Date Published: March 23, 2015
Publisher: Public Library of Science
Author(s): Tingjin Chen, Jinyun Yu, Zeli Tang, Zhizhi Xie, Zhipeng Lin, Hengchang Sun, Shuo Wan, Xuerong Li, Yan Huang, Xinbing Yu, Jin Xu, Aaron R. Jex. http://doi.org/10.1371/journal.pntd.0003641
Abstract: BackgroundApproximately 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 FindingsThere 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 rCsHK, 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 rCsHK. 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/SignificanceDue 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.
Partial Text: Clonorchiasis, induced by Clonorchis sinensis (C. sinensis) infection, is a major public health problem in Southeast Asian countries including China, Korea, Taiwan, and Vietnam. Approximately 35 million people are infected with this neglected fluke globally, of whom 15 millions are in China . The World Health Organization (WHO) announced in 2009 that C. sinensis infection is one of the biological agents that can induce cholangiocarcinoma . In spite of its public health threat, there are still few effective measures to prevent this neglected tropical disease. Humans can be infected with C. sinensis by ingestion of raw or undercooked freshwater fish with metacercariae. The metacercariae of C. sinensis excyst in the duodenum, then migrate into hepatic bile ducts where the flukes mature into adult worms . During the long term of parasitism, the worms continuously release excretory/secretory products (ESPs), a cocktail of hundreds to thousands of bioactive proteins. As molecules involved in the interaction between the parasite and host, ESPs have been well characterized to be targets for vaccine and drug development [4–7].
In the current study, we identified differences in spatial structure between CsHK and HKs from the definitive hosts of C. sinensis, humans and rats. We also characterized the substrate specificity and allosteric regulation of rCsHK in detail. The distribution of CsHK in worms and in liver tissue and serum from C. sinensis infected rats was confirmed. Furthermore, a high-level specific antibody was induced in rats by immunization with rCsHK. 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.