| Research Abstract |
At first, we attempt to clarify the organ distribution of human and murine protease-resistant prion protein in Creutzfeldt-Jakob Disease (CJD), and to measure the concentration of abnormal Prion Protein (PrP) using semi-quantitative Western blot analysis. Human PrP was restricted to the central nervous system, whereas murine PrP was present in the central nervous system and in the lymphoreticular system at the end stage of CJD. PrP concentration in the central nervous system was almost identical to that of humans. The minimum wet weight of an organ with a positive reaction was 0.3 mg for brain, 1 to 3 mg for spleen, 3 mg for spinal cord, 3 mg for lymph node, 10 mg for thymus and 10 to 30 mg for intestine of the CJD-infected mice. There were no immunoreactions in purified PrP fractions form 300 mg of liver, lung or kidney of CJD-infected mice, nor from 300 mg of spleen, lymph node, liver or peripheral nervous system of humans. Within the limits of our method, the distribution of murine
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PrP differed from that of human PrP. Although the immunological detection of PrP does have limits of sensitivity, PrP concentration did correlate with infectivity titers in scrapie infected or CJD-infected mice.
Second, we examined Fukuoka-1 and Fukuoka-2 mouse-adapted CJD strains. Mice infected with Fukuoka-2 strain have a higher incidence of kuru plaques, a higher concentration of PrP, and a higher infectivity titer than do mice with the Fukuoka-1 strain. Thus, it must be kept in mind that there is a difference in the strain of the infectious agent in murine CJD.
Third, to demonstrate that PrP is a component of kuru plaque cores, we fractionated and sequenced kuru plaques core derived peptides, following digestion with Achromobacter lyticus protease I. We identified 3 PrP-derived peptides by reverse-phase high performance liquid chromatography and found a fragment of digests derived from a missense variant of PrP (102 Leu). Variant PrP was also present in the prion rod fraction in patients with Gerstmann-Straussler syndrome. From the data of amino acid sequence, we could not identify the N-terminal sequence because of heterogeneous N-termini. To elucidate whether N-terminal sequence of PrP is related to amyloid formation in vivo, we prepared synthetic N-terminal peptide. Anti-N-terminal antibody immunolabeled kuru plaques positively. Less
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