Leishmania infantum‐specific T cell lines derived from asymptomatic dogs that lyse infected macrophages in a major histocompatibility complex‐restricted manner

Abstract

Protective immunity to leishmaniasis has been demonstrated in murine models to be mediated by T cells and the cytokines they produce. We have previously shown that resistance to experimental Leishmania infantum infection in the dog, a natural host and reservoir of the parasite, is associated with the proliferation of peripheral blood mononuclear cells (PBMC) to parasite antigen and to the production of interleukin-2 and tumour necrosis factor. In this study we show that PBMC from asymptomatic experimentally infected dogs produce interferon-gamma upon parasite antigen-specific stimulation, whereas lymphocytes from symptomatic dogs do not. In addition, we report for the first time the lysis of L. infantum-infected macrophages by PBMC from asymptomatic dogs and by parasite-specific T cell lines derived from these animals. These T cell lines were generated by restimulation in vitro with parasite soluble antigen and irradiated autologous PBMC as antigen-presenting cells. We show that lysis of infected macrophages by T cell lines is major histocompatibility complex restricted. Characterization of parasite-specific cytotoxic T cell lines revealed that the responding cells are CD8+. However, for some animals, CD4+ T cells that lyse infected macrophages were also found. In contrast to asymptomatic dogs, lymphocytes from symptomatic dogs failed to proliferate and produce interferon-gamma after Leishmania antigen stimulation in vitro and were not capable of lysing infected macrophages. These results suggest that both the production of interferon-gamma and the destruction of the parasitized host cells by Leishmania-specific T cells play an important role in resistance to visceral leishmaniasis.

Relationship between clinical and pathological signs and severity of canine leishmaniasis

“…In this study, the clinical classification was chosen because of its widespread adoption in the literature of both the Old and New World, whether in natural or experimental infection (PINELLI et al, 1994(PINELLI et al, , 1995TRAVI et al, 2001;FERNÁNDEZ-PÉREZ et al, 2003;COSTA-VAL, 2004;REIS et al, 2006a, b). The analysis revealed dysproteinemia, azotemia and anemia as the main laboratory findings in dogs naturally infected with different clinical forms of visceral leishmaniasis.…”

SIR2-Deficient Leishmania infantum Induces a Defined IFN-γ/IL-10 Pattern That Correlates with Protection

“…The high percentage of specific lysis of the L. infantum-infected J774 murine macrophage line suggests that an anti-Leishmania cytotoxic response is generated in protected mice. The lysis of parasitized macrophages has been observed in mice (62), hamsters (63), dogs (64), and humans (65) and might be an important mechanism involved in resistance to leishmaniasis. Although the characterization of the cells involved in the cytotoxic activity observed in the present study was not done, several reports have shown that both class I-restricted cytotoxic CD8 ϩ and CD4 ϩ T cells as well as NK cells are potential effector cells.…”

Evaluation of TNF-α, IL-4, and IL-10 and parasite density in spleen and liver ofL. (L.) chagasinaturally infected dogs

“…The occurrence of dogs asymptomatic for VL has been associated with the activation of Th1 cells that produce interferon (IFN)-c, interleukin (IL)-2 and tumor necrosis factor (TNF)-a (Pinelli et al, 1994;Pinelli et al, 1995). Leishmania parasites are killed by macrophages activated by IFN-c producing lymphocytes via a nitric oxide dependent mechanism (Vouldoukis et al, 1996;Holzmuller et al, 2005).…”