title: Immunodiagnosis of Strongyloides stercoralis infection: a method for increasing the specificity of the indirect ELISA.
abstract: Indirect enzyme-linked immunosorbent assay (ELISA) allows sensitive detection of serum immunoglobulin (Ig) G against a soluble extract of Strongyloides stercoralis infective larvae. In this study, 40/40 (100%) human strongyloidiasis sera had high levels of anti-S. stercoralis IgG, but 30/40 (75%) filariasis sera, and 12/40 (30%) necatoriasis sera also had higher levels than control sera from UK residents. In attempts to increase the assay specificity by absorption of cross-reactive IgG, the effectiveness of pre-incubation of sera with extracts of different parasitic nematodes was investigated. One hour of incubation with 20 micrograms/ml aqueous extract of Onchocerca gutturosa absorbed cross-reactive IgG in most filariasis and necatoriasis sera, reducing the proportion with IgG levels above the positivity threshold by more than one-half. Preliminary results suggest that absorption with extracts of other filarial nematodes is equally effective, and that some of the cross-reactive IgG is directed against phosphorylcholine. Cross-reactive IgG in most necatoriasis sera was effectively absorbed with 20 micrograms/ml extract of Necator americanus. Cross-reactive IgG was not effectively absorbed with an extract of Ascaris lumbricoides. Absorption of cross-reactive IgG is an effective means of increasing the specificity of the indirect ELISA, for use in the immunodiagnosis and immuno-epidemiology of S. stercoralis infection.
authors.affiliation: Wellcome Trust Research Centre for Parasitic Infections, Department of Biology, Imperial College, London, UK.
authors.forename: D J
authors.initials: DJ
authors.lastname: Conway
authors.forename: N S
authors.initials: NS
authors.lastname: Atkins
authors.forename: J E
authors.initials: JE
authors.lastname: Lillywhite
authors.forename: J W
authors.initials: JW
authors.lastname: Bailey
authors.forename: R D
authors.initials: RD
authors.lastname: Robinson
authors.forename: J F
authors.initials: JF
authors.lastname: Lindo
authors.forename: D A
authors.initials: DA
authors.lastname: Bundy
authors.forename: A E
authors.initials: AE
authors.lastname: Bianco
mesh_terms: D000042:Absorption; D000818:Animals; D000909:Antibodies, Helminth / Q000032:analysis; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis; D009348:Nematoda / Q000276:immunology; D012680:Sensitivity and Specificity; D017171:Strongyloides stercoralis / Q000276:immunology; D013322:Strongyloidiasis / Q000175:diagnosis*
chemical_list: D000909:Antibodies, Helminth; D007074:Immunoglobulin G