Transforming growth factor-beta in human cutaneous leishmaniasis

Transforming growth factor (TGF)-beta has several downregulatory functions on the immune system: inhibition of interleukin-2 receptor induction, decrease of interferon-gamma-induced class II antigen expression, inhibition of macrophage activation, as well as cytotoxic and lymphokine-activated killer cell generation. TGF-beta has also been recognized as an important immunoregulator in murine leishmaniasis, for which it increases susceptibility to disease. In the present study we evaluate the involvement of TGF-beta in human leishmaniasis in vitro and in patients with cutaneous leishmaniasis. Human macrophages produce active TGF-beta after infection by Leishmania amazonensis (480 +/- 44.7 pg/ml; mean +/- SEM), L. donovani chagasi (295 +/- 7.6 pg/ml), or L. braziliensis (196 +/- 15.7 pg/ml). When TGF-beta was added to cultures of human macrophages infected with L. braziliensis it led to an increase of approximately 50% in parasite numbers as compared with untreated cultures. Exogenous TGF-beta added to macrophage cultures was able to reverse the effect of interferon-gamma in controlling Leishmania growth. Even at 100 IU/ml interferon-gamma the presence of TGF-beta increases the number of intracellular parasites. On the other hand, TNF-alpha at high concentration (100 IU/ml) totally blunts the suppressive effect of TGF-beta. Immunostaining for TGF-beta was observed in the dermis, produced by fibroblasts and occasionally by inflammatory cells in the biopsies from human leishmaniasis lesions, being present in most of the biopsies taken from patients with early cutaneous leishmaniasis (less than 2 months of ulcer development) and in cases of active mucosal leishmaniasis. Taken together these observations suggest an important role for TGF-beta in human leishmaniasis, with its production by infected macrophages being probably related to parasite establishment in the early stages of the disease.

Immune responses of leishmaniasis patients to heat shock proteins of Leishmania species and humans

The course of human infection with Leishmania braziliensis is variable, ranging from self-healing infection to chronic disease. It is therefore a useful system in which to study immunoregulatory aspects of leishmaniasis, including the effects of parasite antigens on host responses. In the present study, we report on the cloning of, expression of, and comparative analyses of patient immune response to two different L. braziliensis genes homologous to the genes for the eukaryotic 83- and 70-kDa heat shock proteins. rLbhsp83 contains a potent T-cell epitope(s) which stimulated peripheral blood mononuclear cells (PBMC) from all L. braziliensis-infected individuals to proliferate and to produce interleukin-2 (IL-2) gamma interferon, and tumor necrosis factor alpha. The elicitation of IL-4 and IL-10 mRNAs was found to differ depending on the portion of the rLbhsp83 used to stimulate PBMC. rLbhsp83a, which represents the nearly full-length protein, stimulated IL-10 but not IL-4 mRNA. In contrast, a approximately 43-kDa protein representing the C-terminal region of Lbhsp83 stimulated the production of IL-4 but not IL-10 mRNA. rLbhsp70 stimulated PBMC proliferation from patients with mucosal disease but, unlike rLbhsp83, did not stimulate PBMC from self-healing individuals. PBMC from mucosal patients were not stimulated by rHuhsp70 to either proliferate or produce cytokines. This suggests that the hyperresponsiveness of mucosal patient PBMC to Leishmania heat shock proteins does not involve an auto-immune phenomenon resulting from cross-reactivity with self hsp70. In general, although the cytokine profile of patient PBMC in response to both of these Leishmania heat shock proteins represents a mixed Th1-Th2 pattern, the levels of gamma interferon and IL-2 were significantly higher than those of the Th2 cytokines IL-4 and IL-10. Patients with active mucosal and cutaneous disease but not self-healing individuals had significant anti-immunoglobulin G antibody titers to both rLbhsp83 and rLbhsp70 but not to the homologous rHuhsp70. It therefore appears that differential patient immune responses to Leishmania hsp83 and hsp70 may be of particular significance in the induction of protective immune responses as well as in the development of tissue damage in cases with particularly strong hypersensitive reactions.

Lymphadenopathy as the first sign of human cutaneous infection by Leishmania braziliensis

This paper describes the presence of transitory lymphadenopathy as an initial sign of cutaneous leishmaniasis, and sometimes the only manifestation of Leishmania braziliensis infection. Ten patients with lymphadenopathy living in an area of L. braziliensis transmission had Leishmania cultivated from their lymph nodes previous to any other manifestation of cutaneous leishmaniasis. Seven of the 10 developed leishmanial ulcers later in the course of infection, whereas lymphadenopathy regressed in three cases and no other sign of infection developed. Results of tests for anti-Leishmania antibodies and an intradermal skin test were positive in four and five patients, respectively, at the time of the diagnosis. The documentation of Leishmania amastigotes in the lymph nodes before any clinical evidence of cutaneous disease indicates that early spread of L. braziliensis from the skin to lymph nodes occurs before a local lesion develops. All medical doctors examining patients coming from endemic areas of leishmaniasis should be aware that lymph node enlargement, even in the absence of a typical ulceration, may be indicative of leishmanial infection and warrants further investigation.

Characterization of the immune response in subjects with self-healing cutaneous leishmaniasis

In patients with cutaneous leishmaniasis in areas of Leishmania braziliensis transmission, ulcers may heal without therapy. In the present study, we evaluated the T cell responses of 10 subjects who two years earlier had a rapidly (less than three months) self-healing cutaneous disease. The immunologic responses of these cases were determined by intradermal skin test, measurements of antibodies, lymphocyte proliferative responses, and interferon-gamma (IFN-gamma) production in cultures stimulated with Leishmania antigens. These data were compared with those observed in 10 other patients with active cutaneous and mucosal leishmaniasis. Evidence of strong lymphocyte blastogenesis and IFN-gamma production was observed in eight of 10 patients with self-healing cutaneous leishmaniasis, with stimulation indices ranging from 32 to 506, and IFN-gamma levels ranging from 500 to 2,900 pg/ml. The mean +/- SD stimulation index of the lymphocyte proliferative responses (288 +/- 247) and the mean +/- SD of IFN-gamma production after stimulation with Leishmania antigen (970 +/- 960 pg/ml) in subjects with self-healing cutaneous leishmaniasis were similar (P > 0.05) to those observed in patients with mucosal disease (stimulation index = 308 +/- 282 and IFN-gamma level = 838 +/- 819 pg/ml). These responses were higher (P < 0.01) than those observed in patients with active cutaneous leishmaniasis (stimulation index = 50 +/- 82 and IFN-gamma level = 264 +/- 336 pg/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Polar and subpolar diffuse cutaneous leishmaniasis in Brazil: clinical and immunopathologic aspects

BACKGROUND

Diffuse cutaneous leishmaniasis (DCL) is a rare manifestation of human leishmaniasis, characterized by multiple, slowly progressive nodules or plaques without ulceration, involving almost the entire body. It has been suggested, that DCL results from a lack of cell-mediated immunity to leishmanial antigen, leading to uncontrolled parasite growth.

METHODS

We have performed detailed clinical, histopathologic, and immunologic investigations in six patients with DCL. Biopsies were taken from the nodules, processed, and examined for determination of the macrophagic pattern present, based on the intensity of vacuolation and the frequency of vacuolated cells, the parasite index, and the presence of eosinophils. Immunologically, patients were evaluated by their response to intradermal skin test to PPD or leishmania antigen, determination of antileishmania antibodies by immunofluorescent assay, and lymphocyte proliferation assay.

RESULTS

There seemed to be a negative relation between nodules and skin ulcerations, whereas the highest number of parasites were observed in patients with the greatest number of vacuolated macrophages. The delayed hypersensitivity skin test to leishmanial antigen was negative, and antileishmania IgG antibodies were positive in all patients.

CONCLUSIONS

Although all cases fulfill the criteria for being classified as DCL, they present a wide spectrum. Three cases were clearly at the unresponsive pole, and three other cases belonged to the subpolar form of DCL, exhibiting varying weak signs of antiparasite responsiveness.

A recombinant Leishmania antigen that stimulates human peripheral blood mononuclear cells to express a Th1-type cytokine profile and to produce interleukin 12

Leishmania braziliensis causes cutaneous and mucosal leishmaniasis in humans. Most patients with cutaneous leishmaniasis heal spontaneously and may therefore have developed protective immunity. There appears to be a mixed cytokine profile associated with active cutaneous or mucosal disease, and a dominant T helper (Th)1-type response associated with healing. Leishmanial antigens that elicit these potent proliferative and cytokine responses from peripheral blood mononuclear cells (PBMC) are now being identified. Herein, we report on the cloning and expression of a L. braziliensis gene homologous to the eukaryotic ribosomal protein eIF4A (LeIF) and patient PBMC responses to rLeIF. Patients with mucosal and self-healing cutaneous disease had significantly higher proliferative responses than those with cutaneous lesions. Whereas the parasite lysate stimulated patient PBMC to produce a mixed Th1/Th2-type cytokine profile, LeIF stimulated the production of interferon gamma (IFN-gamma), interleukin 2 (IL-2), and tumor necrosis factor alpha but not IL-4 or IL-10. Recombinant LeIF (rLeIF) downregulated both IL-10 mRNA in the "resting" PBMC of leishmaniasis patients and LPS-induced IL-10 production by patient PBMC. rLeIF also stimulated the production of IL-12 in cultured PBMC from both patients and uninfected individuals. The production of IFN-gamma by patient PBMC stimulated with either rLeIF or parasite lysate was IL-12 dependent, whereas anti-IFN-gamma monoclonal antibody only partially blocked the LeIF-induced production of IL-12. In vitro production of both IFN-gamma and IL-12 was abrogated by exogenous human recombinant IL-10. Therefore, we have identified a recombinant leishmanial antigen that elicits IL-12 production and Th1-type responses in patients as well as IL-12 production in normal human PBMC.

Spontaneous regional healing of extensive skin lesions in diffuse cutaneous Leishmaniasis (DCL)

The authors report a case of diffuse cutaneous leishmaniasis, with longstanding evolution and presenting with diffuse infiltrated lesions rich in amastigotes in the absence of mucosal involvement. In situ characterization with monoclonal antibodies revealed Leishmania amazonensis. Large regional lesions have presented spontaneous healing without specific therapy. Considering that DCL presents with a defect in the cellular immune response, this fact demonstrate that this patient may develop a regional cellular immune response enough to destroy the parasites and to produce clearing of some lesions.

Cytotoxicity in human mucosal and cutaneous leishmaniasis

CD8+ T cells and lysis of parasitized macrophages seem to be important in the resistance to murine leishmaniasis. In the present study, we evaluated peripheral blood mononuclear cell (PBMC) from patients with either cutaneous (CL) or mucosal (ML) leishmaniasis in cell lysis assays using 51-Cr-labeled Daudi or K562 cells, or autologous antigen-pulsed macrophages as targets. Results are reported as lytic units (number of cells required for 30% lysis) per million PBMC. Exposure of patient PBMC (n = 12) to lysate from Leishmania amazonensis promastigotes led to an increase in cytotoxic activity compared to unstimulated patient cells against Daudi (81.8 +/- 14.9 vs 13.6 +/- 5 lytic units (LU) per million PBMC; mean +/- SEM) and K562 (65.7 +/- 8.4 vs 13.1 +/- 5 LU/10(6) PBMC). ML had higher responses than CL in both targets (80.4 +/- 11.0 vs 46.4 +/- 11.6 LU/10(6) PBMC for K562, and 104.3 +/- 23.8 vs 59.3 +/- 14.3 LU/10(6) PBMC for Daudi). Normal control PBMC, stimulated with L. amazonensis antigen had 6.32 +/- 3.72 LU/10(6) PBMC against Daudi cells and 9.06 +/- 2.78 LU/10(6) PBMC against K562. The cell responsible for lysis of the K562 cells was characterized as NK, by means of cell separation employing magnetic beads coupled to antibodies. Addition of recombinant TGF-beta or recombinant human IL-10 reduced L. amazonensis-induced cytotoxicity by 90% and 70%, respectively. Cytotoxicity of antigen-stimulated PBMC was also demonstrated against autologous L. amazonensis antigen-pulsed macrophages in the range of 6.7 to 41.7 LU/10(6) PBMC.(ABSTRACT TRUNCATED AT 250 WORDS)

The absence of gamma-interferon production of S. mansoni antigens in patients with schistosomiasis

No gamma-interferon production was observed in peripheral blood mononuclear cells (PBMC) cultures from 45 patients living in an endemic area of schistosomiasis in Brazil following in vitro stimulation with schistosomula or adult worm antigens from Schistosoma mansoni (4.9 +/- 24 and 1.0 +/- 3.4 pg/ml, respectively). This immunological abnormality was observed in patients both with a high degree of infection (> or = 400 eggs/g feces) and with a low degree of infection (< 400 eggs/g feces), and was independent of the degree of natural exposure to infection. This absence of gamma-interferon production was antigen specific since high levels of this cytokine were detected in the same patients when their cells were stimulated with PPD (247 +/- 179 pg/ml) or PHA (408 +/- 328 pg/ml). In two of four subjects cured of a previous S. mansoni infection and currently living outside the endemic area, gamma-IFN was produced when their PBMC were stimulated with adult worm antigen (75 +/- 2.5 pg/ml).

Restoration of IFN-gamma production and lymphocyte proliferation in visceral leishmaniasis

Visceral leishmaniasis is associated with a marked depression of T cell responses, which has been characterized by the absence of IL-2 and IFN-gamma production by lymphocytes on in vitro stimulation with Leishmania Ag. The aim of this study was to evaluate both the mechanism of these immunologic abnormalities and the restoration of in vitro T cell responses to Leishmania Ags. A total of 15 untreated visceral leishmaniasis patients were evaluated. Although IFN-gamma and IL-4 levels in the supernatants of lymphocyte cultures were very low or absent, mRNA for these cytokines and for IL-10 were observed in PBMCs. Addition of IFN-gamma plus IL-2 enhanced lymphocyte proliferation by 158%. Restoration of T cell proliferative responses and IFN-gamma production was also observed by the addition of a neutralizing mAb alpha-IL-10. Neutralizing mAb alpha-IL-4 did not restore T cell responses but alpha-IL-10 and alpha-IL-4 mAbs had a synergistic effect on lymphocyte proliferation. The IFN-gamma levels in supernatants of lymphocyte cultures stimulated with Leishmania chagasi Ag or L. chagasi Ag plus alpha-IL-4, alpha-IL-10, or alpha-IL-4 plus alpha-IL-10 mAbs were 26 +/- 30 pg/ml, 41 +/- 18 pg/ml, 146 +/- 73 pg/ml, and 174 +/- 106 pg/ml, respectively. These data indicate that Th2 cell activation occurs in visceral leishmaniasis and that in vitro production of IFN-gamma and lymphocyte proliferation can be restored by blocking the inhibitory effect of the Th2 cytokines on mononuclear cells.

Restoration of IFN-gamma production and lymphocyte proliferation in visceral leishmaniasis

Visceral leishmaniasis is associated with a marked depression of T cell responses, which has been characterized by the absence of IL-2 and IFN-gamma production by lymphocytes on in vitro stimulation with Leishmania Ag. The aim of this study was to evaluate both the mechanism of these immunologic abnormalities and the restoration of in vitro T cell responses to Leishmania Ags. A total of 15 untreated visceral leishmaniasis patients were evaluated. Although IFN-gamma and IL-4 levels in the supernatants of lymphocyte cultures were very low or absent, mRNA for these cytokines and for IL-10 were observed in PBMCs. Addition of IFN-gamma plus IL-2 enhanced lymphocyte proliferation by 158%. Restoration of T cell proliferative responses and IFN-gamma production was also observed by the addition of a neutralizing mAb alpha-IL-10. Neutralizing mAb alpha-IL-4 did not restore T cell responses but alpha-IL-10 and alpha-IL-4 mAbs had a synergistic effect on lymphocyte proliferation. The IFN-gamma levels in supernatants of lymphocyte cultures stimulated with Leishmania chagasi Ag or L. chagasi Ag plus alpha-IL-4, alpha-IL-10, or alpha-IL-4 plus alpha-IL-10 mAbs were 26 +/- 30 pg/ml, 41 +/- 18 pg/ml, 146 +/- 73 pg/ml, and 174 +/- 106 pg/ml, respectively. These data indicate that Th2 cell activation occurs in visceral leishmaniasis and that in vitro production of IFN-gamma and lymphocyte proliferation can be restored by blocking the inhibitory effect of the Th2 cytokines on mononuclear cells.

Trypanosoma cruzi infection in rats induced early lesion of the heart noradrenergic nerve terminals by a complement-independent mechanism

The acute phase of the experimental Chagas' disease in rats induces extensive lesion of the heart sympathetic nerve terminals. Because of evidence indicating the involvement of immune reactions in neuron destruction provoked by Chagas' disease, we tested the effects of depleting the complement system by cobra venom factor upon the sympathetic denervation. The serum hemolytic activity against sensitized sheep erythrocytes ensured the efficacy of the anticomplementary treatment. Glyoxylic acid-induced histofluorescence and electron-microscopic methods allowed the study of the heart noradrenergic nerves. T. cruzi infection caused marked rarefaction of fluorescent nerve terminals at day 10 of infection and the ultrastructural study guaranteed that this rarefaction involved lesion of noradrenergic terminals. The complement depletion failed to prevent this early heart noradrenergic denervation, excluding the participation of complement-mediated lysis as a main mechanism.

Characterization of T cell responses to purified leishmania antigens in subjects infected with Leishmania chagasi

T cell responses to lipophosphoglycan-associated protein (LPG-AP) and the rgp63 antigens were studied in subjects with either asymptomatic L. chagasi infection or cured visceral leishmaniasis. The [3H]-thymidine uptake of lymphocytes stimulated with LPG-AP and rgp63 (mean +/- SD) was 14275 +/- 5048 and 3523 +/- 1678 cpm, respectively, for subjects with asymptomatic L. chagasi infection and 20046 +/- 5102 and 5086 +/- 3500 cpm, respectively, for subjects cured of visceral leishmaniasis. The responses to LPG-AP in both asymptomatic and cured visceral leishmaniasis were higher (P < 0.01) than those observed with rpg63. LPG-AP induced IFN-gamma production in all subjects studied, while rgp63 did not induce lymphocyte proliferation or IFN-gamma production in the majority of the subjects tested. IFN-gamma levels in cultures stimulated with LPG-AP were 103 +/- 81 pg/ml in individuals with asymptomatic L. chagasi infection and 127 +/- 123 pg/ml in subjects cured of visceral leishmaniasis. IFN-gamma levels in cultures stimulated with LPG-AP from subjects with asymptomatic L. chagasi infection were comparable to those observed in subjects cured of visceral leishmaniasis (P > 0.05). These data indicate that LPG-AP is recognized and induces T cell proliferation and IFN-gamma production in subjects with protective immune response against Leishmania chagasi.

Clinical and immunopathological aspects of disseminated cutaneous leishmaniasis

The clinico-pathological and immunological findings in eight patients from Bahia, Brazil with disseminated cutaneous leishmaniasis are described. This condition differs from anergic diffuse cutaneous leishmaniasis (DCL) and from classical American cutaneous leishmaniasis (ACL). The number of lesions in these patients ranged from 75 to 800 and were characterized by papules and an acneiform type of lesion with a few ulcers rather than nodules that are the main characteristic of DCL. On the other hand the high incidence of mucosal disease (38%) in patients with disseminated cutaneous leishmaniasis make the prevalence of mucosal involvement in this condition higher than that observed in ACL. L. amazonensis (five cases) and L. braziliensis (two cases) were the causal agents in the patients where the infecting agent was characterized. Antibody titers in disseminated cutaneous leishmaniasis were higher than those observed in ACL and patients with the highest antibody titers had mucosal involvement. Abnormalities in cellular immunity that are not observed in ACL such as decrease in CD4+ cells and absence of T cell response to leishmania antigen were observed in several patients with disseminated cutaneous leishmaniasis but restoration of these abnormalities occurred after treatment. In spite of the great number of lesions, the therapeutic response was good in six patients with disappearance of the lesions in a period shorter than that observed in ACL. In the two patients that presented therapeutic failure the causal agent was L. amazonensis. In such patients there was a predominance of ulcerated lesions, and a high titer of antibody was detected.

Binding of GPI-PLD-treated DAF to the surface of Schistosoma mansoni schistosomula

Decay accelerating factor (DAF,CD55) is a 70-kDa glycosylphosphatidylinositol (GPI)-anchored protein that protects human erythrocytes (HuE) from complement-mediated damage by regulation of the C3-convertase. Purified human DAF can be incorporated into sheep red blood cell (SRBC) membrane and confer complement resistance on these DAF-deficient cells. Here, we demonstrate that normal HuE or their stroma (HuES) incubated at 37 degrees C for 24 h release soluble DAF in a biologically active form into the culture medium. This soluble DAF neither inserts into SRBC plasma membranes nor presents the cross-reacting determinant (CRD) characteristic of the hydrolysis by phosphatidylinositol-specific phospholipases C (PI-PLC) but binds to schistosomula of S. mansoni protecting them from antibody-mediated complement-dependent damage. To study the binding of DAF to schistosomula in vitro, we have used purified human DAF labeled with 125I(125I-DAF), intact or treated with either PI-PLC or GPI-PLD (glycosylphosphatidylinositol-specific phospholipase D). We have found that GPI-PLD-treated DAF binds to the surface of parasites more readily than intact or PI-PLC-treated DAF. Immunoprecipitation of the samples with a monoclonal anti-human DAF antibody (IA10) revealed that schistosomula incubated with GPI-PLD-treated 125I-DAF emit a stronger signal than their counterparts. This result indicates that the surface of schistosomula is capable of acquiring GPI-PLD-treated DAF more effectively than intact or PI-PLC-treated molecules.

Leishmaniasis recidiva cutis in American cutaneous leishmaniasis

BACKGROUND

Leishmaniasis recidiva cutis (LRC) consists of active lesions around or inside the scar of classical cutaneous leishmaniasis (CL). In the literature it is considered as an hyperergic form of CL because the patients show a strong response to intradermal testing with leishmania antigen and, histologically, the parasites are scarce or absent; a well-organized granuloma is always observed.

METHODS

Three patients from Bahia (Brazil) with LRC were evaluated by clinical examination, biopsies, skin tests with leishmania antigen, serology, and culture. In addition, a specific lymphocyte blastogenesis test was done and the species of leishmania characterized.

RESULTS

The disease was caused by both L. amazonensis and L. braziliensis and serological titers varied from 1/16 to 1/64. The patients presented histologic and immunologic aspects different from those referred to in the literature. From four biopsies obtained only two presented a granulomatous reaction and parasites varied from absent to a parasite index 3. In one patient an absence of T cell response to leishmania antigen was observed in the first evaluation with restoration of the response after cure. In the other two, the degree of the specific proliferative response was lower than that usually observed in patients with classical CL.

CONCLUSIONS

These findings indicate that New World LRC can not be considered a hyperergic form of CL. With respect to its clinical aspects and response to treatment, LRC must be considered as an entity different from the classical CL.

Characteristics of the acquired immunodeficiency syndrome in Brazil

The clinical and epidemiologic characteristics of the acquired immunodeficiency syndrome (AIDS) were studied in a tropical area of Brazil. During an 18-month period (July 1989-January 1991), 111 consecutive AIDS patients (102 men and nine women) were evaluated. Patients reported homosexual/bisexual activities (60%), intravenous drug use (19%), or both (6%), heterosexual activities (11%), blood transfusions (2%), and 2% belonged to an undetermined category. Weight loss, fever, oral thrush, and diarrhea were present in > or = 70% of the patients at presentation. An unexpected high frequency of hepatomegaly (49%) was detected, and found to be significantly associated with tuberculosis (P < 0.0001). Although the epidemiologic features of human immunodeficiency virus transmission were comparable to the United States/European pattern, the clinical spectrum of opportunistic infections more closely resembled that reported in Africa and Haiti, with a greater frequency of fungal and mycobacterial infections than Pneumocystis carinii pneumonia and viral infections.

Mapping human T cell epitopes in leishmania gp63. Identification of cross-reactive and species-specific epitopes

Both a conserved surface metalloprotease of leishmania, gp63 as well as certain gp63-derived peptides, have been shown to have immunoprophylactic potential in mouse models of leishmaniasis. In addition, PBMC from individuals with cutaneous, mucosal, or cured visceral leishmaniasis respond in vitro to both native and rgp63. In this report, we mapped human T cell epitopes within gp63. T cells from leishmaniasis patients responded in vitro to certain peptides of gp63 by proliferation and IFN-gamma production. One peptide, (PT7), stimulated cells from all individuals tested (n = 7). Anti-PT7 T cell lines derived from PBMC of a mucosal leishmaniasis patient contained a heterogeneous population of cells which responded by proliferation and IFN-gamma production to in vitro stimulation with Leishmania promastigote lysate. Another peptide (PT1) derived from Leishmania chagasi gp63 stimulated PBMC from an L. chagasi patient although the corresponding Leishmania major-derived peptide did not. Both L. major PT7 and L. chagasi PT1 were able to induce anti-Leishmania-specific T cell lines from normal human PBMC. These T cell lines responded to in vitro stimulation with promastigote lysate indicating that both peptides were immunogenic for naive T cells in vitro. In conclusion, both antigenic and immunogenic gp63 peptide sequences have been defined, some appearing to be conserved among Leishmania species and at least one that appears to be species specific.

Mapping human T cell epitopes in leishmania gp63. Identification of cross-reactive and species-specific epitopes

Both a conserved surface metalloprotease of leishmania, gp63 as well as certain gp63-derived peptides, have been shown to have immunoprophylactic potential in mouse models of leishmaniasis. In addition, PBMC from individuals with cutaneous, mucosal, or cured visceral leishmaniasis respond in vitro to both native and rgp63. In this report, we mapped human T cell epitopes within gp63. T cells from leishmaniasis patients responded in vitro to certain peptides of gp63 by proliferation and IFN-gamma production. One peptide, (PT7), stimulated cells from all individuals tested (n = 7). Anti-PT7 T cell lines derived from PBMC of a mucosal leishmaniasis patient contained a heterogeneous population of cells which responded by proliferation and IFN-gamma production to in vitro stimulation with Leishmania promastigote lysate. Another peptide (PT1) derived from Leishmania chagasi gp63 stimulated PBMC from an L. chagasi patient although the corresponding Leishmania major-derived peptide did not. Both L. major PT7 and L. chagasi PT1 were able to induce anti-Leishmania-specific T cell lines from normal human PBMC. These T cell lines responded to in vitro stimulation with promastigote lysate indicating that both peptides were immunogenic for naive T cells in vitro. In conclusion, both antigenic and immunogenic gp63 peptide sequences have been defined, some appearing to be conserved among Leishmania species and at least one that appears to be species specific.

Correlation between cell-mediated immunity and degree of infection in subjects living in an endemic area of schistosomiasis

Cell-mediated immunity to Schistosoma mansoni antigens, unrelated antigens and mitogens was evaluated in 50 subjects with the same degree of exposure to infection living in an endemic area of schistosomiasis. The degree of infection, assessed by the number of eggs/g of stool, was variable in this population (0-5604), suggesting differences in susceptibility to infection. Absence of lymphoproliferative response was observed in 56% of this group, despite having a response to purified protein derivative of tuberculin (PPD) and tetanus toxoid (TT) antigens and to pokeweed mitogen. The 50 subjects were divided into two groups, according to their degree of infection. The lymphoproliferative responses to schistosomula and adult worm antigens in the group with a low degree of infection (< 400 eggs/g of stool) were higher than the ones documented in patients with a high degree of infection (> 400 eggs/g of stool), and these differences were statistically significant (p < 0.001). An inverse correlation between the lymphocyte proliferation in response to S. mansoni antigens and the degree of infection was also observed (p = 0.02), indicating that subjects with a lower degree of infection have a higher lymphoproliferative response to schistosomula and adult worm antigens. No differences in the lymphocyte reactivity to other antigens (PPD and TT) were detected in these groups. An impairment of interferon-gamma in vitro production was observed when the lymphocytes from these subjects were stimulated with S. mansoni adult worm antigen, although they produced gamma interferon in response to phytohemagglutinin.

Lymphadenopathy associated with Leishmania braziliensis cutaneous infection

Lymph node involvement by Leishmania during human cutaneous leishmaniasis was reported more than 90 years ago, but the importance of certain Leishmania strains in such dissemination remains largely speculative. We have examined 36 consecutively untreated cutaneous leishmaniasis patients early in their disease; 66.7% had enlarged lymph nodes. Patients with enlarged lymph nodes had higher anti-Leishmania immune responses than patients without such involvement, both at the IgG antibody level (mean +/- SD optical density at 492 nm = 0.163 +/- 0.089 versus 0.098 +/- 0.086; P = 0.009) and in skin test responses (12.4 +/- 10.2 mm versus 5.7 +/- 7.3; P = 0.03). Thirteen (62%) of 21 lymph node cultures and 16 (53%) of 30 cultures from cutaneous sites were positive for Leishmania. Eleven of 13 isolates from lymph nodes were characterized by a panel of monoclonal antibodies, and all were typed as L. braziliensis. Our findings stress the importance of L. braziliensis as an agent involved in the early invasion of the lymphatic system.