CD8þT cells are not required for vaccine-induced immunity against Leishmania amazonensis in IL-12/23P40_/_ C57BL/6 mice.

Abstract

Vaccine-induced protection against leishmaniasis is largely dependent on cell-mediated type 1 response and IL-12-driven IFN-g production. Surprisingly, our previous data showed that IL-12/23p40_/_ mice could be vaccinated against L. amazonensis and were able to produce limited amounts of IFN-g. Since the role of CD8þT in immunization against L. amazonensis is obscure, the aim of this study was to evaluate the effects of CD8þ cells in protection against L. amazonensis in IL-12/23p40_/_ mice. In order to deplete CD8þ cells, one group of vaccinated animals was treated with anti-CD8 mAb. Infection was followed for 8 weeks. The vaccinated CD8þ-depleted group developed smaller lesions than the non-depleted group. CD8 depletion did not affect tissue parasitism or antibody response against the parasite, and treated animals displayed milder inflammation and better tissue integrity. IFN-g production in spleen and draining lymph node was impaired in the depleted group, suggesting that CD8þ cells produced this cytokine in IL-12-independent vaccination. Such results suggest that this T cell subset contributes to augmented pathology in IL12/23p40_/_ mice vaccinated and challenged with L. amazonensis. Although these cells could produce some IFN-g the in the absence of IL-12, they do not affect the parasite tissue load.