T-cell immune responses in patients with cutaneous leishmaniasis (CL) and mucosal leishmaniasis (ML)were studied during the active disease, at the end of therapy, and 1 to 17 years posttherapy (long-term follow-up). Lymphocyte proliferative responses, phenotypic characterization of CD4 ؉ and CD8 ؉ Leishmaniareactive T cells, and cytokine production were assayed. Patients with active ML and CL showed higher proportions of CD4 ؉ than CD8 ؉ T cells. In CL, the healing process was associated with a decrease of CD4؉ and an increase of CD8 ؉ , leading to similar CD4 ؉ and CD8 ؉ proportions. This pattern was only seen in ML after long-term therapy. Long-term follow-up of patients with CL showed a positive CD4؉ /CD8 ؉ ratio as observed during the active disease, although the percentages of these T cell subsets were significantly lower. Patients with CL did not show significant differences between gamma interferon (IFN-␥) and interleukin-5 (IL-5) production during the period of study. Patients with active ML presented higher IFN-␥ and IL-5 levels compared to patients with active CL. IL-4 was only detected during active disease. Patients long term after cure from ML showed increasing production of IFN-␥, significant decrease of IL-5, and no IL-4 production. Two apparently beneficial immunological parameters were detected in tegumentary leishmaniasis: (i) decreasing proportions of CD4 ؉ Leishmania-reactive T cells in the absence of IL-4 production associated with cure of CL and ML and (ii) decreasing levels of IL-5 long after cure, better detected in patients with ML. The observed T-cell responses maintained for a long period in healed patients could be relevant for immunoprotection against reinfection and used as a parameter for determining the prognosis of patients and selecting future vaccine preparations.

Subclinical or asymptomatic infection is documented in individuals living in endemic areas for leishmaniasis suggesting that the development of an appropriate immune response can control parasite replication and maintain tissue integrity. A low morbidity indicates that intrinsic factors could favor resistance to Leishmania infection. Herein, leishmanial T-cell responses induced in subjects with low susceptibility to leishmaniasis as asymptomatic subjects were compared to those observed in cured cutaneous leishmaniasis (CCL) patients, who controlled the disease after antimonial therapy. All of them have shown maintenance of specific long-term immune responses characterized by expansion of higher proportions of CD4 + as compared to CD8 + Leishmania reactive T-lymphocytes. Asymptomatic subjects had lower indexes of in vitro Leishmania induced lymphoproliferative responses and interferon-gamma (IFN-γ) production in comparison to CCL patients. On the other hand, interleukin (IL-10) production was much higher in asymptomatics than in CCL, while no differences in IL-5 levels were found. In conclusion, long lived T-cell responses achieved by asymptomatic individuals differed from those who had developed symptomatic leishmaniasis in terms of intensity of lymphocyte activation (proliferation or IFN-γ) and regulatory mechanisms (IL-10). The absence of the disease in asymptomatics could be explained by their intrinsic ability to create a balance between immunoregulatory (IL-10) and effector cytokines (IFN-γ), leading to parasite destruction without producing skin tissue damage. The establishment of profiles of cell-mediated immune responses associated with resistance against Leishmania infection is likely to make new inroads into understanding the long-lived immune protection against the disease.Key words: asymptomatic infection -Leishmania (Viannia) braziliensis -cured leishmaniasis -cytokines -T-cell subsetslong term immunity (Grimaldi Jr & MacMahon-Pratt 1991). The spectrum of the clinical presentation ranges from self-healing or benign cutaneous lesions to more severe forms, such as disseminated lesions or mucosal involvement (Da-Cruz & Pirmez 2005).Studies conducted in mice and humans have unequivocally shown that a major T-cell driven component underlies the establishment of acquired immunity and protection against re-infection ( Coutinho et al. 1996, Louis et al. 1998, Bosque et al. 2000. Cytokines such as interferon-gamma (IFN-γ) and tumor necrosis factoralpha (TNF-α) activate macrophages for killing parasites, while interleukin (IL)-4, IL-5, IL-10, and transforming grow factor-beta (TGF-β) favor intracellular parasite growth (Louis et al. 1998. In addition, IL-10 production by CD4 + CD25 + T-cells is required for maintenance of Leishmania after cure, which in turn preserves an adaptive immunity to L. (Leishmania) major (Belkaid et al. 2002).The majority of ATL patients develop cutaneous leishmaniasis (CL) (Oliveira-Neto et al. 2000), but occurrence of subclinical or asymptomatic infection strongly suggests that po...

SummaryThe cutaneous leucocyte-associated antigen receptor (CLA) can direct Leishmania-specific T lymphocytes towards inflamed skin lesions. Homing receptors [CLA, lymphocyte-associated antigen 1 (LFA-1) or CD62L] were analysed in lymphocytes from blood and cutaneous leishmaniasis (CL) lesions. CL patients with active lesions (A-CL) presented lower levels of T lymphocytes expressing the CLA + phenotype (T CD4 + = 10·4% Ϯ 7·5% and T CD8 + = 5·8% Ϯ 3·4%) than did healthy subjects (HS) (T CD4 + = 19·3% Ϯ 13·1% and T CD8 + = 21·6% Ϯ 8·8%), notably in T CD8 + (P < 0·001). In clinically cured patients these percentages returned to levels observed in HS. Leishmanial antigens up-regulated CLA in T cells (CLA + in T CD4 + = 33·3% Ϯ 14·1%; CLA + in T CD8 + = 22·4% Ϯ 9·4%) from A-CL but not from HS. An enrichment of CLA + cells was observed in lesions (CLA + in T CD4 + = 45·9% Ϯ 22·5%; CLA + in T CD8 + = 46·4% Ϯ 16·1%) in comparison with blood (CLA + in T CD4 + = 10·4% Ϯ 7·5%; CLA + in T CD8 + = 5·8% Ϯ 3·4%). Conversely, LFA-1 was highly expressed in CD8+ T cells and augmented in CD4+ T from peripheral blood of A-CL patients. In contrast, CD62L was not affected. These results suggest that Leishmania antigens can modulate molecules responsible for migration to skin lesions, potentially influencing the cell composition of inflammatory infiltrate of leishmaniasis or even the severity of the disease.

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An exacerbated type 1 response to leishmanial antigens is the basis of tissue destruction observed in mucosal leishmaniasis (ML). After therapy, a persistent production of high levels of inflammatory cytokines can confer a poor prognosis. Herein we investigated whether the clinical conditions defined during the active phase of ML affect the magnitude of long-term anti-Leishmania immune response. Twenty clinically cured ML cases were studied. Peripheral blood mononuclear cells (PBMC) were cultured with L. braziliensis antigens (Lb-Ag), Toxoplasma gondii antigens (Tg-Ag), concanavalin-A (Con-A) or medium alone, and the lymphocyte proliferative response and cytokine secretion were quantified. Medical records were reviewed for Montenegro skin test (MST) during diagnosis, duration of ML disease or time elapsed after clinical cure. The duration of disease was correlated positively with MST (r = 0·61). Lb-Ag induced interferon (IFN)-γ was correlated positively with duration of illness (r = 0·69) as well as the frequency of secreting cells [enzyme-linked immunospot (ELISPOT)] assay. No association was observed for Tg-Ag or Con-A. Disease duration was correlated negatively with interleukin (IL)-10 production (r = −0·76). Moreover, a negative correlation between length of time after clinical cure and TNF levels (r = −0·94) or the IFN-γ : IL-10 ratio (r = −0·89) were also seen. We suggest that the magnitude of the IFN-γ inflammatory response triggered by ML can be driven by the time of leishmanial antigens exposition during the active phase of the disease. This pattern could persist even long-term after cure. However, despite IFN-γ levels, the decrease of the TNF and IFN-γ : IL-10 ratio reflects the control of proinflammatory responses achieved by cure of ML, possibly preventing disease relapses.