title: Lung pathogenicity of European genotype 3 strain porcine reproductive and respiratory syndrome virus (PRRSV) differs from that of subtype 1 strains.
abstract: Porcine reproductive and respiratory syndrome (PRRS) is difficult to control due to a high mutation rate of the PRRS virus (PRRSV) and the emergence of virulent strains. The objective of this study was to analyse early and late pathological responses in the respiratory tract after infection with the European PRRSV subtype 3 strain Lena in comparison to two European PRRSV subtype 1 strains: Belgium A and Lelystad-Ter Huurne (LV). For each virus strain, groups of twelve pigs were inoculated, and four pigs per group were euthanized at days 3, 7 and 35 post-infection (p.i.) for consecutive examination. Infection with strain Lena resulted in a more severe disease than with the subtype 1 strains, an inflammatory response within the first week of infection with expression of IL-1α in the lung and lymph node, and an influx of neutrophils and monocytes in bronchoalveolar lavage fluid (BALF). Infection with strain Belgium A or LV resulted in mild or no pathology within the first week of infection, but inflammatory cell influx in the lung interstititium was increased at the end of the experiment at day 35 p.i. At five weeks p.i., all strains induced a higher percentage of cytotoxic T cells and higher levels of IFN-γ producing cells in BALF. This might have contributed to clearance of virus. In general, subtype 3 strain Lena induced a stronger early inflammatory response which led to more severe clinical disease and pathology. On the other hand, this may have supported an enhanced or faster clearance of virus in tissues, compared to subtype 1 strains.
authors.affiliation: Department of Infection Biology, Central Veterinary Institute, Part of Wageningen UR, PO Box 65, 8200 AB Lelystad, The Netherlands. Electronic address: eefke.weesendorp@wur.nl.
authors.forename: Eefke
authors.initials: E
authors.lastname: Weesendorp
authors.affiliation: Department of Infection Biology, Central Veterinary Institute, Part of Wageningen UR, PO Box 65, 8200 AB Lelystad, The Netherlands.
authors.forename: Johanna M J
authors.initials: JM
authors.lastname: Rebel
authors.affiliation: Department of Infection Biology, Central Veterinary Institute, Part of Wageningen UR, PO Box 65, 8200 AB Lelystad, The Netherlands.
authors.forename: Ditta J
authors.initials: DJ
authors.lastname: Popma-De Graaf
authors.affiliation: Department of Infection Biology, Central Veterinary Institute, Part of Wageningen UR, PO Box 65, 8200 AB Lelystad, The Netherlands.
authors.forename: Helmi P D
authors.initials: HP
authors.lastname: Fijten
authors.affiliation: Department of Infection Biology, Central Veterinary Institute, Part of Wageningen UR, PO Box 65, 8200 AB Lelystad, The Netherlands.
authors.forename: Norbert
authors.initials: N
authors.lastname: Stockhofe-Zurwieden
mesh_terms: D000818:Animals; D001530:Belgium; D001831:Body Temperature; D001992:Bronchoalveolar Lavage Fluid / Q000821:virology; D005434:Flow Cytometry / Q000662:veterinary; D005838:Genotype; D007150:Immunohistochemistry / Q000662:veterinary; D016130:Immunophenotyping / Q000662:veterinary; D007249:Inflammation / Q000473:pathology*; D008168:Lung / Q000473:pathology / Q000821:virology*; D009000:Monocytes / Q000276:immunology; D019318:Porcine Reproductive and Respiratory Syndrome / Q000276:immunology* / Q000473:pathology*; D019316:Porcine respiratory and reproductive syndrome virus / Q000235:genetics / Q000472:pathogenicity*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D013045:Species Specificity; D018709:Statistics, Nonparametric; D013552:Swine; D014766:Viremia / Q000662:veterinary; D014774:Virulence
keywords: Genetic subtypes; Immune response; Pathogenesis; Porcine reproductive and respiratory syndrome virus