Development of High-Throughput Multiplex Serology to Detect Serum Antibodies against Coxiella burnetii

Abstract

The causative agent of Q fever, the bacterium Coxiella burnetii (C. burnetii), has gained increasing interest due to outbreak events and reports about it being a potential risk factor for the development of lymphomas. In order to conduct large-scale studies for population monitoring and to investigate possible associations more closely, accurate and cost-effective high-throughput assays are highly desired. To address this need, nine C. burnetii proteins were expressed as recombinant antigens for multiplex serology. This technique enables the quantitative high-throughput detection of antibodies to multiple antigens simultaneously in a single reaction. Based on a reference group of 76 seropositive and 91 seronegative sera, three antigens were able to detect C. burnetii infections. Com1, GroEL, and DnaK achieved specificities of 93%, 69%, and 77% and sensitivities of 64%, 72%, and 47%, respectively. Double positivity to Com1 and GroEL led to a combined specificity of 90% and a sensitivity of 71%. In a subgroup of seropositives with an increased risk for chronic Q fever, the double positivity to these markers reached a specificity of 90% and a sensitivity of 86%. Multiplex serology enables the detection of antibodies against C. burnetii and appears well-suited to investigate associations between C. burnetii infections and the clinical manifestations in large-scale studies.

Keywords: Coxiella burnetii; infection marker; multiplex serology; seroepidemiology.

Figure 1

Antibody levels in the reference panel of 76 C. burnetii seropositive and 91 seronegative reference samples. CBU_937, CBU_370, Com1, and GroEL show a significantly different distribution (p < 0.05) between the two reference groups. Stars above boxplots indicate the level of significance, p < 0.01 (**); p < 0.01 (***).

Figure 2

Antibody responses against the C. burnetii antigens Com1 and GroEL measured in 76 C. burnetii seropositive and 91 seronegative patients. Dashed lines (x = 200 MFI; y = 70 MFI) indicate the respective cutoffs to obtain a specificity of 90% and a combined sensitivity of 71%.