Genetic Variability of Antigen B2 of Human, Sheep, Goats, Ca-mel and Cattle Isolates of Echinococcus granulosus in Iran

Antigen B (AgB) is frequently used for immuno-diagnosis of hu­man cystic echinococcosis (CE). Echinococcus granulosus AgBs show a high degree of genetic variability in different hosts or in different CE endemic areas. The present study aimed to evaluate the genetic polymorphisms of encoding antigen B2 gene (AgB2) among different Iranian isolates of E. granulosus. A total of 50 CE isolates were collected from human, sheep, cattle, goat and camels, 10 isolates from each intermediate host of E. granulosus. Total genomic DNA from either protoscolices or germinal layer was extracted from each cyst and PCR-RFLP followed by DNA sequencing was used to evaluate sequence variation and polymorphism of AgB2 in the isolates. After the PCR amplification, using AgB2 primers, an almost 400 bp band was amplified in all of the isolates. The PCR products were digested with Alu1 re­striction endonuclease. After restriction enzyme digestion with Alu1‚ sheep and human isolates gave a similar pattern of RFLP with the gene size of approximately 140 and 240bp and camel and goat isolates gave a similar pattern, but different from sheep and human, with the gene size of approximately 150 and 250bp. Se­quence analysis showed the most genetic similarity of AgB2 between human and sheep isolates. Findings of this study revealed the differences in the sequences of AgB2 within and between the Iranian isolates of E. granulosus. These differences may affect the performance of any diagnostic test which uses AgB.