Extended period of asymptomatic prion disease after low dose inoculation: Assessment of detection methods and implications for infection control

Abstract

We used quantal dose-titration of a mouse-adapted human transmissible spongiform encephalopathy strain (M470) to compare different analytical methods for their ability to detect asymptomatic brain prion infection after low dose inoculation. At a time point approximately 2.5-fold beyond the mean incubation period of high dose inocula, asymptomatic brain infection was commonly observed using histologic examination, Western blot, and "blind" bioassay following intracerebral inoculation with low titer inocula. At this time point, when a clinical end-point titration would usually be determined, evidence of infection was seen in all healthy animals inoculated with up to 100-fold lower inoculation ..