Comparative analysis of two different subunits of antigen B from Echinococcus granulosus: gene sequences, expression in Escherichia coli and serological evaluation

Two different Echinococcus granulosus antigen B subunits (AgB8/1 and AgB8/2 ) were characterized and the structure of the genes encoding these two prot eins were compared. DNA sequences were expressed in Escherichia coli and th e antigens' diagnostic value was then assessed. The genomic sequence of AgB 8/1 has a 92 bp intron in the position corresponding to amino acid 16; the AgB8/2 genomic sequence presents a 68 bp intron in the position correspondi ng to amino acid 20, Both introns are located between the putative N-termin al hydrophobic sequence and the secreted peptide. A comparison between the AgB8/1 and AgB8/2 nucleotide sequences showed a 53.5% identity among exons and a 50% identity between introns. According to the molecular diversity an alysis, the elapsed time since both genes shared a common ancestor would be around 4.2 x 10(7) years. When the native AgB and the two recombinant anti gens (rAgB8/1 and rAgB8/2) were tested in an anti-IgG ELISA, the sensitivit y of the native antigen B was 77.41% and its specificity was 81.9%, while r AgB8/1 showed 54.84% of sensitivity and 80.17% of specificity and rAg138/2 had an 83.87% sensitivity and a 98.28% specificity. Statistical analysis co nfirms that rAgB8/2 has a better performance than rAgB8/1 and native AgB in ELISA. (C) 2000 Elsevier Science B.V. All rights reserved.