Immunization of dogs with Q fever vaccines : comparison of phase I, II and phase I CMR Coxiella burnetii vaccines

Abstract

Q fever vaccines were tested in mixed breed dogs by vaccinating them with formalin-killed Coxiella burnetii whole cells (WC) in either phase I (WCI) or phase II (WCII), or the chloroform: methanol residue (CMR) subunit of phase I cells. Phase I vaccines mixed (1:1) with Freund’s incomplete adjuvant (FIA) induced humoral immune responses to phases I and II antigens as measured by microagglutination assay. The CMR vaccine mixed (1:1) with FIA induced greater antigen-specific antibody levels to both phases I and II antigens than the corresponding WCI vaccine. The WCII vaccine induced antibody responses to only phase II antigens. The time course of erythema and induration after skin testing with C. burnetii antigens were suggestive of cell-mediated immunity (CMI). Although granulomas were observed with only WCI and WCII, none of the skin test antigens induced abscesses at the injection site. In contrast, axillary nodes draining the vaccine injection site developed sterile draining abscesses in all dogs by days 19 to 24 for the WCI and CMR, and day 104 for the WCII vaccines. The abscesses had resolved within 30 days after first appearance. Responses to Con A and PHA and recall antigens of lymphocytes from the blood, axillary and mesenteric nodes, and spleen at 222 days after vaccination were variable among dogs. Lymphocytes from various organs responded to one or more of the recall antigens and to both mitogens in the absence or presence of indomethacin. Although these Q fever vaccines induced humoral and CMI, either the antigens or FIA caused sterile draining abscesses. The skin testing results suggest that the CMR vaccine is a better alternative than the WC vaccines because of the lack of late granuloma formation by CMR. There remain further studies to determine the source of the adverse reactions and to evaluate the effectiveness of the vaccines against coxiellosis in dogs.