PERITONEAL-MACROPHAGES FROM C57BL 6 MICE ORALLY IMMUNIZED WITH TOXOPLASMA-GONDII ANTIGENS IN ASSOCIATION WITH CHOLERA-TOXIN POSSESS AN ENHANCED ABILITY TO INHIBIT PARASITE MULTIPLICATION/

Gamma-interferon (IFN-gamma) has been reported robe a major mediator o f resistance to toxoplasma infection, mainly through macrophage activa tion. Cholera toxin used as oral adjuvant induces enhanced protection. Following oral immunization of C57BL/6 mice with a Toxoplasma gondii sonicate (TSo), in association with either cholera toxin (CT) or its B subunit (CTB), the ability of primed sensitized peritoneal macrophage s (PM phi) to prevent T. gondii intracellular proliferation in vitro w as examined both with and without rIFN-gamma activation. Under these c onditions, the inhibition of T. gondii multiplication was greatly enha nced in PM phi from mice immunized with a TSo and CT as an oral adjuva nt. In contrast, PM phi from mice immunized with a TSo in association with CTB showed a decrease in their microbiostatic activity towards T. gondii. This negative effect on IFN-gamma-treated PM phi was cancelle d out by the addition of a small amount of CT in association with TSo and CTB in the immunization regimen. These data suggest that CT could act as an oral adjuvant in vaccination against toxoplasmosis by increa sing the microbiostatic activity of M phi activated with IFN-gamma. Fu rther studies, using intestinal effector cells such as enterocytes, ar e needed to confirm the value of CT for enhancing this major mechanism of protection against T. gondii infection.