Cross-reactivity of Vector-borne Metacyclic Forms of Trypanosoma cruzi with Mammalian and Culture Stages1

Metacyclic forms of Trypanosoma cruzi isolated from the hindgut of infected insect vectors (Rhodnius prolixus) were found to be immunologically cross-reactive with cultured epimastigote, amastigote, and metacyclic stages of the parasite as well as with bloodstream trypomastigote forms by direct agglutination and indirect immunofluorescence techniques. Sera specific for each of these forms of the parasite systematically yielded maximal antibody titers when measured against the homologous antigen, indicating that antigenic determinants are shared by all of the developmental forms used in this work. Supporting this conclusion were the significant reductions in anti-insect-derived metacyclic antibody titer caused by absorption with any of the other life stages of T. cruzi. These results are relevant to the potential use of laboratory-grown forms of T. cruzi in vaccination against a natural infection with this parasite.     

Survival of Trypanosoma cruzi metacyclic trypomastigotes within Coxiella burnetii vacuoles: differentiation and replication within an acidic milieu

Coxiella burnetii, the etiological agent of Q fever, is an obligate intracellular bacterium that resides within acidified vacuoles with secondary lysosomal characteristics. Infective stages of Trypanosoma cruzi, the causative agent of Chagas' disease, actively invade a wide variety of cells, a process followed by lysosomal recruitment. Recently, we have investigated and characterized early events that occur in Vero cells persistently colonized with C. burnetii when doubly infected with T. cruzi trypomastigote forms. Kinetic studies of trypomastigote transfer indicated that parasitophorous vacuoles (PV) of metacyclic trypomastigotes are rapidly and efficiently fused to C. burnetii vacuoles. Based on these observations we have investigated the behavior of metacyclic trypomastigotes within C. burnetii vacuoles beyond 12 h of co-infection inside Vero cells. Using indirect immunofluorescence with MAb against different developmental stages, it was possible to follow the T. cruzi differentiation process within C. burnetii vacuoles after up to 96 h post-invasion. We observed that metacyclic trypomastigotes began to differentiate after 12 h of infection, and 24 h later amastigotes were the prevailing forms within C. burnetii vacuoles. T. cruzi amastigote replication within C. burnetii vacuoles was confirmed using video and time-lapse confocal microscopy and around 36 h of co-infection, cytokinesis took about 70 min to occur. After 72 h, we observed that amastigote forms seemed to escape from C. burnetii vacuoles. Labeling of amastigotes within C. burnetii vacuoles using a polyclonal antibody to C9 complement protein suggested that TcTOX (T. cruzi hemolysin) could play a role in parasite escape from C. burnetii. We concluded that T. cruzi has an outstanding adaptation capability and can survive within a hostile milieu such as C. burnetii vacuoles.     

Characterization of host cell-derived membrane proteins of the vacuole surrounding different intracellular forms of Trypanosoma cruzi in J774 cells. Evidence for phagocyte receptor sorting during the early stages of parasite entry.

Trypanosoma cruzi, an obligate intracellular protozoan parasite, exhibits developmental regulation of virulence. Although both noninfective epimastigote and infective trypomastigote stages of T. cruzi enter phagocytic cells via the formation of a parasitophorous vacuole (PV), only the latter developmental stages survive ingestion and perpetuate the infection. To determine whether the membrane composition of PV surrounding these different stages might contribute to differences in the outcome of infection, we identified selected membrane constituents by immunofluorescence and intracellular radioiodination, and studied their incorporation into PV. Complement receptors (CR3) are incorporated preferentially into the PV membrane surrounding serum-opsonized epimastigotes but not culture-derived metacyclic trypomastigotes. FcR are not preferentially incorporated into PV membranes unless epimastigotes or culture-derived metacyclic trypomastigotes are opsonized with anti-T. cruzi antibody. PV surrounding either parasite stage contain beta 1 integrins and lysosomal membrane glycoproteins (lgp). These results indicate that the plasma membrane glycoproteins incorporated into the surrounding PV membrane differ depending upon the stage of parasite being internalized, and that these differences reflect, at least in part, selective ligation of cell surface receptors mediating uptake. Furthermore, they imply that although virulent trypomastigote stages may avoid host cell uptake by conventional phagocytic receptors, i.e., CR3 or FcR, they do not escape fusion with an lgp-containing vacuole where they could still be exposed to lysosomal antimicrobial mechanisms.     

Metabolic studies by 1H NMR of different forms of Trypanosoma cruzi as obtained by 'in vitro' culture

Abstract By culturing Trypanosoma cruzi epimastigotes in modified Grace's medium with 10% foetal bovine serum, a significant quantity of metacyclic forms could be obtained. Transformation was observed after 8 days of culture, with metacyclic forms reaching 75%. Cultured Vero cells were infected with metacyclic forms and maintained until free-amastigote forms were obtained. Additionally, amastigote-like forms could be obtained by subjecting metacyclic cultures to heat shock. Parasites were grown with glucose as the major carbon source. The metabolites produced and excreted during culture were identified by difference proton nuclear magnetic resonance spectroscopy and quantified by enzymatic methods. The final products of glucose catabolism differed not only quantitatively but also qualitatively for the three major life-cycle stages of T. cruzi . The end products of metabolism produced by epimastigote forms were mainly acetate and pyruvate and, to a lesser extend, l-alanine and ethanol. Differences between epimastigotes and metacyclic forms were only quantitative. However, free amastigotes as well as amastigote-like forms, excreted acetate, glycerol, and pyruvate and to a lesser extent succinate, but no l-alanine or ethanol.     

Complement-mediated lysis of Trypanosoma cruzi trypomastigotes by human anti-alpha-galactosyl antibodies.

Antibodies that lyse trypomastigotes in a complement-mediated reaction are believed to be the main participants in the protection against virulent Trypanosoma cruzi. Antibodies with a specificity for alpha-galactosyl-containing determinants--generally called antiGal--were studied to determine their role in the lysis of trypomastigote forms. The titers of antiGal markedly increase in Chagas's disease. In the present study we demonstrate binding of this antibody to T. cruzi and the complement-mediated lysis of trypomastigotes by antiGal. Lysis of metacyclic trypomastigotes by whole Chagasic (Ch) serum or isolated antiGal fractions was equally inhibited by alpha- but not by beta-galactosides. Most of the lytic power of the Ch antiGal as well as of the whole Ch serum was removed by absorption on Synsorb-linked Gal alpha 1, 3Gal beta 1, 4GlcNAc followed by rabbit erythrocyte absorption. The Ch antiGal had a lower affinity for melibiose bound to agarose than for the trisaccharide linked to Synsorb, and was several times more effective in the immunolysis of trypomastigotes than the corresponding antiGal from normal human serum. Lytic antibodies were partly absorbed by Serratia marcescens but not by Escherichia coli O111. A human volunteer immunized with an S. marcescens vaccine elicited a specific antiGal response that was lytic to trypomastigotes (70% lysis). We suggest that in vivo high-affinity antiGal antibody clones, as occur in Ch patients, may significantly contribute to the destruction of the parasite, whereas low-affinity antiGal clones are much less effective in the protection against T. cruzi infection.     

The development of Trypanosoma cruzi in triatominae

Trypanosoma cruzi multiplies and differentiates in the digestive tract of triatomine insects. These insects ingest an enormous amount of blood, with ingestion followed very rapidly by a strong diuresis, slow digestion and occasionally long periods of starvation. Resulting changes in the intestinal environment induce the development of dominant stages of T. cruzi--epimastigotes and metacyclic trypomastigotes--and can be correlated with the appearance of specific developmental stages--spheromastigotes and giant cells--which otherwise are only rarely seen. Here, Astrid Kollien and Günter Schaub outline recent research on these developmental steps of T. cruzi in the vector, and the effects of different compounds acting against the parasite in the vector.     

Production of amastigotes from metacyclic trypomastigotes of Trypanosoma cruzi

Attempts to recreate all the developmental stages of Trypanosoma cruzi in vitro have thus far been met with partial success. It is possible, for instance, to produce trypomastigotes in tissue culture and to obtain metacyclic trypomastigotes in axenic conditions. Even though T. cruzi amastigotes are known to differentiate from trypomastigotes and metacyclic trypomastigotes, it has only been possible to generate amastigotes in vitro from the tissue-culture-derived trypomastigotes. The factors and culture conditions required to trigger the transformation of metacyclic trypomastigotes into amastigotes are as yet undetermined. We show here that pre-incubation of metacyclic trypomastigotes in culture (MEMTAU) medium at 37 degrees C for 48 h is sufficient to commit the parasites to the transformation process. After 72 h of incubation in fresh MEMTAU medium, 90% of the metacyclic parasites differentiate into forms that are morphologically indistinguishable from normal amastigotes. SDS-PAGE, Western blot and PAABS analyses indicate that the transformation of axenic metacyclic trypomastigotes to amastigotes is associated with protein, glycoprotein and antigenic modifications. These data suggest that (a) T. cruzi amastigotes can be obtained axenically in large amounts from metacyclic trypomastigotes, and (b) the amastigotes thus obtained are morphological, biological and antigenically similar to intracellular amastigotes. Consequently, this experimental system may facilitate a direct, in vitro assessment of the mechanisms that enable T. cruzi metacyclic trypomastigotes to transform into amastigotes in the cells of mammalian hosts.     

Platelet-activating factor-like activity isolated from Trypanosoma cruzi

Platelet-activating factor is a phospholipid mediator that exhibits a wide variety of physiological and pathophysiological effects, including induction of inflammatory response, chemotaxis and cellular differentiation. Trypanosoma cruzi, the etiological agent of Chagas' disease, is transmitted by triatomine insects and while in the triatomine midgut the parasite differentiates from a non-infective epimastigote stage into the pathogenic trypomastigote metacyclic form. We have previously demonstrated that platelet activating factor triggers in vitro cell differentiation of T. cruzi. Here we show a platelet activating factor-like activity isolated from lipid extract of T. cruzi epimastigotes incubated in the presence of [14C]acetate. Trypanosoma cruzi-platelet activating factor-like lipid induced the aggregation of rabbit platelets, which was prevented by platelet activating factor-acetylhydrolase. Mouse macrophage infection by T. cruzi was stimulated when epimastigotes were kept for 5 days in the presence of T. cruzi-platelet activating factor, before interacting with the macrophages. The differentiation of epimastigotes into metacyclic trypomastigotes was also triggered by T. cruzi-platelet activating factor. These effects were abrogated by a platelet activating factor antagonist, WEB 2086. Polyclonal antibody raised against mouse platelet activating factor receptor showed labelling for T. cruzi epimastigotes using immunoblotting and immunofluorescence assays. These data suggest that T. cruzi contain the components of an autocrine platelet activating factor-like ligand-receptor system that modulates cell differentiation towards the infectious stage.     

Changes in cell-surface carbohydrates of Trypanosoma cruzi during metacyclogenesis under chemically defined conditions.

Highly purified lectins with specificities for receptor molecules containing sialic acid, N-acetylglucosamine (D-GlcNAc), N-acetylgalactosamine (D-GalNAc), galactose (D-Gal), mannose-like residues (D-Man) or L-fucose (L-Fuc), were used to determine changes in cell-surface carbohydrates of the protozoal parasite Trypanosoma cruzi during metacyclogenesis under chemically defined conditions. Of the D-GalNAc-binding lectins, BS-I selectively agglutinated metacyclic trypomastigotes, MPL was selective for replicating epimastigotes, whereas SBA strongly agglutinated all developmental stages of T. cruzi. WGA (sialic acid and/or D-GlcNAc specific) was also reactive with differentiating epimastigotes and metacyclic trypomastigotes but displayed a higher reactivity with replicating epimastigote forms. A progressive decrease in agglutinating activity was observed for jacaline (specific for D-Gal) during the metacyclogenesis process; conversely, a progressive increase in affinity was observed for RCA-I (D-Gal-specific), although the reactivity of other D-Gal-specific lectins (PNA and AxP) was strong at all developmental stages. All developmental stages of T. cruzi were agglutinated by Con A and Lens culinaris lectins (specific for D-Man-like residues); however, they were unreactive with the L-fucose-binding lectins from Lotus tetragonolobos and Ulex europaeus. These agglutination assays were further confirmed by binding studies using 125I-labelled lectins. Neuraminidase activity was detected in supernatants of cell-free differentiation medium using the PNA hemagglutination test with human A erythrocytes. The most pronounced differences in lectin agglutination activity were observed between replicating and differentiating epimastigotes, suggesting that changes in the composition of accessible cell-surface carbohydrates precede the morphological transformation of epimastigotes into metacyclic trypomastigotes.     

Invasion of MDCK epithelial cells with altered expression of Rho GTPases by Trypanosoma cruzi amastigotes and metacyclic trypomastigotes of strains from the two major phylogenetic lineages

In order to invade mammalian cells, Trypanosoma cruzi infective forms cause distinct rearrangements of membrane and host cell cytoskeletal components. Rho GTPases have been shown to regulate three separate signal transduction pathways, linking plasma membrane receptors to the assembly of distinct actin filament structures. Here, we examined the role of Rho GTPases on the interaction between different T. cruzi infective forms of strains from the two major phylogenetic lineages with nonpolarized MDCK cells transfected with different Rho GTPase constructs. We compared the infectivity of amastigotes isolated from infected cells (intracellular amastigotes) with forms generated from the axenic differentiation of trypomastigotes (extracellular amastigotes), and also with metacyclic trypomastigotes. No detectable effect of GTPase expression was observed on metacyclic trypomastigote invasion and parasites of Y and CL (T. cruzi II) strains invaded to similar degrees all MDCK transfectants, and were more infective than either G or Tulahuen (T. cruzi I) strains. Intracellular amastigotes were complement sensitive and showed very low infectivity towards the different transfectants regardless of the parasite strain. Complement-resistant T. cruzi I extracellular amastigotes, especially of the G strain, were more infective than T. cruzi II parasites, particularly for the Rac1V12 constitutively active GTPase transfectant. The fact that in Rac1N17 dominant-negative cells, the invasion of G strain extracellular amastigotes was specifically inhibited suggested an important role for Rac1 in this process.     

Biological characterization of Trypanosoma cruzi strains

Biological parameters of five Trypanosoma cruzi strains from different sources were determined in order to know the laboratory behaviour of natural populations. The parameters evaluated were growth kinetics of epimastigotes, differentiation into metacyclic forms, infectivity in mammalian cells grown in vitro and parasite susceptibility to nifurtimox, benznidazole and gentian violet. Differences in transformation to metacyclic, in the percentage of infected cells as well as in the number of amastigotes per cell were observed among the strains. Regarding to pharmacological assays, Y strain was the most sensitive to the three assayed compounds. These data demonstrate the heterogeneity of natural populations of T. cruzi, the only responsible of infection in humans.     

Developmental stages of Trypanosoma cruzi-like flagellates in Cavernicola pilosa

The developmental stages of Trypanosoma cruzi ssp., found in the intestinal tract of Cavernicola pilosa, are described and measurements given for nine life stages. The frequencies of the various stages in foregut, midgut and hindgut of the triatomines are provided; parasites were rare in the foregut and metatrypomastigotes were seen only in the mid- and hindguts. All adult bugs examined harboured intestinal infections of T. cruzi-like flagellates, large clumps of amastigotes were frequently observed in the midgut. The faeces of C. pilosa, containing metacyclic trypomastigotes, did not produce patent parasitaemia when inoculated into mice. Inoculated mice were not protected against subsequent challenge infections with the highly virulent Tulahuen stock of T. c. cruzi. The blood of bats also failed to produce parasitaemia when inoculated into mice, nor were the mice protected against subsequent challenges with T. c. cruzi. Although the developmental stages described were very similar to those of T. c. cruzi it is presumed that they were stages of T. c. marinkellei because of their failure to infect mice and Rhodnius prolixus, and their failure to protect inoculated mice against challenge with T. c. cruzi.     

Actin-rich structures formed during the invasion of cultured cells by infective forms of Trypanosoma cruzi

Previous work has shown that Trypanosoma cruzi extracellular amastigotes as well as metacyclic trypomastigotes infect cultured cells in a highly specific parasite form-cell type interaction. In this work we have investigated the mode of interaction of both forms with HeLa and Vero cells using scanning electron and confocal fluorescence microscopy. We examined the distribution of several host cell components as well as extracellular matrix elements during cell invasion by both T. cruzi infective forms. Scanning electron microscopy showed that membrane expansions formed during the invasion of cells by extracellular amastigotes. These expansions correspond to small cup-like structures in HeLa cells and are comparatively larger "crater"-like in Vero cells. We detected by confocal microscopy actin-rich structures associated with the internalisation of both infective forms of the parasite that correspond to the membrane expansions. Confocal fluorescence microscopy combining DIC images of cells labelled with monoclonal antibodies to phosphotyrosine, cytoskeletal elements, integrins, and extracellular matrix components revealed that some of the components like gelsolin and alpha-actinin accumulate in actin-rich structures formed in the invasion of amastigotes of both cell types. Others, like vinculin and alpha2 integrin may be present in these structures without evident accumulation. And finally, some actin-rich processes may be devoid of components like fibronectin or alphaV integrin. These studies provide evidence that the repertoire of host cell/extracellular matrix components that engage in the invasion process of T. cruzi forms is cell type- and parasite form-dependent.     

Cryptic epitope explains the failure of a monoclonal antibody to bind to certain isolates of Trypanosoma cruzi

A mouse monoclonal antibody, WIC 29.26 Ab, has previously been characterized as recognizing a carbohydrate epitope on a 72,000 m.w. glycoprotein (GP72) expressed on the surface of Trypanosoma cruzi epimastigotes and metacyclic trypomastigotes. This molecule has been implicated as a receptor in the control of parasite transformation, and when used as an immunogen in mice, partially protects against T. cruzi infection. In previous experiments in which a radioimmunoassay was used, WIC 29.26 Ab was found to react with approximately 50% of T. cruzi strains and clones derived from a variety of sources. In this study, we attempted to determine whether the WIC 29.26 Ab-nonreactive isolates lack the entire GP72 or merely lack the epitope recognized by this monoclonal antibody. WIC 226.4 Ab, a monoclonal antibody raised against periodate-treated GP72, reacted in an immunofluorescence assay with all strains and clones studied, including those which had not reacted with WIC 29.26 Ab. Likewise, two polyvalent rabbit sera, directed specifically against GP72, bound to all T. cruzi isolates tested. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of detergent lysates of surface-labeled epimastigotes immunoprecipitated with WIC 29.26 Ab showed that the epitope bound by this antibody was present in all but one of the parasites that were surface-nonreactive, as well as in all those that were surface-reactive. WIC 29.26 Ab precipitated a single 72K Mr band from most strains and clones, but in several cases 79K Mr and 66K Mr bands were seen. Isolates from both the surface-reactive and the surface-nonreactive groups showed the latter pattern. These results demonstrate that GP72, or similar electrophoretic variants--and with one exception, the carbohydrate epitope bound by WIC 29.26 Ab--are present in the surface membrane of all strains and clones tested. This observation suggests that in intact epimastigotes of the surface-nonreactive isolates, the epitope is not accessible because of structural changes in the molecule itself or because of differences in the membrane environment of GP72.     

Trypanosoma cruzi proteins which are antigenic during human infections are located in defined regions of the parasite

Polyclonal antibodies obtained against antigenic proteins encoded by six recombinant DNA clones of Trypanosoma cruzi were used for the ultrastructural localization of the respective antigens in thin sections of parasites (epimastigote, amastigote and trypomastigote forms of T. cruzi) embedded at low temperature in Lowicryl K4M resin. Antigens of high molecular weight containing tandemly repeated amino acid sequence motifs and recognized by sera from patients with Chagas' disease, were located only in the flagellum, where it contacts the parasite cell body. Other antigens were located on the surface of the parasite while still others were found within the flagellar pocket, as is the case with an antigen released during the acute phase of Chagas' disease. Thus, we conclude that some of the T. cruzi proteins which are antigenic in human infections are located in defined regions of the parasite. Some of the antigens were not expressed to the same extent in the three different developmental stages of the parasite.     

Novel strategy in Trypanosoma cruzi cell invasion: implication of cholesterol and host cell microdomains

Trypanosoma cruzi, the etiological agent of Chagas' disease, is an obligatory intracellular parasite in the mammalian host. In order to invade a wide variety of mammalian cells, T. cruzi engages parasite components that are differentially expressed among strains and infective forms. Because the identification of putative protein receptors has been particularly challenging, we investigated whether cholesterol and membrane rafts, sterol- and sphingolipid-enriched membrane domains, could be general host surface components involved in invasion of metacyclic trypomastigotes and extracellular amastigotes of two parasite strains with distinct infectivities. HeLa or Vero cells treated with methyl-beta-cyclodextrin (MbetaCD) are less susceptible to invasion by both infective forms, and the effect was dose-dependent for trypomastigote but not amastigote invasion. Moreover, treatment of parasites with MbetaCD only inhibited trypomastigote invasion. Filipin labeling confirmed that host cell cholesterol concentrated at the invasion sites. Binding of a cholera toxin B subunit (CTX-B) to ganglioside GM1, a marker of membrane rafts, inhibited parasite infection. Cell labeling with CTX-B conjugated to fluorescein isothiocyanate revealed that not only cholesterol but also GM1 is implicated in parasite entry. These findings thus indicate that microdomains present in mammalian cell membranes, that are enriched in cholesterol and GM1, are involved in invasion by T. cruzi infective forms.     

Trypanosoma cruzi immune evasion mediated by host cell-derived microvesicles

The innate immune system is the first mechanism of vertebrate defense against pathogen infection. In this study, we present evidence for a novel immune evasion mechanism of Trypanosoma cruzi, mediated by host cell plasma membrane-derived vesicles. We found that T. cruzi metacyclic trypomastigotes induced microvesicle release from blood cells early in infection. Upon their release, microvesicles formed a complex on the T. cruzi surface with the complement C3 convertase, leading to its stabilization and inhibition, and ultimately resulting in increased parasite survival. Furthermore, we found that TGF-β-bearing microvesicles released from monocytes and lymphocytes promoted rapid cell invasion by T. cruzi, which also contributed to parasites escaping the complement attack. In addition, in vivo infection with T. cruzi showed a rapid increase of microvesicle levels in mouse plasma, and infection with exogenous microvesicles resulted in increased T. cruzi parasitemia. Altogether, these data support a role for microvesicles contributing to T. cruzi evasion of innate immunity.     

The increase in mannose receptor recycling favors arginase induction and Trypanosoma cruzi survival in macrophages

The macrophage mannose receptor (MR) is a pattern recognition receptor of the innate immune system that binds to microbial structures bearing mannose, fucose and N-acetylglucosamine on their surface. Trypanosoma cruzi antigen cruzipain (Cz) is found in the different developmental forms of the parasite. This glycoprotein has a highly mannosylated C-terminal domain that participates in the host-antigen contact. Our group previously demonstrated that Cz-macrophage (Mo) interaction could modulate the immune response against T. cruzi through the induction of a preferential metabolic pathway. In this work, we have studied in Mo the role of MR in arginase induction and in T. cruzi survival using different MR ligands. We have showed that pre-incubation of T. cruzi infected cells with mannose-Bovine Serum Albumin (Man-BSA, MR specific ligand) biased nitric oxide (NO)/urea balance towards urea production and increased intracellular amastigotes growth. The study of intracellular signals showed that pre-incubation with Man-BSA in T. cruzi J774 infected cells induced down-regulation of JNK and p44/p42 phosphorylation and increased of p38 MAPK phosphorylation. These results are coincident with previous data showing that Cz also modifies the MAPK phosphorylation profile induced by the parasite. In addition, we have showed by confocal microscopy that Cz and Man-BSA enhance MR recycling. Furthermore, we studied MR behavior during T. cruzi infection in vivo. MR was up-regulated in F4/80+ cells from T. cruzi infected mice at 13 and 15 days post infection. Besides, we investigated the effect of MR blocking antibody in T. cruzi infected peritoneal Mo. Arginase activity and parasite growth were decreased in infected cells pre-incubated with anti-MR antibody as compared with infected cells treated with control antibody. Therefore, we postulate that during T. cruzi infection, Cz may contact with MR, increasing MR recycling which leads to arginase activity up-regulation and intracellular parasite growth.     

Different infective forms trigger distinct immune response in experimental Chagas disease

Although metacyclic and blood trypomastigotes are completely functional in relation to parasite-host interaction and/or target cell invasion, they differ in the molecules present on the surface. Thus, aspects related to the variability that the forms of T. cruzi interacts with host cells may lead to fundamental implications on the immune response against this parasite and, consequently, the clinical evolution of Chagas disease. We have shown that BT infected mice presented higher levels of parasitemia during all the acute phase of infection. Moreover, the infection with either MT or BT forms resulted in increased levels of total leukocytes, monocytes and lymphocytes, specifically later for MT and earlier for BT. The infection with BT forms presented earlier production of proinflammatory cytokine TNF-α and later of IFN-γ by both T cells subpopulations. This event was accompanied by an early cardiac inflammation with an exacerbation of this process at the end of the acute phase. On the other hand, infection with MT forms result in an early production of IFN-γ, with subsequent control in the production of this cytokine by IL-10, which provided to these animals an immunomodulatory profile in the end of the acute phase. These results are in agreement with what was found for cardiac inflammation where animals infected with MT forms showed intense cardiac inflammation later at infection, with a decrease in the same at the end of this phase. In summary, our findings emphasize the importance of taking into account the inoculums source of T. cruzi, since vectorial or transfusional routes of T. cruzi infection may trigger distinct parasite-host interactions during the acute phase that may influence relevant biological aspects of chronic Chagas disease.