Evaluation of the antigenic similarities of adult-worm extracts from three Gnathostoma species, using sera from Mexican and Japanese patients with Gnathostoma infections.

The antigenic similarities of adult-worm extracts of Gnathostoma spinigerum, G. hispidum and G. doloresi, all of which are important food-borne parasites causing larva migrans in humans, were evaluated. The 40 sera used came from gnathostomiasis cases in Mexico, where G. binucleatum is endemic, or in Japan, where G. doloresi predominates. When used as the fixed antigens in microplate-ELISA, the adult-worm extracts from the three different species of Gnathostoma were found to have equal binding capacity to the Gnathostoma-specific IgG antibodies in the sera of the Mexican and Japanese patients. The correlation coefficients for the optical densities seen in the ELISA, between any two of the three Gnathostoma extracts, were all >0.900. The dose-response curves produced when four sera were tested, in the microplate-ELISA, against the three different Gnathostoma extracts were nearly identical, indicating that the antigens in each of the extracts had similar avidity. Furthermore, the results of competitive-inhibition ELISA indicated that the antigenic specificities of the three extracts were almost identical. An antigen of 40 kDa, which SDS-PAGE and immunoblot analysis revealed to be present in all three extracts, was recognized by the sera from the gnathostomiasis cases. When the sera were investigated by dot-blot ELISA, they also gave similar results whichever extract was used as the antigen source. It appears that, in the serodiagnosis of gnathostomiasis by microplate- or dot-ELISA, each of the three adult-worm extracts would be equally useful, regardless of the causative species of Gnathostoma.