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

Chagas Disease and Heart Failure: An Expanding Issue Worldwide

Chagas disease, originally a South American endemic health problem, is expanding worldwide because of people migration. Its main impact is on the cardiovascular system, producing myocardial damage that frequently results in heart failure. Pathogenic pathways are mainly related to inmunoinflamatory reactions in the myocardium and, less frequently, in the gastrointestinal tract. The heart usually shows fibrosis, producing dilatation and damage of the electrogenic cardiac system. These changes result in cardiomyopathy with heart failure and frequent cardiac arrhythmias and heart blocks. Diagnosis of the disease must include a lab test to detect the parasite or its immune reactions and the usual techniques to evaluate cardiac function. Therapeutic management of Chagas heart failure does not differ significantly from the most common treatment for dilated cardiomyopathy, with special focus on arrhythmias and several degrees of heart block. Heart transplantation is reserved for end-stage cases. Major international scientific organisations are delivering recommendations for prevention and early diagnosis. This article provides an analysis of epidemiology, prevention, treatment and the relationship between Chagas disease and heart failure.

Chagas Cardiomyopathy: An Update of Current Clinical Knowledge and Management: A Scientific Statement From the American Heart Association

Background:

Chagas disease, resulting from the protozoan Trypanosoma cruzi , is an important cause of heart failure, stroke, arrhythmia, and sudden death. Traditionally regarded as a tropical disease found only in Central America and South America, Chagas disease now affects at least 300 000 residents of the United States and is growing in prevalence in other traditionally nonendemic areas. Healthcare providers and health systems outside of Latin America need to be equipped to recognize, diagnose, and treat Chagas disease and to prevent further disease transmission.

Methods and Results:

The American Heart Association and the Inter-American Society of Cardiology commissioned this statement to increase global awareness among providers who may encounter patients with Chagas disease outside of traditionally endemic environments. In this document, we summarize the most updated information on diagnosis, screening, and treatment of T cruzi infection, focusing primarily on its cardiovascular aspects. This document also provides quick reference tables, highlighting salient considerations for a patient with suspected or confirmed Chagas disease.

Conclusions:

This statement provides a broad summary of current knowledge and practice in the diagnosis and management of Chagas cardiomyopathy. It is our intent that this document will serve to increase the recognition of Chagas cardiomyopathy in low-prevalence areas and to improve care for patients with Chagas heart disease around the world.

Vimentin and Anti Vimentin Antibodies in Chagas' Disease

Background

Vimentin is a main structural protein of the cell, a component of intermediate cell filaments and immersed in cytoplasm. Vimentin is mimicked by some bacterial proteins and anti-vimentin antibodies occur in autoimmune cardiac disease, as rheumatic fever. In this work we studied vimentin distribution on LLC-MK2 cells infected with T. cruzi and anti-vimentin antibodies in sera from several clinical pictures of Chagas' disease or American Trypanosomiasis, in order to elucidate any vimentin involvement in the humoral response of this pathology.

Objective

We standardized an indirect immunofluorescence assay (IFI) to determine sub cellular expression in either parasites and host cells, and ELISA to evaluate anti-vimentin antibodies in sera fron chagasic patients.

Methods

We analyzed the distribution of vimentin in culture cells using indirect fluorescent assays, using as external controls anti-T. cruzi sera, derived from chronic infected patients for identification of the parasites in the same model. After infection and growth of T.cruzi amastigotes, those cells express larger amounts of vimentin, with heavy staining of cytoplasm outside the parasitophorous vacuole and some particle shadowing patterns, suggesting that vimentin are associated with cell cytoplasm. Anti-vimentin antibodies were present in most American trypanosomiasis samples, but notably, they are much more present in acute (76, 9%) or clinical defined syndromes, especially cardiac disease (87, 9%). Paradoxically, they were relatively infrequent in asymptomatic (25%) infected patients, which had a clearly positive serological reaction to parasite antigens, but had low frequency of anti-vimentin antibodies, similar to controls (2,5%).

Conclusion

Our current data revealed that anti-vimentin antibodies induced during T. cruzi infection could be a marker of active disease in the host and its levels could also justify drug therapy in American Trypanosomiasis chronic infection, as a large group of asymptomatic patients would be submitted to treatment with frequent adverse reactions of the available drugs. Anti-vimentin antibodies could be a marker of cardiac muscle cell damage, appearing in American Trypanosomiasis patients during active muscle cell damage.

Secretome analysis of Trypanosoma cruzi by proteomics studies

Background

Chagas disease is a debilitating often fatal disease resulting from infection by the protozoan parasite Trypanosoma cruzi. Chagas disease is endemic in 21 countries of the Americas, and it is an emerging disease in other countries as a result of migration. Given the chronic nature of the infection where intracellular parasites persist for years, the diagnosis of T. cruzi by direct detection is difficult, whereas serologic tests though sensitive may yield false-positive results. The development of new rapid test based on the identification of soluble parasitic antigens in serum would be a real innovation in the diagnosis of Chagas disease.

Methods

To identify new soluble biomarkers that may improve diagnostic tests, we investigated the proteins secreted by T. cruzi using mass spectrometric analyses of conditioned culture media devoid of serum collected during the emergence of trypomastigotes from infected Vero cells. In addition, we compared the secretomes of two T. cruzi strains from DTU Tc VI (VD and CL Brener).

Results

Analysis of the secretome collected during the emergence of trypomastigotes from Vero cells led to the identification of 591 T. cruzi proteins. Three hundred sixty three proteins are common to both strains and most belong to different multigenic super families (i.e. TcS, GP63, MASP, and DGF1). Ultimately we have established a list of 94 secreted proteins, common to both DTU Tc VI strains that do not belong to members of multigene families.

Conclusions

This study provides the first comparative analysis of the secretomes from two distinct T. cruzi strains of DTU TcVI. This led us to identify a subset of common secreted proteins that could potentially serve as serum markers for T. cruzi infection. Their potential could now be evaluated, with specific antibodies using sera collected from patients and residents from endemic regions.

Evolution of anti-Trypanosoma cruzi antibody production in patients with chronic Chagas disease: Correlation between antibody titers and development of cardiac disease severity

Chagas disease is one of the most important endemic infections in Latin America affecting around 6–7 million people. About 30–50% of patients develop the cardiac form of the disease, which can lead to severe cardiac dysfunction and death. In this scenario, the identification of immunological markers of disease progression would be a valuable tool for early treatment and reduction of death rates. In this observational study, the production of anti-Trypanosoma cruzi antibodies through a retrospective longitudinal follow-up in chronic Chagas disease patients´ cohort and its correlation with disease progression and heart commitment was evaluated. Strong inverse correlation (ρ = -0.6375, p = 0.0005) between anti-T. cruzi IgG₁ titers and left ventricular ejection fraction (LVEF) in chronic Chagas cardiomyopathy (CCC) patients were observed after disease progression. Elevated levels of anti-T. cruzi IgG₃ titers were detected in all T. cruzi-infected patients, indicating a lack of correlation of this IgG isotype with disease progression. Furthermore, low levels of anti-T. cruzi IgG₂, IgG₄, and IgA were detected in all patients through the follow-up. Although without statistical significance anti-T. cruzi IgE tends to be more reactive in patients with the indeterminate form (IND) of the disease (p = 0.0637). As this study was conducted in patients with many years of chronic disease no anti-T. cruzi IgM was detected. Taken together, these results indicate that the levels of anti-T. cruzi IgG₁ could be considered to seek for promising biomarkers to predict the severity of chronic Chagas disease cardiomyopathy.

Trypanosoma cruzi is the etiological agent of Chagas disease that affects about 7 million people in Latin America, being considered one of the most important neglected diseases of developing countries. Chronic Chagas disease might be present in different forms as an asymptomatic indeterminate form or even with severe cardiac commitment, known as chronic Chagas cardiomyopathy. In fact, the cardiac form can lead to death due to disease progression. Seeking for biomarkers of cardiomyopathy progression has become important to understand the cardiac progression and to predict or even prevent the disease worsening and to improve the quality of life of affected individuals. In this work, we followed the anti-T. cruzi antibody profile in a retrospective longitudinal study in a cohort of chronic Chagas disease patients, and further correlate with heart commitment and cardiac disease progression. We found an inverse correlation between anti-T. cruzi IgG₁ titers and cardiac disease severity in patients with progressive disease. These data suggest that anti-T. cruzi IgG₁ levels could be considered a suitable candidate tool for early identification of cardiac disease progression.

Leptomonas seymouri and Crithidia fasciculata exoantigens can discriminate human cases of visceral leishmaniasis from American tegumentary leishmaniasis ones

Exoantigens (exo) from Leptomonas seymouri and Crithidia fasciculata were used in an enzyme linked immunosorbent assay (ELISA), showing 100% reactivity with sera from visceral leishmaniasis (VL) cases, and no reactivity with American tegumentary leishmaniasis (ATL) ones. Our results have indicated that these exoantigens can be applied in the discrimination of VL and ATL cases.

Characterization and Diagnostic Application of Trypanosoma cruzi Trypomastigote Excreted-Secreted Antigens Shed in Extracellular Vesicles Released from Infected Mammalian Cells

Chagas disease, caused by Trypanosoma cruzi, although endemic in many parts of Central and South America, is emerging as a global health threat through the potential contamination of blood supplies. Consequently, in the absence of a gold standard assay for the diagnosis of Chagas disease, additional antigens or strategies are needed. A proteomic analysis of the trypomastigote excreted-secreted antigens (TESA) associated with exosomal vesicles shed by T. cruzi identified ∼80 parasite proteins, with the majority being trans-sialidases. Mass spectrometry analysis of immunoprecipitation products performed using Chagas immune sera showed a marked enrichment in a subset of TESA proteins. Of particular relevance for diagnostic applications were the retrotransposon hot spot (RHS) proteins, which are absent in Leishmania spp., parasites that often confound diagnosis of Chagas disease. Interestingly, serological screens using recombinant RHS showed a robust immunoreactivity with sera from patients with clinical stages of Chagas ranging from asymptomatic to advance cardiomyopathy and this immunoreactivity was comparable to that of crude TESA. More importantly, no cross-reactivity with RHS was detected with sera from patients with malaria, leishmaniasis, toxoplasmosis, or African sleeping sickness, making this protein an attractive reagent for diagnosis of Chagas disease.

Virus-like Particle Display of the α-Gal Epitope for the Diagnostic Assessment of Chagas Disease

The α-Gal antigen [Galα(1,3)Galβ(1,4)GlcNAcα] is an immunodominant epitope displayed by infective trypomastigote forms of Trypanosoma cruzi, the causative agent of Chagas disease. A virus-like particle displaying a high density of α-Gal was found to be a superior reagent for the ELISA-based serological diagnosis of Chagas disease and the assessment of treatment effectiveness. A panel of sera from patients chronically infected with T. cruzi, both untreated and benznidazole-treated, was compared with sera from patients with leishmaniasis and from healthy donors. The nanoparticle-α-Gal construct allowed for perfect discrimination between Chagas patients and the others, avoiding false negative and false positive results obtained with current state-of-the-art reagents. As previously reported with purified α-Gal-containing glycosylphosphatidylinositol-anchored mucins, the current study also showed concentrations of anti-α-Gal IgG to decrease substantially in patients receiving treatment with benznidazole, suggesting that the semiquantitative assessment of serum levels of this highly abundant type of antibody can report on disease status in individual patients.

Evaluation of Leishmania (Leishmania) infantum excreted-secreted antigens for detection of canine leishmaniasis

The efficacy of tests with L. (L.) infantum excreted-secreted antigens (ESA) to detect canine leishmaniasis (CanL) was evaluated using immunoblotting (ESA-blot), ELISA (ESA-ELISA) and ELISA with alkaline extract from promastigotes (PAE). Of one hundred fifty-five domestic dogs tested, 100 were suspected of CanL, 23 had other diseases and 32 were healthy. Sera from the dogs suspected of CanL were tested by immunohistochemistry (IHC), and 54% were confirmed to be infected by L. (L.) infantum (38 symptomatic and 16 asymptomatic). Of these, 100% were positive by ESA-blot, ESA-ELISA and PAE-ELISA. In the ESA-blot their sera recognized polypeptides in the 26.5-31.5kDa region. Of the 46% of dogs with negative IHC, 44-53% tested positive in all three tests irrespective of clinical status. The twenty-three dogs with other diseases were negative by ESA-blot, but sera from 9% and 26% of them reacted with ESA-ELISA and PAE-ELISA, respectively. The 32 healthy dogs were negative in all the tests. ESA-blot showed good correlation with IHC in the detection of CanL and a high specificity index.

Prevalence and Transmission of Trypanosoma cruzi in People of Rural Communities of the High Jungle of Northern Peru

Background

Vector-borne transmission of Trypanosoma cruzi is seen exclusively in the Americas where an estimated 8 million people are infected with the parasite. Significant research in southern Peru has been conducted to understand T. cruzi infection and vector control, however, much less is known about the burden of infection and epidemiology in northern Peru.

Methodology

A cross-sectional study was conducted to estimate the seroprevalence of T. cruzi infection in humans (n=611) and domestic animals [dogs (n=106) and guinea pigs (n=206)] in communities of Cutervo Province, Peru. Sampling and diagnostic strategies differed according to species. An entomological household study (n=208) was conducted to identify the triatomine burden and species composition, as well as the prevalence of T. cruzi in vectors. Electrocardiograms (EKG) were performed on a subset of participants (n=90 T. cruzi infected participants and 170 age and sex-matched controls). The seroprevalence of T. cruzi among humans, dogs, and guinea pigs was 14.9% (95% CI: 12.2 – 18.0%), 19.8% (95% CI: 12.7- 28.7%) and 3.3% (95% CI: 1.4 – 6.9%) respectively. In one community, the prevalence of T. cruzi infection was 17.2% (95% CI: 9.6 - 24.7%) among participants < 15 years, suggesting recent transmission. Increasing age, positive triatomines in a participant's house, and ownership of a T. cruzi positive guinea pig were independent correlates of T. cruzi infection. Only one species of triatomine was found, Panstrongylus lignarius, formerly P. herreri. Approximately forty percent (39.9%, 95% CI: 33.2 - 46.9%) of surveyed households were infested with this vector and 14.9% (95% CI: 10.4 - 20.5%) had at least one triatomine positive for T. cruzi. The cardiac abnormality of right bundle branch block was rare, but only identified in seropositive individuals.

Conclusions

Our research documents a substantial prevalence of T. cruzi infection in Cutervo and highlights a need for greater attention and vector control efforts in northern Peru.

Chagas disease causes significant morbidity and mortality throughout Central and South America. The epidemiology and control of this disease is subject to unique regional particularities, including the behavior and ecology of the local insect vector species. Significant resources have been allocated towards research and control efforts in southern Peru, yet very little is known about the prevalence and epidemiology of Trypanosoma cruzi in northern Peru. Our study highlights significant T. cruzi infection in northern Peru and is one of the first to document substantial transmission by the insect Panstrongylus lignarius. Our results illustrate major gaps in knowledge and the need for public health interventions targeted at Chagas disease in the region of Cutervo Province of northern Peru.

Trypanosoma cruzi-infected pregnant women without vector exposure have higher parasitemia levels: implications for congenital transmission risk

BACKGROUND

Congenital transmission is a major source of new Trypanosoma cruzi infections, and as vector and blood bank control continue to improve, the proportion due to congenital infection will grow. A major unanswered question is why reported transmission rates from T. cruzi-infected mothers vary so widely among study populations. Women with high parasite loads during pregnancy are more likely to transmit to their infants, but the factors that govern maternal parasite load are largely unknown. Better understanding of these factors could enable prioritization of screening programs to target women most at risk of transmission to their infants.

METHODOLOGY/PRINCIPAL FINDINGS

We screened pregnant women presenting for delivery in a large urban hospital in Bolivia and followed infants of infected women for congenital Chagas disease. Of 596 women screened, 128 (21.5%) had confirmed T. cruzi infection; transmission occurred from 15 (11.7%) infected women to their infants. Parasite loads were significantly higher among women who transmitted compared to those who did not. Congenital transmission occurred from 31.3% (9/29), 15.4% (4/26) and 0% (0/62) of women with high, moderate and low parasite load, respectively (χx2 for trend 18.2; p<0.0001). Twin births were associated with higher transmission risk and higher maternal parasite loads. Infected women without reported vector exposure had significantly higher parasite loads than those who had lived in an infested house (median 26.4 vs 0 parasites/mL; p<0.001) with an inverse relationship between years of living in an infested house and parasite load.

CONCLUSIONS/SIGNIFICANCE

We hypothesize that sustained vector-borne parasite exposure and repeated superinfection by T. cruzi may act as an immune booster, allowing women to maintain effective control of the parasite despite the down-regulation of late pregnancy.

Canine visceral leishmaniasis and Chagas disease among dogs in Araguaína, Tocantins

The present study analyzed serum samples from 111 male and female dogs of various ages from the municipality of Araguaína in the State of Tocantins, Brazil. Serological diagnosis of canine visceral leishmaniasis (CVL) was initially performed at the Central Laboratory (Laboratório Central - LACEN) of Araguaína, resulting in 61 positive samples by an indirect immunofluorescence assay (IIFA) (≥1:40) and 50 non-reactive samples. The same samples were analyzed at the São Paulo Institute of Tropical Medicine (Instituto de Medicina Tropical de São Paulo - IMTSP) by an enzyme-linked-immunosorbent assay (ELISA), resulting in 57 positive samples (51.35%) and 54 negative samples (48.64%). The Kappa coefficient of agreement between the tests was 0.74. The serum samples were also subjected to a diagnostic assay for Trypanosoma cruzi (Trypomastigote Excreted/Secreted Antigens -TESA-blot) that detected five suspect animals; three of those animals were positive for leishmaniasis by ELISA but negative by IIFA. These findings suggest that the canine population of Araguaína may be simultaneously infected with Leishmania chagasi and T. cruzi. The results obtained demonstrate the difficulty of using serology to detect CVL, thus emphasizing the necessity for a reference test to diagnose CVL, particularly in regions where the infection is endemic.

Chagas disease in Latin American immigrants with dilated cardiomyopathy in New York City

Chagas disease-associated cardiomyopathy is clinically similar to other causes of cardiomyopathy and, therefore, the diagnosis can be easily overlooked. We found a 13% point prevalence of Chagas disease in a sample of New York City immigrants with dilated cardiomyopathy.

Conventional serological performance in diagnosis of Chagas’ disease in southern Brazil

Results of Chagas’ disease diagnosis show disagreement. The aim of this study was to compare commercial tests for Chagas’ disease serodiagnosis in southern Brazil. A total of 161 samples were evaluated. Three enzyme-linked immunosorbent assays, one indirect hemagglutination and one indirect immunofluorescence were assessed. Trypomastigote excreted-secreted antigen-blot was a confirmatory method. From 161 samples, 65.84% were positive in all tests, while 34.16% presents mismatch result in at least one of the tests. All techniques tested presented false-positive and/or false-negative results as follows: Enzyme-linked immunosorbent assay 1 had more false-positive results (lower specificity), indirect immunofluorescence had the highest rate of false-negative results (lower sensitivity), enzyme-linked immunosorbent assays had fewer false-negative results (higher sensitivity), while indirect hemagglutination showed no false-positive result (higher specificity). Knowing the characteristics of techniques make it possible to combine them and obtain more reliable diagnosis. Therefore, it seems useful to combine techniques for diagnosing this infection.

The efficacy of L. (L.) chagasi excreted-secreted antigens (ESAs) for visceral leishmaniasis diagnosis is due to low levels of cross-reactivity

The analysis of promastigote excreted-secreted antigen (ESA) reactivity with 53 visceral leishmaniasis (VL) cases showed that each sample reacted regardless of the antigen or the Leishmania species used in enzyme-linked immunosorbent assay (ELISA) displayed 100% positivity with the L. (L.) chagasi ESA-blot recognizing bands of molecular weight ranging from 26.5 to 31.5 kDa. The analysis of 160 non-visceral cases showed that 5% of the samples cross-reacted with the L. (L.) chagasi ESA-ELISA and 9.4% reacted with the ESA isolated from L. (L.) amazonensis and L. (V.) braziliensis, whereas a high cross-reaction ranging from 24.4% to 25% was observed with total crude promastigote antigens (PRO-ELISA). The ESA-blot of L. (L.) chagasi tested with non-visceral sera samples showed a cross-reaction with 8.8% of cases; most of these cases represented tegumentary leishmaniasis and only one acute chagasic case. These data lead us to recommend the use of ESA as an alternative antigen in VL diagnosis.

Development and Application of an ELISA Assay Using Excretion/Secretion Proteins from Epimastigote Forms of T. cruzi (ESEA Antigens) for the Diagnosis of Chagas Disease

An indirect enzyme-linked immunoabsorbent assay (ELISA) for Trypanosoma cruzi was developed using epimastigote secretion/excretion proteins (ESEA antigens) obtained from axenic culture supernatants. A panel of 120 serum samples from subjects with confirmed Chagas disease (n = 50), healthy controls (n = 50), and patients with other parasitic diseases (n = 20) was used to evaluate the new ESEA-based ELISA (ELISA(ESEA)). This new test had excellent sensitivity (98%) and acceptable specificity (88%). Cross-reactivity was observed largely in sera from subjects with Leishmania and Ascaris infections. Using Western blotting and epimastigotes from two distinct T. cruzi isolates, several polypeptide bands with molecular masses ranging from 50 to 220 kDa were detected in pooled chagasic sera. However, the band pattern for each isolate was different. These data suggest that an inexpensive and technically simple ELISA based on ESEA antigens is a promising new tool for the diagnosis of Chagas disease.

Posttherapeutic cure criteria in Chagas' disease: conventional serology followed by supplementary serological, parasitological, and molecular tests

We performed a critical study of conventional serology, followed by supplementary serological, parasitological, and molecular tests, to assess the response to etiologic treatment of Chagas' disease. A group of 94 Chagas' disease patients treated with benznidazole at least 10 years earlier were evaluated from the laboratory and clinical points of view. When conventional serology (enzyme-linked immunosorbent assay [ELISA], indirect immunofluorescence [IIF], and indirect hemagglutination [IHA]) and classic criteria (consistent results with any two of the three tests) or more rigorous criteria (consistent results from the three tests) were used, 10.6% and 8.5% of patients were considered treated and cured (TC) by classic and rigorous criteria, respectively. Patients were then evaluated using supplementary (recombinant ELISA and Trypanosoma cruzi excreted-secreted antigen blotting [TESA-blot]), parasitological (hemoculture), and molecular (PCR) tests. The results of recombinant ELISA were similar to those with the rigorous criterion (three consistent test results). The TESA-blot group showed a higher percentage (21.3%) of negative results than the groups defined by either cure criterion. Hemoculture and PCR gave negative results for all treated and cured (TC) patients, regardless of the criterion used. Recombinant ELISA and TESA-blot tests showed negative results for 70% and 87.5% of the patients categorized as TC by the classic and three-test criteria, respectively. For patients with discordant conventional serology, the supplementary serological and molecular tests were the decisive factor in determining therapeutic failure. Clinical evaluation showed that 62.5% of TC patients presented with the indeterminate form of the disease. Additionally, treated patients with negative TESA-blot results should be reevaluated later with all methodologies used here to verify whether TESA-blot is a reliable way to determine early parasitological cure of Chagas' disease.

Oral transmission of Chagas disease

Chagas disease is now an active disease in the urban centers of countries of nonendemicity and endemicity because of congenital and blood and/or organ transplantation transmissions and the reactivation of the chronic disease in smaller scale than vectorial transmission, reported as controlled in countries of endemicity. Oral transmission of Chagas disease has emerged in unpredictable situations in the Amazon region and, more rarely, in areas of nonendemicity where the domiciliary triatomine cycle was under control because of exposition of the food to infected triatomine and contaminated secretions of reservoir hosts. Oral transmission of Chagas disease is considered when >1 acute case of febrile disease without other causes is linked to a suspected food and should be confirmed by the presence of the parasite after direct microscopic examination of the blood or other biological fluid sample from the patient.

Acute and congenital Chagas disease

The acute phase of Chagas disease lasts 4-8 weeks and is characterized by microscopically detectable parasitaemia. Symptoms are usually mild with severe acute disease occurring in less than 1% of patients. Orally transmitted Trypanosoma cruzi outbreaks can have more severe acute morbidity and higher mortality than vector-borne infection. Congenital T. cruzi infection occurs in 1-10% of infants of infected mothers. Most congenital infections are asymptomatic or cause non-specific signs, requiring laboratory screening for detection. A small proportion of congenital infections cause severe morbidity with hepatosplenomegaly, anaemia, meningoencephalitis and/or respiratory insufficiency, with an associated high mortality. Infected infants are presumed to carry the same 20-30% lifetime risk of cardiac or gastrointestinal disease as other infected individuals. Most control programs in Latin America employ prenatal serological screening followed by microscopic examination of cord blood from infants of seropositive mothers. Recent data confirm that polymerase chain reaction (PCR) is more sensitive and detects congenital infections earlier than conventional techniques. For infants not diagnosed at birth, conventional serology is recommended at at 6 to 9 months of age. In programs that have been evaluated, less than 20% of at risk infants completed all steps of the screening algorithm. A sensitive, specific and practical screening test for newborns is needed to enable Chagas disease to be added to newborn screening programs.

Cavia porcellus as a model for experimental infection by Trypanosoma cruzi

The guinea pig (Cavia porcellus) is a natural reservoir for Trypanosoma cruzi but has seldom been used as an experimental infection model. We developed a guinea pig infection model for acute and chronic Chagas disease. Seventy-two guinea pigs were inoculated intradermally with 10(4) trypomastigotes of T. cruzi strain Y (experimental group); 18 guinea pigs were used as control group. Eight animals from the experimental group and two from the control group were sacrificed 5, 15, 20, 25, 40, 55, 115, 165, and 365 days after inoculation. During the acute phase (15 to 55 days), we observed parasitemia (with a peak on day 20) and positive IgM and IgG Western blots with anti-shed acute-phase antigen bands. The cardiac tissue showed vasculitis, necrosis (on days 40 to 55), moderate to severe inflammation, and abundant amastigote nests. Smaller numbers of amastigote nests were also present in kidney, brain, and other organs. In the early chronic phase (115 to 165 days), parasitemia disappeared and anti-T. cruzi IgG antibodies were still detectable. In cardiac tissue, the number of amastigote nests and the grade of inflammation decreased. In the chronic phase (365 days), the cardiac tissue showed vasculitis and fibrosis; detectable parasite DNA was associated with higher grades of inflammation. The experimental T. cruzi infection model in guinea pigs shows kinetics and pathologic changes similar to those of the human disease.

Biosensors as rapid diagnostic tests for tropical diseases

Effective diagnosis of infectious pathogens is essential for disease identification and subsequent adequate treatment, to prevent drug resistance and to adopt suitable public health interventions for the prevention and control of epidemic outbreaks. Particular situations under which medical diagnostics operate in tropical environments make the use of new easy-to-use diagnostic tools the preferred (or even unique) option. These diagnostic tests and devices, usually based on biosensing methods, are being increasingly exploited as promising alternatives to classical, "heavy" lab instrumentation for clinical diagnosis, allowing simple, inexpensive and point-of-care testing. However, in many developing countries the lack of accessibility and affordability for many commercial diagnostic tests remains a major cause of high disease burden in such regions. We present a comprehensive overview about the problems of conventional medical diagnosis of infectious pathologies in tropical regions, while pointing out new methods and analytical tools for in-the-field and decentralized diagnosis of current major infectious tropical diseases. The review includes not only biosensor-based rapid diagnostic tests approved by regulatory entities and already commercialized, but also those at the early stages of research.

Anti-triatomine saliva immunoassays for the evaluation of impregnated netting trials against Chagas disease transmission

Insecticide-impregnated nets can kill triatomine bugs, but it remains unclear whether they can protect against Chagas disease transmission. In a field trial in Quequeña, Peru, sentinel guinea pigs placed in intervention enclosures covered by deltamethrin-treated nets showed significantly lower antibody responses to saliva of Triatoma infestans compared with animals placed in pre-existing control enclosures. Our results strongly suggest that insecticide-treated nets prevent triatomine bites and can thereby protect against infection with Trypanosoma cruzi. Anti-salivary immunoassays are powerful new tools to evaluate intervention strategies against Chagas disease.

ELISA versus PCR for diagnosis of chronic Chagas disease: systematic review and meta-analysis

Background

Most current guidelines recommend two serological tests to diagnose chronic Chagas disease. When serological tests are persistently inconclusive, some guidelines recommend molecular tests. The aim of this investigation was to review chronic Chagas disease diagnosis literature and to summarize results of ELISA and PCR performance.

Methods

A systematic review was conducted searching remote databases (MEDLINE, LILACS, EMBASE, SCOPUS and ISIWeb) and full texts bibliography for relevant abstracts. In addition, manufacturers of commercial tests were contacted. Original investigations were eligible if they estimated sensitivity and specificity, or reliability -or if their calculation was possible - of ELISA or PCR tests, for chronic Chagas disease.

Results

Heterogeneity was high within each test (ELISA and PCR) and threshold effect was detected only in a particular subgroup. Reference standard blinding partially explained heterogeneity in ELISA studies, and pooled sensitivity and specificity were 97.7% [96.7%-98.5%] and 96.3% [94.6%-97.6%] respectively. Commercial ELISA with recombinant antigens studied in phase three investigations partially explained heterogeneity, and pooled sensitivity and specificity were 99.3% [97.9%-99.9%] and 97.5% [88.5%-99.5%] respectively. ELISA's reliability was seldom studied but was considered acceptable. PCR heterogeneity was not explained, but a threshold effect was detected in three groups created by using guanidine and boiling the sample before DNA extraction. PCR sensitivity is likely to be between 50% and 90%, while its specificity is close to 100%. PCR reliability was never studied.

Conclusions

Both conventional and recombinant based ELISA give useful information, however there are commercial tests without technical reports and therefore were not included in this review. Physicians need to have access to technical reports to understand if these serological tests are similar to those included in this review and therefore correctly order and interpret test results. Currently, PCR should not be used in clinical practice for chronic Chagas disease diagnosis and there is no PCR test commercially available for this purpose. Tests limitations and directions for future research are discussed.

Diagnosis of Chagas disease: what has been achieved? What remains to be done with regard to diagnosis and follow up studies?

In the acute phase and in the chronic forms of Chagas disease, the etiological diagnosis may be performed by detection of the parasite using direct or indirect parasitological methods and by the presence of antibodies in the serum by way of serological tests. Several techniques are easily available, ranging from the simplest wet smear preparation to immuno-enzymatic assays with recombinant antigens that will meet most diagnostic needs. Other tests under evaluation include a molecular test using polymerase chain reaction, which has shown promising results and may be used as a confirmatory test both in the acute and chronic phases of the disease. Better rapid tests are needed for diagnosis, some of which are already under evaluation. Additionally, there is a need for tools that can identify patients cured shortly after specific treatment. Other needs include a marker for prognosis and early diagnosis of congenital transmission.

Diagnosis of parasitic diseases: old and new approaches

Methods for the diagnosis of infectious diseases have stagnated in the last 20–30 years. Few major advances in clinical diagnostic testing have been made since the introduction of PCR, although new technologies are being investigated. Many tests that form the backbone of the “modern” microbiology laboratory are based on very old and labour-intensive technologies such as microscopy for malaria. Pressing needs include more rapid tests without sacrificing sensitivity, value-added tests, and point-of-care tests for both high- and low-resource settings. In recent years, research has been focused on alternative methods to improve the diagnosis of parasitic diseases. These include immunoassays, molecular-based approaches, and proteomics using mass spectrometry platforms technology. This review summarizes the progress in new approaches in parasite diagnosis and discusses some of the merits and disadvantages of these tests.

Congenital Trypanosoma cruzi transmission in Santa Cruz, Bolivia

BACKGROUND

We conducted a study of congenital Trypanosoma cruzi infection in Santa Cruz, Bolivia. Our objective was to apply new tools to identify weak points in current screening algorithms, and find ways to improve them.

METHODS

Women presenting for delivery were screened by rapid and conventional serological tests. For infants of infected mothers, blood specimens obtained on days 0, 7, 21, 30, 90, 180, and 270 were concentrated and examined microscopically; serological tests were performed for the day 90, 180, and 270 specimens. Maternal and infant specimens, including umbilical tissue, were tested by polymerase chain reaction (PCR) targeting the kinetoplast minicircle and by quantitative PCR.

RESULTS

Of 530 women, 154 (29%) were seropositive. Ten infants had congenital T. cruzi infection. Only 4 infants had positive results of microscopy evaluation in the first month, and none had positive cord blood microscopy results. PCR results were positive for 6 (67%) of 9 cord blood and 7 (87.5%) of 8 umbilical tissue specimens. PCR-positive women were more likely to transmit T. cruzi than were seropositive women with negative PCR results (P < .05). Parasite loads determined by quantitative PCR were higher for mothers of infected infants than for seropositive mothers of uninfected infants P < .01). Despite intensive efforts, only 58% of at-risk infants had a month 9 specimen collected.

CONCLUSIONS

On the basis of the low sensitivity of microscopy in cord blood and high rate of loss to follow-up, we estimate that current screening programs miss one-half of all infected infants. Molecular techniques may improve early detection.

TESA-blot for the diagnosis of Chagas disease in dogs from co-endemic regions for Trypanosoma cruzi, Trypanosoma evansi and Leishmania chagasi

We standardized serodiagnosis of dogs infected with Trypanosoma cruzi using TESA (trypomastigote excreted-secreted antigen)-blot developed for human Chagas disease. TESA-blot showed 100% sensitivity and specificity. In contrast, ELISA using TESA (TESA-ELISA) or epimastigotes (epi-ELISA) as antigen yielded 100% sensitivity but specificity of 94.1% and 49.4%, respectively. When used in field studies in an endemic region for Chagas disease, visceral leishmaniasis and Trypanosoma evansi (Mato Grosso do Sul state, Central Brazil), positivities were 9.3% for TESA-blot, 10.7% for TESA-ELISA and 32% for epi-ELISA. Dogs from a non-endemic region for these infections (Rondonia state, western Amazonia) where T. cruzi is enzootic showed positivity of 4.5% for TESA-blot and epi-ELISA and 6.8% for TESA-ELISA. Sera from urban dogs from Santos, São Paulo, where these diseases are absent, yielded negative results. TESA-blot was the only method that distinguished dogs infected with T. cruzi from those infected with Leishmania chagasi and/or Trypanosoma evansi.

False-positive results of a rapid K39-based strip test and Chagas disease

BACKGROUND

The definitive diagnosis of visceral leishmaniasis (VL) requires invasive procedures with demonstration of amastigotes in tissue or promastigotes in culture. Unfortunately, these approaches require laboratory materials not available in poor countries where the disease is endemic. The correct diagnosis of VL is important, and made more difficult by the fact that several common tropical diseases such as malaria, disseminated tuberculosis, and enteric fever share the same clinical presentation. Serological tests have been developed to replace parasitological diagnosis in the field. A commercially available K39-based strip test for VL has been developed for this purpose. The endemic area of leishmaniasis in Brazil overlaps the endemic area of Chagas disease, a disease that can cause false-positive serological test results. The aim of this study was to evaluate the incidence of false-positive exams using a rapid test for VL in patients with Chagas disease.

METHODS

A rapid test based on the recombinant K39 antigen of Leishmania was used in: (1) 30 patients with confirmed Chagas disease, (2) 30 patients with a serological diagnosis of Chagas disease by ELISA, indirect immunofluorescence, indirect hemagglutination, and chemiluminescence, (3) 30 healthy patients from a non-endemic area as the control group, (4) 30 patients with confirmed VL, and (5) 20 patients with proved cutaneous leishmaniasis.

RESULTS

The sensitivity and specificity of the rapid strip test were 100% when compared with healthy volunteers and those with confirmed Chagas disease. One false-positive result occurred in the group with Chagas disease diagnosed by serological tests (specificity of 96%).

CONCLUSION

The rapid test based on recombinant K39 is a useful diagnostic assay, and a false-positive result rarely occurs in patients with a serological diagnosis of Chagas disease.

Transmission of tropical and geographically restricted infections during solid-organ transplantation

In recent years, the increasing number of donors from different regions of the world is providing a new challenge for the management and selection of suitable donors. This is a worldwide problem in most countries with transplantation programs, especially due to the increase in immigration and international travel. This paper elaborates recommendations regarding the selection criteria for donors from foreign countries who could potentially transmit tropical or geographically restricted infections to solid-organ transplant recipients. For this purpose, an extensive review of the medical literature focusing on viral, fungal, and parasitic infections that could be transmitted during transplantation from donors who have lived or traveled in countries where these infections are endemic has been performed, with special emphasis on tropical and imported infections. The review also includes cases described in the literature as well as risks of transmission during transplantation, microbiological tests available, and recommendations for each infection. A table listing different infectious agents with their geographic distributions and specific recommendations is included.

A multianalyte Dot-ELISA for simultaneous detection of malaria, Chagas disease, and syphilis-specific IgG antibodies

A multianalyte Dot-enzyme-linked immunosorbent assay (Dot-ELISA-Multi) with Trypanosoma cruzi epimastigote alkaline extract (EAE), trypomastigote excreted-secreted antigen (TESA), recombinant protein derived from 19-kDa C-terminal region of the Plasmodium vivax merozoite surface protein 1 (PvMSP1(19)), Plasmodium falciparum Zwittergent extract (Pf-Zw), and Treponema pallidum Zwittergent extract (Tp-Zw) was standardized and evaluated as a method for surveying IgG-specific antibodies in Chagas disease, malaria, and syphilis in a single test. The study was carried out on serum samples from 52 patients with chronic Chagas disease, 103 individuals with current (parasitemic) or past malaria (aparasitemic), 43 patients with syphilis, 21 individuals with heterologous antibodies, and 100 blood donors. Dot-ELISA-Multi yielded 99% specificity for Chagas disease and 100% for malaria and syphilis. The test sensitivity was 100% for chronic Chagas disease, 88% for syphilis, 90% for P. vivax, and 47% for P. falciparum. In past malaria individuals, positivity was 92%. Therefore, Dot-ELISA-Multi can be useful under field conditions where laboratory facilities and resources are scarce, for small-scale epidemiologic studies.

Field evaluation of four novel enzyme immunoassays for Chagas' disease in Venezuela blood banks: comparison of assays using fixed-epimastigotes, fixed-trypomastigotes or trypomastigote excreted?secreted antigens from two Trypanosoma cruzi strains

Many serological tests have been developed for the diagnosis of Chagas' disease, but few have been subjected to a rigorous field evaluation. We have recently described several novel enzyme immunoassays (EIAs) based on fixed-whole organisms or trypomastigote excretory-secretory antigens (TESA) from different Trypanosoma cruzi strains (Tulahuen or Brazil). This study evaluated the most promising of these novel assays (e.g. fixed-epimastigotes, fixed-trypomastigotes, TESA Brazil and TESA Tulahuen antigens) in a field study of Venezuelan blood bank specimens. The assays were tested in an operator-blinded fashion using 2038 blood bank samples obtained from low and high T.cruzi prevalence regions of Venezuela (n= 1050 and n= 988 from Bolivar and Portuguesa states, respectively). Based on National Laboratory for Chagas Immunodiagnosis (NLCI) 'gold standard' results, all novel EIAs were superior to the commercial kit currently used in Venezuela, achieving 100% sensitivity and >99% specificity at optimal cut-off values. The novel assays identified seven false-negative samples compared with the routine screening performed by the Venezuelan blood bank although two samples were also misclassified as positive. Minor differences in the performance of the four novel assays were observed at lower arbitrary cut-off values. This study confirms the potential utility of both the fixed-organism and the TESA-based assays in the diagnosis of T.cruzi infection.

Diagnostic performance of tests based on Trypanosoma cruzi excreted-secreted antigens in an endemic area for Chagas' disease in Bolivia

The diagnostic performance of Trypanosoma cruzi excreted-secreted antigen (TESA)-based and conventional tests for Chagas' disease was evaluated in a field study with 742 sera from a population in an endemic area in the Department of Chuquisaca, Bolivia. Of the 742 samples, 329 (44.34 %) were positive in the TESA blot assay, which diagnosed 9 Trypanosoma cruzi-infected individuals missed by conventional serologic tests.

Purified excreted-secreted antigens from Trypanosoma cruzi trypomastigotes as tools for diagnosis of Chagas' disease

There is currently no "gold standard" test for the diagnosis of late-stage Chagas' disease. As a result, protection of the blood supply in areas where Chagas' disease is endemic remains problematic. A panel of 709 serum samples from subjects with confirmed Chagas' disease (n = 195), healthy controls (n = 400), and patients with other parasitic diseases (n = 114) was used to assess enzyme-linked immunosorbent assays (ELISAs) based on a concentrated extract of excretory-secretory antigens from either Brazil or Tulahuen strain Trypanosoma cruzi trypomastigotes (total trypomastigote excretory-secretory antigens [TESAs]). The total TESA-based assays had excellent overall sensitivity (100%) and specificity (>94%), except for cross-reactivity with Leishmania-infected sera. In an attempt to increase the specificity of the assay, immunoaffinity chromatography was used to purify the TESA proteins (TESA(IA) proteins). By Western blotting, a series of polypeptide bands with molecular masses ranging from 60 to 220 kDa were recognized by pooled sera positive for Chagas' disease. An ELISA based on TESA(IA) proteins had a slightly lower sensitivity (98.6%) but an improved specificity (100%) compared to the sensitivity and specificity of the total TESA protein-based ELISAs. A 60-kDa polypeptide was identified as a major contributor to the cross-reactivity with Leishmania. These data suggest the need for field validation studies of TESA- and TESA(IA)-based assays in regions where Chagas' disease is endemic.

Otimização de ELISA empregando a proteína Tc85-11 e planejamento fatorial

A doença de Chagas é causada pelo Trypanosoma cruzi (T. cruzi) e a detecção de anticorpos anti-T. cruzi no soro é um método para diagnosticar a doença. Neste trabalho, ELISA indireto foi otimizado para a detecção de anticorpos no soro de pacientes com doença de Chagas empregando a proteína Tc85-11 (Ag) da superfície do parasita tripomastigota. Na otimização das condições experimentais foi aplicado planejamento fatorial completo para os parâmetros tempo de incubação, diluições do Ag (0,08 mg mL-1), anticorpo primário (Ac) e anti-IgG conjugada com a peroxidase (Ac*). Os melhores resultados foram obtidos nas seguintes condições: 0,14 mg Ag/poço, 60 min para o tempo de incubação, diluições de 1:35 e 1:1000 para Ac e Ac*, respectivamente. O valor do limiar de reatividade ("cut off") foi A450nm = 0,371. O ELISA indireto foi aplicado em amostras de soros de pacientes infectados com doença de Chagas e pacientes com diferentes doenças sistêmicas. A proteína Tc85-11, a qual está envolvida com a adesão do parasita na célula hospedeira, é também apropriada para o diagnóstico sorológico da doença de Chagas.

Neuroparasitic infections: cestodes, trematodes, and protozoans

Parasitic infection of the nervous system can produce a variety of symptoms and signs. Because symptoms of infection are often mild or nonspecific, diagnosis can be difficult. Familiarity with basic epidemiological characteristics and distinguishing radiographic findings can increase the likelihood of detection and proper treatment of parasitic infection of the nervous system. This article discusses the clinical presentation, diagnosis, and treatment for some of the more common infections of the nervous system caused by cestodes, trematodes and protozoans: Echinococcus spp., Spirometra spp. (sparganosis), Paragonimus spp., Schistosoma spp., Trypanosoma spp., Naegleria fowlerii, Acanthamoeba histolytica, and Balamuthia mandrillaris.

Immunosensor for the diagnosis of Chagas’ disease

Trypanosoma cruzi proteins from epimastigote membranes, herein referred as antigens, have been used for the construction of an amperometric immunosensor for serological diagnosis of Chagas' disease. The proteins used had a molecular mass ranging from 30 to 100 kDa. The gold electrode was treated with cysteamine and glutaraldehyde prior to antigen immobilization. Antibodies present in the serum of patients with Chagas' disease were captured by the immobilized antigens and the affinity interaction was monitored by chronoamperometry at a potential of -400 mV (versus Ag pseudo-reference electrode) using peroxidase-labeled IgG conjugate and hydrogen peroxide, iodide substrate. The incubation time to allow maximum antigen-antibody and antibody-peroxidase-labeled IgG interactions was 20 min with a reactivity threshold at -0.104 microA.

Immunoblotting analyses using two-dimensional gel electrophoresis of Trypanosoma cruzi excreted-secreted antigens

Trypanosoma cruzi trypomastigotes excrete-secrete a complex mixture of antigenic molecules. This antigenic mixture denominated trypomastigote excreted-secreted antigens contains a 150-160 kDa band that shows excellent performance in Chagas' disease diagnosis by immunoblotting. The present study partially characterized by two-dimensional gel electrophoresis the immunoreactivity against the 150-160 kDa protein using sera samples from chagasic patients in different phases of the disease. Trypomastigote excreted-secreted antigen preparations were subjected to high-resolution two-dimensional (2D) gel electrophoresis followed by immunoblotting with sera from chagasic and non-chagasic patients. The 150-160 kDa protein presented four isoforms with isoelectric focusing ranging from 6.2 to 6.7. The four isoforms were recognized by IgM from acute phase and IgG from chronic phase sera of chagasic patients. The 150-160 kDa isoform with IF of approximately 6.4 became the immunodominant spot with the progression of the disease. No cross-reactivity was observed with non-chagasic or patients infected with Leishmania sp. In this study we provide basic knowledge that supports the validation of trypomastigote excreted-secreted antigens for serological diagnosis of Chagas' disease.

Combined use of enzyme-linked immunosorbent assay and flow cytometry to detect antibodies to Trypanosoma cruzi in domestic canines in Texas

Canines may be sentinels and/or reservoirs for human Trypanosoma cruzi exposures. This study adapted a method originally designed for human diagnostics to detect serum immunoglobulin G to T. cruzi in canines. The method combined an enzyme-linked immunosorbent assay (ELISA) for screening and flow cytometry detection of anti-live trypomastigote antibodies (ALTA) for confirmation. The assays were optimized by using known positive and negative control canine sera, and cutoff values were established. The ELISA and ALTA assay easily distinguished between reactive (positive controls) and nonreactive (negative controls) sera and were used to test sera collected in a cross-sectional seroprevalence survey of 356 domestic canines from Harris County, Tex., and the surrounding area. Fifty-three (14.9%) of 356 asymptomatic canines in the survey were positive by ELISA, and 5 (1.4%) were confirmed positive with the ALTA assay, with an additional 4 (1.1%) canines classified as "suspect positive." Thus, the overall prevalence of T. cruzi antibodies in this population was 2.6%. This is the first U.S. study to use the combination of ELISA and ALTA to detect serum antibodies to T. cruzi and the first report of the prevalence of T. cruzi infection in domestic canines in the Houston, Tex. (Harris County), region. Our results demonstrate that the combination of ELISA and ALTA has been successfully adapted for use in testing canines for serological evidence of T. cruzi infection. Seroprevalence survey results suggest that T. cruzi antibody-positive domestic canines in the peridomestic setting are present in the Houston, Tex., region and further suggest that T. cruzi is enzootic in the region.

Serodiagnosis of chronic and acute Chagas' disease with Trypanosoma cruzi recombinant proteins: results of a collaborative study in six Latin American countries

An enzyme-linked immunosorbent assay to diagnose Chagas' disease by a serological test was performed with Trypanosoma cruzi recombinant antigens (JL8, MAP, and TcPo). High sensitivity (99.4%) and specificity (99.3%) were obtained when JL8 was combined with MAP (JM) and tested with 150 serum samples from chagasic and 142 nonchagasic individuals. Moreover, JM also diagnosed 84.2% of patients in the acute phase of T. cruzi infection.

Use of the Trypanosoma cruzi recombinant complement regulatory protein to evaluate therapeutic efficacy following treatment of chronic chagasic patients

One of the greatest concerns in Chagas' disease is the absence of reliable methods for the evaluation of chemotherapy efficacy in treated patients. The tests available to evaluate cure after the specific treatment are the complement-mediated lysis (CoML) and flow cytometry tests, but they are not feasible for routine clinical use. In this study, we evaluated an enzyme-linked immunosorbent assay (ELISA) based on the recombinant Trypanosoma cruzi complement regulatory protein (rCRP) as a method to determine parasite clearance in comparison to the CoML and other methods such as conventional serology, hemoculture, and PCR in serum samples of 31 patients collected before and after the treatment, monitored for an average of 27.7 months after chemotherapy. The results showed that the percentage of patient samples that were positive by rCRP ELISA was reduced from 100 to 70.3, 62.5, 71.4, and 33.4% in the first, second, third, and fourth years after treatment, respectively, while the samples positive by CoML were reduced to 85.2, 81.2, 71.4, and 33.4% during the same period, demonstrating the same significant tendency in the reduction of positive samples. On the other hand, the conventional serology (CS) tests did not present this reduction. The percentage of samples positive by PCR was initially 77.4% and decreased to 55.5, 68.7, 47.7, and 50.0% at the fourth year after treatment, confirming the drastic clearance of circulating parasites after treatment. Our results strongly suggest that the rCRP ELISA was capable of detecting the early therapeutic efficacy in treated patients and confirmed its superiority over the CS tests and parasitologic methods.

Trypanosoma cruzi: isolation of an immunodominant peptide of TESA (Trypomastigote Excreted-Secreted Antigens) by gene cloning

Trypomastigote forms of Trypanosoma cruzi excrete-secrete several molecules, which are immunodominant during the human infection. This complex antigenic mixture termed TESA (Trypomastigote Excreted-Secreted Antigens) presents a 150-160 kDa band that shows excellent specificity and sensitivity in Chagas' disease diagnosis by immunoblotting. Here we describe the isolation and the antigenic characterization of a recombinant peptide (TESA-1) containing a 10 kDa T. cruzi peptide that belongs to the 150-160 kDa TESA fraction. The clone was isolated by screening a T. cruzi genomic expression library with chagasic antibodies reactive to the 150-160 kDa band of TESA immunoblots. After expression, the recombinant peptide TESA-1 was purified and used to immunize rabbits. Anti-TESA-1 immunesera specifically recognized the 150-160 kDa fraction of TESA-blots from eight different T. cruzi strains. The TESA-1 peptide reacted with 82.2% of chagasic patient sera by immunoblotting, showing that it harbors most of the antigenic epitopes that account for the high reactivity of the 150-160 kDa band of TESA.

A critical review on Chagas disease chemotherapy

In this "Critical Review" we made a historical introduction of drugs assayed against Chagas disease beginning in 1912 with the works of Mayer and Rocha Lima up to the experimental use of nitrofurazone. In the beginning of the 70s, nifurtimox and benznidazole were introduced for clinical treatment, but results showed a great variability and there is still a controversy about their use for chronic cases. After the introduction of these nitroheterocycles only a few compounds were assayed in chagasic patients. The great advances in vector control in the South Cone countries, and the demonstration of parasite in chronic patients indicated the urgency to discuss the etiologic treatment during this phase, reinforcing the need to find drugs with more efficacy and less toxicity. We also review potential targets in the parasite and present a survey about new classes of synthetic and natural compounds studied after 1992/1993, with which we intend to give to the reader a general view about experimental studies in the area of the chemotherapy of Chagas disease, complementing the previous papers of Brener (1979) and De Castro (1993).