Cytokine profiles in patients with Q fever fatigue syndrome

Background: Q fever fatigue syndrome (QFS) is a state of prolonged fatigue following around 20% of acute Q fever cases. It is thought that chronic inflammation plays a role in its etiology. To test this hypothesis we measured circulating cytokines and the ex-vivo cytokine production in patients with QFS and compared with various control groups. Materials/methods: Peripheral blood mononuclear cells (PBMCs), whole blood, and serum were collected from 20 QFS patients, 19 chronic fatigue syndrome (CFS) patients, 19 Q fever seropositive controls, and 25 age- and sex-matched healthy controls. Coxiella-specific ex-vivo production of tumor necrosis factor (TNF)alpha, interleukin (IL)-1 beta, IL-6, and interferon (IFN) was measured, together with a total of 92 circulating inflammatory proteins. Results: PBMCs of QFS patients produced more IL-6 (P=0.0001), TNF alpha (P=0.0002), and IL-1 beta (P =0.0005) than the various control groups when stimulated with Coxiella antigen. QFS patients had distinct differences in circulating inflammatory markers compared to the other groups, including higher concentrations of circulating IL-6 and IFN gamma. Conclusion: QFS patients showed signs of chronic inflammation compared to asymptomatic Q fever seropositive controls, CFS patients, and healthy controls, of which the monocyte-derived cytokines TNF alpha, IL-1 beta, and especially IL-6, are likely crucial components. (C) 2019 The British Infection Association. Published by Elsevier Ltd. All rights reserved.