Morphogenesis of Coronavirus HCoV-NL63 in Cell Culture: A Transmission Electron Microscopic Study

Jan M. Orenstein*, 1, Bridget S. Banach2, Susan C. Baker2
1 Department of Pathology, George Washington University School of Medicine, 2300 Eye Street NW, Washington, DC, USA
2 Department of Microbiology and Immunology, Loyola University Chicago Stritch School of Medicine, 2160 South First Ave, Maywood, IL, USA

© 2008 Orenstein et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Department of Pathology, Ross 502, George Washington University Medical Center, 2300 Eye Street NW, Washington, DC 20037, USA. E-mail:


NL63 (HCoV-NL63) is a recently discovered human coronavirus that causes respiratory disease in infants and young children. NL63 productively infects LLCMK2 cells and ciliated epithelial cells of human airway cell cultures. Transmission electron microscopic (TEM) studies of NL63 infected LLCMK2 cells revealed that virions are spherical, spiked, and range from 75 to 115 nm in diameter. Virus replication predominantly occurs on the rough endoplasmic reticulum (RER), both perinuclear and cytoplasmic, and the Golgi. Plasma membrane budding was occasionally observed. As virus production increased, aberrant viral forms appeared with greater frequency. Unusual inclusions were present in infected cells including tubular and laminated structures. Pleomorphic double membrane-bound vesicles (DMV), measuring roughly 140 to 210 nm in diameter, were observed. The virus was released via exocytosis and cell lysis. In summary, we report the key morphologic characteristics of NL63 infection observed by TEM analysis.

Keywords: Aberrant, coronavirus, HCoV-NL63.