Schistosoma mansoni egg specific antibodies and circulating antigens: assessment of their validity in immunodiagnosis of schistosomiasis.

A total of 127 individuals of different age and sex; 92 from Kafr-Sendewa, Qualyobia Governorate, Egypt, in comparison to 23 cases with hydatidosis and fascioliasis as a parasitic control group, and 12 healthy control group from non-endemic area. All cases were screened by clinical examination, urine, stool, rectal snip, abdominal ultrasonographic examination and indirect haemagglutination test (IHAT). Accordingly, they were grouped into active intestinal schistosomiasis group, seropositive group by (IHAT), normal control group from the same endemic area, parasitic control group and normal control group. All cases were subjected to detection of IgG, IgM, IgG4, anti-soluble egg antigen (SEA) and anti-excretory-secretory egg antigen (ESEA) by ELISA tests; and circulating egg antigens by double-sandwich ELISA techniques. The results showed that IgG4 anti-SEA is the best diagnostic test, as it gave the best diagnostic efficacy (90%). Also, it is a good screening test which can be used in endemic area as it gave significant difference between the active intestinal schistosomiasis cases with each of the endemic control group (P < 0.001) and the seropositive cases (P < 0.05). Other valid diagnostic egg specific antibodies tests were IgM anti-SEA and IgG anti-SEA as their diagnostic efficacy were 80% and 76.6% respectively (P < 0.05). The diagnostic efficacy of circulating antigen detection (C.Ag) test was 70% (P < 0.05). In addition, it was the most specific test with 100% specificity. IG4-anti-ESEA gave the least cross-reaction with other parasites (17.3%). The mean optical density (OD) level of circulating antigen detection test was significantly higher in the organomegalic (hepatosplenomegaly) cases than the non-organomegalic cases (P < 0.05).

Detection of circulating anodic antigen before and after specific chemotherapy in experimental murine Schistosomiasis mansoni.

In two groups of mice infected with 60 (group I) and 120 (group II) Schistosoma mansoni cercariae, respectively, the effects of intensity and duration of infection, and of praziquantel therapy (curative vs subcurative dose) on the levels of circulating anodic antigen (CAA), were studied. CAA was measured in trichloracetic acid-treated serum samples with an avidin-biotin enzyme-linked immunosorbent assay (AB-ELISA) using the monoclonal anti-CAA antibody. Total worm burdens, oogram patterns and ova counts/g liver and intestine were followed up. The lowest detectable level of CAA was about 1.0 ng/ml, and was positive with a worm load of 3-5/mouse. CAA levels became already detectable as early as 1-2 weeks post-infection (pi) before any parasitological parameter and showed a significant drop from the 11th-12th week pi onwards. A positive correlation was demonstrated between the CAA level and worm load. Following successful praziquantel therapy, CAA disappeared earlier than any of the other parameters studied.