Vaccination with epimastigotes of different strains of Trypanosoma rangeli protects mice against Trypanosoma cruzi infection

In our laboratory, we have developed a model of vaccination in mice with Trypanosoma rangeli, a non-pathogenic parasite that shares many antigens with Trypanosoma cruzi. The vaccinated mice were protected against infection with virulent T. cruzi. The goal of the present work was to study the protective activity of strains of T. rangeli of different origin, with the aim of analysing whether this protective capacity is a common feature of T. rangeli. BALB/c mice were vaccinated with live or fixed epimastigotes of two T. rangeli strains, Choachi and SC-58. Vaccinated (VM) and control mice (CM) were infected with virulent T. cruzi, Tulahuen strain. The results showed that the levels of parasitemia of VM, vaccinated with the two strains of T. rangeli were significantly lower than those developed in CM. The survival rate of VM was higher than that CM. Histological studies revealed many amastigote nests and severe inflammatory infiltrates in the heart and skeletal muscles of CM, whereas in the VM only moderate lymphomonocytic infiltrates were detected. Altogether, the results of the present work as well as previous studies show that the antigens involved in the protection induced by T. rangeli are expressed in different strains of this parasite. These findings could prove useful in vaccine preparation.

Immunohistochemical characterization of mononuclear cells and MHC II expression in the brain of horses with experimental chronic Trypanosoma evansi infection / Caracterização imunoistoquímica de células mononucleares e expressão de CMH II no sistema nervoso central de eqüinos com infecção crônica experimental por Trypanosoma evansi

An histochemical and immunohistochemical study was carried out to evaluate the mechanisms of immune response of horses experimentally infected by Trypanosoma evansi. For this purpose the HE histochemical stain and the avidin biotin peroxidase method were used. To determine the presence and immunoreactivity of immune cells we used anti-major histocompatibility complex II antibodies. Cellular infiltration fenotype was characterized with the aid of anti-CD3 antibody for T lymphocytes and by anti-BLA 36 antibodies for B lymphocytes. Macrophages were marked with an antibody against myeloid/histyocites antigen (clone Mac387). Lesions in the CNS of experimentally infected horses were those of a wide spread non suppurative encephalomyelitis and meningomyelitis. The severity of lesions varied in different parts of the nervous system, reflecting an irregular distribution of inflammatory vascular changes. Lymphoid perivascular cuffs and meningeal infiltrations were of predominantly composed of T and B cells. The parasite, T. evansi, was not identified in these horses tissues.

Este estudo objetivou caracterizar a resposta imune celular no sistema nervoso central (SNC) de eqüinos com infecção crônica experimental por Trypanosoma evansi. Para este propósito, foram utilizados os métodos histoquímicos (HE) e imunoistoquímicos do complexo avidina-biotina peroxidase (ABC). O fenótipo do infiltrado celular foi caracterizado com o auxílio de anticorpos anti - CD3, para linfócitos T e antiBLA36 para linfócitos B. Os macrófagos foram marcados com anticorpo antiantígenos da linhagem mielóide/histiócitos (Clone Mac387). A lesão no sistema nervoso central (SNC) dos eqüinos infectados com T. evansi foi caracterizada como meningoencefalite e meningomielite não supurativa. A gravidade das lesões variou em diferentes segmentos do SNC, refletindo distribuição irregular das alterações vasculares. A distribuição de células T e B e antígenos do complexo maior de histocompatibilidade classe II foram avaliados dentro do SNC de eqüinos cronicamente infectados com T. evansi. O infiltrado perivascular e meníngeo eram constituídos predominantemente por células T e B. Macrófagos foram raramente visualizados. T.evansi não foi identificado no parênquima do SNC dos eqüinos.

Parasitological and immunological studies on rats experimental infected with Saudi Arabian strain of Trypanosoma evansi

Surra, an enzootic disease caused by Trypanosoma evansi, is one of the most important trypanosomiasis in Kingdom of Saudi Arabia. The state of parasitaemia in relation to the corresponding humoral response in experimentally infected Wister rats for 15 days were investigated. The prepatent period was found to be 5 days. The disease was characterized by intermittent fluctuation of parasitaemia and a significant difference in the level of parasitaemia [P >0.05] was detected in specimens of day 7, 9, 13 and 14. There was a difference in the mean number of blood parasites in relation to sex throughout the 15 days of the study. This difference was statistically significant [P <0.05]. Using in direct haemagglutination serological test, almost all inoculated rats displayed specific antibodies of diagnostic value on day 7 after infection ranging between 1/80-1/160. Thereafter, antibody titers increased progressively to reach very high positive dilutions of >1/2048 in all animals at the end of study on day 15. No sex difference could be observed in both serological specimens of 7 and 15 days. Also no correlation was observed between the state of parasitaemia and the serological titers in infected rats

Specific antibody levels and antigenic recognition of Wistar rats inoculated with distinct isolates of Trypanosoma evansi

"Mal de Cadeiras", an enzootic disease caused by Trypanosoma evansi, is one of the most important trypanosomiases in the Brazilian Pantanal region. The disease affects mainly horses, which are widely used in extensive cattle production, an activity of greatest economical significance for the region. The parasite also infects sylvan (coatis and capybaras) and domestic (dogs) animals, respectively considered wild and domestic reservoirs of T. evansi. For a better understanding of the interaction of T. evansi with its rodent host, we evaluated the differences in the specific antibody level patterns and in the parasitic peptides recognition patterns of experimentally infected Wistar rats. The rats experimentally infected with T. evansi isolates obtained from coatis, dogs and horses were submitted to indirect immunofluorescence test (IgM e IgG) and Western blotting. The serological titers for IgM and IgG ranged between 1:40 and 1:160. The most recognized polypeptide profiles were in a range of 17 and 74 kDa. Our data suggest that the humoral immune response in Wistar rats is not sufficient for granting an effective control of T. evansi infections

Clinical, parasitological and immunological aspects of experimental infection with Trypanosoma evansi in dogs

This research investigated the pattern of antibody response by means of enzyme linked immunosorbent assay (Elisa) and indirect fluorescent antibody test (IFAT) through the course of experimental Trypanosoma evansi infetion in dogs. Clinical and parasitological features were also studied. The average prepatent period was 11.2 days and parasitaemia showed an undulating course. Biometrical study of parasites revealed a mean total length of 21.68mm. The disease was charcterized by intermittent fever closely related to the degree of parasitaemia and main clinical signs consisted of pallor of mucous membrane, edema, progressive emaciation and enlargement of palpable lymph nodes. Diagnostic antibody was detected within 12 to 15 days and 15 to 19 days of infection by IFAT and Elisa, respectively. High and persistent antibody levels were detected by both tests and appeared not to correlate with control of parasitaemia.

The role of IL-12 in experimental Trypanosoma cruzi infection

Host resistance to Trypanosoma cruzi infection in dependent on both natural and acquired immune responses. During the early acute phase of infection in mice, natural killer (NK) cell-derived IFN-gamma is involved in controlling intracellular parasite replication, mainly through the induction of nitric oxide biosynthesis by activate macrophages. We have shown that IL-12, a powerful inducer of IFN-gamma production by NK cells, is synthesized soon after trypomastigote-macrophage interaction. The role of IL-12 in the control of T. cruzi infection in vivo was determined by treating infected mice with anti-IL-12 monoclonal antibody (mAb) and analyzing both parasitemia and mortality during the acute phase of infection. The anti-IL-12 mAb-treated mice had higher levels of parasitemia and mortality compared to control mice. Also, treatment of infected mice with mAb spectific for IFN-gamma or TNF-alpha inhibited the protective effect of exogenous IL-12. On the other hand, TGF-beta and IL-10 produced by infected macrophages inhibited the induction and effects of IL-12. Therefore, while IL-12, TNF-alpha and IFN-gamma correlate with resistance to T. cruzi infection, TGF-beta and IL-10 promote susceptibility. These results provide support for a role of innate immunity in the control of T. cruzi infection. In addition to its protective role, IL-12 may also be involved in the modulation of T. cruzi-induced myocarditis, since treatment of infected mice with IL-12 or anti-IL-12 mAb leads to an enhanced or decreased inflammatory infiltrate in the heart, respectively. Understanding the role of the cytokine produced during the acute phase of T. cruzi infection and their involvement in protection and pathogenesis would be essential to devise new vaccines or therapies.

Cytokines in innate and acquired immunity to Trypanosoma cruzi infection

Reistance to Trypanosoma cruzi infections is critically dependent on cytokine-mediated activation of cell-mediated immune effector mechanisms. This review focuses on the role of IL-10, TNF-alpha, IFN-gamma and IL-12 in controlling T. cruzi replication by the innate and specific immune systems of the vertebrate host. A study performed on mice with disrupted recombinase-activating genes (RAG/KO), which lack T and B lymphocytes, revealed the importance of IL-12, IFN-gamma and TNF-alpha in the resistance against T. cruzi mediated by the innate immune system. In addition, data from experiments using IL-10 KO, RAG/KO and double RAG/IL-10 KO mice indicating an in vivo regulatory role of IL-10 in innate and T. cruzi-specific immunity are discussed.

Clearance-inducing antibodies are responsible for protection against the acute phase of Trypanosoma cruzi infection in mice

A study was conducted on mice infected with strains Y and CL of Trypanosoma cruzi. The ability of anti-Y and anti-CL sera to induce complement-mediated lysis, immune clearance and protection against the acute phase of the infection was studied using homologous anti-Y or anti-CL serum tested with the Y or CL strain, or heterologous anti-Y serum tested with the CL strain or anti-CL serum tested with the Y strain. Complement-mediated lysis was induced by both homologous and heterologous antisera but protection was afforded only by homologous antisera. Immune clearance was induced by homologous but not by heterologous antisera. Antisera with high clearance ability were able to confer protection whereas antisera with high lytic ability were not. These results show a high correlation between the antibody ability to induce clearance and to confer protection and suggest that clearance rather than lysis is responsible for protection against the acute phase of the infection. The mechanisms of antibody protection against the acute phase of the infection is discussed.

Experimental Trypanosoma rangeli infection in a mature model

Trypanosoma rangeli experimental murine infections were performed in order to study parasitemias and anti-parasite antibody levels. Three groups of mice were used: a) mice infected with metatrypomastigotes derived from infected bugs; b) mice which received four reinoculations of metatrypomastigotes and c) mice immunosuppressed with cyclophosphamide. The results showed that bloodstream parasites can be found from the first day post inoculation reaching a peak at day 5 or 7 and then start to decline. Parasites disappeared completely from the circulation after 20-25 days. However in the immunosuppressed group, parasites were found in blood up to 45 days post infection. The humoral immune response was monitored using an ELISA test and low levels of specific IgG and IgM unoglobulins were found. However the IgG titers were lower than the IgM. One could conclude that IgM was the predominant immunoglobulin isotype induced in a T. rangeli experimental infection because the highest titers were observed in the reinoculated group. IgM antibodies also showed the most prominent crossreactivities with T. cruzi antigens