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Infection and Immunity, June 2000, p. 3180-3185, Vol. 68, No. 6
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Enterotoxicity and Cytotoxicity of Vibrio parahaemolyticus Thermostable Direct Hemolysin in In Vitro Systems

Francesco Raimondi,1,2 Joseph P. Y. Kao,3,4 Carla Fiorentini,5 Alessia Fabbri,5 Gianfranco Donelli,5 Nicoletta Gasparini,1 Armido Rubino,1 and Alessio Fasano2,3,6,*

Department of Pediatrics, Università "Federico II," Naples,1 and Department of Ultrastructures, Instituto Superiore di Sanità, Rome,5 Italy, and Gastrointestinal Pathophysiology Laboratory, Center for Vaccine Development,2 Division of Pediatric Gastroenterology and Nutrition,6 Department of Physiology,3 and Medical Biotechnology Center, University of Maryland Biotechnology Institute,4 University of Maryland, Baltimore, Maryland

Received 1 December 1999/Returned for modification 25 January 2000/Accepted 1 March 2000

Vibrio parahaemolyticus is a marine bacterium known to be a common cause of seafood gastroenteritis worldwide. The thermostable direct hemolysin (TDH) has been proposed to be a major virulence factor of V. parahaemolyticus. TDH causes intestinal fluid secretion as well as cytotoxicity in a variety of cell types. In this study, we investigated the interplay between the hemolysin's enterotoxic and cytotoxic effects by using both human and rat cell monolayers. As revealed by microspectrofluorimetry, the toxin causes a dose-dependent increase in intracellular free calcium in both Caco-2 and IEC-6 cells. This effect was reversible only when low toxin concentrations were tested. The TDH-activated ion influx pathway is not selective for calcium but admits ions such sodium and manganese as well. Furthermore, in the same range of concentration, the hemolysin triggers a calcium-dependent chloride secretion. At high concentrations, TDH induces a dose-dependent but calcium-independent cell death as assessed by functional, biochemical, and morphological assays.


* Corresponding author. Mailing address: Division of Pediatric Gastroenterology and Nutrition, University of Maryland School of Medicine, 22 South Greene St., Box 140, Baltimore, MD 21201. Phone: (410) 328-0812. Fax: (410) 328-1072. E-mail: afasano{at}umaryland.edu.


Infection and Immunity, June 2000, p. 3180-3185, Vol. 68, No. 6
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.



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