Biomarkers screening for viral myocarditis through proteomics analysis of plasma exosomes

Objective To compare and analyze the differentially expressed plasma exosomic proteome between healthy control group (Control group) and viral myocarditis group (VMC group) to search for biomarkers that maybe used for early diagnosis of VMC. Methods Fifty plasma samples of Control group and VMC group were collected respectively from Henan Provincial People′s Hospital (from January 2016 to December 2017), and then 5 samples (1 ml) of each group were selected randomly, after exosomes extraction with ultra-centrifugation, difference gel electrophoresis (DIGE) was used to isolate the total proteins, and then the protein spots with more than 2-fold changes between VMC and Control group were picked up after the software analysis, afterward, the varied proteins were identified by MALDI-TOF/TOF mass spectrometry. Finally, the specifically related protein was selected to be verified by ELISA with the plasma exosomic samples of Control (n=40) and VMC (n=40). Results A total of 10 varied protein spots were found including 8 up-regulated proteins and 2 down-regulated proteins between VMC and Control group. After MS analysis, the up-regulated proteins in VMC group contained KRT2, KRT5, KRT9, KRT77, KRT78, AZGP1, HP and RBP4, whereas the down-regulated ones were CD5L and C1QB. RBP4 was selected to validate by ELISA analysis, and the corresponding results showed that RBP4 was increased specifically in plasma exosomes of VMC group (P<0.05) after comparing with Control group, which was consistent with DIGE. Conclusion Ten proteins related to VMC are detected in total, and RBP4 might serve as a potential specific biomarker for early screening and diagnosis of VMC. Key words: Viral myocarditis; Plasma; Exosome; Biological markers; Proteomics