RESUMO
Background: Congenital Trypanosoma cruzi infection accounts for an estimated 22% of new cases of Chagas disease in Latin America. However, neonatal diagnosis is challenging, as 9-month follow-up for immunoglobulin G testing is poor, quantitative polymerase chain reaction (qPCR) analysis is not routinely performed, and the micromethod misses ≥40% of congenital infections. Methods: Biorepository samples from new mothers and their infants from Piura, Peru, (an area of nonendemicity), and Santa Cruz, Bolivia (an area of endemicity) were accessed. Infant specimens were assessed using the micromethod, qPCR analysis, and a trypomastigote excretory secretory antigen (TESA) blot for detection of immunoglobulin M (IgM)-specific shed acute phase antigen (SAPA) bands, using qPCR as the gold standard. Results: When compared to qPCR, IgM TESA blot was both sensitive and specific for congenital Chagas disease diagnosis. Cumulative sensitivity (whether only 4 bands or all 6 bands were present) was 80% (95% confidence interval [CI], 59%-92%). Specificity was 94% (95% CI, 92%-96%) in the area of endemicity and 100% in the area of nonendemicity. SAPA bands occurred sequentially and in pairs, and parasite loads correlated highly with the number of SAPA bands present. The micromethod detected infection in fewer than half of infected infants. Conclusions: The IgM TESA blot for detection of SAPA bands is rapid, relatively inexpensive, and more sensitive than the micromethod and may be a useful point-of-care test for detection of congenital T. cruzi infection.
Assuntos
Doença de Chagas/congênito , Doença de Chagas/diagnóstico , Testes Diagnósticos de Rotina/métodos , Glicoproteínas/sangue , Immunoblotting/métodos , Imunoglobulina M/imunologia , Neuraminidase/sangue , Trypanosoma cruzi/imunologia , Anticorpos Antiprotozoários/imunologia , Bolívia , Feminino , Humanos , Lactente , Recém-Nascido , Masculino , Peru , Gravidez , Sensibilidade e EspecificidadeRESUMO
Chagas' disease, or American trypanosomiasis, is caused by the protozoan parasite Trypanasoma cruzi. It is estimated that 15,000 new cases of congenital T. cruzi transmission occur in the Americas each year. The aim of this study was to estimate the rate of congenital T. cruzi infection in infants born to infected women living in Ushuaia, Argentina, as well to assess a serologic test using Shed Acute Phase Antigen (SAPA) for a timely diagnosis of congenital infection. The rate of congenital infection among children in the study was 4.4% (3/68). Our results show that for infants younger than 30 days of age, matched blood samples from mother and infant were capable of identifying congenital transmission of infection using an enzyme-linked immunosorbent assay with SAPA. For infants older than 3 months, congenital infection could be ruled out using the same procedure.
Assuntos
Glicoproteínas/sangue , Neuraminidase/sangue , Trypanosoma cruzi/isolamento & purificação , Tripanossomíase/diagnóstico , Argentina , Transmissão de Doença Infecciosa , Diagnóstico Precoce , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Lactente , Recém-Nascido , Gravidez , Tripanossomíase/congênito , Tripanossomíase/parasitologia , Tripanossomíase/transmissãoRESUMO
BACKGROUND AND OBJECTIVES: Conventional serology tests for Trypanosoma cruzi blood banks screening are neither sensitive nor specific enough, and currently no gold standard assay is available. Trans-sialidase inhibition assay (TIA) detects neutralizing antibodies against T. cruzi trans-sialidase. Conventional serology inconclusive, positive and negative blood donor samples were evaluated by employing TIA as a supplementary test. MATERIALS AND METHODS: Three hundred and twenty-one blood donor samples were tested using a combination of assays. Based on the results of testing, these were divided into a number of groups. All samples were tested by TIA. RESULTS: In conventional serology inconclusive samples 48.1% were TIA-positive, 1/54 conventional serology positive samples was TIA-negative. All negative samples from donors without epidemiological risks were TIA-negative; 1/48 was positive in those with epidemiological risk. CONCLUSION: Trans-sialidase inhibition assay application in blood banks may be useful to resolve inconclusive samples, and thus improves donor counseling and allows individual re-entry. The use of TIA in samples from negative conventional test donors but positive epidemiological antecedents may contribute to decrease transfusional risk.
Assuntos
Armazenamento de Sangue/métodos , Doadores de Sangue , Doença de Chagas/sangue , Seleção do Doador/métodos , Glicoproteínas/sangue , Neuraminidase/sangue , Proteínas de Protozoários/sangue , Trypanosoma cruzi/enzimologia , Argentina , Doença de Chagas/enzimologia , Doença de Chagas/prevenção & controle , Doença de Chagas/transmissão , Glicoproteínas/antagonistas & inibidores , Humanos , Neuraminidase/antagonistas & inibidores , Proteínas de Protozoários/antagonistas & inibidores , Estudos RetrospectivosRESUMO
Parasite-derived trans-sialidase (TS) activity was demonstrated in the serum and blood of Trypanosoma cruzi-infected mice. Serum TS activity levels correlated well with parasitemia in BALB/c and Swiss mice during the initial stages of the infection. However, in later stages the TS activity levels decreased despite increasing parasitemia. This coincided with the appearance of circulating TS antibodies. On the other hand, there was always a good correlation between TS activity and parasitemia in athymic nude mice. Sera from mice with high parasitemia and low TS activity inhibited TS activity in vitro. The inhibition was also observed with purified serum IgG, and it was absorbed by staphylococcal protein A, indicating that it was caused by anti-TS IgG antibodies. These antibodies inhibited the enzymatic activity of insolubilized TS, indicating that they act by interfering with the catalytic site rather than by aggregating the enzyme. The presence of inhibitory antibodies, however, did not prevent the progression of parasitemia in BALB/c mice.
Assuntos
Anticorpos Antiprotozoários/sangue , Doença de Chagas/sangue , Glicoproteínas/sangue , Neuraminidase/sangue , Trypanosoma cruzi/enzimologia , Animais , Western Blotting , Doença de Chagas/enzimologia , Doença de Chagas/imunologia , Eletroforese em Gel de Poliacrilamida , Feminino , Glicoproteínas/antagonistas & inibidores , Glicoproteínas/imunologia , Imunoglobulina G/sangue , Imunoglobulina G/isolamento & purificação , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Neuraminidase/antagonistas & inibidores , Neuraminidase/imunologia , Parasitemia/sangue , Parasitemia/enzimologia , Parasitemia/imunologia , Fatores de Tempo , Trypanosoma cruzi/imunologiaRESUMO
trans-Sialidase (TS) is an enzymatic activity described only for trypanosomes that is involved in the invasion of host cells by Trypanosoma cruzi. The enzyme that is shed by the parasite is made of two domains, the C-terminal region containing immunodominant amino acid repeats that define the SAPA antigen and the N-terminal domain that contains the putative region for enzymatic activity. The SAPA antigen induces a strong humoral response detected shortly after infection, both in humans and in mice. This response is directed to the immunodominant domain but is irrelevant in terms of neutralization of TS activity. We now show that TS activity can be detected in sera from acutely infected mice. However, mice infected with a T. cruzi strain whose growth can be controlled by the host did not have detectable levels of TS activity in sera. In fact, sera from these mice were able to abolish TS activity. This inhibition was due to the presence of specific antibodies directed against the enzymatic domain of the protein since they also abolish the activity of a recombinant molecule lacking the immunodominant amino acid repeats. The neutralizing antibodies were present from day 30 after the infection, while antibodies to the immunodominant repeats were detected by day 8 postinoculation, suggesting that the in vivo role of these repeats is to defect the humoral response to the repeat domain until the infection is established.