Molecular characterization and serodiagnostic evaluation of the Echinococcus ortleppi recombinant glutaredoxin 1 protein for cystic echinococcosis in buffalo (Bubalus bubalis)

Cystic echinococcosis (CE), caused by the metacestode of Echinococcus granulosus sensu lato (s.l.), adversely affects the physiology of the vital organs in which they grow. Condemnation of meat causes substantial economic loss to the livestock industry. Conventionally the infection is detected by necropsy as serological diagnosis of the infection in livestock is ambiguous. Identification of specific diagnostic antigens would be a substitute for the cyst fluid antigens which lack adequate diagnostic sensitivity and specificity. BLAST analysis supported by the negligible pairwise nucleotide distance of the 389 nt COX1, 489 nt NAD1, and 425 nt ITS1 with the related sequences of E. ortleppi ascertained the association of E. ortleppi with CE in buffaloes. Given the extensive distribution of glutaredoxin 1 in every developmental stage of Echinococcus granulosus s.l that makes it an ideal serodiagnostic antigen for CE, we expressed the 14 kDa E. ortleppi glutaredoxin 1 (rEoGrx1) protein in E. coli BL21 (DE3) and tested a total of 225 sera samples, including 126 sera samples from the necropsy-positive buffalo, by the rEoGrx1 IgG-ELISA. The ELISA could detect a total of 82/126 sera samples as positive. The diagnostic sensitivity and specificity of the rEoGrx1 IgG-ELISA were 65.1 % and 51.5 %, respectively. The protein showed serological cross-reaction against Fasciola gigantica, Toxoplasma gondii, and Sarcocystis sp. The in silico bioinformatics analysis of the E. ortleppi, F. gigantica, and T. gondii glutaredoxin sequences revealed fully conserved amino acids at positions 11 and 21, the substitution of conserved amino acids at positions 14 and 6, and semi-conserved substitutions at positions 3 and 4, respectively. The findings partly explain the molecular basis of the serological cross-reactivity of the protein.