Antibody profiling in ultrasound normal individuals with positive serology for cystic echinococcosis.

Cystic echinococcosis is a zoonotic disease caused by the cestode parasite Echinococcus granulosus. In endemic regions, seropositive individuals to E. granulosus usually and markedly outnumber image-confirmed cases of cystic echinococcosis, suggesting that some parasite challenges derive in unsuccessful infection establishments. However, it is still unknown whether such parasite-specific antibodies in healthy individuals might play a role in resistance/susceptibility to the infection. Therefore, we have here analysed the profile of antibodies recognizing E. granulosus antigens in seropositive but ultrasound normal individuals, as well as in surgery-confirmed patients and healthy donors. Our results showed that ultrasound normal individuals exhibited low avidity IgG antibodies, as well as low levels of parasite-specific IgG1 and IgG4 antibodies. In addition, they displayed significant levels of specific IgE, and thus, they revealed a uniquely high IgE:IgG4 ratio. Moreover, high levels of parasite-specific IgM were detected in such individuals, which showed characteristics of natural cross-reacting antibodies. Therefore, our results indicate that ultrasound normal individuals but seropositive for E. granulosus antigens exhibit a distinctive antibody profile. In this regard, possible associations between their antiparasite antibodies and potential resistance mechanisms to cystic echinococcosis are discussed.