title: Open reading frame 8a of the human severe acute respiratory syndrome coronavirus not only promotes viral replication but also induces apoptosis.
abstract: BACKGROUND
  A unique genomic difference between human and civet severe acute respiratory syndrome coronaviruses (SARS-CoVs) is that the former has a deletion of 29 nucleotides from open reading frame (orf) 8a' that results in the generation of orf8a and orf8b. The objectives of the present study were to analyze antibody reactivity to ORF8a in patients with SARS and to elucidate the function of ORF8a.
  
  
  METHODS
  Western-blot and immunofluorescent antibody assays were used to detect anti-ORF8a antibody. SARS-CoV HKU39849 was used to infect stable clones expressing ORF8a and cells transfected with small interfering RNA (siRNA). The virus loads (VLs) and cytopathic effects (CPEs) were recorded. Confocal microscopy and several mitochondria-related tests were used to study the function of ORF8a.
  
  
  RESULTS
  Two (5.4%) of 37 patients with SARS had anti-ORF8a antibodies. The VLs in the stable clones expressing ORF8a were significantly higher than those in control subjects 5 days after infection. siRNA against orf8a significantly reduced VLs and interrupted the CPE. ORF8a was found to be localized in mitochondria, and overexpression resulted in increases in mitochondrial transmembrane potential, reactive oxygen species production, caspase 3 activity, and cellular apoptosis.
  
  
  CONCLUSIONS
  ORF8a not only enhances viral replication but also induces apoptosis through a mitochondria-dependent pathway.
authors.affiliation: Institute of Public Health, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Chia-Yen
authors.initials: CY
authors.lastname: Chen
authors.forename: Yueh-Hsin
authors.initials: YH
authors.lastname: Ping
authors.forename: Hsin-Chen
authors.initials: HC
authors.lastname: Lee
authors.forename: Kuan-Hsuan
authors.initials: KH
authors.lastname: Chen
authors.forename: Yuan-Ming
authors.initials: YM
authors.lastname: Lee
authors.forename: Yu-Juin
authors.initials: YJ
authors.lastname: Chan
authors.forename: Te-Cheng
authors.initials: TC
authors.lastname: Lien
authors.forename: Tjin-Shing
authors.initials: TS
authors.lastname: Jap
authors.forename: Chi-Hung
authors.initials: CH
authors.lastname: Lin
authors.forename: Lung-Sen
authors.initials: LS
authors.lastname: Kao
authors.forename: Yi-Ming Arthur
authors.initials: YM
authors.lastname: Chen
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D002522:Chlorocebus aethiops; D006801:Humans; D016366:Open Reading Frames; D010101:Oxygen Consumption / Q000502:physiology; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species / Q000378:metabolism; D045473:Severe acute respiratory syndrome-related coronavirus / Q000235:genetics*; D045169:Severe Acute Respiratory Syndrome / Q000821:virology; D013997:Time Factors; D014779:Virus Replication / Q000502:physiology*
chemical_list: D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D053148:Caspase 3