Seasonal Human Coronaviruses OC43, 229E, and NL63 Induce Cell Surface Modulation of Entry Receptors and Display Host Cell-Specific Viral Replication Kinetics (preprint)

The emergence of the COVID-19 pandemic prompted increased interest in seasonal human coronaviruses. 229E, OC43, NL63 and HKU1 are endemic seasonal coronaviruses that cause the common cold and are associated with generally mild respiratory symptoms. In this study, we identified cell lines that exhibited cytopathic effects (CPE) upon infection by three of these coronaviruses and characterized their viral replication kinetics and the effect of infection on host surface receptor expression. We found that NL63 produced CPE in LLC-MK2 cells, while OC43 produced CPE in MRC-5, HCT-8 and WI-38 cell lines, while 229E produced CPE in MRC-5 and WI-38 by day 3 post-infection. We observed a sharp increase in nucleocapsid and spike viral RNA (vRNA) from day 3 to day 5 post-infection for all viruses, however the abundance and the proportion of vRNAs copies measured in the supernatants and cell lysates of infected cells varied considerably depending on the virus-host cell pair. Importantly, we observed modulation of coronavirus entry and attachment receptors upon infection. Infection with 229E and OC43 led to a downregulation of CD13 and GD3, respectively. In contrast, infection with NL63, and also with OC43, lead to an increase in ACE2 expression. Attempts to block entry of NL63 using either soluble ACE2 or anti-ACE2 monoclonal antibodies demonstrated the potential of these strategies to greatly reduce infection. Overall, our results enable a better understanding of seasonal coronaviruses infection kinetics in permissive cell lines, and reveal entry receptor modulation that may have implications in facilitating co-infections with multiple coronaviruses in humans. IMPORTANCESeasonal human coronavirus are an important cause of the common cold associated with generally mild upper respiratory tract infections that can result in respiratory complications for some individuals. There are no vaccines available for these viruses, with only limited antiviral therapeutic options to treat the most severe cases. A better understanding of how these viruses interact with host cells is essential to identify new strategies to prevent infection-related complications. By analyzing viral replication kinetics in different permissive cell lines, we find that cell-dependent host factors influence how viral genes are expressed and virus particles released. We also analyzed entry receptor expression on infected cells and found that these can be up or down modulated depending on the infecting coronavirus. Our findings raise concerns over the possibility of infection enhancement upon co-infection by some coronaviruses, which may facilitate genetic recombination and the emergence of new variants and strains.

Meta-Analysis of the Dynamics of the Emergence of Mutations and Variants of SARS-CoV-2 (preprint)

The novel Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) emerged in late December 2019 in Wuhan, China, and is the causative agent for the worldwide COVID-19 pandemic. SARS-CoV-2 is a 29,811 nucleotides positive-sense single-stranded RNA virus belonging to the betacoronavirus genus. Due to inefficient proofreading ability of the viral RNA-dependent polymerase complex, coronaviruses are known to acquire new mutations following replication, which constitutes one of the main factors driving the evolution of its genome and the emergence of new genetic variants. In the last few months, the identification of new B.1.1.7 (UK), B.1.351 (South Africa) and P.1 (Brazil) variants of concern (VOC) highlighted the importance of tracking the emergence of mutations in the SARS-CoV-2 genome and their impact on transmissibility, infectivity, and neutralizing antibody escape capabilities. These VOC demonstrate increased transmissibility and antibody escape, and reduce current vaccine efficacy. Here we analyzed the appearance and prevalence trajectory of mutations that appeared in all SARS-CoV-2 genes from December 2019 to January 2021. Our goals were to identify which modifications are the most frequent, study the dynamics of their spread, their incorporation into the consensus sequence, and their impact on virus biology. We also analyzed the structural properties of the spike glycoprotein of the B.1.1.7, B.1.351 and P.1 variants. This study offers an integrative view of the emergence, disappearance, and consensus sequence integration of successful mutations that constitute new SARS-CoV-2 variants and their impact on neutralizing antibody therapeutics and vaccines.