Dissemination of MHV4 (strain JHM) infection does not require specific coronavirus receptors

In this report, we demonstrate the syncytial spread of MHV4 (strain JHM) infection through non-murine cell cultures which lack a specific MHV4 receptor and are therefore resistant to infection by free virions. This was achieved by allowing infected murine cells to settle onto confluent monolayers of non-murine cells in a straightforward infectious center assay. Receptor-independent syncytium formation induced by cells expressing the MHV4 spike (S) from recombinant vaccinia viruses (VV) indicated that spread was mediated by this coronavirus glycoprotein. We conclude that the S protein of MHV4 is so potently fusogenic that it does not require prior binding to a virus-specific surface receptor to induce fusion of closely-opposed plasma membranes.