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Application of Schistosome Microsomal Antigens in Immunodiagnostic Assays.

1,2Maged M Al-Sherbiny, 1,2Ahmed M Osman, 2Mohamed Abdel-Fatah, 1Ragia Charmy and 3Victor CW Tsang.

1Zoology Department, Faculty of Science, Cairo University, 2Egyptian Reference and Diagnostic Center, VACSERA, Cairo, Egypt. 3Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA.

The target of this study is to assess and evaluate the use of S.mansoni and S. haematobium microsomal antigens (MAMA and HAMA) in FAST-ELISA and EITB for immunodiagnosis of schistosomiasis and to compare their findings with those of the dipstick (DS) assay as a practical screening test for field sites. Screening of the S.mansoni-infected sera (Kafr El-Sheikh site) with FAST-MAMA and EITB-MAMA, showed sensitivity levels of 98.3% and 100%, respectively. Meanwhile, screening of these sera with DS assay, resulted in the same sensitivity as the EITB assay. Screening of S. haematobium-infected sera (Giza site) with FAST-MAMA showed a low sensitivity (80.5%) as compared to the FAST-HAMA where the sensitivity was much better, reaching 95%. About 97% of sera from parasitologically S. haematobium positive subjects sera, which were FAST-HAMA positive, recognized Gp23 in both EITB and DS assays. All participants from Giza site were parasitologically negative for S. mansoni. Sixty one percent of them were positive in FAST-MAMA and 45%-23% of them recognized Gp30 in EITB and DS assays, respectively. This lower percentage in DS assay could be a much more accurate estimation of S.mansoni antibodies in such S. haematobium endemic site. On comparing the EITB findings with that of the DS assay, the results showed that all negative sera in MAMA and HAMA blots were also negative in the DS assay. Ninety six percent of the positive HAMA blots were also positive in DS assay indicating nearly the same sensitivities of the two assays for Gp23 reactivity. About fifty two percent of the mixed infection sera, which weakly recognized Gp30 in MAMA blots, were totally negative in DS assay thus indicating the purity and specificity of the DS-assay antigen is much higher than that used in EITB. DS assay is sensitive, specific, reproducible and highly effective in screening patients with either schistosome infections. Also, DS assay is economic, rapid and lends itself for use under field conditions.