Total Leishmania antigens with Poly(I:C) induce Th1 protective response

Our proposal was to develop a vaccine based on total Leishmania antigens (TLA) adjuvanted with polyinosinic-polycytidylic acid [Poly(I:C)] able to induce a Th1 response which can provide protection against Leishmania infection. Mice were vaccinated with two doses of TLA-Poly(I:C) administered by subcutaneous route at 3-week interval. Humoral and cellular immune responses induced by the immunization were measured. The protective efficacy of the vaccine was evaluated by challenging mice with infective promastigotes of Leishmania (Leishmania) amazonensis into the footpad. Mice vaccinated with TLA-Poly(I:C) showed a high anti-Leishmania IgG titre, as well as increased IgG1 and IgG2a subclass titres compared with mice vaccinated with the TLA alone. The high IgG2a indicated a Th1 bias response induced by the TLA-Poly(I:C) immunization. Accordingly, the cellular immune response elicited by the formulation was characterized by an increased production of IFN-γ and no significant production of IL-4. The TLA-Poly(I:C) immunization elicited good protection, which was associated with decreased footpad swelling, a lower parasite load and a reduced histopathological alteration in the footpad. Our findings demonstrate a promising vaccine against cutaneous leishmaniasis that is relatively economic and easy to develop and which should be taken into account for preventing leishmaniasis in developing countries.

Biocomposites Based on Bacterial Cellulose and Apple and Radish Pulp

Bacterial cellulose (BC) pellicles obtained from an Acetobacter xylinum culture were disintegrated using mechanical methods to be used as reinforcement to produce biocomposite sheets with Apple and Radish Pulp. The nanosize disintegrated BC pellicles were blended with microsize apple and radish pulp in the wet state and then hot pressed to produce paper-like sheets.

Thermal analysis was carried out by Thermogravimetry Analysis (TGA). Mechanical properties were assessed by Quasistatic Tensile Tests and Dynamic Mechanical Analysis (DMA). High tensile moduli were obtained (up to 8 GPa) and a nearly linear dependence of Young's modulus on the BC volume fraction was observed. Morphological characterisation of biocomposite sheets and fracture surfaces performed by Scanning Electron Microscopy (SEM) revealed the structure of the disintegrated cellulose network and the failure mechanisms of the biocomposites.

Trypanosoma cruzi: Chemotherapeutic effects of clomipramine in mice infected with an isolate obtained from an endemic area

The susceptibility of Trypanosoma cruzi strains to nifurtimox and benznidazole has been investigated and resistant strains have been described. Some tricyclic drugs are lethal for trypomastigote and epimastigote forms of T. cruzi (Tulahuen strain) and prevent the disease in mice. We investigated whether clomipramine, a tricyclic antidepressant drug with anti-trypanothione reductase and anti-calmodulin effects, could be effective in treating Albino Swiss mice infected with trypomastigotes of a new T. cruzi isolate from a chronic patient from an endemic area of Argentina in two different treatment schedules. Both treatment schedules were effective in reducing electrocardiographic changes and preventing myocardial structural damage. The cardiac beta-receptors low affinity was compensated for by an increment in their density. This probably maintained cardiac function since 70% of the mice survived for more than 2 years even though anti-cruzipain titers remained high. These results demonstrate that clomipramine, clinically used as a neuroleptic, could be a promising trypanocidal agent for the treatment of Chagas' disease.

Thioridazine treatment prevents cardiopathy in Trypanosoma cruzi infected mice

Trypanosoma cruzi trypanothione reductase is an enzyme that has been identified as a potential target for chemotherapy. Thioridazine inhibits it and prevented cardiopathy in mice infected with T. cruzi Tulahuen strain. As not all T. cruzi strains respond to treatment in the same way, an isolate from a chronic patient (SGO Z12) was used; parasitaemias were studied along with, survival, serology, electrocardiography, histology and cardiac beta receptor function. Parasitaemia in thioridazine (80 mg/(kg day) for 3 days) treated mice was less and lasted for a shorter period (P < 0.01), there were reduced electrocardiographic and histological alterations and significantly improved survival (80% of non-treated died). Treated mice had lower receptor affinity and higher density as a compensatory mechanism, modifying the course of T. cruzi infection (SGO Z12 isolate) and preventing the consequent cardiopathy.

Antibodies to an epitope from the Cha human autoantigen are markers of Chagas' disease

Chagas' disease is a prevalent disease in South America that is thought to have an autoimmune etiology. We previously identified human Cha as a new autoantigen recognized by chagasic sera. Those sera recognized an epitope spanning amino acids 120 to 129 of Cha, named R3. In the present study we have used the synthetic R3 peptide for the detection of serum immunoglobulin G antibodies from patients at different stages of Chagas' disease, including a therapeutically treated group. The immunoreactivity with R3 by enzyme-linked immunosorbent assay (ELISA) showed 92.4% sensitivity and 100% specificity for Chagas' disease sera. This sensitivity and specificity were higher than for any other autoantigen described to date. No anti-R3 antibodies were detected in sera from Leishmania-infected or idiopathic dilated cardiomyopathy patients or healthy controls from the same areas. Moreover, anti-R3 antibody reactivity detected by ELISA correlated with conventional serological tests as indirect immunofluorescence and ELISA assays with Trypanosoma cruzi extracts and other diagnostic tests as indirect hemagglutination. The levels of anti-R3 antibodies increased with progression and symptomatology of Chagas' disease. More interestingly, a statistically significant fall in anti-R3 antibody titer was observed in patients treated with antiparasitic drugs. Those results suggest that the presence of anti-R3 antibodies is a highly specific marker of Chagas' disease and that R3 ELISA could be helpful in the diagnosis and monitoring of this disease.

Effects of clomipramine on Trypanosoma cruzi infection in mice

Trypanosoma cruzi, widely distributed in Latin American countries, provokes Chagas disease, characterized by cardiomyopathy and mega-viscera. The drugs used currently for treatment of acute Chagas disease are highly toxic; the side-effects are undesirable and patients may abandon treatment. We have previously demonstrated that clomipramine (CLO) exerts trypanocidal effects upon epimastigotes and trypomastigotes in vitro with anticalmodulin activity. The present study analyses the effectiveness of CLO treatment in mice infected with a low number of T. cruzi, an animal model that reproduces acute, indeterminate and chronic phases of this trypanosomiasis. In this work, our results demonstrated that CLO 5 mg/kg daily for 30 days, or 2 doses of CLO 40 mg/kg given intraperitoneally at 1 h and 7 days after infection, was not toxic for the host, but was effective against the parasite in that parasitaemias became negative and only mild heart structural and electrocardiographic alterations were detected in the chronic phase in the group treated with CLO 5 mg/kg. In mice treated with CLO 40 mg/kg, none of these alterations was detected. Cardiac beta receptor density and affinity returned to normal in the chronic stage in both experimental groups. T. cruzi enzymes such as calmodulin and trypanothione reductase represent potential drug targets. It has been reported that both can be inhibited by CLO, a tricyclic drug used in clinical therapeutics. We have shown that CLO strongly decreased the mortality rate and electrocardiographic alterations; in addition cardiac beta receptor density and heart histology returned to, or close to, normality 135 days post infection. These results clearly demonstrated that CLO treatment modified significantly the natural evolution of T. cruzi infection.

Anti-galectin-1 autoantibodies in human Trypanosoma cruzi infection: differential expression of this beta-galactoside-binding protein in cardiac Chagas' disease

The pathogenesis of Chagas' disease has been subject of active research and still remains to be ascertained. Galectin-1 (Gal-1), a member of a conserved family of animal beta-galactoside-binding proteins, localized in human heart tissue, has been suggested to play key roles in immunological and inflammatory processes. In the present study we demonstrated the occurrence of anti-Gal-1 autoAb in sera from patients in the acute and chronic stages of Chagas' disease (ACD and CCD) by means of ELISA and Western blot analysis. We found a marked increase in the level and frequency of Ig E anti-Gal-1 antibodies in sera from patients with ACD, but a low frequency of Ig M anti-Gal-1 immunoreactivity. Moreover, Ig G immunoreactivity to this beta-galactoside-binding protein was found to be correlated with the severity of cardiac damage in CCD, but was absent in nonrelated cardiomyopathies. We could not detect immunoreactivity with Trypanosoma cruzi antigens using a polyclonal antibody raised to human Gal-1 and no hemagglutinating activity could be specifically eluted from a lactosyl-agarose matrix from parasite lysates. Moreover, despite sequence homology between Gal-1 and shed acute phase antigen (SAPA) of T. cruzi, anti-Gal-1 antibodies eluted from human sera failed to cross-react with SAPA. In an attempt to explore whether Gal-1 immunoreactivity was originated from endogenous human Gal-1, we finally investigated its expression levels in cardiac tissue (the main target of Chagas' disease). This protein was found to be markedly upregulated in cardiac tissue from patients with severe CCD, compared to cardiac tissue from normal individuals.

Induction of antibodies reactive to cardiac myosin and development of heart alterations in cruzipain-immunized mice and their offspring

Human and murine infection with Trypanosoma cruzi parasite is usually accompanied by strong humoral and cellular immune response to cruzipain, a parasite immunodominant antigen. In the present study we report that the immunization of mice with cruzipain devoid of enzymatic activity, was able to induce antibodies which bind to a 223-kDa antigen from a mouse heart extract. We identified this protein as the mouse cardiac myosin heavy chain by sequencing analysis. The study of IgG isotype profile revealed the occurrence of all IgG isotypes against cruzipain and myosin. IgG1 showed the strongest reactivity against cruzipain, whereas IgG2a was the main isotype against myosin. Anti-cruzipain antibodies purified by immunoabsorption recognized the cardiac myosin heavy chain, suggesting cross-reactive epitopes between cruzipain and myosin. Autoimmune response in mice immunized with cruzipain was associated to heart conduction disturbances. In addition, ultrastructural findings revealed severe alterations of cardiomyocytes and IgG deposit on heart tissue of immunized mice. We investigated whether antibodies induced by cruzipain transferred from immunized mothers to their offsprings could alter the heart function in the pups. All IgG isotypes against cruzipain derived from transplacental crossing were detected in pups' sera. Electrocardiographic studies performed in the offsprings born to immunized mothers revealed conduction abnormalities. These results provide strong evidence for a pathogenic role of autoimmune response induced by a purified T. cruzi antigen in the development of experimental Chagas' disease.

Cruzipain induces autoimmune response against skeletal muscle and tissue damage in mice

The goal of the current study was to investigate whether cruzipain, a major Trypanosoma cruzi antigen, is able to induce in mice an autoimmune response and skeletal muscle damage. We demonstrate that immunization with cruzipain triggers immunoglobulin G antibody binding to a 210-kDa antigen from a syngeneic skeletal muscle extract. The absorption of immune sera with purified myosin completely eliminated this reactivity, confirming that the protein identified is really myosin. We also found that spleen cells from immunized mice proliferated in response to a skeletal muscle extract rich in myosin and to purified myosin. Cells from control mice did not proliferate against any of the antigens tested. In addition, we observed an increase in plasma creatine kinase activity, a biochemical marker of muscle damage. Histological studies showed inflammatory infiltrates and myopathic changes in skeletal muscle of immunized animals. Electromyographic studies of these mice revealed changes such as are found in inflammatory or necrotic myopathy. Altogether, our results suggest that this experimental model provides strong evidence for a pathogenic role of anticruzipain immune response in the development of muscle tissue damage.

Thioridazine treatment modifies the evolution of Trypanosoma cruzi infection in mice

Thioridazine, a tricyclic drug, is known to have a direct effect on Trypanosoma cruzi, disrupting the parasites' mitochondria and kinetoplasts. In the present study, the drug was used orally, at 80 mg/kg.day for 3 days, to treat mice inoculated with low numbers of T. cruzi. The drug caused no apparent toxicity in the host. It cleared trypomastigotes from the bloodstream, prevented the histological and functional alterations of the heart normally observed in the chronic phase of the experimental disease, and greatly reduced the mortality rate compared with that in untreated, infected controls. When checked 135 days post-infection, the density of cardiac beta receptors and the cardiac histology of the treated mice were indistinguishable from those of uninfected, untreated controls. The drug is already used to treat humans, as a neuroleptic drug. It appears to be able to prevent acute infection with T. cruzi evolving into chronic disease, at least in mice, and may be a useful base from which to design new agents for the treatment of Chagas disease.

Inflammatory arthritic process, iridocyclitis and immune response to articular and ocular antigens in Wistar rats injected with T. gondii trophozoites

The present study deals with the potential role of T. gondii in inducing an arthritic inflammatory process. Wistar rats were injected subcutaneously (sc) into the right footpad with viable T. gondii trophozoites emulsified in incomplete Freund's adjuvant (IFA). The control group was injected with IFA. All parasite-injected animals developed a local inflammatory process characterized by hind limb swelling and marked restriction of ankle motility approximately 25 days after injection. Histopathogical studies of the joints, carried out 90 days after injection, revealed intense mononuclear infiltration, proliferation of granulation tissue, giant cells and necrosis in the synovia of 90% of T. gondii-injected rats. Strikingly, 40% (4/10) of the parasite-injected animals developed iridocyclitis, which was characterized by intense mononuclear infiltration around the iris-ciliary microvasculature in two animals and a slightly pronounced infiltrate of polymorphonuclear and mononuclear cells in two other animals. Antibodies to soluble T. gondii antigens (STAg) were detected in all parasite-injected rats. Antibodies against articular and ocular antigens such as proteoglycans, type II collagen, retinal S antigen and iris antigens were detected by ELISA in 40, 80, 70 and 70% of T. gondii -injected animals, respectively. Control animals injected with IFA failed to develop any articular or ocular process or humoral immune response. The present study demonstrated that footpad sc injection of Wistar rats with viable T. gondii trophozoites was able to induce a localized inflammatory arthritic process which, in some of the animals, was accompanied by iridocyclitis and immune response against articular and ocular components.

Trypanosoma cruzi: the major cysteinyl proteinase (cruzipain) is a relevant immunogen of parasite acidic antigens (FIII)

This study examined the immune responses induced by cruzipain, a well-characterized T. cruzi antigen, to determine whether it is a relevant immunogen among the parasite acidic antigens (FIII), for which some biological properties have been studied previously. Humoral and cellular immune responses were investigated in BALB/C mice after immunization with cruzipain or FIII. Skin tests revealed immediate type-hypersensitivity (ITH) and delayed-type hypersensitivity (DTH) reactions to cruzipain in both groups of immunized mice. IgG1 and IgE isotypes against cruzipain were detected by ELISA in both groups and immunoblot studies showed that these antibodies recognized a major protein band of 50 kDa, cruzipain. The antigen-specific proliferative responses of spleen lymphocytes from both groups of immunized mice were also increased. Immunization with cruzipain of FIII antigen significantly enhanced the percentage survival of mice challenged with 10(3) trypomastigotes. The results revealed high cross-reactivity between cruzipain and FIII, suggesting the cruzipain is a relevant immunogen among the parasite acidic antigens.

Chagas' disease: polyspecificity of antibodies against Trypanosoma cruzi acidic antigens

The aim of this work was to study the reactivity of chagasic patient sera against a panel of natural antigens and its relationship with the immune response against T. cruzi acidic antigens. The presence of IgG and IgM antibodies reactive with myosin, myoglobin, actin and thyroglobulin was investigated in sera with positive serology for Chagas' disease classified into groups (G) I, n = 7, with normal electrocardiogram (ECG) and no signs or symptoms of the disease; GII, n = 7, with ECG abnormalities but without cardiomegaly and GIII, n = 7, with cardiomegaly and congestive heart failure. Healthy individual sera were analyzed in parallel as controls. In the three groups of chagasic patients, a high proportion of sera exhibited an enhancement of IgG response anti actin ranging from 71 to 100%. IgM against this antigen was found positive in GI, 21%; GII and GIII, 57%. The antibodies binding to myosin and myoglobin were mainly of IgM type. When myosin was assayed, the frequency of reactive sera was gradually diminished as heart involvement increased: GI 57%, GII 28% and GIII 14%. Only IgG antibodies against thyroglobulin were detected in the three groups of chagasic patients ranging from 43 to 86%. IgG natural antibodies showed to be polyreactive, since a diminished reactivity against each one of the natural antigens assayed and against T. cruzi acidic antigens (FIV) was observed in the sera absorbed with any of the selected antigens irrespective of the absorbing ones. Moreover, the antibodies against FIV parasite's antigens purified by immunoabsorption showed a similar reactivity with FIV, myosin and actin, and a slight lower reactivity with thyroglobulin. These results indicate that in chagasic patients, the specific humoral response against FIV is associated with an increase of the natural autoantibodies along with their polyspecificity.

Trypanosoma cruzi: immunological cross-reactivity of the major cysteinyl proteinase (cruzipain) with a parasite cytosol acidic antigen (FIV)

This paper shows that a polyclonal monospecific rabbit antiserum to cruzipain, the major T. cruzi cystein proteinase, cross-reacts with a cytosol acidic antigen (F IV) isolated from the epimastigote stage of the same parasite. In addition, antibodies specific for F IV purified from chagasic patient sera or murine anti F IV sera, also react with cruzipain. This was demonstrated by ELISA, DOT-ELISA, native and electrophoretic Immunoblot. These findings suggest that F IV contains an antigen immunologically cross-reactive with cruzipain.

Chagas' disease cardioneuropathy: association of anti-Trypanosoma cruzi and anti-sciatic nerve antibodies

The aim of this work was to study whether Trypanosoma cruzi infection could elicit humoral immune response to the well-defined parasite antigen acidic fraction separated from T. cruzi cytosol by isoelectric focusing and designated fraction IV (FIV) and whether this response could account for some of the autoreactive immune response against peripheral nerve components. Chagasic patients with positive serology for Chagas' disease were classified as group I (n = 12) with normal electrocardiograms (ECG) and no signs of disease, group II (n = 12) with ECG abnormalities but without cardiomegaly, and group III (n = 12) with cardiomegaly and congestive heart failure. Sera from patients in group II showed the highest frequency of positive reactivity against FIV. Ninety-two percent had titers higher than 1/400 while the percentage for groups I and III was 50%. The autoreactive response against human sciatic nerve saline extract (SNS) was studied. The binding of IgG to SNS was positive in groups I (58%), II (66%), and III (75%) patients. The treatment of SNS with periodate diminished the ability of antigens to fix IgG from these chagasic patients. Absorption studies were performed to investigate whether FIV and SNS could have cross-reactive epitopes. Preabsorption of positive sera with FIV inhibited 48-69% of samples' reactivity against antigen. In contrast, preabsorption of positive sera with SNS inhibited only 12-23% of samples' reactivity against antigen. Overall, these results suggest that FIV-T. cruzi and sciatic nerve components possess some epitopes, possibly of a carbohydrate nature, in common. Thus, infection in Chagas' disease could overcome the tolerance to self components and could lead to autoimmunity.

Chagas' disease: IgG isotypes against Trypanosoma cruzi cytosol acidic antigens in patients with different degrees of heart damage

We studied the reactivity of IgG isotypes detected in sera from chronic Chagas' disease patients with a Trypanosoma cruzi cytosol acidic antigenic fraction (F IV) and parasite epimastigote forms (EPI). All patients studied had positive serology for Chagas' disease, with normal electrocardiogram (Group I), abnormal ECG without cardiomegaly (Group II), and abnormal ECG with cardiomegaly (Group III). The highest levels of antibodies were observed in sera from Group II patients. A high prevalence of IgG1 and IgG3, low levels of IgG2, and IgG4 isotypes against EPI were found in sera from all groups by ELISA. When the F IV was used as antigen, IgG1 was the main antibody isotype detected by ELISA in all groups of patients. The antigenic recognition patterns by IgG1 among the different clinical groups by immunoblotting of F IV revealed some differences. The sera from Group I recognized antigens of F IV of 80, 53, and 43 kDa. Sera from Group III recognized mainly one antigenic band of 43 kDa. Finally, sera from Group II showed greater diversity of binding by IgG1, detecting between one and six bands in the 80 and 30 kDa ranges.

Immune response in mice immunized with acidic antigenic fractions from Trypanosoma cruzi cytosol

The humoral and cellular immune responses as well as the resistance to infection with bloodstream forms of T. cruzi were studied in mice immunized with acidic antigenic fractions from parasite cytosol, F III and F IV, plus Bordetella pertussis as adjuvant. The immunization with F III induced positive ITH and DTH responses to homologous antigens. In mice immunized with F IV, the ITH was negative and four out of six animals presented positive DTH reactions. In both groups of mice the analysis of IgG against T. cruzi showed that the major isotype elicited was IgG1. Specific IgE was also detected in sera from F III immunized mice, thus confirming the presence of homocytotropic antibodies. The parasitemias reached by F III and F IV immunized mice after challenge were lower than those of the controls showing in this way a partial protection against the acute infection. The histological studies of heart and skeletal muscle performed two months after the infection revealed variable mononuclear infiltration in all infected mice despite immunization.

IgG isotype profiles induced in mice by two Trypanosoma cruzi electronegative antigens

In this work we studied the IgG isotypes induced in mice immunized with two Trypanosoma cruzi acidic antigenic fractions (F IV and Eas 4.5) and the level of protection to a later infection with parasites. F IV is a cytosolic antigen from epimastigotes, and Eas 4.5 is an exoantigen released by trypomastigotes. The most relevant epitopes of Eas 4.5 are carbohydrates. A high prevalence of IgG1, low levels of IgG3 and no IgG2 antibodies against F IV and Eas 4.5 were found in sera obtained 2 weeks after the last antigen dose from animals immunized with F IV (group I) or Eas 4.5 (group II). Immunized mice from both groups were infected with trypomastigotes, and the parasitemias detected later on were significantly lower than in control groups (p less than 0.01, group I; p less than 0.001, group II). The amount of IgG2-specific antibodies, which was only detected using epimastigotes as antigen in ELISA, was significantly increased after the infection, but no major changes were seen in the profiles of other isotypes.

Antibodies to T. cruzi cytosol acidic antigens (FIV) in Chagas' disease recognize parasite cell surface and human heart epitopes

The expression of T. cruzi electronegative antigens (FIV) on the parasite surface and their cross-reactivity with heart tissue antigens was studied. For the former purpose epimastigotes (EPI) treated with glutaraldehyde were used to absorb antibodies against surface antigens. Glutaraldehyde fixed heart tissue was used for absorption of antibodies in sera from two groups of chagasic patients with normal and altered electrocardiogram. The absorption of sera from normal electrocardiogram group with EPI significantly reduced the anti FIV activity by ELISA (p less than 0.001). The decreased reactivity was observed with the antigenic bands focused at pI about 4.5. Thus, the results indicate that chagasic patients without electrocardiographic alterations have a high percentage of antibodies reactive with T. cruzi cell surface antigens. Serum absorption with glutaraldehyde fixed heart tissue reduced the anti FIV activity from both groups of patients by ELISA and diminished the intensity of several bands focused at pI 4-6.

IgE dependent autoimmune response. Effect of Trypanosoma cruzi infection

The autoimmune response to mouse accessory glands (MAG) was investigated in male BALB/c mice immunized with different doses of chemically modified mouse accessory glands (MMAG) and complete Freund's adjuvant (CFA). This autoimmune response was studied at several time intervals using the skin test with MAG. It was found that 5 mg of MMAG induced on the day 15 an autoimmune response detected by specific skin test at 20 min., 3 h and 24 h. The results of the immediate type hypersensitivity (ITH) were higher than those with the other skin tests. In order to study the type of immunoglobulin involved, the ITH was also analyzed by passive cutaneous anaphylaxis (PCA) at different time intervals with treated and untreated sera at 56 degrees C. The findings suggest the presence of reaginic antibodies, IgE being the major antibody as detected by enzime linked immunosorbent assay (ELISA). The MAG was subsequently fractionated using Sephandex G-100 and the fractions thus obtained (FI,FII and FIII) were used to challenge mice immunized with MMAG. It was found that FI was the only fraction which revealed an ITH similar to that revealed by MAG. The effect of infection with Trypanosoma cruzi on the autoimmune response to MAG was analyzed with different mouse groups intraperitoneally treated with 2 x 10(3) blood trypomastigotes/animal at several time intervals: namely, on days -5, 0, +5 and +10 with respect to the immunization with MMAG. The autoimmune response to MAG showed suppression when the animals received the parasites on the same day as the autoantigen.

Human antibodies against Trypanosoma cruzi exoantigens recognizing parasite surface antigens and heart tissue components

This work describes the occurrence of antibodies against exoantigens of Trypanosoma cruzi in a high percentage of patients with chronic Chagas' disease. When analyzing selected groups of patients, it was observed that sera from individuals with electrocardiographic alterations showed a greater number of precipitin system and higher antibody titers than sera from patients with positive serology only. Partial characterization of exoantigens of T. cruzi was performed by isoelectric focusing and immunoblotting. Two distinct groups of antigens at pI around 5 and 6, respectively, were identified by these methods. It was also shown in absorption experiments that exoantigens of lower pI share epitopes with components of the cellular surface of epimastigotes of T. cruzi, whereas exoantigens of higher pI share epitopes with normal human heart tissue.

Characterization of Trypanosoma cruzi antigens recognized by sera from patients with chronic Chagas' disease

The aim of this work was to study the Trypanosoma cruzi antigens more reactive with antibodies from chagasic patients. For this purpose, the polypeptidic spectrum of cytosol was analyzed by isoelectric focusing. It showed about thirty bands distributed along a pH gradient of 3-10. In order to study the antigenicity of these polypeptides, four fractions from the focused cytosol were eluted and then analyzed by ELISA with chagasic and control sera. The more acidic and homogeneous fraction (FIV, pI 4-5,5) was the most reactive with antibodies from Chagas' disease patients. The 125I-labeled FIV was immunoprecipitated with chagasic and control human sera and subjected to SDS-PAGE analysis. The autoradiography revealed the presence of 4 major antigens, with apparent molecular weights of 49, 80, 86 and 110 kilodaltons only reactive with sera from chagasic patients. Two antigens with molecular weights of 34 and 21 kilodaltons were reactive with both chagasic and control sera.