Induction of indoleamine 2, 3-dioxygenase in human dendritic cells by a cholera toxin B subunit- Proinsulin vaccine

Jacques C. Mbongue, Dequina A. Nicholas, Kangling Zhang, Nan Sun Kim, Brittany N. Hamilton, Marco Larios, Guangyu Zhang, Kazuo Umezawa, Anthony F. Firek, William H R Langridge

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15 Scopus citations

Abstract

Dendritic cells (DC) interact with naïve T cells to regulate the delicate balance between immunity and tolerance required to maintain immunological homeostasis. In this study, immature human dendritic cells (iDC) were inoculated with a chimeric fusion protein vaccine containing the pancreatic β-cell auto-antigen proinsulin linked to a mucosal adjuvant the cholera toxin B subunit (CTB-INS). Proteomic analysis of vaccine inoculated DCs revealed strong up-regulation of the tryptophan catabolic enzyme indoleamine 2, 3-dioxygenase (IDO1). Increased biosynthesis of the immunosuppressive enzyme was detected in DCs inoculated with the CTB-INS fusion protein but not in DCs inoculated with proinsulin, CTB, or an unlinked combination of the two proteins. Immunoblot and PCR analyses of vaccine treated DCs detected IDO1mRNA by 3 hours and IDO1 protein synthesis by 6 hours after vaccine inoculation. Determination of IDO1 activity in vaccinated DCs by measurement of tryptophan degradation products (kynurenines) showed increased tryptophan cleavage into N-formyl kynurenine. Vaccination did not interfere with monocytes differentiation into DC, suggesting the vaccine can function safely in the human immune system. Treatment of vaccinated DCs with pharmacological NF-κB inhibitors ACHP or DHMEQ significantly inhibited IDO1 biosynthesis, suggesting a role for NF-κB signaling in vaccine up-regulation of dendritic cell IDO1. Heat map analysis of the proteomic data revealed an overall down-regulation of vaccinated DC functions, suggesting vaccine suppression of DC maturation. Together, our experimental data indicate that CTB-INS vaccine induction of IDO1 biosynthesis in human DCs may result in the inhibition of DC maturation generating a durable state of immunological tolerance. Understanding how CTB-INS modulates IDO1 activity in human DCs will facilitate vaccine efficacy and safety, moving this immunosuppressive strategy closer to clinical applications for prevention of type 1 diabetes autoimmunity.

Original languageEnglish (US)
Article numbere0118562
JournalPLoS One
Volume10
Issue number2
DOIs
StatePublished - Feb 25 2015

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ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

Mbongue, J. C., Nicholas, D. A., Zhang, K., Kim, N. S., Hamilton, B. N., Larios, M., Zhang, G., Umezawa, K., Firek, A. F., & Langridge, W. H. R. (2015). Induction of indoleamine 2, 3-dioxygenase in human dendritic cells by a cholera toxin B subunit- Proinsulin vaccine. PLoS One, 10(2), [e0118562]. https://doi.org/10.1371/journal.pone.0118562