Long-term persistence of cellular immunity to Oka vaccine virus induced by pernasal co-administration with Escherichia coli enterotoxin in mice

Immunochromatographic detection of the heat-labile enterotoxin of enterotoxigenic Escherichia coli with cross-detection of cholera toxin

Here, we report the development of an immunochromatographic test strip that can detect heat-labile enterotoxin (LT) produced by enterotoxigenic Escherichia coli. Five types of monoclonal antibody (mAb)-producing hybridomas were isolated: three mAbs were A subunit specific and two were B subunit specific. Four mAbs also cross-reacted with both LT proteins derived from swine and human E. coli strains, but only one mAb 57B9 additionally cross-reacted with cholera toxin. Thus, mAb 57B9 was used to form a gold colloid-conjugated antibody for the immunochromatographic test by combination with polyclonal anti-LT rabbit IgG. This test strip detected not only LT in the culture supernatant of LT gene-positive strains, but also cholera toxin in the culture supernatant of Vibrio cholerae. These results indicate that this test strip is suitable for the diagnosis of both enterotoxigenic E. coli and V. cholerae infection.

Escherichia coli cytotoxic necrotizing factor 1 (CNF1): toxin biology, in vivo applications and therapeutic potential

CNF1 is a protein toxin produced by certain pathogenic strains of Escherichia coli. It permanently activates the regulatory Rho, Rac, and Cdc42 GTPases in eukaryotic cells, by deamidation of a glutamine residue. This modification promotes new activities in cells, such as gene transcription, cell proliferation and survival. Since the Rho GTPases play a pivotal role also in several processes in vivo, the potentiality of CNF1 to act as a new pharmacological tool has been explored in experimental animals and in diverse pathological contexts. In this review, we give an update overview on the potential in vivo applications of CNF1.

Mucosal adjuvant activity of oligomannose-coated liposomes for nasal immunization

In the present study, we investigated the effectiveness of liposomes coated with a neoglycolipid consisting of mannotriose and dipalmitoylphosphatidylcholine (Man3-DPPE) as an adjuvant for induction of mucosal immunity. Immunization of BALB/c mice with ovalbumin (OVA)-encapsulated Man3-DPPE-coated liposomes (oligomannose-coated liposomes; OMLs) by a nasal route produced high levels of OVA-specific IgG and IgA antibodies in serum of immunized mice 1 week after the last nasal immunization, whereas no significant serum antibody responses were observed in mice that received OVA in uncoated liposomes or OVA alone. Seven weeks after the last nasal immunization, nasal challenge with an excess amount of OVA in mice that had received OVA/OMLs led to an anamnestic response to the antigen that resulted in 5- to 10-fold increases of antigen-specific serum IgG and IgA antibodies. Only mice immunized nasally with OML/OVA secreted antigen-specific secretory IgA in nasal washes and produced interferon-gamma secreting cells in nasopharyngeal-associated lymphoreticular tissue. Taken together, these results show that nasal administration of OMLs induces mucosal and systemic immunity that are specific for the entrapped antigen in the liposomes. Thus, liposomes coated with synthetic neoglycolipids might be useful as adjuvants for induction of mucosal immunity.

Adjuvants modulating mucosal immune responses or directing systemic responses towards the mucosa

In developing veterinary mucosal vaccines and vaccination strategies, mucosal adjuvants are one of the key players for inducing protective immune responses. Most of the mucosal adjuvants seem to exert their effect via binding to a receptor/or target cells and these properties were used to classify the mucosal adjuvants reviewed in the present paper: (1) ganglioside receptor-binding toxins (cholera toxin, LT enterotoxin, their B subunits and mutants); (2) surface immunoglobulin binding complex CTA1-DD; (3) TLR4 binding lipopolysaccharide; (4) TLR2-binding muramyl dipeptide; (5) Mannose receptor-binding mannan; (6) Dectin-1-binding ss 1,3/1,6 glucans; (7) TLR9-binding CpG-oligodeoxynucleotides; (8) Cytokines and chemokines; (9) Antigen-presenting cell targeting ISCOMATRIX and ISCOM. In addition, attention is given to two adjuvants able to prime the mucosal immune system following a systemic immunization, namely 1alpha, 25(OH)2D3 and cholera toxin.

A mutant of Escherichia coli enterotoxin inducing a specific Thl-type of T cells to varicella-zoster vaccine enhances the production of IL-12 by IFNgamma-stimulated macrophages

A mutant of Escherichia coli enterotoxin induces specific Thl-type T cells to varicella-zoster vaccine. The mutant increased IL-12p40, TNFalpha and nitric oxide production by IFNgamma-stimulated bone marrow macrophages but cholera toxin did not. Anti-TNFalpha antibodies blocked its stimulation of IL-12p40 production but iNOS inhibitor did not. IL-12p40 and IL-12p35 production was stimulated at the level of mRNA formation by the mutant. Cholera toxin suppressed IL-12beta1 expression by spleen T cells stimulated with anti-CD3 antibodies but the mutant did not. These findings indicate that the mutant may induce Thl-type response to the vaccine through its IL-12 and TNFalpha induction by macrophages.

Induction of cellular immunity to varicella-zoster virus glycoproteins tested with pernasal coadministration of Escherichia coli enterotoxin in mice

A mutant of Escherichia coli enterotoxin promotes the induction of cellular immunity to a live varicella vaccine (the Oka strain) as a mucosal adjuvant in mice. An investigation was carried out to determine which of the purified glycoproteins of the virus among three induced cellular immunity with a single nasal administration. Spleen cells from mice immunized nasally with the vaccine and toxin produced interleukin-2 (IL-2) at the same level on restimulation in vitro with glycoprotein H: glycoprotein L (gH:gL), gB, and gE:gI, but not IL-4. The spleen cells from mice immunized with gH:gL, gB, or gE:gI and toxin produced IL-2 on restimulation with gH:gL, gB, or gE:gI, respectively, and the vaccine, but not IL-4. Immunization with gH:gL and the toxin showed increased thymidine uptake and production of IL-2 and interferon-gamma (IFN-gamma) of the spleen cells, but not IL-4, depending on the dose of gH:gL used for immunization and restimulation in vitro. Purified gE:gI and gB have been reported to be the strongest stimulators of cellular immunity to varicella upon subcutaneous injection and are useful as a subunit vaccine. All the glycoproteins tested are excellent stimulators of cellular immunity to the virus and itself on nasal co-immunization with the toxin.

Hypersensitivity reactions after respiratory sensitization: effect of intranasal peptides containing T-cell epitopes

BACKGROUND

The intranasal administration of peptides containing T-cell epitopes has been shown to inhibit T-cell and antibody responses of mice injected with allergen, but responses to respiratory sensitization might be regulated differently.

OBJECTIVE

This study was designed to examine the effect of intranasal peptide on antigen-induced lung inflammatory responses and delayed hypersensitivity after sensitization by the respiratory mucosa or without sensitization.

METHODS

Mice were treated with an intranasal tolerizing regimen of a peptide containing the major T-cell epitope of Der p 1. Delayed hypersensitivity and lung inflammation to challenge with Der p 1 was measured either without further treatment or after sensitization induced by means of the intranasal administration of Der p 1 with a mutated enterotoxin adjuvant. Lung inflammatory responses were examined by means of lavage and histologic section, and delayed hypersensitivity responses were measured on the basis of ear swelling.

RESULTS

Delayed hypersensitivity reactions were induced in mice treated with intranasal peptide, and large reactions were found in mice given intranasal peptide and sensitized with intranasal Der p 1 and adjuvant. Mice pretreated with peptide and sensitized with Der p 1 had an increased lymphocytic infiltration after allergen-specific challenge, as measured by means of bronchoalveolar lavage and shown histologically. These hypersensitivity results are in contrast to previous data that show tolerance to injected antigen.

CONCLUSIONS

Although the intranasal administration of a peptide containing a T-cell epitope markedly inhibits responses to sensitization produced by the injection of allergen, the peptide induces immune responses and increases hypersensitivity to respiratory sensitization.