Biol. Pharm. Bull. 29(1) 180—182 (2006)

causes fatal septicemia and necrotizing wound infections, especially in patients with hepatic diseases, heavy alcohol drinking habits and hemochromatosis. V. vulnificus septicemia is characterized by a rapid and fulminant progression, and results in a mortality rate exceeding 50%. Several bacterial components have been suggested to be the virulence factors of V. vulnificus. Of these, an extracellular hemolysin or cytolysin (named VvhA), the most potent exotoxin, kills mice and shows a variety of biological activities including hemolysis or cytolysis, apoptosis, and vasodilatation. In animal studies, the injection of purified VvhA reproduces the pathological manifestations of septicemia caused by injecting live bacteria. However, the pathogenetic significance of VvhA is being seriously doubted due to the reported effects of VvhA-deficient mutants on mouselethality. The inactivation of the vvhA gene does not affect mouse-lethality, which raises the possibility that only small amounts of VvhA are produced in vivo, and that this VvhA is rapidly inactivated by host factors like cholesterol and bacterial factors such as proteases. Therefore, in order to better characterize the pathogenetic roles of VvhA, further detailed studies regarding the in vitro and in vivo production and inactivation of VvhA are required. In laboratory common media, VvhA is produced in the early growth phase and becomes abruptly inactivated in the late growth phase with a concomitant production of proteases, which results in the belief that the inactivation of VvhA is due to its destruction by proteases. However, our recent study demonstrated that the inactivation of VvhA was due to a novel oligomerization of VvhA by an unknown mechanism, but not to its destruction by proteases. In the present study, we found that bovine serum albumin (BSA) and human serum albumin (HSA) can inhibit or delay VvhA oligomerization, and thus enhance its hemolytic activity.