Strongyloides stercoralis: high worm population density leads to autoinfection in the jird (Meriones unguiculatus).

At 28 days post-infection autoinfective third-stage larvae (L3a) of Strongyloides stercoralis occurred in jirds infected with 10,000 infective third-stage (L3i). Previously in the jird model of strongyloidiasis, autoinfection had been seen in immunologically immature or immunosuppressed jirds only. The heavily infected jirds described herein had a strong anti-L3i immune response at the same time the living L3a were found in their tissues.

Plasmodium: immunization with carboxyl-terminal regions of MSP-1 protects against homologous but not heterologous blood-stage parasite challenge.

A leading candidate for a vaccine targeted at the erythrocytic stages of plasmodial parasite development is the merozoite surface protein-1 (MSP-1). We have previously shown that the carboxyl-terminal region of MSP-1 derived from Plasmodium yoelii yoelii 17XL, expressed as a fusion protein with glutathione S-transferase (GST-PYC2), can immunize mice against an otherwise lethal homologous challenge infection. This protection has been shown to be predominantly mediated by antibodies.

Fc receptors are not required for antibody-mediated protection against lethal malaria challenge in a mouse model.

The mechanisms by which Abs mediate protection during blood-stage malaria infections is controversial, with some evidence pointing to the direct effect of Abs on parasite invasion and growth, while other studies suggest that Abs act in cooperation with monocytes to achieve parasite inhibition. To determine whether the effector phase of protection in vivo to the rodent parasite Plasmodium yoelii yoelii requires Fc receptor bearing cells, we passively transferred immune sera into FcR gamma-chain knockout mice. Inflammatory macrophages from these knockout mice were unable to mediate phagocytosis or Ab-dependent cell-mediated cytotoxicity (ADCC) through Fc gamma RI, Fc gamma RII, or Fc gamma RIII.

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.

Chronicity in Strongyloides stercoralis infections: dichotomy of the protective immune response to infective and autoinfective larvae in a mouse model.

Strongyloidiasis is an intestinal disease that can last for decades due to the occurrence of autoinfective larvae (L3a) in an infected person, which contribute to the maintenance of the population of adult worms in the intestine. The goal of the present study was to determine if L3a are susceptible to the protective immunity that targets the infective stage of the worm, the third-stage larvae (L3). Mice immunized and challenged with Strongyloides stercoralis L3 kill more than 90% of challenge larvae contained within diffusion chambers.