Immunological consequences of Coxiella burnetii phase variation

The influence of the number of passages in chick embryo yolk sac (EPs) on the properties of the lipopolysaccharide (LPS) and other antigens of Coxiella burnetii Priscilla strain in polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate (SDS-PAGE), immunoblot analysis, enzyme-linked immunosorbent assay (ELISA) and complement-fixation reaction (CFR) test has been studied. Three phases in the phase variation of Coxiella burnetii could be distinguished by these methods: phase I lasting up to the 20th passage (EP 20), intermediate phase corresponding to EP 20-EP 70, and phase II beginning at EP 80. The changes in LPS were more marked than those in proteins which conserved their immunoblot profile up to EP 80. The phase II was clearly demonstrated by all the methods used.