Kawasaki Disease-Specific Molecules in the Sera Are Linked to Microbe-Associated Molecular Patterns in the Biofilms

<div><p>Background</p><p>Kawasaki disease (KD) is a systemic vasculitis of unknown etiology. The innate immune system is involved in its pathophysiology at the acute phase. We have recently established a novel murine model of KD coronary arteritis by oral administration of a synthetic microbe-associated molecular pattern (MAMP). On the hypothesis that specific MAMPs exist in KD sera, we have searched them to identify KD-specific molecules and to assess the pathogenesis.</p><p>Methods</p><p>We performed liquid chromatography-mass spectrometry (LC-MS) analysis of fractionated serum samples from 117 patients with KD and 106 controls. Microbiological and LC-MS evaluation of biofilm samples were also performed.</p><p>Results</p><p>KD samples elicited proinflammatory cytokine responses from human coronary artery endothelial cells (HCAECs). By LC-MS analysis of KD serum samples collected at 3 different periods, we detected a variety of KD-specific molecules in the lipophilic fractions that showed distinct m/z and MS/MS fragmentation patterns in each cluster. Serum KD-specific molecules showed m/z and MS/MS fragmentation patterns almost identical to those of MAMPs obtained from the biofilms formed <i>in vitro</i> (common MAMPs from <i>Bacillus cereus</i>, <i>Yersinia pseudotuberculosis</i> and <i>Staphylococcus aureus</i>) at the 1^st study period, and from the biofilms formed <i>in vivo</i> (common MAMPs from <i>Bacillus cereus</i>, <i>Bacillus subtilis/Bacillus cereus/Yersinia pseudotuberculosis</i> and <i>Staphylococcus aureus</i>) at the 2^nd and 3^rd periods. The biofilm extracts from <i>Bacillus cereus</i>, <i>Bacillus subtilis</i>, <i>Yersinia pseudotuberculosis</i> and <i>Staphylococcus aureus</i> also induced proinflammatory cytokines by HCAECs. By the experiments with IgG affinity chromatography, some of these serum KD-specific molecules bound to IgG.</p><p>Conclusions</p><p>We herein conclude that serum KD-specific molecules were mostly derived from biofilms and possessed molecular structures common to MAMPs from <i>Bacillus cereus, Bacillus subtilis</i>, <i>Yersinia pseudotuberculosis and Staphylococcus aureus</i>. Discovery of these KD-specific molecules might offer novel insight into the diagnosis and management of KD as well as its pathogenesis.</p>