Anti-Trypanosoma cruzi and anti-laminin antibodies in chagasic patients after specific treatment

Targeting circulating labile heme as a defense strategy against malaria

Severe presentations of malaria emerge as Plasmodium (P.) spp. parasites invade and lyse red blood cells (RBC), producing extracellular hemoglobin (HB), from which labile heme is released. Here, we tested whether scavenging of extracellular HB and/or labile heme, by haptoglobin (HP) and/or hemopexin (HPX), respectively, counter the pathogenesis of severe presentations of malaria. We found that circulating labile heme is an independent risk factor for cerebral and non-cerebral presentations of severe P. falciparum malaria in children. Labile heme was negatively correlated with circulating HP and HPX, which were, however, not risk factors for severe P. falciparum malaria. Genetic Hp and/or Hpx deletion in mice led to labile heme accumulation in plasma and kidneys, upon Plasmodium infection This was associated with higher incidence of mortality and acute kidney injury (AKI) in ageing but not adult Plasmodium-infected mice, and was corroborated by an inverse correlation between heme and HPX with serological markers of AKI in P. falciparum malaria. In conclusion, HP and HPX act in an age-dependent manner to prevent the pathogenesis of severe presentation of malaria in mice and presumably in humans.

ABO, Secretor and Lewis histo-blood group systems influence the digestive form of Chagas disease

Chagas disease, caused by Trypanosoma cruzi, can affect the heart, esophagus and colon. The reasons that some patients develop different clinical forms or remain asymptomatic are unclear. It is believed that tissue immunogenetic markers influence the tropism of T. cruzi for different organs. ABO, Secretor and Lewis histo-blood group systems express a variety of tissue carbohydrate antigens that influence the susceptibility or resistance to diseases. This study aimed to examine the association of ABO, secretor and Lewis histo-blood systems with the clinical forms of Chagas disease. We enrolled 339 consecutive adult patients with chronic Chagas disease regardless of gender (cardiomyopathy: n=154; megaesophagus: n=119; megacolon: n=66). The control group was composed by 488 healthy blood donors. IgG anti-T. cruzi antibodies were detected by ELISA. ABO and Lewis phenotypes were defined by standard hemagglutination tests. Secretor (FUT2) and Lewis (FUT3) genotypes, determined by Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), were used to infer the correct histo-blood group antigens expressed in the gastrointestinal tract. The proportions between groups were compared using the χ2 test with Yates correction and Fisher's exact test and the Odds Ratio (OR) and 95% Confidence Interval (95% CI) were calculated. An alpha error of 5% was considered significant with p-values <0.05 being corrected for multiple comparisons (pc). No statistically significant differences were found for the ABO (X2: 2.635; p-value=0.451), Secretor (X2: 0.056; p-value=0.812) or Lewis (X2: 2.092; p-value=0.351) histo-blood group phenotypes between patients and controls. However, B plus AB Secretor phenotypes were prevalent in pooled data from megaesophagus and megacolon patients (OR: 5.381; 95% CI: 1.230-23.529; p-value=0.011; pc=0.022) in comparison to A plus O Secretor phenotypes. The tissue antigen variability resulting from the combined action of ABO and Secretor histo-blood systems is associated with the digestive forms of Chagas disease.

Antibody drop in newborns congenitally infected by Trypanosoma cruzi treated with benznidazole

OBJECTIVE

To compare the drop of Chagas antibody titres between non-infected and congenitally infected newborns treated by two doses of benznidazole, aiming at evaluating the recovery time and giving recommendations regarding serological criteria of recovery.

METHODS

During a clinical trial, the drop of Trypanosoma cruzi antibody titres measured by ELISA tests was followed during the first year of life in congenitally infected newborns treated with different doses of benznidazole and compared to T. cruzi antibody titres in non-parasitaemic newborns. Confirmation of recovery was given by two negative serological tests: Chagas Stat-Pak (CSP) (immunochromatography) and Chagatest v3.0 (ELISA).

RESULTS

In non-parasitaemic infants of infected mothers, antibodies of maternal origin disappeared in <8 months while in infected infants, T. cruzi antibodies decreased more slowly and disappeared in 9-16 months allowing to confirm the recovery. All CSP tests were negative before the ninth month while about 10% of ELISA tests remained positive at the 12th month.

CONCLUSIONS

Recovery may be confirmed in most cases at 10 months. The CSP test was compared to Chagatest v3.0 ELISA and appeared to give a reliable response. The decrease rate of antibodies does not depend on treatment modes.

Parasite persistence in treated chagasic patients revealed by xenodiagnosis and polymerase chain reaction

Polymerase chain reaction (PCR) was compared with xenodiagnosis performed 20 years after trypanocidal chemotherapy to investigate parasite clearance. Eighty-five seropositive individuals for Chagas disease presenting a positive xenodiagnosis were treated with specific drugs; 37 in the acute phase and 48 in the chronic phase. Fifteen chronic asymptomatic patients received a placebo. Treatment in the acute phase led to PCR negative results in 73% of the cases, while xenodiagnosis was negative in 86%. In the chronic phase, PCR was negative in 65% of the patients and 83% led to xenodiagnosis negative results. Regarding the untreated group (placebo), 73% gave negative results by xenodiagnosis, of which 36% were positive by PCR. Individuals that were considered seronegative (n=10), presented unequivocally negative results in the PCR demonstrating the elimination of parasite DNA. Seventeen individuals had their antibodies titers decreased to such a level that the final results were considered as doubtful and 16 of them presented negative PCR. The molecular method represents a clear advantage over conventional techniques to demonstrate persistent infections in Chagas disease patients that underwent chemotherapy.

Enzyme-linked immunosorbent assay with Trypanosoma cruzi excreted-secreted antigens (TESA-ELISA) for serodiagnosis of acute and chronic Chagas' disease

In the present report we describe the use of Trypomastigote Excreted-Secreted Antigens (TESA) as antigen in ELISA for Chagas' disease serodiagnosis. The study was carried out on 284 patients, 164 of whom were nonchagasic subjects including individuals with leishmaniasis or other pathologies, and 120 chagasic patients, being 53 in the acute (with positive IgA and IgM antibodies to T. cruzi) and 67 in the chronic phase. TESA-ELISA showed 100% positivity in the survey of IgG antibodies in chagasic patients (acute and chronic) and 100% positivity for IgM antibodies in acute phase sera. TESA preparation does not require biochemical purification procedures and does not present the cross-reactivity of leishmaniasis sera observed when ELISA with epimastigote alkaline extract (EAE) is performed. ELISA competition assays showed that anti-T. cruzi antibodies of sera from chagasic patients that react with TESA are different from those that react with EAE. Besides, partial characterization of TESA showed that several epitopes present in this fraction are absent in EAE.

The role of blood group antigens in infectious diseases

The medical literature contains a large number of publications attempting to correlate blood groups with disease. Many of these reports are poorly documented and have limited scientific validity. Only a few agents, such as malaria parasites and parvovirus B19, infect red blood cells (RBCs) and precursors. Most other agents use RBCs as carriers to the target tissue. There is an excess of blood group A individuals among cancer patients compared with normal individuals; malignancy has also been associated with the Lewis antigen. Plasmodium vivax only enters RBCs when the Fy6 Duffy protein is present. Certain Escherichia coli organisms will only attach to epithelial cells carrying P or Dr blood group antigens. The P antigen Is also the receptor for parvovirus B19. Le(b) appears to be the receptor for Helicobacter pylori in gastric tissue. The high frequency blood group antigen AnWJ is the receptor for Haemophilus influenzae. Knowledge of the functions of RBC surface molecules Is expanding and the ability to generate experimental animals devoid of certain molecules will clarify their physiological role.

Relationship between ABO blood group and levels of Gal alpha,3Galactose-reactive human immunoglobulin G

BACKGROUND

The terminal Gal alpha1,3Galactose (alphaGal) determinant is present on all porcine glycoproteins and glycolipids, but is not expressed by human cells. Consequently human sera contain anti-alphaGal natural antibodies. The human blood group B antigen [Gal alpha1,3(Fuc1,2)Galactose] is differentiated from the alphaGal epitope by the presence of a fucosyl group.

METHODS

To determine whether the expression of the B antigen has any effect on the level of alphaGal-reactive natural antibodies, equal numbers (n=12) of A, B, AB, and O serum samples were evaluated by ELISA and flow cytometry.

RESULTS

A significant reduction in IgG alphaGal reactivity was observed with serum samples from B antigen-expressing donors (B, AB) relative to non-B antigen-expressing donors (A, O).

CONCLUSIONS

These results are consistent with the possibility that anti-alphaGal antibodies in non-B antigen-expressing individuals include a subset that is reactive with the structurally related B antigen and that this subset is absent in B and AB individuals.

Flow cytometry, a new approach to detect anti-live trypomastigote antibodies and monitor the efficacy of specific treatment in human Chagas' disease

Sera from patients chronically infected with Trypanosoma cruzi display antibodies that bind to epitopes of living trypomastigotes, known as lytic antibodies (LA), and are detected by a complement-mediated lysis test. Conventional serology antibodies (CSA) are also present in sera from patients with chronic infections but, in contrast to LA, are unable to recognize viable trypomastigotes. The presence of LA has been used as an important element in the criterion of cure in human Chagas' disease. Using flow cytometry technology, we introduced a new and sensitive immunomethod for the detection of anti-live trypomastigote membrane-bound antibodies. On the basis of serological tests (LA and CSA detection) and parasitological assays such as hemoculture (HE), patients were classified into the following groups: chronically infected untreated patients (NT) and treated not-cured patients (TNC), with positive HE and both LA and CSA in their sera; "dissociated" HE-negative patients (DIS), in whom LA was not detected whereas CSA were present; a group of cured HE-negative patients (CUR), who were both LA and CSA negative; and, as control, a group of non-chagasic individuals (NC). Sera from these patients were assayed by incubation with live bloodstream trypomastigotes, which were subsequently exposed to fluorescein isothiocyanate-conjugated anti-human immunoglobulin G. The parasites were then fixed, run in the cytometer, and identified on basis of their size and granularity gain adjustments. On the basis of experience with the complement-mediated lysis test, a level of 20% of parasites being fluorescein isothiocyanate fluorescence positive was used as a cutoff between effective and ineffective treatments. With this criterion, our results indicated that sera from NT and TNC patients were antibody positive whereas all sera from DIS, CUR, and NC patients did not contain membrane-bound antibodies. This new approach is a tool to easily identify anti-live T. cruzi membrane-bound antibodies that can be used to monitor the efficacy of Chagas' disease treatment.

Distribution of alpha-galactosyl-containing epitopes on Trypanosoma cruzi trypomastigote and amastigote forms from infected Vero cells detected by Chagasic antibodies

Reactivity of different Trypanosoma cruzi developmental forms with purified Chagasic anti-alpha-galactosyl antibodies (anti-Gal) was studied using epimastigotes from axenic cultures, trypomastigotes and amastigotes from infected Vero cell cultures, and an immunogold labeling method as observed by electron microscopy. Epimastigotes were poorly labeled, whereas extracellular trypomastigotes and amastigotes bound heterogeneously to the antibody with many cells being intensely labeled at the cell surface, including the membrane lining the cell body, the flagellum and the flagellar pocket. Parasites with poor labeling at the cell surface generally had several gold particles within the cell, mostly in cytoplasmic vacuoles. The Golgi complex of trypomastigotes was strongly labeled. Intracellular parasites were labeled at the parasite cell surface or within vacuolar structures. The expression in T. cruzi-infected Vero cells of alpha-galactosyl antigenic structures acquired from the parasite was shown by moderate labeling with Chagasic anti-Gal of the membrane lining parasite-free outward cell projections. The reactivity with purified anti-Gal from healthy individuals at the same concentrations of Chagasic anti-Gal was poor, with gold particles appearing in the nucleus and cytoplasm but not at the cell surface. It paralleled the labeling with Bandeireae simplicifolia IB-4 lectin. The results provide a basis for autoimmune reactions involving anti-Gal from chronic Chagasic patients.

Antibodies to laminin and immunohistochemical localization of laminin in chronic chagasic cardiomyopathy: a review

Antibodies against laminin were determined by ELISA in forty six patients suffering from Chagas' disease and twenty healthy persons (control group). The patients were divided into three groups according to the severity of clinical, electrocardiographic and echocardiographic studies. Histologic, ultrastructural and immunohistochemical studies were made of endomyocardial biopsy specimens from 10 of these patients with chronic Chagasic cardiomyopathy. Antibodies to laminin were detected in 50% of the patients in each of the three groups. However analysis of the data did not allow us to determine any significant correlation among the severity of the different clinical and non-invasive studies and the level of circulating antibodies to laminin. The highest titers of antilaminin antibodies were detected in the group with severe cardiological alterations (37% of the patients). Histological and electron microscopic observation of myocardial biopsies disclosed marked thickening of the basement membranes of the myocytes, endothelial cells and vascular smooth muscle cells. Light (peroxidase-labeled antibodies) and electron (gold-conjugated antibody) microscopic immunohistochemical methods revealed a positive reaction for laminin in these thickened basement membranes. This thickening may develop as a consequence of: a) an immunologic reaction which is triggered by the presence of a laminin-like molecule on the surfaces of T. cruzi amastigotes and trypomastigotes; b) an immunologic response to direct injury of basement membranes causing some of their components to become antigenic; c) myocardial fibrosis, with synthesis of new connective tissue components, and d) a combination of the preceding factors. The relationship of these changes to antilaminin antibodies remains unclear.(ABSTRACT TRUNCATED AT 250 WORDS)

Lytic antibody titre as a means of assessing cure after treatment of Chagas disease: a 10 years follow-up study

A complement-mediated lysis test (CoML) using living trypomastigotes was compared with conventional serological methods and with haemoculture. Over a 10 years follow-up period evidence was obtained which supported the view that chagasic patients, treated with nitroheterocyclic drugs, in whom CoML had reverted to negative, might be considered cured despite conventional serology remaining positive.

Glycoconjugates of Trypanosoma cruzi: a 74 kD antigen of trypomastigotes specifically reacts with lytic anti-alpha-galactosyl antibodies from patients with chronic Chagas disease

Protective, lytic antibodies are believed to be correlated with active Trypanosoma cruzi infection. In patients with chronic infection, antibodies lysing trypomastigote forms recognize chiefly alpha-galactosyl structures at the parasite surface. The target molecules on cell-derived trypomastigotes that react with anti-alpha-galactosyl antibodies (anti-Gal) from patients with chronic Chagas disease were investigated. Glycoconjugates were isolated from trypomastigotes and shown to absorb purified Chagasic (Ch) anti-Gel effectively as well as lytic antibodies from Ch sera. Active fractions were F2 (74 kD and 95.6 kD) and F3 (120-200 kD). A differential reactivity with antibodies from untreated Ch patients (trypanolytic) and from treated, presumably cured, individuals (not trypanolytic) was evident using F2 and F3 antigenic fractions. No cross-reactivity with heterologous sera (other infections) was observed. The F2 glycoconjugate (mostly 74 kD) can be used in the diagnosis of active Chagas infection, replacing the quantitative determination of complement-mediated lysis. With the present sample of patients' sera and normal human sera, it showed 100% sensitivity and specificity.

Direct lysis of Trypanosoma cruzi: a novel effector mechanism of protection mediated by human anti-gal antibodies

Anti-gal antibodies directed against a carbohydrate epitope present in mouse laminin (galactosyl alpha 1-3 galactose) and detected in high levels in sera from patients in the acute phase of Chagas disease are responsible for the direct lysis (DL) of Trypanosoma cruzi blood forms independent of either the classic or alternative complement pathways. Furthermore, the lectins Euonymus europaeus (EE) specific for the carbohydrates gal alpha 1-3 gal present a similar lytic activity against T. cruzi at the same concentrations of purified anti-gal antibodies. The DL activity was tested with several other lectins but Concanavalin A (Con A) specific for alpha-D-mannose and alpha-D-glucose was the only one also presenting lytic activity. The lectins and anti-gal antibodies lytic activity can be inhibited by specific carbohydrates suggesting that this phenomenon is related to the capability of these lectins or anti-gal antibodies to bind to a crucial surface component of T. cruzi. Moreover, the infectivity of T. cruzi blood forms to mice was clearly inactivated by incubation with acute chagasic sera (ACS) but not by ACS absorbed by immunoaffinity chromatography with mouse laminin, a strong evidence that high levels of anti-gal antibodies participate in the decline of the parasitaemia from the acute to the chronic phase in Chagas disease.

Distribution of carbohydrates recognized by the lectins Euonymus europaeus and concanavalin A in monoxenic and heteroxenic trypanosomatids

We observed a wide distribution of the carbohydrate epitopes galactosyl alpha(1-3)galactose (gal alpha1-3 gal), alpha-glucoside and alpha-mannoside in mono- and heteroxenic trypanosomatids by using fluorescein-labelled lectins of Euonymus europaeus (EE) and Concanavalin A (Con A) as well as sera from acute chagasic patients who have very high levels of anti-gal alpha(1-3)gal antibodies. The direct fluorescence test for gal alpha1-3 gal with EE was positive at minimum concentrations of 6 micrograms/ml for heteroxenic trypanosomatids and 0.7 micrograms/ml for monoxenic ones and for the plant parasite, Phytomonas. On the other hand, heteroxenic trypanosomatids that infect vertebrates bound ten-fold more Con A than monoxenic flagellates and Phytomonas. These data were confirmed in ELISA and Western Blot assays carried out with peroxidase-labelled EE and Con A. Euonymus europaeus recognized several glycoproteins in all trypanosomatids that we tested. Con A, however, recognized a glycoprotein cluster in heteroxenic protozoa, which ranging from 60-120 kDa, seemed to lack monoxenic parasites and Phytomonas. These findings suggest that alpha-D-mannose and alpha-D-glucose might play an important role in the interaction between trypanosomatids and vertebrate hosts.

Immunocytochemical identification of Leishmania and Trypanosoma cruzi amastigotes in situ with homologous and heterologous polyclonal antibodies

The unlabelled antibody peroxidase-antiperoxidase method was used to study the immunocytochemical properties of Leishmania and Trypanosoma cruzi amastigotes in situ after tissues had been submitted to different fixation procedures. Antisera were obtained from rabbits chronically infected with different strains of T. cruzi or immunized with L. mexicana amazonensis and L. braziliensis guyanensis, and were applied on 5 microns thick sections. T. cruzi antigens were well stained by the three anti-T. cruzi sera and the two anti-Leishmania sera at optimum dilution between 1:1,000 and 1:2,000, regardless the parasite strain. Differently, the leishmanial antigens were revealed by anti-Leishmania sera only at low dilutions (between 1:60-1:160), whereas the anti-T. cruzi sera, at these low dilutions, gave rather weak stainings. Although there is no clear explanation for this immunocytochemical "reverse-monodirectional" cross-reactivity between Leishmania and T. cruzi, the present results show that polyclonal antibodies agains Leishmania species, when used for immunocytochemical detection of these parasites in situ, react more strongly with T. cruzi amastigotes than with the homologous amastigotes.