Reliable tool for detection of novel Coxiella burnetii antigens, using immobilized human polyclonal antibodies

- We presented a workflow for identification of novel immunoreactive proteins of C. burnetii using serological proteome analysis.
- Our approach also allowed immunocapturing of intact cells of C. burnetii.
- We confirmed 22 previously described Q fever antigens and proposed 15 novel immunoreactive proteins.
- The immunogenic potential of these proteins were validated by in silico analyses.

Coxiella burnetii (C. burnetii) is the etiological agent of a Q fever-the re-emerging disease with considerable economic impact. Due to many similar symptoms with commonly occurring infections, its clinical diagnosis is very difficult. Thus, a strong effort should be taken to raise the awareness and develop a robust strategy for an accurate diagnosis. The identification of specific C. burnetii biomarkers could be valuable for a sensitive and selective diagnosis of the disease. Herein, we described a workflow to identify immunoreactive proteins of C. burnetii with a high confidence. It is based on immunocapturing of bacterial antigens by biofunctionalized magnetic microspheres, followed by tandem mass spectrometry (MS/MS) identification. We detected dozens of previously reported antigens and proposed 15 novel biomarkers, which specificity was confirmed by in silico epitope analysis. Among them, the cardiolipin synthetase participating in the synthesis of cardiolipin was recognized. This biomarker could play a critical role in the early management of acute Q fever and prevention of Q fever endocarditis.