Echinococcus granulosus human infection stimulates low avidity anticarbohydrate IgG2 and high avidity antipeptide IgG4 antibodies.

Total IgG and IgG subclasses recognizing carbohydrate and peptidic epitopes from native and periodate treated partially purified hydatid cyst fluid (ppHCFA) and protoscolex somatic antigens (PSA) were tested by ELISA in hydatid patients sera. Binding of the major cross-reactive antiphosphorylcholine antibodies was inhibited with free reagent. A predominant anticarbohydrate antibody response against ppHCFA and PSA is shown. Although the main contributing IgG subclass to the antipeptide response against both antigens was IgG4, IgG1 also significantly contributed to the anti-PSA peptidic epitopes response. Western blot showed that IgG1 antibodies strongly recognized in ppHCFA a periodate susceptible 38 kDa antigen. The IgG4 antibodies mainly recognized the periodate-resistant 12, 16 and 24 kDa antigens. In addition, IgG2 antibodies recognized three strongly periodate-susceptible broad bands (116, 55 and 24 kDa antigens). PSA-specific IgG1 and IgG4 antibodies showed similar patterns of antigen recognition as well as no significant reduction of reactivity after periodate treatment while the IgG2 antibody recognition was strongly affected by this treatment. Furthermore, IgG2 showed significantly lower avidities than IgG1 and IgG4 antibodies recognizing both antigens. In conclusion, hydatid patients showed an enhanced production of low avidity anticarbohydrate IgG2 as well as high avidity antipeptide IgG4 antibodies.