Plasma extracellular vesicle proteomic analysis identifies WARS as a potential biomarker of infectious mononucleosis.

[BACKGROUND] Infectious mononucleosis (IM), caused by Epstein-Barr virus (EBV) infection, is a prevalent disease among children and young adults and may lead to a range of severe complications. Proteomic analysis of extracellular vesicles (EVs) has shown potential for identifying novel biomarkers and therapeutic targets. Consequently, elucidating the proteome signature of plasma EVs in IM may provide insights into pathological mechanisms of this disease, enabling improved diagnostic accuracy and targeted therapeutic development.

[METHODS] In this study, we employed tandem mass tag (TMT)-labeled liquid chromatography‒mass spectrometry (LC‒MS) to perform differential proteomic analysis of plasma EVs between IM patients and healthy controls. Gene Ontology (GO) enrichment analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis and Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database analysis were employed to conduct bioinformatics analyses. Western blotting (WB) and enzyme-linked immunosorbent assay (ELISA) were utilized to validate the differentially expressed proteins in plasma EVs. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic potential of the candidate biomarker, and Spearman correlation analysis was conducted to assess its relationship with EBV viral load.

[RESULTS] We identified 193 differentially expressed proteins in plasma EVs, including 146 upregulated and 47 downregulated proteins in the IM group. Significant alterations were observed across various metabolic, immune-regulating processes, and lipid metabolism processes. Functional analysis highlighted the proteasome as a significantly enriched pathway, while also revealing differentially expressed proteins associated with crucial inflammatory and disease-related pathways, including the IL-17 signaling pathway and acute myeloid leukemia. Furthermore, we validated the upregulation of tryptophan-tRNA ligase, cytoplasmic (WARS), in clinical plasma EV samples from IM patients. The diagnostic value of EV WARS was evaluated by ROC curve analysis, which yielded an area under the curve (AUC) of 0.8091, with a sensitivity of 64.52% and a specificity of 83.33% for distinguishing IM patients from healthy controls. Additionally, EV WARS concentration in IM patients exhibited a moderate positive correlation (r = 0.4980, p = 0.0044) with EBV viral load.

[CONCLUSIONS] Our findings provide a comprehensive plasma EV protein expression profile of IM, and indicate the potential value of WARS for IM diagnosis. This study contributes to a deeper understanding of IM pathophysiology and lays the groundwork for future diagnostic studies.