Characterization of antigen B subunit 2 (AgB2) gene polymorphism in sheep isolates of Echinococcus granulosus sensu lato and effect on serologic response.

Cystic Echinococcosis (CE) is one of the most common helminth infections in many parts of the world. Antigen B (AgB) is a key molecule secreted by both the germinal membrane and protoscoleces during the larval stages of Echinococcus granulosus. Characterizing polymorphisms in the genes encoding AgB can improve the interpretation of serological diagnostic tests. This study aimed to determine the polymorphism in the AgB subunit 2 (AgB2) gene in sheep isolates of E. granulosus sensu lato and to investigate its effect on the serological response. Germinal membranes from 41 sheep hydatid cysts and corresponding blood serum samples were collected from slaughterhouses in Elazig and Bingol provinces of Türkiye. Total genomic DNA was isolated, and PCR amplification of the AgB2 gene region was followed by DNA sequencing to evaluate genetic diversity. Western Blot (WB) analysis was performed using partially purified cyst fluid antigen rich in AgB. Sequence analysis revealed that the 663 bp AgB2 gene region exhibited high polymorphism. A total of 33 polymorphic sequences were identified and classified into 10 different haplotypes (AgB2.Hap_01 to AgB2.Hap_10). Among these, 31 (93.9 %) samples were WB-positive, while 2 (6.1 %) were negative. The WB test demonstrated a sensitivity of 80.4 % and a specificity of 100 %. These results suggest a relationship between the polymorphism in the AgB2 gene and variations in the serological response.