Figure 2.

(A) Excretion of PrP^Sc and rPrP^Sc in the feces of Syrian hamsters orally infected with Sc237 prions. Each Syrian hamster consumed half a brain of an Sc237-infected Syrian hamster. Feces were collected daily from 0 to 20 days, then every 3–7 days until Syrian hamsters showed symptoms of disease at 116 days. The concentration of PrP isoforms in fecal extracts were measured by CDI using recFab HuM D18 to capture and Eu-labeled mAb 3F4 to detect SHaPrP. Total PrP^Sc (circles) was measured after PTA precipitation without protease treatment; rPrP^Sc (squares) was measured after PK digestion and PTA precipitation as in Fig. 1. The dashed lines indicate the cut-off value calculated as mean+3*SD from age-matched, control feces. (B) Levels of PrP^Sc in the brains of individual, symptomatic Tg7 mice inoculated intracerebrally with irradiated fecal homogenates. The feces were collected at 1, 2, 8, 22, 43, 64, 85, and 106 days postinfection from orally infected (p.o.), intraperitoneally inoculated (i.p.), or intracerebrally inoculated (i.c.) Syrian hamsters. As a control (c), age-matched, uninoculated brains were evaluated. The dashed line indicates the cut-off value calculated as mean+3*SD from age-matched, control brain samples. For both panels, each sample was tested two to four times and the results for individual samples are expressed as the mean ± S.D. The concentration of PrP^Sc was calculated from the (D–N) differences of the time-resolved fluorescence measured in counts per minute (cpm) [39, 56]. The concentration of rPrP^Sc is directly proportional to the (D–N) value and was calculated from the published formula [39].