Evaluation of recombinant cathepsin L for immunodiagnosis of gnathostomiasis

Abstract

Gnathostoma spinigerum infection is a serious health problem occurring in several countries, including Thailand. The gold standard for diagnosis is currently detection of antibody- specific 24 kDa antigens with immunoblotting. However, this technique requires lengthy antigen preparation, and experience to interpret correctly. In this study, recombinant antigen, cathepsin L (GsCatL), of G.spinigerum was evaluated as an immunodiagnostic tool. Several previous studies suggested cathepsin L as a potential antigen for the diagnosis of helminthic infections. Initially, GsCatLcDNA was cloned into a prokaryotic expression vector and then expressed as recombinant GsCatL (rGsCatL) in Escherichia coli. The rGsCatL expressed at the molecular size of 48 kDa was purified and evaluated with gnathostomiasis-, other helminthic infected-and healthy sera using immunoblot and indirect ELISA. The results showed that rGsCatL cross-reacted with all sera by immunoblot with lowsensitivity (25.7%) and specificity (41%). The indirect ELISA also exhibited the same result as immunoblotting. These results suggest that rGsCatLusing a prokaryotic expression system is not suitable for diagnosis of gnathostomiasis. However, a eukaryotic expression system still needs to be verified for correct conformational structure through further evaluation.