A simplified method for the fractionation of Gnathostoma-specific antigens for serodiagnosis of human gnathostomosis.

Specific immunoreactive components present in crude somatic extract and in excretory-secretory (ES) products of Gnathostoma spinigerum advanced third-stage larvae (L3) were identified by Western blotting and their diagnostic potential evaluated by indirect ELISA. Although both crude antigen preparations were highly complex, the ES antigen gave a more satisfactory diagnostic result. Most G. spinigerum specific components present in the somatic and ES preparations had molecular weights below 29 kD and were not glycosylated, judging from the concanavalin A staining pattern. Specific diagnostic antigens were prepared by subjecting the crude preparations to SDS-PAGE. Low molecular weight components were identified and electroeluted from the gel. Excess SDS was removed by the use of an ion retardation resin. The antigens obtained by this relatively simple procedure were found to be highly specific for G. spinigerum. Sensitivity, specificity, and positive and negative predictive values for the assay using the fractionated somatic antigen were 100%.