Enzyme-linked immunosorbent assay using cysteine proteinase antigens for immunodiagnosis of human paragonimiasis

An enzyme-linked immunsorbent assay (ELISA) using worm extract antigens from lung flukes of Paragonimus westermani provided good sensitivity to sera from patients with paragonimiasis westermani but high cross-reactivity with sera from most fascioliasis patients and some patients with onchocerciasis or clonorchiasis. To improve the specificity, we tested an ELISA using fluke cysteine proteinases as antigens. Cysteine proteinases were partially purified from the excretory/secretory products of P. westermani by 40-75% ammonium sulfate fractionation, hydrophobic chromatography, and arginine affinity chromatography. An ELISA using the enzyme preparation not only had increased sensitivity to paragonimiasis westermani sera but also reduced cross-reactivity with the fascioliasis, onchocerciasis, and clonorchiasis sera to negligible levels. The reactivity of the ELISA to paragonimiasis miyazakii sera was similar to that of paragonimiasis westermani sera. A proteinase preparation from P. ohirai, which can be obtained easily from infected rats, provided similar results. Therefore, the ELISA using cysteine proteinases of Paragonimus could not distinguish the parasite species with which patients were infected, but it is a valuable assay with which to immunodiagnose paragonimiasis even when the proteinases are prepared from nonhuman species.