Rapid Typing of Transmissible Spongiform Encephalopathy Strains with Differential ELISA
Figure 2. Determination of the A/A’ ratio. A dilution series was assayed for each analyzed sample to determine the optimal range that would permit precise determination of the A/A′ratio (absorbance ranging from 0.5 to 2.5 absorbance units in A reagent). A) A/A′ratio is close to 1 for PK-resistant prion protein (PrPres) associated with classic scrapie strains (manual protocol, see Experimental Procedures) and B) close to 10 for experimental ovine bovine spongiform encephalopathy (BSE)–associated PrPres. C) To minimize interassay variations, the ratio obtained for each sample is thus normalized by dividing by the ratio obtained for the ovine BSE sample.