Evaluation of larval surface antigens from infective larvae of Strongyloides venezuelensis for the serodiagnosis of human strongyloidiasis

Abstract

Serodiagnosis of strongyloidiasis is usually performed by ELISA for the detection of IgG antibodies due to its high sensitivity and practicality, but its main limitation is a constant source of S. stercoralis antigens. The use of S. venezuelensis as a heterologous source of antigens has facilitated several published studies on the serodiagnosis and epidemiology of human strongyloidiasis. The main objective of this study was to evaluate the diagnostic accuracy of surface cuticle antigens of infective larvae of S. venezuelensis extracted with CTAB detergent (L3-CTAB) in comparison with soluble somatic extracts (L3-SSE) using a panel of sera from immunocompetent and immunocompromised individuals, at three different cut-offs. ROC curve analysis showed that L3-CTAB had an AUC of 0.9926. At the first cut-off value (OD 450 nm = 0.214), sensitivity and specificity were 100% and 90.11%, respectively, with a diagnostic accuracy of 0.93. At a second cut-off value (OD 450 nm = 0.286), sensitivity and specificity were 70% and 100%, respectively, with a diagnostic accuracy of 0.91. However, at an alternative third cut-off value (OD 450 nm = 0.589), sensitivity and specificity were 95% and 97.8%, respectively, with a diagnostic accuracy of 0.97. Using L3-CTAB as an antigenic source, the seropositivity rate in immunocompromised patients was 28.13% (9/32) whereas a seropositivity rate of 34.38% (11/32) was found when L3-SSE was used in ELISA. Therefore, the L3-CTAB is simple and practical to obtain and was found to be highly sensitive and specific.

Seroprevalence and associated risk factors of strongyloidiasis in indigenous communities and healthcare professionals from Brazil

“…The test has been based on the heterologous extract of S . venezuelensis (CTABL3), with cut-off, sensitivity, and specificity values of 0.286, 95% and 97.8%, respectively, as already established (Gomes et al 2022) [ 33 ]. Positive serum samples for S .…”

“…ELISA for detection of IgG antibodies was based on an established protocol used for research and daily routine use at the Clinical Hospital, School of Medicine, University of São Paulo [ 33 ]. Briefly, commercial 96-well flat bottom microtitration polystyrene plates (Costar, Sigma-Aldrich Chemical Co., St. Louis, MO, USA) were coated (100 μL/well) with the antigenic extracts at a concentration of 10 μg/mL, diluted in carbonate-bicarbonate buffer (0.06 M, pH 9.6), and incubated overnight at 4°C.…”

“…The ELISA used herein has shown 95.0% sensitivity and 97.8% specificity, and 0.286 cut off [ 33 ]. Diagnostic parameters were determined by the ROC curve, using serum samples that were parasitologically positive for S .…”

“…Diagnostic parameters were determined by the ROC curve, using serum samples that were parasitologically positive for S . stercoralis , negative, and positive for other parasites, as previously described [ 33 ]. All assays were monitored by including positive (pool of positive serum samples for S .…”