Abstract: Objective To clone the subunits of AgB antigen gene family of Echinococcus granulosus（Eg） and Echinococcus multilocularis （Em）, analyze the gene sequences by bioinformatics methods, and predict the potential antigen epitopes. Methods Specific primers were designed based on the reference sequences from GenBank database. Total DNA was extracted from E. granulosus and E. multilocularis, which collected from the endemic areas of Xinjiang, Gansu and Sichuan. The PCR products were cloned into TA vector for sequencing. The online bioinformatics systems such as Bioedit software, Blastn, NPS@ and IEDB were used for the analysis. Results A total of five AgB gene subunits were cloned from E. granulosus and E. multilocularis, respectively, and identified by sequencing. Sequence homology analysis indicated that EmAgB subunits were highly conserved, while the EgAgB subunits were variable. Sequence alignment of AgB subunit genes from E. granulosus and E. multilocularis showed that the identity ranged from 87.69% to 100%. Three major types of secondary structure in the AgB subunits were alpha helix, extended strand, and random coil. Compared with other subunits, the higher percentages of random coil were found in AgB1, AgB2 and AgB4. Ten epitope areas were predicted from the five AgB subunits which were located in AgB1: 1-7 and 21-27, AgB2: 1-7 and 29-36, AgB3: 1-11 and 18-28, AgB4: 1-13, 27-37 and 39-60, AgB5: 1-11, repectively. Conclusion The majority of epitopes in EgAgB and EmAgB subunits have the same or similar sequences. Ten predicted epitopes are mainly located at the N-terminal sequences. Among the five subunits, AgB1, AgB2 and AgB4 display higher antigenicity.

Key words: Echinococcus granulosus, Echinococcus multilocularis, AgB gene family, Antigen subunits, Gene cloning, Epitope prediction