Mouse-adapted scrapie strains 139A and ME7 overcome species barrier to induce experimental scrapie in hamsters and changed their pathogenic features

BACKGROUND: Transmissible spongiform encephalopathy (TSE) diseases are known to be zoonotic diseases that can infect different kinds of animals. The transmissibility of TSE, like that of other infectious diseases, shows marked species barrier, either being unable to infect heterologous species or difficult to form transmission experimentally. The similarity of the amino acid sequences of PrP among species is believed to be one of the elements in controlling the transmission TSE interspecies. Other factors, such as prion strains and host's microenvironment, may also participate in the process. METHODS: Two mouse-adapted strains 139A and ME7 were cerebrally inoculated to Golden hamsters. Presences of scrapie associate fibril (SAF) and PrP(Sc )in brains of the infected animals were tested by TEM assays and Western blots dynamically during the incubation periods. The pathogenic features of the novel prions in hamsters, including electrophoretic patterns, glycosylating profiles, immunoreactivities, proteinase K-resistances and conformational stabilities were comparatively evaluated. TSE-related neuropathological changes were assayed by histological examinations. RESULTS: After long incubation times, mouse-adapted agents 139A and ME7 induced experimental scrapie in hamsters, respectively, showing obvious spongiform degeneration and PrP(Sc )deposits in brains, especially in cortex regions. SAF and PrP(Sc )in brains were observed much earlier than the onset of clinical symptoms. The molecular characteristics of the newly-formed PrP(Sc )in hamsters, 139A-ha and ME7-ha, were obviously distinct from the original mouse agents, however, greatly similar as that of a hamster-adapted scrapie strain 263 K. Although the incubation times and main disease signs of the hamsters of 139A-ha and ME7-ha were different, the pathogenic characteristics and neuropathological changes were highly similar. CONCLUSIONS: This finding concludes that mouse-adapted agents 139A and ME7 change their pathogenic characteristics during the transmission to hamsters. The novel prions in hamsters' brains obtain new molecular properties with hamster-specificity.