Coexistence of protease sensitive and resistant prion protein in 129VV homozygous sporadic Creutzfeldt-Jakob disease: a case report

Abstract

Introduction: The coexistence of different molecular types of classical protease-resistant prion protein in the same individual have been described, however, the simultaneous finding of these with the recently described protease-sensitive variant or variably protease-sensitive prionopathy has, to the best of our knowledge, not yet been reported.

Case presentation: A 74-year-old Caucasian woman showed a sporadic Creutzfeldt-Jakob disease clinical phenotype with reactive depression, followed by cognitive impairment, akinetic-rigid Parkinsonism with pseudobulbar syndrome and gait impairment with motor apraxia, visuospatial disorientation, and evident frontal dysfunction features such as grasping, palmomental reflex and brisk perioral reflexes. She died at age 77.Neuropathological findings showed: spongiform change in the patient's cerebral cortex, striatum, thalamus and molecular layer of the cerebellum with proteinase K-sensitive synaptic-like, dot-like or target-like prion protein deposition in the cortex, thalamus and striatum; proteinase K-resistant prion protein in the same regions; and elongated plaque-like proteinase K-resistant prion protein in the molecular layer of the cerebellum. Molecular analysis of prion protein after proteinase K digestion revealed decreased signal intensity in immunoblot, a ladder-like protein pattern, and a 71% reduction of PrPSc signal relative to non-digested material. Her cerebellum showed a 2A prion protein type largely resistant to proteinase K. Genotype of polymorphism at codon 129 was valine homozygous.

Conclusion: Molecular typing of prion protein along with clinical and neuropathological data revealed, to the best of our knowledge, the first case of the coexistence of different protease-sensitive prion proteins in the same patient in a rare case that did not fulfill the current clinical diagnostic criteria for either probable or possible sporadic Creutzfeldt-Jakob disease. This highlights the importance of molecular analyses of several brain regions in order to correctly diagnose rare and atypical prionopathies.

Figure 1

Immunohistological (A-L) and immunoblotting (M-N) results. AC: frontal cortex; DF: temporal cortex; GL: cerebellum. Spongiform change in the frontal (A) and temporal (D) cortex and molecular layer of the cerebellum (G, H) is accompanied by moderate neuronal loss in cortex (A, D) and torpedoes in the granular layer of the cerebellum (I). PrP-immunoreactive (PrP-ir) deposits are seen in the cerebral cortex and cerebellum (B, E, J). PrP-ir is largely reduced in the cerebral cortex after proteinase K (PK) treatment, except for small PrP-ir dots following a dot-like or target-like pattern (C, F). By contrast, PrP-ir in the molecular layer of the cerebellum, in the form of elongated plaque-like deposits, is preserved after PK treatment (K, L); PrP plaques in the granular layer are absent. Paraffin sections: A, D, G, H: hematoxylin and eosin staining; I: phosphorylated neurofilament immunohistochemistry; B, C, E, F, JL: PrP immunostaining (3F4 antibody) without (B, E, J) and with (C, F, K, L) PK treatment. A, D, G, J, K, L: × 200 (bar in L, 100μm); B, C, E, F, H, I: × 400 (bar in I, 50μm). PK was used according to the indications of the supplier: 1 drop of PK concentrate (DAKO, S2019) in 1.6mL of DAKO ChemMate TM PK diluent (S2032) for 15 minutes. M: Routine immunoblotting conditions (10% brain homogenate and final PK concentration of 440μg/mL) as described elsewhere [5] and five minutes of film exposure time. PK pretreated brain regions corresponded to occipital cortex (lane 1), putamen/globus pallidus (lane 2), cerebellum (lane 3), parietal cortex (lane 4), thalamus (lane 5), frontal cortex (lane 6), temporal cortex (lane 7), sporadic Creutzfeldt–Jakob disease (sCJD) VV2 reference case occipital cortex (lane 8). N: Immunoblotting of PK pretreated samples with less stringent conditions (TeSeE® Western Blot Kit, Bio-Rad) and detection with 3F4 antibody (Dako, dilution 1:3000) as previously described [5] at ten minutes film exposure time. Brain regions corresponded to occipital cortex (lane 1), cerebellum (lane 2), parietal cortex (lane 3), thalamus (lane 4), frontal cortex (lane 5), temporal cortex (lane 6), variably protease-sensitive prionopathy 129MV parietal cortex (lane 7) [5] and sCJD VV2 reference case frontal cortex (lane 8). Molecular weight standards are indicated in kDa: (M) SDS-PAGE Standards, broad range, Bio-Rad and (N) Precision Plus Protein Unstained Standards, Bio-Rad.