Sensitive and specific assay for detecting circulating antigens in individuals infected with Schistosoma mansoni.

Monoclonal antibody 128C3/3/21 in an antigen-capture ELISA was used to detect circulating antigen in individuals infected with Schistosoma mansoni. This antibody recognizes a carbohydrate epitope expressed on the major group of acidic egg glycoproteins and on glycoproteins and glycolipids in all other stages of parasite development. The overall sensitivity of the assay was 78%, with a sensitivity of 100% for patients excreting >100 egg/g feces (EGF) and 72% for those excreting <100 EGF. By increasing the degree of antibody biotinylation, the authors have now achieved sensitivities of 92.4% overall and 82% for those excreting <100 EGF. A direct increase in the mean level of circulating antigen was found with increasing egg counts. The difference between those excreting >100 EGF (53 individuals) and those excreting <100 EGF (39 cases) was statistically significant (P<0.01). None of the control sera (23 uninfected individuals and 16 patients infected with other parasites) had circulating antigen levels >80 ng/ml. Thus, the test specificity was >99%. The test accuracy was 94.7%, the positive predictive value 100%, and the negative predictive value 84.8%.

Detection of Cryptosporidium antigen in stool samples among diarrhoeic children.

A double antibody sandwich ELISA technique, using a chromatography purified Cryptosporidium antiserum (fractiuon 1), was applied to detect faecal antigen in children infected with Cryptosporidium suffering from diarrhoea. The assay could detect antigens in 55 out of 60 (91.7%) infected children. False positive reactions were detected in 4 children infected with E. histolytica and 2 children with Giardia. The mean level of copro-antigen was higher in children, below 10 years, than in older patients, with a highly significant difference. A significant higher mean copro-antigen level was found among children below 2 years of age who were bottle feeders when compared to those receiving breast feeding. Higher mean optical density readings was obtained in those with severe forms of diarrhoea than mild or moderate forms with statistically significant difference (P < 0.01). It was concluded that detection of Cryptosporidium antigens by ELISA technique in the stool samples is a highly sensitive (91.7%) and specific (85%) diagnostic method. It correlates well with the diarrhoea forms and the age of patients.

Histopathological and histochemical studies on the sigmoidal and rectal tissues of hepatosplenic children with gastro-intestinal troubles.

Hepatosplenomegaly accompanied with different intestinal troubles is more or less a marked clinical manifestations in children. The histopathological and histochemical changes were studied in biopsied materials taken from the sigmoidal and rectal tissues of 49 children. These children had schistosomiasis mansoni (26), schistosomiasis and amoebiasis (4), schistosomiasis and tuberculosis (TB.) (2), amoebiasis (4), thalassemia (6), acute myeloid leukaemia (AML) (1), mucopolysaccharidosis (1) and bacillary dysentery (5). The pathological changes were erosion ulceration hyperplasia, atrophy, crypt-abscess and fibrosis (mucosa) and oedema, congestion, cellular infiltration (Lamina propria). The chemical changes were the mucin secretion, deposition of collagen and fibrin and activity of the argentaffin cells. Not all the disease agent had the same effect, but changes were marked mainly in children with S. mansoni and/or E. histolytica.