Analysis of bovine respiratory syncytial virus envelope glycoproteins in cell fusion.

To compare the requirements for respiratory syncytial virus (RSV)-mediated cell fusion, the fusion (F), attachment (G) and small hydrophobic (SH) glycoproteins of bovine RSV (BRSV), ovine RSV (ORSV) and human RSV (HRSV) were expressed individually or coexpressed in either homologous or heterologous combinations in HeLa cells, using the vaccinia virus-T7 polymerase transient expression system. Cell fusion was examined by a reporter gene activation assay. Although the expression of the F protein alone or coexpression of the F and G proteins or the F and SH proteins induced cell fusion, coexpression of F, G and SH proteins induced extensive cell fusion. Coexpression of various combinations of envelope glycoproteins of BRSV, ORSV and HRSV indicated that substitution of heterologous SH protein affects the effective fusigenic properties of the BRSV F protein far more than that obtained by substituting the heterologous G protein.