Characterization of IL-12 and TNF-α inducing activities in toxoplasma gondil as protein-associated glycolipids

Toxoplasma gondii Is an intracellular protozoan parasite which induces a strong cell-mediated immunity by triggering production of the monokines IL-12, TNF-α, and IL-1-ß early in Infection. We have been characterizing the tachyzoite molecules responsible for the stimulation of two of these mediators, IL-12 and TNF-α using thyoglycolate elicited peritoneal macrophages from C3H/HeJ mice as the responding cells. The monokine inducing factors are found in both soluble and membrane form in the parasite and are heat stable (5′ at 100°C) but sensitive to periodate oxidation. The soluble IL-12 stimulating activity is also partially sensitive to both protease and lipase treatments while the equivalent TNF-α inducing activity is largely refractory to these enzymes. Significantly, while both activities remain in the aquaeous phase when extracted with lipid solvents, they partition into the organic phase after proteolytic digestion. These findings argue that the TNF-α and IL-12 inducing factors are peptide linked glycolipids which differ in their dependence on associated protein. They therefore resemble the glycollpid anchor structures in the malaria parasite which mediate TNF-α production and fever. Further purification of the bioactive T. gondli glycolipids is in progress.