Elevated serum levels of neutrophil elastase in patients with influenza virus-associated encephalopathy

We examined serum levels of various cytokines, chemokines, growth factors, and adhesion molecules in patients with uncomplicated influenza (n = 20) and influenza virus-associated encephalopathy (IE) (n = 18) to understand the underlying mechanism of IE. We found that IL-1β, IL-2, IL-5, IL-6, IL-7, IL-8, IL-10, IL-13, G-CSF, GM-CSF, TNF-α, TIMP-1, MMP-9, sE-selectin, and neutrophil elastase were elevated significantly in sera from patients with uncomplicated influenza and those with IE, compared with normal controls (n = 20). Of note, neutrophil elastase, sE-selectin, IL-8, and IL-13 were elevated significantly in IE as compared with uncomplicated influenza. In the present study, for the first time, we found that serum levels of neutrophil elastase were increased in patients with IE compared with uncomplicated influenza, which suggested that cerebral endothelial damage in the development of IE was mediated by neutrophil elastase. The present study implied that anti-elastase agents are possibly an effective therapeutic protocol for IE, but this needs further elucidation.