Identification of proinflammatory flagellin proteins in supernatants of Vibrio cholerae O1 by proteomics analysis.
The genome of Vibrio cholerae contains five flagellin genes that encode proteins (FlaA-E) of 39-41 kDa with 61-82% identity among them. Although the existing live oral attenuated vaccine strains against cholera are protective in humans, there is an intrinsic residual cytotoxic and inflammatory component associated with these candidate vaccine strains. Bacterial flagellins are known to be potent inducers of proinflammatory molecules via activation of Toll-like receptor 5. Here we found that purified flagella from wild type V. cholerae 395 induced significant release of interleukin (IL)-8 from cultured HT-29 human colonic epithelial cells. Furthermore we found that filtered supernatants of KKV90, a DeltaflaA isogenic strain unable to produce flagella, were still able to activate production of IL-8 albeit to significantly lower levels than the wild type, suggesting that other activators of proinflammatory molecules were still present in these supernatants. A comparative proteomics analysis of secreted proteins of V. cholerae 395 and KKV90 identified additional proteins with potential to induce IL-8 release in HT-29 cells. Secreted proteins in the range of 30-45 kDa identified by two-dimensional electrophoresis and mass spectrometry revealed the presence of two additional flagellins, FlaC and FlaD, that appeared to be secreted 3- and 6-fold more, respectively, in the mutant compared with the wild type. Double isogenic mutants flaAC and flaAD were unable to trigger IL-8 release from HT-29 cells. In sum, we have shown that purified flagella and secreted flagellin proteins (FlaC and FlaD) are inducers of IL-8 release from epithelial cells via Toll-like receptor 5. This observation may explain, in part, the observed reactogenicity of cholera vaccine strains in humans.
Xicohtencatl-Cortés
Juan
J
Department of Immunobiology, University of Arizona, Tucson, Arizona 85724, USA.
Lyons
Sean
S
Chaparro
Adriana P
AP
Hernández
Diana R
DR
Saldaña
Zeus
Z
Ledesma
Maria A
MA
Rendón
María A
MA
Gewirtz
Andrew T
AT
Klose
Karl E
KE
Girón
Jorge A
JA
D017077:Culture Media, Conditioned / Q000737:chemistry* / Q000494:pharmacology; D005408:Flagellin / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D019073:HT29 Cells; D006801:Humans; D018836:Inflammation Mediators / Q000032:analysis* / Q000378:metabolism; D016209:Interleukin-8 / Q000032:analysis / Q000096:biosynthesis; D030781:Organisms, Genetically Modified; D040901:Proteomics / Q000379:methods*; D041241:Vibrio cholerae O1 / Q000235:genetics / Q000276:immunology*
D017077:Culture Media, Conditioned; D018836:Inflammation Mediators; D016209:Interleukin-8; D005408:Flagellin; C067138:flaA protein, bacteria