RESUMEN
Strongyloides stercoralis is a soil-transmitted nematode that can cause life-threatening conditions in immunocompromised persons. In the United States, strongyloidiasis should be considered mainly in immigrants, refugees, or travelers. The confirmatory laboratory diagnosis is usually performed by detecting larvae from the stool, duodenal material, and sputum. In persons who are immunocompromised with severe strongyloidiasis, adult worms and eggs can be detected from duodenal material. For serological diagnosis, most assays use crude antigens to detect anti-S. stercoralis IgG. Recently, recombinant proteins such as rSs-NIE-1 and rSs-IR have been used to detect IgG antibodies. We used rSs-NIE-1 and rSs-IR recombinant antigens to develop a biplex Western blot assay to detect the IgG4 antibody in individuals with strongyloidiasis. The sensitivities of rSs-NIE-1 and rSs-IR were 97.4% and 90.8%, respectively, whereas the specificities were 97.6% and 98%, respectively. In conclusion, the biplex rSs-NIE-1 and rSs-IR immunoblot performs well in detecting IgG4 antibody in S. stercoralis-infected persons.
Asunto(s)
Anticuerpos Antihelmínticos/sangre , Antígenos Helmínticos/inmunología , Immunoblotting/métodos , Strongyloides stercoralis/inmunología , Estrongiloidiasis/diagnóstico , Animales , Antígenos Helmínticos/genética , Heces/parasitología , Humanos , Immunoblotting/normas , Inmunoglobulina G/sangre , Larva/inmunología , Proteínas Recombinantes/inmunología , Sensibilidad y Especificidad , Strongyloides stercoralis/química , Estrongiloidiasis/inmunologíaRESUMEN
BACKGROUND: Strongyloidiasis, a human intestinal infection caused by the nematode Strongyloides stercoralis, is frequently underdiagnosed and although its high prevalence is still a neglected parasitic disease because conventional diagnostic tests based on parasitological examination (presence of Strongyloides larvae in stool) are not sufficiently sensitive due to the low parasitic load and to the irregular larval output. There is an urgent need to improve diagnostic assays, especially for immunocompromised patients with high parasitic load as consequence of self-infection cycle, which can disseminate throughout the body, resulting in a potentially fatal hyperinfection syndrome often accompanied by sepsis or meningitis. METHODS/PRINCIPAL FINDINGS: We have performed Phage Display technology to select peptides that mimic S. stercoralis antigens, capable of detecting a humoral response in patients with strongyloidiasis. The peptides reactivity was investigated by Phage-ELISA through different panels of serum samples. We have successfully selected five peptides with significant immunoreactivity to circulating IgG from patients' sera with strongyloidiasis. The phage displayed peptides C9 and C10 presented the highest diagnostic potential (AUC>0.87) with excellent sensitivity (>85%) and good specificity (>77.5%), suggesting that some S. stercoralis antigens trigger systemic immune response. CONCLUSIONS/SIGNIFICANCE: These novel antigens are interesting serum biomarkers for routine strongyloidiasis screenings due to the easy production and simple assay using Phage-ELISA. Such markers may also present a promising application for therapeutic monitoring.
Asunto(s)
Antígenos Helmínticos , Parasitología/métodos , Péptidos , Strongyloides stercoralis/inmunología , Estrongiloidiasis/diagnóstico , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Animales , Anticuerpos Antihelmínticos/sangre , Antígenos Helmínticos/inmunología , Bacteriófagos , Ensayo de Inmunoadsorción Enzimática/métodos , Femenino , Humanos , Inmunoglobulina G/sangre , Masculino , Persona de Mediana Edad , Biblioteca de Péptidos , Péptidos/inmunología , Sensibilidad y Especificidad , Strongyloides stercoralis/química , Estrongiloidiasis/inmunología , Adulto JovenRESUMEN
Host-seeking behavior by parasitic nematodes relies heavily on chemical cues emanating from potential hosts. Nonspecific cues for Strongyloides stercoralis, a nematode that infects humans and a few other mammals, include carbon dioxide and sodium chloride; however, the characteristic species specificity of this parasite suggested the existence of other, more specific cues. Here we show that the infective larva of S. stercoralis is strongly attracted to an extract of mammalian skin and that the active component in this skin extract is urocanic acid. Urocanic acid, a histidine metabolite, is particularly abundant in mammalian skin and skin secretions, suggesting that it serves as an attractant specific to mammalian hosts. The attractant activity of urocanic acid is suppressed by divalent metal ions, suggesting a possible strategy for preventing infection.
Asunto(s)
Factores Quimiotácticos/química , Interacciones Huésped-Parásitos , Parásitos/metabolismo , Piel/parasitología , Strongyloides stercoralis/metabolismo , Ácido Urocánico/farmacología , Animales , Quimiotaxis , Cromatografía , Perros , Relación Dosis-Respuesta a Droga , Histidina/química , Iones , Metales/química , Strongyloides stercoralis/química , Factores de Tiempo , Ácido Urocánico/metabolismoRESUMEN
The World Health Organization is sponsoring major treatment programs with the aim of controlling helminth infection throughout the tropical world. Prominent among the anthelmintics recommended for use in these programs are drugs in the benzimidazole (BZ) class. Resistance to these drugs has been associated with polymorphisms in the beta-tubulin gene. We have cloned and sequenced the beta-tubulin genes of Strongyloides stercoralis and Strongyloides ratti and have proceeded to develop a protocol for genotyping single worms for polymorphisms in beta-tubulin. Our findings indicate that S. ratti has a single beta-tubulin gene, making DNA sequence analysis of a single larva PCR product a feasible means of studying BZ resistance in these species. Our genotyping test allows the identification of polymorphisms at codons 167, 198, and 200 in the Strongyloides beta-tubulin gene, thus enabling survey for BZ resistant genotypes.
Asunto(s)
ADN Complementario/química , ADN de Helmintos/química , Strongyloides ratti/genética , Strongyloides stercoralis/genética , Tubulina (Proteína)/genética , Regiones no Traducidas 3' , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Bencimidazoles/farmacología , Southern Blotting , Clonación Molecular , Cartilla de ADN/química , Resistencia a Medicamentos/genética , Electroforesis en Gel de Agar , Genotipo , Humanos , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa , Polimorfismo Genético , ARN de Helminto/genética , Ratas , Ratas Wistar , Alineación de Secuencia , Strongyloides ratti/química , Strongyloides ratti/clasificación , Strongyloides ratti/efectos de los fármacos , Strongyloides stercoralis/química , Strongyloides stercoralis/clasificación , Strongyloides stercoralis/efectos de los fármacos , Tubulina (Proteína)/químicaRESUMEN
Two G protein alpha subunit genes orthologous to gpa-2 and gpa-3 in Caenorhabditis elegans have been identified in the parasitic nematode, Strongyloides stercoralis. These genes mediate chemosensory signal transduction regulating dauer arrest in C. elegans. In the parasite, they represent candidate mediators for regulation of the choice between free-living and parasitic life cycles, the obligatory developmental arrest of infective larvae, and reactivation of development after infection. The (A+T) content of these genes is 72.2% for coding sequences, 90% for introns, and 84.1% for 5' and 3' flanking regions, requiring the use of low extension temperatures for long distance PCR. The possible significance of conserved structural motifs of these proteins is discussed.