Benznidazole: Hero or villain of cellular immune response in chronic Chagas disease patients?

Although the treatment of chronic Chagas disease (CCD) patients with Benznidazole (Bz) is still controversial, its use may prevent or delay the progression of the disease to the most severe forms. One of the main factors that can influence the effectiveness of the treatment is the possible cooperation between drug effect and the host immune response. Herein, we evaluated the immune response of peripheral blood mononuclear cells (PBMCs) infected with Trypanosoma cruzi and submitted to Bz treatment. Blood samples of CCD patients (n = 7) and non-infected individuals (n = 6) were drawn to obtain PBMCs. After cell culture, the supernatants were harvested and stored, and the cell analyzed by flow cytometer. The results showed that Bz positively regulated the molecular process of cell activation (CD80) and antigen presentation (HLA-DR), increased phagocytosis receptor and macrophage activation (CD64), and did not induce an exacerbated immune response. In conclusion, these results highlight the relevance of using Bz that, despite not being a true hero, it is also not a villain, as it presents a wide range of pharmacological/immunological response interactions, important for the immune balance in the clinical progression of CCD.

Performance of recombinant chimeric proteins in the serological diagnosis of Trypanosoma cruzi infection in dogs

Background

Dogs are considered sentinels in areas of Trypanosoma cruzi transmission risk to humans. ELISA is generally the method of choice for diagnosing T. cruzi exposure in dogs, but its performance substantially depends on the antigenic matrix employed. In previous studies, our group has developed four chimeric antigens (IBMP-8.1, 8.2, 8.3, and 8.4) and evaluated their potential for diagnosing T. cruzi exposure in humans. For human sera, these chimeric antigens presented superior diagnostic performances as compared to commercial tests available in Brazil, Spain, and Argentina. Therefore, in this study we have evaluated the potential of these antigenic proteins for detection of anti-T. cruzi IgG antibodies in dog sera.

Methodology/Principal findings

The IBMP-ELISA assays were optimized by checkerboard titration. Subsequently, the diagnostic potential was validated through analysis of ROC curves and the performance of the tests was determined using double entry tables. Cross-reactivity was also evaluated for babesiosis, ehrlichiosis, dirofilariosis, anaplasmosis, and visceral leishmaniasis. Best performance was shown by IBMP-8.3 and IBMP-8.4, although all four antigens demonstrated a high diagnostic performance with 46 positive and 149 negative samples tested. IBMP-8.3 demonstrated 100% sensitivity, followed by IBMP-8.4 (96.7–100%), IBMP-8.2 (73.3–87.5%), and IBMP-8.1 (50–100%). The highest specificities were achieved with IBMP-8.2 (100%) and IBMP-8.4 (100%), followed by IBMP-8.3 (96.7–97.5%) and IBMP 8.1 (89.1–100%).

Conclusions/Significance

The use of chimeric antigenic matrices in immunoassays for anti-T. cruzi IgG antibody detection in sera of infected dogs was shown to be a promising tool for veterinary diagnosis and epidemiological studies. The chimeric antigens used in this work allowed also to overcome the common hurdles related to serodiagnosis of T. cruzi infection, especially regarding variation of efficiency parameters according to different strains and cross-reactivity with other infectious diseases.

Despite dogs being considered T. cruzi’s most important domestic sentinel/reservoir and also suffering from the outcomes of the infection, there has never been a commercially available test to diagnose T. cruzi infection in dogs. As such, our group’s objective was to develop a state-of-the-art serological diagnostic test utilizing four chimeric antigens (IBMP-8.1, 8.2, 8.3, and 8.4) in an ELISA platform to accurately identify canine anti-T. cruzi IgG antibodies. The IBMP-ELISA assays were optimized, evaluated for cross-reactivity towards multiple canine parasite’s, including Leishmania spp., its diagnostic potential was validated and the test’s performance was determined using double entry tables. The IBMP-8.3 antigen demonstrated 100% sensitivity, followed by IBMP-8.4, whereas the highest specificities were achieved with IBMP-8.2 (100%) and IBMP-8.4 (100%). Therefore, we’ve concluded that the serodiagnosis through anti-T. cruzi IgG detection in dogs, utilizing chimeric antigenic matrices in immunoassays is a promising tool for veterinary diagnosis and epidemiological surveillance. Furthermore, the use of chimeric antigens efficiently addressed common hurdles related to T. cruzi serodiagnosis, especially regarding efficiency variation in response to different strains and cross-reactivity.

Genetic susceptibility to chronic Chagas disease: an overview of single nucleotide polymorphisms of cytokine genes

Chagas disease is a parasitic infection that is a significant public health problem in Latin America. The mechanisms responsible for susceptibility to the infection and the mechanisms involved in the development of cardiac and digestive forms of chronic Chagas disease remain poorly understood. However, there is growing evidence that differences in susceptibility in endemic areas may be attributable to host genetic factors. The aim of this overview was to analyze the genetic susceptibility to human Chagas disease, particularly that of single nucleotide polymorphisms of cytokine genes. A review of the literature was conducted on the following databases: PubMed/MEDLINE and Scopus. The search strategy included using the following terms: "Cytokines", "Single Nucleotide Polymorphisms" and "Chagas Disease". After screening 25 citations from the databases, 19 studies were selected for the overview. A critical analysis of the data presented in the articles suggests that genetic susceptibility to Chagas disease and chronic Chagas cardiomyopathy is highly influenced by the complexity of the immune response of the host. Follow-up studies based on other populations where Chagas disease is endemic (with distinct ethnic and genetic backgrounds) need to be conducted. These should use a large sample population so as to establish what cytokine genes are involved in susceptibility to and/or progression of the disease.

Characterization of novel Leishmania infantum recombinant proteins encoded by genes from five families with distinct capacities for serodiagnosis of canine and human visceral leishmaniasis

To expand the available panel of recombinant proteins that can be useful for identifying Leishmania-infected dogs and for diagnosing human visceral leishmaniasis (VL), we selected recombinant antigens from L. infantum, cDNA, and genomic libraries by using pools of serum samples from infected dogs and humans. The selected DNA fragments encoded homologs of a cytoplasmic heat-shock protein 70, a kinesin, a polyubiquitin, and two novel hypothetical proteins. Histidine-tagged recombinant proteins were produced after subcloning these DNA fragments and evaluated by using an enzyme-linked immunosorbent assays with panels of canine and human serum samples. The enzyme-linked immunosorbent assays with different recombinant proteins had different sensitivities (67.4-93.0% and 36.4-97.2%) and specificities (76.1-100% and 90.4-97.3%) when tested with serum samples from Leishmania-infected dogs and human patients with VL. Overall, no single recombinant antigen was sufficient to serodiagnosis all canine or human VL cases.

Diagnosis of Chagas disease: what has been achieved? What remains to be done with regard to diagnosis and follow up studies?

In the acute phase and in the chronic forms of Chagas disease, the etiological diagnosis may be performed by detection of the parasite using direct or indirect parasitological methods and by the presence of antibodies in the serum by way of serological tests. Several techniques are easily available, ranging from the simplest wet smear preparation to immuno-enzymatic assays with recombinant antigens that will meet most diagnostic needs. Other tests under evaluation include a molecular test using polymerase chain reaction, which has shown promising results and may be used as a confirmatory test both in the acute and chronic phases of the disease. Better rapid tests are needed for diagnosis, some of which are already under evaluation. Additionally, there is a need for tools that can identify patients cured shortly after specific treatment. Other needs include a marker for prognosis and early diagnosis of congenital transmission.

Cellular immune response from Chagasic patients to CRA or FRA recombinant antigens of Trypanosoma cruzi

We propose to analyze the relation between the cellular immune response of Chagas' disease patients after in vitro stimulation of peripheral blood mononuclear cells (PBMC) with recombinant antigens cytoplasmatic repetitive antigen (CRA) or flagellar repetitive antigen (FRA) of T. cruzi and the chronic clinical forms of disease. Cells were stimulated using phytohemagglutinin, CRA, FRA, or a soluble antigen of Epimastigota (Ag-Epi) for 24 hr, 72 hr, or 6 days. The proliferation of cells was evaluated after 6 days of culture by quantification of incorporated 3H-thymidine. Cytokines were measured in the supernatants obtained after 24 hr (tumor necrosis factor [TNF]-alpha and interleukin [IL]-4), 72 hr (IL-10), and 6 days (interferon [IFN]-gamma) using enzyme-linked immunosorbent assay (ELISA). Cells of the Chagas patients stimulated with the recombinant antigens exhibited higher proliferation responses compared with that of non-Chagas (NC) individuals. However, when proliferation was compared between patients with the cardiac form (CF) or indeterminate form (IF), it was not possible to establish a difference in the response. So far as the cytokines secreted in the culture supernatants after stimulation in vitro with T. cruzi antigens were concerned, the results showed that CRA, as well as Epi-Ag, were able to stimulate the production of TNF-alpha and IFN-gamma in Chagas patients as compared with NC individuals. However, the cytokine levels after stimulation with the T. cruzi antigens were not different between the patients with CF and IF. CRA was capable of inducing a T helper type 1 (Th1) immune response, with elevated production of TNF-alpha and IFN-gamma in Chagas patients that are carriers of CF and IF clinical forms.

[Family screening for HBB*S gene and detection of new cases of sickle cell trait in Northeastern Brazil]

OBJECTIVE

To estimate the additional number of affected individuals based on the prevalence of sickle-cell syndromes among relatives of index cases.

METHODS

Cross-sectional study of relatives of a random sample of index cases identified through a neonatal screening program in Northeastern Brazil, between 2001 and 2005. The extended family trial model included 463 relatives of 21 index cases. Relatives were classified as nuclear family (NF: father, mother, and siblings); first degree extended family (N1: grandparents, uncles and aunts, and first cousins); second degree extended family (N2: children of first cousins); extended family (NA: NF+N1+N2); and extended nuclear family (NA1: NF+N1). The presence of HBB*S and other abnormal hemoglobins was confirmed by high-performance liquid chromatography. The association between the presence of HBB*S and other variables was calculated using prevalence ratios and their respective 95% confidence intervals, and differences between means were calculated using Student's t test with a 5% significance level.

RESULTS

Of relatives, 81% had no knowledge of sickle-cell anemia and HBB*S was present in 114 family members. A total of 53.3% of the studied population was considered as of reproductive age, and 80% of HBB*S carriers had already had children. Frequency was higher among NF (69%), but was also high in N1 (22.8%). NA1 screening resulted in the detection of 69 carriers additional (a 172% increase).

CONCLUSIONS

These results indicate that family screening for the identification of sickle-cell carriers should be extended to first degree relatives.

Triagem familiar para o gene HBB*S e detecção de novos casos de traço falciforme em Pernambuco

OBJETIVO: Estimar o incremento no número adicional de afetados com base na prevalência de síndromes falciformes em familiares de casos-índice. MÉTODOS: Estudo transversal em familiares de amostra aleatória dos casos-índice identificados por programa de triagem neonatal em Pernambuco, no período de 2001 a 2005. O modelo de triagem familiar ampliado incluiu 463 membros familiares de 21 casos-índice. Os familiares foram categorizados como: núcleo reduzido (NR -pai, mãe e irmãos); de primeiro grau (N1 - avós, tios e primos de primeiro grau); de segundo grau (N2 - filhos dos primos de primeiro grau); ampliado (NA - NR+N1+N2) e ampliado de primeiro grau (NA1 -NR+N1). A confirmação da presença de HBB*S e detecção de hemoglobinas anormais foram realizadas por meio da High Performance Liquid Chromathgraphy. A associação entre a presença de HBB*S e variáveis foi testada pelo cálculo da razão de prevalência e respectivos IC 95% e a diferença entre médias verificadas pelo teste t de Student, ao nível de significância de 5%. RESULTADOS: A anemia falciforme era desconhecida por 81% dos familiares; o gene HBB*S esteve presente em 114 familiares. Observou-se que 53,3% da população estudada estava na faixa considerada reprodutiva e 80% das pessoas portadoras do gene HBB*S já tinham gerado filhos. A freqüência foi maior no núcleo NR (69%), mas também elevada no N1 (22,8%). O NA1 resultou na detecção de 69 portadores adicionais (aumento de 172%). CONCLUSÕES: Os resultados indicam que a triagem familiar para identificação de portadores de síndrome falciforme deve ser estendida para os familiares até o primeiro grau.

Molecular variations linked to the grouping of beta- and alpha-globin genes in neonatal patients with sickle cell disease in the State of Pernambuco, Brazil

Various factors have been described as phenotypic modulators of sickle cell disease, such as levels of fetal hemoglobin (Hb F), presence of alpha-thalassemia (thal), and haplotypes of the beta-globin genes. In order to characterize and determine the frequency of the betaS and betaC mutations and the prevalence of -alpha3.7-thal, 74 patients with sickle cell disease detected during neonatal screening in the State of Pernambuco, Brazil, were studied. The haplotypes of the beta gene and -alpha3.7-thal were determined using polymerase chain reaction (PCR), and specific restriction endonucleases were used to establish the polymorphic sites of the haplotypes. The results showed the high frequency of the Central African Republic (CAR) or Bantu haplotype in the State of Pernambuco, Brazil. The low frequency of the Benin haplotype recorded in this study, in comparison with other states in northeast Brazil, suggests the diversity of origins of Afro-Brazilians in this region.

Diagnosis of canine visceral leishmaniasis: biotechnological advances

Human visceral leishmaniasis (HVL) is endemic in the tropical and sub-tropical regions of Africa, Asia, the Mediterranean, Southern Europe and South and Central America, with approximately 500,000 new cases reported annually. As dogs are considered to be the major reservoirs for HVL, the accurate diagnosis of disease in these animals is important. Diagnosis of canine visceral leishmaniasis (CVL) is performed mainly by direct parasitological methods that can yield false-negative results, either because of the very low number of Leishmania spp. organisms in clinical samples (bone marrow and lymph nodes) or because morphological identification is difficult. In addition, these methods are invasive. Conventional serological techniques are limited by cross-reactivity with other parasitic diseases and because several technical procedures have not been standardised. The development of polymerase chain reaction based approaches and immunoassays based on the use of recombinant antigens aimed at improving the sensitivity and specificity of CVL diagnosis is discussed.

Canine visceral leishmaniosis: A comparative analysis of the EIE-leishmaniose-visceral-canina-Bio-Manguinhos and the IFI-leishmaniose-visceral-canina-Bio-Manguinhos kits

This study evaluated the performance of the EIE-leishmaniose-visceral-canina-Bio-Manguinhos (EIE-LVC) kit and to compare it with that of the IFI-leishmaniose-visceral-canina-Bio-Manguinhos (IFI-LVC) kit. Four groups of dogs were studied: group 1 (G1), dogs with clinical signs indicative of CVL and testing positive for the parasite (n = 25); group 2 (G2), dogs with only a presumed diagnosis of CVL (n = 62); group 3 (G3), dogs that had never lived in an area where CVL is endemic and never received a blood transfusion (n = 16); group 4 (G4), dogs carrying other parasites: such as babesiosis (n = 4), ehrlichiosis (n = 6) and demodicosis (n = 1). G1 and G3 were used for the calculation of sensitivity and specificity, respectively. The EIE-LVC showed a sensitivity of 72% (IC 95%: 50.4-87.1%) and a specificity of 87.5% (IC 95%: 60.4-97.8%). The value of the kappa index was 0.975 (CI 95%: 0.926-1.024), which represents an excellent fit. For IFI-LVC, the sensitivity was 68.0% (CI 95%: 46.4-84.3%) and the specificity 87.5% (CI 95%: 60.4-97.8%). When the tests were conducted in parallel, sensitivity was 92.0% (CI 95%: 72.5-98.6%) and specificity 75.0% (CI 95%: 47.4-91.7%). However, when conducted consecutively, the tests showed a sensitivity of 48.0% (CI 95%: 28.3-68.2%) and a specificity of 100.0% (CI 95%: 75.9-99.4%). The analysis of clinically suspected dogs using IFI-LVC and EIE-LVC kits in parallel, revealed that 26/62 animals were positive. Cross-reaction was observed in a dog with demodicosis. These results lead to the following conclusions: (1) the performance of the EIE-LVC kit is not statistically different from the IFI-LVC and (2) the kits must be used in parallel if higher sensitivity is required, reducing the number of false-negative results.

Immunization with cytoplasmic repetitive antigen and flagellar repetitive antigen of Trypanosoma cruzi stimulates a cellular immune response in mice

In previous studies, we demonstrated that CRA and FRA recombinant proteins, used for diagnosis of Chagas' disease, elicited a humoral immune response in susceptible and resistant mice. To understand better the immune response to these proteins, we have evaluated, the cellular immune response in CRA- and in FRA-immunized BALB/c and C57BL/6 mice. A specific cellular lymphoproliferative response was observed in both strains of mice. Spleen cell cultures mainly from CRA-immunized C57BL/6 and FRA-immunized BALB/c mice produced high levels of IFN-y, indicating the induction of a Type 1 immune response. Regarding the T cell subsets, CD4+ T cells were the major source of IFN-y in CRA- and FRA-immunized mice. These results suggest that CRA and FRA are important immunogens in inducing a Type 1 immune response and that they may be considered as potential vaccine antigens.

Humoral and cellular immune responses in BALB/c and C57BL/6 mice immunized with cytoplasmic (CRA) and flagellar (FRA) recombinant repetitive antigens, in acute experimental Trypanosoma cruzi infection

In previous studies, cytoplasmic repetitive antigen (CRA) and flagellar repetitive antigen (FRA) proteins induced specific humoral and cellular immune responses in susceptible and resistant mice in the absence of Trypanosoma cruzi infection with a significant induction of the Interferon-gamma (IFN-gamma) production in those animals. In this follow-up paper, the immunostimulatory and protective effects of these proteins were evaluated by immunizing with CRA or FRA antigens, BALB/c and C57BL/6 mice and challenging with a T. cruzi (Y strain). Both proteins induced humoral response with high levels of IgG isotypes as well as cellular immunity with high levels of IFN-gamma when compared to controls. However, the lymphocyte proliferative response was minimal. The survival rate at 30 days post-infection was significant in CRA (60%) or FRA (50%)--immunized BALB/c mice and CRA (83.3%)--immunized C57BL/6 mice. Taken as a whole these findings indicate that CRA and FRA are immunogenic and potentially important for protective immunity.

Reservosome: an endocytic compartment in epimastigote forms of the protozoan Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae). Correlation between endocytosis of nutrients and cell differentiation

Reservosomes are large membrane-bound organelles found at the posterior end of epimastigote forms of Trypanosoma cruzi, but absent in amastigotes and trypomastigotes. We have transferred bloodstream trypomastigotes to LIT medium supplemented with gold-labelled transferrin in order to analyse, at the ultrastructural level, the occurrence of reservosomes and endocytosis during the trypomastigote to epimastigote differentiation. After 24 h, the trypomastigotes differentiated into amastigotes, which adhered to each other forming large clusters. Electron-dense vesicles were detected close to the Golgi complex in cells with intermediary characteristics between amastigotes and epimastigotes, but typical reservosomes at the posterior cell tip were still absent. Transferrin-gold complexes were observed only bound to the surface of clustered cells. After 72 h, epimastigotes were observed being released from the clusters and free-swimming epimastigotes appeared, containing electron-dense vesicles at their posterior region. Typical reservosomes, labelled with transferrin-gold, were observed only in free-swimming epimastigotes. When fully differentiated epimastigotes were incubated with transferrin-gold complexes and then processed for the immunocytochemical detection of cysteine proteinase, all reservosomes were positive for the enzyme, but co-localization of both markers did not occur in all organelles. Our data demonstrate that in T. cruzi epimastigotes endocytosis is strongly related to reservosome biogenesis during the trypomastigote to epimastigote differentiation process.

Elevated concentrations of CCL2 and tumor necrosis factor-alpha in chagasic cardiomyopathy

Chronic myocarditis is the main pathological finding associated with Chagas disease-related morbidity. Concentrations of CCL2, CCL3, tumor necrosis factor (TNF)-alpha, and brain natriuretic peptide (BNP) were evaluated in plasma samples obtained from patients with different clinical forms of chronic chagasic cardiomyopathy. Patients with more-severe Chagas disease had elevated plasma concentrations of TNF-alpha, CCL2, and BNP, and there was a good correlation between levels of these proteins (especially TNF-alpha ) and the degree of heart dysfunction. Indeed, TNF-alpha level was an excellent predictor of heart failure. Peripheral blood mononuclear cell samples obtained from patients with mild or severe chagasic cardiomyopathy produced greater amounts of TNF-alpha and CCL2 than did those obtained from noninfected individuals. The elevation of TNF-alpha and CCL2 levels in the plasma of patients appears to be secondary to the degree of heart dysfunction, whereas spontaneous production of TNF-alpha and CCL2 by mononuclear cells is secondary not only to heart dysfunction, but also to the underlying inflammation in the heart of chagasic patients. Measurement of the TNF-alpha level could be a useful tool in the identification of patients with heart dysfunction who may benefit from further investigation and treatment.

Mitogenic activity of Cratylia mollis lectin on human lymphocytes

The mitogenic effect of Cratylia mollis seed lectin preparations containing two (Cramoll 1,4) or one molecular form (Cramoll 1) showed activity similar to the well known T-cell mitogen, concanavalin A (Con A). The effect on human lymphocytes was analyzed through a colorimetric assay using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT). Inhibition of lymphocyte proliferation with methyl-alpha-d-mannoside (both preparations) indicated that the mitogenic effect involved carbohydrate lectin binding sites.

Impedimetric evaluation for diagnosis of Chagas’ disease: antigen–antibody interactions on metallic eletrodes

A polypeptide chain formed by recombinant antigens, cytoplasmic repetitive antigen (CRA) and flagellar repetitive antigen (FRA) (CF-Chimera) of Trypanosoma cruzi, was adsorbed on gold and platinum electrodes and investigated by electrochemical impedance spectroscopy on phosphate buffer saline solutions (PBS) containing a redox couple. It was found that the adsorption is strongly sensitive to the oxide layer on the electrode surface. In the majority of the experiments the antigens retained their activity as observed through their interaction with sera from chronic chagasic patients. The results expressed in terms of the charge transfer resistance across the interface, indicate the viability of using the impedance methodology for the development of a biosensor for serological diagnosis of Chagas' disease.

Antibody isotype responses in Balb/c mice immunized with the cytoplasmic repetitive antigen and flagellar repetitive antigen of Trypanosoma cruzi

In the present report we analyzed the levels of IgG1, IgG2a, IgG2b and IgG3 isotypes from Balb/c mice immunized with cytoplasmic repetitive antigen (CRA), and flagellar repetitive antigen (FRA) of Trypanosoma cruzi. The immunization was done by subcutaneous route three times (20 days apart) and the analysis was performed 14 days after each treatment. CRA-immunized mice produced high levels of all IgG isotypes, mainly IgG3 and IgG1. FRA-immunization elicited only high levels of IgG1.

Chagas' disease diagnosis: comparative analysis of recombinant ELISA with conventional ELISA and the haemagglutination test

BACKGROUND AND OBJECTIVES

Serological screening for Chagas' disease in the blood banks of South America is carried out by using two different assays that generally show a high number of inconclusive results. To establish a combination of two tests that can minimize the number of inconclusive results, we compared a recombinant enzyme-linked immunosorbent assay (ELISA) with two conventional tests.

MATERIALS AND METHODS

Serum samples from chagasic patients (n = 112), from non-chagasic individuals (n = 143) and from patients with other diseases (n = 32) were tested using three assays: recombinant ELISA (Rec-ELISA); conventional ELISA (Con-ELISA); and the indirect haemagglutination (IHA) test.

RESULTS

When we evaluated the data by matching the Rec-ELISA and the IHA test, 52 inconclusive results were obtained. When Rec-ELISA and Con-ELISA were matched, only four inconclusive results were observed.

CONCLUSIONS

Our investigation indicates that the use of two ELISAs with different antigen preparations provides an effective test combination for blood bank screening of Chagas' disease.

Protective immunity of single and multi-antigen DNA vaccines against schistosomiasis

We evaluated the usefulness of the combination of three plasmids encoding tegumental (pECL and pSM14) and muscular (pIRV5) antigens of the Schistosoma mansoni on improving the protective immunity over the use of a single antigen as DNA vaccines. Female BALB/c mice were inoculated twice with 25 micro g DNA plasmid within two weeks interval. The challenge was performed with 80 cercarias of a regional isolate of S. mansoni (SLM) one week after the last immunization. Six weeks after challenge, all mice were perfused for worm load determination. The following groups were analyzed: saline; empty vector; monovalent formulations of pECL; pSM14 and pIRV5 and also double combinations of pECL/pIRV5 and pIRV5/pSM14 and a triple combination of pECL/pIRV5/pSM14. The protection was expressed as a percentage of worm loads in each group compared with the saline group. The results obtained were 41% (p < 0.05); 52% (p < 0.05); 51% (p < 0.05); 48% (p < 0.05); 55% (p < 0.05); 45% (p < 0.05); 65% (p < 0.05) for each group respectively.

Antibody isotype responses to egg antigens in human chronic Schistosomiasis mansoni before and after treatment

In the present communication we analyzed the levels of IgG1, IgG2, IgG3, IgG4 and IgE isotypes to soluble egg antigen of Schistosoma mansoni by ELISA in individuals from an endemic area for schistosomiasis in Northeast Brazil. The analysis was performed before and after treatment to evaluate the age-dependent pattern, and to identify differences in the reactivities to antigens. Our results suggest that schistosomiasis treatment would not interfere with this sort of immune response.

Use of the EIE-recombinant-Chagas-biomanguinhos kit to monitor cure of human Chagas' disease

We used the EIE-Recombinant-Chagas-Biomanguinhos kit (EIE-Rec kit) developed by the Oswaldo Cruz Foundation, Brazil, to monitor cure of chagasic patients who were treated during the acute phase of T. cruzi infection. Treated patients were previously studied by parasitological and serological tests and classified as cured patients (CP) (n = 10), dissociated patients (DP) (n = 6), and noncured patients (NCP) (n = 6). When sera of these patients were assayed by EIE-Rec kit all sera from NCP and all sera from CP showed positive and negative reactions, respectively. These results were in full agreement with those obtained previously by the classical tests. Two DP showed a positive reaction; the remaining four displayed a negative reaction, similar to that observed in sera from nonchagasic (NCh) individuals, and could therefore be considered CP. Our results suggest that the EIE-Rec kit could be used to monitor the efficacy of Chagas' disease treatment.

Excretory-secretory antigens of Trypanosoma cruzi are potentially useful for serodiagnosis of chronic Chagas' disease

The reactivities of sera from chronic chagasic patients against the trypomastigote excreted-secreted antigens (TESA) of Trypanosoma cruzi strains with different biodemes were analyzed by TESA-blot and TESA-enzyme-linked immunosorbent assay (ELISA). Although both tests presented high sensitivity and specificity, TESA-ELISA is more appropriate for screening a larger number of samples.

Serodiagnosis of chronic Chagas infection by using EIE-Recombinant-Chagas-Biomanguinhos kit

A kit based on an enzyme immunoassay, EIE-Recombinant-Chagas-Biomanguinhos, developed by the Oswaldo Cruz Foundation, was evaluated for the serodiagnosis of chronic Chagas disease. Evaluation was performed with 368 serum samples collected from individuals living in an endemic area for Chagas disease: 131 patients in the chronic phase with confirmed clinical, epidemiological, and serological diagnosis (indirect immunofluorescence, indirect hemagglutination or enzyme-linked immunosorbent assay) and 237 nonchagasic seronegative individuals were considered negative control. The EIE-Recombinant-Chagas-Biomanguinhos kit showed high sensitivity, 100% (CI 95%: 96.4-100%) and high specificity, 100% (CI 95%: 98-100%). The data obtained were in full agreement with clinical and conventional serology data. In addition, no cross-reaction was observed with sera from patients with cutaneous (n=14) and visceral (n=3) leishmaniasis. However, when these sera were tested by conventional serological assays for Chagas disease, cross-reactions were detected in 14.3% and 33.3% of the patients with cutaneous and visceral leishmaniasis, respectively. No cross-reactions were observed when sera from nonchagasic seronegative patients bearing other infectious disease (syphilis, n=8; HTLV, n=8; HCV, n=7 and HBV, n=12) were tested. In addition, sera of patients with inconclusive results for Chagas disease by conventional serology showed results in agreement with clinical evaluation, when tested by the kit. These results are relevant and indicate that the referred kit provides a safe immunodiagnosis of Chagas disease and could be used in blood bank screening.

Dynamics of the antibody response in patients with therapeutic or spontaneous cure of American cutaneous leishmaniasis

The antigen specificity and the level of the antibody response were analysed in Perambuco State, Brazil, in sera collected in 1995-96 from 58 patients with clinical American cutaneous leishmaniasis (ACL), 25 ACL patients with apparent cure after chemotherapy with meglumine antimonate, and 10 ACL patients with spontaneous cure. Assessment was by immunoblot analysis, ELISA and indirect immunofluorescence, with Leishmania (Viannia) braziliensis antigens, with a particular interest in evaluating whether the dynamics of the antibody response could be useful to monitor clinical cure. A clear decrease of IgG antibody reactivity was noticed after clinical healing, for all of the antigens analysed, with the exception of the 19 kDa antigen, whose recognition frequency in fact increased in the spontaneously cured patients, suggesting that this antigen may play a role in protective immunity against cutaneous leishmaniasis. The recognition frequencies of the most frequently recognized antigens (27 and 30 kDa antigens) diminished approximately 2-fold in patients clinically healed, suggesting that they could be useful as a marker of cure of ACL. In addition, some of the healthy individuals living in endemic areas presented the same immunoblotting pattern of reactivity observed in active ACL, possibly representing asymptomatically infected individuals.

Characterization of Sm13, a tegumental antigen of Schistosoma mansoni

Sm13, a 13-kDa Schistosoma mansoni tegumental antigen, is one of the principal polypeptides recognized by antibodies from mice protectively vaccinated with adult-worm tegumental membranes. To obtain the complete gene encoding Sm13 we subcloned and sequenced a cDNA and a fragment of a genomic clone. The collated sequence contains 1,088 nucleotides and represents the full-length open reading frame of the gene, encoding a protein of 104 amino acids with a calculated molecular mass of 11,923 Da, compatible with the native protein identified in the tegumental membranes. The sequence derived from genomic DNA contains a 45-nucleotide intron. The analysis of the predicted protein suggests the presence of both N- and C-terminal hydrophobic membrane-spanning segments, and the coding region contains no homology in the currently available data bases. Additionally, the coding region is preceded by putative CCAAT and TATA boxes that may be involved in the control of expression. Western-blot analysis and indirect immunofluorescence resulted in the identification of a 13-kDa protein (Sm13) in the tegument of adult worms. The present study reveals that Sm13 behaves as an integral membrane protein upon partitioning in Triton X-1 14 and that it is present in worms of 3 weeks or older but not in schistosomula or miracidia. Moreover, it is also specifically recognized by sera from some schistosomiasis patients in enzyme-linked immunosorbent assay and Western-blot analysis, suggesting that it is immunogenic in human schistosomiasis.

Immunodiagnosis of chronic Chagas' disease using the Tc 46 and Tc 58 antigens

The polypeptides of 46 and 58 kDa were recognized in different T. cruzi strains (Y, WSL and Colombiana) by serum of all chagasic patients studied. These polypeptides were isolated from T. cruzi Y strain and used in ELISA. The sensitivity and specificity were 97.6% [CI 95%: 86-100%] and 100% [CI 95%: 89.3-100%], respectively when Tc 46 was used. When Tc 58 was used the sensitivity and specificity were 100% [CI 95%: 89.6-100%] and 90.2% [CI 95%: 75.9-96.8%], respectively.

Identification of potentially diagnostic Leishmania braziliensis antigens in human cutaneous leishmaniasis by immunoblot analysis

The antibody response in patients with American cutaneous leishmaniasis was analyzed by immunoblotting with soluble and insoluble antigens of Leishmania braziliensis. The recognition of the 27- and/or 30-kDa soluble antigens was considered relevant for the diagnosis of cutaneous leishmaniasis. Immunoblotting was found to be significantly more sensitive and specific than indirect immunofluorescence and enzyme-linked immunosorbent assay.

[Hemoglobin "S" positive newborn detected by cord blood and its characteristics]

OBJECTIVE: To evaluate the prevalence of hemoglobin "S" (Hb "S") in babies born at the Instituto Materno Infantil de Pernambuco (IMIP) and its occurrence according to sex, birth weight and Apgar score. METHODS: We carried out a cross-sectional descriptive study of all babies born in the IMIP from October 1996 to March 1997. We used alkaline electrophoresis to analyze cord blood samples (1,988). Data for other variables were collected from medical reports. EPI-Info 6.0 was used to analyze the data.RESULTS: We found 105 (5.3%) newborns with Hb "S": 102 (5.1%.) as sickle cell trait (Hb "FAS"), and 3 (0.2%) as sickle cell disease (Hb "SC"). No cases of homozygosis were found. Newborns with and without Hb "S" did not differ in relation to sex, birth weight and Apgar score. CONCLUSIONS: We suggest the implementation of neonatal screening for hemoglobinopathies for all the newborns in Recife, Brazil, with further follow up focusing on genetic counseling for suspected and positive cases.

Partial protection of mice against Trypanosoma cruzi after immunizing with the TcY 72 antigenic preparation

A 72 kDa Trypanosoma cruzi glycoprotein recognized by the 164C11 monoclonal antibody (IgM isotype) was purified by preparative electrophoresis. The antigenic preparation obtained, named TcY 72, was used to immunize C57Bl/10 mice. The following results were observed after immunization: (1) induction of higher titres of IgG than IgM antibodies, as evaluated by indirect immunofluorescence; (2) significant DTH after injection of epimastigotes in mice footpads; (3) peak parasitemia in immunized mice was significantly reduced and animals were negative by 13 days post-infection, although the mice still succumb to infection; (4) the phenotypic analysis of spleen cell populations showed a decrease in the CD4/CD8 ratio in immunized mice. Taken as a whole, these findings indicate that TcY 72 is immunogenic and potentially important for protective immunity.

Vaccines against human parasitic diseases: an overview

There are no vaccines currently available to control the major human parasitic diseases, although there is evidence of acquired immunity and resistance to reinfection in most of the parasitic infections. The present manuscript concentrates on the vaccines for parasitic diseases that are in the most advanced stages of development: malaria, leishmaniasis and schistosomiasis. Vaccines for malaria and leishmaniasis have been taken to clinical trials while vaccines for schistosomiasis are being considered for Phase I (assessment of safety and immune responsiveness in volunteers). We have attempted to give a factual account of the present status of knowledge of vaccines against human parasitic diseases, emphasizing both the successes and setbacks. We do not intend to cover the enormous literature in the field but have concentrated on the most promising antigenic preparations. Finally, some new approaches for the development of vaccines are discussed including nucleic acid vaccines and the use of cytokines as adjuvants.

PCR and sero-diagnosis of chronic Chagas' disease. Biotechnological advances

In the acute phase of Chagas' disease, when the parasitemia is high, diagnosis can be easily made using conventional parasitological methods. During the chronic phase, due to the low parasitemia, diagnosis is performed mainly by immunological methods. Conventional serological techniques are limited by cross-reactivity with other parasitic diseases, non-standardization of reagents, and the diversity of technical procedures. Methods are being developed to improve the sensitivity and specificity of diagnosis using molecular approaches. PCR-based detection systems and the use of recombinant antigens in ELISA are the most promising.

A monoclonal antibody against blood forms of Trypanosoma cruzi lyses the parasite in vitro and inhibits host cell invasion

Monoclonal antibodies (mAbs) of the IgM isotypes were produced from mice immunized with blood forms of Trypansoma cruzi Y strain. Characterization of the epitope recognized by one of the mAbs, 164C11, as well as the effects of this mAb on complement-mediated lysis and host cell invasion are reported. Immunocytochemical analysis showed that the mAb was reactive with various strains of T. cruzi (Y, WSL, and Colombiana) as well as other trypanosomatids. The mAb 164C11 demonstrated a high complement-mediated lytic activity against bloodstream trypomastigotes, being more effective than chronic mouse serum. A protein with an apparent molecular weight of 72 kDa was detected by this mAb on all developmental stages of T. cruzi. Studies using periodate and endoglycosidase treatments suggested that the epitope is not a carbohydrate and seems to be located on the parasite membrane. In addition, preliminary results are presented, suggesting that the 72-kDa protein is involved in adhesion/or internalization of bloodstream trypomastigotes.

A simple method for detection of monoclonal isotypes

A simple rapid method of enzyme labeled anti-isotype assay (ELIA) for detection of monoclonal isotype on hybridoma cells is proposed. This alternative method was first carried out on hybridoma cell lines 147C11 and 257C11 produced against Trypanosoma cruzi and male accessory secretion of Panstrongylus megistus, respectively. The monoclonal antibodies produced by these hybridoma were characterized by this method as IgM (147C11) and IgG1 (257C23) isotypes, allowing evaluation of isotype without having to wait until the concentration of antibody present in the supernatant itself rises. Results were confirmed by Ouchterlony immunodiffusion. The proposed method offers the advantages of a permanent rapid procedure for light microscopy.

Isolation of Trypanosoma cruzi from blood by histopaque and continuous percoll gradient centrifugations

Separation of the blood forms of trypanosomes from the blood of infected animals is difficult, especially in the case of Trypanosoma cruzi Y strain. Two procedures to isolate the Y strain blood forms of T. cruzi using polyvinyl pyrrolidone-coated silica (percoll) and histopaque are reported in this study. The recovery rates of parasites were 16 +/- 5 and 68 +/- 16%, respectively. The parasites isolated by these methods presented normal motility and morphology and were infective to albino mice with prepatent periods, parasitemia curves, and polymorphism patterns during the infection that were similar to those of control parasites. In addition, the preservation of surface antigens was confirmed by immunocytochemical studies.

Natural lectin activity in the haemolymph of Panstrongylus megistus (Heteroptera: Reduviidae)

The haemolymph of Panstrongylus megistus showed a natural lectin activity for a wide range of vertebrate erythrocytes. Agglutination was observed against all vertebrate erythrocytes tested (human ABO, duck, rabbit, mouse, sheep, chicken and cow). Cow erythrocytes showed the lowest titre. Concerning human erythrocytes, the lectin activity was similar in the types A+, B+ and AB+ while the highest activity was observed in the type O+. Determination of minimal inhibitory concentrations was carried out with human erythrocytes type O+. Agglutination was inhibited by several carbohydrates (rhamnose, D-galactose, raffinose, D-lactose and D-fucose). Rhamnose was reported as the strongest inhibitor (0.78 mM). The results suggest the presence of more than one lectin in the haemolymph of P. megistus.

The use of non-specific immunopotentiators in experimental Trypanosoma cruzi infection

The effects of levamisole, isoprinosine and Corynebacterium parvum on Trypanosoma cruzi (Y strain) experimental infection of mice were studied. In prophylactic treatment these drugs reduced the peak of parasitaemia, and had no apparent effect on mortality rate or on histopathological and electrocardiographic findings. Levamisole and isoprinosine had no effect when used after infection. Electrocardiograms were obtained from all chronic chagasic mice. The most frequent changes were left atrial overload and first degree atrio-ventricular block. These findings became more frequent the longer the animals survived. The net effect of the non-specific immunopotentiators seems to depend on several factors: host immune state, severity of infection, dose and timing of drug administration. This probably explains the variable published results and the paradoxical findings of different laboratories.