Improved Diagnosis of Strongyloides stercoralis Using Recombinant Antigen-Based Serologies in a Community-Wide Study in Northern Argentina

Abstract

The serodiagnosis of Strongyloides stercoralis infection by enzyme-linked immunosorbent assays based on crude antigen (CrAg-ELISA), while useful, has been limited by the reliance on crude parasite extracts. Newer techniques such as the luciferase immunoprecipitation system assay (LIPS), based on a 31-kDa recombinant antigen (termed NIE) from S. stercoralis and/or the recombinant antigen S. stercoralis immunoreactive antigen (SsIR), or the NIE-ELISA have shown promise in controlled settings. We compared each of these serologic assays in individuals from both regions of the world in which S. stercoralis is endemic and those in which it is not. A comprehensive stool evaluation (sedimentation concentration, Baermann concentration with charcoal cultures, agar plate, and Harada-Mori) and four different serologic techniques using CrAg-ELISA or recombinant NIE-ELISA as well as LIPS using NIE alone or in combination with a second recombinant antigen (NIE/SsIR-LIPS) were compared among individuals with parasitologically proven infection (n ‫؍‬ 251) and healthy controls from regions of the world in which the infection is nonendemic (n ‫؍‬ 11). Accuracy was calculated for each assay. The prevalence of S. stercoralis infection was 29.4% among Argentinean stool samples (n ‫؍‬ 228). Sedimentation concentration and Baermann were the most sensitive stool-based methods. NIE-LIPS showed the highest sensitivity (97.8%) and specificity (100%) of the serologic assays. The calculated negative predictive value was highest for both the NIE-LIPS and CrAg-ELISA (>97%) irrespective of disease prevalence. No cross-reactivity with soil-transmitted helminths was noted. NIE-LIPS compares favorably against the current CrAg-ELISA and stool evaluation, providing additional accuracy and ease of performance in the serodiagnosis of S. stercoralis infections irrespective of disease prevalence.

The laboratory diagnosis of Strongyloides stercoralis

“…No definitive study of serological methods has been conducted to date, and much of the available data is subject to flaws in methodology, particularly the use of microscopy only as a reference and a S. stercoralis crude antigen extract ELISA (97%) 18 . All assays tested showed 100% specificity in this study 15 . A more recent study compared an in-house crude S. stercoralis filariform larvae immunofluorescent antibody test (IFAT) with the ELISAs from IVD Research, Bordier, and a recombinant antigen NIE ELISA and LIPS 14 .…”

“…Two commercial ELISA kits employing somatic antigens are available from BORDIER (Strongyloides ratti antigen) and IVD Research (S. stercoralis antigen), respectively 14 . Recently, two recombinant antigens (32 kD recombinant antigen, called NIE and S. stercoralis immmunoreactive antigen, SsIR) have been employed for serological testing in both ELISA and luciferase immunoprecipitation system assay (LIPS) platforms 15 . The reported sensitivity and specificity of various serological platforms ranges from 56-100% and 29-100%, dependent upon the method, antigens, cut-offs, study populations, and reference methods employed 16 .…”

Prevalence of Strongyloides stercoralis and other intestinal parasitic infections among mentally retarded residents in central institution of southern Iran

“…Serological methods can reveal light infections in asymptomatic individuals and should be used for further studies among those population [11,15,32] and in order to achieve real prevalence, screening procedures must be applied.…”

“…Moreover, asymptomatic infection can remain for decades due to the occurrence of several auto infection cycles [15,17] .…”

“…It is estimated that over 1 billion people are infected with STH and 30-100 millions with S. stercoralis worldwide [7,[11][12][13][14] . S. stercoralis's unique life cycle makes it possible to survive in human host and causes autoinfection to lead chronic disease which could have remained for several years [13][14][15] . Although most of infections are asymptomatic, disseminated and hyper infection may occur in immunocompromised and immune deficient individuals as a fatal disease [16][17][18][19][20] .…”