title: Distinction of subtype-specific antibodies against European porcine influenza viruses by indirect ELISA based on recombinant hemagglutinin protein fragment-1.
abstract: BACKGROUND
  Serological investigations of swine influenza virus infections and epidemiological conclusions thereof are challenging due to the complex and regionally variable pattern of co-circulating viral subtypes and lineages and varying vaccination regimes. Detection of subtype-specific antibodies currently depends on hemagglutination inhibition (HI) assays which are difficult to standardize and unsuitable for large scale investigations.
  
  
  METHODS
  The nucleocapsid protein (NP) and HA1 fragments of the hemagglutinin protein (HA) of five different lineages (H1N1av, H1N1pdm, H1pdmN2, H1N2, H3N2) of swine influenza viruses were bacterially expressed and used as diagnostic antigens in indirect ELISA.
  
  
  RESULTS
  Proteins were co-translationally mono-biotinylated and refolded in vitro into an antigenically authentic conformation. Western blotting and indirect ELISA revealed highly subtype-specific antigenic characteristics of the recombinant HA1 proteins although some cross reactivity especially among antigens of the H1 subtype were evident. Discrimination of antibodies directed against four swine influenza virus subtypes co-circulating in Germany was feasible using the indirect ELISA format.
  
  
  CONCLUSIONS
  Bacterially expressed recombinant NP and HA1 swine influenza virus proteins served as antigens in indirect ELISAs and provided an alternative to commercial blocking NP ELISA and HI assays concerning generic (NP-specific) and HA subtype-specific sero-diagnostics, respectively, on a herd basis.
authors.affiliation: Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Suedufer 10, Greifswald 17493, Germany.
authors.forename: Na
authors.initials: N
authors.lastname: Zhao
authors.forename: Elke
authors.initials: E
authors.lastname: Lange
authors.forename: Sybille
authors.initials: S
authors.lastname: Kubald
authors.forename: Christian
authors.initials: C
authors.lastname: Grund
authors.forename: Martin
authors.initials: M
authors.lastname: Beer
authors.forename: Timm C
authors.initials: TC
authors.lastname: Harder
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D000956:Antigens, Viral / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005858:Germany; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D009980:Influenza A virus / Q000145:classification* / Q000276:immunology / Q000302:isolation & purification; D019590:Nucleocapsid Proteins; D009976:Orthomyxoviridae Infections / Q000276:immunology / Q000662:veterinary* / Q000821:virology; D016601:RNA-Binding Proteins / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics; D013552:Swine; D013553:Swine Diseases / Q000276:immunology / Q000821:virology*; D014758:Viral Core Proteins / Q000235:genetics
chemical_list: D000914:Antibodies, Viral; D000956:Antigens, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus; C048842:NP protein, Influenza A virus; D019590:Nucleocapsid Proteins; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D014758:Viral Core Proteins
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