title: Tropism and replication of Middle East respiratory syndrome coronavirus from dromedary camels in the human respiratory tract: an in-vitro and ex-vivo study.
abstract: BACKGROUND
  Middle East respiratory syndrome coronavirus (MERS-CoV) is a zoonotic infection causing severe viral pneumonia, with index cases having resided in or recently travelled to the Arabian peninsula, and is a global concern for public health. Limited human-to-human transmission, leading to some case clusters, has been reported. MERS-CoV has been reported in dromedary camels but phenotypic characterisation of such viruses is limited. We aimed to compare MERS-CoV isolates from dromedaries in Saudi Arabia and Egypt with a prototype human MERS-CoV to assess virus replication competence and cell tropism in ex-vivo cultures of human bronchus and lung.
  
  
  METHODS
  We characterised MERS-CoV viruses from dromedaries in Saudi Arabia and Egypt and compared them with a human MERS-CoV reference strain. We assessed viral replication kinetics and competence in Vero-E6 cells (rhesus monkey), tissue tropism in cultures of ex-vivo human bronchial and lung tissues, and cytokine and chemokine induction, gene expression, and quantification of viral RNA in Calu-3 cells (human respiratory tract). We used mock-infected tissue as negative controls for ex-vivo experiments and influenza A H5N1 as a positive control for cytokine and chemokine induction experiments in Calu-3 cells.
  
  
  RESULTS
  We isolated three dromedary strains, two from Saudi Arabia (Dromedary/Al-Hasa-KFU-HKU13/2013 [AH13] and Dromedary/Al-Hasa-KFU-HKU19D/2013 [AH19D]), and one from Egypt (Dromedary/Egypt-NRCE-HKU270/2013 [NRCE-HKU270]). The human and dromedary MERS-CoV strains had similar viral replication competence in Vero-E6 cells and respiratory tropism in ex-vivo cultures of the human respiratory tract, and had similar ability to evade interferon responses in the human-respiratory-tract-derived cell line Calu-3.
  
  
  CONCLUSIONS
  The similarity of virus tropism and replication competence of human and dromedary MERS-CoV from the Arabian peninsula, and genetically diverse dromedary viruses from Egypt, in ex-vivo cultures of the human respiratory tract suggests that dromedary viruses from Saudi Arabia and Egypt are probably infectious to human beings. Exposure to zoonotic MERS-CoV is probably occurring in a wider geographical region beyond the Arabian peninsula.
  
  
  BACKGROUND
  King Faisal University, Egyptian National Research Centre, Hong Kong Food and Health Bureau, National Institute of Allergy and Infectious Diseases, and European Community Seventh Framework Program.
authors.affiliation: Centre of Influenza Research and School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China; State Key Laboratory of Emerging Infectious Disease, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Renee W Y
authors.initials: RW
authors.lastname: Chan
authors.affiliation: Department of Microbiology and Parasitology, College of Veterinary Medicine, King Faisal University, Saudi Arabia; Department of Virology, Faculty of Veterinary Medicine, Kafrelsheikh University, Egypt.
authors.forename: Maged G
authors.initials: MG
authors.lastname: Hemida
authors.affiliation: Division of Virology, Department of Infectious Diseases, St Jude Children's Hospital, Memphis, TN, USA.
authors.forename: Ghazi
authors.initials: G
authors.lastname: Kayali
authors.affiliation: Centre of Influenza Research and School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China; State Key Laboratory of Emerging Infectious Disease, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Daniel K W
authors.initials: DK
authors.lastname: Chu
authors.affiliation: Centre of Influenza Research and School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China; State Key Laboratory of Emerging Infectious Disease, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Leo L M
authors.initials: LL
authors.lastname: Poon
authors.affiliation: Department of Clinical Studies, College of Veterinary Medicine, King Faisal University, Saudi Arabia.
authors.forename: Abdelmohsen
authors.initials: A
authors.lastname: Alnaeem
authors.affiliation: Center of Excellence for Influenza Viruses, National Research Center, Giza, Egypt.
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Ali
authors.affiliation: Centre of Influenza Research and School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China; State Key Laboratory of Emerging Infectious Disease, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Kin P
authors.initials: KP
authors.lastname: Tao
authors.affiliation: Centre of Influenza Research and School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China; State Key Laboratory of Emerging Infectious Disease, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Hoi Y
authors.initials: HY
authors.lastname: Ng
authors.affiliation: Centre of Influenza Research and School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China; State Key Laboratory of Emerging Infectious Disease, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Michael C W
authors.initials: MC
authors.lastname: Chan
authors.affiliation: Centre of Influenza Research and School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China; State Key Laboratory of Emerging Infectious Disease, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Guan
authors.affiliation: Department of Pathology, Queen Mary Hospital, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China. Electronic address: nicholls@pathology.hku.hk.
authors.forename: John M
authors.initials: JM
authors.lastname: Nicholls
authors.affiliation: Centre of Influenza Research and School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China; State Key Laboratory of Emerging Infectious Disease, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China. Electronic address: malik@hku.hk.
authors.forename: J S Malik
authors.initials: JS
authors.lastname: Peiris
mesh_terms: D000818:Animals; D002162:Camelus; D018352:Coronavirus Infections / Q000821:virology*; D004534:Egypt; D006801:Humans; D065207:Middle East Respiratory Syndrome Coronavirus / Q000472:pathogenicity / Q000502:physiology*; D012137:Respiratory System / Q000821:virology*; D012529:Saudi Arabia; D056189:Viral Tropism; D014779:Virus Replication