Sequential appearance and accumulation of pathognomonic markers in the central nervous system of hamsters orally infected with scrapie.

Both infectivity and TSE-specific amyloid protein (also referred to as protease resistant- or prion protein, PrP) are pathognomonic markers for transmissible spongiform encephalopathies (TSE). This paper presents a new densitometric method for the quantification of TSE-specific amyloid protein and its application to studying the pathogenesis of scrapie in Syrian hamsters after infection with scrapie strain 263K. A first study established a close correlation between infectivity and TSE-specific amyloid protein with a doubling time of 2-2.6 days in the brain and cervical spinal cord for both markers. The ratio of infectivity and TSE-specific amyloid protein was relatively constant at a mean value of about 10(6) protein molecules per infectious unit during the course of infection. A subsequent study addressed the temporal-spatial spread of infection in the central nervous system by tracing the accumulation of the pathological protein. The pathogenetic process was first detected in the spinal cord between vertebrae T4 and T9, and then showed an anterograde and retrograde spread with a rate of 0.8-1.0 mm/day. There were also some indications for a possible alternative route of spread of infection from the periphery to the brain, other than via the spinal cord. Involvement of the spleen did not appear essential for the early pathogenesis in hamsters orally infected with the 263K strain of scrapie.