Lipopolysaccharide variation in Coxiella burnetti: intrastrain heterogeneity in structure and antigenicity

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Abstract
Lipopolysaccharides (LPS) were isolated from phase variants of C. burnetii Nine Mile, and the isolated LPS and C. burnetii cells were compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. The LPS were found to be the predominant component which varied structurally and antigenically between virulent phase I and avirulent phase II. A comparison of techniques historically used to extract the phase I antigenic component revealed that the aqueous phase of phenol-water, trichloroacetic acid and dimethyl sulfoxide extractions of phase I C. burnetii cells all contained phase I LPS, although the efficiency and specificity of extraction varied. These studies provide additional evidence that phase variation in C. burnetii is analogous to the smooth-to-rough LPS variation of gram-negative enteric bacteria, with phase I LPS being equivalent to smooth LPS and phase II being equivalent to rough LPS. A variant was identified with a 3rd LPS chemotype which appears to have a structural complexity intermediate to phase I and II LPS. All 3 C. burnetti LPS contain a 2-keto-3-deoxyoctulosonic acid-like substance, heptose and gel Limulus amoebocyte lysates in subnanogram amounts. The C. burnetii LPS were nontoxic to chicken embroyos at doses of > 80 .mu.g/embryo, in contrast to Salmonella typhimurium smooth- and rough-type LPS, which were toxic in ng amounts.