Strongyloidiasis Serological Analysis with Three Different Biological Probes and Their Electrochemical Responses in a Screen-Printed Gold Electrode.

(1) Background: The validation of biological antigens is the study's utmost goal in biomedical applications. We evaluated three different probes with single and multiple epitopes through electrochemical detection of specific IgG in serum for human strongyloidiasis diagnosis. (2) Methods: Screen-printed gold electrodes were used and probes consisting of two single-epitope synthetic peptides (D3 and C10) with different sequences, and a multi-epitope antigen [detergent phase (DP)-hydrophobic membrane proteins]. Human serum samples from three populations were used: Strongyloides stercoralis positive, positive for other parasitic infections and negative controls. To test the immobilization of probes onto a screen-printed gold electrode and the serum IgG detection, electrochemical analyses were carried out through differential pulse voltammetry (DPV) and the electrode surface analyses were recorded using atomic force microscopy. (3) Results: The electrochemical response in screen-printed gold electrodes of peptides D3 and C10 when using positive serum was significantly higher than that when using the DP. Our sensor improved sensitivity to detect strongyloidiasis. (4) Conclusions: Probes' sequences are critical factors for differential electrochemical responses, and the D3 peptide presented the best electrochemical performance for strongyloidiasis detection, and may efficiently substitute whole antigen extracts from parasites for strongyloidiasis diagnosis in electrochemical immunosensors.

IgY antibody and human neurocysticercosis: a novel approach on immunodiagnosis using Taenia crassiceps hydrophobic antigens.

Human neurocysticercosis (NCC) is a worldwide neglected disease caused by Taenia solium metacestode and responsible for various complications and neurological disorders. This study aimed to evaluate the use of specific immunoglobulin Y (IgY) produced by laying hens immunized with a hydrophobic fraction of Taenia crassiceps metacestodes (hFTc) in NCC diagnosis. Egg yolk IgY antibodies were fractionated, purified and characterized. Enzyme-linked immunosorbent assay (ELISA) was carried out to evaluate the production kinetics and avidity maturation of anti-hFTc IgY antibodies throughout the IgY obtention process. Antigen recognition tests were carried out by Western blotting and immunofluorescence antibody test using purified and specific anti-hFTc IgY antibodies for detection of parasitic antigens of T. crassiceps and T. solium metacestodes. Sandwich ELISA was performed to detect circulating immune complexes formed by IgG and parasitic antigens in human sera. The results showed high diagnostic values (93.2% sensitivity and 94.3% specificity) for immune complexes detection in human sera with confirmed NCC. In conclusion, specific IgY antibodies produced from immunized hens with hFTc antigens were efficient to detect T. solium immune complexes in human sera, being an innovative and potential tool for NCC immunodiagnosis.

Egg yolk immunoglobulin Y as a promising tool to detect immune complexes in neurocysticercosis serum samples.

BACKGROUND: Neurocysticercosis (NCC) is a neglected tropical disease and its diagnosis is still a challenge due to non-specific manifestations. Neuroimaging techniques are used in the diagnosis of NCC, however, due to the high cost of these methods and the advantages presented in the use of immunological tests, such as ease of performance and satisfactory results, immunoassays are commonly used to detect antibodies against Taenia sp. antigens. The aim of the present study was to produce, characterize and apply specific polyclonal immunoglobulin Y (IgY) anti-Taenia crassiceps extracted from egg yolk of hens immunized with T. crassiceps metacestodes. METHODS: Indirect enzyme-linked immunosorbent assay (ELISA), avidity ELISA, immunoblotting and indirect immunofluorescence tests were performed for characterization of IgY antibodies. Diagnostic performance was verified by ELISA for immune complex detection testing 90 serum samples. RESULTS: Values of sensitivity, specificity, positive and negative likelihood ratios (LR+/LR-) and area under the curve (AUC) were calculated and presented the following results: sensitivity 83.3%, specificity 96.7%, AUC 0.966, LR+ 25.0 and LR- 0.17. CONCLUSIONS: Results of this pioneering and innovative study demonstrate that anti-T. crassiceps IgY antibodies present potential applicability and can be used as an efficient tool in human NCC serodiagnosis.

Short epitope-based synthetic peptides for serodiagnosis of human strongyloidiasis.

Strongyloidiasis is one of the major intestinal infections in humans, and a neglected tropical disease whose diagnosis still poses a challenge. We hypothesized that diagnostic tests based on short peptides containing major epitopes may represent a promising strategy to improve strongyloidiasis detection due to reduced cross-reactivity and higher sensitivity. Our aim was to evaluate two synthetic peptides selected by phage display (C10 and D3) as potential tools for serodiagnosis of strongyloidiasis, and to predict their putative antigen target. To investigate their diagnostic potential, we have tested different panels of serum samples (n=120) by enzyme linked immunosorbent assay (ELISA) to detect specific IgG, and their diagnostic parameters were calculated. Similarities with proteins from Strongyloides stercoralis were searched and conformational epitopes were predicted and aligned to known protein structures. Both C10 and D3 achieved sensitivity of 95%, and specificities were 89.2% and 92.5%, respectively. D3 presented the highest diagnostic efficiency (93.3%). Epitope prediction for both C10 and D3 led to the alignment with the cytochrome c oxidase subunit 1 structure. In brief, we propose two synthetic peptides as new biomarkers for serodiagnosis of strongyloidiasis, which can be promptly used for ELISA and in future field sensor platforms.

IgG avidity in differential serodiagnosis of human strongyloidiasis active infection.

IgG avidity assays have been developed for several parasitic diseases although there are no researches focused in strongyloidiasis diagnosis. Definitive diagnosis of strongyloidiasis is based on the presence of Strongyloides larvae in stool, but majority of cases involve low and irregular larval output. While limitations of serological assays for strongyloidiasis are well known, characteristics of persons who are misdiagnosed based on negative coproparasitological tests have been little explored. The aim of the present study was to evaluate the use of IgG avidity to detect patients with active strongyloidiasis and to characterize sources of disagreement between serology and coproparasitology. A total of 80 serum samples was analyzed, 40 from patients with Strongyloides larvae in stool (G1) and 40 from individuals with negative coproparasitology, but positive serology (G2). Serum samples were analyzed in an indirect IgG avidity ELISA using urea 6M in serial double dilutions from 1:80 to 1:2560. Avidity index (AI) was calculated to each serum dilution and analyzed as screening AI (serum dilution of 1:160) or mean AI of different serum dilutions that had a positive result. Statistical analyzes were performed by Mann-Whitney's (U) and Fisher's exact tests. At screening dilution, median of AI was 68% in G1 and 88% in G2 (P<0.0001), whereas median of mean AI in G1 was 72% and in G2 94% (P<0.0001), but there was no significant differences between both AI in each patient group. A cut off value established at AI of 75% demonstrated a significant difference between groups, with G1 sera showing AI<75% and G2 sera with AI>75% (P<0.0001). In conclusion, IgG avidity assays may distinguish active infection with Strongyloides stercoralis from suspect or serologically false positive cases.

Detergent fraction of heterologous antigen to detect IgA and IgG in strongyloidiasis using saliva and serum paired samples.

Strongyloides stercoralis causes chronic asymptomatic infections in immunocompetent human hosts and systemic invasion in immunocompromised patients, developing into a fatal hyperinfection syndrome. IgA and IgG detection in saliva and serum paired samples were tested using total saline extract from Strongyloides venezuelensis (SE(*)) and its detergent phase (D) extracted with Triton X-114. Saliva and serum paired samples were obtained from: 25 patients with confirmed strongyloidiasis; 25 patients with other parasitoses and 20 from apparently healthy individuals. Sensitivity, specificity, diagnostic efficiency, positive and negative predictive values and likelihood ratio were calculated at the optimum point of reaction. Using D phase sensitivity and specificity to detect IgA in saliva were 76.0% and 88.9% and in serum 80.0% and 86.7%, respectively. To detect IgG, D phase showed sensitivity and specificity of 88.0% and 88.9% in saliva and 88.0% and 84.4% in serum, respectively. D phase proved to be specific and efficient and could be utilized as an alternative antigen for IgA and IgG detection in saliva and serum samples for strongyloidiasis diagnosis.