Transcription analysis of the porcine alveolar macrophage response to porcine circovirus type 2

Abstract

BackgroundPorcine circovirus type 2 (PCV2) is the causal agent of postweaning multisystemic wasting syndrome (PMWS), which has severely impacted the swine industry worldwide. PCV2 triggers a weak and atypical innate immune response, but the key genes and mechanisms by which the virus interferes with host innate immunity have not yet been elucidated. In this study, genes that control the response of primary porcine alveolar macrophages (PAMs), the main target of PCV2, were profiled in vitro.ResultsPAMs were successfully infected by PCV2-WH strain, as evidenced quantitative real-time polymerase chain reaction (qPCR) and immunofluorescence assay (IFA) results. Infection-related differential gene expression was investigated using pig microarrays from the US Pig Genome Coordination Program and validated by real-time PCR and enzyme-linked immunosorbent assay (ELISA). Microarray analysis at 24 and 48 hours post-infection (HPI) revealed 266 and 175 unique genes, respectively, that were differentially expressed (false discovery rate <0.05; fold-change >2). Only six genes were differentially expressed between 24 and 48 HPI. The up-regulated genes were principally related to immune response, cytokine activity, locomotion, regulation of cell proliferation, apoptosis, cell growth arrest, and antigen procession and presentation. The down-regulated genes were mainly involved in terpenoid biosynthesis, carbohydrate metabolism, translation, proteasome degradation, signal transducer activity, and ribosomal proteins, which were representative of the reduced vital activity of PCV2-infected cells.ConclusionsPCV2 infection of PAMs causes up-regulation of genes related to inflammation, indicating that PCV2 may induce systematic inflammation. PCV2 persistently induced cytokines, mainly through the Toll-like receptor (TLR) 1 and TLR9 pathways, which may promote high levels of cytokine secretion. PCV2 may prevent apoptosis in PAMs by up-regulating SERPINB9 expression, possibly to lengthen the duration of PCV2 replication-permissive conditions. The observed gene expression profile may provide insights into the underlying immunological response and pathological changes that occur in pigs following PCV2 infection.

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

“…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.…”

“…Additionally, infection with this virus increases cellular autophagy to enhance PCV2 proliferation in cells. The arrows indicate activation, whereas T lines indicate inhibition Virus Genes and TLR9 pathways [40]. Interleukin (IL)-2 can induce cell proliferation and PCV2 replication in peripheral blood lymphocytes [99].…”

“…In porcine alveolar macrophages (PAMs), SERPINB9 expression is up-regulated during PCV2 infection to prevent apoptosis [40].…”