title: Genome-wide analysis of the transcriptional response to porcine reproductive and respiratory syndrome virus infection at the maternal/fetal interface and in the fetus.
abstract: Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) infection of pregnant pigs can result in congenital infection and ultimately fetal death. Little is known about immune responses to infection at the maternal-fetal interface and in the fetus itself, or the molecular events behind virus transmission and disease progression in the fetus. To investigate these processes, RNA-sequencing of two sites, uterine endothelium with adherent placental tissue and fetal thymus, was performed 21 days post-challenge on four groups of fetuses selected from a large PRRSV challenge experiment of pregnant gilts: control (CON), uninfected (UNINF), infected (INF), and meconium-stained (MEC) (n = 12/group). Transcriptional analyses consisted of multiple contrasts between groups using two approaches: differential gene expression analysis and weighted gene co-expression network analysis (WGCNA). Biological functions, pathways, and regulators enriched for differentially expressed genes or module members were identified through functional annotation analyses. Expression data were validated by reverse transcription quantitative polymerase chain reaction (RTqPCR) carried out for 16 genes of interest.
  
  
  
  The immune response to infection in endometrium was mainly adaptive in nature, with the most upregulated genes functioning in either humoral or cell-mediated immunity. In contrast, the expression profile of infected fetal thymus revealed a predominantly innate immune response to infection, featuring the upregulation of genes regulated by type I interferon and pro-inflammatory cytokines. Fetal infection was associated with an increase in viral load coupled with a reduction in T cell signaling in the endometrium that could be due to PRRSV-controlled apoptosis of uninfected bystander cells. There was also evidence for a reduction in TWIST1 activity, a transcription factor involved in placental implantation and maturation, which could facilitate virus transmission or fetal pathology through dysregulation of placental function. Finally, results suggested that events within the fetus could also drive fetal pathology. Thymus samples of meconium-stained fetuses exhibited an increase in the expression of pro-inflammatory cytokine and granulocyte genes previously implicated in swine infectious disease pathology.
  
  
  
  This study identified major differences in the response to PRRSV infection in the uterine endometrium and fetus at the gene expression level, and provides insight into the molecular basis of virus transmission and disease progression.
authors.affiliation: Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, AB, Canada. jamiewilkinson@hotmail.com.
authors.forename: Jamie M
authors.initials: JM
authors.lastname: Wilkinson
authors.affiliation: Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, AB, Canada.
authors.forename: Hua
authors.initials: H
authors.lastname: Bao
authors.affiliation: Department for Farm Animals and Veterinary Public Health, University Clinic for Swine, University of Veterinary Medicine, Vienna, Austria.|Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada.
authors.forename: Andrea
authors.initials: A
authors.lastname: Ladinig
authors.affiliation: Animal Parasitic Diseases Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD, USA.|Key Lab of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China.
authors.forename: Linjun
authors.initials: L
authors.lastname: Hong
authors.affiliation: Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, AB, Canada.
authors.forename: Paul
authors.initials: P
authors.lastname: Stothard
authors.affiliation: Animal Parasitic Diseases Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD, USA.
authors.forename: Joan K
authors.initials: JK
authors.lastname: Lunney
authors.affiliation: Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, AB, Canada.
authors.forename: Graham S
authors.initials: GS
authors.lastname: Plastow
authors.affiliation: Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada.
authors.forename: John C S
authors.initials: JC
authors.lastname: Harding
mesh_terms: D000818:Animals; D016000:Cluster Analysis; D004717:Endometrium / Q000378:metabolism; D005260:Female; D005333:Fetus / Q000378:metabolism*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D055106:Genome-Wide Association Study; D054884:Host-Pathogen Interactions / Q000235:genetics*; D009928:Organ Specificity / Q000235:genetics; D010920:Placenta / Q000378:metabolism*; D019318:Porcine Reproductive and Respiratory Syndrome / Q000235:genetics* / Q000821:virology*; D019316:Porcine respiratory and reproductive syndrome virus; D011247:Pregnancy; D015203:Reproducibility of Results; D015398:Signal Transduction; D013552:Swine; D059467:Transcriptome; D019562:Viral Load
keywords: Fetus; Gene; PRRSV; Pig; RNA-sequencing; Transcriptome