Lacto-N-fucopentaose III (Lewis x), a target of the antibody response in mice vaccinated with irradiated cercariae of Schistosoma mansoni.

Carbohydrates on soluble egg antigens are major epitopes for the antibody responses of patients and mice infected with Schistosoma mansoni. Recently, protective sera of mice vaccinated with irradiated cercariae were shown to recognize carbohydrate epitopes on schistosomal glutathione S-transferase. The present study demonstrates that carbohydrate epitopes are major targets of sera from C57BL/6J and CBA/J mice vaccinated with 15- or 50-kilorad-irradiated cercariae of S. mansoni. Antibody titers to carbohydrate epitopes increased with the number of vaccinations and were considerably higher in C57BL/6J mice than in CBA/J mice. The specificity of this anticarbohydrate response was determined by measuring antibody binding to defined oligosaccharide residues known to be present on the parasite. A predominant target of the humoral anticarbohydrate response of vaccinated mice was lacto-N-fucopentaose III, a molecule relevant for cell trafficking. We observed no binding to its nonfucosylated homolog, lacto-N-neotetraose, or to oligosaccharides present on keyhole limpet hemocyanin. The strongest antibody response to lacto-N-fucopentaose III was observed for C57BL/6J and CBA/J mice repeatedly vaccinated with 15-kilorad-irradiated cercariae, which also achieve the highest levels of protection. Immunoglobulin M was the predominant antibody class binding to lacto-N-fucopentaose III. We conclude that in the irradiated-cercariae vaccine model, C57BL/6J and CBA/J mice produce anticarbohydrate antibodies against various stages of S. mansoni and that the oligosaccharide lacto-N-fucopentaose III is one target of this response. Lacto-N-fucopentaose III and its specific antibodies may profoundly affect host resistance and parasite homing.