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.