title: Inclusion bodies of recombinant Epstein-Barr virus capsid antigen p18 as potential immobilized antigens in enzyme immunoassays for detection of nasopharyngeal carcinoma.
abstract: BACKGROUND
  Development of indirect enzyme-linked immunosorbent assays (ELISAs) often utilizes synthetic peptides or recombinant proteins from Escherichia coli as immobilized antigens. Because inclusion bodies (IBs) formed during recombinant protein expression in E. coli are commonly thought as misfolded aggregates, only refolded proteins from IBs are used to develop new or in-house diagnostic assays. However, the promising utilities of IBs as nanomaterials and immobilized enzymes as shown in recent studies have led us to explore the potential use of IBs of recombinant Epstein-Barr virus viral capsid antigen p18 (VCA p18) as immobilized antigens in ELISAs for serologic detection of nasopharyngeal carcinoma (NPC).
  
  
  METHODS
  Thioredoxin fusion VCA p18 (VCA-Trx) and IBs of VCA p18 without fusion tags (VCA-IBs) were purified from E. coli. The diagnostic performances of IgG/VCA-IBs, IgG/VCA-Denat-IBs (using VCA-IBs coated in 8mol/l urea), IgG/VCA-Trx, and IgG/VCA-Peptide assays were compared by screening 100 NPC case-control pairs.
  
  
  RESULTS
  The IgG/VCA-Denat-IBs assay showed the best area under the receiver operating characteristic curve (AUC: 0.802; p<0.05), while the AUCs for the IgG/VCA-IBs, IgG/VCA-Trx, and IgG/VCA-Peptide assays were comparable (AUC: 0.740, 0.727, and 0.741, respectively).
  
  
  CONCLUSIONS
  We improved the diagnostic performance of the ELISA significantly using IBs of recombinant VCA p18.
authors.affiliation: Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Chun Shen
authors.initials: CS
authors.lastname: Lim
authors.affiliation: Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Siang Ling
authors.initials: SL
authors.lastname: Goh
authors.affiliation: Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Leena
authors.initials: L
authors.lastname: Kariapper
authors.affiliation: Department of Otorhinolaryngology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Gopala
authors.initials: G
authors.lastname: Krishnan
authors.affiliation: Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Yat-Yuen
authors.initials: YY
authors.lastname: Lim
authors.affiliation: Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia. Electronic address: ccng@um.edu.my.
authors.forename: Ching Ching
authors.initials: CC
authors.lastname: Ng
mesh_terms: D000956:Antigens, Viral / Q000737:chemistry / Q000276:immunology*; D036022:Capsid Proteins / Q000737:chemistry / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D055767:Immobilized Proteins / Q000737:chemistry / Q000276:immunology*; D007181:Inclusion Bodies, Viral / Q000737:chemistry / Q000276:immunology*; D009303:Nasopharyngeal Neoplasms / Q000175:diagnosis* / Q000276:immunology / Q000821:virology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000276:immunology
chemical_list: D000956:Antigens, Viral; D036022:Capsid Proteins; C041788:Epstein-Barr viral capsid antigen; D055767:Immobilized Proteins; D011994:Recombinant Proteins
keywords: BFRF3; Capsid protein VP26; EBV; ELISA; Inclusion body; NPC