Leishmania RNA virus exacerbates Leishmaniasis by subverting innate immunity via TLR3-mediated NLRP3 inflammasome inhibition

Leishmania RNA virus (LRV) is an important virulence factor associated with the development of mucocutaneous Leishmaniasis, a severe form of the disease. LRV-mediated disease exacerbation relies on TLR3 activation, but downstream mechanisms remain largely unexplored. Here, we combine human and mouse data to demonstrate that LRV triggers TLR3 and TRIF to induce type I IFN production, which induces autophagy. This process results in ATG5-mediated degradation of NLRP3 and ASC, thereby limiting NLRP3 inflammasome activation in macrophages. Consistent with the known restricting role of NLRP3 for Leishmania replication, the signaling pathway triggered by LRV results in increased parasite survival and disease progression. In support of this data, we find that lesions in patients infected with LRV+ Leishmania are associated with reduced inflammasome activation and the development of mucocutaneous disease. Our findings reveal the mechanisms triggered by LRV that contribute to the development of the debilitating mucocutaneous form of Leishmaniasis.

Promastigote parasites cultured from the lesions of patients with mucosal leishmaniasis are more resistant to oxidative stress than promastigotes from a cutaneous lesion

Human leishmaniasis caused by Leishmania (Viannia) braziliensis can be presented as localized cutaneous leishmaniasis (LCL) or mucosal leishmaniasis (ML). Macrophages kill parasites using nitric oxide (NO) and reactive oxygen species (ROS). The aim of this study was to evaluate the ability of parasites obtained from patients with LCL or ML to produce and resist NO or ROS. Promastigotes and amastigotes from LCL or ML isolates produced similar amounts of NO in culture. Promastigotes from ML isolates were more resistant to NO and H₂O₂ than LCL parasites in a stationary phase, whereas amastigotes from LCL isolates were more resistant to NO. In addition, in the stationary phase, promastigote isolates from patients with ML expressed more thiol-specific antioxidant protein (TSA) than LCL isolates. Therefore it is suggested that infective promastigotes from ML isolates are more resistant to microbicidal mechanisms in the initial phase of infection. Subsequently, amastigotes lose this resistance. This behavior of ML parasites can decrease the number of parasites capable of stimulating the host immune response shortly after the infection establishment.

Leprosy and American cutaneous leishmaniasis coinfection

Brazil is a country with a high prevalence of infectious diseases such as leprosy and leishmaniasis. However, coinfection of these diseases is still poorly understood. We report a case of a patient who presented with lepromatous leprosy and cutaneous-mucosal leishmaniasis at the same period. After clinical, laboratory, and histopathological diagnosis, the treatment was introduced and the patient showed important clinical improvement. He was followed in our outpatient clinic. Both pathologies play an important role in the immune system. Depending on the immune response profile of the host, diseases may present themselves in different ways. In this case, the patient showed a divergent immune response for each disease. We hypothesized that this response is specific for each pathogen.

Clinical and epidemiological features of leishmaniasis in northwestern-Argentina through a retrospective analysis of recent cases

Leishmaniasis is a parasitic disease caused by hemoflagellates of the genus Leishmania and is transmitted to humans by the bite of infected phlebotomine sandflies. Depending on the Leishmania species, the disease has different clinical forms including cutaneous, mucocutaneous, and visceral manifestations. Previous studies performed in endemic zones of northwestern-Argentina, during epidemic outbreaks, have been important for detecting patients suffering from the acute phase of the disease, but have not given a complete representation of the clinical and epidemiological features in the region. Furthermore, due to the resurgence of leishmaniasis worldwide and in particular the large increase of international tourism to the region, it seems pertinent to update the current epidemiological and clinical profile of leishmaniasis in northwestern-Argentina. Here we present a retrospective analysis of 95 Leishmania positive cases, presenting between 2000 and 2014. Patients were derived from hospitals and diagnosed in our lab at the University of Salta, located in a non-endemic area in Salta, Argentina. We detected numerous extensive mucocutaneous cases (34/95, 35.8%) distinct from mucosal affected patients, some instances originating in locations with no previously reported human cases. Additionally patients suffering from concomitant diseases, besides leishmaniasis, were assessed. These included Chagas disease, syphilis, deep mycoses, tuberculosis, toxoplasmosis and intestinal parasitosis. This study updates the clinical and epidemiological features of leishmaniasis in northwestern-Argentina, and discusses the implications and management strategy for patients who acquire the disease in this region.

MyD88 and TLR9 dependent immune responses mediate resistance to Leishmania guyanensis infections, irrespective of Leishmania RNA virus burden

Infections with Leishmania parasites of the Leishmania Viannia subgenus give rise to both localized cutaneous (CL), and metastatic leishmaniasis. Metastasizing disease forms including disseminated (DCL) and mutocutaneous (MCL) leishmaniasis result from parasitic dissemination and lesion formation at sites distal to infection and have increased inflammatory responses. The presence of Leishmania RNA virus (LRV) in L. guyanensis parasites contributes to the exacerbation of disease and impacts inflammatory responses via activation of TLR3 by the viral dsRNA. In this study we investigated other innate immune response adaptor protein modulators and demonstrated that both MyD88 and TLR9 played a crucial role in the development of Th1-dependent healing responses against L. guyanensis parasites regardless of their LRV status. The absence of MyD88- or TLR9-dependent signaling pathways resulted in increased Th2 associated cytokines (IL-4 and IL-13), which was correlated with low transcript levels of IL-12p40. The reliance of IL-12 was further confirmed in IL12AB^−/− mice, which were completely susceptible to infection. Protection to L. guyanensis infection driven by MyD88- and TLR9-dependent immune responses arises independently to those induced due to high LRV burden within the parasites.

[Role of three ELISA tests using promastigote homogenates of Leishmania braziliensis, L. amazonensis and L. guyanensis in the diagnosis of tegumentary leishmaniasis]

It is important to know whether the variability of species of Leishmania parasites circulating in a region affects the performance of the ELISA test for the diagnosis of leishmaniasis. Therefore, the aim of this study was to analyze the reactivity of the ELISA using homogenates of promastigotes of Leishmania (V.) braziliensis (ELISAb), Leishmania (L) amazonensis (ELISAa) and Leishmania (V.) guyanensis (ELISAg) against different sera groups. Samples from individuals with cutaneous leishmaniasis (n = 37), mucocutaneous leishmaniasis (n = 8), healthy controls (n = 52), persons infected with Trypanosoma cruzi (n = 11) and mixed infections (n = 14) were included in the study. We calculated sensitivities, specificities, cut offs, and predictive values for the three tests and compared them using ANOVA, kappa index, ROC curves comparison, and confidence intervals calculated by the bootstrap method. Significant differences were found when comparing the OD levels of sera from patients with cutaneous leishmaniasis against healthy controls, but there were no differences when comparing the different ELISAs. The sensitivities calculated for ELISAb and ELISAa were 84.6 and of 88.5% for ELISAg, while the value of specificity for the three tests was 96.2. The kappa index (0.87) and comparison of ROC curves showed similar performance for the three ELISAs (p = 0.225). The high reactivity obtained for these ELISAs in sera of patients with mucocutaneous leishmaniasis indicates this test as an important complement in the diagnosis of the disease.

The -2518bp promoter polymorphism at CCL2/MCP1 influences susceptibility to mucosal but not localized cutaneous leishmaniasis in Brazil

Mucosal leishmaniasis (ML) follows localized cutaneous leishmaniasis (CL) caused by Leishmania braziliensis. Proinflammatory responses mediate CL self-healing but are exaggerated in ML. Proinflammatory monocyte chemoattractant protein 1 (MCP-1; encoded by CCL2) is associated with CL. We explore its role in CL/ML through analysis of the regulatory CCL2 -2518bp promoter polymorphism in CL/ML population samples and families from Brazil. Genotype frequencies were compared among ML/CL cases and control groups using logistic regression and the family-based association test (FBAT). MCP-1 was measured in plasma and macrophages. The GG recessive genotype at CCL2 -2518bp was more common in patients with ML (N=67) than in neighborhood control (NC; N=60) subjects (OR 1.78; 95% CI 1.01-3.14; P=0.045), than in NC combined with leishmanin skin-test positive (N=60) controls (OR 4.40; 95% CI 1.42-13.65; P=0.010), and than in controls combined with CL (N=60) patients (OR 2.78; 95% CI 1.13-6.85; P=0.045). No associations were observed for CL compared to any groups. FBAT (91 ML and 223 CL cases in families) confirmed recessive association of ML with allele G (Z=2.679; P=0.007). Higher levels of MCP-1 occurred in plasma (P=0.03) and macrophages (P<0.0001) from GG compared to AA individuals. These results suggest that high MCP-1 increases risk of ML.

Leishmania (Viannia) guyanensis induces low immunologic responsiveness in leishmaniasis patients from an endemic area of the Brazilian Amazon Highland

Cutaneous leishmaniasis caused by Leishmania (Viannia) guyanensis (CL-Lguy) is endemic in the Brazilian Amazon, differing from L. braziliensis infection in clinical, diagnostic, and therapeutic aspects. T-cell reactivity to leishmanial antigens possibly involved in the pathogenesis of CL-Lguy was studied herein. Variable lymphoproliferative responses (LPRs) to Leishmania antigens were found among the 23 studied patients, and 50% of them showed low or no response to these antigens. Active disease was associated with an enrichment of leishmanial-reactive T lymphocytes, mainly TCD4(+). High and low interferon (IFN)-gamma producers were observed. TNF-alpha, interleukin (IL)-10, and IL-5 were consistently detected. CL-Lguy displayed low antibody response in comparison to L. braziliensis patients. CL caused by L. braziliensis presented positive LPRs and higher IFN-gamma production but undetectable IL-5. L. guyanensis seems to induce a down-regulation of the immune system compared with L. braziliensis. This finding could explain some aspects of clinical presentation of CL-Lguy, such as high tissue parasite burden and frequent resistance to therapy.

Testing of four Leishmania vaccine candidates in a mouse model of infection with Leishmania (Viannia) braziliensis, the main causative agent of cutaneous leishmaniasis in the New World

We evaluated whether four recombinant antigens previously used for vaccination against experimental infection with Leishmania (Leishmania) major could also induce protective immunity against a challenge with Leishmania (Viannia) braziliensis, the species responsible for 90% of the 28,712 annual cases of cutaneous and mucocutaneous leishmaniasis recorded in Brazil during the year of 2004. Initially, we isolated the homolog genes encoding four L. (V.) braziliensis antigens: (i) homologue of receptor for activated C kinase, (ii) thiol-specific antioxidant, (iii) Leishmania elongation and initiation factor, and (iv) L. (L.) major stress-inducible protein 1. At the deduced amino acid level, all four open reading frames had a high degree of identity with the previously described genes of L. (L.) major being expressed on promastigotes and amastigotes of L. (V.) braziliensis. These genes were inserted into the vector pcDNA3 or expressed as bacterial recombinant proteins. After immunization with recombinant plasmids or proteins, BALB/c mice generated specific antibody or cell-mediated immune responses (gamma interferon production). After an intradermal challenge with L. (V.) braziliensis infective promastigotes, no significant reduction on the lesions was detected. We conclude that the protective immunity afforded by these four vaccine candidates against experimental cutaneous leishmaniasis caused by L. (L.) major could not be reproduced against a challenge with L. (V.) braziliensis. Although negative, we consider our results important since they suggest that studies aimed at the development of an effective vaccine against L. (V.) braziliensis, the main causative agent of cutaneous leishmaniasis in the New World, should be redirected toward distinct antigens or different vaccination strategies.

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

Suitable levels of interferon (IFN)-gamma and interleukin (IL)-10 seem to favour the outcome of cutaneous leishmaniasis (CL), while high IFN-gamma 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-gamma 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-gamma 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-gamma/IL-10 ratio observed in CML can indicate unfavourable cytokine balance. On the other hand, no significant difference in the IFN-gamma/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-gamma/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-gamma/IL-10 balance observed in CCL, SH and ASY individuals can represent a better-modulated immune response associated with a favourable prognosis.

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.

IL-10 producing CD8+ T cells in human infection with Leishmania guyanensis

Cytokines are increasingly recognized as important components of the cellular immune responses to intracellular pathogens. In this study, we analyzed the production of TGF-beta, IL-10 and IFN-gamma by PBMC of unexposed naïve subjects and LCL patients after stimulation with live Leishmania guyanensis (L.g.). We demonstrated that IFN-gamma is produced in controls and LCL patients, IL-10 only in LCL patients and TGF-beta only in naïve subjects. Furthermore, in naive subjects, neutralization of TGF-beta induced IL-10 production. IL-10 produced in naïve subjects when TGF-beta is neutralized or in LCL patients did not modify the IFN-gamma production but inhibit reactive nitrogen species production. Analysis of the phenotype of IL-10 producing cells in naive subjects when TGF-beta is neutralized clearly showed that they are memory CD45RA- CD8+ T cells. In LCL patients, IL-10 producing cells are both CD45RA- CD4 and CD8+ T cells. The role of these IL-10 producing CD8+ T cells in the development of the diseases should be carefully evaluated.

Leishmaniasis

Epidemiology, disease patterns, immunology, diagnosis, treatment and control measures of leishmaniasis are described. Various issues relating to leishmaniasis are highlighted: the relative lack of importance given to this disease compared with other infections, climate change and its possible impact on extension of endemicity of this infection, and new diagnostic tests which are improving diagnosis, especially in resource poor areas. Other important aspects discussed include the potential for newer oral therapy to change the way this disease is managed; Leishmania-HIV coinfection and groups at risk; and development of an effective vaccine.

Selective expression of the V beta 14 T cell receptor on Leishmania guyanensis--specific CD8+ T cells during human infection

Peripheral blood mononuclear cells from subjects never exposed to Leishmania were stimulated with Leishmania guyanensis. We demonstrated that L. guyanensis-stimulated CD8(+) T cells produced interferon (IFN)- gamma and preferentially expressed the V beta 14 T cell receptor (TCR) gene family. In addition, these cells expressed cutaneous lymphocyte antigen and CCR4 surface molecules, suggesting that they could migrate to the skin. Results obtained from the lesions of patients with localized cutaneous leishmaniaisis (LCL) showed that V beta 14 TCR expression was increased in most lesions (63.5%) and that expression of only a small number of V beta gene families (V beta 1, V beta 6, V beta 9, V beta 14, and V beta 24) was increased. The presence of V beta 14 T cells in tissue confirmed the migration of these cells to the lesion site. Thus, we propose the following sequence of events during infection with L. guyanensis. After initial exposure to L. guyanensis, CD8(+) T cells preferentially expressing the V beta 14 TCR and secreting IFN- gamma develop and circulate in the periphery. During the infection, these cells migrate to the skin at the site of the parasitic infection. The role of these V beta 14 CD8(+) T cells in resistance to infection remains to be determined conclusively.

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.

Mucosal Leishmaniasis Patients Display an Activated Inflammatory T-cell Phenotype Associated with a Nonbalanced Monocyte Population

Leishmania braziliensis is a parasite that can induce at least two clinical forms of leishmaniasis in humans: cutaneous leishmaniasis (CL) and mucosal leishmaniasis (ML). In humans, the specific mechanisms that determine which form will develop following infection are not well established. In this study, peripheral blood mononuclear cells from 17 CL and 9 ml patients were compared both ex vivo and after culture with soluble leishmania antigen (SLA). Patients with ML presented a higher frequency of activated T cells as measured by ex vivo frequencies of (CD4+)(CD69+), (CD4+)(CD28-), (CD4+)(CD62L-) and (CD8+)(CD69+) than those with CL. Moreover, after stimulation with SLA, patients with ML presented a higher frequency of TNF-alpha-producing CD4+ and CD14+ cells than CL individuals. While CL patients displayed a positive correlation between the frequency of IL-10 and TNF-alpha-producing monocytes, the ML patients did not. This lack of a positive correlation between IL-10-producing and TNF-alpha-producing monocytes in ML patients could lead to a less controlled inflammatory response in vivo. These results corroborate with a model of an exacerbated, unregulated, immune response in ML patients and point to key immunomodulatory leucocyte populations and cytokine networks that may be involved in the development of immunopathology in ML patients.

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.

OBJECTIVES

In this report flow cytometry was used to determine the predominant T-cell subsets in leishmaniasis lesions, and their relationship with Leishmania-responsive circulating T cells.

PATIENTS AND METHODS

Mononuclear cells from lesions or peripheral blood (PBMC) of 34 cutaneous (CL), four mucosal (ML) and four disseminated leishmaniasis were phenotypically characterized by flow cytometry. Leishmania-responsive T cells were obtained after in vitro stimulation of PBMC with leishmanial antigens.

RESULTS/CONCLUSIONS

Variable amounts of gammadelta lymphocytes were present in all lesions, with no association with duration of illness. The highest percentages of interleukin-2R- and interferon-gammaR-positive cells were observed in ML lesions and could render these T cells more susceptible to the effects of these cytokines. The distribution of intralesional T-lymphocyte subsets was quite variable (CD4+ > CD8+ = 18 cases, CD8+ > CD4+ = 12 cases and CD4+ congruent with CD8+ = 4 cases) without any association with clinical parameters, and could explain the controversy regarding proportions of these T-cell subsets in leishmaniasis lesions. Low percentages of Leishmania-reactive CD8+ T cells were observed in blood while an enrichment of CD8+ cells was shown in the inflammatory infiltrate, suggesting that local immunoregulatory factors could favour the recruitment and/or proliferation of local CD8+ lymphocytes. Increased percentages of CD8+ cells observed in older lesions are consistent with the hypothesis that they can mediate healing, although their involvement in tissue damage cannot be ruled out. It is possible that these mechanisms can influence the clinical outcome or even the response to therapy.

Transforming growth factor beta 1 production by CD4+ CD25+ regulatory T cells in peripheral blood mononuclear cells from healthy subjects stimulated with Leishmania guyanensis

Transforming growth factor beta (TGF-beta) has been shown to be a central immunomodulator used by leishmaniae to escape effective mechanisms of protection in human and murine infections with these parasites. However, all the information is derived from studies of established infection, while little is known about TGF-beta production in response to Leishmania stimulation in healthy subjects. In this study, TGF-beta1 production was demonstrated in peripheral blood mononuclear cells from healthy subjects never exposed to leishmaniae in response to live Leishmania guyanensis, and the TGF-beta1-producing cells were described as a distinct subpopulation of CD4(+) CD25(+) regulatory T cells. The suppressive properties of CD4(+) CD25(+) T cells were demonstrated in vitro by their inhibition of production of interleukin 2 (IL-2) and IL-10 by CD4(+) CD25(-) T cells in the presence of either anti-CD3 or L. guyanensis. Although neutralization of TGF-beta1 did not reverse the suppressive activity of CD4(+) CD25(+) T cells activated by anti-CD3, it reversed the suppressive activity of CD4(+) CD25(+) T cells activated by L. guyanensis. Altogether our data demonstrated that TGF-beta1 is involved in the suppressive activity of L. guyanensis-stimulated CD4(+) CD25(+) T cells from healthy controls.

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.

Leishmania (Viannia) braziliensis-induced chronic granulomatous cutaneous lesions affecting the nasal mucosa in the rhesus monkey (Macaca mulatta) model

The present studies on infections with Leishmania (Viannia) braziliensis in rhesus macaques were made to characterize the evolution of different parasite strains and the immune responses they elicited in this experimental host. A standardized inoculum of promastigotes was injected intradermally either above the eyelid or on the forearm of each monkey. Sixteen infected monkeys developed longstanding infections which lasted until the end of the observation period (33 months). The time required for lesion development was very variable, not only for the isolates showing molecular differences but also for individual animals in groups infected with the same parasite strain. The inocula produced lesions of variable severity, ranging from localized cutaneous leishmaniasis (CL) with a tendency to spontaneous healing to non-healing disease. One infected animal developed persistent metastatic skin and mucosal lesions. Anti-Leishmania antibodies and parasite-specific T-cell responses were induced by the experimental infections. As the granulomatous inflammatory response found at the lesions in L. (V.) braziliensis-infected M. mulatta was similar to that in patients with CL, this primate model could be useful for studying the pathophysiology and immunoregulatory events associated with disease evolution, as well as for the evaluation of new drugs or candidate vaccines.

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.

Increased production of interferon-gamma by Leishmania homologue of the mammalian receptor for activated C kinase-reactive CD4+ T cells among human blood mononuclear cells: an early marker of exposure to Leishmania?

A prospective study was undertaken to define early predictive immunological marker(s) of exposure to Leishmania in naïve subjects who have never been exposed to any Leishmania and who were also free of any cutaneous leishmaniasis lesions. These naïve subjects could have been exposed to Leishmania in a rain forest where Leishmania guyanensis and their natural vectors and mammalian host are cocirculating. The production of interferon (IFN)-gamma in response to the Leishmania homologue of the mammalian receptor for activated c kinase (LACK), a candidate for vaccine against leishmaniasis was analysed. At the end of their stay in the rain forest, LACK-specific CD8+ T cells were detected in subjects whose peripheral blood mononuclear cell (PBMC) produced IFN-gamma in response to soluble Leishmania antigens (SLA) and in those whose PBMC remained unresponsive to SLA. However, LACK-specific CD4+ T cells were detected only in PBMCs from individuals who became IFN-gamma responders to SLA. In subjects whose PBMC became positive to SLA, LACK-reactive CD4+ T cells producing high level of IFN-gamma were detectable before the SLA-reactive IFN-gamma producing CD4+ T cells, suggesting that the former readout assay could be used as an early predictive immunological marker of exposure to Leishmania in subjects who remained disease free.

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.

Characterizing cellular immune response to kinetoplastid membrane protein-11 (KMP-11) during Leishmania (Viannia) panamensis infection using dendritic cells (DCs) as antigen presenting cells (APCs)

In vitro peptide binding assays and DCs pulsed with recombinant KMP-11 (rKMP-11) plus six 20-mer overlapping peptides covering the entire protein of Leishmania (Viannia) panamensis (L(V)p) promastigotes were used to identify T-cell epitopes in this protein. Such in vitro binding assays, using HLA DRB1* 0101, -0401, -0701 and -1101 alleles, demonstrated that two peptide sequences (DEEFNKKMQEQNAKFFADKP and FKHKFAELLEQQKAAQYPSK) exhibited high HLA DRB1* 0401 allele binding capacity. rKMP-11 specific T-cell proliferation and cytokine production, derived from 13 volunteers exposed to the parasite, suggested that using autologous DCs as APCs becomes advantageous in uncovering T-cell epitopes promoting proliferation and differences in IFN-gamma and IL-4 production in T-cells from volunteers with ACTIVE and CURED undetectable disease when other APCs were used. The two peptides which bound in vitro to the HLA DRB1* 0401 allele were immunogenic in HLA DRB1* 04 volunteers, thus validating the use of in vitro binding assays for predicting epitopes in this protein. The experimental approach used here may prove useful for characterizing T-cell epitopes in a protein useful in designing peptide-based vaccine candidates for Leishmania and other intracellular pathogens.

The site of cutaneous infection influences the immunological response and clinical outcome of hamsters infected with Leishmania panamensis

We determined that the site of inoculation (foot or snout) influences the clinical evolution and immune responses of hamsters infected with Leishmania (Viannia) panamensis. Hamsters infected in the snout showed (i) a more rapid and severe lesion evolution at multiple time points (P < 0.05), (ii) a more extensive inflammatory infiltrate and tissue necrosis, (iii) a higher tissue parasite burden, (iv) a higher antibody titre (P < 0.01), but lower antigen-specific spleen cell proliferative response (P = 0.02), and (v) a slower response to anti-leishmanial drug treatment (P < 0.002). In both inoculation groups there was co-expression of type 1 (IFN-gamma and IL-12) and some type 2 (IL-10 and TGF-beta, but not IL-4) cytokines in the cutaneous lesions and spleen. Early in the course of infection, hamsters infected in the snout showed higher expression of splenic IL-10 (P = 0.04) and intra-lesional IFN-gamma (P = 0.02) than foot infections. No expression of IL-12p40 or IL-4 was detected. During the chronic phase, snout lesions expressed more IFN-gamma (P = 0.001), IL-12p40 (P = 0.01), IL-10 (P = 0.009) and TGF-beta (P = 0.001), and the level of expression of each of these cytokines correlated with lesion size (P < or = 0.01). These results suggest that the site of infection influences the clinical outcome in experimental cutaneous leishmaniasis, and that the expression of macrophage-deactivating type 2 cytokines and/or an exaggerated type 1 proinflammatory cytokine response may contribute to lesion severity.

Mucosal leishmaniasis: in situ characterization of the host inflammatory response, before and after treatment

Mucosal leishmaniasis (ML) generally shows progressive tissue destruction, not yet fully elucidated, associated with an intense inflammatory response. To contribute to the understanding of this process and of how treatment interferes with it, we studied several anatomopathological parameters, including those analyzed by immunohistochemistry, such as Leishmania antigens, cells participating in the immune response and cytokine expression. Biopsies were taken from 20 patients with ML before and after treatment. A mixed Th1 and Th2 pattern response occurred inside ML before treatment, persist after treatment. Nevertheless, this mixed response was smaller than in active lesions, with reduced but present numbers of cells expressing TNF-alpha, IFN-gamma and IL-4 and sustained numbers of cells expressing IL-10. We may conclude that specific treatment causes a reduction of inflammatory lesions and disappearance of amastigote forms of Leishmania although the factors related to the pathogenesis of the lesion, such as T CD4+ and T CD8+ lymphocytes and Leishmania antigens, persist in treated lesions. The maintenance of these inflammatory patterns may be due to a specific host-parasite relationship response, strongly indicating the need for continuous surveillance of LM patients at risk of reactivation, despite effective cicatrization after therapy.

Disseminated leishmaniasis: a new and emerging form of leishmaniasis observed in northeastern Brazil

During the past decade, there has been an increase in the number of patients with disseminated leishmaniasis (DL), which is characterized by a large number of acneiform and papular skin lesions, with very few or no parasites in the skin tissue. The present report describes 42 cases of DL identified between 1992 and 1998 in an area where Leishmania braziliensis transmission is endemic; 8 of the patients were prospectively diagnosed. In a contrast to localized cutaneous leishmaniasis (LCL), acquisition of DL was associated with age >19 years (P<.05), male sex (P<.05), and agricultural occupation (P<.001). Patients with DL presented with 10-300 lesions that were a mixture of acneiform, papular, nodular, and ulcerated types. Twelve (29%) of 42 patients had mucosal involvement. Patients with DL had lower levels of interferon-gamma (P<.05) and tumor necrosis factor-alpha (P<.05) production, compared with patients with LCL. DL is an emerging clinical distinct form of leishmaniasis associated with agricultural activities and host immunological response.

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.

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.

LACK-specific CD4(+) T cells that induce gamma interferon production in patients with localized cutaneous leishmaniasis during an early stage of infection

The profile of cytokines induced by soluble leishmania antigen (SLA) and the Leishmania homologue of the mammalian receptor for activated C kinase (LACK), a candidate vaccine against leishmaniasis, and the cellular source of the cytokines produced in response to these antigens were analyzed in patients infected with Leishmania guyanensis. Gamma interferon (IFN-gamma) and interleukin-10 (IL-10) were produced in response to LACK. Although LACK-specific CD4(+) cells producing IFN-gamma were isolated only during the early phase of infection (less than 30 days following the onset of infection), cells producing IL-10 in response to LACK were detected in all patients. CD4(+) T cells producing IFN-gamma and IL-13 were produced in response to SLA in all patients. SLA- and LACK-specific T cells are effector memory cells, as they are CD45RA(-) CCR7(-) CD4(+) T cells. CD4(+) T cells producing IFN-gamma are CD62L(-), and CD4(+) T cells producing IL-10 are CD62L(+), indicating that these cells have different tissue-homing capacities. These findings show that SLA and LACK induce both type 1 (IFN-gamma) and type 2 (IL-10 or IL-13) cell responses.

Technetium-99m labeling anti-amastigote polyclonal antibodies of Leishmania amazonensis

Anti-amastigote polyclonal antibody (IgG) was incubated with solutions of stannous chloride and sodium borohidride. After that, 3.7 MBq of technetium-99m (99mTc) was added. A labeling yield of the antibody about 84% was obtained. After filtration of 99mTc-IgG, the radiochemical purity increased from 84 to 95%. The labeling of IgG with 99mTc did not modify the immunoreactivity of the antibody, since it was able to identify in vitro and in vivo the specific antigen of Leishmania amazonensis.

Parasitological and immunological follow-up of American tegumentary leishmaniasis patients

A long-term evaluation of human American tegumentary leishmaniasis patients was conducted to detect immunological and/or parasitological indicators associated with cure or protection against leishmaniasis. Cutaneous leishmaniasis (CL) and mucosal leishmaniasis (ML) patients from endemic areas of Leishmania braziliensis infection in Brazil were studied during the active disease, at the end of therapy, and up to 10 years after the end of therapy. For immunological studies, lymphocyte proliferative responses, phenotypic characterization of CD4+ and CD8+ T cells reactive to L. braziliensis and cytokine production in vitro were assayed. In CL, with its tendency for healing lesions, at or shortly after the completion of therapy the ratio of CD4+ to CD8+ T cells was approximately one and production of interferon gamma (IFN gamma) remained roughly constant. In ML, these apparently beneficial CD4+/CD8+ ratios and cytokine patterns appeared later. The long-term memory T cell responses were associated with preferential induction of CD4+ subpopulations and IFN gamma production that probably led to protection against relapses or reinfection. Deoxyribonucleic acid (DNA) was isolated from peripheral blood and oligonucleotides that amplify the conserved region of the minicircle molecules of Leishmania were used in a 'hot-start' polymerase chain reaction (PCR). Leishmania DNA was found in about one-quarter of the patients with active disease as well as in individuals who had received chemotherapy. The PCR was also positive in one-third of the individuals with a positive skin test but no past or present history of leishmaniasis. The well-modulated T cell response leading to long-term protection observed in CL patients could result from a favourable host genetic background and/or a particular parasite genotype, leading to a beneficial T cell immune response even in the presence of parasite antigens. The possibility of parasite persistence after clinical cure suggests that the immune response can control, but not fully eliminate, the infection. It could prevent the parasite from causing disease, maintaining a leishmanial antigen-specific response and hampering reinfection.

T-cell-mediated immune responses in patients with cutaneous or mucosal leishmaniasis: long-term evaluation after therapy

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-gamma) and interleukin-5 (IL-5) production during the period of study. Patients with active ML presented higher IFN-gamma 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-gamma, 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.

IFN-gamma-producing CD45RA+CD8+ and IL-10-producing CD45RA-CD4+ T cells generated in response to LACK in naive subjects never exposed to Leishmania

Leishmania guyanensis (L.g.)-specific CD8+ T cells can be isolated from PBMC of subjects who have never been previously exposed to Leishmania. Cells that produce IFN-gamma in response to live L.g. are generated from naive CD45RA+CD8+ T cells. The generation of L.g.-specific CD8+ T cells requires the presence of whole L.g. or UV-irradiated parasite but not the soluble antigens from L.g. promastigotes. The IFN-gamma-producing T cells recognize a specific antigen, the Leishmania homologue of receptors of activated C kinases (LACK) and this antigen but not live L.g. can produce a strong IL-10 response in CD45RA-CD4+ memory T cells from naive subjects. A single epitope (amino acid 156-173) is found to induce the IL-10 synthesis. While the IFN-gamma-producing cells are present among CD45RA+CD8+ T cells that are CD62L-CDR7- and CLA-, the LACK-reactive IL-10-producing cells are CD4+ T cells that are CD62L+CCR7- and CLA-.

Immunological selection for Leishmania (Viannia) braziliensis antigens

Comparative ELISA and selective immunoblotting procedures were used in attempts to identify differential serological indicators of infection with the Leishmania (Viannia) braziliensis complex, infection with the L. braziliensis species, and therapeutic cure of localized or mucocutaneous leishmaniasis (LCL or MCL). Although mean ELISA absorbance values were significantly higher for MCL sera than for LCL sera, absorbance could not be used as a reliable indicator of the clinical form of disease. Immunoblotting profiles were similar with sera from MCL and LCL. Pre-adsorption with heterologous trypanosomatid antigens indicated that recognition of antigens of about 56, 60, 66, 72, 88 and 110 kDa might be specific to the subgenus Viannia. In two-colour, sequential, dual ELISA-based immunoblotting, no antigens recognized only by sera from MCL patients were detected. After glucantime therapy, immunoblotting profiles with LCL sera were reduced both in intensity and in the range of antigens detected; a 104-kDa antigen was newly detected with post-treatment LCL sera. Overall, the results show the value of differential immunological detection strategies and support the close relationship between species of the subgenus Viannia but fail to indicate a prognostic antigen for MCL.

[Mucocutaneous leishmaniasis in naturally infected dogs in Salta, Argentina]

The objective of the present study is to describe two cases of dogs with mucocutaneous lesions caused by Leishmania spp. Both dogs presented destruction of the nasal septum, hyperemia with soft palate edema and barking alteration due to laryngeal compromise. Biopsies were taken from the lesion border and Leishmania spp. amastigotes were seen in the imprints. The dogs presented positive serology when complex soluble antigen from Leishmania mexicana was used. One of the dogs was also suspected to be infected by Trypanosoma cruzi as suggested by its positive reaction with a purified specific antigen, Ag163B6-cruzipain. Most of the studies concerning leishmaniosis in dogs have described the cutaneous form of this disease in close association with human cases of Leishmania infection instead of the mucocutaneous form described herein. The presence of dogs with mucocutaneous leishmaniosis alerts on an increase of the prevalence of this form in humans, which can cause deforming lesions, alterations of the speech and even an inadequate nutrition due to difficulties in deglutition.

Distinct innate and acquired immune responses to Leishmania in putative susceptible and resistant human populations endemically exposed to L. (Viannia) panamensis infection

Mechanisms of constitutive and acquired susceptibility/resistance to Leishmania Viannia panamensis (L. (V ) p.) were investigated in endemically exposed human populations presenting either recurrent disease (putative susceptible) or subclinical infection (clinically resistant). Cutaneous delayed type hypersensitivity response to leishmanin was significantly lower among individuals experiencing recurrent leishmaniasis than among those whose skin test converted without developing the disease. Monocyte derived macrophages from individuals with recurrent disease were more permissive in vitro to the entry of parasites than macrophages from subclinically infected individuals. In vitro proliferation of CD4 and CD8 T lymphocytes in response to intracellular amastigotes was significantly lower among individuals with a history of recurrent disease compared with subclinically infected individuals. Linear regression analyses revealed a strong direct relationship between the production of interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha and interleukin (IL)-10 by peripheral blood mononuclear cells (PBMC) from resistant (subclinically infected) individuals and no correlation in the production of these cytokines by PBMC from individuals who experienced recurrent disease. The results provide evidence of differences in the innate and acquired responses to Leishmania according to the outcome of the natural infection. These findings support the feasibility of identifying the immunological bases of innate and acquired resistance through studies in naturally exposed human populations.

Immunotherapy with live BCG plus heat killed Leishmania induces a T helper 1-like response in American cutaneous leishmaniasis patients

Previous work has shown that American cutaneous leishmaniasis (ACL) patients treated with viable BCG plus heat killed promastigotes of Leishmania amazonensis show the same rate of cure as patients receiving conventional chemotherapy. The treatment is safe and economical, but the immunological correlates of cure have not been examined. In the present study, T cell responses have been analysed in 43 ACL patients, including patient groups sampled before and after therapy, and in 10 endemic controls. Lymphocyte proliferation, interferon (IFN)-gamma and interleukin (IL)-5 responses to crude antigen (L. amazonensis, MEL; Mycobacterium tuberculosis PPD; M. bovis BCG) stimulation, and serum IL-5 levels, were analysed. In endemic volunteers, proliferative responses to BCG were high and IFN-gamma responses low. In contrast, localized cutaneous (LCL) and mucocutaneous (MCL) patients showed low proliferative and high IFN-gamma responses to BCG. Treatment enhanced the IFN-gamma response and further decreased the proliferative response to BCG, especially in MCL patients. LCL and MCL patients showed an increase in proliferative and IFN-gamma responses to MEL with treatment, but the response was not exaggerated in MCL patients, either before or after treatment, compared to LCL patients. IL-5 production was low in T cell assays, and > 62% of untreated patients had very low serum IL-5 levels. There were no significant changes in serum IL-5 with treatment. Overall results show enhanced antigen-specific IFN-gamma responses to the two components of the immunotherapy, live M. bovis BCG and heat killed L. amazonensis, which is consistent with a shift in balance of T cell response towards a T helper 1 response and clinical cure mediated by IFN-gamma.

Mucosal leishmaniasis: quantitative nasal cytology as a marker of disease activity and indicator of healing

Mucosal leishmaniasis (ML) follow-up is based on subjective parameters. Using simplified quantitative cytology of nasal lavages (QNCs), we studied 20 ML patients, 10 patients with cutaneous leishmaniasis (CL), and 10 healthy subjects. Patients with ML were treated with antimony and followed up with otolaryngological examination plus QNCs for 6 months. At the first evaluation, the median total number of cells in ML patients (1,540,000) was greater than that in CL patients (215,000) or that in healthy subjects (250,000). Neutrophils were predominant in ML patients, in contrast to both sets of controls, in whom epithelial cells were more frequent. During treatment, we found a significant reduction in total nasal cell counts in ML patients who were cured, and encountered a switch in predominant cell type. The cytology of 2 patients who did not respond to antimony remained the same. It is therefore possible to detect nasal inflammation in ML patients through QNCs, which may indicate extension of mucosal involvement, providing an objective parameter to monitor therapy.

Humoral immune responses among mucosal and cutaneous leishmaniasis patients caused by Leishmania braziliensis

Mucosal leishmaniasis is arguably the most morbid sequelae of cutaneous leishmaniasis. The importance of early diagnosis for effective therapy, coupled with the difficulty of diagnosing the disease parasitologically, prompted this investigation of humoral immune markers of mucosal disease. Promastigote soluble antigens of Leishmania braziliensis, isolated from cutaneous and mucosal lesions, were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis; antigens were identified by immunoblotting with parasite-specific IgG antibody-positive sera of patients with mucosal disease (n = 18) and cutaneous disease (n = 23). For antigens of the cutaneous parasite WR 2095, mucosal sera generally reacted intensely to antigens of 75, 66, and 45 kDa and weakly to 48-50-kDa antigens, whereas cutaneous sera generally detected weakly the first 3 antigens and intensely the latter doublet. The data suggest that the transition from the cutaneous antigenic profile to a mucosal antigenic profile could be used to predict mucosal disease in approximately half of mucosal patients. An additional finding was that antibodies present in the sera of patients with mucosal disease labeled a 66-kDa peptide of normal human lip mucosa more intensely than did cutaneous sera. Autoimmune processes stimulated by the reaction of IgG, originally directed against the 66-kDa of L. braziliensis, to the 66-kDa antigen of mucosal tissue may contribute to the clinical presentation of mucosal leishmaniasis.

Persistence of Leishmania antigen in C57Bl/6j inbred mice infected with Leishmania (Leishmania) amazonensis

PURPOSE

To develop an animal model for studying mucocutaneous leishmaniasis.

METHODS

The hind footpad of C57Bl/6j inbred mice was experimentally infected with 10(7) Leishmania (Leishmania) amazonensis promastigote and the skin was studied through light and electron transmission microscopy and immunohistochemistry (PAP) techniques.

RESULTS

There were morphological evidences of cellular immune mechanisms and hypersensitivity reaction after eight weeks of infection and metastasis and well shaped parasites at ultrastructural level by fifty-one weeks post infection. Relapse of infection with mucosa lesions occurred around the 50th week after inoculation.

CONCLUSION

The use of this animal model in long term follow up could be an useful experimental model for human mucocutaneous leishmaniasis.

Atypical mucocutaneous leishmaniasis caused by Leishmania braziliensis in an acquired immunodeficiency syndrome patient: T-cell responses and remission of lesions associated with antigen immunotherapy

An atypical case of acquired immunodeficiency syndrome-associated mucocutaneous lesions due to Leishmania braziliensis is described. Many vacuolated macrophages laden with amastigote forms of the parasite were found in the lesions. Leishmanin skin test and serology for leishmaniasis were both negative. The patient was resistant to therapy with conventional drugs (antimonial and amphotericin B). Interestingly, remission of lesions was achieved after an alternative combined therapy of antimonial associated with immunotherapy (whole promastigote antigens). Peripheral blood mononuclear cells were separated and stimulated in vitro with Leishmania antigens to test the lymphoproliferative responses (LPR). Before the combined immunochemotherapy, the LPR to leishmanial antigens was negligible (stimulation index - SI=1.4). After the first course of combined therapy it became positive (SI=4.17). The antigen responding cells were predominantly T-cells (47.5%) most of them with CD8+ phenotype (33%). Very low CD4+ cells (2.2%) percentages were detected. The increased T-cell responsiveness to leishmanial antigens after combined therapy was accompanied by interferon-g (IFN-g) production as observed in the cell culture supernatants. In this patient, healing of the leishmaniasis lesions was associated with the induction of a specific T-cell immune response, characterized by the production of IFN-g and the predominance of the CD8+ phenotype among the Leishmania-reactive T-cells.

Susceptibility and resistance to Leishmania amazonensis in H-2q syngeneic high and low antibody responder mice (Biozzi mice)

H-2 syngeneic H and L (Biozzi) mice provide a model to study Leishmania infections in which polar resistant and susceptible phenotypes are independent from H-2 differences. High-Ab-responder (H) and low-Ab-responder (L) mice syngeneic at the H-2 locus (H-2q) were, respectively, susceptible and highly resistant to Leishmania amazonensis infection. L-mice resistance was associated with high IFN-gamma and transient IL-4 production by lymph node (LN) cells, in contrast with sustained IL-4 and decreasing IFN-gamma production by susceptible H mice. IL-12 production could be detected only in LN from resistant mice. The cytokine production pattern was consistent with preferential progression to a Th1-type response in resistant L-mice, and to a Th2-type response in susceptible H-mice. We also investigated whether this shift towards Th1- or Th2-type cytokine responses was dependent upon H or L antigen presenting cells' (APC) intrinsic ability to preferentially stimulate either T-cell subset. To this end, LN-derived T-cell lines were grown from 12-day infected mice, when both strains produced IFN-gamma and IL-4. L-derived T-cell lines developed a Th2 cytokine pattern whereas H-derived T-cell lines produced IFN-gamma, IL-4 and IL-10 whatever the APC origin (H or L) used for their derivation. This work constitutes the first characterization of cellular immune responses to the intracellular parasite, L. amazonensis in H-2 syngeneic mice, an infection model in which polar resistant and susceptible phenotypes are determined by non-MHC genes.

Parasite-driven in vitro human lymphocyte cytotoxicity against autologous infected macrophages from mucosal leishmaniasis

Parasite-specific cytotoxicity in human leishmaniasis was evaluated in an autologous system. PBL from cutaneous leishmaniasis (CL) or mucosal leishmaniasis (ML) patients were exposed to Leishmania amazonensis-infected autologous macrophages for 7 days and then used as effector cells in a cytotoxic assay using 51Cr-labeled autologous infected macrophages as targets. Results are reported as LU per 10(7) PBMC. Cytotoxic activity is present in ML (9.7 +/- 2.1 LU/10(7) PBMC) but not in CL (1.5 +/- 2.4 LU/10(7) PBMC) patients' lymphocytes, and the differences were highly significant (p < 0.0001). Both CD8+ T cells and NK cells exhibited cytotoxic activity. Addition of rIL-12, but not of IFN-gamma, during the generation of effector cells increased cytotoxic responses against infected macrophages. On the other hand, addition of mAb against human IL-12 or IFN-gamma during the stimulation of PBL significantly decreased the cytotoxic responses. Addition of IL-10 led to diminished cytotoxic responses, whereas the addition of anti-IL-10 did not significantly increase the cytotoxic responses. The observation of parasite-driven autologous cytotoxic responses in patients with ML, the destructive form of leishmaniasis, but not in CL, suggests that this phenomenon is involved in tissue pathology rather than in protection. Understanding the regulation of cytotoxic responses in leishmaniasis may be relevant to strategies aimed at limiting pathologic tissue destruction.

The IgG isotypes of specific antibodies in patients with American cutaneous leishmaniasis; relationship to the cell-mediated immune response

American cutaneous leishmaniasis (ACL) presents a spectrum of clinical and immunological manifestations. Since the nature of the cellular response appears to play a fundamental role in determining the characteristics of the immunoglobulin isotype of specific antibody responses, we have compared the relative levels of specific antibodies of the four IgG isotypes against Leishmania in sera from patients with different clinical manifestations of ACL. Using a specific antibody capture assay, significant levels of antibodies of the IgG1, 2 and 3 isotypes were detected in localized cutaneous leishmaniasis (LCL); the average level of IgG4 antibodies was low and they were not detected in 10/20 sera. Sera from muco-cutaneous leishmaniasis (MCL) gave a comparatively strong IgG1 response. Sera from diffuse cutaneous leishmaniasis (DCL), the rare form characterized by antigen-specific anergy of cell-mediated immunity, showed highly significant levels of IgG4 antibodies compared to antibody levels of this isotype in the other groups; IgG1 and IgG2 levels were also elevated. Based on other studies of the relationship between the IgG isotype response and cell-mediated immunity, these results confirm a Th1-like CD4+ T cell response in LCL and MCL and a significant Th2-like response in DCL.