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Tissue Digestion - Technical Information

> Composition of Mammals
> Digestion of Radioiodine Labeled Tissues
> Efficacy Testing Results
> Formaldehyde Destruction
> Prion Destruction
> The Effect on Plant and Animal Tissues
> Water Usage

Prion Destruction

Transmissible degenerative encephalopathies have been found in sheep, goats, mink, elk, mule deer, cattle, exotic ungulates, domestic cats, exotic felids, and humans in the form of CJD, Gerstmann-Straussler-Scheinker syndrome, fatal familial insomnia, and kuru.

New variant Creutzfeldt-Jakob Disease (nvCJD) is the variety of CJD that has been linked to Bovine Spongiform Encephalopathy (BSE or mad-cow disease). Prion protein has been isolated in tonsils, the spleen, and lymph nodes of those with nvCJD (Hill, et. al.).

All of the following has proved to be ineffective in reliably inactivating the many strains of prions that have been tested in all kinds of materials, including those previously exposed to fixing agents:
Any form of autoclaving alone
Radiation methods
Most forms of chemical inactivation

Therefore, surgical instruments that have been in contact with tonsils, the spleen, lymph nodes, as well as tissues of the central nervous system and the eye of those with nvCJD are potentially infectious, even after sterilization by any conventionally used sterilization method.

Clearly the most effective way to inactivate all prions in tests has been to expose them to sodium hydroxide or potassium hydroxide at elevated temperatures. Boiling in a 1M solution for 60 seconds completely inactivated all prions in one study, and 15 minutes in another study.

Dr. David Taylor's laboratory at the Institute of Animal Health, Neuropathogenesis Unit, developed the 301-V strain of mouse-passaged BSE agent, a highly resistant agent, which is being used to test the efficacy of the WR2 Tissue Digestor in a study which has been funded by the U.K. Ministry of Agriculture, Food, and Fisheries.

To date, recognized experts recommend the following treatment:
Taguchi et al: 1M NaOH/1 hour followed by porous load autoclaving at 121 degrees Celsius for 30 minutes
Prusiner: Porous load autoclaving at 121 degrees Celsius for 90 minutes in the presence of 1 M NaOH
Taylor et al: Porous load autoclaving at 121 degrees Celsius for 30 minutes in the presence of 2 M NaOH

Health Canada is using a 100-Lab-30 WR2 Tissue Digestor for their Prion Research Facility in Winnipeg.

The USDA ARS is using the WR2 Tissue Digestor for their BSL-3 Arbovirus Research Facility in Laramie, Wyoming, where it has also been used to digest scrapie sheep & CWD infected elk and deer.

Any WR2 Tissue Digestor standard cycle exposes all materials to the equivalent of 1M NaOH for 3 hours at 150°C (302°F).