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.

Among the various toxins produced by the bacterial species Vibrio cholerae is HlyA, a cytolytic protein commonly called the E1 Tor hemolysin. HlyA is synthesized and processed in a complex manner involving various processed or degraded forms, that may co-purify and complicate the interpretation of biochemical and physiological experiments. In this study a single form of HlyA was purified by gel filtration and chromatofocusing using fast protein liquid chromatography in the presence of protease inhibitors. A 45-fold purification was obtained, with a final recovery of 17% of pure 60,000 mol. wt HlyA. A significant improvement in specific activity to 8.5 x 10(6) Chinese hamster ovary tissue culture units per mg protein was obtained. Physiological activity studies indicated that cytolysis of erythrocytes (hemolysis) was inhibited by oxygen: storage of HlyA under oil, and experimentation in N2-flushed buffers maintained activity. HlyA-mediated lysis of human erythrocytes was characterized by a significant lag phase, followed by a rapid induction of hemolysis. Hemolysis was inhibited by sucrose, an osmotic protectant, suggesting that the initial action of HlyA on erythrocytes is to raise the basal cation permeability of the cell membrane. The most likely cytolytic mechanism is thus the formation of transmembrane lesions such as homopolymer pores in target cells, as has been found for toxins from numerous other bacterial pathogens.

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.

Twenty-four selected non-O1/non-O139 Vibrio cholerae strains were examined for the presence of virulence associated genes like ctxA, tcpA, toxR and the repetitive sequence (RS element). Seventeen of these were isolated from diarrhoeal stool samples while the remaining seven were of local environmental origin. Nine and four respectively of these strains were positive for ctxA and tcpA by Multiplex PCR analysis. The majority (16 out of 18 tested) of the strains (including the four tcpA + strains) contained toxR sequences as determined by another PCR assay. The presence of RS element was demonstrable in ctxA+ strains only. Interestingly, three of these non-O1/non-O139 strains were shown to contain all the three virulence associated genes (ctxA, tcpA and toxR) as well as the RS element. Two of these belonged to serogroups 037 (V2) and 064 (CG15) while the third one (V315-1) was untypable. These three strains also produced cholera toxin, expressed toxin coregulated pilus (TCP) and/or TcpA related antigens when grown under appropriate culture conditions. Southern hybridization analysis of their chromosomal DNA fragments using DNA probes representing ctxA, zot, ace and RS element revealed that the strains V2 and CG15 contained, at least, two complete copies of the CTX genetic element, while the strain V315-1 had three or more copies of the same. Presence of the RS element in these strains led to tandem duplication of the CTX genetic element in the chromosome of V2 and V315-1, but not in CG15 where the copies were likely to be present at different loci. These results also indicate the presence of additional copies of incomplete "core region' with zot and ace genes, but not ctxA, in strains V2 and CG15. The significance of these results in terms of the pathogenic and epidemic potential of V. cholerae strains is discussed.

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.

In 1986, an outbreak of diarrheal disease in Texas was attributed to contaminated iced tea in whichKlebsiella pneumoniaewas the predominant flora. Although the ten strains tested were of different serotypes, they all produced a heat labile enterotoxin. Some of these enterotoxigenic strains (ETKP) also exhibited mannose-resistant hemagglutinins, which were later found to be type 3 MR/K fimbriae. In this study we extended our observations and investigated fimbrial expression, as well as HeLa cell adherence behavior, using negative staining, immunogold labeling, and scanning electron microscopy (SEM).ETKP strains were grown on colonization factor antigen agar overnight at 37° C for expression of fimbriae. The presence of fimbriae and immunogold labeling of the cells was determined as described by Wolfeet al.Antiserum was prepared against purified fimbriae in rabbits and dilutions of primary and secondary antibodies (goat anti-rabbit IgG conjugated with 10 nm gold particles) in phosphate buffered saline, pH 7.2, containing 1 % bovine serum albumin and 0.5% Tween 20 were used to label cells.

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.

We examined envelope protein profiles, chromosomal restriction endonuclease digest patterns, and immune responses to envelope proteins for collections of Salmonella typhi strains isolated in Peru and Indonesia. Only minor differences in envelope protein patterns were apparent among strains. Strains from 7 of 20 Indonesian patients had a distinct chromosomal digest pattern compared with patterns of Peruvian and other Indonesian strains. Strains with this pattern carried the gene for the j flagellar antigen (H1-j); differences in response to envelope proteins of j and d strains were noted on immunoblot analysis. Our data suggest that there are genotypic and phenotypic differences among S. typhi strains. The clinical importance of these differences remains to be fully evaluated; however, in this study it was not possible to show a clear correlation between strain characteristics and disease severity.

A functional tcpA gene, encoding the major subunit of toxin-coregulated pili (TCP), is necessary for Vibrio cholerae O1 Ogawa strain 395 to colonize the human intestine and confer protective immunity to virulent challenge. The immunogenicity of TCP and other antigens in experimental and naturally acquired cholera was determined. Seroconversion to cholera toxin (CT), whole cell preparations, and to Ogawa lipopolysaccharide but not to purified native TCP or to a TcpA mimiotope was found in volunteers. Local intestinal secretory immunoglobulin A from volunteers showed conversions to cholera toxin and lipopolysaccharide but not to TCP. Cholera patients in Indonesia showed a seroconversion rate to TCP of 3 of 6 and a seroconversion to a TcpA mimiotope of 1 of 6. Volunteer and patient sera showed similar vibriocidal seroconversions when assayed against either TCP-positive and TCP-negative V. cholerae O1 strains, suggesting that TCP do not contribute demonstrably to the vibriocidal antigen. We conclude that although seroconversion to TCP can occur in naturally acquired cholera, solid long-term protection can be engendered in the absence of a detectable anti-TCP immune response.

The leukocidal activity of the Vibrio cholerae hemolysin (HlyA) was utilized to detect, enrich, and clone hybridoma cells expressing neutralizing monoclonal antibody in a new survivor selection protocol. A bank of 550 hybridoma clones was obtained from a mouse immunized with hemolysin by using standard techniques. The hybridoma bank was treated with a dose of HlyA hemolysin lethal to nonimmune clones. Five surviving hybridoma clones (X1 through X5) which possessed anti-HlyA activity were obtained. Western immunoblot analysis of V. cholerae culture supernatants with monoclonal antibody from clone X1 identified proteins with Mrs of 83,200, 71,600, and 60,300. Amino-terminal sequence analysis of the 71,600-Mr and 60,300-Mr forms showed homology with the published predicted sequence of HlyA. Our data indicate that proteolytic cleavage occurs between residues 120 and 121 (Glu-Leu) of the 83,200-Mr form, producing the 71,600-Mr form with the terminus NH2-L-L-F-T-P-F-D-Q-A-E-E-. Cleavage between residues 150 and 151 (Gly-Phe) releases the 60,300-Mr form with the terminus NH2-F-A-S-P-A-P-A-N-S-E-. Calculations based on the DNA sequence and the N termini indicated that the actual molecular masses of the 83,200-, 71,600-, and 60,300-Mr forms were, respectively, 79.4 kilodaltons (kDa), 68.6 kDa, and 65.3 kDa. Survivor selection and amino-terminal microsequencing offer powerful tools for the analysis of leukotoxic agents.

Enterotoxigenic Escherichia coli fimbriae are immunogenic and play a key role in intestinal colonization. Native colonization factor antigen I, coli surface antigen 1, and coli surface antigen 3 fimbriae were purified by a common method involving shearing, differential centrifugation, gel filtration, and density gradient ultracentrifugation. The compositions and N-terminal sequences were determined. Coli surface antigen 3 possesses two N-terminal isoforms, one of which matches the published DNA sequence, except for the previously proposed signal sequence cleavage point.

Conference Article| December 01 1985 The molecular mass of Vibro cholerae haemolysin measured by radiation inactivation ROBERT H. HALL; ROBERT H. HALL *Department of Medical Microbiology, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, U.K. Search for other works by this author on: This Site PubMed Google Scholar ANDREW C. HALL; ANDREW C. HALL †Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, U.K. Search for other works by this author on: This Site PubMed Google Scholar J. CLIVE ELLORY; J. CLIVE ELLORY †Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, U.K. Search for other works by this author on: This Site PubMed Google Scholar CHRISTOPHER W. SUTTON; CHRISTOPHER W. SUTTON *Department of Medical Microbiology, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, U.K. Search for other works by this author on: This Site PubMed Google Scholar DAVID A. BROADBENT DAVID A. BROADBENT *Department of Medical Microbiology, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, U.K. Search for other works by this author on: This Site PubMed Google Scholar Biochem Soc Trans (1985) 13 (6): 1251–1252. https://doi.org/10.1042/bst0131251 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Cite Icon Cite Get Permissions Citation ROBERT H. HALL, ANDREW C. HALL, J. CLIVE ELLORY, CHRISTOPHER W. SUTTON, DAVID A. BROADBENT; The molecular mass of Vibro cholerae haemolysin measured by radiation inactivation. Biochem Soc Trans 1 December 1985; 13 (6): 1251–1252. doi: https://doi.org/10.1042/bst0131251 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Society Transactions Search Advanced Search Keywords: CT, cholera toxin, SDS, sodium dodecyl sulphate This content is only available as a PDF. © 1985 Biochemical Society1985 Article PDF first page preview Close Modal You do not currently have access to this content.