CD8+ T Cells Specific for Immunodominant Trans -Sialidase Epitopes Contribute to Control of Trypanosoma cruzi Infection but Are Not Required for Resistance

Abstract

CD8+ T cells are essential for controlling Trypanosoma cruzi infection. During Brazil strain infection, C57BL/6 mice expand parasite-specific CD8+ T cells recognizing the dominant TSKB20 (ANYKFTLV) and subdominant TSKB74 (VNYDFTLV) trans-sialidase gene (TS)-encoded epitopes with up to 40% of all CD8+ T cells specific for these epitopes. Although this is one of the largest immunodominant T cell responses described for any infection, most mice fail to clear T. cruzi and subsequently develop chronic disease. To determine if immunodominant TS-specific CD8+ T cells are necessary for resistance to infection, we epitope-tolerized mice by high-dose i.v. injections of TSKB20 or TSKB74 peptides. Tolerance induction led to deletion of TS-specific CD8+ T cells but did not prevent the expansion of other effector CD8+ T cell populations. Mice tolerized against either TSKB20 or TSKB74, or both epitopes simultaneously, exhibited transient increases in parasite loads, although ultimately they controlled the acute infection. Furthermore, BALB/c mice tolerized against the TSKD14 peptide effectively controlled acute T. cruzi infection. These data are consistent with the hypothesis that development of high-frequency CD8+ T cell populations focused on TS-derived epitopes contributes to optimal control of acute infection but is not required for the development of immune resistance.