Preparation Of Q Fever Vaccine Of Chloroform-methanol Residue Of Coxiella Burnetii And Primary Valuation Of Its Immunoprotectivity And Safety

Coxiella burnetii is an obligate intracellular bacterium that causes a worldwide zoonotic disease, Q fever. It is an air-borne IFNectious agent and recognized as an important agent of biological threats. Human and animals are sensitive to it and peoples working in contacting with the IFNected animals are easy to suffer from Q fever. Inoculation of vaccines against Q fever is a key way to prevent the human IFNection caused by C. burnetii.In this study, C. coxiella Xinqiao strain isolated in China was propagated in chicken egg embryos and the whole cell vaccine (WCV) and chloroform-methanol residue vaccine (CMR) were prepared with the coxiellal cells purified from the IFNected yolk sac membranes of embryos. To investigate the differences of fatty acids between WCV and CMR vaccines of C. burnetii, their fatty acids were analyzed by gas-chromatography. There were significantly different in composition and content of fatty acids between WC and CMR. Eleven fatty acids were not detected by gas-chromatography in CMR in comparison with that in WCV; 4 of them were unsaturated fatty acids and other 4 were branched-chain fatty acids and 70% of them were long-chain fatty acids with 18 C atoms or more. In addition, the ratios of branched-chain fatty acids to linear-chain fatty acids and unsaturated fatty acids to saturated fatty acids were also significantly different between WCV and CMR.To investigate the immunogenicity and immunoprotectivity of CMR, the CMR was used to immunize BALB/c mice and the specific antibody level of the immunized mice was analyzed by indirect immunofluoresce assay (IFA) and cell-mediated immunity response was detected by assess the proliferation of the splenic lymphocytes in vitro. The pathogenic agent in the blood and spleen samples of the immunized mice after challenge of C. burnetii was detected by quantitative real-time PCR specific for the IFNectious agent. The high levels of specific antibody (IgG) to C. burnetii and proliferation of lymphocytes responding to CMR were detected in sera and splenic cells from the immunized mice, respectively. The high levels of cytokines, TNF-α, IFN-γ, and IL-10 detected in sera of mice immunized with CMR and supernatant of splenic lymphocytes cultured in vitro.The coxiella-loads in blood and spleens from mice immunized with CMR were detected in markedly lower levels of C. burnetii compared with that from mice without immunization after challenge of C. burnetii Xinqiao strain. The coxiella-loads in spleens from the mice immunized with CMR absorbed with Al(OH)₃ were significantly lower than that from mice immunized with CMR only. The CMR-immunized mice were also challenged with Nine Mile strain isolated from USA and Henzerling strain isolated from Europe and the mice were efficiently protected from coxiella-IFNection.The hard nodes in the inoculated positions of the skin and the swollen spleens with enlargement of reticular endothelial cells were found in the mice immunized with large dose of WCV. In addition, the indexes of hepatic function (ALT and AST) were markedly higher than normal levels in the mice immunized with large dose of WCV. However, the pathologic alterations and damage in hepatic function were not found in mice immunized with the large dose of CMR.Like WCV, CMR, prepared with Xinqiao strain isolated in China, have capabilities of inducing bodies to yield specific humoral and cell-mediated immune responses, efficiently resisting of IFNection of C. burnetii. However, the adverse reactions caused by the WCV-immunization are significantly reduced in the CMR-immunization and the major reason for its reduction of adverse reaction is due to the fatty acids were vanished or reduced in quantity for CMR compared with WCV. In addition, the adjuvant Al (OH)₃ can markedly enhance the immunoprotectivity of CMR. In addition, mice immunized with WCV partially resisted to the IFNection of Dengue-2 virus, suggesting that the Q fever vaccine has a non-specific protectivity against the virus.