Appendix Figure 2. Proteinase K (PK) sensitivity of 21 Norwegian isolates in mild conditions. The ELISA typing test was performed on 20 Nor98 isolates and 1 Norwegian scrapie isolate (Lavik) by using the protective A´´ reagent, with a PK concentration of 1.2 µg/mg tissue. These new conditions (PK 1.2 µg/mg of tissue in A´´ reagent) showed a large range of PK resistance with normalized ratios varying from 1.4 for the most resistant (Lindas isolate), close to the experimental ovine BSE, to >14 for the weakest (Soknedal2). One isolate, Tennevoll, appeared so sensitive to PK digestion that the ratio could not be evaluated (>95) even using these protective conditions.