Identification of antigens of culture forms of Trypanosoma cruzi and Trypanosoma rangeli recognized by sera from patients with chronic Chagas' disease

Experimental Chagas disease in Balb/c mice previously vaccinated with T. rangeli. II. The innate immune response shows immunological memory: reality or fiction?

Trypanosoma cruzi is a real challenge to the host's immune system, because it requires strong humoral and cellular immune response to remove circulating trypomastigote forms, and to prevent the replication of amastigote forms in tissues, involving many regulator and effector components. This protozoan is responsible for Chagas disease, a major public health problem in Latinamerica. We have developed a model of vaccination with Trypanosoma rangeli, a parasite closely related to T. cruzi, but nonpathogenic to humans, which reduces the infectiousness in three different species of animals, mice, dogs and guinea pigs, against challenge with T. cruzi. In a previous work, we demonstrated that mice vaccinated with T. rangeli showed important soluble mediators that stimulate phagocytic activity versus only infected groups. The aim of this work was to study the innate immune response in mice vaccinated or not with T. rangeli. Different population cells and some soluble mediators (cytokines) in peritoneal fluid and plasma in mice vaccinated-infected and only infected with T. cruzi were studied. In the first hours of challenge vaccinated mice showed an increase of macrophages, NK, granulocytes, and regulation of IL6, IFNγ, TNFα and IL10, with an increase of IL12, with respect to only infected mice. Furthermore an increase was observed of Li T, Li B responsible for adaptative response. Finally the findings showed that the innate immune response plays an important role in vaccinated mice for the early elimination of the parasites, complementary with the adaptative immune response, suggesting that vaccination with T. rangeli modulates the innate response, which develops some kind of immunological memory, recognizing shared antigens with T. cruzi. These results could contribute to the knowledge of new mechanisms which would have an important role in the immune response to Chagas disease.

Experimental Chagas disease. Innate immune response in Balb/c mice previously vaccinated with Trypanosoma rangeli. I. The macrophage shows immunological memory: Reality or fiction?

Chagas' disease, caused by Trypanosoma cruzi, is a major vector borne health problem in Latin America and an emerging or re-emerging infectious disease in several countries. Immune response to T. cruzi infection is highly complex and involves many components, both regulators and effectors. Although different parasites have been shown to activate different mechanisms of innate immunity, T. cruzi is often able to survive and replicate in its host because they are well adapted to resisting host defences. An experimental model for vaccinating mice with Trypanosoma rangeli, a parasite closely related to T. cruzi, but nonpathogenic to humans, has been designed in our laboratory, showing protection against challenge with T. cruzi infection. The aim of this work was to analyze some mechanisms of the early innate immune response in T. rangeli vaccinated mice challenged with T. cruzi. For this purpose, some interactions were studied between T. cruzi and peritoneal macrophages of mice vaccinated with T. rangeli, infected or not with T. cruzi and the levels of some molecules or soluble mediators which could modify these interactions. The results in vaccinated animals showed a strong innate immune response, where the adherent cells of the vaccinated mice revealed important phagocytic activity, and some soluble mediator (Respiratory Burst: significantly increase, p ≤ 0.03; NO: the levels of vaccinated animals were lower than those of the control group; Arginasa: significantly increase, p ≤ 0.04). The results showed an important role in the early elimination of the parasites and their close relation with the absence of histological lesions that these animals present with regard to the only infected mice. This behaviour reveals that the macrophages act with some type of memory, recognizing the antigens to which they have previously been exposed, in mice were vaccinated with T. rangeli, which shares epitopes with T. cruzi.

Modulation of immune response in experimental Chagas disease

Trypanosoma cruzi (T. cruzi), the etiological agent of Chagas disease, affects nearly 18 million people in Latin America and 90 million are at risk of infection. The parasite presents two stages of medical importance in the host, the amastigote, intracellular replicating form, and the extracellular trypomastigote, the infective form. Thus infection by T. cruzi induces a complex immune response that involves effectors and regulatory mechanisms. That is why control of the infection requires a strong humoral and cellular immune response; hence, the outcome of host-parasite interaction in the early stages of infection is extremely important. A critical event during this period of the infection is innate immune response, in which the macrophage’s role is vital. Thus, after being phagocytized, the parasite is able to develop intracellularly; however, during later periods, these cells induce its elimination by means of toxic metabolites. In turn, as the infection progresses, adaptive immune response mechanisms are triggered through the TH1 and TH2 responses. Finally, T. cruzi, like other protozoa such as Leishmania and Toxoplasma, have numerous evasive mechanisms to the immune response that make it possible to spread around the host. In our Laboratory we have developed a vaccination model in mice with Trypanosoma rangeli, nonpathogenic to humans, which modulates the immune response to infection by T. cruzi, thus protecting them. Vaccinated animals showed an important innate response (modulation of NO and other metabolites, cytokines, activation of macrophages), a strong adaptive cellular response and significant increase in specific antibodies. The modulation caused early elimination of the parasites, low parasitaemia, the absence of histological lesions and high survival rates. Even though progress has been made in the knowledge of some of these mechanisms, new studies must be conducted which could target further prophylactic and therapeutic trials against T. cruzi infection.

Trypanosoma rangeli Tejera, 1920, in chronic Chagas' disease patients under ambulatory care at the Evandro Chagas Clinical Research Institute (IPEC-Fiocruz, Brazil)

We report the finding, the isolation by hemoculture, and the characterization of Trypanosoma rangeli stocks from two chronic Chagas' disease patients who received ambulatory care at the Evandro Chagas Clinical Research Institute (IPEC, FIOCRUZ). Both patients proceeded from Bahia State (Brazil). One of them presented the cardiac form of the disease and the other indeterminate symptomalogy. Giemsa-stained smears of the hemocultures from these patients evidenced that they were coinfected with T. rangeli and Trypanosoma cruzi, with predominance of the former species. These isolates could only be successfully grown in Novy-MacNeal-Nicolle + liver infusion-tryptose supplemented with 20-30% fetal calf serum. After 6 months of serial maintenance, rich and apparently pure cultures of T. rangeli were obtained. Both stocks were analyzed with different approaches and compared with two T. cruzi isolates also from chagasic patients under care at IPEC, besides T. rangeli and T. cruzi reference strains. All stocks were characterized by morphology, biometry, electrophoresis of isoenzymes, and products of kDNA minicircle amplified by polymerase chain reaction. The identification of T. rangeli was largely confirmed by all techniques. Taken together, these data represent the third report on T. rangeli in human hosts in Brazil.

Isolation, purification and characterization of GPI-anchored membrane proteins from Trypanosoma rangeli and Trypanosoma cruzi

GPI-anchored proteins from plasma membrane of Trypanosoma rangeli and Trypanosoma cruzi epimastigotes were isolated and characterized using the partition Triton X-114 method. The detection by Western blot of specific proteins of 90, 85 and 56 kDa molecular mass in T. rangeli compared to those of 30, 70 and 100 kDa detected in T. cruzi demonstrates specific discrimination between these two species of Trypanosoma. The potential diagnostic value of the here reported proteins to differentiate mixed infections by T. cruzi and T. rangeli is evaluated and its potential for epidemiological studies of Chagas disease in endemic areas is also discussed.

Further morphological studies on the behavior of Trypanosoma rangeli in the hemocytes of Rhodnius prolixus

The hemocytes of Rhodnius prolixus were analyzed during the course of infection with the protozoan Trypanosoma rangeli. The following cell types were identified: prohemocyte, plasmatocyte, adipocyte, granular cell and oenocytoid. The number of these cells changes during the infection course thus indicating a cell response to infection of R. prolixus by T. rangeli. Transmission electron microscopy showed that plasmatocytes were able to ingest epimastigote forms of the parasite, which were then found within a parasitophorous vacuole. Amorphous material was seen within the vacuole suggesting that fusion of host cell lysosomes with the vacuole took place. Intravacuolar parasites in process of digestion were observed. In addition, reaction product indicative of the presence of acid phosphatase was observed in parasite-containing vacuoles. No dividing parasites were seen within the vacuole in contrast to what was observed outside the host cells.

Trypanosoma (Herpetosoma) rangeli Tejera, 1920: an updated review

Trypanosoma rangeli, a parasite generally considered non-pathogenic for man, is the second species of human trypanosome to be reported from the New World. The geographical distribution of T. rangeli often overlaps with that of T. cruzi, the same vertebrate and invertebrate hosts being infected. Their differentiation thus becomes of real, practical importance, particularly as they share approximately half the antigenic determinants recognized by the humoral response. Little is known about the life cycle of T. rangeli in the vertebrate host, although thousands of human and wild animal infections have been reported. Recent studies have revealed 2 major phylogenetic lineages in T. rangeli having different characteristics, thus leading to better understanding of the epidemiology and interactions with this parasite's vertebrate hosts and triatomine vectors. Based on further genetic characterization analysis, the authors have proposed 2 alternative hypotheses and consider that T. rangeli could have had clonal evolution or have been subjected to speciation processes.

Antigenic significance of a Trypanosoma rangeli sialidase

The Trypanosoma rangeli-secreted sialidase was purified by bovine submaxillary gland mucin-sepharose affinity chromatography. In immunoblotting analysis, antibodies raised against this molecule recognized polypeptides of 73 kDa in T. rangeli medium supernatant (TrSialr) and of 70 kDa in the cell lysates of T. rangeli (TrSials) and T. cruzi (TcSialL) epimastigotes. TrSialr, TrSials, and TcSialL were subjected to proteolytic cleavage with papain; the resultant peptide pattern displayed differences in the immunoblotting profiles. TrSials was purified by immunoprecipitation, and this protein band was recognized by sera from T. cruzi-infected chronic mice and Chagas' disease patients. In contrast, TrSialr was not recognized by these sera. The antibodies from the infected mice also recognized a band of 70 kDa present in the medium. These preliminary observations imply that the released and somatic sialidases are partially different molecules, with probably different biological roles. The related proteins recognized in T. rangeli and T. cruzi epimastigotes share many antigenic characteristics but have some structural differences, probably related to their function in the parasitic cell. On the basis of the strong antigenicity of TrSials, this molecule is proposed as the antigen for the detection of antibodies arising during T. cruzi infection.

An electron microscopic study of penetration by Trypanosoma rangeli into midgut cells of Rhodnius prolixus

The process of interaction of the Choachi strain of Trypanosoma rangeli with intestinal epithelial cells of Rhodnius prolixus was analyzed in experiments carried out in vitro and in vivo. For the in vitro experiments small fragments of the anterior region of the posterior midgut were incubated in the presence of the parasites, fixed, and processed for observation with the scanning electron microscope. Parasites attached to the surface of some epithelial cells, especially to the extracellular membrane layers (perimicrovillar membranes), were observed. For the in vivo experiments insects were infected with cultures of T. rangeli, sacrificed at different time intervals, and then processed for scanning and transmission electron microscopy. An intimate contact between the parasites and the membrane layers was observed. The parasites penetrated into cells that showed an electronlucent cytoplasm and a damaged surface, moved within the cytoplasm of the epithelial cell, reached the basal region, crossed the basal lamina, and entered the hemocoel.

[Review of the biologic and diagnostic aspects of Trypanosoma (Herpetosoma) rangeli]

This review has three objectives: a) To stimulate further research of this prevalent human infection b) to examine the progress of current diagnostic techniques and c) to emphasise the significance of the flagellate parasite Trypanosoma (Herpetosoma) rangeli in Chagas' Disease endemic areas of South and Central America. Both Trypanosoma rangeli and Trypanosoma cruzi overlap in many of the areas of Latin America utilising the same triatomine vectors. Also a vast range of mammalian species have been found naturally infected with T. rangeli. The biology of the parasitism of T. rangeli is revised and emphasis is given regarding its biological cycle. T. cruzi and T. rangeli share common antigens and cross react serologically. Human infection in the chronic phase may be misdiagnosed as T. cruzi infection. Conventional and modern diagnostic and identification methods are discussed. Unfortunately we do not know the real distribution of T. rangeli infections in most areas and epidemiological studies to examine concomitant dual infections deserve further investigation.

Karyotype variability in Trypanosoma rangeli

The molecular karyotypes of several different protozoan parasites show high intra-species variation, including different kinetoplastids such as Trypanosoma brucei, Trypanosoma cruzi and Leishmania ssp. In this study, the molecular karyotype of Trypanosoma rangeli was examined. To evaluate potential intra-species molecular karyotype variations, 16 different samples were studied by pulsed field gel electrophoresis (PFGE) followed by ethidium bromide staining and hybridizations with 6 different probes. The result showed that different T. rangeli populations are highly polymorphic regarding the molecular karyotype, and thus suggests that PFGE analysis can be used for classification of different T. rangeli isolates. In addition, the molecular karyotype of T. rangeli was compared to molecular karyotypes of other kinetoplastids, and was shown to be distinctly different from that of T. cruzi, but shows some similarities with the karyotype described for T. brucei. Among the probes used one was identified as highly polymorphic, and thus informative for studies of different T. rangeli populations, and another was useful for differentiation between T. rangeli and T. cruzi.

Comparison of chagasic and non-chagasic myocardiopathies by ELISA and immunoblotting with antigens of Trypanosoma cruzi and Trypanosoma rangeli

Trypanosoma cruzi associated myocardiopathy, or Chagas disease, continues to be a serious problem in Venezuela, for which there is neither a vaccine nor a cure. In order to learn more about the humoral immune response to trypanosomal antigens, and to try to identify dominant antigens, we used ELISA and immunoblotting to study the reactivity of sera from patients with chagasic and non-chagasic myocardiopathies, against surface and secreted proteins from T. cruzi and T. rangeli. Both species are found in the same insect vector, but only T. cruzi is thought to be pathogenic in vertebrates. The ELISA results fell into three patterns: (1) high reactivity values with both T. cruzi and T. rangeli surface and secreted proteins; (2) high values to T. cruzi but low values with T. rangeli; and (3) high values to T. rangeli and low values with T. cruzi. This finding that some chagasic sera react more strongly against T. rangeli than against T. cruzi is intriguing, and warrants further investigation. When chagasic sera were tested on Western blots of total extracts of T. cruzi and T. rangeli, the pattern of reactive bands was similar against both parasites, but no two sera showed an identical pattern. Furthermore, there was no correlation between a particular immunoblotting pattern and either the antibody titer, or the severity of the disease. Several T. cruzi and T. rangeli antigens were recognized by sera from healthy controls as well as from patients with other tropical diseases endemic in Venezuela. Overall, our results suggest that the humoral immune response to trypanosomal antigens is complex, and no single antigen may be the determining factor in the pathogenesis of chagasic myocardiopathy.

Trypanosoma rangeli sialidase lacks trans-sialidase activity

Extracts and tissue culture supernatants of axenic forms of T. rangeli were assayed for the presence of sialidase and trans-sialidase activities. Using sialyl(alpha 2-3)lactose, sialyl(alpha 2-6)lactose, poly(alpha 2-8)N-acetylneuraminic acid, fetuin and 4-methylumbelliferyl-N-acetylneuraminic acid as sialic acid donors, and lactose as a sialic acid acceptor, no trans-sialidase activity was detected. Nevertheless, T. rangeli lysates and culture supernatants contain a sialidase that hydrolyzes sialyl(alpha 2-3)lactose, and much less efficiently sialyl(alpha 2-6)lactose, but not poly(alpha 2-8)N-acetylneuraminic acid. T. cruzi trans-sialidase hydrolyzed only sialyl(alpha 2-3)lactose under the same conditions. The T. rangeli and the T. cruzi enzymes differ antigenically and in their pH optimum for hydrolase activity.

Trypanosoma (Herpetosoma) rangeli Tejera, 1920. Intracellular amastigote stages of reproduction in white mice

The method, site, and stage of multiplication of Trypanosoma (Herpetosoma) rangeli Tejera, 1920 has not hitherto been known. "We have now observed many intracellular nests or pseudocysts, containing amastigotes and trypomastigotes of this parasite in the heart, liver, and spleen of suckling (5.0 g) male white mice (NMRI strain) inoculated i.p. with 9 x 10(4) metatrypomastigotes/g body weight from a 12-day-old culture of the "Dog-82" strain of T. rangeli. At the peak of parasitemia (1.9 x 10(6) trypomastigotes/ml blood, 3 days post-inoculation) various tissues were taken for sectioning and staining. The heart was most intensely parasitized. The amastigotes were rounded or ellipsoidal, with a rounded nucleus and the kinetoplast in the form of a straight or curved bar; the average maximum diameter of 50 measured amastigotes was 4.2 p. Binary fission was seen in the nucleus and kinetoplast of some amastigotes; no blood trypomastigotes were seen in division. The above characteristics, as well as the location of the pseudocysts in the tissues, are similar to T. cruzi. Comparison of these results with those reported for other Herpetosoma suggest study of the taxonomic position of T. rangeli.