Enhanced protective immune responses against Salmonella Enteritidis infection by Salmonella secreting an Escherichia coli heat-labile enterotoxin B subunit protein

ABSTRACTTheEscherichia coliheat-labile enterotoxin B subunit (LTB) is a potent vaccine adjuvant.Salmonella entericaserovar Enteritidis ghosts carrying LTB (S. Enteritidis-LTB ghosts) were genetically constructed using a novel plasmid, pJHL187-LTB, designed for the coexpression of the LTB and E lysis proteins.S. Enteritidis-LTB ghosts were characterized using scanning electron microscopy to visualize their transmembrane tunnel structures. The expression of LTB inS. Enteritidis-LTB ghost preparations was confirmed by immunoblot and enzyme-linked immunosorbent assays. The parenteral adjuvant activity of LTB was demonstrated by immunizing chickens with eitherS. Enteritidis-LTB ghosts orS. Enteritidis ghosts. Chickens were intramuscularly primed at 5 weeks of age and subsequently boosted at 8 weeks of age. In total, 60 chickens were equally divided into three groups (n= 20 for each): group A, nonvaccinated control; group B, immunized withS. Enteritidis-LTB ghosts; and group C, immunized withS. Enteritidis ghosts. Compared with the nonimmunized chickens (group A), the immunized chickens (groups B and C) exhibited increased titers of plasma IgG and intestinal secretory IgA antibodies. The CD3+CD4+subpopulation of T cells was also significantly increased in both immunized groups. Among the immunized chickens, those in group B exhibited significantly increased titers of specific plasma IgG and intestinal secretory IgA (sIgA) antibodies compared with those in group C, indicating the immunomodulatory effects of the LTB adjuvant. Furthermore, both immunized groups exhibited decreased bacterial loads in their feces and internal organs. These results indicate that parenteral immunization withS. Enteritidis-LTB ghosts can stimulate superior induction of systemic and mucosal immune responses compared to immunization withS. Enteritidis ghosts alone, thus conferring efficient protection against salmonellosis.

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The B subunits of cholera and Escherichia coli heat-labile toxins enhance the immune responses in mice orally immunised with a recombinant live P-fimbrial vaccine for avian pathogenic E. coli

Acta Veterinaria Hungarica ◽

10.1556/avet.2014.006 ◽

2014 ◽

Vol 62 (3) ◽

pp. 293-303

Author(s):

In-Gyeong Oh ◽

Chetan Jawale ◽

John Lee

Keyword(s):

Escherichia Coli ◽

Immune Responses ◽

Cholera Toxin B Subunit ◽

Adjuvant Effect ◽

Toxin B ◽

E Coli ◽

Cholera Toxin B ◽

B Subunit ◽

Heat Labile ◽

Enterotoxin B

This study aimed to investigate the adjuvant effect of recombinant attenuatedSalmonellaexpressing cholera toxin B subunit (CTB) andEscherichia coliheat-labile enterotoxin B subunit (LTB) for the P-fimbriae subunit-based vaccine of avian pathogenicE. coli(APEC) in a murine model. The PapA-specific sIgA and IgG responses were significantly enhanced after immunisation with theSalmonella-PapA vaccine in the presence of CTB or LTB. The group immunised with theSalmonella-LTB strain promoted Th1-type immunity, whereas that immunised with theSalmonella-CTB strain produced Th2-type immunity. We concluded that bothSalmonella-CTB and -LTB strains can enhance the immune response to PapA, and that the LTB strain may be a more effective adjuvant for APEC vaccination, which requires higher Th1-type immunity for protection. Thus, our findings provide evidence that immunisation with an adjuvant, LTB, is one of the strategies of developing effective vaccines against P-fimbriated APEC.

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Tissue culture and expression of Escherichia coli heat-labile enterotoxin B subunit in transgenic Peperomia pellucida

Protein Expression and Purification ◽

10.1016/j.pep.2010.02.010 ◽

2010 ◽

Vol 72 (1) ◽

pp. 82-86 ◽

Cited By ~ 11

Author(s):

Nguyen Hoang Loc ◽

Nguyen Hoang Bach ◽

Tae-Geum Kim ◽

Moon-Sik Yang

Keyword(s):

Escherichia Coli ◽

Tissue Culture ◽

B Subunit ◽

Heat Labile ◽

Enterotoxin B

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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.

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