[Proteomics of serum exosomes in children in the acute stage of Kawasaki disease: a prospective study].

Objectives: To study the biological processes and functions of serum exosomes in children in the acute stage of Kawasaki disease (KD), so as to provide new biomarkers for the early diagnosis of KD.

Methods: In this prospective study, 13 children with KD who were treated in Children's Hospital of Soochow University from June 2019 to August 2020 were enrolled as the KD group, and 13 children who were hospitalized due to bacterial infection during the same period were enrolled as the control group. Whole blood was collected on the next morning after admission, serum samples were obtained by centrifugation, and exosomes were extracted through ultracentrifugation. Serum exosomes were analyzed by label-free quantitative proteomics, and differentially expressed proteins (DEPs) were screened out for functional enrichment analysis. A protein-protein interaction (PPI) network was plotted, and unique proteins were validated by targeted proteomics.

Results: A total of 131 DEPs were screened out for the two groups, among which 27 proteins were detected in both groups. There were 48 unique DEPs in the KD group, among which 23 were upregulated and 25 were downregulated, and these proteins acted on "complement and coagulation cascades" and "the MAPK signaling pathway". Validation by targeted proteomics showed that FGG, SERPING1, C1R, C1QA, IGHG4, and C1QC proteins were quantifiable in the KD group. A total of 29 proteins were only expressed in the control group, among which 12 were upregulated and 17 were downregulated. Four proteins were quantifiable based on targeted proteomics, i.e., VWF, ECM1, F13A1, and TTR. A PPI network was plotted for each group. In the KD group, FGG and C1QC had close interaction with other proteins, while in the control group, VWF had close interaction with other proteins.

Conclusions: The serum exosomes FGG and C1QC in children in the acute stage of KD are expected to become the biomarkers for the early diagnosis of KD. For children with unexplained fever, detection of FGG, C1QC1, and VWF may help with etiological screening.