Detection of the Sm31 antigen in sera of Schistosoma mansoni– infected patients from a low endemic area

Abstract

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.

Assessment of the diagnostic efficacy of enolase as an indication of active infection of Schistosoma japonicum

“…Evidently, a protein present at high abundance in the Sj ESA should exist at a high concentration in the serum of schistosomiasis patients. Thus, proteomics could select highly abundant protein molecules in the Sj ESA as optimized targets for detection methods, and these methods would improve the specificity and sensitivity of detection of circulating antigens (Liu et al 1988;Sulbarán et al 2010;Shen et al 2000). In this study, we determined that the most abundant protein in the Sj ESA was Sj enolase.…”

Evaluation of an IgY-Based Immunomagnetic Enzyme-Linked Immunosorbent Assay System for Detection of Circulating Schistosoma japonicum Antigen in Serum Samples from Patients in China

“…Many immunologic tests based on antigen detection 27,28 and molecular or proteomic diagnostic techniques 29,30 have been well studied and described. However, an affordable, easy-tohandle, sensitive and specific method is not yet available.…”

Advances in the Diagnosis of Human Schistosomiasis

“…Furthermore, recent mass spectrophotometry-based studies detected multiple antigenic proteins of S. mansoni, including annexin, major egg antigen, and troponin T, and highlighted the possibility of using these components in improved diagnostic tests for schistosomiasis (279). In addition, cathepsin B (Sm31) from S. mansoni adult worms has shown promise as a useful serum diagnostic marker (280,281). Other schistosome proteins and antigens from different life cycle stages which may be of value as diagnostic markers include protease inhibitors, such as ␣ macroglobulin, a serpin, the MEG 2 and 3 egg secretory proteins, and the 18-kDa, 31/32-kDa, 38-kDa, Sm29, and Sm21.7 proteins (282)(283)(284).…”