The Antigenic Composition and Immunizing Properties of Trypanosomes

Data are presented on the antigenic composition of Tr. evansi and Tr. lewisi and on the toxic and immunogenic properties of the various components of the cell. Tr. evansi has a higher lipoid and lower residue content than Tr. lewisi. The lipoid and protein fractions when injected into animals produce a leucocytosis and a rise in temperature. None of the fractions on injection produces a hypoglycemia or a depression of temperature as is the case with toxic fractions from bacterial cells. The various antigenic fractions of Tr. evansi fail to induce any immunity in rats. The residue of Tr. lewisi possesses some immunizing properties; this is not the case in Tr. evansi. Injection of whole, dead trypanosomes (Tr. evansi) produces a partial and transient immunity. Treatment with a drug of an active infection of Tr. evansi results in a more solid and durable immunity against a reinfection with the homologous strain; this immunity is extremely variable in individual rats, in some lasting 2 or 3 months and in exceptional instances as long as 9 months. The significance of the cell composition in relation to the antigenic and pathogenic properties of the parasite is discussed and a comparison made with the acid-fast bacteria also having a high lipoid content.