Doxycycline Treatment of Mansonella perstans–Infected Individuals Affects Immune Cell Activation and Causes Long-term T-cell Polarization

Abstract

Background Doxycycline is used for treatment of Mansonella (M.) perstans infection. Immune modulatory effects of both, M. perstans and doxycycline, have been described but long-term implications on host immune response are not defined. Here we determined multiple immune parameters of M. perstans infected individuals prior to and after doxycycline treatment to characterize doxycycline effects on host T-cell immunity. Methods Immune characterization of doxycycline-treated M. perstans infected individuals was performed as part of an open-label randomized clinical trial. Immune cell population phenotyping by flow cytometry and functional in vitro T-cell assays were performed at baseline, six months, and ‘long-term’ (18-24 months) after treatment start. Treatment efficacy, based on peripheral blood microfiliaria burden, was correlated with immune parameters and effects on immune response against concomitant Mycobacterium tuberculosis infection were determined. Results Immune population phenotyping indicated changes in functional T-cell responses after doxycycline treatment. Constitutive and superantigen induced T-cell activation and polarization towards T helper type (TH)1 phenotype at baseline declined after doxycycline treatment whereas low proportions of TH17 and TH1* cells at baseline increased significantly at follow-up. In accordance, long-term decline in antigen-specific TH1 responses against concomitant Mycobacterium tuberculosis infection was seen. Notably, only TH17 and TH1* changes after six months and TH17 at baseline were negatively correlated with M. perstans microfilaria burden or reduction whereas long-term changes were not associated with treatment efficacy. Conclusions We found long-term immune modulatory effects of doxycycline treatment leading to decreased constitutive T-cell activation, polarization towards TH17/TH1*, and impaired immune response against concomitant Mycobacterium tuberculosis infection.