High-Resolution Profiling of Innate Immune Responses by Porcine Dendritic Cell Subsets in vitro and in vivo.

Gaël Auray,Irene Keller,Artur Summerfield,Sylvie Python,Matthias Liniger,Llilianne Ganges,Stephanie C Talker,Rémy Bruggmann,Markus Gerber,Nicolas Ruggli

doi:10.3389/fimmu.2020.01429

Abstract

The present study investigated the transcriptomic response of porcine dendritic cells (DC) to innate stimulation in vitro and in vivo. The aim was to identify DC subset-specialization, suitable Toll-like receptor (TLR) ligands targeting plasmacytoid DC (pDC), and the DC activation profile during highly and low virulent classical swine fever virus (CSFV, strain Eystrup and Pinar del Rio, respectively) infection, chosen as model for a virus causing a severe immunopathology. After identification of porcine conventional DC (cDC) 1, cDC2, pDC and a monocyte-derived subset in lymphoid tissues, we characterized DC activation using transcriptomics, and focused on chemokines, interferons, cytokines, as well as on co-stimulatory and inhibitory molecules. We demonstrate that porcine pDC provide important signals for Th1 and interferon responses, with CpG triggering the strongest responses in pDC. DC isolated early after infection of pigs with either of the two CSFV strains showed prominent upregulation of CCL5, CXCL9, CXCL10, CXCL11, and XCL1, as well as of the cytokines TNFSF13B, IL6, IL7, IL12B, IL15, IL27. Transcription of IL12B and many interferon genes were mostly restricted to pDC. Interestingly, the infection was associated with a prominent induction of inhibitory and cell death receptors. When comparing low and highly virulent CSFV strains, the latter induced a stronger inflammatory and antiviral response but a weaker cell cycle response, and reduced antigen presentation functions of DC. Taken together, we provide high-resolution information on DC activation in pigs, as well as information on how DC modulation could be linked to CSFV immunopathology.

Highlights

Dendritic cells (DC) are sentinel innate immune cells that are present in the skin and at mucosal surfaces and are specialized in the early sensing of pathogens
Due to limitations in cell numbers of the rare cDC1 subset following sorting, we focused on the stimulation of the different populations with the TLR1/TLR2 agonist PAM3Cys which was selected based on its ability to directly activate all four targeted subsets [3]
We compared the response of dendritic cells (DC) subsets and monocytes to the TLR1/2 ligand PAM3Cys which is able to activate both porcine DC and monocytes [3]

Summary

Introduction

Dendritic cells (DC) are sentinel innate immune cells that are present in the skin and at mucosal surfaces and are specialized in the early sensing of pathogens. DC can be divided into functionally specialized subsets, including two conventional DC subsets (cDC1 and cDC2) and plasmacytoid (p)DC These subsets differ in their ability to induce particular T-cell responses and in their expression of pattern recognition receptors (PRRs) which sense danger signals such as pathogen- and damage-associated molecular patterns [1]. Triggering of these receptors leads to activation and maturation of DC, which is associated with a shift in their expression of chemokine receptors from CCR2 and/or CCR5 to CCR7, allowing them to migrate toward lymph nodes (LN) [2]. Depending on the stimuli and the immunological environment, signals from activated DC shape the adaptive immune response toward Th1, Th2, or Th17 responses

Objectives

Methods

Results

Conclusion