Detection of the Sm31 antigen in sera of Schistosoma mansoni- infected patients from a low endemic area.
Schistosoma mansoni cathepsin B (Sm31) is a major antigen from adult worms that circulates in the blood of infected patients (Li et al., Parasitol Res 1996; 82: 14-18). An analysis of the Sm31 sequence (Klinkert et al., Mol Biochem Parasitol 1989; 33: 113-122) allowed the prediction of seven hydrophilic regions that were confirmed to be exposed on the surface of a 3D model of Sm31; the species specificity of these regions was checked using BLAST analysis. The corresponding peptides were chemically synthesized in polymerazible forms using the t-Boc technique. Rabbits developed a high humoral response against these peptides as tested by a multiple antigen blot assay; it recognized native Sm31 in crude S. mansoni extracts and as circulating antigen in sera of S. mansoni-infected patients by western blot. Relevant antigenic determinants were located at the N- and C-terminus sequences. Antibodies against these regions recognized the native enzyme in an ELISA-like assay called cysteine protease immuno assay in which the immunocaptured enzyme was revealed by the intrinsic cathepsin B hydrolytic activity of Sm31. The method successfully and specifically detected Sm31 in sera of infected individuals, most of them (83.3%) with light infections, offering a rationale for the development of parasite enzyme capture assays using anti-synthetic peptide antibodies for possible use in the diagnosis of schistoso,iasis.
Sulbarán
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GS
Unidad de Trematodiasis, Centro de Microbiología y Biología Celular, Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela.
Ballen
D E
DE
Bermúdez
H
H
Lorenzo
M
M
Noya
O
O
Cesari
I M
IM
D000595:Amino Acid Sequence; D000818:Animals; D000909:Antibodies, Helminth / Q000276:immunology; D000947:Antigens, Helminth / Q000097:blood* / Q000276:immunology; D003546:Cysteine Endopeptidases / Q000097:blood* / Q000138:chemical synthesis / Q000276:immunology; D019353:Endemic Diseases; D015801:Helminth Proteins / Q000097:blood* / Q000138:chemical synthesis / Q000276:immunology; D006801:Humans; D007118:Immunoassay; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D011817:Rabbits; D012550:Schistosoma mansoni / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D012555:Schistosomiasis mansoni / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology* / Q000276:immunology; D012680:Sensitivity and Specificity; D013045:Species Specificity; D014687:Venezuela / Q000453:epidemiology
D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D015801:Helminth Proteins; D003546:Cysteine Endopeptidases; C059747:Sm31 protein, Schistosoma mansoni