Alda Maria Da-Cruz

T-Cell-Mediated Immune Responses in Patients with Cutaneous or Mucosal Leishmaniasis: Long-Term Evaluation after Therapy

ABSTRACT 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+Leishmania-reactive 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-γ) and interleukin-5 (IL-5) production during the period of study. Patients with active ML presented higher IFN-γ 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-γ, 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.

TUMOR NECROSIS FACTOR-A IN HUMAN AMERICAN TEGUMENTARY LEISHMANIASIS

Tumor necrosis factor-alpha (TNF-alpha) is a cytokine produced by activated macrophages and other cells. In order to verify whether the serum levels of TNF-alpha in American tegumentary leishmaniasis patients are associated with the process of cure or aggravation of the disease, 41 patients were studied: 26 cases of cutaneous leishmaniasis (CL) and 15 of mucocutaneous leishmaniasis (MCL). During active disease the serum levels of TNF-alpha of MCL patients were significantly higher than those of CL patients and control subjects (healthy individuals and cutaneous lesions from other etiologies). The MCL patients had serum titers of TNF-alpha significantly lower at the end of antimonial therapy than before therapy. After a six-month follow-up, the MCL patients had serum levels of TNF-alpha similar to those observed at the end of the therapy as well as to those of CL patients and control subjects. No significant variation in the serum levels of TNF-alpha was observed in CL patients throughout the study period (before, at the end of therapy and after a six-month follow-up). The possible relationship between the high TNF-alpha serum levels and severity of the disease is discussed.

Can interferon‐γ and interleukin‐10 balance be associated with severity of human Leishmania (Viannia) braziliensis infection?

Suitable levels of interferon (IFN)‐γ and interleukin (IL)‐10 seem to favour the outcome of cutaneous leishmaniasis (CL), while high IFN‐γ and low IL‐10 production are associated with severity of mucosal leishmaniasis (ML). Considering that cytokine balance is important for the maintenance of protective responses in leishmaniasis, our aim was to investigate leishmanial antigens‐induced IFN‐γ and IL‐10 levels maintained in healed individuals who had different clinical outcomes of Leishmania infection. Thirty‐three individuals who recovered from L. braziliensis infection were studied: cured CL (CCL), cured ML (CML), spontaneous healing of CL (SH) or asymptomatic individuals (ASY). Cytokines were quantified by enzyme‐linked immunosorbent assay (ELISA) in culture supernatants of L. braziliensis‐stimulated peripheral blood mononuclear cells (PBMC). IFN‐γ levels were higher in CML (7593 ±  5994 pg/ml) in comparison to SH (3163 ± 1526 pg/ml), ASY (1313 ±  1048 pg/ml) or CCL (1897 ± 2087 pg/ml). Moreover, cured ML cases maintained significantly lower production of IL‐10 (127 ± 57·8 pg/ml) in comparison to SH (1373 ± 244 pg/ml), ASY (734 ± 233 pg/ml) or CCL (542 ±  375 pg/ml). Thus, a high IFN‐γ/IL‐10 ratio observed in CML can indicate unfavourable cytokine balance. On the other hand, no significant difference in the IFN‐γ/IL‐10 ratio was observed when CCL individuals were compared to SH or ASY subjects. In conclusion, even after clinical healing, ML patients maintained a high IFN‐γ/IL‐10 secretion profile in response to leishmanial antigens. This finding can explain a delayed down‐modulation of exacerbated inflammatory responses, which can be related in turn to the necessity of prolonged therapy in ML management. Conversely, lower IFN‐γ/IL‐10 balance observed in CCL, SH and ASY individuals can represent a better‐modulated immune response associated with a favourable prognosis.

Immunologic patterns associated with cure in human American cutaneous leishmaniasis

Patients with American cutaneous leishmaniasis were studied before therapy (active lesion) and at the end of therapy (cured patients). Assays of lymphocyte proliferative responses of peripheral blood mononuclear cells induced in vitro by Leishmania braziliensis promastigote antigens (Lb) were performed. Antigen-stimulated cells were harvested for CD4 and CD8 phenotype analysis and the levels of gamma interferon (IFN-gamma) and interleukin 4 (IL-4) produced were also determined in the culture supernatants. Two different patterns of Lb-induced T cell responses were observed: a) predominance of responding CD4+ cells and mixed type 1 and type 2 cytokine production (IFN-gamma and IL-4) during the active disease, and b) similar proportions of responding CD4+ and CD8+ cells, and type 1 cytokine production (presence of IFN-gamma and very low IL-4) at the end of therapy (healed lesions). This last pattern is probably associated with a beneficial T cell response.

Disseminated American muco-cutaneous leishmaniasis caused by Leishmania brasiliensis brasiliensis in a patient with AIDS: a case report

The authors report a case of culture-proven disseminated American muco-cutaneous leishmaniasis caused by Leishmania braziliensis braziliensis in an HIV positive patient. Lesions began in the oropharynx and nasal mucosa eventually spreading to much of the skin surface. The response to a short course of glucantime therapy was good.

Flow cytometric analysis of cellular infiltrate from American tegumentary leishmaniasis lesions.

Background  CD4+ and CD8+ T lymphocytes play different roles in the outcome of leishmaniasis. However, T‐cell distribution in lesions shows significant variability in in situ immunocytochemical studies.

Cellular and humoral immune responses of a patient with American cutaneous leishmaniasis and AIDS

The lymphocyte responsiveness to leishmanial antigens and its influence on the course of cutaneous leishmaniasis was studied in a patient with AIDS-associated American cutaneous leishmaniasis caused by Leishmania braziliensis. The patient had cutaneous disseminated erythematous papules or nodules and mucosal lesions as well as moniliasis and weight loss. The patient had a poor delayed-type hypersensitivity to leishmanial antigens, showing 3 mm of induration. The cellular immune responses were studied in vitro by lymphocyte proliferative assays induced by leishmanial antigens and concanavalin A. The T cell phenotypes were analysed by flow cytometry. The peripheral blood mononuclear cells before proliferation showed an inversion of the CD4/CD8 ratio (0.28:1). The lymphoproliferative responses to antigen and mitogen were very low (indices < 2.5). The blast-like cell phenotypes after antigen stimulation in culture were: CD3+ 44.8%, CD4+ 7.53% and CD8+ 17.45%. In AIDS patients the decrease in the pool of CD4+ cells, and consequent diminution of the CD4/CD8 ratio, produced by HIV infection provokes a generalized immune depression. The patients disseminated clinical picture was probably related to the inability of his T cell-mediated immune responses to control the spread of Leishmania infection.

T-cell responses associated with resistance to Leishmania infection in individuals from endemic areas for Leishmania (Viannia) braziliensis

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-gamma) 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-gamma) 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-gamma), 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.

Detection of early apoptosis and cell death in T CD4+ and CD8+ cells from lesions of patients with localized cutaneous leishmaniasis

Human localized cutaneous leishmaniasis (LCL), induced by Leishmania braziliensis, ranges from a clinically mild, self-healing disease with localized cutaneous lesions to severe forms which can present secondary metastatic lesions. The T cell-mediated immune response is extremely important to define the outcome of the disease; however, the underlying mechanisms involved are not fully understood. A flow cytometric analysis of incorporation of 7-amino actinomycin D and CD4+ or CD8+ T cell surface phenotyping was used to determine whether different frequencies of early apoptosis or accidental cell death occur at different stages of LCL lesions. When all cells obtained from a biopsy sample were analyzed, larger numbers of early apoptotic and dead cells were observed in lesions from patients with active disease (mean = 39.5 +/- 2.7%) as compared with lesions undergoing spontaneous healing (mean = 17.8 +/- 2.2%). Cells displaying normal viability patterns obtained from active LCL lesions showed higher numbers of early apoptotic events among CD8+ than among CD4+ T cells (mean = 28.5 +/- 3.8 and 15.3 +/- 3.0%, respectively). The higher frequency of cell death events in CD8+ T cells from patients with LCL may be associated with an active form of the disease. In addition, low frequencies of early apoptotic events among the CD8+ T cells were observed in two patients with self-healing lesions. Although the number of patients in the latter group was small, it is possible to speculate that, during the immune response, differences in apoptotic events in CD4+ and CD8+ T cell subsets could be responsible for controlling the CD4/CD8 ratio, thus leading to healing or maintenance of disease.

IFNG +874T/A polymorphism is not associated with American tegumentary leishmaniasis susceptibility but can influence Leishmania induced IFN-γ production

BackgroundInterferon-gamma is a key cytokine in the protective responses against intracellular pathogens. A single nucleotide polymorphism (SNP) located in the first intron of the human IFN-γ gene can putatively influence the secretion of cytokine with an impact on infection outcome as demonstrated for tuberculosis and other complex diseases. Our aim was to investigate the putative association of IFNG+874T/A SNP with American tegumentary leishmaniasis (ATL) and also the influence of this SNP in the secretion of IFN-γ in vitro.MethodsBrazilian ATL patients (78 cutaneous, CL, and 58 mucosal leishmaniasis, ML) and 609 healthy volunteers were evaluated. The genotype of +874 region in the IFN-γ gene was carried out by Amplification Refractory Mutational System (ARMS-PCR). Leishmania-induced IFN-γ production on peripheral blood mononuclear cell (PBMC) culture supernatants was assessed by ELISA.ResultsThere are no differences between +874T/A SNP frequency in cases and controls or in ML versus CL patients. Cutaneous leishmaniasis cases exhibiting AA genotype produced lower levels of IFN-γ than TA/TT genotypes. In mucosal cases, high and low IFN-γ producers were clearly demonstrated but no differences in the cytokine production was observed among the IFNG +874T or A carriers.ConclusionOur results suggest that +874T/A polymorphism was not associated with either susceptibility or severity to leishmaniasis. Despite this, IFNG +874T/A SNP could be involved in the pathogenesis of leishmaniasis by influencing the amount of cytokine released by CL patients, although it could not prevent disease development. On the other hand, it is possible that in ML cases, other potential polymorphic regulatory genes such as TNF-α and IL-10 are also involved thus interfering with IFN-γ secretion.