Metacyclogenesis as the Starting Point of Chagas Disease

Chagas disease is a neglected infectious disease caused by the protozoan Trypanosoma cruzi, primarily transmitted by triatomine vectors, and it threatens approximately seventy-five million people worldwide. This parasite undergoes a complex life cycle, transitioning between hosts and shifting from extracellular to intracellular stages. To ensure its survival in these diverse environments, T. cruzi undergoes extreme morphological and molecular changes. The metacyclic trypomastigote (MT) form, which arises from the metacyclogenesis (MTG) process in the triatomine hindgut, serves as a crucial link between the insect and human hosts and can be considered the starting point of Chagas disease. This review provides an overview of the current knowledge regarding the parasite's life cycle, molecular pathways, and mechanisms involved in metabolic and morphological adaptations during MTG, enabling the MT to evade the immune system and successfully infect human cells.

An Integrative Sialomic Analysis Reveals Molecules From Triatoma sordida (Hemiptera: Reduviidae)

Triatomines have evolved salivary glands that produce versatile molecules with various biological functions, including those leading their interactions with vertebrate hosts’ hemostatic and immunological systems. Here, using high-throughput transcriptomics and proteomics, we report the first sialome study on the synanthropic triatomine Triatoma sordida. As a result, 57,645,372 reads were assembled into 26,670 coding sequences (CDS). From these, a total of 16,683 were successfully annotated. The sialotranscriptomic profile shows Lipocalin as the most abundant protein family within putative secreted transcripts. Trialysins and Kazal-type protease inhibitors have high transcript levels followed by ubiquitous protein families and enzyme classes. Interestingly, abundant trialysin and Kazal-type members are highlighted in this triatomine sialotranscriptome. Furthermore, we identified 132 proteins in T. sordida salivary gland soluble extract through LC-MS/MS spectrometry. Lipocalins, Hemiptera specific families, CRISP/Antigen-5 and Kazal-type protein inhibitors proteins were identified. Our study provides a comprehensive description of the transcript and protein compositions of the salivary glands of T. sordida. It significantly enhances the information in the Triatominae sialome databanks reported so far, improving the understanding of the vector’s biology, the hematophagous behaviour, and the Triatominae subfamily’s evolution.

Enhanced IL-6 and IL-12B Gene Expression After SARS-CoV-2 Infection in Leprosy Patients May Increase the Risk of Neural Damage

Experts have called attention to the possible negative impact of the coronavirus disease 2019 (COVID-19)–related cytokine storm syndrome on the progression of leprosy-related disabilities. We assessed the frequency of reactional states in patients co-infected with Mycobacterium leprae and severe acute respiratory syndrome (SARS) coronavirus (CoV) 2 (SARS-CoV-2). We consecutively included patients during the first peak of the COVID-19 epidemic in Brazil and analyzed the expressions of genes encoding interleukin (IL)-1β, IL-6, IL-8, IL-10, IL-12A, IL-12B, and tumor necrosis factor-α in peripheral blood mononuclear cells. We included 64 leprosy patients and 50 controls. Twelve of the leprosy patients and 14 of the controls had been diagnosed with COVID-19. Co-infection was associated with increased IL-6 (P = 0.043) and IL-12B (P = 0.017) expression. The median disability grades were higher for leprosy/COVID-19 patients; however, the difference was not significant (P = 0.194). Patients co-infected with M. leprae and SARS-CoV-2 may experience a higher-grade proinflammatory state.

International collaboration in Brazilian science: financing and impact

The study of international collaborations can help in understanding the benefits of such relationships and aid in developing national financing policies. In this paper, the international collaboration of Brazilian scientists was studied using SciVal^® and Incites^® database, looking at its effect on the universities, financing agencies and different areas of knowledge and research topic clusters. Cluster and principal component analyses of scientometric data were carried out. While the results confirmed known knowledge that international collaboration increases impact, this study shows that Brazilian researchers are contributing to prominent research topics worldwide, in all areas of knowledge. This finding is contrary to several points of view that identify Brazil as a regional and not an international partner in science. Important also to note the impact of Brazilian authors in international collaboration that is well above the world mean. The collaboration of Brazil with foreign partners brings benefits for both sides, creating the opportunity of Brazilian research access to financing from international agencies. Increases in measures of impact are also seen for both sides. Foreign partners likewise benefit from higher impact factors in the same topic cluster, when collaborating with Brazilian partners. Publishing open access in high impact journals is fundamental for maintaining Brazilian science at the forefront.

Proteomic Mapping of Multifunctional Complexes Within Triatomine Saliva

Triatomines are hematophagous insects that transmit Trypanosoma cruzi, the etiological agent of Chagas disease. This neglected tropical disease represents a global health issue as it is spreading worldwide. The saliva of Triatominae contains miscellaneous proteins crucial for blood feeding acquisition, counteracting host's hemostasis while performing vasodilatory, anti-platelet and anti-coagulant activities, besides modulating inflammation and immune responses. Since a set of biological processes are mediated by protein complexes, here, the sialocomplexomes (salivary protein complexes) of five species of Triatominae were studied to explore the protein-protein interaction networks. Salivary multiprotein complexes from Triatoma infestans, Triatoma dimidiata, Dipetalogaster maxima, Rhodnius prolixus, and Rhodnius neglectus were investigated by Blue-Native- polyacrylamide gel electrophoresis coupled with liquid chromatography tandem mass spectrometry. More than 70 protein groups, uncovering the landscape of the Triatominae salivary interactome, were revealed. Triabin, actin, thioredoxin peroxidase and an uncharacterized protein were identified in sialocomplexes of the five species, while hexamerin, heat shock protein and histone were identified in sialocomplexes of four species. Salivary proteins related to triatomine immunity as well as those required during blood feeding process such as apyrases, antigen 5, procalins, and nitrophorins compose different complexes. Furthermore, unique proteins for each triatomine species were revealed. This study represents the first Triatominae sialocomplexome reference to date and shows that the approach used is a reliable tool for the analysis of Triatominae salivary proteins assembled into complexes.

In vitro investigation of Brazilian Cerrado plant extract activity against Plasmodium falciparum, Trypanosoma cruzi and T. brucei gambiense

The threatened Brazilian Cerrado biome is an important biodiversity hotspot but still few explored that constitutes a potential reservoir of molecules to treat infectious diseases. We selected eight Cerrado plant species for screening against the erythrocytic stages of Plasmodium falciparum, human intracellular stages of Trypanosoma cruzi and bloodstream forms of T. brucei gambiense, and for their cytotoxicity upon the rat L6-myoblast cell line. Bioassays were performed with 37 hexane, ethyl acetate and ethanol extracts prepared from different plant organs. Activities against parasites were observed for 24 extracts: 9 with anti-P. falciparum, 4 with anti-T. cruzi and 11 with anti-T. brucei gambiense activities. High anti-protozoal activity (IC50 values < 10 μg/mL) without obvious cytotoxicity to L6 cells was observed for eight extracts from plants: Connarus suberosus, Blepharocalyx salicifolius, Psidium laruotteanum and Myrsine guianensis. Overall, studies of plant extracts will contribute to increase the biodiversity knowledge essential for Cerrado conservation and sustainable development.

Parasite prolyl oligopeptidases and the challenge of designing chemotherapeuticals for Chagas disease, leishmaniasis and African trypanosomiasis

The trypanosomatids Trypanosoma cruzi, Leishmania spp. and Trypanosoma brucei spp. cause Chagas disease, leishmaniasis and human African trypanosomiasis, respectively. It is estimated that over 10 million people worldwide suffer from these neglected diseases, posing enormous social and economic problems in endemic areas. There are no vaccines to prevent these infections and chemotherapies are not adequate. This picture indicates that new chemotherapeutic agents must be developed to treat these illnesses. For this purpose, understanding the biology of the pathogenic trypanosomatid-host cell interface is fundamental for molecular and functional characterization of virulence factors that may be used as targets for the development of inhibitors to be used for effective chemotherapy. In this context, it is well known that proteases have crucial functions for both metabolism and infectivity of pathogens and are thus potential drug targets. In this regard, prolyl oligopeptidase and oligopeptidase B, both members of the S9 serine protease family, have been shown to play important roles in the interactions of pathogenic protozoa with their mammalian hosts and may thus be considered targets for drug design. This review aims to discuss structural and functional properties of these intriguing enzymes and their potential as targets for the development of drugs against Chagas disease, leishmaniasis and African trypanosomiasis.

Effects of an anticarcinogenic Bowman-Birk protease inhibitor on purified 20S proteasome and MCF-7 breast cancer cells

Proteasome inhibitors have been described as an important target for cancer therapy due to their potential to regulate the ubiquitin-proteasome system in the degradation pathway of cellular proteins. Here, we reported the effects of a Bowman-Birk-type protease inhibitor, the Black-eyed pea Trypsin/Chymotrypsin Inhibitor (BTCI), on proteasome 20S in MCF-7 breast cancer cells and on catalytic activity of the purified 20S proteasome from horse erythrocytes, as well as the structural analysis of the BTCI-20S proteasome complex. In vitro experiments and confocal microscopy showed that BTCI readily crosses the membrane of the breast cancer cells and co-localizes with the proteasome in cytoplasm and mainly in nucleus. Indeed, as indicated by dynamic light scattering, BTCI and 20S proteasome form a stable complex at temperatures up to 55°C and at neutral and alkaline pHs. In complexed form, BTCI strongly inhibits the proteolytic chymotrypsin-, trypsin- and caspase-like activities of 20S proteasome, indicated by inhibition constants of 10⁻⁷ M magnitude order. Besides other mechanisms, this feature can be associated with previously reported cytostatic and cytotoxic effects of BTCI in MCF-7 breast cancer cells by means of apoptosis.

The Trypanosoma cruzi virulence factor oligopeptidase B (OPBTc) assembles into an active and stable dimer

Oligopeptidase B, a processing enzyme of the prolyl oligopeptidase family, is considered as an important virulence factor in trypanosomiasis. Trypanosoma cruzi oligopeptidase B (OPBTc) is involved in host cell invasion by generating a Ca(2+)-agonist necessary for recruitment and fusion of host lysosomes at the site of parasite attachment. The underlying mechanism remains unknown and further structural and functional characterization of OPBTc may help clarify its physiological function and lead to the development of new therapeutic molecules to treat Chagas disease. In the present work, size exclusion chromatography and analytical ultracentrifugation experiments demonstrate that OPBTc is a dimer in solution, an association salt and pH-resistant and independent of intermolecular disulfide bonds. The enzyme retains its dimeric structure and is fully active up to 42°C. OPBTc is inactivated and its tertiary, but not secondary, structure is disrupted at higher temperatures, as monitored by circular dichroism and fluorescence spectroscopy. It has a highly stable secondary structure over a broad range of pH, undergoes subtle tertiary structure changes at low pH and is less stable under moderate ionic strength conditions. These results bring new insights into the structural properties of OPBTc, contributing to future studies on the rational design of OPBTc inhibitors as a promising strategy for Chagas disease chemotherapy.

[Severe hydroureteronephrosis associated to asymptomatic giant anterior sacral meningocele: a case report and review of the literature]

We present the case of a woman with Marfan's syndrome presenting with a clinical picture of acute gastroenteritis in whom severe bilateral hydroureteronephrosis associated to a neurogenic bladder and a giant anterior sacral meningocele was diagnosed incidentally. The importance of this case lies in the fact that the patient was asymptomatic despite the significant visceral repercussions already occurring that led to questioning of whether MRI follow-up would still be advisable even in the absence of symptoms.

The diagnostic usefulness of AUDIT and AUDIT-C for detecting hazardous drinkers in the elderly

We compare the diagnostic usefulness of the Alcohol Use Disorders Identification Test (AUDIT) and the AUDIT alcohol consumption questions (AUDIT-C) for detecting hazardous drinkers between the populations over and less than 65 years in primary care settings. To assess weekly alcohol intake an interview on quantity-frequency was administered to 602 patients. Hazardous drinking was defined as a level of consumption of 280 g of alcohol per week for men and 168 g for women. The participants received AUDIT, AUDIT-C and CAGE questionnaires. Gamma-glutamyltransferase (GGT), mean corpuscular volume (MCV), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) values were also determined. Average weekly alcohol intake among the population aged 65 and older was 83 g, and 10% were hazardous drinkers. In this age group, the sensitivities of AUDIT and AUDIT-C for detecting this type of drinkers were 67% and 100%, whereas specificities were 95% and 81% respectively. In the younger patient group, the sensitivities were 84% and 100% and the specificities 95% and 79% respectively. In conclusion, both AUDIT and AUDIT-C perform well at detecting hazardous drinkers in the group older than 65 years and that their sensitivities and specificities are comparable to those in younger ages.

Lagochilascaris minor third-stage larvae secrete metalloproteases with specificity for fibrinogen and native collagen

Dissemination of parasitic infections depends on migration through tissues and evasion from both hemostatic processes and immune responses from hosts. Metalloproteases play major roles in these mechanisms of pathogen-host interactions and, thus, are considered drug targets. In this study, we characterized metalloprotease activities in excretory/secretory (ES) products from third stage larvae (L3) of the ascarid Lagochilascaris minor, the causative agent of lagochilascariosis, which demonstrates an impressive migrating capacity across host tissues, including bone. Gel enzymography showed that ES products of L3 display two major gelatinolytic activities. Optimal proteolytic activity was found to occur at neutral/alkaline pH and was associated with two L. minor-secreted metalloproteases of 59 (SM59(Lm)) and 114kDa (SM114(Lm)). We next showed that ES products of L3 were able to hydrolyze fibrinogen and collagen I at neutral pH, but not BSA, in an extensive manner. Furthermore, we demonstrated that ES products of L3 mediate hydrolysis of the triple helical structure of collagen I fibers in mouse mesentery. These results suggest that ES proteases of L3 might facilitate both L. minor migration through host tissues by hydrolyzing collagens of the extracellular matrix and evasion from host hemostatic mechanisms by degrading fibrinogen.

Diagnostic usefulness of brief versions of Alcohol Use Disorders Identification Test (AUDIT) for detecting hazardous drinkers in primary care settings

OBJECTIVE

The aim of this study was to evaluate the diagnostic usefulness of the brief versions of the Alcohol Use Disorders Identification Test (AUDIT) for detecting hazardous drinkers and to compare it with that of the full-AUDIT in primary care settings.

METHOD

Five hundred patients were randomly selected in a primary care center. An interview on quantity-frequency was administered for assessment of weekly alcohol intake. The standard used for classification of hazardous drinkers was a weekly alcohol consumption of 280 g for men and 168 g for women. Cut-off points were 8 for the full-AUDIT, 1 for the AUDIT-3 (third item), 3 for the AUDIT-C (items 1, 2 and 3), 5 for the AUDIT-PC (items 1, 2, 4, 5 and 10) and 3 for the modified Fast Alcohol Screening Test (m-FAST; items 3, 5, 8 and 10). Sensitivity, specificity, positive and negative predictive values, and areas under the receiver operating characteristic (AUROC) curves were measured.

RESULTS

Diagnostic usefulness of the questionnaires for detecting hazardous drinkers was for the full-

AUDIT

81.4% sensitivity, 94.6% specificity and 0.97 AUROC curve; for the AUDIT-3: 83.1% sensitivity, 90.9% specificity and 0.89 AUROC curve; for the AUDIT-C: 100% sensitivity, 79.4% specificity and 0.97 AUROC curve; for the AUDIT-PC: 98.3% sensitivity 90.9% specificity and 0.97 AUROC curve; and for the m-FAST: 79.7% sensitivity, 93.7% specificity and 0.93 AUROC curve.

CONCLUSIONS

The AUDIT-C and AUDIT-PC show a higher sensitivity, lower specificity and a similar AUROC curve than the full-AUDIT, thus allowing their use as screening instruments that are as reliable as the original test for detecting hazardous drinkers. The AUDIT-3 and m-FAST, when compared with the full-AUDIT, performed less well, therefore limiting their use for this purpose.

Trypanocidal activity of a new diterpene from Casearia sylvestris var. lingua

Bioassay-guided fractionation of the hexanic root bark extract of Casearia sylvestris var. lingua led to the isolation of a new clerodane diterpene, whose structure was elucidated as rel-(2 S,5 R,6 R,8 S,9 S,10 R,18 S,19 R)-19-acetoxy-18,19-epoxy-6-hydroxy-18-butanoyloxy-2-(2-methylbutanoyloxy)cleroda-3,13(16), 14-triene by spectroscopic means, including 1D and 2D NMR analyses. This compound showed pronounced activity on Trypanosoma cruzi, the casual agent of Chagas' disease, with minimal inhibitory concentration (MIC) at 0.59 microg/mL.

Trypanosoma cruzi prolyl oligopeptidase Tc80 is involved in nonphagocytic mammalian cell invasion by trypomastigotes

Trypanosoma cruzi is an intracellular protozoan parasite able to invade a wide variety of mammalian cells. To have access to the target organs/cells, the parasite must cross the basal laminae and the extracellular matrix (ECM). We previously characterized an 80-kDa proteinase (Tc80) secreted by the infective trypomastigotes that hydrolyzes native collagens and might be involved in infection by degrading ECM components. Here, we present evidence indicating a role for Tc80 in the invasion of nonphagocytic cells. Tc80 was classified as a member of the prolyl oligopeptidase (POP) family of serine proteases and was also found to hydrolyze fibronectin. Selective inhibitors for POP Tc80 were synthesized that blocked parasite entry into cells. Blockage occurred when trypomastigotes were preincubated with irreversible inhibitors but not after host cell preincubation, and the blockage correlated with inhibition of POP Tc80 activity in treated parasites. These data and the enzyme location inside a vesicular compartment close to the flagellar pocket, a specialized domain in endocytosis/exocytosis, strongly suggest a role for POP Tc80 in the maturation of parasite protein(s) and/or, after secretion, in a local action on parasite or host cell/ECM components required for invasion.

Human IgG1 and IgG4: the main antibodies against Triatoma infestans (Hemiptera: Reduviidae) salivary gland proteins

The Triatoma infestans salivary gland proteins (TSGP) can induce local and systemic hypersensitivity reactions in humans. IgG antibodies against TSGP were present in higher levels in sera of Chagas disease patients, and in individuals living in triatomine-infested areas than in controls living in triatomine-free areas. TSGP-specific IgG1 was found in sera of Chagas patients, and of individuals living in triatomine-infested rural areas, and uniquely specific IgG4 was present in sera of Chagas patients living in triatomine-infested areas, reactive against TSGP. Unique specificities were not detected in sera of individuals reacting against the ubiquitous mosquito Culex quinquifasciatus saliva proteins (CSGP). In conclusion, IgG1 reactive against TSGP is the main antibody present in individuals living in the triatomine-infested study areas. Also, IgG4 is found in the sera of insect-transmitted Chagas disease patients living in study areas.

Diagnostic usefulness of carbohydrate-deficient transferrin for detecting alcohol-related problems in hospitalized patients

We evaluated the diagnostic usefulness of carbohydrate-deficient transferrin (CDT) for detecting alcohol-related problems (ARP) in hospitalized patients, assessed potential differences according to gender and age, and compared this value to the other screening measures conventionally used, namely the CAGE questionnaire and standard biological markers MCV (mean corpuscular volume) and GGT (gamma-glutamyltransferase). CDT sensitivity for detecting ARP was 70%, specificity 75% and area under the receiver operating characteristic curve 0.76%. Its sensitivity was shown to be lower both in the female group (65 vs 71%) as well as in the younger-age group whereas its specificity was lower in the liver-damaged group (55%). CDT diagnostic value did not exceed that of CAGE (sensitivity 78% and specificity 99%), MCV (sensitivity and specificity 74%) or GGT (sensitivity 82% and specificity 53%) but was better than those of other biochemical measures. We conclude that CDT is an effective biological marker for the detection of ARP among hospitalized patients, but that its diagnostic usefulness does not exceed that of some other alternative measures commonly used.

Current millennium biotechniques for biomedical research on parasites and host-parasite interactions

The development of biotechnology in the last three decades has generated the feeling that the newest scientific achievements will deliver high standard quality of life through abundance of food and means for successfully combating diseases. Where the new biotechnologies give access to genetic information, there is a common belief that physiological and pathological processes result from subtle modifications of gene expression. Trustfully, modern genetics has produced genetic maps, physical maps and complete nucleotide sequences from 141 viruses, 51 organelles, two eubacteria, one archeon and one eukaryote (Saccharomices cerevisiae). In addition, during the Centennial Commemoration of the Oswaldo Cruz Institute the nearly complete human genome map was proudly announced, whereas the latest Brazilian key stone contribution to science was the publication of the Shillela fastidiosa genomic sequence highlythed on a Nature cover issue. There exists a belief among the populace that further scientific accomplishments will rapidly lead to new drugs and methodological approaches to cure genetic diseases and other incurable ailments. Yet, much evidence has been accumulated, showing that a large information gap exists between the knowledge of genome sequence and our knowledge of genome function. Now that many genome maps are available, people wish to know what are we going to do with them. Certainly, all these scientific accomplishments will shed light on many more secrets of life. Nevertheless, parsimony in the weekly announcements of promising scientific achievements is necessary. We also need many more creative experimental biologists to discover new, as yet un-envisaged biotechnological approaches, and the basic resource needed for carrying out mile stone research necessary for leading us to that "promised land" often proclaimed by the mass media.

Solubilization of delipidated macrophage membrane proteins for analysis by two-dimensional electrophoresis

Two-dimensional electrophoresis of proteins is often precluded due to the lack of solubilization of cell membrane extracts in an aqueous medium. Various additives and detergents have been used to circumvent the problem, but their efficacy may not be satisfactory. In this study, the removal of lipidic components of the cell membrane extract with chloroform-methanol was used to achieve solubilization. Optimal delipidation was obtained with acetone washings. This procedure increased solubilization of membrane proteins from a murine macrophage cell line, thus showing a substantial improvement in gel resolution. The two-dimensional gels loaded with delipidated extract proved to be free of smearing and horizontal streaking. In addition, other protein spots were revealed that were not detected in the gels loaded with undelipidated cell membrane extract.

Chemotherapy of an experimental Trypanosoma cruzi infection with specific immunoglobulin-chlorambucil conjugate

Hybrid molecules were constructed with either polyclonal antibodies against Trypanosoma cruzi antigens or monoclonal antibody against Trypanosoma brucei brucei low-density lipoprotein (LDL)-receptor conjugated with chlorambucil. Physical-chemical analysis of the hybrid molecule showed four chlorambucil coupling sites in each IgG and a binding constant in the order of 10(4). Maintenance of IgG integrity was indicated by its circular dichroism pattern. Biologic activity of the hybrid molecule was shown by its inhibitory effect on the mobility and proliferation of the parasite. An IgG-chlorambucil conjugate, produced with monoclonal antibody anti-T. b. brucei LDL-receptor, led to the immobilization of the T. cruzi forms, albeit at a much lesser level than that obtained with a mouse polyclonal anti-T. cruzi IgG linked to the drug. Targeting experimental T. cruzi infection with a specific IgG-chlorambucil conjugate resulted in consistent reduction of parasitemia and mortality, thus showing its potential usefulness in controlling the acute form of the disease.

Characterisation of a Trypanosoma cruzi acidic 30 kDa cysteine protease

A novel proteolytic activity was identified in epimastigote, amastigote and trypomastigote forms of Trypanosoma cruzi using the fluorogenic substrate N-Succinyl-Leu-Leu-Val-Tyr-7-amido-4-methylcoumarin. Epimastigotes showed enzyme activity to be 2-fold higher than amastigotes and trypomastigotes. The protease that displays this activity was purified from epimastigote forms by a four step chromatographic procedure: Diethylaminoethyl-Sephacel, Phenyl-Sepharose, Phenyl-Superose, and Concanavalin A Sepharose columns. The purified enzyme is a glycoprotein that migrates as a 30 kDa protein in 12.5% SDS-polyacrylamide gel electrophoresis (PAGE), under reducing conditions. Its optimal enzymatic activity on both fluorogenic and protein substrates was found to occur at an acidic pH. The inhibition pattern of the purified 30 kDa protease showed that it belongs to the cysteine-protease class. In addition to the synthetic substrate, the purified protease hydrolysed bovine serum albumin (BSA) and human type I collagen. The N-terminal amino acid sequence of the protease shows similarity to the mammalian cathepsin B protease.

A Trypanosoma cruzi-secreted 80 kDa proteinase with specificity for human collagen types I and IV

Specific interactions between parasites and extracellular matrix components are an important mechanism in the dissemination of Chagas' disease. Binding of the extracellular matrix proteins to Trypanosoma cruzi receptors has been described as a significant step in this phenomenon. In this study, a specific proteinase activity was identified in cell-free extracts of amastigote, trypomastigote and epimastigote forms of T. cruzi using the collagenase fluorogenic substrate N-Suc-Gly-Pro-Leu-Gly-Pro-7-amido-4-methylcoumarin. Isolation of this activity was achieved by a four-step FPLC procedure. Optimal enzyme activity was found to occur at pH 8.0 and was associated with a single T. cruzi 80 kDa protein (Tc 80 proteinase) on SDS/PAGE under reducing conditions. An internal peptide sequence of Tc 80 proteinase was obtained (AGDNYTPPE), and no similarity was found to previously described proteinases of T. cruzi. This enzyme activity is strongly inhibited by HgCl2, tosyl-lysylchloromethane ('TLCK') p-chloromercuribenzoate and benzyloxycarbonyl-Phe-Ala-diazomethane. The purified enzyme was able to hydrolyse purified human [14C]collagen types I and IV at neutral pH, but not 14C-labelled BSA, rat laminin, rabbit IgG or small proteins such as insulin or cytochrome c. In addition, Tc 80 proteinase activity was found to be secreted by T. cruzi forms infective to mammalian cells. Furthermore we demonstrated that purified Tc 80 proteinase mediates native collagen type I hydrolysis in rat mesentery. This feature is compared with that of Clostridium histolyticum collagenase. These findings suggest that Tc 80 proteinase may facilitate T. cruzi host-cell infection by degrading the collagens of the extracellular matrix and could represent a good target for Chagas' disease chemotherapy.

Diversity of Trypanosoma cruzi stocks and clones derived from Chagas disease patients: I--Behavioral characterization in vitro

In this study, we isolated Trypanosoma cruzi from chronic Chagas heart disease and from megaesophagus patients. The parasite stock hSLU239 (heart disease) yielded clones h1 and h2, whereas stock mSEU142 (megaesophagus) yielded clones m1, m2, m3 and m4. The parasite growth kinetics, doubling time and differentiation in axenic liquid medium showed broad behavioral diversity. It was shown that a particular pattern of behavior for a parental stock could not necessarily be assigned for subsequent clones. This study indicates that i) each Chagas disease patient is infected with several T. cruzi populations; ii) clonal lines derived from patient samples may have different biological characteristics from the original isolate; and that iii) additional behavioral and/or molecular markers are required for further characterization of Trypanosoma cruzi stocks and clones derived from Chagas disease patients in order to identify correlations with pathology.

Cross-reactivity of antibodies in human infections by the kinetoplastid protozoa Trypanosoma cruzi, Leishmania chagasi and Leishmania (viannia) braziliensis

We have detected antibodies, in the sera of Chagas disease, Kala-azar and Mucocutaneous leishmaniasis patients, that bind multiple antigens shared between the three causative agents. The Chagas disease sera showed 98 to 100% positive results by ELISA when the Leishmania braziliensis and Leishmania chagasi antigens were used, respectively. The Kala-azar sera showed 100% positive results with Trypanosoma cruzi or L. braziliensis antigens by immunofluorescence assays. The antibodies in the sera of Mucocutaneous leishmaniasis patients showed 100% positive results by ELISA assays with T. cruzi or L. chagasi antigens. Furthermore, the direct agglutination of L. chagasi promastigotes showed that 95% of Kala-azar and 35% of Mucocutaneous leishmaniasis sera agglutinated the parasite in dilutions above 1:512. In contrast, 15% of Chagas sera agglutinated the parasite in dilutions 1:16 and below. Western blot analysis showed that the Chagas sera that formed at least 24 bands with the T. cruzi also formed 13 bands with the L. chagasi and 17 bands with the L. braziliensis. The Kala-azar sera that recognized at least 29 bands with the homologous antigen also formed 14 bands with the T. cruzi and 10 bands with the L. braziliensis antigens. Finally, the Mucocutaneous leishmaniasis sera that formed at least 17 bands with the homologous antigen also formed 10 bands with the T. cruzi and four bands with the L. chagasi antigens. These results indicate the presence of common antigenic determinants in several protozoal proteins and, therefore, explain the serologic cross-reactions reported here.

[The use of 4 immunological exams for the determination of Chagas disease prevalence in streetsweepers of the City Sanitation Service in the Federal District]

Seropositivity for Trypanosoma cruzi infection was studied in 368 street-sweepers of the SLU, Federal District, Brazil, with the aid of haemaglutination, immunofluorescence and, also, a delayed-type skin test to the parasite T12E antigen. It showed 32.1%, 42.1% and 38.6% positive results, respectively for each assay. Among these, however, only 47% were positive with each of three exams performed. In addition, 19.7% were positive with two out of three exams performed. The remaining 33.3% sera yielded one positive result out of three exams employed and were submitted to the immunoblot assay. This analysis confirmed 3 cases (37.5%) positive by hemmaglutination, 3 (11.5%) positive by skin test, and 1 (3.7%) positive by immunofluorescence. At the end of the analysis, it was shown that 129 (35%) individuals yielded at least two positive assays and, therefore, they should be considered as T. cruzi-infected individuals.

Possible integration of Trypanosoma cruzi kDNA minicircles into the host cell genome by infection

Infection with Trypanosoma cruzi is known to induce the division of peritoneal macrophages in BALB/c mice. We have demonstrated, by cytogenetic analysis, that accessory DNA elements are associated with the metaphase macrophage chromosomes of such infected macrophages. The identification of these accessory DNA elements with T. cruzi DNA is strongly supported by the association of 3H-label with some chromatids in macrophages previously infected with T. cruzi which had been labelled with 3H-methyl-thymidine. The karyotyping consistently showed preferential associations of T. cruzi DNA with chromosomes 3, 6 and 11. A conclusive demonstration of the parasite origin of the integrated DNA came from fluorescein in situ hybridization studies using specific parasite DNAs as probes. In order to determine the identity of the inserted DNA and to investigate the nature of the integration mechanism, Southern blot analyses were performed on DNA extracted from both uninfected and infected (but parasite-free) macrophages. Hybridizations of BamHI, EcoRI and TaqI digests of DNA from T. cruzi-infected host cells all revealed the presence of a 1.7-kb DNA fragment when probed with kDNA. The covalent association of kDNA with that of the host was confirmed by the fact that AluI and Hinf-I digests of DNA from infected host cells produced a number of bands, in a size range of 0.8-3.6 kb, which hybridized with kDNA minicircles. None of these bands was found in DNA purified from cell-free preparations of the parasite and thus it must be concluded that they represent insertion fragments between parasite and host cell DNA. These results strongly suggest that kDNA minicircles from T. cruzi have been integrated into the genome of the host cell following infection.

Purification and characterization of a new 120 kDa alkaline proteinase of Trypanosoma cruzi

A new alkaline proteinase activity was identified in cell-free extracts of Trypanosoma cruzi epimastigotes on the basis of its ability to hydrolyze the fluorogenic substrate N-Z-Gly-Gly-Arg-AMC. The optimal activity was at pH 8.0. After a three step-chromatography procedure using two anionic columns (DEAE-Sepharose and Mono Q) and a chromatofocusing column (Mono P), the proteolytic activity was associated with a single 120 kDa protein and was called Tc 120 proteinase. The molecular mass of the proteinase was confirmed by direct visualization of the proteolytic activity using a fluorometric assay on SDS-PAGE. The Tc 120 proteinase which also cleaves N-Z-Arg-AMC, N-Z-Phe-Arg-AMC and N-glutaryl-Gly-Arg-AMC substrates, is a cysteine-type proteinase with an unusual low sensitivity to E-64.

[Insertion of Trypanosoma cruzi DNA in the genome of mammal host cell through infection]

Trypanosoma cruzi chromatin was observed in macrophage chromosome spreads obtained at different periods of infections in BALB/c mice. Immunofluorescent studies showed that genetic materials associated with the chromosomes were T. cruzi products. In situ hybridization showed the protozoon DNA insertion in the host cell genome. In addition, selective 3H-DNA insertion in chromosomes 3, 6 and 11 was observed, which suggested that transxenogene rearrangement may take place in T. cruzi infections of mammals.

Chagas' disease. Immunotoxin inhibition of Trypanosoma cruzi release from infected host cells in vitro

Virulent tissue culture-derived Trypanosoma cruzi trypomastigotes were readily killed by immune IgG-ricin A chain conjugates (ITR) in vitro. Forty micrograms of ITR immobilized 10(6) trypomastigotes after 48 hours of incubation at 37 degrees C. ITR showed antibody specificity and 125I-labeled anti-T. cruzi IgG bound to parasitized host cells 9-fold more than to nonparasitized host cells. The degree of specificity was evaluated further in experiments in which 10 micrograms of ITR showed 78% inhibition of [3H]thymidine incorporation by T. cruzi. In contrast, nonimmune IgG-ricin A chain conjugate neither immobilized nor inhibited [3H]thymidine incorporation by the parasite. Furthermore, 20 micrograms of ITR significantly inhibited T. cruzi trypomastigote release from infected host cells and thus prevented reinfection of other cells in vitro.

Malignant, non-Hodgkin's lymphomas in Trypanosoma cruzi-infected rabbits treated with nitroarenes

Use of 2-nitroimidazole, 5-nitrofuran and 5-nitroimidazole compounds in T. cruzi-infected rabbits resulted in a reduction in duration of parasitaemia in comparison with untreated, infected rabbits. The chronic myocarditis associated with Chagas' disease was not, however, prevented in nitroarene-treated rabbits; lymphocytic infiltrates associated with cardiac cell lysis, in the absence of parasites in situ, were present in both treated and untreated rabbits. The carcinogenic effect of each trypanocidal nitroarene used in this study was also assessed. Administration of nitroarenes to rabbits resulted in the appearance of solid tumours in 37.8 per cent of animals that received drug therapy. Untreated, control rabbits in this series did not show tumour growth. Furthermore, malignant, mixed-cell type, non-Hodgkin's lymphomas were seen in 32.4 per cent of the treated rabbits. It seems that a direct relationship could be present between the presence of the nitro group, the trypanocidal cytotoxicity and the prevalence of tumours. Benznidazole cleared up parasitaemias in the shortest time and was associated with 41.6 per cent of lymphoma growths, whereas MK-436 required twice as much time to clear blood parasites, and showed lymphomas in 25 per cent of experimental rabbits. The demonstration of a high prevalence of malignant tumours in addition to the chronic myocarditis of Chagas' disease in nitroarene-treated rabbits is important since indiscriminate use of such compounds currently used to treat T. cruzi infections in man could increase the risk of lymphoma.

Effect of immunotoxins against Trypanosoma cruzi

Immunotoxins were constructed with IgG antibodies against Trypanosoma cruzi surface antigens by hybridization with abrin (ITA) and ricin (ITR) A chains. The biological activity of the hybrid macromolecules was tested on the parasite forms. Motility of parasite forms was lost in vitro after incubation with ITR. In general, killing of the parasite with ITR was more efficient than with ITA. Inhibition of protein synthesis after incubation with either ITR or ITA, measured by 3H-leucine incorporation, confirmed the parasite immobilization experiments. The lethal effect was potentiated when the immunotoxins were used in the presence of 2.5 mM ammonium chloride. T. cruzi antibodies specific to cell surface antigens are excellent drug carriers that can be delivered to the target cell. However, ITR and ITA did not reduce parasitemia or increase survival of mice infected with T. cruzi.

Trypanosoma cruzi: endocytosis and degradation of specific antibodies by parasite forms

Specific human IgG antibodies bound to a Trypanosoma cruzi envelope were internalized by antigen receptor-mediated endocytosis. Ferritin conjugated antibodies and horseradish peroxidase (HRP) conjugated IgG were found inside parasite cytoplasmic vesicles. Nonspecific IgG that did not bind to the external membrane was not internalized by the parasite. The ratio of 3H-protein A labeled: specific IgG internalization by parasites in the exponential growth phase (95% epimastigotes) was much smaller than that of parasites in the late stationary growth phase (38% trypomastigotes). Antibodies bound to the latter parasite forms almost disappeared from their outer membranes after 12 hr incubation at 27 degrees C. Results of experiments in which membrane bound antibodies were removed by an excess of pronase showed that only small amounts of radiolabeled IgG were found inside the parasites. The fate of immunoglobulins that vanished from external membrane receptors and did not accumulate inside the cells was explained by experiments in which the supernatants of IgG-3H-protein A labeled parasites were precipitated with trichloroacetic acid (TCA). In these, membrane-bound antibodies were taken in and degraded by the parasites as increased amounts of free radiolabel appeared in the supernatants as functions of incubation time and parasite stage.