Genetic Variability of Antigen B8/1 among Echinococcus granulosus Isolates from Human, Cattle, and Sheep in Fars Province, Southern Iran

Background: Cystic echinococcosis (CE), known as hydatid cyst, is a zoonotic parasitic infection caused by the larval stage of Echinococcus granulosus (E. granulosus). Antigen B, the major component of hydatid cyst fluid, is encoded by members of a multigene family. The present study aimed to evaluate the genetic diversity of the gene encoding antigen B8/1 (EgAgB8/1) among the main intermediate hosts of E. granulosus. Methods: Twenty-eight hydatid cyst isolates (10 sheep, 9 human, and 9 cattle) were collected in Fars province, Iran. DNA was extracted from each cyst and PCR, followed by DNA sequencing was used to identify potential EgAgB8/1 sequence variation and polymorphism. A phylogenetic tree was constructed using MEGA 7.0 software and the maximum likelihood method. Results: Using EgAgB8/1 primers, an approximately 315 bp band was amplified from all the isolates. The PCR products were sequenced, and the sequences were deposited in GenBank (accession numbers, KY709266-KY709293). The polymorphism variation among the isolates was 0.0, while intra-species variation within the isolates and related sequences in GenBank was 0.5-1%. Analysis of the phylogenetic tree revealed that the isolates from humans, sheep, and cattle all cluster in one group and are homologous to the EgAgB8/1 M1 allele. Conclusions: Findings of this study revealed close similarity between the EgAgB8/1 of human, sheep, and cattle E. granulosus isolates. However, differences were found between the EgAgB8/1 sequences in our study and those reported from other CE endemic areas. Whether such similarities and differences exist in other subunits AgB subunits require further study.