Altered properties of amyloidogenic prion protein in genetic Creutzfeldt–Jakob disease with PRNP V180I mutation in response to pentosan polysulfate

Genetic Creutzfeldt–Jakob disease (gCJD) with V180I prion protein gene (PRNP) mutation shows weaker prion protein (PrP) deposition histologically compared with sporadic CJD, and it is more difficult to detect protease‐resistant prion protein in immunoblotting. However, we previously reported the autopsy case of a patient with V180I gCJD who was treated with pentosan polysulfate sodium (PPS); this case had increased protease‐resistant PrP deposition. It has been suggested that PPS might reduce protease‐resistant PrP; however, the detailed pharmacological and histopathological effects of PPS in humans remain unknown. We examined autopsied human brain tissue from four cases with V180I gCJD that were added to our archives between 2011 and 2021: two cases treated with PPS and two cases without PPS. We conducted a neuropathological assessment, including immunohistochemistry for PrP. We also performed immunoblotting for PrP on homogenate samples from each brain to detect protease‐resistant PrP using both a conventional procedure and size‐exclusion gel chromatography for the purification of oligomeric PrP. Both PPS‐treated cases showed long survival time over 5 years from onset and increased PrP deposition with a characteristic pattern of coarse granular depositions and congophilic PrP microspheres, whereas the cases without PPS showed around 1‐year survival from onset and relatively mild neuronal loss and synaptic PrP deposition. Although cortical gliosis seemed similar among all cases, aquaporin 4‐expression as a hallmark of astrocytic function was increased predominantly in PPS cases. Immunoblotting of non‐PPS cases revealed protease‐resistant PrP in the oligomeric fraction only, whereas the PPS‐treated cases showed clear signals using conventional procedures and in the oligomeric fraction. These unique biochemical and histopathological changes may reflect the progression of V180I gCJD and its modification by PPS, suggesting the possible existence of toxic PrP‐oligomer in the pathophysiology of V180I gCJD and beneficial effects of PPS toward the aggregation and detoxication of toxic PrP‐oligomer. PrP‐positive microspheres in pentosan polysulfate sodium (PPS)‐administrated V180I‐gCJD cases. The images in (A‐D, G, H) show the cerebral cortex and (E,F) show the thalamus. Arrows indicate microspheres, arrowheads indicate foamy spheroid bodies. (A,C,E): hematoxylin–eosin staining, (B,D,F): immunohistochemistry for prion protein (PrP; clone 3F4), (G,H): Congo red sta