Morphology and morphogenesis of SARS-CoV-2 in Vero-E6 cells

Abstract

BACKGROUNDThe coronaviruses (CoVs) called the attention of the world for causing outbreaks of severe acute respiratory syndrome (SARS-CoV), in Asia in 2002-03, and respiratory disease in the Middle East (MERS-CoV), in 2012. In December 2019, yet again a new coronavirus (SARS-CoV-2) first identified in Wuhan, China, was associated with a severe respiratory infection, known today as COVID-19. This new virus quickly spread throughout China and 30 additional countries. As result, the World Health Organization (WHO) elevated the status of the COVID-19 outbreak from emergency of international concern to pandemic on March 11, 2020. The impact of COVID-19 on public health and economy fueled a worldwide race to approve therapeutic and prophylactic agents, but so far, there are no specific antiviral drugs or vaccines available. In current scenario, the development of in vitro systems for viral mass production and for testing antiviral and vaccine candidates proves to be an urgent matter.OBJECTIVE The objective of this paper is study the biology of SARS-CoV-2 in Vero-E6 cells at the ultrastructural level.METHODS In this study, we documented, by transmission electron microscopy and real-time reverse transcription polymerase chain reaction (RT-PCR), the infection of Vero-E6 cells with SARS-CoV-2 samples isolated from Brazilian patients.FINDINGS The infected cells presented cytopathic effects and SARS-CoV-2 particles were observed attached to the cell surface and inside cytoplasmic vesicles. The entry of the virus into cells occurred through the endocytic pathway or by fusion of the viral envelope with the cell membrane. Assembled nucleocapsids were verified inside rough endoplasmic reticulum cisterns (RER). Viral maturation seemed to occur by budding of viral particles from the RER into smooth membrane vesicles.MAIN CONCLUSIONS Therefore, the susceptibility of Vero-E6 cells to SARS-CoV-2 infection and the viral pathway inside the cells were demonstrated by ultrastructural analysis.

SARS-CoV-2: Ultrastructural Characterization of Morphogenesis in an In Vitro System

“…We observed that the entry of the SARS-CoV-2 into the host cell occurs most commonly by endocytosis, although the fusion of the virus envelope with the cell membrane has also been observed. This is consistent with our previous ultrastructural studies with SARS-CoV-2 [23] and others from literature with SARS-CoV and MERS-CoV which support both mechanisms [9,43,44].…”

“…We believe that the role of filopodia in this in vitro model is associated with infection maximization. In vitro studies with Vero cells with SARS-CoV and SARS-CoV-2 corroborate our findings [23,31,32]. Enveloped viruses can spread by two different routes: the cell-free aqueous environment or by cell-to-cell contact [33][34][35].…”

“…Vero cells, which are widely used in virus studies and in the production of human vaccines, have been shown to be a relevant model for studies of coronaviruses including SARS-CoV, SARS-CoV-2, and MERS-CoV [17][18][19][20][21][22][23].…”

An intra-cytoplasmic route for SARS-CoV-2 transmission unveiled by Helium-ion microscopy

“…It has been reported that SARS-CoV-2 infected Vero E6 cells produce many lopodia, and they are longer than those present in uninfected cells 16,17 . We observed these very long lopodia and followed their path.…”

COVID-19 Shuts Doors to Flu but Keeps Them Open to Rhinoviruses

“…The lipid envelope of SARS-CoV-2 contains an envelope protein, a spike protein S, and a membrane protein. The nucleocapsid protein forms the virion core encased in the viral genome [ 17 ]. The S protein mediates viral binding to the host cell surface [ 28 ].…”