Objective: To identify the molecules of soluble egg antigen (SEA) for early diagnosis of Schistosoma japonicum infection by two-dimensional electrophoresis (2-DE), immunoblotting and liquid chromatography with tandem mass spectrometry (LC-MS/MS).
Methods: The 2-DE of SEA was executed through first direction isoelectric focusing (IEF) in immobilized pH gradient gel 3-10 (IPG3-10) and second direction SDS-PAGE. The protein dots of SEA on the SDS-PAGE gel were transferred to nitrocellulose membrane. These nitrocellulose membranes were responded to the sera of healthy, sera of mice at 1 week, 2 weeks and 6 weeks post-infection respectively, then the membrane color was developed with the second antibody of HRP labeled goat anti -mouse IgG conjugate and substrate DAB. The protein dots recognized by sera of mice in the early stage of schistosome infection were identified by LC-MS/MS.
Results: After matching and analyzing the Western blot patterns of SEA responding to acute infection sera (1 week and 2 weeks post-infection), chronic infection sera (6 weeks post-infection) and healthy sera by PDQuest 1.0 software, two protein dots were found to be recognized by sera of mice at 1 week, 2 weeks and 6 weeks post-infection, and three protein dots were only recognized by the sera of mice at 6 weeks post-infection, no protein dot was recognized by healthy mouse sera. The data of LC-MS/MS showed that the two protein molecules recognized by the sera of mice with schistosome infection in the early stage were heat shock protein 70 (HSP70) and 78 kDa glucose-regulated protein (Grp78/Bip) respectively.
Conclusion: The results of this study preliminarily indicate that HSP70 and Grp78 in SEA have early diagnostic value for S. japonicum infection.