Analysis on the reactivity of five subunits of antigen B family in serodiagnosis of echinococcosis.

In this study, the reactivity and differences of five subunits of echinococcus antigen B (AgB) family, recognizing specific antibodies in echinococcosis patient serum, were analyzed. Eight recombinant subunit antigens from Echinococcus granulosus (EgAgB1-EgAgB4) and Echinococcus multilocularis (EmAgB1-EmAgB3 and EmAgB5) were tested by ELISA using a panel of 243 serum samples collected from cystic echinococcosis (CE), alveolar echinococcosis (AE), cysticercosis (CC) patients and clinically normal individuals (NH). The results showed that the diagnostic sensitivity of the subunits for CE sera were 83.06%, 62.90%, 29.03%, 75.81% and 41.13%, and the specificities were 73.95%, 72.27%, 76.47%, 73.11% and 85.71%, respectively. The reactivity of three paralogous subunits, EgAgB1, EgAgB2 and EgAgB3 from E. granulosus and EmAgB1, EmAgB2 and EmAgB3 from E. multilocularis were compared by serological assay. All of the orthologous subunits showed no statistical difference (P>0.05) in detecting CE and AE sera; it revealed that the reactive epitopes may be similar between the orthologous subunits. In a total of 124 CE sera, the positive recognition rate by EgAgB1 was the highest (103/124), yet cocktail subunit antigens may detect even more positives from 100/124 to 112/124 using different subunit combinations. IgG4 subclass was the predominant antibody in reacting with subunit antigens. To conclude, the epitopes of orthologous AgB subunits from E. granulosus and E. multilocularis that recognize specific antibodies may be similar. The paralogous subunits EgAgB1, EgAgB2 and EgAgB4 were the main reactive subunit in sera detection and may have utility as echinococcosis diagnostics, with EgAgB1 possessing the greatest potential. Cocktail subunits may improve the positive detection rate.