ABSTRACT
Unremitting emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants imposes us to continuous control measurement. Given the rapid spread, new Omicron subvariant named BA.5 is urgently required for characterization. Here we analyzed BA.5 with the other Omicron variants BA.1, BA.2, and ancestral B.1.1 comprehensively. Although in vitro growth kinetics of BA.5 is comparable among the Omicron subvariants, BA.5 become much more fusogenic than BA.1 and BA.2. The airway-on-a-chip analysis showed that the ability of BA.5 to disrupt the respiratory epithelial and endothelial barriers is enhanced among Omicron subvariants. Furthermore, in our hamster model, in vivo replication of BA.5 is comparable with that of the other Omicrons and less than that of the ancestral B.1.1. Importantly, inflammatory response against BA.5 is strong compared with BA.1 and BA.2. Our data suggest that BA.5 is still low pathogenic compared to ancestral strain but evolved to induce enhanced inflammation when compared to prior Omicron subvariants.
ABSTRACT
The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has threatened human health and the global economy. Development of additional vaccines and therapeutics is urgently required, but such development with live virus must be conducted with biosafety level 3 confinement. Pseudotyped viruses have been widely adopted for studies of virus entry and pharmaceutical development to overcome this restriction. Here we describe a modified protocol to generate vesicular stomatitis virus (VSV) pseudotyped with SARS-CoV or SARS-CoV-2 Spike protein in high yield. We found that pseudovirions produced with the conventional transient expression system lacked coronavirus Spike protein at their surface as a result of inhibition of parental VSV infection by overexpression of this protein. Establishment of stable cell lines with an optimal expression level of coronavirus Spike protein allowed the efficient production of progeny pseudoviruses decorated with Spike protein. This improved VSV pseudovirus production method should facilitate studies of coronavirus entry and development of antiviral agents.
