title: Vibrio vulnificus RTX toxin kills host cells only after contact of the bacteria with host cells.
abstract: Vibrio vulnificus causes acute cell death and a fatal septicaemia. In this study, we show that contact with host cells is a prerequisite to the acute cytotoxicity. We screened transposon mutants defective in the contact-dependent cytotoxicity. Two mutants had insertions within two open reading frames in a putative RTX toxin operon, the rtxA1 or rtxD encoding an RTX toxin (4701 amino acids) or an ABC type transporter (467 amino acids). An rtxA1 mutation resulted in a cytotoxicity defect, which was fully restored by in trans complementation. The expression of RtxA1 toxin increased after host cell contact in a time-dependent manner. The RtxA1 toxin induced cytoskeletal rearrangements and plasma membrane blebs, which culminated in a necrotic cell death. RtxA1 colocalized with actin and caused actin aggregation coinciding with a significant decrease in the F/G actin ratio. The RtxA1 toxin caused haemolysis through pore formation (radius 1.63 nm). The rtxA1 deletion mutant was defective in invading the blood stream from ligated ileal loops of CD1 mice. The rtxA1 null mutation resulted in over 100-fold increase in both intragastric and intraperitoneal LD(50)s against mice. Overall, these results show that the RtxA1 toxin is a multifunctional cytotoxin and plays an essential role in the pathogenesis of V. vulnificus infections.
authors.affiliation: Clinical Vaccine R&D Center, Chonnam National University Medical School, Gwangju 501-746, South Korea.
authors.forename: Young Ran
authors.initials: YR
authors.lastname: Kim
authors.forename: Shee Eun
authors.initials: SE
authors.lastname: Lee
authors.forename: Hyun
authors.initials: H
authors.lastname: Kook
authors.forename: Jung A
authors.initials: JA
authors.lastname: Yeom
authors.forename: Hee Sam
authors.initials: HS
authors.lastname: Na
authors.forename: Soo Young
authors.initials: SY
authors.lastname: Kim
authors.forename: Sun Sik
authors.initials: SS
authors.lastname: Chung
authors.forename: Hyon E
authors.initials: HE
authors.lastname: Choy
authors.forename: Joon Haeng
authors.initials: JH
authors.lastname: Rhee
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects; D002701:Chloramphenicol / Q000494:pharmacology; D004251:DNA Transposable Elements / Q000235:genetics; D005260:Female; D005816:Genetic Complementation Test; D006367:HeLa Cells; D006461:Hemolysis / Q000187:drug effects; D054884:Host-Pathogen Interactions; D006801:Humans; D051379:Mice; D018613:Microscopy, Confocal; D016254:Mutagenesis, Insertional; D009154:Mutation; D014735:Vibrio Infections / Q000382:microbiology* / Q000473:pathology; D041261:Vibrio vulnificus / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D001427:Bacterial Toxins; D004251:DNA Transposable Elements; C434464:RtxA protein, Vibrio cholerae; D002701:Chloramphenicol