Application of a single-chain fragment variable (scFv) antibody for the confirmatory diagnosis of hydatid disease in non-endemic areas

A scFv antibody against cystic echinococcosis was produced by genetic engineering and then applied to the immunohistochemical diagnosis of 18 cases of cystic echinococcosis presented in non-endemic coastal areas. The diagnosis of these cases by ultrasound and serum-based examinations was inconclusive. The 750 bp scFv antibody gene was expressed in COS-7 cells, and the antibody localized in the cytoplasm. The scFv antibody can detect the germinal layer and protoscolices of actively growing cysts but not of the degenerating protoscolices and has a diagnostic efficiency higher than that of single serum or ultrasound testing (P < 0.05). The combined use of scFv antibodies with serology and ultrasound diagnostics results in a diagnostic efficiency comparable to that of surgery. The scFv antibody can be used as a confirmatory test for the diagnosis of hydatid disease in non-endemic areas, providing a beneficial supplementary diagnostic method that complements traditional immune testing and ultrasonic radiology and thus helping physicians to effectively differentiate hydatid disease.