Oral immunization of mice with a glycoconjugate vaccine containing the O157 antigen of <i>Escherichia coli</i> O157:H7 admixed with cholera toxin fails to elicit protection against subsequent colonization by the pathogen

It has been postulated that a humoral immune response directed against the O157 antigen of Escherichia coli O157:H7, and expressed in the intestine, might afford protection from colonization and consequent infection by this enteric pathogen. The present study was conducted to determine whether such an immune response can be experimentally generated in mice. To this end, mice were orally immunized with a glycoconjugate vaccine consisting of horse serum albumin and the O157 polysaccharide admixed with the mucosal adjuvant, cholera toxin. Mice consistently developed robust local and systemic immune responses to the cholera toxin adjuvant, but were far from uniformly reactive to the test vaccine. Moreover, vaccinated mice were as susceptible to transient intestinal colonization following challenge with an isolate of E. coli O157:H7 as unvaccinated control mice. These results indicate that this vaccination approach is unlikely to be straightforward in target bovine or human hosts.Key words: Escherichia coli O157:H7, glycoconjugate vaccine, mucosal immunity, mice.

Download Full-text

Humoral and cellular immune responses in the murine respiratory tract following oral immunization with cholera toxin or Escherichia coli heat-labile enterotoxin

Vaccine ◽

10.1016/0264-410x(95)00231-o ◽

1996 ◽

Vol 14 (8) ◽

pp. 792-798 ◽

Cited By ~ 17

Author(s):

Christiane Ruedl ◽

Claudia Rieser ◽

Nikolaus Kofler ◽

Georg Wick ◽

Hugo Wolf

Keyword(s):

Escherichia Coli ◽

Immune Responses ◽

Respiratory Tract ◽

Cholera Toxin ◽

Oral Immunization ◽

Cellular Immune Responses ◽

Heat Labile ◽

Cellular Immune

Download Full-text

A genetically detoxified derivative of heat-labile Escherichia coli enterotoxin induces neutralizing antibodies against the A subunit.

Journal of Experimental Medicine ◽

10.1084/jem.180.6.2147 ◽

1994 ◽

Vol 180 (6) ◽

pp. 2147-2153 ◽

Cited By ~ 69

Author(s):

M Pizza ◽

M R Fontana ◽

M M Giuliani ◽

M Domenighini ◽

C Magagnoli ◽

...

Keyword(s):

Escherichia Coli ◽

Cholera Toxin ◽

Neutralizing Antibodies ◽

Site Directed Mutagenesis ◽

Directed Mutagenesis ◽

E Coli ◽

Heat Labile ◽

A Subunit ◽

Adp Ribosyltransferase ◽

Derivatives Of

Escherichia coli enterotoxin (LT) and the homologous cholera toxin (CT) are A-B toxins that cause travelers' diarrhea and cholera, respectively. So far, experimental live and killed vaccines against these diseases have been developed using only the nontoxic B portion of these toxins. The enzymatically active A subunit has not been used because it is responsible for the toxicity and it is reported to induce a negligible titer of toxin neutralizing antibodies. We used site-directed mutagenesis to inactivate the ADP-ribosyltransferase activity of the A subunit and obtained nontoxic derivatives of LT that elicited a good titer of neutralizing antibodies recognizing the A subunit. These LT mutants and equivalent mutants of CT may be used to improve live and killed vaccines against cholera and enterotoxinogenic E. coli.

Download Full-text

Biochemical and structural characterization of the novel sialic acid-binding site of Escherichia coli heat-labile enterotoxin LT-IIb

Biochemical Journal ◽

10.1042/bcj20160575 ◽

2016 ◽

Vol 473 (21) ◽

pp. 3923-3936 ◽

Cited By ~ 3

Author(s):

Dani Zalem ◽

João P. Ribeiro ◽

Annabelle Varrot ◽

Michael Lebens ◽

Anne Imberty ◽

...

Keyword(s):

Escherichia Coli ◽

Binding Site ◽

Cholera Toxin ◽

Carbohydrate Binding ◽

Type I ◽

Type Ii ◽

E Coli ◽

B Subunit ◽

Heat Labile ◽

B Subunits

The structurally related AB5-type heat-labile enterotoxins of Escherichia coli and Vibrio cholerae are classified into two major types. The type I group includes cholera toxin (CT) and E. coli LT-I, whereas the type II subfamily comprises LT-IIa, LT-IIb and LT-IIc. The carbohydrate-binding specificities of LT-IIa, LT-IIb and LT-IIc are distinctive from those of cholera toxin and E. coli LT-I. Whereas CT and LT-I bind primarily to the GM1 ganglioside, LT-IIa binds to gangliosides GD1a, GD1b and GM1, LT-IIb binds to the GD1a and GT1b gangliosides, and LT-IIc binds to GM1, GM2, GM3 and GD1a. These previous studies of the binding properties of type II B-subunits have been focused on ganglio core chain gangliosides. To further define the carbohydrate binding specificity of LT-IIb B-subunits, we have investigated its binding to a collection of gangliosides and non-acid glycosphingolipids with different core chains. A high-affinity binding of LT-IIb B-subunits to gangliosides with a neolacto core chain, such as Neu5Gcα3- and Neu5Acα3-neolactohexaosylceramide, and Neu5Gcα3- and Neu5Acα3-neolactooctaosylceramide was detected. An LT-IIb-binding ganglioside was isolated from human small intestine and characterized as Neu5Acα3-neolactohexaosylceramide. The crystal structure of the B-subunit of LT-IIb with the pentasaccharide moiety of Neu5Acα3-neolactotetraosylceramide (Neu5Ac-nLT: Neu5Acα3Galβ4GlcNAcβ3Galβ4Glc) was determined providing the first information for a sialic-binding site in this subfamily, with clear differences from that of CT and LT-I.

Download Full-text

Escherichia coli Heat-Labile Enterotoxin B Subunit Is a More Potent Mucosal Adjuvant than Its Closely Related Homologue, the B Subunit of Cholera Toxin

Infection and Immunity ◽

10.1128/iai.69.5.3476-3482.2001 ◽

2001 ◽

Vol 69 (5) ◽

pp. 3476-3482 ◽

Cited By ~ 57

Author(s):

Douglas G. Millar ◽

Timothy R. Hirst ◽

Denis P. Snider

Keyword(s):

Escherichia Coli ◽

Cholera Toxin ◽

Lymphocyte Proliferation ◽

Vaccine Adjuvants ◽

B Subunit ◽

Heat Labile ◽

Antibody Titers ◽

Enterotoxin B ◽

Draining Lymph Nodes ◽

Stimulation Of

ABSTRACT Although cholera toxin (Ctx) and Escherichia coliheat-labile enterotoxin (Etx) are known to be potent mucosal adjuvants, it remains controversial whether the adjuvanticity of the holotoxins extends to their nontoxic, receptor-binding B subunits. Here, we have systematically evaluated the comparative adjuvant properties of highly purified recombinant EtxB and CtxB. EtxB was found to be a more potent adjuvant than CtxB, stimulating responses to hen egg lysozyme when the two were coadministered to mice intranasally, as assessed by enhanced serum and secretory antibody titers as well as by stimulation of lymphocyte proliferation in spleen and draining lymph nodes. These results indicate that, although structurally very similar, EtxB and CtxB have strikingly different immunostimulatory properties and should not be considered equivalent as prospective vaccine adjuvants.

Download Full-text

The early cellular and humoral immune response to primary and booster oral immunization with cholera toxin B subunit

European Journal of Immunology ◽

10.1002/eji.1830210917 ◽

1991 ◽

Vol 21 (9) ◽

pp. 2087-2094 ◽

Cited By ~ 31

Author(s):

David J. M. Lewis ◽

Pavel Novotny ◽

Gordon Dougan ◽

George E. Griffin

Keyword(s):

Immune Response ◽

Cholera Toxin ◽

Humoral Immune Response ◽

Oral Immunization ◽

Cholera Toxin B Subunit ◽

Toxin B ◽

Cholera Toxin B ◽

Humoral Immune ◽

B Subunit

Download Full-text

Effects of Oral Vaccination and Immunomodulation by Cholera Toxin on Experimental Helicobacter pylori Infection, Reinfection, and Gastritis

Infection and Immunity ◽

10.1128/iai.70.8.4621-4627.2002 ◽

2002 ◽

Vol 70 (8) ◽

pp. 4621-4627 ◽

Cited By ~ 42

Author(s):

S. Raghavan ◽

A.-M. Svennerholm ◽

J. Holmgren

Keyword(s):

Helicobacter Pylori ◽

Cholera Toxin ◽

Mononuclear Cells ◽

Oral Treatment ◽

Bacterial Load ◽

Oral Immunization ◽

Initial Infection ◽

Fold Reduction ◽

H Pylori

ABSTRACT Therapeutic vaccination is an attractive strategy to control infection and disease caused by Helicobacter pylori. In mice infected with H. pylori we have studied the protective effect of oral immunization with an H. pylori lysate preparation given together with the mucosal adjuvant cholera toxin (CT), both against the initial infection and against a later reinfection challenge. We have also examined the effects of treatment with the CT adjuvant alone on H. pylori infection and reinfection. Specific immunization with lysate was found to result in a sixfold reduction of the extent (bacterial load) of the primary infection and also to provide similar levels of protection against reinfection. However, these effects were associated with severe postimmunization gastritis. In contrast, oral treatment with CT alone at the time of initial infection, while unable to suppress the initial infection, gave rise to a 20-fold reduction in bacterial load upon reinfection without causing any associated gastric inflammation. Both the infected animals that were specifically immunized and those that were treated with CT only displayed increased in vitro proliferative responses of mononuclear cells to H. pylori antigens. Antibody levels in response to H. pylori were on the other hand only marginally increased after treatment with CT, whereas they were markedly elevated after immunization with lysate plus CT, with a rise in both (Th2-driven) immunoglobulin G1 (IgG1) and, especially, (Th1-driven) IgG2a antibodies. The results illustrate the complex balance between protection and harmful inflammation after postinfection vaccination against H. pylori as studied in a mouse model.

Download Full-text