title: Relationship between virulence and immunity as revealed in recent studies of the F1 capsule of Yersinia pestis.
abstract: Yersinia pestis, the causative agent of plague, possesses multiple virulence determinants encoded on its three plasmids and on its chromosome. We evaluated the role of the protein capsule F1 in virulence an immunity against plague. Strains lacking F1, either those that are naturally occurring or those with genetically defined nonpolar mutations in the structural gene, retained their virulence for mice and nonhuman primates. However, both active immunization with F1, from either a recombinant vector or Y. pestis, and passive immunization with F1 monoclonal antibody protected mice from experimental infection with wild-type F1-positive organisms. These results suggest that protective immunogens like F1 need not be essential for virulence. The rare isolation of virulent F1-negative organisms from F1-immunized animals infected with F1-positive strains supports this conclusion and also suggests that, in addition to F1, an optimal vaccine against plague should include essential virulence factors as immunogens.
authors.affiliation: Division of Bacteriology, U. S. Army Medical Research Institute of Infectious Diseases, Frederick, Maryland 21702, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Friedlander
authors.forename: S L
authors.initials: SL
authors.lastname: Welkos
authors.forename: P L
authors.initials: PL
authors.lastname: Worsham
authors.forename: G P
authors.initials: GP
authors.lastname: Andrews
authors.forename: D G
authors.initials: DG
authors.lastname: Heath
authors.forename: G W
authors.initials: GW
authors.lastname: Anderson
authors.forename: M L
authors.initials: ML
authors.lastname: Pitt
authors.forename: J
authors.initials: J
authors.lastname: Estep
authors.forename: K
authors.initials: K
authors.lastname: Davis
mesh_terms: D000818:Animals; D016667:Bacterial Capsules / Q000276:immunology / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D051379:Mice; D010930:Plague / Q000276:immunology / Q000382:microbiology*; D010957:Plasmids; D014774:Virulence; D015010:Yersinia pestis / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity*
chemical_list: D001426:Bacterial Proteins; C086725:caf1 protein, Yersinia pestis