Vibrio cholerae cytolysin causes an inflammatory response in human intestinal epithelial cells that is modulated by the PrtV protease.
BACKGROUND
Vibrio cholerae is the causal intestinal pathogen of the diarrheal disease cholera. It secretes the protease PrtV, which protects the bacterium from invertebrate predators but reduces the ability of Vibrio-secreted factor(s) to induce interleukin-8 (IL-8) production by human intestinal epithelial cells. The aim was to identify the secreted component(s) of V. cholerae that induces an epithelial inflammatory response and to define whether it is a substrate for PrtV.


RESULTS
Culture supernatants of wild type V. cholerae O1 strain C6706, its derivatives and pure V. cholerae cytolysin (VCC) were analyzed for the capacity to induce changes in cytokine mRNA expression levels, IL-8 and tumor necrosis factor-alpha (TNF-alpha) secretion, permeability and cell viability when added to the apical side of polarized tight monolayer T84 cells used as an in vitro model for human intestinal epithelium. Culture supernatants were also analyzed for hemolytic activity and for the presence of PrtV and VCC by immunoblot analysis.


CONCLUSIONS
We suggest that VCC is capable of causing an inflammatory response characterized by increased permeability and production of IL-8 and TNF-alpha in tight monolayers. Pure VCC at a concentration of 160 ng/ml caused an inflammatory response that reached the magnitude of that caused by Vibrio-secreted factors, while higher concentrations caused epithelial cell death. The inflammatory response was totally abolished by treatment with PrtV. The findings suggest that low doses of VCC initiate a local immune defense reaction while high doses lead to intestinal epithelial lesions. Furthermore, VCC is indeed a substrate for PrtV and PrtV seems to execute an environment-dependent modulation of the activity of VCC that may be the cause of V. cholerae reactogenicity.
Ou
Gangwei
G
Department of Clinical Microbiology/Immunology, Umeå University, Umeå, Sweden.
Rompikuntal
Pramod Kumar
PK
Bitar
Aziz
A
Lindmark
Barbro
B
Vaitkevicius
Karolis
K
Wai
Sun Nyunt
SN
Hammarström
Marie-Louise
ML
D004847:Epithelial Cells / Q000378:metabolism* / Q000382:microbiology*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D006461:Hemolysis; D006801:Humans; D007249:Inflammation; D016209:Interleukin-8 / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000382:microbiology*; D009154:Mutation; D010447:Peptide Hydrolases / Q000378:metabolism*; D054353:Perforin / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D014734:Vibrio cholerae / Q000378:metabolism*
D016209:Interleukin-8; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D054353:Perforin; D010447:Peptide Hydrolases; C513132:PrtV protein, Vibrio cholerae