Comparison Study on Clinical and Neuropathological Characteristics of Hamsters Inoculated With Scrapie Strain 263K in Different Challenging Pathways

Key words: 
• Transmissible spongiform encephalopathy /
• Scrapie /
• Strain 263K /
• PrPSc /
• Bioassay /
• Neuropathology /
• Inoculating pathways

Abstract: Objective To understand the infectious characteristics of a hamster-adapted scrapie strain 263K with five different routes of infection including intracerebral (i.c.), intraperitoneal (i.p.),intragastrical (i.g.), intracardiac and intramuscular (i. m.) approaches. Methods Hamsters were infected with crude- or fine-prepared brain extracts. The neuropathological changes, PrPSc deposits,and patterns of PK-resistant PrP were analyzed by HE stain, immunohistochemistry (IHC) assay and Western blot. Reactive gliosis and neuron loss were evaluated by glial fibrillary acidic protein (GFAP)and neuron specific enolase (NSE) specific IHC. Results The animals inoculated in i.m. and i.p.ways with crude PrPSc extracts showed clinical signs at the average incubation of 69.2+-2.8 and 65.5±3.9 days. Inoculation in i.c. and intracardiac ways with fine PrPSc extracts (0.00035 g) caused similar,but relative long incubation of around 90 days. Only oneout of eight hamsters challenged ini.g way with low dosage (0.01 g) became ill after a much longer incubation (185 d), while all animals (4/4)with high dosage (0.04 g) developed clinical signs 105 days postinfection. The most remarkable spongiform degeneration and PrPsc deposits were found in brain stem among the five challenge groups generally. The number of GFAP-positive astrocytes increased distinctly in brain stems in all infection groups, while the number of NSE-positive cells decreased significantly in cerebrum, except i.c. group. The patterns of PK-resistant PrP in brains were basically identical among the five infection routes. Conclusion Typical TSE could be induced in hamsters by inoculating strain 263K in the five infection ways. The incubation periods in bioassays depend on infective dosage, administrating pathway and preparation of PrPSc. The neuropathological changes and PrPSc deposits seem to be related with regions and inoculating pathways.