Strain-Dependent Morphology of Reactive Astrocytes in Human- and Animal-Vole-Adapted Prions.

Reactive astrogliosis is one of the pathological hallmarks of prion diseases. Recent studies highlighted the influence of several factors on the astrocyte phenotype in prion diseases, including the brain region involved, the genotype backgrounds of the host, and the prion strain. Elucidating the influence of prion strains on the astrocyte phenotype may provide crucial insights for developing therapeutic strategies. Here, we investigated the relationship between prion strains and astrocyte phenotype in six human- and animal-vole-adapted strains characterized by distinctive neuropathological features. In particular, we compared astrocyte morphology and astrocyte-associated PrPSc deposition among strains in the same brain region, the mediodorsal thalamic nucleus (MDTN). Astrogliosis was detected to some extent in the MDTN of all analyzed voles. However, we observed variability in the morphological appearance of astrocytes depending on the strain. Astrocytes displayed variability in thickness and length of cellular processes and cellular body size, suggesting strain-specific phenotypes of reactive astrocytes. Remarkably, four out of six strains displayed astrocyte-associated PrPSc deposition, which correlated with the size of astrocytes. Overall, these data show that the heterogeneous reactivity of astrocytes in prion diseases depends at least in part on the infecting prion strains and their specific interaction with astrocytes.

Gerstmann-Sträussler-Scheinker Disease with F198S Mutation Induces Independent Tau and Prion Protein Pathologies in Bank Voles.

Gerstmann-Sträussler-Scheinker disease (GSS) is a rare genetic prion disease. A large GSS kindred linked to the serine-for-phenylalanine substitution at codon 198 of the prion protein gene (GSS-F198S) is characterized by conspicuous accumulation of prion protein (PrP)-amyloid deposits and neurofibrillary tangles. Recently, we demonstrated the transmissibility of GSS-F198S prions to bank vole carrying isoleucine at 109 PrP codon (BvI). Here we investigated: (i) the transmissibility of GSS-F198S prions to voles carrying methionine at codon 109 (BvM); (ii) the induction of hyperphosphorylated Tau (pTau) in two vole lines, and (iii) compared the phenotype of GSS-F198S-induced pTau with pTau induced in BvM following intracerebral inoculation of a familial Alzheimer's disease case carrying Presenilin 1 mutation (fAD-PS1). We did not detect prion transmission to BvM, despite the high susceptibility of BvI previously observed. Immunohistochemistry established the presence of induced pTau depositions in vole brains that were not affected by prions. Furthermore, the phenotype of pTau deposits in vole brains was similar in GSS-F198S and fAD-PS1. Overall, results suggest that, regardless of the cause of pTau deposition and its relationship with PrPSc in GSS-F198S human-affected brains, the two components possess their own seeding properties, and that pTau deposition is similarly induced by GSS-F198S and fAD-PS1.

Pelodera strongyloides in the critically endangered Apennine brown bear (Ursus arctos marsicanus).

Skin biopsies from 20 Apennine brown bears (Ursus arctos marsicanus), 17 of which displaying skin lesions, were investigated by histopathology. Different degrees of dermatitis characterized by folliculitis and furunculosis accompanied by epidermal hyperplasia and epidermal and follicular hyperkeratosis were detected. In the most severe lesions, the superimposition of traumatic wounds, probably self-induced by scratching, was observed. In 8 out of 17 (47.0%) affected bears, cross- and longitudinally-sectioned nematode larvae were present within the lumen of hair follicles, whose localization and morphological characteristics were consistent with Pelodera strongyloides. P. strongyloides is a free-living saprophytic nematode whose third-stage larvae can invade the skin causing pruritic dermatitis in several mammalian species. This is the first report of Pelodera infection in the brown bear. Although capable of causing primary dermatitis, the finding of Pelodera is not sufficient to conclude that it is the cause of the lesions observed in bears. Nevertheless, the high prevalence of the infection is indicative of a diffuse phenomenon that requires further specific investigations given the interest and conservational relevance of this relict bear population.