Interactions of Rodent Coronaviruses with Cellular Receptors
Uniformed Services University Of The Health Sciences Bethesda United States
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Coronaviruses express a spike glycoprotein S on the viral envelope and a subset of coronaviruses expresses an additional glycoprotein HE, that binds to a sugar moiety and has hemagglutinating and acetylesterase activities. This dissertation focuses on how interactions of these membrane glycoproteins with cell surface molecules affects virus species specificity and tissue tropism. To study the role of the HE glycoprotein in MHV infection we used the anti-receptor MAD-eel to block binding of S to its receptor on various mouse cell lines and then challenged these cells with an HE expressing strain of MEV to determine whether this virus could use the HE alone to initiate viral infection . When the S glycoprotein was prevented from binding to its receptor by MAb-CCl an MEV strain expressing, HE could not infect mouse fibroblast cell lines or primary brain cells. Although murine coronavirus MHV and rat coronavirus both cause common infections in colonies of laboratory rodents and are related antigenically, each virus is restricted to a single host species and the target organs for the mouse and rat viruses are different. A solid phase virus-binding assay was used to investigate the tissue specificity of binding of rat coronavirus. Rat coronavirus bound to membranes isolated from rat parotid and lacrimal glands, correlating well with the natural target tissues of this virus. Both rat coronavirus and MHV can infect the same murine cell line. The hypothesis that rat homologs of the MHV receptor MHVR serve as receptors for rat coronavirus was tested. Antibodies to the MHV receptor that protected these cells against MHV infection, did not protect them against infection with rat coronavirus suggesting that the rat virus does not use MHVR to infect these cells. Rat ecto-ATPase, a glycoprotein homologous to MHVR was expressed in nonpermissive hamster cells, but the cells remained resistant to infection with rat coronavirus.