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.

BackgroundAccording 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 FindingsParasitemia 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.SignificanceThis 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.

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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 murine 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 either monoclonal antibodies against L3T4, Thy 1.2, NK1.1, or with a polyclonal rabbit 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 parasitaemia 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 NK 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.

The aim of this study was to study the incidence of chronic renal dysfunction in patients with more than 5 yr of follow-up following liver transplantation and to evaluate the benefit of decreasing cyclosporine A (CsA) dose combined with mycophenolate mofetil (MMF) on renal function and immune response in these patients. Between 1988 and 1994, 60 children were transplanted, and 86% survived >5 yr post-liver transplantation. Fourteen patients developed chronic renal dysfunction secondary to CsA toxicity as evaluated by renal biopsy. In 11 patients CsA dose was decreased to 40-90 mg/ml target levels and MMF 600 mg/m(2) twice daily was added to the immunosuppressive regimen. Plasma creatinine decreased (from 1.0 +/- 0.03 to 0.8 +/- 0.03 ng/dl, p < 0.007), creatinine clearance increased (from 66.8 +/- 3.0 to 99.2 +/- 6.3 ml/min/1.73 m(2), p < 0.002) and microalbuminuria decreased (from 21.0 +/- 8.6 to 3.6 +/- 1.1 mg/24 h, p < 0.05) after 12 months of CsA combined with MMF therapy. During combined therapy the proliferative, cytolytic response and cytotoxic antibodies showed no significant changes, whereas CD4/CD8 ratio increased (from 1.2 +/- 0.2 to 1.4 +/- 0.1, p < 0.05). Tumor necrosis factor-alpha secretion increased (p < 0.005) during MMF therapy. The release of interleukin-10 was strikingly augmented under both immunosuppressive regimens, but the release of transforming growth factor-beta and interferon-gamma did not change. Our findings indicate that initiation of MMF combined with reduced doses of CsA allowed the recovery of renal function with minor changes in the immune response.