At present, there is no consensus that purified schistosome egg
antigens offer any advantage in the diagnosis of
schistosomiasis by
enzyme linked
immunosorbent assay (ELISA). Previously, we demonstrated by multiple techniques that the major serologic
antigens in Schistosoma japonicum soluble egg
antigen (SEA) are
glycoproteins, and that the
glycoproteins with highest specificity and sensitivity are hydrophobes. We therefore tested these materials for their specificity, sensitivity and cost effectiveness in the ELISA. In this study we used five SEA fractions that varied in their purity and antigenicity. The order of immunologic specific activity in the ELISA, measured by titration of a standard sera pool, was: hydrophobic
glycoproteins (highest), crude SEA
glycoproteins, hydrophilic
glycoproteins, crude SEA, and SEA
proteins (lowest). Complexity (purity) of these materials were (in rank order), hydrophilic
glycoproteins (purest), hydrophobic
glycoproteins, crude
glycoproteins, SEA
proteins, and crude SEA (most complex). Epidemiologic sensitivity in the ELISA was tested on limited but well characterized populations. At high
antigen coating concentration (0.5 microgram/well), the only
antigen fraction with poor sensitivity was SEA
proteins. There was little difference in epidemiologic sensitivity between the purer fractions with highest immunologic sensitivity (hydrophobic
glycoproteins and crude SEA
glycoproteins) and the crude SEA which possesses intermediate immunologic sensitivity. Differences in epidemiologic sensitivity were most pronounced when wells were coated at an
antigen concentration (0.1 microgram/well) where crude SEA began to fail. Specificity for all preparations, assessed by reactivity with sera from patients with other
trematode infections and with cestode and
nematode infections, was excellent. The clinical sensitivity of the ELISA employing crude S. japonicum SEA is so high, and the specificity so good, that the increased immunologic sensitivity of partially purified
antigens had little effect on epidemiologic sensitivity. This is not true for the S. mansoni ELISA where crude
antigens had inferior sensitivity and specificity.