| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2005: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2004: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2003: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Research Abstract |
1.The septicemia caused by Vibrio vulnificus is characterized by formation of the secondary edematous skin damage. In order to clarify the process, action mechanisms of the metalloprotease (VVP), a major toxin causing the skin damage, was studied. It was found that VVP evoked the exocytotic histamine release from mast cells via direct binding of the N-terminal catalytic domain to the membrane receptor, and that it activated the bradykinin-generating cascade through limited proteolysis and generation of the active enzymes, activated factor XII and plasma kallikrein, from the zymogens.
2.V.vulnificus can sense the cell density and regulate expression of various genes encoding toxins, as well as VVP. This coordinated regulation system is called the quorum-sensing (QS) system. The present study showed that V.vulnificus secreted a small pheromone-like substance as a signal molecule, and that when the signal molecule secreted reached to a crucial threshold level, the bacterium operated the QS
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system and stimulated VVP production at the expression level. Although it was also effective at 37 C, the QS system functioned more effectively at lower temperature suggesting V.vulnificus can produce more VVP at the interstitial space but not in the intestinal tract or blood stream.
3.The cytotoxic hemolysin (VVH) is another toxin produced by V.vulnificus. Since this toxin is so unique, the presence of vvhA encoding VVH has been documented to be a reliable evidence for classification to this species. VVH from an eel-pathogenic strain, CDC B3547, showed significantly different properties to that from human-pathogenic strains because three amino acid residues in the C-terminal domain are substituted. The nucleotide sequence of vvhA of CDC B3547 was determined, and the PCR primers specific to the gene was designed. The genetic test using the primers indicated that they were useful for specific selection of eel-pathogenic strains. Therefore, the PCR primers designed might be suitable for genotyping of V.vulnificus strains. Less
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