Isolation of a protein antigen from Coxiella burnetii

Characterization and protective effect of a 29 kDa protein isolated from Coxiella burnetii by detergent Empigen BB

A 29 kDa protein, isolated from the outer membrane of Coxiella burnetii, strain Nine Mile phase I by detergent Empigen BB, was characterized. The failure in removing lipopolysaccharides (LPS) from preparations of the protein by the purification method used indicates a strong binding between proteins and LPS in the outer membrane of C. burnetii. The protein was immunogenic in mice and protected them against virulent C. burnetii challenge.

Electron-microscopic study of the effect of various extractants on the morphology of Coxiella burnetii

This paper presents the results of the effect of trichloroacetic acid (TCA) at two different temperatures and the effect of a mixture of detergents (D) on Coxiella burnetii. Both TCA and D caused a large destruction of C. burnetii cells. In both cases complexes of high-molar-mass components from the outer membrane were extracted. In the D case not only proteins but a mixture with other high-molar-mass structures were released from the destroyed cells. By extraction of TCA, the antigenic complex composed of lipopolysaccharides (LPS), proteins and phospholipids was released. The effect of the D mixture on C. burnetii causes their complete destruction. The TCA causes a surface destruction of cells but it does not cause complete disintegration. The small-cell variants (SCV) in both cases were shown to be more stable compared to the large-cell variants (LCV).

Clinical aspects and prevention of Q fever in animals

The natural reservoir of Coxiella burnetii encompasses many free-living vertebrates but the major risk of human infection arises through contact with infected ruminant livestock and their contaminated products. The organism has a remarkable affinity for the ruminant placenta and mammary gland but the great majority of naturally-occurring infections are asymptomatic. However, the potential of C. burnetii to cause abortion has been demonstrated experimentally and observed in the field while more recent evidence has implied a contributory role in bovine infertility. Empirical vaccines incorporating inactivated whole cells of C. burnetii or derivatives have induced varying degrees of protection of cattle and sheep against both natural and experimental challenge but, in some cases, severe reactions have occurred at inoculation sites. Modifications in processes of antigen preparation seem to overcome this problem. Discrimination between antibodies resulting from natural infection and those induced by vaccination is possible using ELISAs with specificity for individual immunoglobulin isotypes.

Enzyme-linked immunosorbent fluorescence assay and high-pressure liquid chromatography for analysis of humoral immune responses to Coxiella burnetti proteins

A microtiter enzyme-linked immunosorbent fluorescence assay based on alkaline phosphatase conjugate and 4-methylumbelliferyl phosphate as fluorogenic substrate was developed and adapted to quantitatively analyze immunoglobulin G subclass 1 (IgG1) and IgG2 responses of vaccinated and infected cattle to proteins of Coxiella burnetii. The enzyme-linked immunosorbent fluorescence assay surpassed the conventional enzyme-linked immunosorbent assay with a 50-fold-higher sensitivity and a broader range of linear dose-response signals. Antigens of C. burnetii were purified by sodium dodecyl sulfate extraction and molecular-sieve high-pressure liquid chromatography. The purified 14-, 27-, and 30-kilodalton proteins were used as antigens without any further treatment. Vaccination with either chloroform-methanol-extracted cell residues of C. burnetii or the 27-kilodalton major surface protein evoked an early IgG2 response to the 27-kilodalton protein (2 weeks after immunization), whereas IgG2 to lipopolysaccharides of C. burnetii was detected only in the late phase (13 weeks after immunization). These results may have implications for the serodiagnosis of acute and chronic Q fever. IgG1 against these antigens was induced solely by naturally occurring C. burnetii infections, indicating that infected cattle can be distinguished from vaccinated cattle by using the enzyme-linked immunosorbent fluorescence assay and SP27 antigen.