[Show abstract][Hide abstract] ABSTRACT: A diarrheogenic strain of non-O1/non-O139 Vibrio cholerae (10325) belonging to serogroup O34 was earlier shown to express a new type of pilus composed of a 20-kDa subunit protein. Amino-terminal sequence data (determined up to 20 amino acid residues) of this protein showed it to be different from the subunit proteins of other known types of pili of V. cholerae. On the other hand, it showed complete homology with the corresponding sequence of a 22-kDa outer membrane protein (OmpW) of V. cholerae. Expression of 10325 pili was favored in AKI rather than in NB medium and at 30°C rather than at 37°C. Further, cultural conditions favoring pilus expression also enhanced autoagglutination and adherence properties of strain 10325. An antiserum to the 20-kDa protein induced passive protection against challenge with the parent organism 10325, but not against V. cholerae O1 strains. Such protection was shown to be mediated by inhibition of intestinal colonization in vivo.
[Show abstract][Hide abstract] ABSTRACT: Cholera vaccines developed by the deletion of CTX genes from Vibrio cholerae induce a residual reactogenicity in up to 10% of vaccinees. A novel cytotonic agent named secreted CHO cell elongating protein (S-CEP) was purified from culture supernatants of CVD 103-HgR (Levine et al., Lancet ii:467-470, 1988). Five fractionation steps yielded electrophoretically pure S-CEP with an M(r) of 79,000. A partially purified preparation caused fluid accumulation in the sealed infant mouse model. The amino terminus bore a unique sequence with strong homology to a cytotonic toxin of El Tor V. cholerae.
Infection and Immunity 11/2000; 68(10):6062-5. · 4.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Vibrio cholerae strains with all known toxin genes deleted or inactivated still cause diarrhoea in some volunteers, suggesting the presence of an unknown virulence factor or factors. Lysozyme-EDTA treated cells of JBK70, a genetically manipulated cholera toxin negative strain of Vibrio cholerae O1, biotype El Tor, release a factor that causes elongation of Chinese hamster ovary (CHO) cells. CHO cell-elongating toxin (Cef) was purified by FPLC chromatography (anion exchange; Q Sepharose High Performance) followed by 2D electrophoresis (isoelectric focusing gel, IEF; pH 3-9 and SDS-PAGE, 8-25% gradient gel). Partly purified toxin (anion exchange or IEF-eluted concentrate) caused fluid accumulation in sealed infant mice suggesting that Cef shows some properties of an enterotoxin. On SDS-PAGE (8-25%) and IEF (pH 2.5-5.0) gels, CHO cell activity was associated with a single band at 85 kDa and a pI of 3.8, respectively. A unique amino terminal sequence, XGDETNSSGASTEVVYESYIQQ, was determined by automated Edman degradation of gel-purified protein. The unique molecular mass, N-terminal sequence and activity on CHO cells indicate that this factor is not zonula occludens toxin (Zot) or accessory cholera enterotoxin (Ace) or the Hly A haemolysin. Partly purified Cef did not increase cyclic AMP or prostaglandin E(2)levels in CHO cells which suggests that its mechanism of action differs from that of cholera toxin.
[Show abstract][Hide abstract] ABSTRACT: A diarrheogenic strain of non-O1/non-O139 Vibrio cholerae (10,325) belonging to serogroup O34 was earlier shown to express a new type of pilus composed of a 20-kDa subunit protein. Amino-terminal sequence data (determined up to 20 amino acid residues) of this protein showed it to be different from the subunit proteins of other known types of pili of V. cholerae. On the other hand, it showed complete homology with the corresponding sequence of a 22-kDa outer membrane protein (OmpW) of V. cholerae. Expression of 10,325 pili was favored in AKI rather than in NB medium and at 30 degrees C rather than at 37 degrees C. Further, cultural conditions favoring pilus expression also enhanced autoagglutination and adherence properties of strain 10,325. An antiserum to the 20-kDa protein induced passive protection against challenge with the parent organism 10,325, but not against V. cholerae O1 strains. Such protection was shown to be mediated by inhibition of intestinal colonization in vivo.
[Show abstract][Hide abstract] ABSTRACT: Determining the activity of purified toxins has generally provided the basis for establishing their role in the host-pathogen relationship. The bacterial genus Vibrio produces a number of exotoxins in addition to cholera toxin, including haemolysin A (HlyA; Vibrio cholerae) and thermostable direct haemolysin (TDH; Vibrio parahaemolyticus), both of which possess membrane-targeting cytolytic activity. The action of HlyA has been analyzed using protocols previously applied to TDH: lysis and flux experiments on human erythrocytes showed that HlyA similarly causes lysis after cell swelling (by colloid osmosis) due to an elevation of cation permeability. However, kinetic measurements of flux, haemolysis and cation selectivity showed that HlyA and TDH form pores with distinct and characteristic features.
Human & Experimental Toxicology 03/1997; 16(2):101-5. · 1.41 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Until recently, only Vibrio cholerae strains of the O1 serogroup have been associated with epidemic cholera. In December 1992, an outbreak of cholera gravis in Vellore, India, was attributed to a new serogroup of V. cholerae recently designated O139. Serogroup O139 cholera has since spread to 13 countries and has reached pandemic proportions. Serogroup O139 cholera evades immunity to O1 cholera and is not detected by the standard O1 antigen test. Understanding the origins of O139 cholera and determining the relatedness of O139 to O1 cholera are necessary to device strategies for detecting, reporting, and controlling this new pandemic. In order to determine the origins of this novel cholera serogroup, O139 was analyzed for virulence genes, for virulence proteins and their regulation, and for its genomic background. We found that O139 and O1 V. cholera strains of the E1 Tor biotype possess highly homologous virulence genes encoding cholera toxin and toxin-coregulated pili and that the regulation of virulence protein expression likewise was indistinguishable between O139 and O1. Pulsed-field gel electrophoresis (PFGE) revealed the restriction digest pattern of O139 strains to be closely related to that of O1 serogroup E1 Tor biotype cholera strains from the Indian subcontinent. However, PFGE showed minor differences among individual O139 cholera isolates, suggesting that O139 V. cholerae is evolving.
Infection and Immunity 10/1994; 62(9):3859-63. · 4.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Vibrio parahaemolyticus, an important agent of seafood-borne gastroenteritis, expresses several putative virulence factors that could account for the disease symptoms of infected humans, namely, diarrhea, nausea, and abdominal cramps. The pathogenicity of V. parahaemolyticus correlates well with the Kanagawa phenomenon (the hemolytic ability of strains grown on Wagatsuma blood agar), implicating the thermostable direct hemolysin (TDH) as the predominant toxin responsible for pathogenicity. TDH-induced hemolysis could be inhibited by the addition of the osmolyte sorbitol to the extracellular solution, supporting the hypothesis that hemolysis occurs through colloid osmosis secondary to an increase in the cation permeability of the membrane. The effect of TDH on cation permeability was investigated by measuring K+ (congener, 86Rb+) influx into human erythrocytes in which the endogenous cation transporters had been blocked (by use of ouabain, bumetanide, and nitrendipine). TDH increased K+ influx into these cells; this increase was rapid in onset and constant in magnitude, suggesting a direct action by TDH on the membrane. The kinetics of leak generation were examined; the relationship between counts accumulated and hematocrit indicated that the TDH-induced lesion is multihit in nature. TDH-induced K+ influx was sensitive to Zn2+. Time courses of hemolysis in isosmotic solutions of monovalent cation chlorides were used to obtain the selectivity series for the TDH-induced leak: Cs+ > Li+ > K+ > Rb+ > Na+. Both the Zn2+ sensitivity and this selectivity series were obtained for crude culture supernatants, suggesting that TDH is the predominant leak-inducing agent. Thus, we have identified several features of the TDH-induced leak likely to be important in the diarrhetic action of V. parahaemolyticus in the human intestine.
Infection and Immunity 10/1993; 61(10):4326-32. · 4.16 Impact Factor