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The Divergent CD8+ T Cell Adjuvant Properties of LT-IIb and LT-IIc, Two Type II Heat-Labile Enterotoxins, Are Conferred by Their Ganglioside-Binding B Subunits.

Hu JC, Greene CJ, King-Lyons ND, Connell TD - PLoS ONE (2015)

Bottom Line: Comparing the immune potentiating characteristics of both native and chimeric HLT adjuvants, it was found that not all the adjuvant characteristics of the HLT adjuvants were modulated by the respective B subunits.However, induction of IL-1 from macrophages and the capacity to intoxicate cells in a mouse Y1 adrenal cell bioassay did not correlate with the B subunits.Therefore, it is likely that additional factors other than the B subunits contribute to the effects elicited by the HLT adjuvants.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology & Immunology, The Witebsky Center for Microbial Pathogenesis and Immunology, The University at Buffalo, Buffalo, New York, United States of America.

ABSTRACT
Poor immune responses elicited by vaccine antigens can be enhanced by the use of appropriate adjuvants. Type II heat-labile enterotoxins (HLT) produced by Escherichia coli are extremely potent adjuvants that augment both humoral and cellular immunity to co-administered antigens. Recent findings demonstrate that LT-IIb and LT-IIc, two type II HLT adjuvants, exhibit potent, yet distinguishable CD8(+) T cell adjuvant properties. While LT-IIc elicits a robust and rapid response at one week after administration, LT-IIb engenders a more gradual and slower expansion of antigen-specific CD8(+) T cells that correlates with improved immunity. The variations in immune effects elicited by the HLT adjuvants have been generally attributed to their highly divergent B subunits that mediate binding to various gangliosides on cell surfaces. Yet, HLT adjuvants with point mutations in the B subunit that significantly alter ganglioside binding retain similar adjuvant functions. Therefore, the contribution of the B subunits to adjuvanticity remains unclear. To investigate the influence of the B subunits on the enhancement of immune responses by LT-IIb and LT-IIc, chimeric HLT were engineered in which the B subunits of the two adjuvants were exchanged. Comparing the immune potentiating characteristics of both native and chimeric HLT adjuvants, it was found that not all the adjuvant characteristics of the HLT adjuvants were modulated by the respective B subunits. Specifically, the differences in the CD8(+) T cell kinetics and protective responses elicited by LT-IIb and LT-IIc did indeed followed their respective B subunits. However, induction of IL-1 from macrophages and the capacity to intoxicate cells in a mouse Y1 adrenal cell bioassay did not correlate with the B subunits. Therefore, it is likely that additional factors other than the B subunits contribute to the effects elicited by the HLT adjuvants.

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Related in: MedlinePlus

Chimeric HLT adjuvants preserve parental B-pentamer ganglioside binding profiles.(A) Modified dot blots with 500 μm of each ganglioside spotted on a grid and probed with 2 μg/mL HLT adjuvant, anti-HLT polyclonal antibodies, and anti-rabbit IgG AF790. (B) Binding of both WT and chimeric HLTs to different gangliosides as normalized to GD1a binding. Data shown (n = 3).
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pone.0142942.g002: Chimeric HLT adjuvants preserve parental B-pentamer ganglioside binding profiles.(A) Modified dot blots with 500 μm of each ganglioside spotted on a grid and probed with 2 μg/mL HLT adjuvant, anti-HLT polyclonal antibodies, and anti-rabbit IgG AF790. (B) Binding of both WT and chimeric HLTs to different gangliosides as normalized to GD1a binding. Data shown (n = 3).

Mentions: The pentameric B subunits of the HLT adjuvants are responsible for binding gangliosides expressed ubiquitously on cell surfaces. To ensure that the chimeric HLT adjuvants preserved their parental ganglioside binding profiles, modified immunodot blots using commercially prepared gangliosides were performed (Fig 2A). As previously reported, LT-IIb binds GM2, GM3, and GD1a, but not GM1, while LT-IIc binds all four of the mentioned gangliosides [22]. Binding to particular gangliosides was dependent upon the B pentamer that was present in the chimeric holotoxins and equivalent to the WT HLT from which the B pentamers were derived. LT-IIcb bound to GM2, GM3, and GD1a, but not to GM1 (Fig 2B). Similarly, LT-IIbc bound to all four gangliosides: GM1, GM2, GM3, and GD1a (Fig 2B).


The Divergent CD8+ T Cell Adjuvant Properties of LT-IIb and LT-IIc, Two Type II Heat-Labile Enterotoxins, Are Conferred by Their Ganglioside-Binding B Subunits.

Hu JC, Greene CJ, King-Lyons ND, Connell TD - PLoS ONE (2015)

Chimeric HLT adjuvants preserve parental B-pentamer ganglioside binding profiles.(A) Modified dot blots with 500 μm of each ganglioside spotted on a grid and probed with 2 μg/mL HLT adjuvant, anti-HLT polyclonal antibodies, and anti-rabbit IgG AF790. (B) Binding of both WT and chimeric HLTs to different gangliosides as normalized to GD1a binding. Data shown (n = 3).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643920&req=5

pone.0142942.g002: Chimeric HLT adjuvants preserve parental B-pentamer ganglioside binding profiles.(A) Modified dot blots with 500 μm of each ganglioside spotted on a grid and probed with 2 μg/mL HLT adjuvant, anti-HLT polyclonal antibodies, and anti-rabbit IgG AF790. (B) Binding of both WT and chimeric HLTs to different gangliosides as normalized to GD1a binding. Data shown (n = 3).
Mentions: The pentameric B subunits of the HLT adjuvants are responsible for binding gangliosides expressed ubiquitously on cell surfaces. To ensure that the chimeric HLT adjuvants preserved their parental ganglioside binding profiles, modified immunodot blots using commercially prepared gangliosides were performed (Fig 2A). As previously reported, LT-IIb binds GM2, GM3, and GD1a, but not GM1, while LT-IIc binds all four of the mentioned gangliosides [22]. Binding to particular gangliosides was dependent upon the B pentamer that was present in the chimeric holotoxins and equivalent to the WT HLT from which the B pentamers were derived. LT-IIcb bound to GM2, GM3, and GD1a, but not to GM1 (Fig 2B). Similarly, LT-IIbc bound to all four gangliosides: GM1, GM2, GM3, and GD1a (Fig 2B).

Bottom Line: Comparing the immune potentiating characteristics of both native and chimeric HLT adjuvants, it was found that not all the adjuvant characteristics of the HLT adjuvants were modulated by the respective B subunits.However, induction of IL-1 from macrophages and the capacity to intoxicate cells in a mouse Y1 adrenal cell bioassay did not correlate with the B subunits.Therefore, it is likely that additional factors other than the B subunits contribute to the effects elicited by the HLT adjuvants.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology & Immunology, The Witebsky Center for Microbial Pathogenesis and Immunology, The University at Buffalo, Buffalo, New York, United States of America.

ABSTRACT
Poor immune responses elicited by vaccine antigens can be enhanced by the use of appropriate adjuvants. Type II heat-labile enterotoxins (HLT) produced by Escherichia coli are extremely potent adjuvants that augment both humoral and cellular immunity to co-administered antigens. Recent findings demonstrate that LT-IIb and LT-IIc, two type II HLT adjuvants, exhibit potent, yet distinguishable CD8(+) T cell adjuvant properties. While LT-IIc elicits a robust and rapid response at one week after administration, LT-IIb engenders a more gradual and slower expansion of antigen-specific CD8(+) T cells that correlates with improved immunity. The variations in immune effects elicited by the HLT adjuvants have been generally attributed to their highly divergent B subunits that mediate binding to various gangliosides on cell surfaces. Yet, HLT adjuvants with point mutations in the B subunit that significantly alter ganglioside binding retain similar adjuvant functions. Therefore, the contribution of the B subunits to adjuvanticity remains unclear. To investigate the influence of the B subunits on the enhancement of immune responses by LT-IIb and LT-IIc, chimeric HLT were engineered in which the B subunits of the two adjuvants were exchanged. Comparing the immune potentiating characteristics of both native and chimeric HLT adjuvants, it was found that not all the adjuvant characteristics of the HLT adjuvants were modulated by the respective B subunits. Specifically, the differences in the CD8(+) T cell kinetics and protective responses elicited by LT-IIb and LT-IIc did indeed followed their respective B subunits. However, induction of IL-1 from macrophages and the capacity to intoxicate cells in a mouse Y1 adrenal cell bioassay did not correlate with the B subunits. Therefore, it is likely that additional factors other than the B subunits contribute to the effects elicited by the HLT adjuvants.

Show MeSH
Related in: MedlinePlus