Potential serodiagnostic markers for Q fever identified in Coxiella burnetiiby immunoproteomic and protein microarray approaches

Abstract

BackgroundCoxiella burnetii is the etiological agent of Q fever. The clinical diagnosis of Q fever is mainly based on several serological tests. These tests all need Coxiella organisms which are difficult and hazardous to culture and purify.ResultsAn immunoproteomic study of C. burnetii Xinqiao strain isolated in China was conducted with the sera from experimentally infected BALB/c mice and Q fever patients. Twenty of whole proteins of Xinqiao recognized by the infection sera were identified by mass spectrometry. Nineteen of the 20 proteins were successfully expressed in Escherichia coli and used to fabricate a microarray which was probed with Q fever patient sera. As a result, GroEL, YbgF, RplL, Mip, OmpH, Com1, and Dnak were recognized as major seroreactive antigens. The major seroreactive proteins were fabricated in a small microarray and further analyzed with the sera of patients with rickettsial spotted fever, Legionella pneumonia or streptococcal pneumonia. In this analysis, these proteins showed fewer cross-reactions with the tested sera.ConclusionsOur results demonstrate that these 7 Coxiella proteins gave a modest sensitivity and specificity for recognizing of Q fever patient sera, suggesting that they are potential serodiagnostic markers for Q fever.

Coxiella burnetii immunogenic proteins as a basis for new Q fever diagnostic and vaccine development

“…Therefore, we speculate that these proteins might be the most presented antigens to immune cells due to high abundance during activated metabolism. This assumption is in good agreement with the result of Xiong et al (2012a) who evaluated potential serodiagnostic markers for Q fever and identified 13 proteins with housekeeping function out of 20 antigenic proteins. They discovered that proportionally more of these proteins are recognized by the sera from patients with acute rather than with chronic or persistent infections.…”

“…Thus, fourteen articles investigated the reactivity of human, seven mice, and one guinea pig sera. Interestingly, one of the selected studies employed two different experimental procedures for evaluating the same human sera (Xiong et al, 2012a). On the other hand, we excluded a publication describing a frequently published antigen which was recognized by sera from experimentally and naturally infected goats, since it did not report a screening method (Fernandes et al, 2009).…”

“…A more precise conclusion about the portion of host species-specific anti-C. burnetii antigen responses can be drawn from those three publications, which analyzed human and mouse sera in parallel using the same techniques (Xiong et al, 2012a;Wang et al, 2013;Jiao et al, 2014;Ref. 16-18, Table 1).…”

“…In some of the selected immunoproteomic studies, sensitivity and specificity of ELISAs based on seroreactive proteins were analyzed (Beare et al, 2008;Chen et al, 2009;Sekeyova et al, 2010) or protein microarrays (Xiong et al, 2012a). Sensitivity ranged from 40% to 60%.…”

“…The numbers in brackets indicate absolute protein numbers. (b) The Venn diagram comprises immunogenic proteins identified in publications 16, 17 and 18 as listed in Table 1, that analyzed human and mouse sera in parallel with the same techniques (Xiong et al, 2012a;Wang et al, 2013;Jiao et al, 2016). In total 58 proteins were identified and the ratios for antigens found exclusively in humans, mice or both were averaged.…”