Subclass-specific serological reactivity and IgG4-specific antigen recognition in human echinococcosis.

Immunoglobulin (Ig) subclass-specific antibody responses and isotype-specific recognition of E. multilocularis (Em) and E. granulosus (Eg) antigens (Ag) were evaluated in both alveolar echinococcosis (AE) and cystic echinococcosis (CE). AE patients were divided into 3 groups by clinical and therapeutic criteria according to their actual state of infection, i.e. elimination of parasite, and regression or progression of disease, CE patients were either before or after surgery, of in continuous chemotherapy due to parasite persistence. Total IgE was highly elevated in progressive AE cases (7/11), but not in the cases with eliminated infection or regression. In AE patients with active disease, EmAg-specific IgE, total IgG, IgG1, IgG2 and IgG4 were particularly high. Similarly, in 9 of 30 CE patients, total IgE was raised above reference values, indicating progressive disease. CE patients" sera antibody cross-reacted with crude EmAg, and detectable Ig levels of the same isotype were also measured by ELISA. In both AE and CE, parasite-specific antigen recognition was dominated by IgG1 and IgG4. In AE patients with progressive disease, IgG4 distinctively recognized low molecular weight EmAg of Ar 26 kD, 18 kD, 16 kD and 12 kD. As prominent IgG4 and IgE responses develop with chronic helminth infections only, these serological parameters may indicate successful parasite infestation and severe outcome of disease. In summary, analyses of immunoglobulin isotype responses in AE patients by ELISA in combination with immunoblotting are a useful approach for post-treatment follow-up of patients at risk of developing recrudescent disease.