DISTRIBUTION OF IGA SUBCLASS RESPONSE TO COXIELLA-BURNETII IN PATIENTS WITH ACUTE AND CHRONIC Q-FEVER

The progression of Coxiella burnetii infection to acute or chronic Q f ever has been attributed to biological characteristics of the bacteriu m and to the host immune response. We measured whether set-sam levels of total and specific subclasses IgA1 and IgA2 could be correlated wit h the course of disease in acute and chronic Q fever infections, and w ith the occurrence of endocarditis. In patients with chronic infection , total IgA2 levels mere significantly increased, Q-fever-specific IgA 1 antibodies were detectable in both acute and chronic infections, but only patients with endocarditis had IgA2 antibodies to C, burnetii ph ase II antigens. These findings indicate that the measurement of IgA s ubclasses may be a useful aid in the serological diagnosis of Q fever. Our results reinforce the idea that immunologically mediated host fac tors are important in the pathogenesis of Q fever and in the disease o utcome of this infection. (C) 1998 Academic Press.