The effect of an immune RNA (RNAi) against Trypanosoma cruzi infection in mice.

Immune ribonucleic acid (RNAi) was extracted with phenol from the spleen of mice immunized with the avirulent PF strain of Trypanosoma cruzi. These preparations were able to induce immunocompetent cells to answer as a secondary response to later challenges with the virulent Y strain of the same parasite. The preparations of RNAi were"immunogenic" and free of proteins. The RNAi preparations were sensitive to pancreatic RNAase and lost their immune effect when pretreated with this enzyme. The injections of normal RNA (RNAn) obtained by the same method showed that this polymer acts as an immuno supressor or competitive agent. The electrophoretic profiles of the RNAi preparations in polyacrylamide gels showed normal and characteristic migration patterns (28S, 18S and 4.5S). These results demonstrate the development of an immune state against T. cruzi infection in mice injected with RNAi, in the absence of living parasites.