Effect of cellular components or detergent present in the gradient top fractions on infectivity of the LA21K PK-resistant PrP^Sc–richest fractions.

LA21K PK-resistant PrP^Sc-richest fractions 11 to 13 (fr11–13) were mixed together and incubated (vol∶vol) with either the upper fractions 1 to 3 (fr1–3) of a gradient made with uninfected tg338 mouse brain (NI) or with dodecyl maltoside (DDM) at 2% (wt/vol.) final concentration. The specific influence of sarkosyl was not tested since the gradients were prepared in a solution containing this detergent (see methods). The resulting mixture was inoculated to recipient mice. Their relative infectious titer was estimated by an incubation time bioassay, and compared to that of the fractions 1 to 3 of the same gradient pooled and diluted in 5% glucose (vol∶vol). The infectious titers are expressed as relative infectious doses as in Figure 3.