CHARACTERIZATION OF AVIAN REOVIRUS-INDUCED CELL-FUSION - THE ROLE OF VIRAL STRUCTURAL PROTEINS

Cell fusion induced by avian reovirus was analyzed using virus strain FC and Vero cells. One-step growth curves showed that cell fusion was directly associated with viral replication. Cell fusion occurred most efficiently at basic pH (8.0-8.5) and fusion from without could not be demonstrated. Actinomycin D, at low concentrations, increased cell fusion, and cycloheximide prevented cell fusion, indicating that viral protein(s) were responsible for the induction of cell fusion. Immunofluorescence tests indicated that viral proteins were present on the infected cell surface. Radioimmunoprecipitation identified structural proteins μ2C and σ2 as predominant viral protein species present on the infected cell surface. Cell fusion was inhibited by virus-specific antisera, suggesting that μ2C and/or σ2 present on the infected cell surface were involved in the induction of cell fusion. Trypsin and chymotrypsin treatment of purified viruses cleaved both μ2C and σ2 proteins, but generated different cleavage products with each protein. The addition of trypsin to the culture media following infection increased cell fusion, whereas chymotrypsin treatment decreased cell fusion. The opposite effects of trypsin and chymotrypsin on the cell fusion, together with the different specificities of these two proteases in cleavage of μ2C and σ2 proteins, further suggest that the cell surface-associated μ2C and/or σ2 are involved in the syncytium formation. © 1993 American Health Foundation and Academic Press.