title: Genotypic and phenotypic characterization of an aroD deletion-attenuated Escherichia coli K12-Shigella flexneri hybrid vaccine expressing S. flexneri 2a somatic antigen.
abstract: The construction and characterization of EcSf2a-2, an aroD-deleted Escherichia coli-Shigella hybrid vaccine carrying chromosomal and plasmid genes from Shigella flexneri and expressing S. flexneri 2a somatic antigen in association with E. coli K12 core are described. Expression of hybrid lipopolysaccharide and deletion of aroD resulted in the attenuation of phenotypic characteristics associated with pathogenicity. The addition of an aroD deletion results in a requirement for an aromatic precursor of para-aminobenzoic acid (PABA), an essential bacterial metabolite not present in mammalian tissues. The biosynthesis of hybrid somatic antigen prevents expression of a Sereny-positive reaction by invasive bacteria capable of expressing a plaque-positive phenotype. A functional kcpA gene is required for expression of the plaque-positive phenotype. The presence of an aroD deletion does not interfere with expression of an invasive phenotype; however, in bacteria containing a functional kcpA gene, replication and spread by invading bacteria are limited, preventing development of the plaque-positive phenotype.
authors.affiliation: Department of Enteric Infections, Walter Reed Army Institute of Research, Washington, DC 20307.
authors.forename: J W
authors.initials: JW
authors.lastname: Newland
authors.forename: T L
authors.initials: TL
authors.lastname: Hale
authors.forename: S B
authors.initials: SB
authors.lastname: Formal
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000096:biosynthesis; D000942:Antigens, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000276:immunology / Q000472:pathogenicity; D017353:Gene Deletion; D005838:Genotype; D006801:Humans; D007075:Immunoglobulin M / Q000096:biosynthesis; D008253:Macaca mulatta; D010641:Phenotype; D010957:Plasmids; D011817:Rabbits; D012763:Shigella flexneri / Q000235:genetics* / Q000276:immunology / Q000472:pathogenicity; D013045:Species Specificity; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000235:genetics* / Q000276:immunology; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000235:genetics* / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D007075:Immunoglobulin M; D014613:Vaccines, Attenuated; D014614:Vaccines, Synthetic