Phage antibody selection and molecular genetics characterization. In the upper part of the figure (panels A, B, C and D) the FACS binding profiles of the ETH-2 library and selected phage antibody populations with CCRF-CEM cells are shown after each round of biopanning selection. In the inserted boxes, the ELISA reactivity of the ETH-2 library (A') and selected phage antibody populations (B', C', D') with the rHaPrP are shown in parallel with the irrelevant phage antibody anti glucose oxidase and anti tetanus toxoid (A", B", C" and D"). Experiments were repeated at least twice and mean ± SD from representative experiments (triplicate samples) is shown. The cut-off value separating positive from negative sample was calculated as 3 standard deviation above the mean of the value obtained from irrelevant phage antibodies (0,085 OD). In the lower part of the figure, the nucleotide composition and the corresponding amino acid sequences in the CDR3 regions of the selected scFv antibodies MA3.B4 and MA3.G3 are shown. A schematic representation of the scFv antibody gene as M13 pIII fusion protein is also illustrated.