title: Virulence phenotype and genetic characteristics of the T32-ISTRATI Shigella flexneri 2a vaccine strain.
abstract: The T32-ISTRATI strain, which has been used as an oral attenuated Shigella flexneri 2a vaccine, has lost the invasive phenotype due to a spontaneous deletion in the shigella virulence plasmid. This deletion has eliminated three plasmid loci (ipaBCDA, invA and virG) that are necessary for production of a positive Sereny test by Shigella species. Virulence in the Sereny test was reconstituted in the T32-ISTRATI strain by the conjugal transfer of an intact 140 M Da virulence plasmid from S. flexneri 5. The T32-ISTRATI vaccine is safe when given orally in multiple doses of 50-100 x 10(9) organisms, and both homologous and heterologous protection has been reported in large Romanian and Chinese field trials. Although the protective antigen(s) in this vaccine have not been identified, the potential use of non-invasive plasmid deletion mutants as living shigella vaccines is illustrated by the T32-ISTRATI vaccine.
authors.affiliation: Department of Bacterial Immunology, Walter Reed Army Institute of Research, Washington, DC 20307.
authors.forename: M
authors.initials: M
authors.lastname: Venkatesan
authors.forename: C
authors.initials: C
authors.lastname: Fernandez-Prada
authors.forename: J M
authors.initials: JM
authors.lastname: Buysse
authors.forename: S B
authors.initials: SB
authors.lastname: Formal
authors.forename: T L
authors.initials: TL
authors.lastname: Hale
mesh_terms: D001483:Base Sequence; D002872:Chromosome Deletion; D002874:Chromosome Mapping; D015342:DNA Probes; D004269:DNA, Bacterial / Q000235:genetics; D004405:Dysentery, Bacillary / Q000517:prevention & control; D005798:Genes, Bacterial; D006801:Humans; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D010641:Phenotype; D010957:Plasmids; D012763:Shigella flexneri / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity; D014613:Vaccines, Attenuated / Q000276:immunology; D014765:Viral Vaccines / Q000276:immunology*; D014774:Virulence / Q000235:genetics
chemical_list: D015342:DNA Probes; D004269:DNA, Bacterial; D014613:Vaccines, Attenuated; D014765:Viral Vaccines