Chronic and de novo infection of GT1 cell line. GT1 cells were infected according to the procedures described in the Materials and Methods section. Regarding de novo infected GT1 cells (iGT1) the presence of PrPSc was tested at the fourth passage. PrPSc was detected by PK digestion assay (PK+ lanes) and the signal revealed using Western blot technique. Approximately 20 μg of total protein were loaded as control (PK-lanes).