Global Gene Expression Profiling of Myeloid Immune Cell Subsets in Response to In Vitro Challenge with Porcine Circovirus 2b

Bettina Mavrommatis,Victoria Offord,Theo Kanellos,Robert Patterson,Mick Watson,Dirk Werling,Falko Steinbach,Sylvia Grierson,Lars Kaderali

doi:10.1371/journal.pone.0091081

Abstract

Compelling evidence suggests that the early interaction between porcine circovirus 2 (PCV-2) and the innate immune system is the key event in the pathogenesis of Post-Weaning Multisystemic Wasting Syndrome (PMWS). Furthermore, PCV2 has been detected in bone-marrow samples, potentially enabling an easy spread and reservoir for the virus. To assess the gene-expression differences induced by an in-vitro PCV2b infection in different three different myeloid innate immune cell subsets generated from the same animal, we used the Agilent Porcine Gene Expression Microarray (V2). Alveolar macrophages (AMØs), monocyte-derived dendritic cells (MoDCs) and bone-marrow cells (BMCs) were generated from each animal, and challenged with a UK-isolate of a PCV2 genotype b-strain at a MOI of 0.5. Remarkably, analysis showed a highly distinct and cell-type dependent response to PCV2b challenge. Overall, MoDCs showed the most marked response to PCV2b challenge in vitro and revealed a key role for TNF in the interaction with PCV2b, whereas only few genes were affected in BMCs and AMØs. These observations were further supported by an enrichment of genes in the downstream NF-κB Signalling pathway as well as an up regulation of genes with pro-apoptotic functions post-challenge. PCV2b challenge increases the expression of a large number of immune-related and pro-apoptotic genes mainly in MoDC, which possibly explain the increased inflammation, granulomatous inflammation and lymphocyte depletion seen in PMWS-affected pigs.

Highlights

PCV2, a non-enveloped, single-stranded circular DNA virus, has been recognized as the underlying agent for Post Weaning Multisystemic Wasting Syndrome (PMWS) [1,2] and is endemic in most pig-producing countries
Quantitative PCR revealed the presence of increasing copynumbers of PCV2b in all three cell-types, with the highest copy number being detected in alveolar macrophages (Fig. 1a)
Differences in cell-specific gene expression of PCV2b challenged and unchallenged immune cell subsets derived from individual animals (MoDCs, AMØs and bone-marrow cells (BMCs)) were assessed using the Agilent Porcine Gene Expression Microarray with a cutoff p-value of p,0.05 and a fold range of 21.5#fold change (FC)$1.5

Summary

Introduction

PCV2, a non-enveloped, single-stranded circular DNA virus, has been recognized as the underlying agent for Post Weaning Multisystemic Wasting Syndrome (PMWS) [1,2] and is endemic in most pig-producing countries. Previous studies did not show differences in virulence of different PCV2 strains [1,6]; recent evidence suggests that mutations in circulating PCV2 strains coincided with a dramatic change of pathogenicity and clinical outcome [3,7], with pigs carrying numerous PCV2 genotypes [8]. The fact that PCV2 has been detected in both PMWS and non-PMWS affected farms and pigs contributed to the notion that different PCV2 strains vary in their pathogenicity [9]. In that context it has to be noted that the dominant PCV2 strain circulating on severely-affected farms in the UK was grouped into genotype PCV2b, as determined in a recent cross-sectional study involving 147 pig farms across England [10]

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