title: Strain specificity of the immune response of pigs following vaccination with various strains of porcine reproductive and respiratory syndrome virus.
abstract: The primary objective of the study was to determine strain specificity of the immune response of pigs following vaccination with selected strains of porcine reproductive and respiratory syndrome virus (PRRSV). The experimental design included five groups (I through V, six pigs per group) free of antibody for PRRSV at the beginning of the experiment (day 0). On day 0, groups III, IV, and V were vaccinated with attenuated versions of PRRSV strains 8, 9, and 14, respectively. On day 21, the immunity of group II (non-vaccinated/challenged controls) and groups III, IV, and V was challenged by exposing each pig to a composite of the virulent versions of these same three strains. On day 35, all pigs, including non-vaccinated/non-challenged pigs of group I, were necropsied. Lungs and selected lymph nodes were examined for lesions. Serum samples obtained at weekly intervals throughout the study and lung lavage fluids obtained at necropsy were tested for the presence of PRRSV and its strain identity. Before challenge the strain of PRRSV identified in the sera of vaccinated pigs was always that with which the particular pig had been vaccinated (i.e. homologous strain), whereas, with one exception, only heterologous strains were identified after challenge. This apparent strain exclusion as a result of vaccination was statistically significant (P = 0.004). The tendency for heterologous strains to predominate after challenge suggests that a pig's immune response to PRRSV has some degree of strain specificity. Whether this finding has any clinical relevance in regard to immunoprophylaxis remains to be determined.
authors.affiliation: Virus and Prion Diseases of Livestock Research Unit, National Animal Disease Center, USDA, Agricultural Research Service, PO Box 70, Ames, IA 50010, USA. bbmengeling@aol.com
authors.forename: William L
authors.initials: WL
authors.lastname: Mengeling
authors.forename: Kelly M
authors.initials: KM
authors.lastname: Lager
authors.forename: Ann C
authors.initials: AC
authors.lastname: Vorwald
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Koehler
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D001835:Body Weight; D001992:Bronchoalveolar Lavage Fluid / Q000821:virology; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect / Q000662:veterinary; D008168:Lung / Q000473:pathology / Q000821:virology; D008198:Lymph Nodes / Q000473:pathology / Q000821:virology; D016133:Polymerase Chain Reaction / Q000662:veterinary; D012150:Polymorphism, Restriction Fragment Length; D019318:Porcine Reproductive and Respiratory Syndrome / Q000097:blood / Q000276:immunology / Q000517:prevention & control / Q000821:virology*; D019316:Porcine respiratory and reproductive syndrome virus / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity; D013045:Species Specificity; D013047:Specific Pathogen-Free Organisms; D013552:Swine / Q000276:immunology*; D014611:Vaccination / Q000379:methods / Q000662:veterinary*; D014613:Vaccines, Attenuated / Q000276:immunology / Q000592:standards; D014765:Viral Vaccines / Q000276:immunology*; D014774:Virulence
chemical_list: D000914:Antibodies, Viral; D004279:DNA, Viral; D014613:Vaccines, Attenuated; D014765:Viral Vaccines