title: Increased pathogenicity of European porcine reproductive and respiratory syndrome virus is associated with enhanced adaptive responses and viral clearance.
abstract: Porcine reproductive and respiratory syndrome (PRRS) is one of the most economically important diseases of swine worldwide. Since its first emergence in 1987 the PRRS virus (PRRSV) has become particularly divergent with highly pathogenic strains appearing in both Europe and Asia. However, the underlying mechanisms of PRRSV pathogenesis are still unclear. This study sets out to determine the differences in pathogenesis between subtype 1 and 3 strains of European PRRSV (PRRSV-I), and compare the immune responses mounted against these strains. Piglets were infected with 3 strains of PRRSV-I: Lelystad virus, 215-06 a British field strain and SU1-bel from Belarus. Post-mortem examinations were performed at 3 and 7 days post-infection (dpi), and half of the remaining animals in each group were inoculated with an Aujeszky's disease (ADV) vaccine to investigate possible immune suppression resulting from PRRSV infection. The subtype 3 SU1-bel strain displayed greater clinical signs and lung gross pathology scores compared with the subtype 1 strains. This difference did not appear to be caused by higher virus replication, as viraemia and viral load in broncho-alveolar lavage fluid (BALF) were lower in the SU1-bel group. Infection with SU1-bel induced an enhanced adaptive immune response with greater interferon (IFN)-γ responses and an earlier PRRSV-specific antibody response. Infection with PRRSV did not affect the response to vaccination against ADV. Our results indicate that the increased clinical and pathological effect of the SU1-bel strain is more likely to be caused by an enhanced inflammatory immune response rather than higher levels of virus replication.
authors: Virology Department, Animal Health and Veterinary Laboratories Agency, Addlestone KT15 3NB, United Kingdom.
authors: S B
authors: SB
authors: Morgan
authors: S P
authors: SP
authors: Graham
authors: F J
authors: FJ
authors: Salguero
authors: P J
authors: PJ
authors: Sánchez Cordón
authors: H
authors: H
authors: Mokhtar
authors: J M J
authors: JM
authors: Rebel
authors: E
authors: E
authors: Weesendorp
authors: K B
authors: KB
authors: Bodman-Smith
authors: F
authors: F
authors: Steinbach
authors: J P
authors: JP
authors: Frossard
mesh_terms: D056704:Adaptive Immunity / Q000276:immunology*; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D001992:Bronchoalveolar Lavage Fluid / Q000821:virology; D007371:Interferon-gamma / Q000276:immunology; D008168:Lung / Q000473:pathology; D019318:Porcine Reproductive and Respiratory Syndrome / Q000276:immunology* / Q000473:pathology / Q000821:virology; D019316:Porcine respiratory and reproductive syndrome virus / Q000276:immunology / Q000472:pathogenicity*; D011994:Recombinant Proteins; D013552:Swine; D014765:Viral Vaccines / Q000276:immunology; D014779:Virus Replication
chemical_list: D000914:Antibodies, Viral; D011994:Recombinant Proteins; D014765:Viral Vaccines; D007371:Interferon-gamma