Detection of prion after decontamination procedures: comparative study of standard Western blot, filter retention and scrapie-cell assay.

Prion diseases such as Creutzfeldt-Jakob disease represent a unique infection control problem because the infectious agent exhibits an unusual resistance to conventional chemical and physical decontamination methods. We investigated the reliability and sensitivity of a filter retention assay and standard Western blot to detect the scrapie form of cellular prion protein (PrPSc), the most commonly used surrogate prion disease marker, on tissue infected samples, treated with five commercially available decontamination solutions currently used in hospitals. Major discrepancies were observed between the two immunoblot methods. By using Western blot, we observed that three decontamination solutions have a strong ability to reduce PrPSc levels, whereas in the filter assay, none have this effect and two even enhanced the detection of PrPSc. We used an original and rapid ex vivo approach called the scrapie-cell assay to analyse the persistence of infectivity on scrapie-treated tissues. We observed that tissues remained infectious after treatment with the decontaminant in concordance with in vivo data. This study suggests that conventional PrPSc detection methods are not adapted for the rapid study of a large number of prion decontaminants tested on infectious tissues, and that the scrapie-cell assay could be proposed as a relevant alternative method. Copyright 2004 The Hospital Infection Society