Abstract
Currently, the accepted method for Q fever serodiagnosis is indirect immunofluorescent antibody assay (IFA) using the whole cell antigen. In this study, we prepared the recombinant antigen of the 27-kDa outer membrane protein (Com1) which has been shown to be recognized by Q fever patient sera. The performance of recombinant Com1 was evaluated in ELISA by IFA confirmed serum samples. Due to the low titers of IgG and IgM in Q fever patients, the standard ELISA signals were further amplified by using biotinylated anti-human IgG or IgM plus streptavidin-HRP polymer. The modified ELISA can detect 88% (29 out of 33) of Q fever patient sera collected from Marines deployed to Iraq. Less than 5% (5 out of 156) of the sera from patients with other febrile diseases reacted with the Com1. These results suggest that the modified ELISA using Com1 may have the potential to improve the detection of Q fever specific antibodies.
Highlights
Q fever is a worldwide zoonotic disease caused by infection with Coxiella burnetii
The purified and refolded recombinant Com1 antigen without its signal peptide can be recognized by both human IgG and IgM to C. burnetii in enzyme-linked immunosorbent assay (ELISA)
The recombinant protein antigen Recombinant Com1 Protein (rCom1) offers a considerable advantage over the whole cell antigen of C. burnetii
Summary
Q fever is a worldwide zoonotic disease caused by infection with Coxiella burnetii. This agent is highly infectious for humans by aerosol, where a single organism can cause the disease. The presence of C burnetii DNA can be detected occasionally in patient serum of acute phase Q fever with Polymerase Chain Reaction (PCR) [8,9,10], the current diagnosis of Q fever relies mainly on serological methods [11] These methods include the indirect immunofluorescent antibody assay (IFA) [12, 13], the complement fixation assay (CFA) [14, 15], and the enzyme-linked immunosorbent assay (ELISA) [16, 17]. There are commercially available IFA and ELISA tests for Q fever, the serological test results vary considerably among different laboratories using the same kit This may be due to the residual egg yolk or tissue culture proteins in the whole cell antigen preparation [2, 21]. The results demonstrated the amplification of ELISA signal may have the potential to improve the serological assay
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