Advanced Enzymology, Expression Profile and Immune Response of Clonorchis sinensis Hexokinase Show Its Application Potential for Prevention and Control of Clonorchiasis

Abstract

Background

Approximately 35 million people are infected with Clonorchis sinensis ( C. sinensis) globally, of whom 15 million are in China. Glycolytic enzymes are recognized as crucial molecules for trematode survival and have been targeted for vaccine and drug development. Hexokinase of C. sinensis ( CsHK), as the first key regulatory enzyme of the glycolytic pathway, was investigated in the current study.

Principal Findings

There were differences in spatial structure and affinities for hexoses and phosphate donors between CsHK and HKs from humans or rats, the definitive hosts of C. sinensis. Effectors (AMP, PEP, and citrate) and a small molecular inhibitor regulated the enzymatic activity of r CsHK, and various allosteric systems were detected. CsHK was distributed in the worm extensively as well as in liver tissue and serum from C. sinensis infected rats. Furthermore, high-level specific IgG1 and IgG2a were induced in rats by immunization with r CsHK. The enzymatic activity of CsHK was suppressed by the antibody in vitro. Additionally, the survival of C. sinensis was inhibited by the antibody in vivo and in vitro.

Conclusions/Significance

Due to differences in putative spatial structure and enzymology between CsHK and HK from the host, its extensive distribution in adult worms, and its expression profile as a component of excretory/secretory products, together with its good immunogenicity and immunoreactivity, as a key glycolytic enzyme, CsHK shows potential as a vaccine and as a promising drug target for Clonorchiasis.

Author Summary

Clonorchiasis, caused by Clonorchis sinensis ( C. sinensis) infection, is a kind of neglected tropical disease. There are still few effective measures to prevent clonorchiasis. As in other helminthes, hexokinase (HK) has been well characterized as a target for vaccine and drug development. In the current study, we identified differences in spatial structure between CsHK and HKs from the definitive C. sinensis hosts, humans and rats. We also characterized the substrate specificity and allosteric regulation of r CsHK in detail. The distribution of CsHK in the worm and in the liver tissue and serum from C. sinensis infected rats were confirmed. Furthermore, a high-level specific antibody in rat was induced by immunization with r CsHK. The enzymatic activity of CsHK was suppressed by the antibody in vitro. Additionally, the survival of C. sinensis was inhibited by the antibody in vivo and in vitro. Our study shows that CsHK has vaccine potential and is a promising drug target for Clonorchiasis.