After infection, total PrP in the proliferating cells did not change, and only a small amount of PrP-res (1.2% of total PrP) was detectable for up to 81 days p.i. With a short 5 day arrest at 37.5°C-2% serum, infected SEP cells, as previous control uninfected cells [22], rapidly displayed a 7 fold increase in total PrP, 0.6% of which is PrP-res. Here, PRNP is linked to infection.