PrPSc detection in affected tissues and blood of mice infected with murine-adapted bovine spongiform encephalopathy strain 301C

The sensitivities of PrPSc detection methods, western blotting (WB), immunohistochemistry (IHC) and protein misfoldingcyclic amplification (PMCA) techniques were compared from brains, spleens and blood of mice challenged withPrPSc of murine-adapted BSE strain 301C. PrPSc was detected in the spleen from 30 dpi by IHC and at 60 dpi by WB.At 30 dpi, disease-specific signals of PrPSc was observed in only two follicles of a single spleen. PrPSc was detectedin spleen at 10 dpi with PMCA after 5 rounds of amplification. Clinical signs were obviously shown from 240 dpi,and coincided with first detection of PrPSc in brains by WB, IHC and PMCA after one round amplification. In addition,PrPSc was also detected in blood at 60, 180 and 240 dpi with PMCA after 5 rounds of amplification. The FDC-M1epitope, which appears in immature FDCs, and PrPSc were detected in follicles first at 30 dpi, whilst the FDC-M2epitope of mature FDCs was detected at 60 dpi. More FDC-M2 epitope and PrPSc were detected in follicles as diseaseprogressed. The CD21/35 epitope is expressed on both FDCs and germinal center B cells. The pattern of CD21/35expressing cells was similar to but less dominant than that of FDCs.