Evaluation of Three Recombinant Antigens for the Detection of Anti-Coxiella Antibodies in Cattle

<b>Background/Objectives:</b> The detection of anti-Coxiella antibodies using serological methods is essential for identifying exposed ruminants and preventing this important zoonotic disease in livestock. In recent years, numerous attempts have been made to increase diagnostic performance as well as simplify the production of serological assays. Commercially available tests often use whole-cell antigens, which can decrease specificity and require high-level biosafety facilities for manufacturing. The aim of this work was to produce three <i>Coxiella burnetii</i> (<i>C. burnetii</i>) antigens in recombinant form and assess them for the detection of anti-Coxiella antibodies in ruminants. <b>Methods:</b> Three recombinant <i>C. burnetii</i> antigens (Com-1, MceB, AdaA) were selected among immunodominant antigens and produced in a heterologous system (<i>Escherichia coli</i>). Following purification, the proteins were utilized to coat ELISA plates and evaluated for seroreactivity against sera from both negative and positive cattle. <b>Results:</b> Com-1 demonstrated the greatest agreement with the commercial test, albeit moderate. MceB exhibited nonspecific reactivity against a large number of sera, while the AdaA showed reactivity against only a few positive sera. <b>Conclusions:</b> Our findings are consistent with previous research, indicating that utilizing a single antigen to identify exposed animals is unfeasible with current knowledge, most likely due to the complex immunological response following <i>C. burnetii</i> infection in cattle. Consequently, it is critical to continue testing and identifying immunoreactive antigens in order to further investigate them and, potentially, select the most appropriate.