In contrast with previous studies where infectivity was correlated with highest PrPres content for rodent-adapted scrapie strains17,18, our results show that the shortest survival times induced in tgElk mice did not correlate with the highest content of PrPres or total PrP among the fractions used as inoculum (Figs. 2 and 4). This evidence concerns the gene PRNP and scrapie.