title: Persistence of antibodies to West Nile virus nonstructural protein 5.
abstract: BACKGROUND
  Because IgM antibody against West Nile virus (WNV) pre-membrane/envelope (preM/E) recombinant protein may persist for more than 1 year, an assay distinguishing recent from past WNV infection would be useful. Published findings for a single patient suggest that the presence of antibody against WNV nonstructural protein 5 (NS5) indicates recent infection.
  
  
  OBJECTIVE
  To compare the persistence of WNV NS5 antibodies and preM/E IgM using plasma samples from blood donors who were viremic at the time of donation.
  
  
  METHODS
  Follow-up plasma samples from 35 viremic donors were tested for WNV NS5 antibodies using a microsphere immunoassay, and compared to WNV preM/E IgM antibodies determined on the same samples using an enzyme-linked immunosorbent assay (ELISA).
  
  
  RESULTS
  At 90+/-14 days of follow-up, 20/26 donors (77%) were positive for NS5 antibodies; 6/25 (24%) were positive at 180+/-27 days, and 3/23 (13%) were positive at 365+/-55 days. The comparable values for preM/E IgM antibodies were 77%, 32% and 17%, respectively.
  
  
  CONCLUSIONS
  Persistence of WNV NS5 antibody in plasma is similar to that of preM/E IgM antibody. WNV NS5 antibody cannot be used to distinguish recent from past WNV infection.
authors.affiliation: Focus Diagnostics, 5785 Corporate Avenue, Cypress, CA 90630, USA. hprince@focusdx.com
authors.forename: Harry E
authors.initials: HE
authors.lastname: Prince
authors.forename: Mary
authors.initials: M
authors.lastname: Lapé-Nixon
authors.forename: Cindy
authors.initials: C
authors.lastname: Yeh
authors.forename: Leslie H
authors.initials: LH
authors.lastname: Tobler
authors.forename: Michael P
authors.initials: MP
authors.lastname: Busch
mesh_terms: D000914:Antibodies, Viral / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood; D008863:Microspheres; D013997:Time Factors; D014759:Viral Envelope Proteins / Q000276:immunology; D017361:Viral Nonstructural Proteins / Q000276:immunology*; D014901:West Nile Fever / Q000276:immunology*; D014902:West Nile virus / Q000276:immunology*
chemical_list: D000914:Antibodies, Viral; D007075:Immunoglobulin M; C096041:NS5 protein, flavivirus; D014759:Viral Envelope Proteins; D017361:Viral Nonstructural Proteins; C074932:prM protein, Flavivirus