Immunological properties of the lipopolysaccharide-protein complex of Coxiella burnetii.

Purified lipopolysaccharide-protein complex (LPS-PC) extracted by trichloroacetic acid from phase I Coxiella burnetii organisms induced in mice and rabbits fair levels of antibodies directed to antigen 1 and antigen 2, as detected by complement-fixation (CF), microagglutination (MA), opsonization-phagocytosis (OP) and serum protection (SP) tests. In guinea pigs only very low levels of MA antibodies against antigen 2 were demonstrated. In rabbit serum, MA antibodies directed to antigen 2 were found exclusively in the IgM fraction after the primary immunizing dose; the second dose was followed by gradual shift of MA antibodies to the IgG class. Two immunizing doses of the LPS-PC were more effective when testing antibody response in mice or protection of mice and guinea pigs against phase I virulent challenge.