Immunoblot analysis of antibody response in mice infected with Coxiella burnetii phase I.

Mouse sera collected from day 4 to day 133 postinfection (p.i.) with phase I Coxiella burnetii strain Nine Mile were analysed by immunoblotting with phase I C. burnetii cell lysate. Antibodies of IgG class protein antigens were revealed already on day 10 p.i. (60, 49 and 27 kD proteins), followed by those to 77 kD protein from day 18 p.i. and to further 7 (from 42 to 70 kD) proteins from day 28 p.i. IgG antibody reaction was observed also with 5 antigens in 14-20 kD region corresponding to lipopolysaccharides from day 22 p.i. Surprisingly, antibodies of IgM type appeared later (from day 22 p.i.) and were directed only to protein antigens, most markedly to 60 and 77 kD proteins. Differences in immunoblot patterns observed with the serum collected on day 72 p.i. before and after absorption to phase I and phase II C. burnetii cells, and to phase I cells treated by trichloroacetic acid (TCA) or KIO4, indicate the surface localization of protein phase I antigenic epitopes, which can be destroyed partly by TCA and almost completely by KIO4 treatment.