The present study was conducted to detected IgG antibodies using Strongyloides venezuelensis alkaline extract for the diagnosis of human strongyloidiasis by the enzyme-linked immunosorbent assay (ELISA). (Siddiqui & Berk 2001). Due to the fluctuations on the larvae shedding in subjects infected with S. stercoralis, the parasitological methods have shown low sensitivity, being necessary repeated stool exams (Dreyer et al. 1996, Uparanukraw et al. 1999. Complementary tests for the diagnosis and the monitoring of the immune response in this parasitosis have been developed. However, the major limitation for the standardization of immunological methods is the difficulty in obtaining large amount of S. stercoralis larvae (Sato et al. 1995, Costa-Cruz et al. 1997.The aim of this study was to diagnose human strongyloidiasis by enzyme-linked immunosorbent assay (ELISA) using alkaline extract of S. venezuelensis filariform larvae. The study received approval from the Ethical Committee of the Federal University of Uberlândia.Strain of S. venezuelensis was isolated from feces of the wild rodent Nectomys squamips in August 1988 and maintained by experimental infection in Rattus norvergicus-Wistar. Infective larvae of S. venezuelensis were obtained from the feces of rats experimentally infected and cultured in mineral charcoal for two days at room temperature. Larvae were recovered by the Rugai et al. (1954) method and washed five times in 0.01 M phosphatebuffered saline (PBS) pH 7.2 containing 400 IU/ml of benzyl penicilin and 2 mg/ml of streptomycin sulfate and then stored at -70 o C in PBS until the antigen preparation. Alkaline extract of 100,000 larvae of S. venezuelensis was prepared by adding 1 ml of 0.15 M NaOH (Merck, Germany) during 6 h under slow agitation at 4 o C. Subsequently, 0.5 ml of 0.3 M HCl (Merck) was added until reaching the pH 7.0, and this preparation was centrifuged at 10,000 g for 30 min at 4 o C. Protein determination of the supernatant was 240 µg/ml as detected by the Lowry et al. (1951) method.ELISA was carried out using polystyrene microplates (Difco, São Paulo, Brazil) and the reagents were assayed in 50 µl/well. The plates were coated with alkaline extract at 10 µg/ml in 0.06 M carbonate-bicarbonate buffer, pH 9.6 and incubated overnight at 4 o C. The plates were washed three times for 5 min with PBS containing 0.05% Tween 20 (PBS-T) and incubated with the serum samples, including positive and negative control sera, diluted at 1:80 in PBS-T for 45 min at 37 o C. After new washing as previously described, the conjugate rabbit anti-human IgG (Fc chain specific) labeled with peroxidase (Sigma, US) diluted at 1:2,000 in PBS-T was added and incubated for 45 min at 37 o C. After washing, the enzymatic substrate consisting of H 2 O 2 (Merck) plus o-phenylenediamine (OPD) diluted in 0.1 M citrate-Na 2 HPO 4 buffer pH 5.5 was added. The reaction was stopped after 15 min with 20 µl/well of 1 M H 2 SO 4 and the absorbance values were determined in an
The aim of this study was to detect levels of IgG and IgA by enzyme-linked immunosorbent assay (ELISA) using alkaline extracts of larvae, adult female worms, and eggs of Strongyloides venezuelensis as antigen. One hundred twenty serum samples divided into 3 groups were analysed: group I (40 strongyloidiasis patients), group II (40 patients with other parasitic infections), and group III (40 healthy subjects). Statistical variations were analyzed using analysis of variance. There was a significant statistical difference (P < 0.001) in the detection of antibodies in group I between larvae and female antigens and between larvae and egg antigens, with higher positivity using larvae antigen. The larvae antigen showed the highest values for sensitivity, specificity, and diagnostic efficiency in ELISA. This study is the first that examines the use of adult female worm and egg antigens to detect antibodies for human strongyloidiasis diagnosis compared with the larval extract. By comparing all 3 extracts, larval antigens demonstrated better diagnostic parameters.
SUMMARYParasitological and immunological diagnoses were part of a study conducted among 151 children, 83 immunocompromised (IC) and 68 non-immunocompromised (non-IC) aged from zero to 12, seen at
Levels of total and specific anti-Trypanosoma cruzi immunoglobulin E (IgE) were determined by immunoenzymatic assay among 101 samples of pericardial fluid from patients who had died in one trypanosomiasis endemic area in central Brazil. These samples were divided into 6 groups. Group I, 17 samples from patients with the cardiac form of Chagas disease; group II, 11 samples from patients with the digestive form of Chagas disease, presenting megaoesophagus and/or megacolon; group III, 41 samples from patients with the indeterminate form of Chagas disease; group IV, 4 samples from patients with both cardiac and digestive forms of Chagas disease; group V, 5 samples from patients who suddenly died and were seropositive for T. cruzi antibodies; group VI, 23 samples, used as a control group, which came from patients seronegative for T. cruzi antibodies. Significantly high levels of total IgE were observed in groups I, II, III, IV and V when compared with group VI (mean concentrations 708-1157 iu/mL compared with 394 iu/mL). In groups I-V, 32 samples (41%) had specific anti-T. cruzi IgE antibodies. The individual percentage positivity rates in these groups were 64.7% (group I), 45.4% (group II), 34.1% (group III), nil (group IV), and 40.0% (group V). A significant correlation between total IgE and specific anti-T. cruzi IgE was observed only in the samples from patients with the cardiac form of Chagas disease (group I).
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