Recognition of schistosome glycolipids by immunoglobulin E: possible role in immunity

To investigate the role of antibody responses to (glyco)lipids in immunity to schistosome infection, lipids extracted from Schistosoma mansoni eggs and adult worms were fractionated, and the antibody isotype profile reactive to the fractionated lipids in a well-characterized S. haematobium-infected population was investigated. In tests of 10 plasma samples it was found that immunoglobulin G (IgG) reactivity was highest to the fraction containing ceramidepolyhexosides, whereas IgE reactivity was most prominent to both cerebroside- and ceramidepolyhexoside-containing fractions. The fraction containing ceramidepolyhexosides was then tested for reactivity with IgG subclasses and IgE in plasma samples from 66 S. haematobium-infected patients. Considering IgG4 and IgE, isotypes of particular interest in helminth infections, we found that both isotypes recognized egg (glyco)proteins in more than 90% of the infected subjects. However, in the case of glycolipids, IgE reactivity was much more prominent than IgG4 reactivity (found in 80 and 41% of the subjects, respectively). Furthermore, worm glycolipid-specific IgE prior to treatment of the subjects with praziquantel was negatively correlated with egg counts at 2 years posttreatment, indicating that IgE directed towards glycolipids could play an important role in resistance to reinfection.