The effect of dissociation of Bacteroides nodosus pili on their efficacy as a protective antigen against ovine footrot.
Previous studies have shown that pili from homologous Bacteroides nodosus provide protective immunity in sheep against footrot, whereas denatured pilin subunits are ineffective. The aim of the present study was to examine whether pili that were dissociated into pilin subunits under less vigorous, non-denaturing treatment conditions, would provide an effective level of protective immunity. Using the techniques of gel permeation chromatography, light scattering and susceptibility to proteolysis as measures of disruption, it was shown that pili were dissociated either by the neutral detergents n-octyl-beta-D-glucopyranoside (NOG) and Tween 80 or by lowering the pH with 1 M phosphoric acid to pH 2.2. Circular dichroic spectra indicated, however that the samples were not denatured by these treatments. Electron microscopic monitoring of detergent dissociated material following exhaustive dialysis showed the presence of protein-detergent micelles and "in-line" aggregates which gave the appearance of short fibres. Within these monitored preparations, there was no evidence of native undissociated pili. Pili dissociated by NOG or acid were tested in protection trials and shown to provide protective immunity, although agglutination titres of serum taken from the vaccinated sheep were significantly lower than those of animals inoculated with intact pili.
CSIRO Division of Animal Health, Animal Health Research Laboratory, Parkville, Vic. Australia.
D J
DJ
Stewart
N M
NM
McKern
J A
JA
Ramshaw
P A
PA
Tulloch
D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology*; D001439:Bacteroides / Q000276:immunology / Q000648:ultrastructure*; D002850:Chromatography, Gel; D002942:Circular Dichroism; D003902:Detergents; D010861:Fimbriae, Bacterial / Q000276:immunology*; D005535:Foot Rot / Q000517:prevention & control*; D005960:Glucosides; D006863:Hydrogen-Ion Concentration; D008854:Microscopy, Electron; D011136:Polysorbates; D012756:Sheep; D012757:Sheep Diseases / Q000517:prevention & control*; D014611:Vaccination / Q000662:veterinary
D000942:Antigens, Bacterial; D003902:Detergents; D005960:Glucosides; D011136:Polysorbates; C018619:octyl-beta-D-glucoside