prion by using mouse brain homogenate as a substrate in the presence of polyanions and l-arginine ethylester. This method was highly sensitive and detected PrPSc in infected brain homogenate diluted up to 1010 by sequential amplification. This method in combination with PrPSc precipitation by sodium phosphotungstic acid is capable of amplifying very small amounts of PrPSc contained in the cerebrospinal fluid (CSF), saliva, urine, and plasma of macaques that have been intracerebrally inoculated with the l-BSE prion. Furthermore, PrPSc was detectable in the saliva or urine samples as well as CSF samples obtained at the preclinical phases of the disease. Thus, our novel method may be useful for furthering the understanding of bodily fluid leakage of PrPSc in nonhuman primate models.