Successful transmission of Creutzfeldt-Jakob disease from human to mouse verified by prion protein accumulation in mouse brains

The accumulation of prion protein (PrP) was revealed in the brains of mice inoculated with the brain homogenate from seven patients with Creutzfeldt-Jakob disease (CJD) by immunohistochemistry using hydrolytic autoclaving. It was not found in the brains of mice inoculated with material from either two patients with Gerstmann-Sträussler syndrome or two with other dementing illnesses. PrP accumulation took the forms of diffuse neuropil accumulation in the gray matter and plaque-like accumulation in the white matter and was observed in particular areas in the supratentorial structure. Its distribution was narrower than that in the brains of mice infected with a mouse-adapted CJD strain. PrP accumulation was found not only in all histopathologically positive mice, but also in some histopathologically negative mice. In all groups of mice inoculated with the material from each CJD patient, the percentage of mice with PrP accumulation was equal to or exceeded that of mice with the histopathological findings. PrP immunohistochemistry using formic acid pretreatment stained such plaque-like accumulation less intensely than that using hydrolytic autoclaving and did not stain diffuse neuropil accumulation. Therefore, PrP accumulation which can be revealed in the brains of first-passage CJD mice by this new immunohistochemical method may be the most sensitive hallmark of successful transmission.