title: Resistance of the cholera vaccine candidate IEM108 against CTXPhi infection.
abstract: The cholera toxin (CT) genes ctxAB are carried on a lysogenic phage of Vibrio cholerae, CTXPhi, which can transfer ctxAB between toxigenic and nontoxigenic strains of bacteria. This transfer may pose a problem when live oral cholera vaccine is given to people in epidemic areas, because the toxin genes can be reacquired by the vaccine strains. To address this problem, we have constructed a live vaccine candidate, IEM108, which carries an El Tor-derived rstR gene. This gene encodes a repressor and can render bacterial resistance to CTXPhi infection. In this study, we evaluated the resistance of IEM108 against CTXPhi infection by using a CTXPhi marked for chloramphenicol (CAF) resistance and an in vivo model. We found that the cloned rstR gene rendered IEM108 immune to infection with the marked CTXPhi. In addition, the infection rate of IEM108 was even lower than that of the native CTXPhi-positive strain. These results suggest that the vaccine candidate IEM108 is resistant to infection by CTXPhi.
authors.affiliation: National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, P.O. Box 5, Changping, Beijing 102206, PR China. lgw424@126.com
authors.forename: Guangwen
authors.initials: G
authors.lastname: Liu
authors.forename: Meiying
authors.initials: M
authors.lastname: Yan
authors.forename: Weili
authors.initials: W
authors.lastname: Liang
authors.forename: Guoming
authors.initials: G
authors.lastname: Qi
authors.forename: Yanqing
authors.initials: Y
authors.lastname: Liu
authors.forename: Shouyi
authors.initials: S
authors.lastname: Gao
authors.forename: Biao
authors.initials: B
authors.lastname: Kan
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D015139:Blotting, Southern; D002702:Chloramphenicol Resistance / Q000235:genetics; D002772:Cholera Toxin / Q000235:genetics*; D022121:Cholera Vaccines / Q000235:genetics; D004269:DNA, Bacterial / Q000032:analysis; D017930:Genes, Reporter; D006801:Humans; D017912:Inovirus / Q000235:genetics / Q000502:physiology*; D007421:Intestine, Small / Q000382:microbiology; D011817:Rabbits; D012097:Repressor Proteins / Q000235:genetics; D014161:Transduction, Genetic; D014734:Vibrio cholerae / Q000235:genetics / Q000254:growth & development / Q000821:virology*
chemical_list: D001426:Bacterial Proteins; D022121:Cholera Vaccines; D004269:DNA, Bacterial; D012097:Repressor Proteins; C107871:RstR protein, Vibrio cholerae; D002772:Cholera Toxin