Effectiveness of Strongyloides Recombinant IgG Immunoreactive Antigen in Detecting IgG and IgG4 Subclass Antibodies for Diagnosis of Human Strongyloidiasis Using Rapid Immunochromatographic Tests

Abstract

Human strongyloidiasis is an important soil-transmitted helminthiasis that affects millions worldwide and can develop into fatal systemic strongyloidiasis in immunosuppressed patients. We have developed two new rapid and simple-to-use immunochromatographic test (ICT) kits for rapid serodiagnosis that support stool examination for clinical diagnosis. Strongyloides stercoralis recombinant IgG immunoreactive antigen (GenBank: AAB97359.1; rSsIR-based ICT kit) was used for detection of IgG and IgG4 antibodies. The diagnostic efficacy of both kits was evaluated using human serum samples from strongyloidiasis patients, healthy individuals, and those with other parasitosis. At a prevalence of infection of 36.4%, the diagnostic sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the rSsIR-based IgG ICT kit were 91.7%, 83.8%, 76.4%, 94.6%, and 86.7%, respectively, and those of the rSsIR-based IgG4 ICT kit were 78.3%, 84.8%, 74.6%, 87.3%, and 82.4% respectively. The concordance between the two kits was 89.7%. The recombinant antigen can be produced to an unlimited extent and the kits can be used as point-of-care diagnostic tools and in large-scale surveys in endemic areas throughout tropical regions without necessitating additional facilities or ancillary supplies.

The accuracy of a recombinant antigen immunochromatographic test for the detection of Strongyloides stercoralis infection in migrants from sub-Saharan Africa

“…However, studies comparing the IgG and the IgG4 formats of different assays for S. stercoralis diagnosis (including ELISAs, LIPS and another lateral flow cassette test), showed that the sensitivity of the IgG4 assay was dramatically lower than that of the IgG formats [ 11 , 21 , 22 ]. An ICT based on the recombinant antigen SsIR [ 23 ] showed 91.7% and 73.8% sensitivity with the IgG and IgG4 kits, respectively, while the specificity values were almost the same. Since the use of recombinant antigens is thought to produce more specific results than the use of crude antigens [ 11 ], an ICT that detects IgG would probably have the benefit of better sensitivity while retaining good specificity.…”

Strongyloides stercoralis: A Neglected but Fatal Parasite

“…Our indirect IgG-ELISA diagnosis of strongyloidiasis, prepared from a modified molecular weight cut-off antigen, yielded a sensitivity and specificity of 96% and 94%, respectively, in immunocompetent hosts, and 42.9% and 96.3%, in immunocompromised hosts [ 27 , 28 ]. Recently, several sensitive and specific point-of-care serological tests for strongyloidiasis were developed and showed sensitivities and specificities of 91.3–93.3% and 83.8–100%, respectively [ 29 , 30 , 31 ]. The rapid point-of-care test also worked well in a field study, with 82% sensitivity and 96% specificity [ 32 ].…”

Comparison of Two Serological Assays in Detecting Strongyloides Infection in Immunocompromised Patients

“…9 Recently, there have been two reports on IgG4-based prototype lateral-flow dipstick rapid tests for strongyloidiasis. 10,11 One of them, SsRapid, lined with S. stercoralis recombinant NIE (rNIE) protein, showed good diagnostic value. 11,12 Hence, the present study assessed the concordance between a commercial IgG-ELISA and SsRapid.…”