Redirection of allergen-specific TH2 responses by a modified adenine through Toll-like receptor 7 interaction and IL-12/IFN release

doi:10.1016/j.jaci.2006.05.027

Journal of Allergy and Clinical Immunology

Volume 118, Issue 2, August 2006, Pages 511-517

https://doi.org/10.1016/j.jaci.2006.05.027 Get rights and content

Background

Natural or synthetic ligands of Toll-like receptors (TLRs), such as CpG-containing oligodeoxynucleotides and imidazoquinolines, affect the functional phenotype of antigen-specific human T lymphocytes by inducing cytokine release by cells of the innate immunity.

Objective

In vitro investigation of the ability of substitute adenines (SAs) to affect antigen-presenting cells and shift the functional phenotype of specific human T_H2 cells was performed.

Methods

The functional profile of hapten- and allergen-specific T-cell lines obtained in the absence or presence of modified adenines was assessed by means of quantitative real-time PCR, flow cytometry, and ELISAs. Activation of TLRs was evaluated by means of nucleofection of HEK293 cells.

Results

The synthetic heterocycle, chemically related to adenine with substitution in positions 2-, 8-, and 9- (SA-2), but not its related derivative lacking 2- and 8- substitutions, stimulated the production of high amounts of IL-12, IL-10, TNF-α, and IL-6 by CD14⁺ cells and IFN-α and CXCL10 by blood dendritic cell antigen (BDCA)-4⁺ plasmacytoid dendritic cells. A nuclear factor κB–dependent signaling pathway mediated by SA-2 ligation of TLR7 was responsible for these effects. SA-2 also redirected the in vitro differentiation of either Dermatophagoides pteronyssinus group 1 or amoxicillin-specific T_H2 cells toward the T_H1/T_H0 phenotype, with parallel downregulation of GATA-3 and upregulation of T-box expressed in T cells transcription factors.

Conclusion

Critical substitutions of the adenine backbone confer the ability to activate TLR7, inducing the production of modulatory cytokines able to shift human allergen-specific T_H2 cells to a T_H1/T_H0 phenotype.

Clinical implications

Appropriately modified adenines might be used as effective adjuvants for the development of novel immunotherapeutic strategies of allergic disorders.

Section snippets

Reagents

For information on reagents, see this article's supplementary Methods text in the Online Repository at www.jacionline.org.

Synthesis of modified adenines

See this article's supplementary Methods text in the Online Repository at www.jacionline.org for the synthesis of modified adenine SA-2 and SA-1.¹⁶ The chemical structures of modified adenines are shown in Fig 1.

Subjects

PBMCs were derived from 11 healthy donors, 9 adult amoxicillin-sensitive donors and 5 D pteronyssinus–sensitive atopic volunteers, in accordance with the ethical

SA-2 induces the production of cytokines and chemokines by cells of the innate immunity

The ability of modified adenines to stimulate the cells of the innate immunity was first investigated. Highly purified circulating CD14⁺ cells were derived from 11 healthy donors and stimulated for 36 hours with 6 μM SA-2 or SA-1, and the amounts of IL-12, TNF-α, IL-6, and IL-10 were measured by using ELISAs in the supernatants. As positive controls, LPS (1 μg/mL) and R-848 (6 μM) were used. SA-2, but not SA-1, stimulated the production of regulatory (IL-12 and IL-10) and inflammatory (TNF-α

Discussion

Although the mechanisms responsible for successful immunotherapy in allergic subjects are still matter of debate, they certainly account for the central role of allergen-specific T_H2 cells. Both inhibition of antigen presentation and, more recently, suppression of T_H responses by regulatory cells have been suggested, but most investigations addressed immune deviation from T_H2 cells toward a less pathogenic T_H1 phenotype.¹⁹ Actually, CD4⁺ T cells from nonatopic subjects produce IFN-γ and little

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Supported by funds from the European Community (project QLK3-CT-2002-02026), Associazione Italiana per la Ricerca sul Cancro, and Ministero dell'Università e della Ricerca Scientifica.

Disclosure of potential conflict of interest: The authors have declared that they have no conflict of interest.

View full text

Basic and clinical immunologyRedirection of allergen-specific TH2 responses by a modified adenine through Toll-like receptor 7 interaction and IL-12/IFN release

Background

Objective

Methods

Results

Conclusion

Clinical implications

Section snippets

Reagents

Synthesis of modified adenines

Subjects

SA-2 induces the production of cytokines and chemokines by cells of the innate immunity

Discussion

J Allergy Clin Immunol

J Allergy Clin Immunol

J Allergy Clin Immunol

J Allergy Clin Immunol

J Allergy Clin Immunol

J Allergy Clin Immunol

Vaccine

Curr Opin Immunol

Trends Immunol

Bioorg Med Chem

Cell

Immunity

Toll-like receptor downstream signalling

Arthritis Res Ther

Negative regulation of Toll-like receptor-mediated immune responses

Nat Rev Immunol

Sequence-specific potent induction of IFN-α by short interfering RNA in plasmacytoid dendritic cells through TLR7

Nat Med

Immunomodulatory oligonucleotides containing a cytosine-phosphate-2′-deoxy-7-deazaguanosine motif as potent toll-like receptor 9 agonists

Proc Natl Acad Sci U S A

CpG RNA: identification of novel single-stranded RNA that stimulates human CD14+CD11c+ monocytes

J Immunol

Basic and clinical immunology
Redirection of allergen-specific T_H2 responses by a modified adenine through Toll-like receptor 7 interaction and IL-12/IFN release