[Application of trichloroacetic acid-treated antigen for serodiagnosis of Q fever by indirect immunofluorescence technique].

It is well known that the etiologic agent, Coxiella burnetii, exhibits an antigenic phase variation (phase I to phase II), and the diagnostic significance of the relative antibody titers against phase I and phase II antigens is pointed out. Therefore both phase I and phase II antigens are necessary for the serological examination of Q fever. But it is not so easy to prepare and maintain the phase II antigen by the conventional method. In the present study we tried to prepare the phase II antigen for immunofluorescence test by chemical treatment of the phase I antigen. As a result, treatment of the TK-1 strain of C. burnetii (phase I) with 10% trichloroacetic acid for 4 hr at 4 degrees C modified the antigenicity. The modified antigen reacted strongly with anti-phase II antibody.