Size and Structure of the Cholera Toxin Molecule and Its Subunits

Ohtomo, Nobuya; Muraoka, Toyoharu; Tashiro, Akari; Zinnaka, Yutaka; Amako, Kazunobu

doi:10.1093/infdis/133.supplement_1.s31

Cited by 85 publications

(39 citation statements)

References 14 publications

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“…First, our constructs are intended to be retained in transfected cells and therefore lack the A2 subdomain that may have negatively influenced the outcomes of their A-subunit-only studies. In this regard, the A2 subdomains facilitate the binding to the B pentamers (43). The A2 subdomains of both CT and LT also obscure their hydrophobic ARF binding faces (26).…”

Section: Discussionmentioning

confidence: 99%

“…CT and LT are AB5 enterotoxins produced by Vibrio cholerae and E. coli, respectively. CT and LT consist of catalytic A subunits (separated into A1 and A2 subdomains) anchored in rings of five identical B subunits (43). Their enzymatic active sites reside within the A1 subdomains, while the A2 subdomains anchor the A subunits into the B pentamers (43).…”

mentioning

confidence: 99%

“…CT and LT consist of catalytic A subunits (separated into A1 and A2 subdomains) anchored in rings of five identical B subunits (43). Their enzymatic active sites reside within the A1 subdomains, while the A2 subdomains anchor the A subunits into the B pentamers (43). The B pentamers of CT and LT bind to gangliosides on cell membranes and facilitate their entry into lysosomes (23).…”

mentioning

confidence: 99%

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Adjuvant Activity of the Catalytic A1 Domain of Cholera Toxin for Retroviral Antigens Delivered by GeneGun

Bagley¹,

Lewis²,

Fouts³

2011

Clin. Vaccine Immunol.

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Most DNA-encoded adjuvants enhance immune responses to DNA vaccines in small animals but are less effective in primates. Here, we characterize the adjuvant activity of the catalytic A1 domain of cholera toxin (CTA1) for human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) antigens in mice and macaques delivered by GeneGun. The inclusion of CTA1 with SIVmac239 Gag dramatically enhanced anti-Gag antibody responses in mice. The adjuvant effects of CTA1 for the secreted antigen HIV gp120 were much less pronounced than those for Gag, as the responses to gp120 were high in the absence of an adjuvant. CTA1 was a stronger adjuvant for Gag than was granulocyte-macrophage colony-stimulating factor (GM-CSF), and it also displayed a wider dose range than GM-CSF in mice. In macaques, CTA1 modestly enhanced the antibody responses to SIV Gag but potently primed for a recombinant Gag protein boost. The results of this study show that CTA1 is a potent adjuvant for SIV Gag when delivered by GeneGun in mice and that CTA1 provides a potent GeneGun-mediated DNA prime for a heterologous protein boost in macaques.Most DNA vaccines have translated poorly from mice to primates. The exact reasons for this loss of potency are not fully elucidated. This topic is discussed in detail in references 11, 13, 31, and 32. Two strategies to improve the immunogenicity of DNA vaccines for cellular and/or humoral immune responses have evolved in recent years. One utilizes enhanced delivery of the DNA using ballistic particle bombardment with the GeneGun (14) or in vivo electroporation (3). The other main strategy entails the use of plasmid mixtures that combine the DNA vaccine of interest with a plasmid that expresses an adjuvant. The best-studied DNA adjuvants are based on cytokines (9,25,29,30,48) or chemokines (33,53,54). Although several of these adjuvant approaches have shown great promise in small animal models, most have been disappointing in humans and nonhuman primates (11,13,32).Cholera toxin (CT) and the highly related heat-labile enterotoxin of Escherichia coli (LT) have been found to be powerful mucosal immunogens and adjuvants (reviewed in reference 34). In mice, antibody (Ab) responses to CT and bystander antigens last at least 2 years (35, 50). We previously showed that the adjuvant properties of CT can be incorporated into DNA vaccines delivered intramuscularly (i.m.) (7). CT and LT are AB5 enterotoxins produced by Vibrio cholerae and E. coli, respectively. CT and LT consist of catalytic A subunits (separated into A1 and A2 subdomains) anchored in rings of five identical B subunits (43). Their enzymatic active sites reside within the A1 subdomains, while the A2 subdomains anchor the A subunits into the B pentamers (43). The B pentamers of CT and LT bind to gangliosides on cell membranes and facilitate their entry into lysosomes (23). The A1 subdomains are cleaved from the A2 subdomains in the Golgi complex or the endoplasmic reticulum (ER), and then the A1 subdomains exploit host protein retention and degradatio...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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Adjuvant Activity of the Catalytic A1 Domain of Cholera Toxin for Retroviral Antigens Delivered by GeneGun

Bagley¹,

Lewis²,

Fouts³

2011

Clin. Vaccine Immunol.

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“…Since this enterotoxin is a protein, its entrance into the cell is based upon the assumption that only the "subunit A" can be transported across the cell membrane [22,23]. According to the present findings, the process of cellular internalization of cholera toxin should not be considered uniform in different body cells.…”

Section: Discussionmentioning

confidence: 74%

Changes in tissue cyclic AMP concentrations following an intravenous lethal dose of cholera enterotoxin in rabbits

Liu

Galloway

1981

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“…CT and LT are AB5 enterotoxins consisting of a 27-kDa catalytic A domain anchored in a pentamer of identical 11.7-kDa B subunits (28). The B pentamer of CT (CTB) binds exclusively to GM1 gangliosides on the surfaces of cells, while the B pentamer of LT (LTB) binds to other gangliosides in addition to GM1 (16,20).…”

mentioning

confidence: 99%

An Enzymatically Active A Domain Is Required for Cholera-Like Enterotoxins To Induce a Long-Lived Blockade on the Induction of Oral Tolerance: New Method for Screening Mucosal Adjuvants

et al. 2003

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The cholera-like enterotoxins (CLETS), cholera toxin (CT) and Escherichia coli heat-labile toxin (LT), are powerful mucosal adjuvants. Here we show that these toxins also induce a long-lived blockade (of at least 6 months) on the induction of oral tolerance when they are coadministered with the antigen ovalbumin. Strikingly, only enzymatically active CLETS induced this blockade on the induction of oral tolerance. In this regard, the enzymatically inactive mutants of CT and LT, CTK63 and LTK63, and their recombinant B pentamers, rCTB and rLTB, failed to block the induction of oral tolerance, demonstrating a stringent requirement for an enzymatically active A domain in this phenomenon. Together with the results of other recent studies, these results indicate that the enzymatic activity of CLETS, most likely cyclic AMP elevation, is responsible for their adjuvant effects. The results of this study also indicate that measuring the ability of putative mucosal adjuvants to block the induction of oral tolerance may be a superior method for measuring mucosal adjuvanticity.Oral tolerance is a state of systemic hyporesponsiveness that occurs after the ingestion of protein antigens and is thought to be important for the maintenance of homeostasis between the immune system and food antigens (33). Systemic challenge with an antigen in Freund's adjuvant following prior oral administration of that antigen results in diminished antibody and cytolytic responses (36). Feeding of a single high dose or multiple low doses of a protein antigen induces oral tolerance to that antigen (33). The mechanism of oral tolerance is poorly understood; however, at least two independent mechanisms appear to be involved. First, feeding of a high dose of antigen induces clonal T-cell anergy or deletion, as evidenced by reduced interleukin-2 production and a lack of T-cell proliferation (8, 27, 37). Second, feeding of multiple low doses of antigen induces suppressor T cells that secrete transforming growth factor ␤ (9, 22). Interestingly, mucosal adjuvants such as the cholera-like enterotoxins (CLETS), cholera toxin (CT), and Escherichia coli heat-labile enterotoxin (LT) block the induction of oral tolerance when coadministered with an antigen. In the present study, we determined whether the blockade on the induction of oral tolerance to antigens induced by CLETS is transient or long-lived and what role the enzymatic activity of the toxins plays in this phenomenon.CT and LT are AB5 enterotoxins consisting of a 27-kDa catalytic A domain anchored in a pentamer of identical 11.7-kDa B subunits (28). The B pentamer of CT (CTB) binds exclusively to GM1 gangliosides on the surfaces of cells, while the B pentamer of LT (LTB) binds to other gangliosides in addition to GM1 (16,20). These toxins exploit the host protein retention and degradation pathways to gain access to the cytoplasm (reviewed in reference 19). In the cytosol, their A1 subunits catalyze the transfer of an ADP-ribose from NAD to stimulatory alpha subunits of G proteins. After ADP ribosylatio...

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Size and Structure of the Cholera Toxin Molecule and Its Subunits

Cited by 85 publications

References 14 publications

Adjuvant Activity of the Catalytic A1 Domain of Cholera Toxin for Retroviral Antigens Delivered by GeneGun

Adjuvant Activity of the Catalytic A1 Domain of Cholera Toxin for Retroviral Antigens Delivered by GeneGun

Changes in tissue cyclic AMP concentrations following an intravenous lethal dose of cholera enterotoxin in rabbits

An Enzymatically Active A Domain Is Required for Cholera-Like Enterotoxins To Induce a Long-Lived Blockade on the Induction of Oral Tolerance: New Method for Screening Mucosal Adjuvants

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