title: Construction of genetically marked Vibrio cholerae O1 vaccine strains.
abstract: Attenuated Vibrio cholerae O1 vaccine strains lacking the gene encoding the A subunit of cholera toxin have proven efficacious in preventing experimental cholera. As these strains move from closed, contained testing environments to large-scale field trials, a readily assayable phenotypic trait to distinguish a vaccine strain from wild-type V. cholerae O1 is desirable. We have constructed three derivatives of the attenuated V. cholerae strain CVD 103 which carry a mercury resistance or urease marker in the hlyA gene. CVD 103-HgR was constructed using a protracted marker-exchange procedure; this strain was found to have somewhat lowered colonisation efficiency in infant mice in comparison to its parent strain, CVD 103. The insertion of the resistance marker was repeated using a suicide vector system; CVD 103-HgR2 was found to colonise infant mice as efficiently as CVD 103. Strain CVD 103-UR, in which sequences encoding urease were inserted using a suicide vector, also colonised infant mice as well as CVD 103. The genetically marked strains CVD 103-HgR, CVD 103-HgR2 and CVD 103-UR form the basis for a generation of defined oral vaccines that may give single-dose, long-lasting protection to populations at risk from cholera.
authors.affiliation: Center for Vaccine Development, University of Maryland School of Medicine, Baltimore.
authors.forename: J M
authors.initials: JM
authors.lastname: Ketley
authors.forename: J
authors.initials: J
authors.lastname: Michalski
authors.forename: J
authors.initials: J
authors.lastname: Galen
authors.forename: M M
authors.initials: MM
authors.lastname: Levine
authors.forename: J B
authors.initials: JB
authors.lastname: Kaper
mesh_terms: D000818:Animals; D002771:Cholera / Q000382:microbiology; D002772:Cholera Toxin / Q000235:genetics*; D003967:Diarrhea / Q000382:microbiology; D004352:Drug Resistance, Microbial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D005819:Genetic Markers; D005822:Genetic Vectors; D046911:Macromolecular Substances; D051379:Mice; D016254:Mutagenesis, Insertional; D011817:Rabbits; D014613:Vaccines, Attenuated / Q000096:biosynthesis / Q000235:genetics*; D014734:Vibrio cholerae / Q000235:genetics* / Q000276:immunology* / Q000472:pathogenicity; D014765:Viral Vaccines / Q000096:biosynthesis / Q000235:genetics*; D014774:Virulence
chemical_list: D005819:Genetic Markers; D046911:Macromolecular Substances; D014613:Vaccines, Attenuated; D014765:Viral Vaccines; D002772:Cholera Toxin