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

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.

TLR2/MyD88/NF-κB signalling pathway regulates IL-8 production in porcine alveolar macrophages infected with porcine circovirus 2

“…IL-8, a major neutrophil chemotactic factor, is an important participant in the migration of specific inflammatory cells from the peripheral blood to the inflammatory site during an innate immune response (Kunkel et al, 1991). In this study, we found that PCV2 activated IL-8 expression in PAMs, which is consistent with previous reports that IL-8 is upregulated both in vivo (Chae & Choi, 2011;Darwich et al, 2003a, b) and in vitro Mavrommatis et al, 2014). Expression levels of IL-8 vary with PCV2 infection status and rely on the efficiency of the innate immune response (Borghetti et al, 2013).…”

“…Previous studies have reported that PCV2 infection induces porcine IL-8 expression both in vivo and in vitro (Chae & Choi, 2011;Darwich et al, 2003;Li et al, 2013;Mavrommatis et al, 2014). To confirm these findings, IL-8 secretion from PCV2-infected PAMs was measured at the protein level by ELISA.…”

“…Interstitial pneumonia is frequently observed in pigs suffering from naturally acquired PMWS or experimental PCV2 infection (Chae & Choi, 2011;Darwich et al, 2003a). It has been reported that PCV2 infection triggers IL-8, IL-1b and TNF-a expression in porcine alveolar macrophages (PAMs), monocyte-derived dendritic cells, and PBMCs (Darwich et al, 2003b;Li et al, 2013;Mavrommatis et al, 2014). Moreover, upregulated mRNA expression of IL-1a and IL-8 was found in an in vivo model of PCV2-associated respiratory disease (Chae & Choi, 2011).…”

Interactions of porcine circovirus 2 with its hosts

“…During PCV2 infection, the expression levels of cellular genes are extensively modulated, and the resulting differentially expressed proteins are involved in the cytoskeleton, stress response, macromolecular biosynthesis, energy metabolism, ubiquitin-proteasome pathway, signal transduction, gene regulation, and immune response [38][39][40][41][42][43][44][45]. The virus-host interactions related to PCV2 proliferation are shown in Fig.…”

Overexpression of Programmed Death Ligands in Naturally Occurring Postweaning Multisystemic Wasting Syndrome

“…The targets of PCV2 replication are mainly monocyte/macrophage and antigen-presenting cells (APCs), with several studies demonstrating the importance of the immune system in the pathogenesis of PMWS. For example, PMWS-affected pigs exhibit B-and T-cell depletion; diminishment of CD8 + , CD4 + CD8 + , and IgM + lymphocyte subsets; overexpression of IL-10 and IFN-c mRNA in the thymus and tonsils respectively; and decreased expression of IL-2 and IL-12p40 mRNA in the spleen (7,16,20,21,23). In addition, pigs affected by PMWS are more susceptible to secondary infection by bacteria (15).…”