title: Grey variants of the live vaccine strain of Francisella tularensis lack lipopolysaccharide O-antigen, show reduced ability to survive in macrophages and do not induce protective immunity in mice.
abstract: Francisella tularensis live vaccine strain (LVS) produces two colony types when grown on solid media, often referred to as blue variants (BV) and grey variants (GV). Whereas blue variant bacteria possessed a lipopolysaccharide O-side chain, grey variant bacteria lacked O-side chains. Grey variant bacteria appeared in stationary phase bacterial cultures and could be identified using a novel FACS-based assay. Compared to blue variant bacteria, grey variants showed a reduced ability to infect and survive in macrophages. The immunisation of mice with blue variant bacteria, but not grey variant bacteria, induced protective immunity towards fully virulent F. tularensis.
authors.affiliation: Defence Science and Technology Laboratory, Salisbury, Wiltshire, UK.
authors.forename: Gill
authors.initials: G
authors.lastname: Hartley
authors.forename: Rosa
authors.initials: R
authors.lastname: Taylor
authors.forename: Jo
authors.initials: J
authors.lastname: Prior
authors.forename: Sarah
authors.initials: S
authors.lastname: Newstead
authors.forename: Paul G
authors.initials: PG
authors.lastname: Hitchen
authors.forename: Howard R
authors.initials: HR
authors.lastname: Morris
authors.forename: Anne
authors.initials: A
authors.lastname: Dell
authors.forename: Richard W
authors.initials: RW
authors.lastname: Titball
mesh_terms: D000818:Animals; D001428:Bacterial Vaccines / Q000276:immunology*; D002460:Cell Line; D005434:Flow Cytometry; D005604:Francisella tularensis / Q000145:classification / Q000276:immunology* / Q000302:isolation & purification / Q000502:physiology; D008264:Macrophages / Q000382:microbiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D019081:O Antigens / Q000502:physiology*
chemical_list: D001428:Bacterial Vaccines; D019081:O Antigens