Recombinant bovine respiratory syncytial virus with deletions of the G or SH genes: G and F proteins bind heparin

Bovine respiratory syncytial virus (BRSV) encodes three transmembrane envel ope glycoproteins, namely the small hydrophobic (SH) protein, the attachmen t glycoprotein (G) and the fusion glycoprotein (F). The BRSV reverse geneti cs system has been used to generate viable recombinant BRSV lacking either the G gene or the SH gene or both genes. The deletion mutants were fully co mpetent for multicycle growth in cell culture, proving that, of the BRSV gl ycoprotein genes, the SH and G genes are non-essential. Virus morphogenesis was not impaired by either of the deletions. The deletion mutants were use d to study the role of the F glycoprotein and the contributions of SH and G with respect to virus attachment, Attachment mediated by the F protein alo ne could be blocked by soluble heparin, but not by chondroitin sulphate. He parin affinity chromatography revealed that both the BRSV G and F glycoprot eins have heparin-binding activity, with the affinity of the F glycoprotein being significantly lower than that of G. Therefore, the roles of the BRSV glycoproteins in virus attachment and receptor binding have to be reconsid ered.