Antibodies are generated during infection to Coxiella burnetii macrophage infectivity potentiator protein (Cb-Mip).

Antisera from rabbits immunized with formalin inactivated Coxiella burnetii isolates associated with either acute (Nine Mile, phase I or phase II) or chronic (Priscilla) Q fever showed reactivity to a C. burnetii macrophage infectivity potentiator protein (Cb-Mip) cloned in Escherichia coli. Further, antisera generated in BALB/c mice after infection with live Nine Mile phase I or Priscilla isolates also showed reactivity to Cb-Mip by immunoblot analysis. In addition, human serum from an individual with previous serological and clinical evidence of Q fever showed reactivity to Cb-Mip. This study indicates that Cb-Mip is immunogenic in both experimental and natural infections, and is the first report on the presence of antibodies to Mip/Mip-like proteins of intracellular bacteria in human sera. Cb-Mip may serve as a potential target antigen for developing recombinant vaccines or diagnostic assays for Q fever.