Molecular cloning and functional characterization of Schistosoma japonicum enolase which is highly expressed at the schistosomulum stage

Enolase is a key enzyme in the glycolytic pathway; recent studies have also shown that enolase is found on the surface of several parasites, where it acts as a plasminogen-binding protein. In the present study, the enolase of Schistosoma japonicum has been cloned and expressed. In western blot analysis, the recombinant enolase from S. japonicum ( rSjENO) was recognized by rabbit sera directed against an antigen preparation from adult worms. Kinetic measurement revealed that rSjENO possesses good enzymatic activity. The real-time PCR showed that the enolase gene was highly expressed at 18-28 days of the life cycle. Immunofluorescence testing showed that SjENO was located mainly on the surface as well as in the inner tissues of the worms. Ligand-blotting analysis indicated that rSjENO could bind to human plasminogen as its receptor. In addition, a 24.28% reduction in the liver egg count and a reduction of 21.45% in the fecal egg count were observed in BALB/c mice vaccinated with rSjENO when compared with blank control mice. An ELISA assay suggested that high levels of specific IgG antibody could be induced by rSjENO in vaccinated mice.