Monoclonal antibodies to Coxiella burnetii that cross-react with strain Nine Mile

Proteomics paves the way for Q fever diagnostics

Q fever is a worldwide zoonosis caused by Coxiella burnetii. The disease most frequently manifests clinically as a self-limited febrile illness, as pneumonia (acute Q fever) or as a chronic illness that presents mainly as infective endocarditis. The extreme infectivity of the bacterium results in large outbreaks, and the recent outbreak in the Netherlands underlines its impact on public health. Recent studies on the bacterium have included genome sequencing, the investigation of host-bacterium interactions, the development of cellular and animal models of infection, and the comprehensive analysis of different clinical isolates by whole genome and proteomic approaches. Current approaches for diagnosing Q fever are based on serological methods and PCR techniques, but the diagnosis of early stage disease lacks specificity and sensitivity. Consequently, different platforms have been created to explore Q fever biomarkers. Several studies using a combination of proteomics and recombinant protein screening approaches have been undertaken for the development of diagnostics and vaccines. In this review, we highlight advances in the field of C. burnetii proteomics, focusing mainly on the contribution of these technologies to the development and improvement of Q fever diagnostics.

Identification and Characterization of Coxiella burnetii Strains and Isolates Using Monoclonal Antibodies

We evaluated 6 monoclonal antibodies (MAbs) for their usefulness in identifying and characterizing recognized laboratory strains as well as field isolates of Coxiella burnetii. Five had been generated in response to strain Nine Mile (3 IgM class, 1 IgG class, 1 light chain producers only) and were polypeptide-specific, and 1 was anti-Priscilla (IgG class) and was lipopolysaccharide (LPS)-specific. Initially, the MAbs were used in conjunction with a dot blot assay with which we could differentiate C. burnetii from rickettsiae or chlamydiae. Confirmation of the specificity of these MAbs was provided by demonstrating that only C. burnetii antigens were recognized by certain combinations of antibodies used for immunoblotting proteins of various C. burnetii strains. Subsequently, we characterized antigens of 11 C. burnetii field isolates and 3 reference strains by Western blotting with individual MAbs. MAb 921 and 922 (IgG class), MAb 241, 242, 384, 386, 614 (IgM class), and 7A5, 7A1 (light chain) consistently recognized a protein. Staining intensity differed, depending on the strain tested, and there was variability in the size of the antigen immunoreactive with MAb 14H (IgG class, LPS-specific). The most reactive region was at about 249 kD. Variability of reactivities with field isolates was seen in both the distribution of individual bands and their intensities. We conclude that an extensive immunoblotting technique may be useful for C. burnetii strain differentiation and routine identification of C. burnetii can be accomplished using this MAb-based dot blot assay.