Flagella phase variation in the thermophilic campylobacters
Date
1986
Authors
Harris, Lori-Anne
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The purpose of this study was to examine the contribution of flagella to the widely used Lior heat-labile serotyping scheme for thermophilic Campylobacters. The serotype chosen for examination, serotype 8, contains strains of both Campylobacter jejuni and Campylobacter coli and is commonly isolated from man. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of cultures of strains belonging to the Lio 8 serogroup, showed that many of the strains produced flagellin molecules of two different molecular weights (MW). Radio-immunoprecipitation experiments with the Lio 8 typing antiserum revealed that while most Lio 8 strains produced flagellin which reacted with Lio 8 antiserum, some strains produced flagellin which did not react with this antiserum. This indicated that while the Lio 8 antiserum contained a high titer of serospecific antibodies to flagellin the serotype determinants for the Lio 8 serogroup were not carried on the flagella.
Immune-electron microscopy with Lio 8 antiserum showed that some cultures were producing two antigenically distinct flagella. This observation together with the ability of strains to produce flagellins of different MW suggested that inf. jejuni and f. coli flagella were subject to antigenic phase variation. To show that a strain could switch from the production of one flagellin antigenic type to the production of a different flagellin antigenic type, cells originating from a single clone were selected which exhibited motility in the presence of Lio 8 antiserum. By SDS-PAGE analysis, flagellin produced before the switch (phase 1) was found to have a MW of 61,000, while flagellin produced after the switch (phase 2) had a MW of 57,000. This flagellin switching was shown by three different strains. In the case of the Lio 8 serogroup type strain VC 167, the rate of the phase 1 to phase 2 (1.9 x 10-5) switch was over ten times higher than the rate of the phase 2 to phase 1 switch (1.1 x 10-6). Although the two flagellins reacted with polyclonal antiserum to non surface-exposed conserved Campylobacter flagellin epitopes and to a monoclonal antibody which recognized a cross reactive internal Campylobacter flagellin epitope, only phase 1 flagellin reacted with Lio 8 antiserum by radioimmune-precipitation, enzyme-linked immunosorbent assay, or by . 0 1 . immune-e ectron microscopy. Absorption experiments confirmed that the X serospecific epitopes were exposed on the surface of the native phase 1 flagella filament. Biochemical analysis of the two flagellin molecules revealed significant structural conservation. The N-terminal amino acid sequences were identical for the first 22 residues, and peptide mapping showed many conserved peptides. However, the flagellins were different in MW and amino acid composition, and also contained unique pepides.