Role of the virus -glycan interaction in the infection mechanism of coronaviruses

Abstract

This study explores how human coronaviruses (CoVs), namely MERS-CoV, HCoV-HKU1, SARS-CoV-1, and SARS-CoV-2, infect cells, focusing on the role of their spike (S) proteins and interac ons with cell surface receptors. It aims to understand how CoVs use both proteinaceous and sialylated glycan receptors to a ach to cells. To safely study these interac ons, we used pseudoviruses which are non- infec ous and non-replica ve par cles that express S proteins. Ini al luciferase assay showed no infec on from pseudoviruses, including SARS-CoV-2. Due to issues like variability in results and poten al mismatches in S protein domains, the assay was repeated. A er improving the prepara on methods and ensuring the S1 and S2 protein regions were homogenized and compa ble, we observed infec on by SARS-CoV-2 pseudoviruses in HEK ACE2 TMPRSS2 cells, which was expectedly lost in RD cells. However, pseudoviruses for MERS-CoV and HCoV-HKU1 s ll failed to infect either cell line. Further tes ng of S protein domains-cell line interac ons using FACS showed that while some S protein regions could bind certain cell lines, it was never observed for both domains of the same CoV simultaneously which might explain the absence of infec on in the luciferase assay. A key factor may also be the incompa bility of the S protein’s transmembrane domain (TMD), which helps stabilize the S protein. Mismatched TMDs could disrupt the S protein’s func on. The next step is to improve pseudovirus design by matching TMDs with other S protein regions. Achieving successful infec on will allow us to study how different receptors contribute to viral a achment and entry, advancing strategies to fight CoV infecons.