A microarray platform was used for screening in silico selected peptides for reactivity with patients' sera. The low-density peptide microarray (Alta Bioscience, University of Birmingham, UK) featured two blocks, each containing 45 Echinococcus peptide spots, a spotting control allowing positioning of grid for analysis (unrelated, TAMRA-labeled peptide), a control for serological detection (human IgG) and a blank (spotting solution). All microarray work was done at room temperature. Microarray slides were blocked for one hour in assay buffer (16PBS pH 7.4, 0.05% Tween20, 3% milk powder). Individual human sera or serum pools were diluted 1:50 in assay buffer and incubated for two hours in a moist chamber. Slides were washed for 365 minutes in assay buffer and incubated for one hour with a 1:100 dilution of Cy5-labeled goat anti-human IgG (H+L) secondary antibody (Jackson ImmunoResearch Laboratories product number 109-175-088). Slides were washed for 365 min- ELISA 96-well plates (NUNC Immobilizer Streptavidin) were prewashed three times using an ELISA plate washer (deionized H 2 O, 0.05% Tween20) and coated overnight at 4uC with 100 ml/well of synthetic peptide diluted to 2 mg ml 21 in PBS pH 7.4. All following steps were carried out at room temperature. After washing, the plates were blocked for one hour with 150 ml/well of assay buffer (3% milk in PBS pH 7.4, 0.05% Tween20, 0.5 mM biotin). The plates were washed and incubated for one hour with human sera diluted 1:200 in assay buffer (100 ml/well). Alkalinephosphatase-conjugated goat anti-human IgG antibodies (Sigma product number A 3187) 1:1000 in assay buffer were used as secondary antibodies. After washing, 100 ml of conjugate dilution was added to each well and incubated for one hour, followed by a final wash. Wells were then incubated for 15 minutes with 100 ml of p-nitrophenyl phosphate (Sigma product number N 4645) at a concentration of 1 mg ml 21 in substrate buffer (13.2 mM Na 2 CO 3 , 35 mM NaHCO 3 , 1mM MgCl 2 66H 2 O, pH 9.6). Absorbance values (A 405nm ) were measured at 405 nm in a Tecan Sunrise microplate absorbance reader. All serum samples were tested in duplicates. The two values were averaged and blankcorrected. For distinguishing between positive and negative ELISA test results, 50 sera from healthy blood donors living in Switzerland were tested. The cut-off value was determined by the mean of the blood donor samples plus two standard deviations. Sensitivity and specificity of the single peptide candidates were calculated using test results from confirmed echinococcosis patients as true positives (TP). Blood donors and individuals infected by other helminths were taken as true negatives (TN). The working characteristics of the peptide antigens were explored by receiver-operating characteristics (ROC) plot analysis (Analyse-It, version 2.21).