title: Detection of NP, N3 and N7 antibodies to avian influenza virus by indirect ELISA using yeast-expressed antigens.
abstract: BACKGROUND
  Avian influenza viruses, belonging to the family Orthomyxoviridae, possess distinct combinations of hemagglutinin (H) and the neuraminidase (N) surface glycoproteins. Typing of both H and N antigens is essential for the epidemiological and surveillance studies. Therefore, it is important to find a rapid, sensitive, and specific method for their assay, and ELISA can be useful for this purpose, by using recombinant proteins.
  
  
  RESULTS
  The nucleoprotein (NP) and truncated neuraminidase subtype 3 and 7 of avian influenza virus (AIV) were expressed in Saccharomyces cerevisiae and used to develop an indirect enzyme-linked immunosorbent assay for antibody detection. The developed assays were evaluated with a panel of 64 chicken serum samples. The performance of NP-ELISA was compared with the commercially available ProFlok AIV ELISA kit. The results showed comparable agreement and sensitivity between the two tests, indicating that NP-ELISA assay can be used for screening the influenza type A antibody in AIV infected birds. The N3 and N7- ELISAs also reacted specifically to their type specific sera and did not exhibit any cross-reaction with heterologous neuraminidase subtype specific sera.
  
  
  CONCLUSIONS
  The study demonstrates the expression of the NP, N3, and N7 proteins of AIV in yeast (S. cerevisiae) and their application in developing an indirect ELISA for detecting NP, N3 and N7 antibodies from AIV-infected chicken sera. The described indirect ELISAs are rapid, sensitive, specific and can be used as promising tests during serological surveillance.
authors.affiliation: Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, Maryland 21202-3101, USA. upadhyay@umbi.umd.edu
authors.forename: Chitra
authors.initials: C
authors.lastname: Upadhyay
authors.forename: Arun
authors.initials: A
authors.lastname: Ammayappan
authors.forename: Vikram N
authors.initials: VN
authors.lastname: Vakharia
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D000956:Antigens, Viral / Q000276:immunology*; D002645:Chickens; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005585:Influenza in Birds / Q000175:diagnosis* / Q000821:virology; D009439:Neuraminidase / Q000276:immunology*; D019590:Nucleocapsid Proteins; D011201:Poultry Diseases / Q000175:diagnosis / Q000821:virology; D016601:RNA-Binding Proteins / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology; D012441:Saccharomyces cerevisiae / Q000235:genetics; D012680:Sensitivity and Specificity; D014758:Viral Core Proteins / Q000276:immunology*; D014764:Viral Proteins / Q000276:immunology*
chemical_list: D000914:Antibodies, Viral; D000956:Antigens, Viral; C048842:NP protein, Influenza A virus; D019590:Nucleocapsid Proteins; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D014758:Viral Core Proteins; D014764:Viral Proteins; C487630:NA protein, influenza A virus; D009439:Neuraminidase