Immunity in Q fever.

Post-infection and post-vaccination immune mechanisms in Q fever are summarized. Whereas cell-mediated immunity has been found to play a crucial role in developing resistance to Coxiella burnetii infection, data on the role of specific antibodies in Q fever immunity are controversial. The functional state of immunocompetent cells and professional phagocytes seems to be decisive for the persistence of C. burnetii within phagocytic cells and for the control of Q fever at the host level. Defects of cellular immunity, immune complex formation, and immune response modulation by C. burnetii isolates differing in plasmid composition or LPS antigenic structure are implicated as aetiological factors. Immunogenicity and reactogenicity of three possible vaccine candidates (phase I chloroform-methanol treated and untreated corpuscular vaccine, and phase I soluble chemovaccine) for Q fever prophylaxis is discussed, stressing the need for developing suitable models and defined experimental conditions enabling to compare and evaluate the results obtained in different laboratories.