PRNP and Creutzfeldt Jacob disease: Because CJD patients, who received dura mater prion-contaminated transplants, were found to have increased Aβ plaques [55], another possibility is that prions increase Aβ levels through the deviation of PrPC signalling (associated to p38 and JNK-stress kinases), which could impair Aβ clearance via a decreased activity of MMP-9 metalloprotease [56].