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Background: According to the Chagas congenital transmission guides, the diagnosis of infants, born to Trypanosoma cruzi infected mothers, relies on the detection of parasites by INP micromethod, and/or the persistence of T. cruzi specific antibody titers at 10-12 months of age., Methodology and Principal Findings: Parasitemia levels were quantified by PCR in T. cruzi-infected children, grouped according to the results of one-year follow-up diagnosis: A) Neonates that were diagnosed in the first month after delivery by microscopic blood examination (INP micromethod) (n = 19) had a median parasitemia of 1,700 Pe/mL (equivalent amounts of parasite DNA per mL); B) Infants that required a second parasitological diagnosis at six months of age (n = 10) showed a median parasitemia of around 20 Pe/mL and 500 Pe/mL at 1 and 6 months old, respectively, and C) babies with undetectable parasitemia by three blood microscopic observations but diagnosed by specific anti - T. cruzi serology at around 1 year old, (n = 22), exhibited a parasitemia of around 5 Pe/mL, 800 Pe/mL and 20 Pe/mL 1, 6 and 12 month after delivery, respectively. T. cruzi parasites were isolated by hemoculture from 19 congenitally infected children, 18 of which were genotypified as DTU TcV, (former lineage TcIId) and only one as TcI., Significance: This report is the first to quantify parasitemia levels in more than 50 children congenitally infected with T. cruzi, at three different diagnostic controls during one-year follow-up after delivery. Our results show that the parasite burden in some children (22 out of 51) is below the detection limit of the INP micromethod. As the current trypanocidal treatment proved to be very effective to cure T. cruzi - infected children, more sensitive parasitological methods should be developed to assure an early T. cruzi congenital diagnosis.

The relationship between parasite burden and vertical transmission of Trypanosoma cruzi was studied in pairs of chronically infected women and their children in a non-endemic area. Parasitemia was quantified by quantitative polymerase chain reaction (qPCR) in the peripheral blood amplifying a nuclear T. cruzi DNA and expressed as equivalent amounts of CL Brener parasites DNA per ml (eP/ml). Similar levels of parasitemia were found in non-transmitting pregnant women and in non-pregnant women: 1.8 ± 0.5 and 1.5 ± 0.7 eP/ml, respectively. In women pregnant with infected children parasitemia was 11.0 ± 2.7 eP/ml (n=20). In 12 of their neonates the infection was detected by microscopic observation of the parasites in peripheral blood in the 1(st) month of age. These children had variable levels of parasitemia (13,000 ± 7000 eP/ml), that were about 600-fold higher than that found in their mothers. To our knowledge, this is the first quantitative evaluation of parasitemia in these three groups of women and in their congenitally infected children. These parasite quantifications could be a basis to plan the control of mother-to-child transmission of T. cruzi., (Copyright © 2012 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved.)

Objective: The presence of autoantibodies with adrenergic and cholinergic activity, capable of triggering neurotransmitter receptor-mediated effects, has been associated with pathogenesis in T. cruzi-infected hosts. The goal of this study was to investigate the production of anti-M2 muscarinic receptor autoantibodies (Anti-M2R AAbs) as well as the IFN-γ profile in children at the early stage of Chagas disease, and to examine whether trypanocidal chemotherapy with benzonidazole (BZ) could modify both response patterns., Methods: This study comprised 30 T. cruzi-infected children (mean age: 13.8 years) and 19 uninfected controls (mean age: 12.7 years). Infected patients were treated with BZ and followed-up. Blood samples collected at diagnosis-T0, end of treatment-T1, and six months later-T2 were analysed by ELISA for detection of Anti-M2R AAbs and circulating levels of IFN-γ., Results: At T0, anti-M2R AAbs were demonstrated in 56.7% of T. cruzi-infected patients, whereas uninfected controls were 100% negative. The average age of Anti-M2R AAbs(+) patients was higher than that from negative population. Infected children also displayed significantly stronger serum IFN-γ responses than controls. Upon BZ treatment, a significant linear decreasing trend in Anti-M2R AAb reactivity was recorded throughout the follow-up, with 29.7-88.1% decrease at T2. IFN-γ circulating levels also declined by T2., Conclusion: Anti-M2R AAbs and IFN-γ raise early during chagasic infection in children and are downmodulated by BZ therapy. These findings reinforce the usefulness of early BZ treatment not only to eliminate the parasite but also to reduce potentially pathogenic immune responses.

Mother-to-child transmission of intracellular parasites could be related to the production of immunoregulatory cytokines. The levels of gamma interferon (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha) and lnterleukin (IL)-10 were evaluated during pregnancy in sera of women chronically infected with Trypanosoma cruzi that delivered infected or non-infected children. The levels of IL-10 increased in both, women only pregnant and only infected, compared to non-infected non-pregnant women. However, in pregnant women chronically infected with T. cruzi, IL-10 did not increase significantly, neither in the mothers of infected nor in the mothers of non-infected children. The levels of the inflammatory cytokine TNF-alpha were not affected in normal pregnancy but increased in the infected mothers of non-infected children. The levels of IFN-gamma did not increase in the groups studied, indicating that the production of this pro-inflammatory cytokine was controlled, even when the levels of IL-10 did not increase, as in pregnant women chronically infected with T. cruzi.

T and NK cells play a key role in resistance to Trypanosoma cruzi infections, mainly through IFN-gamma production. The expression of T and NK cells surface markers was studied in NWNA spleen cells of resistant C3H and susceptible BALB/c mice that release IFN-gamma in the early and late acute infection, respectively. In the progressively enlarged spleens, we found: (a) an increased percentage and number of NK blast cells as early as at 2 days post-infection (pi), (b) an enrichment of T and NK cells, in both the total and blast populations, during the late acute phase. At 17 days pi, there was also an accumulation of TCR- alphabeta+DX5+, NKT cells, mainly in resistant mice. At 21 days pi, the enrichment of NK cells ceased, while spleen cells and the T cell compartment continued their expansion. In the chronic stage, TCR-alphabeta+ blasts were expanded in both mouse strains, but NK blasts increased only in BALB/c that, unlike C3H mice, release IFN-gamma. As T and NK cell proliferation is not always associated to IFN-gamma release the experimental downregulation of their expansion to avoid tissue damage could be explored.

Gamma-interferon (IFN-gamma) production, the hallmark of the Th1 immune response, has been shown to play a central role in the resistance to Trypanosoma cruzi infections, in particular when produced in the very early acute infection. BALB/c mice infected with T. cruzi, Tulahuén strain, reach high parasitemias during the acute phase, and their spleen cells release IFN-gamma in the second week of the infection, while those of the resistant C3H strain produce the cytokine earlier, at 2 days post-infection (pi). We studied in the spleen cells supernatants of infected BALB/c and C3H mice, the spontaneous production of cytokines involved in the induction, interleukin (IL)-18 and IL-12 p70, as well as in the downregulation, IL-13 and IL-10, of the Th1 immune response. We found that, at 2 days pi, only C3H mice produced IL-18, while IL-12 p70 was detected in both mouse strains. Moreover, at this time pi splenocytes from BALB/c mice spontaneously produced high amounts of IL-13. At 14 days pi, despite the increased levels of IL-13 and IL-10 detected in C3H mice, they still showed high concentrations of IL-18 and IL-12 p70. In contrast, spleen cells from BALB/c mice did not secrete IL-18, IL-12 p70 and IL-13 at this time pi, but produced higher amounts of IL-10 than C3H mice. Non of these cytokines was found increased in the cell supernatants of chronically infected mice. The addition of lipopolysaccharide (LPS) or Concanavalin A (Con A) to the cell cultures did not enhance the production of IL-18 and IL-12 at the time points tested. On the other hand, at 21 days pi, when parasitemia peaked, an inhibition of both the LPS induced IL-10 release and the IL-13 production upon Con A stimulation was observed in C3H, but not in BALB/c mice. We did not find an increase of IL-18, IL-10, or IL-12 p70 in the serum of the infected mice, despite the high seric IL-12 p40 concentrations reached during the infection. The data show that the different kinetics of the production of these cytokines in the spleen of both mouse strains could have a key role in the in vivo regulation of IFN-gamma production. In these experimental models, early IFN-gamma release and thus resistance to T. cruzi infection, could be related to the combined effect of both IL-18 and IL-12p70 in the absence of IL-13.

Specific antibodies and the activation of phagocytic cells by IFN-gamma are the key elements of the immune response involved in protection of the T. cruzi infected host. The central role of the IFN-gamma in vivo seems to be the activation of the inducible nitric oxide synthetase of macrophages (iNOS) and the production of nitric oxide (NO degree) for the intracellular destruction of the parasite. Interleukin 12 (IL-12), the cytokine that stimulates NK cells for IFN-gamma production, seems to trigger the TH1 response in the acute phase. Other cell types, such as lymphocytes Thy-1+CD4-CD8-, CD4+ and CD8+, are also involved in IFN-gamma production. The down regulation of the TH1 response could in part depend on the decrease in the macrophage activation, as a result of the controlled parasite burden, and on the production of IL-10 and transforming growth factor beta (TGF-beta). The protective TH1 immune response seems to be also related to both the tissue damage and the alterations of the immune response observed during the infection. We studied the kinetics of both NK cell activity, and the production of IL-12 and/IFN-gamma by spleen cells, as well as the seric levels of these cytokines, in BALB/c and C3H mice infected with T. cruzi, Tulahuén strain. In the spleen, we found that the production of IL-12 and the NK cell activity increased in the very early acute infection, and that in C3H the effect was higher than in BALB/c mice. IFN-gamma increased in C3H at the same time, but in the BALB/c strain it increased later in the acute phase. The infection induced a very early increase in the seric levels of IL-12, that remained high throughout the acute phase, in both mouse strains. However, the levels of IFN-gamma in the serum increased a few days before the peak of parasitemia, reaching higher values, and earlier, in BALB/c than in C3H mice. Surprisingly, in the chronic infection IL-12 production remained high in both mouse strains, but IFN-gamma production was only observed in BALB/c mice. The immune response was predominantly TH1 in both mouse strains, in spite of the higher susceptibility of BALB/c compared to C3H. The early control of the parasite burden could be evaluated as the expression of the TH1 response in spleen cells, while the seric levels of IL-12 and IFN-gamma would be related to the induction of tissue damage. Our data indicate that the protective TH1 immune response has a different expression according to the host-parasite relationship, and that the factors controlling the response are of primary importance to determine the quali- and quantitative expression of IL-12/NK/IFN-gamma as well as their involvement in resistance and tissue damage.

The release of reactive oxygen intermediates (ROI), mediators of inflammatory reactions, was evaluated in murine Trypanosoma cruzi infection. In acutely infected BALB/c mice, spleen cells were stimulated, either with epimastigote or trypomastigote forms of the parasite, and the effect was enhanced by serum from infected mice. Only opsonized parasites triggered the release of ROI by normal mouse cells and this response was several times lower than in infected mice. This seems to indicate that cells from acutely infected mice reacted to T. cruzi and that neither parasites nor serum factors blocked the release of ROI. During the acute stage of the infection, both the parasitemia and the release of ROI by spleen cells were higher in BALB/c than in C3H mice (ROI generated in response to a phagocytic stimulation was 12 and 3 times the normal levels, respectively). In addition, in BALB/c mice infected with different numbers of parasites, the production of ROI was related to parasitemia. On the other hand, during the chronic stage of the infection, the inflammatory reaction in myocardium was greater in C3H than in BALB/c mice, and the increase in ROI production was 30% and 100% above the normal levels in BALB/c and C3H mice, respectively. This suggests that the increased ROI production paralleled the parasite burden in the acute phase, and could be related to inflammatory processes after the control of the parasitemia.

The acute stage of Trypanosoma cruzi infections related to high parasitemia is characterized by the presence of inflammatory infiltrates in several tissues, including the heart and squeletal muscle, as well as by an increased production of inflammatory mediators, such as gamma-interferon (IFN-gamma), tumor necrosis factor (TNF), interleukin-1 (IL-1) and oxygen and nitrogen reactive intermediates. The activation of phagocytic cells seems to be closely related to both the inflammatory process and host resistance to the infection. Herein, the inflammatory mediators produced in vivo and their relationship with the tissue damage and TH1 immune response are reviewed.

Effector mechanisms of resistance exerted by T cells from BALB/c mice chronically infected with Trypanosoma cruzi, Tulahuén strain, were studied. Spleen cells from chronically infected mice (Chro-SC) prestimulated with heat-killed trypomastigotes (HKT) and/or IL-2 destroyed PHA-labeled p-815 mastocytoma cells, HKT-pulsed macrophages, and normal peritoneal macrophages. However, HKT-stimulated Chro-SC did not affect the infectivity of free bloodstream forms of the parasite. Upon HKT stimulation, Chro-SC or their culture supernatant activated peritoneal macrophages for the destruction of intracellular amastigotes. The effect was abolished after Thy 1.2+ cell depletion. The addition of Cyclosporin A (CyA), which blocks T-cell activation, during HKT-stimulation of Chro-SC, diminished their ability to activate the trypanocidal activity of macrophages. CyA also inhibited the production of both macrophage-activating factors and interferon-gamma by HKT-stimulated Chro-SC. CyA administration to recipients of nylon-wool nonadherent spleen cells from chronically infected mice inhibited their adoptively acquired resistance against T. cruzi, suggesting that the conferred resistance depended on the effect of specifically activated cells. When administered during the chronic stage of the infection, CyA abrogated the antigen-specific delayed type hypersensitivity response but increased the levels of anti-T. cruzi IgG antibodies. Neither parasitemia, tissular parasitism in myocardium or skeletal muscle, nor mortality were detected after CyA treatment, suggesting the presence of a CyA nonsensitive mechanism(s) in the control of T. cruzi during the chronic phase of the infection.

This study has been designed to find an easy method to evaluate the motor unit alterations induced during experimental T. cruzi infections. Different mouse strains infected with three strains of T. cruzi were used to perform conventional needle electromyography, in one of the lower limb hamstring muscles; amplitude, duration and number of phases of single motor unit potentials were measured. The following parasite strain to mouse strain relationship was investigated, in mice inoculated intraperitoneally with bloodstream forms of T. cruzi: Tulahuen and C3H/HeN, C57Bl, Balb/c, Swiss; CA-I and C3H/HeN, Rockland, NIH; RA and C3H/HeN, Rockland. T. cruzi-induced denervating alterations were found in both C3H/HeN and C57Bl mice infected with the Tulahuen strain, as well as in C3H/HeN mice inoculated with the CA-I strain. Moreover, CA-I trypomastigotes could produce primary muscle changes in C3H/HeN and NIH mice. The technique employed in this investigation proved to be an easy and adequate way to detect changes within the motor unit during T. cruzi infection in mice.

The temperature-dependence of some processes involved in the killing of sensitized T. cruzi epimastigotes by human polymorphonuclear leukocytes (PMN) was determined. The rate of the reactions was related to the temperature of incubation according to the Arrhenius equation and the apparent energies of activation (Ea) were calculated. The Ea values separated these complex reactions into two groups: one with Ea of about 10 kcal/mol for the phagocytosis of the parasites and the release of lysosomal enzymes by PMN, and the other with Ea of about 22 kcal/mol for the cytotoxicity against sensitized T. cruzi, the rate of oxygen consumption by PMN, and the lysis of the parasites with added hydrogen peroxide.

The humoral and cellular immune responses were studied in mice immunized with flagellar fraction (F), F plus Bordetella pertussis as adjuvant (F-Bp), and microsomal (Mc) subcellular fractions from the epimastigote forms of Trypanosoma cruzi. The immune response was studied before and after the challenge with 50 bloodstream forms of T. cruzi, Tulahuén strain. The immunization with F-Bp, but not with Mc or F and Bp separately, protected mice, in terms of parasitemia and mortality, from the challenge with the parasite. Before the challenge, levels of specific antibodies in mice immunized with F-Bp were higher than in mice immunized with F or Mc. Antibody levels 17 days after the infection were similar in the three groups of mice while nonimmunized mice reached lower levels. Early during the infection nonimmunized infected mice lacked delayed-type hypersensitivity (DTH) responses to parasite antigens and to concanavalin A (Con A). Mice immunized with F-Bp, however, presented positive DTH responses to parasite antigens and Con A both, before and after the challenge with T. cruzi. DTH reaction was transferred with spleen cells. Mice immunized with Mc behaved similarly to infected nonimmunized animals in their reactivity to parasite antigens. These results indicated striking differences between protected and nonprotected mice in humoral and cellular immune responses during experimental T. cruzi infection.

This study provides biochemical and electron spin resonance spectroscopic evidence that contract of human polymorphonuclear leukocytes with antibody-coated Trypanosoma cruzi triggers the respiratory burst. Oxygen consumption, superoxide anion and hydrogen peroxide release were stimulated under conditions of polymorphonuclear leukocyte-mediated killing. This stimulation did not occur under non-killing conditions when antibody was omitted. A common mechanism of cytotoxicity of human polymorphonuclear leukocytes against different T. cruzi forms is suggested by the triggering of the respiratory burst by antibody-coated epimastigotes and trypomastigotes.

The release of beta-glucuronidase and lysozyme from human polymorphonuclear leukocytes (PMN) engaged in phagocytosis and lysis of Trypanosoma cruzi epimastigotes was studied in the presence or absence of chagasic serum. Lysosomal enzyme release was enhanced when parasites were sensitized with serum from a chronic Chagas' patient, increased up to 3 hr of incubation at 28 C, and depended on the PMN:parasite ratio. The release of lysosomal enzymes was determined by the presence of 2 mM cyanide, 2 microM azide, 3 mM amobarbital, and 1 mM phenylbutazone. These drugs inhibited the killing of sensitized T. cruzi by interfering with the oxidative microbicidal mechanisms of PMN without affecting the uptake of the parasites. Lysosomal enzyme release occurred in the presence of cyanide and azide, indicating that in these cases the enzymatic release was unrelated to the killing of the parasites. Amobarbital and phenylbutazone, which stabilize PMN membranes, inhibited the release of beta-glucuronidase and lysozyme by PMN. The addition of 10 micrograms/ml of cytochalasin B inhibited the phagocytosis and killing of sensitized T. cruzi by PMN but increased the enzymatic release by effector cells. Since cytochalasin B did not affect the close contact between PMN and parasites, it appears that the enzymes released to the extracellular milieu were not toxic to noningested parasites. Furthermore, the lysosomal enzymes did not lyse bystander unsensitized parasites. Therefore, the release of lysosomal enzymes during the interaction of T. cruzi epimastigotes and PMN seems to be related to the triggering event of the phagocytic process and does not bear a cause-effect relationship with parasite death.

Human peripheral mononuclear cells were cytotoxic to antibody-sensitized Trypanosoma cruzi epimastigotes. The cytotoxic effect depended on the concentration of effector cells and antiserum, and was progressive until 17 hr of incubation at 28 degrees C. After 3 hr of incubation the highest specific activity was achieved at a 50:1 effector to target cell ratio. A nonspecific cytotoxic effect in the absence of antiserum was observed at a 100:1 parasite to cell ratio or after 17 hr of incubation. When the human mononuclear cell population was depleted of adherent cells by Sephadex G-10 filtration or adsorption to glass, the cytotoxic effect was greatly reduced. Similar results were obtained using mouse spleen cells, indicating that only the adherent cells were cytotoxic to sensitized T. cruzi in both systems. When human mononuclear cells were incubated with amobarbital, cyanide, azide, or aminotriazole, an inhibition of cytotoxicity against sensitized T. cruzi was observed, suggesting that oxygen reduction products and myeloperoxidase were involved in the destruction of sensitized T. cruzi epimastigotes by normal human mononuclear cells.

Infective forms of Trypanosoma cruzi were used to evaluate the complement-mediated lysis (CoML) of the parasites in the presence of anti-T. cruzi sera. Parasites released to the supernatant from infected Vero cell monolayers were used. Cultures of 1-3 x 10(6) parasites/ml were incubated for 24 h in the presence of 10 microCi/ml of 3H-uridine. Under these conditions 10(5) parasites used for each determination incorporated about 9600 dpm of the radioactive material. The release of tritium from labelled parasites after incubation with antiserum and complement correlated with the percentage of lysed parasites evaluated by optical microscopy. Normal sera from humans, a guinea pig, a rabbit, and mice were tested as complement sources. Only human sera were suitable for the evaluation of CoML in the presence of antisera, and the levels of lysis attained depended on the serum donor.

Normal human polymorphonuclear leukocytes (PMN) are cytotoxic to T. cruzi epimastigotes sensitized with specific antiserum (T. cruzi + Ab). The damage follows an early phagocytic event, suggesting the intracellular destruction of the parasites. We have studied the characteristics of the killing using metabolic inhibitors of the effector cells. Oxygen consumption by PMN with unsensitized parasites was similar to the uptake by resting cells, but increased two- to fourfold when T. cruzi + Ab was used. This increase in O2 consumption, associated with phagocytosis of T. cruzi + Ab was not sensitive to 2 mM cyanide nor 100 microM azide. Addition of T. cruzi + Ab to human PMN also stimulated H2O2 production. When PMN were incubated with phenylbutazone, cyanide or azide, an inhibition of cytotoxicity against sensitized T. cruzi was observed. Under the same experimental conditions phagocytosis was unaffected. These results indicate that active oxygen reduction products and myeloperoxidase are involved in the destruction of sensitized, T. cruzi epimastigotes by normal PMN.

Subcellular fractions of T. cruzi epimastigotes (Epi) were studied for their capability to induce protective or aggressive effects in animals. The flagellar fraction (F) showed the best immunoprotective properties without tissular aggression. Monoclonal antibodies were raised against F. Two of them, FCH-F8-1 and 4, were able to neutralize the infectivity of bloodstream forms, to mediate lysis by complement of cell culture derived[trypomastigotes (Tripo) and to recognize the surface of Tripo and Epi. FCH-F8-1 reacted with a 85 kDa protein from Tripo (assayed by immunoprecipitation) and with peptides of 43 kDa on Epi and Tripo (tested by immunoblotting). FCH-F8-4 recognized several proteins ranging from 50 to 150 kDa on Epi and two molecules of 15 and 48 kDa on Tripo. Mice immunized with antigens purified by affinity chromatography by using FCH-F8-4 were protected against the infection. Several recombinant clones were detected on a cDNA lambda gt11 expression library constructed from T. cruzi Epi (Tulahuén strain): three with FCH-F8-4 and two with FCH-F8-1. One clone recognized by each monoclonal antibody was studied gamma (FCH-F8-1) 1 and gamma (FCH-F8-4) 1. Both inserts were of 150 base pairs each; they detected a 3.5 and 5.0 kilobases Epi mRNA, respectively. Both inserts were sequenced, and the amino acid sequences were inferred. gamma (FCH-F8-4) 1 codified for a 19 aa peptide, PAFLGCSSRFSGSFSGVEP, and gamma (FCH-F8-1) 1 for a 29 aa peptide EFLERGRISCORHSYTSYTSCSDEHNVTPFC. The whole 19 aa peptide was synthesized. This peptide (SP4) inhibited the ELISA reactivity against the parasite of chronically infected and F immunized mouse sera.(ABSTRACT TRUNCATED AT 250 WORDS)

We have studied the relationship between phagocytosis and cytotoxicity of human polymorphonuclear leucocytes (PMN) to sensitized Trypanosoma cruzi. Assays were done simultaneously using [3H]-uridine labelled epimastigotes as target cells. Phagocytosis was evaluated by the uptake and cytotoxicity by the release of parasite associated [3H]-uridine. Both reactions reached maximum levels at the same effector- to target-cell ratio and antibody concentration. Uptake of epimastigotes by PMN was highest at 30 min and intracellular disruption and release of parasite debris took place later. In conditions that precluded repeated uptake of sensitized radiolabelled T. cruzi, the release profile of [3H]-uridine from PMN that contained intracellular parasites was similar to that of the standard cytotoxic assay. However, as the ingestion phase was separated from the release step, no lag in the onset of the reaction was observed. Although we cannot rule out extracellular killing, the results of this study demonstrate that the bulk of damaged T. cruzi epimastigotes had been previously internalized by the PMN.

Background: According to the Chagas congenital transmission guides, the diagnosis of infants, born to Trypanosoma cruzi infected mothers, relies on the detection of parasites by INP micromethod, and/or the persistence of T. cruzi specific antibody titers at 10–12 months of age. Methodology and Principal Findings: Parasitemia levels were quantified by PCR in T. cruzi-infected children, grouped according to the results of one-year follow-up diagnosis: A) Neonates that were diagnosed in the first month after delivery by microscopic blood examination (INP micromethod) (n = 19) had a median parasitemia of 1,700 Pe/mL (equivalent amounts of parasite DNA per mL); B) Infants that required a second parasitological diagnosis at six months of age (n = 10) showed a median parasitemia of around 20 Pe/mL and 500 Pe/mL at 1 and 6 months old, respectively, and C) babies with undetectable parasitemia by three blood microscopic observations but diagnosed by specific anti - T. cruzi serology at around 1 year old, (n = 22), exhibited a parasitemia of around 5 Pe/mL, 800 Pe/mL and 20 Pe/mL 1, 6 and 12 month after delivery, respectively. T. cruzi parasites were isolated by hemoculture from 19 congenitally infected children, 18 of which were genotypified as DTU TcV, (former lineage TcIId) and only one as TcI. Significance: This report is the first to quantify parasitemia levels in more than 50 children congenitally infected with T. cruzi, at three different diagnostic controls during one-year follow-up after delivery. Our results show that the parasite burden in some children (22 out of 51) is below the detection limit of the INP micromethod. As the current trypanocidal treatment proved to be very effective to cure T. cruzi - infected children, more sensitive parasitological methods should be developed to assure an early T. cruzi congenital diagnosis. [ABSTRACT FROM AUTHOR]

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This article discusses various issues related to a study whose aim was to determine the effect of pregnancy on resistance to experimental Trypanosoma cruzi infection. Trypanosoma cruzi is the protozoan parasite that causes Chagas disease. Pregnancy has been associated with a suppression of the immune response, attributed to both maternal and foetal factors such as the production of progesterone and &agr;-foetoprotein, as well as the involution of the cortical zone of the maternal thymus. Although this suppression helps to protect the foetus from the potential damage of the maternal response to allo-antigens, it is not clear if this immunodepression is restricted to foetal allo-antigens or also generally reduces the maternal response to pathogens during pregnancy.

T rypanosoma cruzi induces inflammatory reactions in several tissues. The production of prostaglandin F 2α , 6-keto-prostaglandin F 1α and thromboxane B 2 , known to regulate the immune response and to participate in inflammatory reactions, was studied in mice experimentally infected with T. cruzi . The generation of nitric oxide (NO), which could be regulated by cyclooxygenase metabolites, was also evaluated. In the acute infection the extension of inflammatory infiltrates in skeletal muscle as well as the circulating levels of cyclooxygenase metabolites and NO were higher in resistant C3H mice than in susceptible BALB/c mice. In addition, the spontaneous release of NO by spleen cells increased earlier in the C3H mouse strain. In the chronic infections, the tissue inflammatory reaction was still prominent in both groups of mice, but a moderate increase of thromboxane B 2 concentration and in NO released by spleen cells was observed only in C3H mice. This comparative study shows that these mediators could be mainly related to protective mechanisms in the acute phase, but seem not to be involved in its maintenance in the chronic T. cruzi infections. [ABSTRACT FROM AUTHOR]

T lymphocytes provide a major line of defence against many protozoan parasites. The aim of this work was to determine the role of T-cell helper/inducer subset (T h/i) in the resistance to Trypanosoma cruzi in a routine model. The importance of natural killer (NK) cells in the resistance to the parasite was also evaluated. BALB/c and C57BL/6 mice were injected with or with a polyclonal rabbit either monoclonal antibodies against L3T4, Thy 1.2, NK1.1, antiserum against NK cells (anti-asialo GM-1). The effect of in vivo administration of these antibodies was tested in separate functional assays. After antibody treatment, mice were infected with a low dose of T. cruzi in the bloodstream form. Mice depleted of, or reduced in T, T h/i, or NK cell activity all developed higher parasitacmia and had higher mortality than their control counterparts. Mice injected with anti-L3T4 monoclonal antibodies were unable to generate a specific antibody response to the parasite. Treatment of mice with alpha/beta interferon, which is known to boost N K cell activity, resulted in an enhanced resistance to the parasite. Our data indicate that T h/i cells as well as NK cells, are of vital importance in controlling parasitaemia and reducing mortality in T. cruzi-infected mice. Finally, we also demonstrate that the production of antibodies specific for T. cruzi is strictly T helper cell-dependent. [ABSTRACT FROM AUTHOR]