Strongyloides stercoralis Host-Adapted Third-Stage Larvae Are the Target of Eosinophil-Associated Immune-Mediated Killing in Mice

Host-adapted, transformed, Strongyloides stercoralis third-stage larvae (L3+) were previously found to be antigenically different from free-living, infective, third-stage larvae (L3). These antigenic differences were reproduced by transformation of free-living larvae in tissue culture medium at 37 C over 24 hr. Transformed L3 of both derivations were given as challenge infections in diffusion chambers to naive mice and mice immunized with S. stercoralis L3. Within 12 hr, the challenge infections were killed regardless of whether the L3+were generated in vitro or in vivo. Eosinophils, previously found to be important in the immune response to S. stercoralis larvae, were recruited into the L3+microenvironment within 12 hr of challenge infection in immune mice, which supports the previously proposed mechanisms of S. stercoralis larval killing. Thus, S. stercoralis L3+appear to be targets of the immune response in mice instead of being involved in immune evasion.