Creation of an engineered APC system to explore and optimize the presentation of immunodominant peptides of major allergens.

Sandra Rosskopf,Barbara Bohle,Peter Steinberger,Winfried F Pickl,Alina Neunkirchner,Beatrice Jahn-Schmid,Martín R Candia,Sabrina Jutz

doi:10.1038/srep31580

Abstract

We have generated engineered APC to present immunodominant peptides derived from the major aero-allergens of birch and mugwort pollen, Bet v 1142–153 and Art v 125–36, respectively. Jurkat-based T cell reporter lines expressing the cognate allergen-specific T cell receptors were used to read out the presentation of allergenic peptides on the engineered APC. Different modalities of peptide loading and presentation on MHC class II molecules were compared. Upon exogenous loading with allergenic peptides, the engineered APC elicited a dose-dependent response in the reporter T cells and the presence of chemical loading enhancers strongly increased reporter activation. Invariant chain-based MHC class II targeting strategies of endogenously expressed peptides resulted in stronger activation of the reporters than exogenous loading. Moreover, we used Bet v 1 as model allergen to study the ability of K562 cells to present antigenic peptides derived from whole proteins either taken up or endogenously expressed as LAMP-1 fusion protein. In both cases the ability of these cells to process and present peptides derived from whole proteins critically depended on the expression of HLA-DM. We have identified strategies to achieve efficient presentation of allergenic peptides on engineered APC and demonstrate their use to stimulate T cells from allergic individuals.

Highlights

Accessory signals provided by antigen presenting cells (APC) govern the responses of T cells towards cognate peptide-major histocompatibility complex (MHC) molecules
Antibodies specific for the β-chain of the respective T cell receptors (TCRs) variable regions were used to select TCR-transgenic Jurkat reporter cell clones (Fig. 1b). These engineered antigen presenting cells (eAPC) and TCR-transgenic Jurkat-reporter T cells were cocultured for 24 hours in presence of immunodominant peptides and reporter induction was measured by flow cytometry
In this study we developed a stable system of engineered APC for efficient presentation of allergenic peptides to allergen-specific human CD4+ T cells

Summary

Introduction

Accessory signals provided by antigen presenting cells (APC) govern the responses of T cells towards cognate peptide-major histocompatibility complex (MHC) molecules. Initial studies have focused on the generation and use of MHC class I expressing K562 cells to stimulate CD8+ T cells specific for antigens derived from pathogens or tumors[2,3,4,5] More recently these cells have been shown to be suitable to present MHCII restricted antigens to CD4+ T cells. EAPC stably expressing MHCII molecules of choice are valuable for studying mechanisms and strategies for antigen processing and presentation to CD4+ T cells. They might be useful tools to expand and study allergen-specific T cells derived from allergic individuals. We have explored approaches to target endogenously expressed immunodominant peptides and full-length allergen proteins into the MHCII presentation pathway

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