Immunogenicity and protective ability of corpuscular and soluble vaccines prepared from different Coxiella burnetii phase I strains.

BALB/c mice immunized intraperitoneally (ip) with killed purified Coxiella burnetii phase I corpuscular vaccines or trichloroacetic acid (TCA) extracts from phase I corpuscles (soluble vaccines) were protected against ip challenge with both homologous and heterologous C. burnetii phase I strains. Though the degree of protection, namely the inhibition of C. burnetii multiplication in the mouse spleen slightly varied, in general, corpuscular vaccines provided better protection than soluble ones. Cross-protection was accompanied by comparable levels of cell-mediated immune response as evaluated by lymphocyte transformation test (LTT). However, higher stimulation indices of LTT were obtained with homologous than with heterologous strains. The values of antibody response as determined by enzyme-linked immunosorbent assay (ELISA) were higher with homologous strains too. On average, both antibody-inducing and antibody-binding capabilities of the strains Priscilla and S were lower than those of the Nine Mile and Luga strains, except for values obtained with the antigens from homologous strains.