Successful treatment of refractory mucosal leishmaniasis with pentoxifylline plus antimony

Functional dichotomy of dendritic cells following interaction with Leishmania braziliensis: infected cells produce high levels of TNF-alpha, whereas bystander dendritic cells are activated to promote T cell responses

Leishmania braziliensis infections are often associated with exaggerated immune responses that can sometimes lead to severe disease associated with high levels of IFN-gamma and TNF-alpha. To explore the role played by dendritic cells (DCs) in these responses, we characterized DCs that were exposed to L. braziliensis. We found that DCs cultured with L. braziliensis parasites up-regulated DC activation markers and produced IL-12 and TNF-alpha. However, not all DCs in the culture became infected, and an analysis of infected and uninfected DCs demonstrated that the up-regulation of activation markers and IL-12 production was primarily confined to the uninfected (bystander) DCs. Further studies with Transwell chambers and parasite fractions indicated that the activation of bystander DCs was mediated by a soluble parasite product, in a type 1 IFN- and MyD88-independent, but TNF-alpha-dependent fashion, and that the activated DCs were more efficient at presenting Ag than control DCs. In contrast, L. braziliensis-infected DCs failed to up-regulate activation markers, but exhibited a dramatic enhancement in their ability to produce TNF-alpha in response to LPS as compared with uninfected DCs. These findings uncover a dual role for DCs in L. braziliensis infection: T cell activation by bystander DCs due to enhanced Ag-presenting capacity following exposure to soluble parasite products, and increased production of TNF-alpha by infected cells that may contribute to the local control of the parasites, but concomitantly induce immunopathology.

Interventions for Old World cutaneous leishmaniasis

BACKGROUND

Cutaneous leishmaniasis is caused by a parasitic infection and is considered one of the most serious skin diseases in many developing countries. Antimonials are the most commonly prescribed treatment but other drugs have been used with varying success.

OBJECTIVES

To assess the effects of treatments for Old World cutaneous leishmaniasis (OWCL).

SEARCH STRATEGY

We searched the Cochrane Skin Group Specialised Register (April 2008), the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 2, 2008), MEDLINE (2003-April 2008), EMBASE (2005-April 2008), CINAHL (1982-August 2007), LILACS (from inception to April 2008) and ongoing trials databases (August 2007).

SELECTION CRITERIA

Randomised controlled trials assessing treatments in immuno-competent people with OWCL confirmed by smear, histology, culture or polymerase chain reaction.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data.

MAIN RESULTS

We included 49 trials involving 5559 participants. Reporting quality was generally poor and only two studies contained sufficiently similar data to pool.In Leishmania major infections, there was good RCT evidence of benefit of cure around 3 months after treatment when compared to placebo for 200 mg oral fluconazole (1 RCT n = 200, RR 2.78; 95% CI 1.86, 4.16), topical 15% paromomycin + 12% methylbenzethonium chloride (PR-MBCL) (1 RCT n = 60, RR 3.09; 95% CI 1.14, 8.37) and photodynamic therapy (1 RCT n = 60, RR 7.02; 95% CI 3.80, 17.55). Topical PR-MBCL was less efficacious than photodynamic therapy (1 RCT n = 65, RR 0.44; 95% CI 0.29, 0.66). Oral pentoxifylline was a good adjuvant therapy to intramuscular meglumine antimoniate (IMMA) when compared to IMMA plus placebo (1 RCT n = 64, RR 1.63; 95% CI 1.11, 2.39)In Leishmania tropica infections, there was good evidence of benefit for the use of 200 mg oral itraconazole for 6 weeks compared with placebo (1 RCT n = 20, RR 7.00; 95% CI 1.04, 46.95), for intralesional sodium stibogluconate (1 RCT n = 292, RR 2.62; 95% CI 1.78, 3.86), and for thermotherapy compared with intramuscular sodium stibogluconate (1 RCT n = 283, RR 2.99; 95% CI 2.04, 4.37).

AUTHORS' CONCLUSIONS

Most trials have been designed and reported poorly, resulting in a lack of evidence for potentially beneficial treatments. There is a desperate need for large well conducted studies that evaluate long-term effects of current therapies. We suggest the creation of an international platform to improve quality and standardization of future trials in order to inform clinical practice.

An essential role for transmembrane TNF in the resolution of the inflammatory lesion induced by Leishmania major infection

TNF is an essential player in infections with Leishmania major, contributing to the control of the inflammatory lesion and, to a lesser degree, to parasite killing. However, the relative contribution of the soluble and transmembrane forms of TNF in these processes is unknown. To investigate the role of transmembrane TNF (mTNF) in the control of L. major infections, mTNF-knock-in (mTNF(Delta/Delta)) mice, which express functional mTNF but do not release soluble TNF, were infected with L. major, and the development of the inflammatory lesion and the immune response was compared to that occurring in L. major-infected TNF(-/-) and wild-type mice. mTNF(Delta/Delta) mice controlled the infection and resolved their inflammatory lesion as well as wild-type mice, a process associated with the early clearance of neutrophils at the site of parasite infection. In contrast, L. major-infected TNF(-/-) mice developed non-healing lesions, characterized by an elevated presence of neutrophils at the site of infection and partial control of parasite number within the lesions. Altogether, the results presented here demonstrate that mTNF, in absence of soluble TNF, is sufficient to control infection due to L. major, enabling the regulation of inflammation, and the optimal killing of Leishmania parasites at the site of infection.

Pentoxifylline down modulate in vitro T cell responses and attenuate pathology in Leishmania and HTLV-I infections

Tumor necrosis factor-alpha (TNF-alpha) is known to have numerous biological properties relating to inflammation. This cytokine participates in the tissue damage of chronic inflammatory, autoimmune and infectious diseases. Pentoxifylline is a methylxanthine that inhibits phosphodiesterase IV, which inhibits the degradation of the cAMP and prostanoids. The increased intracellular concentration of the cAMP leads to a negative regulation of NF-kappaB and NF-AT transcription factors and suppresses TNF-alpha production. This review describes studies that support evidences that TNF-alpha is involved in the pathogenesis of HTLV-1 associated myelopathy and of cutaneous and mucosal leishmaniasis. Additionally, it demonstrates the effect of pentoxifylline in vitro in inhibiting TNF-alpha and IFN-gamma spontaneous production in PBMC from HTLV-1-infected patients, as well as its in vivo effect in inhibiting TNF-alpha in sera from mucosal leishmaniasis patients. Moreover, we review the results of clinical studies from the last 10 years using pentoxifylline to treat HTLV-1 associated myelopathy and cutaneous and mucosal leishmaniasis.

Mucosal leishmaniasis . Current scenario and prospects for treatment

Leishmaniasis causes significant morbidity and mortality and thus constitutes a serious public health problem. Even though it has long been endemic in developing countries, in recent years the economic globalization and the increased volume of international travel have extended its prevalence in developed countries. In addition, native populations may be exposed to the infection through blood transfusion and the use of blood products produced from infected asymptomatic individuals. Mucosal leishmaniasis (ML) is a chronic form of this infection, which attacks the mucosa. In most cases this form of leishmaniasis results from the metastatic spread of Leishmania (Viannia) braziliensis from cutaneous lesions. It is a healthcare issue because of its wide demographic distribution, its association with significant morbidity levels, and because of the pressing concern that tourists who travel to endemic areas might present the disease even years later. The treatment currently available for ML is based on drugs such as pentavalent antimony-containing compounds, amphotericin B deoxycholate and pentamidine and often guarantees a satisfactory clinical response. Nevertheless, it also frequently provokes serious side effects. This review offers a critical analysis of the drugs now available for the treatment of ML as also of the future prospects for the treatment of the disease.

Cytokines, signaling pathways, and effector molecules required for the control of Leishmania (Viannia) braziliensis in mice

Cutaneous leishmaniasis is caused by protozoan parasites of the genus Leishmania. The mechanisms of pathogen control have been established primarily in the mouse model of Leishmania major infection, but they might not hold true for other Leishmania species associated with cutaneous disease. Here, we analyzed the role of cytokines, signaling components, and effector molecules in the control of New World cutaneous leishmaniasis due to L. braziliensis. Unlike L. major, L. braziliensis caused small, nonulcerative, and self-healing skin swelling in C57BL/6 mice, as well as BALB/c mice. In contrast to the results obtained for L. mexicana, mice deficient for interleukin-12 or its key signaling molecule, signal transducer and activator of transcription 4, rapidly succumbed to severe visceral leishmaniasis. Infection of tumor necrosis factor knockout mice with L. braziliensis led to progressive, nonhealing skin lesions with erosions and hemorrhagic ulcerations, but in contrast to the results with L. major, only 20 to 30% of the mice developed fatal visceral disease. As seen with L. major, mice with a deleted inducible nitric oxide synthase gene (iNOS(-/-)) were unable to contain L. braziliensis in the skin, whereas the control of the parasite in the spleen remained unimpaired. Unlike what happens in L. major infections, NADPH oxidase had no impact on the course of disease in L. braziliensis-infected mice. These results not only define essential components of a protective immune response to L. braziliensis but also illustrate that the requirements for the control of cutaneous leishmaniasis vary between different parasite species.

Differential immune regulation of activated T cells between cutaneous and mucosal leishmaniasis as a model for pathogenesis

Cutaneous (CL) and mucosal leishmaniasis (ML) are characterized by a predominant type 1 immune response (IFN-gamma and TNF-alpha production) and strong inflammatory response in the lesions with few parasites. This exacerbated type 1 response is more evident in ML as compared to CL. Our main hypothesis is that a differential immune regulation of T cell activation leads to over reactive T cells in ML. In the present study, we investigated immunological factors that could explain the mechanisms behind it by comparing some immune regulatory mechanisms between ML and CL patients: frequency of cells expressing co-stimulatory molecules, apoptotic markers, T cell activation markers; and ability of neutralizing antibodies to IL-2, IL-12 and IL-15 do down-regulate IFN-gamma production in leishmania antigen-stimulated peripheral blood mononuclear cells (PBMC). Interestingly, in CL anti-IL-2 and anti-IL-15 significantly suppressed antigen-specific IFN-gamma production, while in ML only anti-IL-2 suppressed IFN-gamma production. Finally, higher frequency of CD4+ T cells expressing CD28-, CD69+ and CD62L(low) were observed in ML as compared to CL. These data indicate that an exacerbated type 1 response in ML is differentially regulated and not appropriately down modulated, with increased frequencies of activated effectors T cells, maintaining the persistent inflammatory response and tissue damage observed in ML.

Cutaneous leishmaniasis treatment

The causative species of cutaneous leishmaniasis determines the clinical features and courses, and treatments. Intralesional or systemic antimonials are the gold standard for the treatment of these diseases. However, as for visceral leishmaniasis, other therapeutic options appear promising. Paromomycin ointments are effective in Leishmania major, L. tropica, L. mexicana, and L. panamensis lesions. In L. braziliensis localized leishmaniasis, both paromomycin and imiquimod may be topically applied. Oral fluconazole and zinc sulfate are useful in L. major. Oral azithromycin, effective in vitro and in mice, needs further investigation in human leishmaniasis. On the contrary, data with oral itraconazole are disappointing. Oral miltefosine, which is very effective in visceral leishmaniasis caused by L. donovani, appears ineffective in L. major and L. braziliensis infections. Intramuscular pentamidine is required for L. guyanensis cutaneous leishmaniasis, for which systemic antimony is not effective. Liposomal amphotericin B could be an alternative to antimony in south American cutaneous leishmaniasis with mucosal involvement (especially L. braziliensis and L. guyanensis infections).

Tratamento da Leishmaniose Tegumentar Americana

A leishmaniose tegumentar americana é doença infecciosa da pele e mucosa, cujo agente etiológico é um protozoário do gênero Leishmania. Seu tratamento é desafio porque as drogas disponíveis apresentam elevada toxicidade, e nenhuma delas é bastante eficaz. A recidiva, a falha terapêutica em pacientes imunodeprimidos e a resistência ao tratamento são fatores que motivam a busca de uma droga ideal.

Oral Pentoxifylline Combined with Pentavalent Antimony: A Randomized Trial for Mucosal Leishmaniasis

BACKGROUND

Mucosal leishmaniasis is associated with intense tissue damage and high tumor necrosis factor-alpha production. Therapeutic failure occurs in up to 42% of cases; patients who experience treatment failure will require >1 pentavalent antimony (Sb(v)) course or alternative drugs to achieve a cure. We previously showed that an inhibitor of tumor necrosis factor-alpha (pentoxifylline) combined with Sb(v) cured 90% patients refractory to monotherapy with Sb(v).

METHODS

A double-blind, placebo-controlled trial involving 23 patients with mucosal leishmaniasis evaluated the efficacy of pentoxifylline when administered in association with Sb(v), compared with Sb(v) treatment alone. Eleven patients were randomized to receive Sb(v) plus oral pentoxifylline for 30 days, and 12 patients received Sb(v) plus oral placebo. The criterion for cure was a complete healing of lesions.

RESULTS

All patients in the pentoxifylline group experienced a cure with 1 course of Sb(v), whereas 5 (41.6%) of 12 patients in the placebo group required a second course of Sb(v) (P=.037). The healing time +/- standard deviation in the pentoxifylline group was 83+/-36 days, compared with 145+/-99 days in the placebo group (P=.049). No relapses were documented in either group at the 2-year follow-up visit.

CONCLUSIONS

The addition of pentoxifylline to Sb(v) in mucosal leishmaniasis reduces the healing time significantly and prevents the need for further courses of Sb(v).

Effect of combination therapy with systemic glucantime and pentoxifylline in the treatment of cutaneous leishmaniasis

INTRODUCTION

Cutaneous leishmaniasis is a common parasitic disease in Iran, especially in Isfahan. First line treatment for this disease is antimonial compounds; however, owing to the intermittent failure of this treatment and its significant side-effects alternative therapeutic measures have been advocated.

OBJECTIVE

Evaluating the efficacy of pentoxifylline plus glucantime in the treatment of cutaneous leishmaniasis.

METHODS

This double-blind, randomized, controlled clinical trial with simple sampling was performed on 64 patients with cutaneous leishmaniasis referred to the Skin Diseases & Leishmaniasis Research Center from an endemic foci of L. major in Isfahan. The patients randomly were divided into two groups. One group was treated with systemic Glucantime (20 mg pentavalent antimony/kg/day) combined with pentoxifylline (400 mg three times daily) and the other group were treated with Glucantime (20 mg pentavalent antimony/kg/day) plus placebo (three tablets daily) for 20 days. Follow up lasted 3 months. Response to treatment was grouped as complete improvement (lesions had been flattened, no induration, and epidermal creases had appeared), partial improvement (reduction in lesion size, but without the appearance of epidermal creases) and poor response (no reduction in lesion size).

RESULTS

Of 64 participants, 32 patients in the trial group and 31 patients in the control group were followed for 3 months. One patient in group B discontinued withdrew. After this time, complete improvement, partial improvement and poor response to treatment were 81.3%, 12.5% and 6.2% in the trial group and 51.6%, 29% and 19.4% in the control group, respectively. We also observed no adverse effect resulting from pentoxifylline.

DISCUSSION

The result obtained by two therapeutic methods indicates that combined therapy with Glucantime and pentoxifylline is more effective than Glucantime alone (P < 0.05).

Decreased in situ expression of interleukin-10 receptor is correlated with the exacerbated inflammatory and cytotoxic responses observed in mucosal leishmaniasis

Human infection with Leishmania braziliensis can lead to cutaneous leishmaniasis (CL) or mucosal leishmaniasis (ML). We hypothesize that the intense tissue destruction observed in ML is a consequence of an uncontrolled exacerbated inflammatory immune response, with cytotoxic activity. For the first time, this work identifies the cellular sources of inflammatory and antiinflammatory cytokines, the expression of effector molecules, and the expression of interleukin-10 (IL-10) receptor in ML and CL lesions by using confocal microscopy. ML lesions displayed a higher number of gamma interferon (IFN-gamma)-producing cells than did CL lesions. In both ML and CL, CD4+ cells represented the majority of IFN-gamma-producing cells, followed by CD8+ cells and CD4- CD8- cells. The numbers of tumor necrosis factor alpha-positive cells, as well as those of IL-10-producing cells, were similar in ML and CL lesions. The effector molecule granzyme A showed greater expression in ML than in CL lesions, while inducible nitric oxide synthase did not. Finally, the expression of IL-10 receptor was lower in ML than in CL lesions. Thus, our data identified distinct cytokine and cell population profiles for CL versus ML patients and provide a possible mechanism for the development of ML disease through the demonstration that low expression of IL-10 receptor is present in conjunction with a cytotoxic and inflammatory profile in ML.

CD16+ monocytes in human cutaneous leishmaniasis: increased ex vivo levels and correlation with clinical data

Peripheral blood CD16 (Fc receptor for immunoglobulin G III)-positive monocytes have been shown to expand in different pathological conditions, such as cancer, asthma, sepsis, human immunodeficiency virus infection, and AIDS progression, but data in leishmaniasis are lacking. We found that cutaneous leishmaniasis patients (n = 15) displayed a significant increase in the percentage (3.5 vs. 10.1) as well as mean fluorescent intensity (13.5 vs. 29.2) of ex vivo CD16 expression in monocytes as compared with healthy controls. We observed a significant positive correlation between the percentage of ex vivo CD16+ monocytes and lesion size (P = 0.0052, r = 0.75) or active transforming growth factor-beta plasma levels (P = 0.0017, r = 0.78). In addition, two patients with nonhealing lesions during a 3-year follow-up had high (9.1-19.4%) CD16 levels at diagnosis. Our data suggest a deleterious role for CD16 in human leishmaniasis, as well as its possible use as a marker for disease severity and/or adverse disease outcome.

Advances in leishmaniasis

Governed by parasite and host factors and immunoinflammatory responses, the clinical spectrum of leishmaniasis encompasses subclinical (inapparent), localised (skin lesions), and disseminated infection (cutaneous, mucosal, or visceral). Symptomatic disease is subacute or chronic and diverse in presentation and outcome. Clinical characteristics vary further by endemic region. Despite T-cell-dependent immune responses, which produce asymptomatic and self-healing infection, or appropriate treatment, intracellular infection is probably life-long since targeted cells (tissue macrophages) allow residual parasites to persist. There is an epidemic of cutaneous leishmaniasis in Afghanistan and Pakistan and of visceral infection in India and Sudan. Diagnosis relies on visualising parasites in tissue or serology; culture and detection of parasite DNA are useful in the laboratory. Pentavalent antimony is the conventional treatment; however, resistance of visceral infection in India has spawned new treatment approaches--amphotericin B and its lipid formulations, injectable paromomycin, and oral miltefosine. Despite tangible advances in diagnosis, treatment, and basic scientific research, leishmaniasis is embedded in poverty and neglected. Current obstacles to realistic prevention and proper management include inadequate vector (sandfly) control, no vaccine, and insufficient access to or impetus for developing affordable new drugs.

Effect of LACK and KMP11 on IFN-gamma Production by Peripheral Blood Mononuclear Cells from Cutaneous and Mucosal Leishmaniasis Patients

The immune modulatory properties of recombinant antigens Kinetoplasmid membrane protein-11 (KMP11) and Leishmania homologue of receptors for activated C kinase (LACK) in cutaneous leishmaniasis (CL) and mucosal leishmaniasis (ML) patients were evaluated. The mean levels of interferon-gamma (IFN-gamma) in soluble leishmania antigen (SLA) stimulated peripheral blood mononuclear cells (PBMC) of ML and CL patients were 5625 +/- 2333 pg/ml and 4422 +/- 3665 pg/ml, respectively. IFN-gamma was not detected in cultures stimulated with KMP11 or LACK. Interleukin-10 (IL-10) concentration in SLA, KMP11 and LACK-stimulated PBMC of ML patients was 13 +/- 12 pg/ml, 285 +/- 388 pg/ml and 802 +/- 483 pg/ml, respectively. Addition of KMP11 or LACK to SLA-stimulated PBMC of CL and ML patients enhanced IL-10 production (P < 0.05). Addition of KMP11 decreased IFN-gamma levels by 52% in CL patients and by 19% in ML patients. Addition of LACK to SLA-stimulated cultures decreased IFN-gamma levels by 58% in CL patients and by 30% in ML patients. Neutralization of IL-10 abrogated the downregulatory effect of LACK and KMP11. The modulatory properties of LACK and KMP11 are due to induction of IL-10 production and may be helpful for attenuating chronic inflammatory diseases. However, in some clinical conditions, as demonstrated for ML, these molecules are not able to suppress the IFN-gamma response, even inducing IL-10 production.

Antibody response in patients with cutaneous leishmaniasis infected by Leishmania (Viannia) braziliensis or Leishmania (Viannia) guyanensis in Brazil

The antibody response against Leishmania (Leishmania) amazonensis crude antigen was measured through the indirect immunofluorescent assay (IFA) and the immunoenzymatic assay (ELISA) in 114 patients with cutaneous leishmaniasis (CL) in Brazil. Fifty-four patients were infected by Leishmania (Viannia) braziliensis, and 60 patients had L. (V.) guyanensis infection. Patients were comparable by age, sex, disease duration and the Montenegro skin test diameter. L. (V.) braziliensis-infected patients showed significant lower number of ulcerated lesions, greater ulcerated area and higher proportion of lymph node enlargement. Sensitivity of IFA was 79.6% (95% CI 66.1-88.9) and 71.7% (95% CI 58.4-82.2) for L. (V.) braziliensis and L. (V.) guyanensis-infected patients, respectively (P=0.324). Sensitivity of ELISA was 98.2% (95% CI 88.8-99.9) and 85.0% (95% CI 72.9-92.5) for L. (V.) braziliensis and L. (V.) guyanensis-infected patients, respectively (P=0.018). Significant differences were observed in the magnitude of the antibody response before treatment with higher levels detected in L. (V.) braziliensis-infected patients by both serologic techniques. Eighty-four patients had serologic evaluations before and 12 weeks after treatment with meglumine antimoniate, 20 mg/kg/day for 20 days. Significant lower optic density values were observed after treatment with both species independent of cure or failure. Our data showed that L. (V.) braziliensis induces a higher antibody response against L. (L.) amazonensis antigens than L. (V.) guyanensis and that down-modulation of the antibody response occurs shortly during disease evolution after treatment. Moreover the data support the use of ELISA as a better tool for detection of antibodies in CL.

Itraconazole in the treatment of New World mucocutaneous leishmaniasis

BACKGROUND

A well-tolerated oral drug is required for the treatment of mucocutaneous leishmaniasis (MCL). Current parenteral treatment regimens with pentavalent antimonials are associated with marked toxicity and significant rates of relapse.

AIM

To evaluate the efficacy and tolerability of high-dose itraconazole for the treatment of MCL.

METHODS

An uncontrolled treatment study was performed in 13 Ecuadorian patients with MCL. Each patient received a daily dosage of 400 mg of itraconazole for a minimum of 3 months.

RESULTS

All 13 subjects responded to itraconazole during the first month of treatment, but by 12 months after treatment the complete resolution of MCL lesions was observed in only three (23%) subjects. No adverse effects of treatment were reported. Response to treatment was associated with a short evolution of the disease and mild to moderate disease severity.

CONCLUSION

Prolonged and high-dose treatment regimens with itraconazole are not effective for the treatment of the majority of patients with MCL.

Differential interferon- gamma production characterizes the cytokine responses to Leishmania and Mycobacterium leprae antigens in concomitant mucocutaneous leishmaniasis and lepromatous leprosy

BACKGROUND

Tegumentary leishmaniasis and leprosy display similar spectra of disease phenotypes, which are dependent on cell-mediated immunity to specific antigens. Diffuse cutaneous leishmaniasis and lepromatous leprosy represent the anergic end of the spectrum, whereas mucocutaneous leishmaniasis and tuberculoid leprosy are associated with marked antigen-specific cellular immune response.

METHODS

We characterized and compared the cell-mediated response to Leishmania and Mycobacterium leprae antigens in a patient with an intriguing association of mucocutaneous leishmaniasis with lepromatous leprosy, which are at opposite ends of the immunopathological spectra of these diseases. This was done by performance of skin tests and by assessment of the cell proliferation and cytokine production of peripheral blood mononuclear cells (PBMCs).

RESULTS

Strong skin-test reactions and PBMC proliferation were observed in response to Leishmania antigens but not to M. leprae antigens. The stimulation of PBMCs with Leishmania and M. leprae antigens induced comparable levels of tumor necrosis factor- alpha , interleukin-5, and interleukin-10. However, the interferon- gamma response to Leishmania antigens was remarkably high, and that to M. leprae antigens was almost nil.

CONCLUSIONS

We found that concomitant leprosy and tegumentary leishmaniasis can produce opposite polar forms associated, respectively, with absent or exaggerated cell-mediated immune responses to each pathogen. This suggests that independent mechanisms influence the clinical outcome of each infection. Moreover, interferon- gamma appears to play a major role in the clinical expression of these intracellular infections.

Mecanismos de resposta imune às infecções

O conhecimento dos principais mecanismos de defesa imune contra os diversos agentes infecciosos permite a compreensão da patogênese das doenças infectoparasitárias e das várias estratégias do hospedeiro e do parasita. O sistema imunológico atua numa rede de cooperação, envolvendo a participação de muitos componentes estruturais, moleculares e celulares. Nesse cenário encontra-se o delicado equilíbrio entre a saúde e a doença, em que tanto a deficiência quanto o exagero resultam em dano tecidual. Este artigo explora esses aspectos e algumas abordagens terapêuticas que surgem desse entendimento.

Azithromycin in the treatment of mucosal leishmaniasis

This report describes three elderly patients with mucosal form of American tegumentary leishmaniasis associated with chronic cardiopathy. Due to the known toxicity of classical drugs with activity against Leishmania sp., the patients received three oral courses of azithromycin therapy in single 500 mg daily dose during ten days, every other month. All lesions healed after the third series. One of the patients relapsed and a new series of azithromycin was prescribed. Azithromycin may be an alternative drug for the treatment of leishmaniasis in special situations due to its optimal mucosal and intraphagocyte concentration, single daily posology, high tolerance and oral administration. The mechanism of this drug on Leishmania sp. is unknown at present.

Therapy of Venezuelan patients with severe mucocutaneous or early lesions of diffuse cutaneous leishmaniasis with a vaccine containing pasteurized Leishmania promastigotes and bacillus Calmette-Guerin: preliminary report

Severe mucocutaneous (MCL) and diffuse (DCL) forms of American cutaneous leishmaniasis (ACL) are infrequent in Venezuela. Chemotherapy produces only transitory remission in DCL, and occasional treatment failures are observed in MCL. We have evaluated therapy with an experimental vaccine in patients with severe leishmaniasis. Four patients with MCL and 3 with early DCL were treated with monthly intradermal injections of a vaccine containing promastigotes of Leishmania (Viannia) braziliensis killed by pasteurization and viable Bacillus Calmette- Guerin. Clinical and immunological responses were evaluated. Integrity of protein constituents in extracts of pasteurized promastigotes was evaluated by gel electrophoresis. Complete remission of lesions occurred after 5-9 injections in patients with MCL or 7-10 injections in patients with early DCL. DCL patients developed positive skin reactions, average size 18.7 mm. All have been free of active lesions for at least 10 months. Adverse effects of the vaccine were limited to local reactivity to BCG at the injection sites and fever in 2 patients. Extracts of pasteurized and fresh promastigotes did not reveal differences in the integrity of protein components detectable by gel electrophoresis. Immunotherapy with this modified vaccine offers an effective, safe option for the treatment of patients who do not respond to immunotherapy with vaccine containing autoclaved parasites or to chemotherapy.

Short report: persistence of tumor necrosis factor-alpha in situ after lesion healing in mucosal leishmaniasis

Mucosal leishmaniasis (ML) is a disease characterized by intense activation of inflammatory cells and extensive tissue destruction. Among the cytokines involved in the immune response to ML, tumor necrosis factor-alpha (TNF-alpha) has attracted strong interest because of its roles in the modulation of the immune response. We studied 20 patients with ML who provided biopsy specimens before treatment and after lesion healing obtained by specific therapy. The biopsy specimens were subjected to immunohistochemical analysis for in situ quantification of cellular and extracellular TNF-alpha. The amount of TNF-alpha was significantly lower in the healed lesions compared with pretreatment biopsy specimens, although TNF-alpha persisted at the tissue level even after lesion healing. This relevant finding demonstrates for the first time an in situ tissue reduction of TNF-alpha after treatment and shows persistence of TNF-alpha in healed lesions may be related to the maintenance of an immunopathologic background for relapses observed in ML.

American cutaneous leishmaniasis unresponsive to antimonial drugs: successful treatment using combination of N-methilglucamine antimoniate plus pentoxifylline

BACKGROUND

American cutaneous leishmaniasis is characterized by single or multiple ulcerations. Cytokines, among other factors, have been shown to influence lesion development and tumoral necrosis factor-alpha is a major cytokine implicated in pathogenesis of ulcers.

OBSERVATIONS

We tested oral pentoxifylline, a known tumoral necrosis factor-alpha inhibitor, at doses of 400 mg (2-3x/day), associated to N-methylglucamine antimoniate (15 mg/kg/day) in two patients with American cutaneous leishmaniasis unresponsive to antimonial drugs. We observed a satisfactory response with quick cure of skin lesions of these patients.

CONCLUSIONS

Our results suggest that oral pentoxifylline in association to N-methylglucamine antimoniate should be consider in refractory cutaneous leishmaniasis patients.

Characterization of the immune response to Leishmania infantum recombinant antigens

Leishmaniases have a high prevalence in tropical countries. In order to improve existing diagnostic systems based on total Leishmania proteins, and to identify antigen candidates for vaccine development, an intensive search for the identification of antigens was performed using molecular biology techniques. In this study, the immune response to three L. infantum recombinant antigens was evaluated. Upon stimulation with KMP11, mononuclear cells from leishmaniasis patients produced high levels of IL-10, while a predominant IFN-gamma production could be observed in cultures stimulated with H2A and soluble Leishmania antigen. All the recombinant antigens induced very little IL-5. KMP11 decreased IFN-gamma production by 48% in cultures of peripheral blood mononuclear cells from cutaneous leishmaniasis patients who had been stimulated with soluble Leishmania antigen. Furthermore, antibodies to KMP11 were detected in the sera from all patients with visceral leishmaniasis and in the majority of the sera from patients with cutaneous leishmaniasis or individuals with asymptomatic L. chagasi infection. Thus, KMP11 is recognized by cells and sera of patients with different clinical forms of leishmaniasis, and KMP11, through IL-10 production, proved to be a potent antigen in modulating type 1 immune response.

Advances in the treatment of leishmaniasis

PURPOSE OF REVIEW

Treatment of leishmaniasis is far from satisfactory: all antileishmanial drugs are toxic and most have to be used parenterally for prolonged periods, especially for visceral leishmaniasis. In recent years, there has been a steady erosion in the efficacy of pentavalent antimony to cure visceral leishmaniasis in Bihar, India. In addition, several new antileishmanial formulations have become available.

RECENT FINDINGS

Through the publication of three studies from Africa, generic sodium stibogluconate, which is a fraction of the price of the branded drug Pentostam, has proven to be equivalent to Pentostam both in terms of safety and efficacy. The first oral drug, miltefosine, has been approved for treating visceral leishmaniasis in India, and preliminary reports of its efficacy against cutaneous leishmaniasis have been published. Interesting studies on successful low/single dose treatment of Indian visceral leishmaniasis with liposomal amphotericin B have been published. Several trials using different approaches towards treating cutaneous leishmaniasis are also reviewed. The results of clinical trials of two oral compounds are reported - fluconazole in treating cutaneous leishmaniasis was found to be safe and effective, whereas sitamaquine (WR6026) for visceral leishmaniasis was found to be toxic with poor efficacy.

SUMMARY

Generic stibogluconate enables the cost effective treatment of all forms of leishmaniasis as it remains the most important antileishmanial drug in most parts of the world. In India, successful single dose AmBisome for visceral leishmaniasis makes therapy simple and enables mass treatment, provided the drug cost is brought down. For cutaneous leishmaniasis, two new oral drugs, fluconazole and miltefosine, provide wider options to the clinician.

Up-regulation of Th1-type responses in mucosal leishmaniasis patients

The cytokine profile produced by peripheral blood mononuclear cells (PBMC) in response to leishmania antigens and the ability of interleukin-10 (IL-10) and transforming growth factor beta (TGF-beta) to modulate the immune response were evaluated in 21 mucosal leishmaniasis patients. Patients with mucosal disease exhibited increased gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) secretion and decreased IL-10 secretion compared to patients with classical cutaneous leishmaniasis. CD4(+) Th1 cells were the main source of IFN-gamma and TNF-alpha production in mucosal leishmaniasis patients. Evaluation of cytokine gene expression in PBMC of these patients showed that there was strong up-regulation of IFN-gamma transcripts upon stimulation with leishmania antigen, in contrast to the baseline levels of IL-10 mRNA. IL-10 suppressed IFN-gamma production by 48% in cell cultures from cutaneous leishmaniasis patients and by 86% in cell cultures from healthy subjects stimulated with purified protein derivative, whereas in similar conditions IL-10 suppressed IFN-gamma production by 19% in cell cultures from mucosal leishmaniasis patients stimulated with leishmania antigen. TGF-beta suppressed IFN-gamma levels to a greater extent in healthy subjects than in mucosal leishmaniasis and cutaneous leishmaniasis patients. These data indicate that a poorly modulated T-cell response in mucosal leishmaniasis patients leads to production of high levels of proinflammatory cytokines, such as IFN-gamma and TNF-alpha, as well as a decreased ability of IL-10 and TGF-beta to modulate this response. These abnormalities may be the basis for the pathological findings observed in this disease.

Failure of early treatment of cutaneous leishmaniasis in preventing the development of an ulcer

The clinical characteristics and treatment outcome were determined for 26 patients who presented with early-stage cutaneous leishmaniasis. Illness duration ranged from 8 to 20 days, and the commonest clinical presentation was the presence of a papule with small central crust on a lower extremity. Prominent regional adenopathy was found in 22 (85%) of 26 patients. The results of an intradermal skin test for Leishmania were positive for 96% of those patients, and results of serologic testing were positive for 61% of patients tested. Ten (46%) of 22 patients for whom follow-up data were available developed enlargement and ulceration of the lesion despite early antimony therapy and required additional courses of treatment. Histopathological studies of samples from the lesions of 3 patients showed vasculitis. These data show that early therapy for cutaneous leishmaniasis does not prevent the development of an ulcer in one-half of patients. This unfavorable outcome underlines the relevance of local exacerbated inflammatory and immune response in the pathogenesis of the disease.

Epidemiologic and immunologic findings for the subclinical form of Leishmania braziliensis infection

The epidemiologic and immunologic findings for 104 subjects with subclinical Leishmania braziliensis infection were compared with those for 29 patients with cutaneous leishmaniasis (CL) from the same area of endemicity. Subjects had a positive leishmania skin test result and remained asymptomatic during the next 4 years of follow-up were considered to have subclinical infection. Patients with CL were younger, had larger-diameter indurations after skin testing, and were more likely to have positive serologic markers than were those with subclinical infection (P<.05). In subjects with subclinical infection, levels of interferon-gamma and tumor necrosis factor-alpha in lymphocyte supernatants were lower than they were in patients with CL (P<.05); however, mean interleukin-5 levels were slightly higher in patients with subclinical infection than in patients with CL. These data indicate that, unlike patients with CL, individuals who do not develop disease when infected with L. braziliensis may have the ability to modulate their immune response.

Immune responses to an inactive vaccine against American cutaneous leishmaniasis together with granulocyte-macrophage colony-stimulating factor

The immunological response in healthy subjects to a crude leishmania antigen vaccine (Leishvacin) plus rhGM-CSF without prior Montenegro (DTH) skin testing was evaluated. Fifty-six healthy volunteers received vaccine plus either placebo or rhGM-CSF at day 0, followed by either a vaccine booster or placebo at day 21. IFN-gamma and IL-5 levels were significantly enhanced by day 21. The adjuvant group had a higher percentage of individuals with a significant response to vaccination than the corresponding placebo group. Eighty-six percent of all volunteers were DTH-positive by day 42. Leishvacin is capable of sensitizing lymphocytes from individuals not previously exposed to leishmania antigen. Use of rhGM-CSF enhanced the immune response, indicating that it may improve immunological response to the vaccine.