Specific in vitro interferon-gamma and IL-2 production as biomarkers during treatment of chronic Q fever

Contains fulltext : 153993.pdf (publisher's version ) (Open Access)BACKGROUND: Antibiotic treatment of chronic Q fever is cumbersome and of long duration. To monitor treatment, there is a need for alternative biomarkers. Coxiella burnetii-specific interferon (IFN)-gamma and interleukin (IL)-2 production reflect the type of effector and memory T-cell response. In chronic Q fever, C. burnetii-specific IFN-gamma production is higher and IL-2 production is lower than in individuals with past Q fever. Here we explore whether C. burnetii-specific IFN-gamma and IL-2 production correlate to treatment response. METHODS: We studied the longitudinal C. burnetii-specific IFN-gamma/IL-2 ratio in fifteen proven chronic Q fever patients. All patients were followed for at least 18 months during antibiotic treatment. Treatment was considered successful when clinical recovery was observed, a positive PCR for C. burnetii DNA in blood became persistently negative, anti-phase I IgG showed a fourfold decrease or more, and imaging techniques showed disappearance of infectious foci. RESULTS: Overall, the IFN-gamma/IL-2 ratio declined when patients experienced a successful treatment outcome. When treatment failed, IFN-gamma/IL-2 ratios did not significantly decrease. The median (+/-IQR) slope of the longitudinal IFN-gamma/IL-2 ratio with successful treatment was -2.10 (-7.02 to -0.06), and -0.15 (-1.13 to 0.25) with unsuccessful treatment (P = 0.19). Q fever endocarditis patients had higher IFN-gamma/IL-2 ratios than patients with endovascular infections. CONCLUSION: We propose that the IFN-gamma/IL-2 ratio can be used as an additional biomarker for monitoring chronic Q fever treatment, with declining ratios being indicative of successful treatment

A combination of interferon-gamma and interleukin-2 production by Coxiella burnetii-stimulated circulating cells discriminates between chronic Q fever and past Q fever

Contains fulltext : 137608.pdf (publisher's version ) (Closed access)Infection with Coxiella burnetii may lead to life-threatening chronic Q fever endocarditis or vascular infections, which are often difficult to diagnose. The present study aims to investigate whether measurement of in-vitro interferon-gamma (IFN-gamma) production, a key cytokine in the immune response against C. burnetii, differentiates chronic from a past cleared infection, and whether measurement of other cytokines would improve the discriminative power. First, C. burnetii-specific IFN-gamma production was measured in whole blood of 28 definite chronic Q fever patients and compared with 135 individuals with past Q fever (seropositive controls) and 908 seronegative controls. IFN-gamma production was significantly higher in chronic Q fever patients than in controls, but with overlapping values between patients and seropositives. Secondly, the production of a series of other cytokines was measured in a subset of patients and controls, which showed that interleukin (IL)-2 production was significantly lower in patients than in seropositive controls. Subsequently, measuring IL-2 in all patients and all controls with substantial IFN-gamma production showed that an IFN-gamma/IL-2 ratio >11 had a sensitivity and specificity of 79% and 96%, respectively, to diagnose chronic Q fever. This indicates that a high IFN-gamma/IL-2 ratio is highly suggestive for chronic Q fever. In an additional group of 25 individuals with persistent high anti-Coxiella phase I IgG titres without definite chronic infection, all but six showed an IFN-gamma/IL-2 ratio <11. In conclusion, these findings hold promise for the often difficult diagnostic work-up of Q fever and the IFN-gamma/IL-2 ratio may be used as an additional diagnostic marker