STRONGYLOIDES-STERCORALIS - PROTECTIVE IMMUNITY TO 3RD-STAGE LARVAE IN BALB CBYJ MICE/

A murine model system was developed to study the induction and mechani sm of protective immunity to L3 of Strongyloides stercoralis. L3 were implanted in BALB/cByJ mice in diffusion chambers constructed with 0.1 - or 2.0-mu m-pore-size membranes. Parasites survived equally well reg ardless of membrane type for 7 days, after which larval survival decre ased in diffusion chambers constructed with 2.0-mu m-pore-size membran es, which allowed host cells to enter. Survival of S. stercoralis L3 i n diffusion chambers implanted in mice was assayed after immunization with live, heat-killed, and homogenized L3. Optimal immunization was a chieved with 10,000 live L3, whereby immunized mice eliminated 97% of the larvae either contained within diffusion chambers or free within t he tissues of the mouse by 24 hr postinfection. Sera from immunized mi ce had elevated levels of IgGl, IgM, and IgA parasitic-specific antibo dy; IgM was the only antibody isotype that recognized surface antigens of L3. Larvae were not killed in immunized mice if contact between ho st cells and the parasites was prevented. In the peripheral blood and diffusion chamber fluid of immunized mice, eosinophil levels were sign ificantly higher when compared to the levels found in control mice. Th e rodent model developed in the present study has thus demonstrated th at virtually complete immunity can be induced to the L3 of S. stercora lis and that larval killing was found to be associated with the presen ce of both specific antibody and eosinophils. (C) 1995 Academic Press, Inc.