Western blot analysis of reactivity to larval and adult Strongyloides ratti antigens in mice.

Mice were infected once, twice or many times with Strongyloides ratti infective larvae, and the parasite was allowed to complete its development. Other mice were infected many times with either infective larvae only, by aborting the infection with cambendazole, or with adult worms transferred by intra-oesophageal intubation. Sera from these animals were analysed by immunoblotting against SDS-PAGE separations of larval and adult worm water-soluble, deoxycholate-soluble, sodium dodecyl sulphate-soluble and excretory/secretory antigens. Minimal antibody responses were observed after primary and secondary infections. Mice exposed to multiple complete infections reacted strongly to both larval and adult antigens but greater responses were observed against the larval preparations. Stage-specific effects were noted in mice infected with larvae only or adult worms only. Mice exposed only to larvae reacted with larval antigens and to a minor degree to somatic adult worm antigens while those mice which were exposed only to adult worms failed to react with any of the antigen preparations. Some cross-reactions were found, however, as mice infected only with larvae displayed strong reactions against both larval and adult excretory/secretory products. These data demonstrate differences in sero-reactivity to infective larvae and adult worms and suggest that humoral immunity is induced by larvae migrating through the tissues and not by adult worms in the gut.