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Biomedical subjects

A Barral

Publications and source records attributed to A Barral.

At least 37 records · Page 2Linked to original sources
PubMed1996

In vivo protective effect of the lectin from Canavalia brasiliensis on BALB/c mice infected by Leishmania amazonensis.

In vivo administration of Canavalia brasiliensis lectin (at the time of infection, or maintained throughout the infection) reduced the lesions of highly susceptible BALB/c mice infected by Leishmania amazonensis. At the doses used C. brasiliensis lectin (ConBr) does not interfere with penetration or fate of Leishmania in the macrophages in vitro. Since Interferon-gamma (IFN-gamma) is the major macrophage activating factor, and considered a critical element in the successful immune response against leishmaniasis, we explored its participation in this phenomenon. ConBr either in vivo or in vitro induced IFN-gamma production in normal or in leishmania-infected BALB/c mice. However we were unable to change the course of disease by in vivo IFN-gamma administration (although IFN-gamma preparations were effective in inducing a leishmanicidal effect in vitro on L. amazonensis-infected peritoneal macrophages). Additionally, IFN-gamma neutralization with anti-IFN-gamma monoclonal antibody did not alter the protection conferred by ConBr administration. These data show that lectin administration in vivo is protective in the otherwise unchecked L. amazonensis infection of BALB/c mice, and suggest that such effect is not mediated by IFN-gamma.

Animals↗
PubMed1996

Cytotoxicity in patients with different clinical forms of Chagas' disease.

There are few studies on cell-mediated cytotoxicity in human Chagas' disease. In the present study, we evaluated peripheral blood mononuclear cell (PBMC) cytotoxicity activity from chagasic patients with different clinical forms of disease. To verify the cytotoxic response, we performed cell lysis assays using 51Cr-labelled K562 cells as targets. Results are reported as lytic units (LU = number of cells required for 30% lysis) per million PBMC. Exposure of patients' PBMC to Trypanosoma cruzi antigen led to an increase in cytotoxic activity compared with unstimulated patient cells against K562. Asymptomatic cardiomyopathy patients had higher responses (37.8 +/- 5.0 LU/10(6) PBMC; mean +/- s.d.) than indeterminate (11.5 +/- 3.6 LU/10(6) and symptomatic cardiomyopathy (7.8 +/- 2.5 LU/10(6)). Normal control PBMC stimulated with T. cruzi antigen had 4.36 +/- 1.31 LU/10(6)) PBMC against K562. Addition of recombinant interferon-gamma (IFN-gamma) did not lead to significant increase in cytotoxicity in any group of patients. On the other hand, recombinant human IL-12 significantly increased cytotoxic responses from symptomatic cardiomyopathy patients and normal controls who presented low levels of cytotoxicity induced by T. cruzi antigen. The combined use of IL-12 and a neutralizing anti-IFN-gamma antibody did not change IL-12-induced cytotoxic responses, showing the direct role of this cytokine on natural killer (NK) cells. NK cells were the main cells responsible for the lysis of K562 target cells as evidenced by testing cell subsets following magnetic cell sorting. These data demonstrate that chagasic patients with different clinical forms of disease have PBMC which respond to T. cruzi antigen with a cytotoxic response, and this response is up-regulated by IL-12.

Adult↗
PubMed1996

Biological behavior of Leishmania amazonensis isolated from humans with cutaneous, mucosal, or visceral leishmaniasis in BALB/C mice.

Leishmania amazonensis causes a wide spectrum of disease in humans. In this study, we evaluated BALB/c mice infected with five strains of L. amazonensis isolated from patients with either cutaneous, mucosal, or visceral leishmaniasis. Mice infected with cutaneous and mucosal isolates developed ulcerating footpad lesions with parasite-loaded macrophages and extensive tissue destruction. Skin metastases, early dissemination of parasites to the spleen, and high anti-Leishmania antibody levels were also noted. Mice infected with L. amazonensis strains isolated from patients with visceral disease had a controlled infection, with small footpad lesions with mononuclear cell infiltration, few infected macrophages, and granuloma formation. They had no skin metastases, delayed dissemination of the parasite to the spleen, lower levels of IgG and higher levels of IgG2a against L. amazonensis. These findings demonstrate an unexpected resistance of BALB/c mice to the infection with L. amazonensis isolated from patients with visceral leishmaniasis. This resistance seems to be due to differences in these parasites that may be related to the altered course of the disease in humans and in isogenic BALB/c mice.

Animals↗
PubMed1995

Antigenicity of cystatin-binding proteins from parasitic protozoan. Detection by a proteinase inhibitor based capture immunoassay (PINC-ELISA).

A novel immunoassay (PINC-ELISA) was designed using proteinase inhibitors of the cystatin superfamily (PINC) in the solid phase, to promote the selective capture of cysteine proteinases. The method was applied in the identification of papain-like antigens from parasitic protozoa. PINC of human origin, namely recombinant cystatin C (r-cystatin C) or low molecular weight kininogen were used in the assays to adsorb proteases contained in cell lysates from various trypanosomatids. The PINC-ELISA was at first optimized with the major cysteine proteinase from Trypanosoma cruzi (known as GP57/51 or cruzipain), an antigen whose serodiagnostic properties were previously established. Cruzipain is selectively adsorbed from crude extracts of T. cruzi onto PINC-coated wells; the finding that antibodies bind to epitopes located away from the sites of interaction with r-cystatin or low molecular weight kininogen has allowed for the screening of antibodies in chagasic sera, the methodology being advantageous in that it dispensed prior purification of the proteinase antigen. The PINC-ELISA was then carried out with lysates originating from Leishmania m. amazonensis (amastigotes) or Leishmania donovani (promastigotes). Complexes between solid-phase r-cystatin C and antigenic ligands in the lysates were again detected. The Leishmania molecules which bound to r-cystatin C, were respectively recognized by serum antibodies from mice chronically infected with L. amazonensis or from patients with visceral leishmaniasis. Direct evidence for the presence of cysteine proteinases in lysates from L. donovani was then obtained, using synthetic fluorogenic substrates.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Serum soluble markers in the evaluation of treatment in human visceral leishmaniasis.

Visceral leishmaniasis (VL) has a fatal course if not properly treated. Recovery from VL is linked to cellular immune response. Unresponsiveness to antimonial therapy reinforces the importance of determining parameters for treatment assessment. We analysed the pre- and post-treatment serum levels of soluble CD4 (sCD4), sCD8, sIL-2R, soluble intercellular adhesion molecule-1 (sICAM-1) and neopterin in groups of VL patients either responsive or not to standard antimonial therapy. Pretreatment serum levels of all markers except for sICAM-1 were significantly higher in VL patients than in healthy subjects from the same area (P < 0.05). sICAM-1 levels were similar in healthy controls and in VL patients refractory to antimonial therapy (P = 0.25), but significantly higher in patients responsive to treatment (P = 0.02). The comparison of pre- and post-treatment concentrations showed that all markers, except sCD4 and sICAM-1, presented a significant fall (P < 0.05) in patients responsive to antimonial therapy. However, only neopterin presented with levels compatible with those of healthy subjects at the end of treatment (P = 0.30). In refractory patients sICAM-1 presented with post-treatment levels significantly higher than the pretreatment determinations (P = 0.03), while sCD4 experienced a significant drop (P = 0.01). All markers displayed clearly distinct behaviour according to the patient's response to therapy. This makes all soluble molecules studied suitable for use as indicators of antimonial therapy response. Additionally the comparison of pretreatment levels of the markers between responders and refractory patients to antimonial therapy showed that serum concentrations of sIL-2R and sICAM-1 significantly differed among these two groups (P = 0.02 in each case), suggesting that they may be used in future as predictors of antimonial therapy response.

Antimony↗
PubMed1995

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)

Animals↗
PubMed1995

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.

Adolescent↗
PubMed1995

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.

Adult↗
PubMed1995

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.

Animals↗
PubMed1995

Up-regulation of T helper 2 and down-regulation of T helper 1 cytokines during murine retrovirus-induced immunodeficiency syndrome enhances susceptibility of a resistant mouse strain to Leishmania amazonensis.

Resistance to and recovery from leishmania infection is dependent on cell-mediated immunity. C57BL/6 mice are resistant to Leishmania amazonensis (La) infection but susceptible to LP-BM5 murine leukemia virus (MuLV) infection. MuLV infection leads to a state of immunodeficiency characterized by severe compromise of cell-mediated immunity. When infected with La alone, C57BL/6 mice developed a small transient lesion that evolved to spontaneous healing or a lesion with extremely slow growth. Lesions were predominantly comprised of a lympho-macrophagic infiltrate with few parasitized macrophages. When infected with La and, 4 weeks later, with MuLV (La-MuLV), the mice developed a large uncontrolled nonhealing lesion containing vacuolated and heavily parasitized macrophages. In contrast, mice infected with MuLV first and La 4 weeks later (MuLV-La) developed a small but persistent lesion, characterized histologically by a small number of heavily parasitized macrophages and few lymphocytes. Eight weeks after MuLV infection, both had similar immunological profiles with decreased lymphocyte proliferation, diminished production of interferon-gamma, and high production of interleukins 4 and 10. At the time of L. amazonensis infection, La-MuLV animals have a normal T cell function whereas in MuLV-La mice this function is already impaired; this may influence the recruitment of macrophages to the site of leishmania injection.

Animals↗
PubMed1994

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.

Adult↗
PubMed1994

Transforming growth factor-beta in tegumentary leishmaniasis.

1. The course of infection with the protozoan parasite Leishmania is determined in part by its early replication in macrophages, the exclusive host cells for these organisms. Resistance to and recovery from leishmanial infection is related to cell-mediated immune responses in all forms of human and murine leishmaniasis. 2. Factors contributing to the early inhibition or proliferation of Leishmania are poorly understood, but cytokines such as IFN gamma, IL-10 or transforming growth factor beta (TGF-beta) are known to influence the replication of Leishmania in macrophages. 3. TGF-beta is a multipotential cytokine with diverse effects on cells of the immune system, including down-regulation of certain macrophage functions. Infection of murine or human macrophages by Leishmania induces the production of active TGF-beta. Recombinant TGF-beta added to murine or human macrophage cultures leads to increased intracellular replication of Leishmania. Exogenous TGF-beta administered in vivo promotes enhancement of infection, whereas its neutralization by monoclonal antibodies decreases the level of in vitro infection, and protects susceptible mice. 4. Susceptible animals treated with anti-TGF-beta monoclonal antibodies change their immune response, not increasing the expression of IL-4 while increasing the expression of IFN gamma mRNA in their draining lymph nodes. Resistant animals treated with TGF-beta also change their pattern of immune response as indicated by an increase of the important Th2 cytokine IL-10 mRNA in the draining lymph node. 5. TGF-beta has profound effects on the host response to Leishmania in both mouse and man, and probably is an important parasite escape mechanism.

Animals↗
PubMed1993

Antigen-reactive gamma delta T cells in human leishmaniasis.

The importance of Ag-specific gamma delta T lymphocytes in human immune responses to pathogenic organisms is unknown. In the present study the expression of gamma delta TCR on T lymphocytes from patients with cutaneous, mucosal, or visceral leishmaniasis was examined. All of these patient groups had elevated levels of gamma delta T cells in peripheral blood. Patients' gamma delta T cells included CD8+ as well as null cells. The percentage of T cells expressing gamma delta TCR was increased significantly by stimulation in vitro with certain parasite Ag. T-cell lines generated by stimulation with promastigote lysates of Leishmania amazonensis or L. braziliensis typically contained 25 to 60% gamma delta T cells. In contrast, two immunodominant surface Ag of L. amazonensis, gp63 and gp42, did not expand gamma delta T cells from infected patients, although both Ag elicited strong alpha beta T-cell responses. gamma delta T cells isolated from a Leishmania-specific T-cell line responded to stimulation with promastigote lysate. Of particular interest, gamma delta T cells from PBMC of a patient with mucosal leishmaniasis responded to stimulation with a recombinant 70 kDa heat shock protein of L. chagasi. This study demonstrated that several clinical forms of leishmaniasis induced elevated numbers of gamma delta T cells that responded specifically to Leishmania Ag in vitro. Therefore, this component of the T-cell response to Leishmania may impact the outcome of clinical disease.

Animals↗
PubMed1993

Transforming growth factor beta as a virulence mechanism for Leishmania braziliensis.

Transforming growth factor beta (TGF-beta) has potent down-regulating effects on macrophages and is thus capable of influencing the fate of intramacrophage parasites, including leishmanias. We report the development of a mouse model for the study of the human pathogen Leishmania braziliensis and demonstrate, both in vitro and in vivo, a key regulatory role for TGF-beta in the pathogenesis of infection with this parasite. Recombinant TGF-beta added to cultures of murine peritoneal macrophages led to increased intracellular L. braziliensis replication, whereas addition of neutralizing anti-TGF-beta monoclonal antibody decreased levels of infection. Macrophages infected with L. braziliensis produced biologically active TGF-beta, with a direct correlation between amounts of TGF-beta induced by two parasite isolates and their relative virulence. In vivo, treatment with recombinant TGF-beta rendered avirulent parasites virulent and activated latent L. braziliensis infection. Activation of parasite replication was observed in mice which had been infected with L. braziliensis 15 weeks previously but had not developed lesions or had healed lesions, depending on the parasite isolate used to infect the mice. The exacerbation of L. braziliensis infection in vivo was associated with an increase of interleukin 10 mRNA in the draining lymph node. These results demonstrate that TGF-beta is able to alter the course of in vitro and in vivo infections with L. braziliensis, the latter being characterized by an increase in interleukin 10, an important Th2 helper-T-cell cytokine.

Actins↗
PubMed1993

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.

Adult↗
PubMed1992

Transforming growth factor-beta in leishmanial infection: a parasite escape mechanism.

The course of infection with the protozoan parasite Leishmania is determined in part by their early replication in macrophages, the exclusive host cells for these organisms. Although factors contributing to the survival of Leishmania are not well understood, cytokines influence the course of infection. Transforming growth factor-beta (TGF-beta) is a multipotential cytokine with diverse effects on cells of the immune system, including down-regulation of certain macrophage functions. Leishmanial infection induced the production of active TGF-beta, both in vitro and in vivo. TGF-beta was important for determining in vivo susceptibility to experimental leishmanial infection.

Actins↗
PubMed1992

Leishmania amazonensis infection: a comparison of in vivo leishmanicidal mechanisms between immunized and naive infected BALB/c mice.

In vitro studies have shown that both macrophage activation and destruction of parasitized macrophages lead to leishmania destruction. The relative role played by such mechanisms in vivo have not been properly evaluated. We took advantage of the model of intravenous immunization with solubilized leishmanial antigen which renders partially resistant the otherwise highly susceptible BALB/c mice to address this issue avoiding the interference of different genetic backgrounds. Leishmania destruction occurred in three situations: destruction of the parasitized macrophage, which were in close contact with lymphocytes or eosinophils; extracellular damage, always surrounded by small foci of granulocytes; and parasite damage inside activated macrophages. Destruction of the parasitized macrophages was frequently seen in immunized and protected animals. Our observations suggest that destruction of parasite-loaded macrophages is an important mechanism of host protection in experimental cutaneous leishmaniasis.

Animals↗