title: Maternal and fetal predictors of fetal viral load and death in third trimester, type 2 porcine reproductive and respiratory syndrome virus infected pregnant gilts.
abstract: Minimal research has focused on understanding mechanisms underlying porcine reproductive and respiratory syndrome virus (PRRSV) induced reproductive failure. We have completed a large-scale project investigating phenotypic and genotypic predictors of reproductive PRRS severity in which numerous clinical, pathological, immunologic and viral responses were characterized in dams and fetuses. The goal was to determine which phenotypic responses were associated with fetal viral load and death after experimental infection of pregnant gilts with type 2 PRRSV, thereby elucidating mechanisms of reproductive PRRS in third trimester pregnant gilts. The presence of fetal infection and increasing RNA concentration at the maternal-fetal interface were strong predictors of the probability of fetal death, while PRRSV RNA concentration in dam sera and systemic tissues were not associated with the odds of fetal death. Fetal infection and death clustered, indicating that the status of adjacent fetuses is crucial for lateral transmission and fetal outcome. Several systemic immune responses of gilts were associated with fetal outcome and viral load: interferon-α contributed to the probability of fetal death, but absolute numbers of T helper cells in early infection, absolute numbers of myeloid cells over time and interleukin 12 levels appeared protective. These results suggest specific immune responses may either contribute to, or protect against, transplacental virus transmission. The WUR10000125 SNP on chromosome 4, associated with PRRS resilience in nursery pigs, was not associated with reproductive outcome. Whereas past research suggested that fetal death results from events occurring at the maternal-fetal interface, we conclude that viral replication within fetuses and spread of PRRSV to adjacent fetuses are pivotal events in the pathogenesis of reproductive PRRS.
authors.affiliation: Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK, S7N5B4, Canada. andrea.ladinig@vetmeduni.ac.at.|University Clinic for Swine, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210, Vienna, Austria. andrea.ladinig@vetmeduni.ac.at.
authors.forename: Andrea
authors.initials: A
authors.lastname: Ladinig
authors.affiliation: Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK, S7N5B4, Canada. carolyn.ashley@usask.ca.
authors.forename: Carolyn
authors.initials: C
authors.lastname: Ashley
authors.affiliation: Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK, S7N5B4, Canada. susan.detmer@usask.ca.
authors.forename: Susan E
authors.initials: SE
authors.lastname: Detmer
authors.affiliation: Department of Agricultural, Food, and Nutritional Science, Faculty of Agricultural, Life and Environmental Sciences, University of Alberta, 410 Agriculture/Forestry Centre, Edmonton, AB, T6G2P5, Canada. james.wilkinson@ales.ualberta.ca.
authors.forename: Jamie M
authors.initials: JM
authors.lastname: Wilkinson
authors.affiliation: Animal Parasitic Diseases Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, 10300 Baltimore Blvd., Building 003, Beltsville, MD, 20705, USA. Joan.Lunney@ars.usda.gov.
authors.forename: Joan K
authors.initials: JK
authors.lastname: Lunney
authors.affiliation: Department of Agricultural, Food, and Nutritional Science, Faculty of Agricultural, Life and Environmental Sciences, University of Alberta, 410 Agriculture/Forestry Centre, Edmonton, AB, T6G2P5, Canada. graham.plastow@ales.ualberta.ca.
authors.forename: Graham
authors.initials: G
authors.lastname: Plastow
authors.affiliation: Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK, S7N5B4, Canada. john.harding@usask.ca.
authors.forename: John C S
authors.initials: JC
authors.lastname: Harding
mesh_terms: D000818:Animals; D005260:Female; D005333:Fetus / Q000821:virology; D019318:Porcine Reproductive and Respiratory Syndrome / Q000821:virology*; D019316:Porcine respiratory and reproductive syndrome virus / Q000502:physiology*; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000662:veterinary* / Q000821:virology; D012367:RNA, Viral / Q000032:analysis; D013552:Swine; D013950:Thymus Gland / Q000821:virology*; D019562:Viral Load / Q000662:veterinary*
chemical_list: D012367:RNA, Viral