Tropism and replication of Middle East respiratory syndrome coronavirus from dromedary camels in the human respiratory tract: an in-vitro and ex-vivo study

Lancet Respir Med. 2014 Oct;2(10):813-22. doi: 10.1016/S2213-2600(14)70158-4. Epub 2014 Aug 28.

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.

Findings: 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.

Interpretation: 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.

Funding: 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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Camelus
  • Coronavirus Infections / virology*
  • Egypt
  • Humans
  • Middle East Respiratory Syndrome Coronavirus / pathogenicity
  • Middle East Respiratory Syndrome Coronavirus / physiology*
  • Respiratory System / virology*
  • Saudi Arabia
  • Viral Tropism*
  • Virus Replication*