Antibody response in man following a small intradermal inoculation with Coxiella burnetii phase I vaccine.

A small inoculum (0.2 microgram) of phase I Coxiella burnetii vaccine given to individuals previously sensitized to CO burnetii elicited a positive skin reaction and a strong IgM phase I antibody response as determined by microagglutination, complement fixation and microimmunofluorescence tests. A similar inoculum administered to nonsensitized individuals did not elitic a skin reaction nor stimulate a recognizable antibody response. Serum from one of these sensitized and skin tested individuals was fractionated by gel filtration methods. The serum and serum fractions were titrated in a mouse seroprotection test using primary chicken embryo cell culture plaque technique as the assay procedure. Results of the mouse seroprotection test indicated that most of the protective activity of the serum was associated with the IgM fraction and that phase I IgM antibody suppressed the growth of C. burnetii in mouse spleen when mixed with the rickettsial suspension prior to inoculation.