For defining optimal peptide length, we designed extended variants of the 8 most reactive candidates from the microarray. The length of extended peptides ranged between 40 and 47 residues (table 1). Modifications at the N-and C-terminus were identical to those of the microarray peptides. The extension of peptides was chosen to increase alpha-helical coiled-coil stability or to combine epitopes from two single peptides. To target these improved peptides to E. multilocularis diagnosis, we chose the E. multilocularis sequences for designing longer peptides. Sequences derived from antigen B8/1 (accession number BAC77657) and antigen B8/2 (accession number BAD89809). To our knowledge, these were the first synthetic peptides from any E. multilocularis antigen B sequence that were serologically evaluated. Alignments of homologous antigen B8/1-and antigen B8/2-sequences of the two Echinococcus species are shown in figures S1 and S2, respectively. Antigen B8/1sequences of E. granulosus and E. multilocularis showed 86% identity and antigen B8/2-sequences 93% identity. Peptide longD8-9 coincided with the region of a previously published E. granulosus epitope EVKYFFER [29] , but differed from another published synthetic peptide p176 [30] : p176 spans the N-terminal region of antigen B8/1 (amino acids 17-54), while longD8-9 covered the central part of the protein (amino acids . Within the overlap of 26 amino acids, three amino acids differed.