RESUMO
Forty-one-, 31-, and 28-kDa proteins of strongyloides stercoralis filariform larvae have previously been demonstrated to be sensitively and specifically recognized by serum IgG in individuals with strongyloidiasis. Characteristics of these proteins, their immunodominant epitopes, and reactive antibodies are described here. The proteins are soluble is aqueous as well as detergent extracts. The immunodominant epitopes are present in S. stercoralis but not in S. cebus or S. ratti. Epitopes on the three proteins are not shared, as determined by cross-absorption of serum with each of the size components on nitrocellulose. In most sera from strongyloidiasis patients there was reactivity to each of the proteins by IgG1 and IgG4, but reactivity by IgG2 or IgG3 was detectable only in a minority. A rabbit antiserum raised to a 41-kDa size fraction of S. stercoralis larvae reacted against a doublet of 41-kDa which was distinct from the immunodiagnostic 41-kDa protein.(AU)
Assuntos
Anticorpos Anti-Helmínticos/biossíntese , Anticorpos Anti-Helmínticos/diagnóstico , Epitopos Imunodominantes/análise , Strongyloides stercoralis/imunologia , Estrongiloidíase/diagnóstico , Anticorpos Anti-Helmínticos/sangue , Anticorpos Anti-Helmínticos/imunologia , Western Blotting , Eletroforese em Gel de Poliacrilamida , Imunoglobulina G/biossíntese , Imunoglobulina G/sangue , Soros Imunes/imunologia , Epitopos Imunodominantes/química , Epitopos Imunodominantes/imunologia , Larva/imunologia , Peso Molecular , Onchocerca/imunologia , Coelhos , Solubilidade , Especificidade da Espécie , Strongyloides ratti/imunologia , Estrongiloidíase/imunologiaRESUMO
Recently described enzyme-linked immunosorbent assay (ELISA) and immunoblot methods for the detection of serum IgG against Strongyloides stercoralis larval antigens were prospectively evaluated for the diagnosis of endemic strongyloidiasis. A modification of the ELISA involved preincubation of sera with Onchocerca gutturosa phosphate-buffered saline-soluble extract to remove cross-reactivity with other helminths. The sensitivity of the ELISA increased from 80 percent and 85 percent following preincubation. Similarly, there was an increase in specifity from 94 percent to 97 percent. The IgG recognition of 41-, 31-, and 28-kD filariform larval components showed sensitivities of 100 percent, 85 percent and 65 percent, respectively. Both the ELISA following incubation of sera with O. gutturosa extract and serum IgG reactivity to a 41-kD larval component using immunoblotting are sensitive and specific techniques for diagnosing endemic strongyloidiasis.(AU)
Assuntos
Anticorpos Anti-Helmínticos/sangue , Ensaio de Imunoadsorção Enzimática , Immunoblotting , Strongyloides stercoralis/imunologia , Estrongiloidíase/diagnóstico , Antígenos de Helmintos/imunologia , Reações Cruzadas , Estudo de Avaliação , Reações Falso-Positivas , Fezes/parasitologia , Imunoglobulina G/sangue , Larva/imunologia , Onchocerca/imunologia , Estudos Prospectivos , Sensibilidade e EspecificidadeRESUMO
Proteins from a deoxycholate-soluble extract of Strongyloides stercoralis infective larvae were separated by SDS-PAGE, blotting onto nitrocellulose paper, and reacted with sera from individuals with confirmed S. stercoralis infections (n = 100), suspectedS. stercoralis infections in whom no larvae could be detected (n = 27), and other nematode infections (40 with Wuchereria bancrofti, 20 with Onchocerca volvulus, 20 with Necator americanus, and 20 with mixed Ascaris lumbricoides and Trichuris trichiura infections). Immunodominant proteins of approximately 41, 31, and 28 kDa were recongnized by IgG in 91 percent, 88 percent and 90 percent respectively, of sera from those with confirmed strongyloidiasis; in 100 percent, 100 percent, and 93 percent of sera from those with suspected strongyloidiasis; and in 9 percent, 12 percent and 14 percent of sera from those infected with other nematodes. IgG reactivity to each of these proteins was a more specific means of immunodiagnosis than the currently use indirect ELISA; the methods were equally sensitive.(AU)
Assuntos
Anticorpos Anti-Helmínticos/sangue , Antígenos de Helmintos/imunologia , Imunoglobulina G/sangue , Strongyloides stercoralis/imunologia , Estrongiloidíase/diagnóstico , Western Blotting , Reações Cruzadas , Ensaio de Imunoadsorção Enzimática , Larva/imunologia , Sensibilidade e EspecificidadeRESUMO
Strongyloides stercoralis is the most serious intestinal nematode infecting humans in the Caribbean. The parasite is, however, difficult to diagnose using standard laboratory techniques, especially in sub-clinical cases. An ELISA, using PBS extracts of filariform larvae as antigen, and a Western Blot method were evaluated in the Jamaican community. Sensitivity and specificity of the ELISA were 73 per cent and 93 per cent (n=135) respectively. Pre-incubation of sera with Onchocerca gutterosa (Filariata) antigen increased sensitivity and specificity of the ELISA to 82 per cent and 97 per cent, respectively. Similarly, The Western Blot which was based on IgG recognition of proteins of 41kD and one of 31kD or 28kD detected 82 per cent of infected individuals and 97 per cent of true negatives. There was no notable cross-reactivity by either ELISA or Western Blot with Ascaris, Trichuris or hookworm, also common to the Region. ELISA proved to be a sensitive and specific test for diagnosing S. stercoralis infection in Jamaica. Western Blotting had no significant merits over those of ELISA although it confirmed the presence of 3 immunodominant bands which may play a role in future immunodiagnosis. Furthermore, it adds to the battery of sensitive serological tests available to clinicians who have to decide on the infection status of potential S. stercoralis patients who are about to receive immuno-suppressive therapy (AU)
Assuntos
Humanos , Estrongiloidíase/diagnóstico , Ensaio de Imunoadsorção Enzimática , Western BlottingRESUMO
Indirect enzyme-linked immunosorbent (ELISA) allows sensitive detection of serum immunoglobulin (Ig) G against a soluble extract of Strongyloides stercoralis infective larvae. In this study, 40/40 (100 percent) human strongyloidiasis sera had high levels of anti-S. stercoralis IgG, but 30/40 (75 percent) filariasis sera, and 12/40 (30 percent) necartoriasis 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 æ/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 one-half. Preliminary results suggest that absorption with extracts of other filarial nematodes is equally effective, and that some cross-reactive IgG is directed against phosphorylcholine. Cross-reactive IgG in most necatoriasis sera was 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.
Assuntos
Humanos , Strongyloides/parasitologia , Testes Imunológicos/métodos , Ensaio de Imunoadsorção EnzimáticaRESUMO
This study examines the age-dependency of the relationships between human infection with whipworm (Trichuris trichiura) and parasite-specific antibody level measured by ELISA against an extract of adult worms after preincubation of the sera with Ascaris lumbricoides adult worm extract. The convex age-profile of parasite infection intensity is shown to be mirrored by age-dependent change in age-class mean levels of IgG (all subclasses except IgG3), IgA, IgM and IgE. Mean antibody levels rise with increasing acquisition of infection in childhood. Immunoblot analysis of selected sera from different age-classes indicates that antigen recognition is similarly dependent on infection intensity. In individual children, antibody levels correlate positively with acquisition of infection, consistent with a simple model of antigen dosage specifying the magnitude of the humoral immune response. In adults, IgG4 correlates positively and IgA negatively with intensity of infection, suggesting involvement of these isotypes in functional roles of immune blockade or effector mechanisms, respectively.(AU)