A T‐cell diagnostic test for cystic echinococcosis based on Antigen B peptides

Abstract

SummaryCystic echinococcosis (CE) immunodiagnosis is still imperfect. We recently set‐up a whole‐blood test based on the interleukin (IL)‐4 response to the native Antigen B (AgB) of Echinococcus granulosus. However, AgB is encoded by a multigene family coding for five putative subunits. Therefore, the aims of this study were to analyse the IL‐4 response to peptides spanning the immunodominant regions of the five AgB subunits and to evaluate the accuracy of this assay for CE diagnosis. Peptides corresponding to each subunit were combined into five pools. A pool containing all peptides was also used (total pool). IL‐4 evaluated by enzyme‐linked immunosorbent assay was significantly higher in patients with CE compared to those without (NO‐CE subjects) when whole‐blood was stimulated with AgB1 and with the total pool. Moreover, IL‐4 levels in response to the total pool were significantly increased in patients with active cysts. Receiver Operator Curve analysis identified a cut‐off point of 0.59 pg/mL predicting active cysts diagnosis with 71% sensitivity and 82% specificity in serology‐positive CE patients. These data, if confirmed in a larger cohort, offer the opportunity to develop new diagnostic tools for CE based on a standardized source of AgB as the peptides.

Species specificity preliminary evaluation of an IL‐4‐based test for the differential diagnosis of human echinococcosis

“…In conclusion, our preliminary data show that the IL-4 whole-blood test is a promising assay to rule out AE in case of test positivity, in the context of a differential diagnosis with CE. This finding, combined with its potential usefulness in discriminating active from inactive CE stages 11,12 and the possibility to standardize the test, underscores this assay's potential to further improve the diagnosis of CE.…”

“…[17][18][19][20][21][22] In this context, we recently set up an immune-based test measuring the IL-4 production after stimulating whole blood with an enriched fraction of antigen B (AgB-the most abundant antigen of HCF) or AgB peptides. 11,12 In this whole-blood test, higher levels of IL-4 associated with CE infection (71.4% sensitivity, 93.3% specificity) and with the presence of active cysts (84.6% sensitivity, 92% specificity). 12 However, cross-reactivity with AE has not been tested.…”

“…Cytokines have been considered the basis of potential tools for the diagnosis and clinical management of CE, and associations between cytokine responses and some clinical features have been reported . In this context, we recently set up an immune‐based test measuring the IL‐4 production after stimulating whole blood with an enriched fraction of antigen B (AgB—the most abundant antigen of HCF) or AgB peptides . In this whole‐blood test, higher levels of IL‐4 associated with CE infection (71.4% sensitivity, 93.3% specificity) and with the presence of active cysts (84.6% sensitivity, 92% specificity) .…”

“…[7][8][9] Several approaches, such as the use of different sources of antigens and different readout systems, have been attempted to overcome the serology shortfalls. [9][10][11][12][13][14] The most commonly used serological tests for human CE are based on the detection of IgG antibodies against E granulosus hydatid cyst fluid (HCF). These tests show an 80%-99% sensitivity with variable specificity (60%-97%), while tests detecting IgG against purified or recombinant antigens show a better specificity (80%-100%) but lower sensitivity (38%-93%).…”

Detection of Echinococcus granulosus sensu lato infection by using extracts derived from a protoscoleces G1 cell line

“…Alternative methods to improve serological diagnosis of CE have thus been proposed. These include: evaluation of interleukin levels, antibody class change, antigen identification and purification from freshly extracted metacestodes and the use of antigenic recombinant proteins or fusion proteins assayed in infected animals in immunodiagnostic assays.…”