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Print version ISSN 0036-4665
Rev. Inst. Med. trop. S. Paulo vol.41 n.5 São Paulo Sept./Oct. 1999
The congenital transmission of Chagas disease was evaluated in 57 pregnant women with Chagas disease and their 58 offspring. The patients were selected from three Health Institutions in São Paulo City. The maternal clinical forms of Chagas disease were: indeterminate (47.4%), cardiac (43.8%) and digestive (8.8%); 55 were born in endemic areas and two in São Paulo City. The transmission of Chagas disease at fetal level was confirmed in three (5.17%) of the 58 cases studied and one probably case of congenital Chagas disease. Two infected infants were born to chagasic women with HIV infection and were diagnosed by parasitolological assays (microhematocrit, quantitative buffy coat-QBC or artificial xenodiagnosis). In both cases the placenta revealed T. cruzi and HIV p24 antigens detected by immunohistochemistry. In one case, a 14-week old abortus, the diagnosis of congenital T. cruzi infection was confirmed by immunohistochemistry. The other probable infection, a 30-week old stillborn, the parasites were found in the placenta and umbilical cord.
The Western blot method using trypomastigote excreted/secreted antigens of T. cruzi (TESA) was positive for IgG antibodies in 54/55 newborns and for IgM in 1/55 newborns. One of the two newborns with circulating parasites had no detectable IgG or IgM antibodies.
The assessment of IgG antibodies in the sera of pregnant women and their newborns was performed by ELISA using two different T. cruzi antigens: an alkaline extract of epimastigotes (EAE) and trypomastigote excreted/secreted antigens (TESA). The analysis showed a linear correlation between maternal and newborn IgG antibody titers at birth.
KEYWORDS: Trypanosoma cruzi; Chagas disease; Congenital Chagas disease; Chagas disease and HIV; Immunohistochemistry for parasites; TESA.
The congenital transmission of Trypanosoma cruzi has been described by several authors3,7,12. Its frequency varies according to the area studied and methodology employed. In 1960, LISBOA18 described for the first time the presence of amastigote forms of T. cruzi in a stillborn and its placenta, confirming infection through the transplacental route. In studies conducted in the sixties and seventies, anatomopathological examination of material collected from abortions and stillborn fetuses showed that death occurred because of chagasic infection4,5,7. Since 1980, prospective work has shown that different clinical forms of congenital Chagas disease can be identified with the aid of different methods of diagnosis such as parasitological and serological tests and anatomopathological studies7,22,23. Congenital Chagas disease is manifested in several ways: intra-uterine death during any fetal phase, prematurity, hepatosplenomegaly, fever and/or cardiac problems, nervous and digestive manifestations. The newborns may be at birth asymptomatic5,12. There are regional differences in the incidence rates of congenital chagasic infection, which vary from 1.1 % to 18.5% when parasitological methods are applied for diagnosis2,3,6,22,24,26. The risk factors for recurrent congenital transmission by chagasic pregnant women have not been clearly defined, but may be influenced by the strains of T. cruzi or the level of parasitemia8. The presence of T. cruzi at birth substantiates the diagnosis of congenital Chagas disease. The detection of IgM antibodies by serological methods is possible with the use of a specific acute phase protein (SAPA) in Western blotting32, or SAPA recombinant proteins19, but these antibodies are not always found at birth in spite of the presence of circulating T. cruzi 3,6,12,19.
The main objective of this study was to investigate the incidence of congenital Chagas disease in three institutions specialized in the care of high risk pregnant women in São Paulo City, Brazil.
MATERIAL AND METHODS
Fifty seven pregnant women and their 58 newborns were chosen from three high risk obstetric clinics in São Paulo City: 25 patients from the University Hospital, Faculty of Medicine, Discipline of Obstetrics; 19 from the Maternity Hospital Leonor Mendes de Barros, and 13 from the Dante Pazzanese Institute of Cardiology (Cardiologic and Obstetric Sectors). Forty-two pregnant women had a previous diagnosis of Chagas disease and 15 had been diagnosed during prenatal examination. Serological tests were negative for syphilis but two were positive for HIV (2/36). Fifty-five patients were from endemic areas for Chagas disease, and two where born in São Paulo City (the daughter of a chagasic woman and a woman submitted to blood transfusion). Fifty-seven pregnant women were classified in indeterminate (47.4%, n=27), digestive (8.8%, n=5) and cardiac forms (43.8%, n=25) (according to clinical and laboratory evaluation, and electrocardiogram data). Childbirth occurred by vaginal delivery in 49.1% (n=28), and by cesarean section in 47.4% (n=27); spontaneous abortion occurred in 3.5% (n=2). The average age of the pregnant women was 32 years (21 to 44). The newborn data recorded at birth were: classification of age (Capurro), weight, 1st and 5th minute APGAR scores and data of physical examination. Infants born to these infected women were submitted to clinical, parasitological and serological examinations at birth. The anatomopathological examination was done in material collected from abortions and stillborns.
Parasitemia was determined in the 54 newborns. The parasitological tests were microhematocrit25, quantitative buffy coat (QBC)1 and artificial xenodiagnosis. The microhematocrit and QBC were also determined for the 46 pregnant women. Artificial xenodiagnosis was performed using 1 to 3 ml of venous blood and sometimes with cord blood collected with anticoagulant (heparin or EDTA). The collected blood was placed in a container covered with transparent PVC film (Magipack ®), heated to 37 °C, and offered as a meal to 20 3rd and 4th instar nymphs of Triatoma infestans for 45 minutes. The presence of T. cruzi was determined in the vectors feces 30 and 60 days after the blood meal.
Enzyme-linked-immunosorbent-assay (ELISA) was performed using 2 different antigens from T. cruzi: i) trypomastigote excreted/secreted antigens (TESA)32 , and ii) epimastigote alkaline extract (EAE)32,33. The ELISAs were processed as described33. The results were expressed as OD 492 nm (OD492). Samples from the pregnant women and their offspring were recorded as positive or negative in relation to the cutoff value. The confirmatory diagnosis of Chagas disease was performed by Western blot using TESA as antigens (TESA-blot), processed as previously described32. The results of the search for IgG and IgM anti-T. cruzi antibodies were defined as positive by the naked-eye observation of bands.
Histological and immunohistochemistry methods
Histological analysis was performed in 12 placentas, in two autopsies of stillborns and in two umbilical cord. Formaldehyde-fixed paraffin- embedded sections were stained with hematoxylin-eosin (HE) and also examined for detection of T. cruzi antigen by immunohistochemistry (IH)11,28. Immunohistochemical analysis for HIV p24 antigen (M 857/DAKO) was also performed in sections of placentas of two newborns, and one autopsy case of a dead newborn all from HIV-positive mothers.
The 58 offspring born to 57 chagasic pregnant women were represented by 54 newborns, with five neonatal deaths, two stillborns and two abortions (Fig. 1).
The average weight of the 54 newborns was 3 140 g. Weight adjusted for gestational age was appropriate in 83.3% of cases (n=45) but 13% (n=7) were small-for-gestational-age and only 3.7% (n=2) were large-for-gestational-age; 90.7% (n=49) of the deliveries were at term, 7.4% (n=4) pre-term and 1.9% (n=1) post-term. Low APGAR score at the first minute was observed in 11.3% (6/53) of the newborns, but two newborns recovered vitality by the 5th minute.
Among the 54 newborns, 49 were discharged from the hospital without abnormalities; 13 had physiological jaundice and five presented anomalies (one CIV and four minor anomalies). Five died within the perinatal period: two from Chagas disease and three from unrelated causes (Fig 1).
Two newborns congenitally infected were born from women co-infected with HIV (Tables 1 and 2). These mothers showed anti-T. cruzi IgM antibodies by TESA-blot and two were positive by xenodiagnosis and one by QBC. They also presented respectively 185 and 406 CD4/mm3. The mother of case 1 had received antiretroviral therapy (zidovudine, 200 mg/tid), from the second trimester of pregnancy to the 30th week of gestation when the HIV viral load was 35,600 copies/ml. Other details are summarized in Table 2.
Case 1 newborn died, during the neonatal period, with 10 hours of life, and autopsy was not performed. The infant had a third trimester placenta showing no inflammatory response or amastigotes forms by HE. T. cruzi antigen was detected in the decidua, villus stroma, cytotrophoblast, membranes and umbilical cord. The congenital transmission of HIV could not be proved in this case despite the presence of the p24 HIV antigen in the placenta membrane. The principal aspects of anatomopathological examination and others details are summarized in Table 1.
Case 2 newborn died 30 days after birth despite the introduction of benznidazole treatment (20 mg/kg/day). The autopsy findings showed bilateral pulmonary infarction, hepatosplenomegaly, digestive bleeding, and jaundice. Histology of the heart showed multifocal interstitial lymphocytic infiltration and necrosis of myocardial fibers. In the liver diffuse hypertrophy of Kupffer cells, intralobular cholesthasis and hepatocytic steatosis and inflammatory infiltration in portal spaces were observed. ntact T. cruzi amastigote forms were not detected by IH but T. cruzi antigen was present in myocardial fibers and Kupffer cells. Histology showed a third trimester placenta with chronic villitis, endarteritis, amastigotes forms in villus stroma and Hofbauer cell. T. cruzi antigen delineate amastigotes forms and antigen particles were present in villus stroma and Hofbauer cell. HIV p24 antigen was positive by IH in the villus and membrane of placenta, but the congenital transmission of HIV could not be proved also in this case.
Anatomopathological study was not performed in the stillborn (case 3), whose placenta presented intact T. cruzi amastigotes in the decidua, syncytiotrophoblast, Hofbauer cells and in the stroma, and T. cruzi antigen was found in the Wharton jelly of umbilical cord (Table 1).
In case 4, a 14 week-old macerated fetus, in spite of autolysis, T. cruzi antigens were detected by IH in the central nervous system.
The HE/IH examinations were not done in one abortus and in one 38 week-old stillborn twin (Figure 1). The other twin, a newborn showed no evidence of placental infection. The other nine placentas do not showed amastigote forms and T. cruzi antigen by the histological and IH studies.
Specific anti-T. cruzi IgG antibodies were found in 54/55 newborns by ELISA and TESA-blot. The IgM antibodies were detected only in case 1 (1/55) by TESA-blot (Table 1). Despite high parasitemia, case 2 presented no anti-T. cruzi IgG or IgM detectable in the serum. The surviving twin presented decreasing anti-T. cruzi IgG titers during follow-up, until he reached negative results after 6 months, demonstrating absence of congenital infection.
The concordance in anti-T. cruzi IgG levels in mother and newborn sera was almost perfect in the pairs tested. Only one newborn presented negative results, but the usual maternal antibody levels were present in infants serum. Serological patterns of specific anti-T. cruzi antibodies were tested by correlation between EAE and TESA, by ELISA (Fig.2). TESA-specific antibodies presented a higher correlation between maternal and newborn IgG antibodies, with r2=0.386 (p<0.0001), compared with the low level correlation of r2=0.178 (p=0.0067) found with EAE. These data suggest that most all of the maternal antibodies could be transferred by the placenta to the newborn, since only one case showed IgM anti-T.cruzi production, specific for a newborn response.
Congenital transmission of Chagas disease occurred in 5.17% of our patients series (3/58), plus one probable case. The parasitological method detected T. cruzi in two of 54 newborns, and the other cases were diagnosed by histological and immunohistochemistry methods.
The transplacentary transmission of T. cruzi has been shown in several stages of pregnancy5,8,12, with risk of T. cruzi transmission during the successive pregnancies5,8 of chagasic mothers.
Parasitological methods in general are the diagnostic tests of choice in acute congenital Chagas disease6,7,12, but xenodiagnosis is not easily performed due to the need for laboratory triatomines and to the long time needed to obtain the results7. The microhematocrit and QBC methods proved to be useful in these situations, since two of 54 newborns were positive by these methods.
The serological and parasitological tests concomitantly applied to newborns can be of help for the diagnosis of congenital Chagas disease12,15,26,27,32. In some cases IgG or IgM antibody detection is not possible, as observed in case 2 (Table 1). Some hypotheses can be formulated to explain this fact. According to GRILL et al.15, fetal infection can occur at any gestational age and the fetus at birth can be in the chronic phase. More recently, Lorca et al.19 found IgM antibodies at birth in 8/12 newborns with congenital Chagas disease and only after 1 to 2 months of life was possible to detect IgM antibodies in all children. The same authors explained this fact by the hypothesis of fetal infection in a late phase of the gestation, delaying the detection of IgM antibodies at birth. These hypotheses cannot explain the aspects found in case 2, which showed none of the Ig classes in spite of a marked parasitism. Some authors showed that IgG and IgM anti-T. cruzi antibodies could be adsorbed on the circulating bloodstream forms14.
In two of the present cases, the parasitological assays proved to be decisive for the diagnosis of newborn infection (Table 1)6,13,24,31,32.
Our study showed by ELISA differences in the correlation between maternal IgG and newborn antibody titers at birth, depending on the T. cruzi antigens used (Fig. 2).
The frequent reports showing T. cruzi forms in the placenta and umbilical cord in cases of congenital Chagas disease2,7 has led to the proposal of a correlation between congenital infection and presence of T. cruzi in these materials. Our data showed amastigote forms and T. cruzi fractions in the placenta and umbilical cord in case 3 (Table 1), supporting this hypothesis, since histological analysis of material from this stillborn was not possible.
IH is the method of choice for the detection of T. cruzi in tissues, since the amastigote forms can be confused with Toxoplasma gondii and Histoplasma capsulatum7. As observed in the present study, IH is very useful when the inflammatory response is not seen in the placenta as observed in case 1 and when the fetus is macerated7,16,17.
Congenital T. cruzi transmission at fetal level was confirmed in three cases, and in one case transmission was documented only at placental level.
The level of circulating T. cruzi parasites has been already mentioned as a possible factor for congenital Chagas disease transmission8. The presence of anti-T. cruzi IgM antibodies during pregnancy as observed in two HIV positive mothers indicates of Chagas disease reactivation. In urban centers9, heterosexual contamination with HIV virus is frequent, and the chances of pregnant women having both infections is high. In these cases the number of circulating T. cruzi could be increased29.
These results suggest the necessity of follow up of chagasic pregnant women coinfected with HIV, that presents high risk of T.cruzi transmission, and perinatal morbidity as previously reported12,13.
In spite of the presence of p24 HIV antigen in two placentas (cases 1 and 2), congenital HIV transmission was not investigated in our study, but previous data have shown that presence of HIV antigens in the placenta do not necessarily indicates fetal infection10,20,21,30.
The use of several parasitological, histopathological and immunohistochemical methods for the diagnosis of congenital Chagas disease increases the possibility of diagnosis, since specific IgM antibodies are not always present in the infected newborn at birth.
Doença de Chagas congênita em três instituições de saúde da cidade de São Paulo, Brasil
A transmissão congênita da doença de Chagas continua a ser um problema no Brasil. Em um estudo com 58 recém-nascidos, de 57 mães com a forma crônica da doença de Chagas, selecionadas em três Instituições de Saúde da Cidade de São Paulo, a transmissão congênita foi demonstrada em 5,17% (3/58) dos casos, com um provável caso confirmado somente pelo achado de antígenos do T. cruzi na placenta e cordão umbilical. Os testes parasitológicos (microhematócrito, quantitative buffy coat-QBC ou xenodiagnóstico artificial) foram capazes de diagnosticar dois casos congênitos de infecção pelo T. cruzi, nascidos de mulheres chagásicas com infecção pelo HIV. A imunohistoquímica efetuada nestas duas placentas foi capaz de identificar formas amastigotas e antígenos do T. cruzi. A infecção congênita foi confirmada a nível placentário em outros dois casos, e a nível fetal em um destes casos por imunohistoquímica.
O Immunoblotting utilizando antígenos excretados/secretados de formas tripomastigotas do T. cruzi (TESA-blot), detectou anticorpos IgG em 54/55 dos casos e IgM em 1/55. Nos dois casos congênitos um apresentou anticorpos IgG e IgM o no outro não foram detectados anticorpos IgG ou IgM anti T. cruzi, apesar do achado de parasitas circulantes.
This work was supported by grants from FAPESP, CNPq and LIM-49-FMUSP. We wish to thank the following persons for their help: M. Zugaib, S. Kahhale and M.R.F.L. Bortolotto; C.R. Leone; M.H. Lopes, M.A. Shikanai-Yasuda and A.A.C. Segurado, HC-FMUSP; Dr V. Tadini, C. Mariani, T. Oliveira and S. Daré from Hospital-Maternidade Leonor Mendes de Barros; J. Andrade, M.G.R. Champi and A. Franchi Jr, Setor de Cardiopatia e Gravidez, Instituto Dante Pazzanese de Cardiologia; H. Franco Jr; A.O.D. Fernandez, C.R.M. Casadei, F.L. Carignani; N. Kesper Jr, and M.S. Santos from Instituto de Medicina Tropical FMUSP.
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(1) Post-graduate student, Departamento de Doenças-Infecciosas e Parasitárias da Faculdade de Medicina da USP, São Paulo, SP, Brasil
(2) Laboratório de Parasitologia do Instituto de Medicina Tropical de São Paulo-USP, São Paulo, SP, Brasil
(3) Departamento de Patologia da Faculdade de Medicina da USP, São Paulo, SP, Brasil
(4) Laboratório de Protozoologia do Instituto de Medicina Tropical de São Paulo-USP, São Paulo, SP, Brasil
Correspondence to: Eufrosina Setsu Umezawa; Instituto de Medicina Tropical de São Paulo da FMUSP, Av. Dr Enéas de Carvalho Aguiar 470, 05403-000 São Paulo, S.P., Brasil, Fone 55 (11) 3066 7017. E-mail: firstname.lastname@example.org
Received: 12 May 1998
Accepted: 18 October 1999