title: Contribution of the respiratory syncytial virus G glycoprotein and its secreted and membrane-bound forms to virus replication in vitro and in vivo.
abstract: The surface glycoproteins of viruses can play important roles in viral attachment, entry, and morphogenesis. Here, we investigated the role of the attachment G glycoprotein of human respiratory syncytial virus (RSV) in viral infection. RSV G is produced both as a complete, transmembrane form and as an N-terminally truncated form that is secreted. Using reverse genetics, we created mutant recombinant RSVs (rRSV) that do not express G (DeltaG) or express either the secreted or the membrane-bound form of G only (sG and mG, respectively). In Vero cells, the DeltaG virus formed plaques and grew as efficiently as wild-type rRSV and mG. In contrast, DeltaG replicated less efficiently and did not form distinct plaques in HEp-2 cells. This defect was primarily at the level of the initiation of infection, with only a minor additional effect at the level of packaging. Replication of DeltaG in the respiratory tract of mice was very highly restricted, indicating that G is important in vivo. Although the G protein expressed by the sG virus was confirmed to be secreted, this virus grew at least as efficiently as wild-type in HEp-2 cells and was only moderately attenuated in vivo. Thus, the G protein was important for efficient replication in HEp-2 cells and in vivo, but this function could be supplied in large part by the secreted form and thus does not require the cytoplasmic and transmembrane domains. Amino acids 184-198 have been identified as the major heparin-binding domain of the G protein and were implicated in mediating binding to cells [S. A. Feldman et al., 1999, J. Virol. 73, 6610-6617]. Heparin-like glycosaminoglycans also appeared to be important for infection in vitro by direct clinical isolates of RSV. Deletion of amino acids 187-197 from rRSV did not reduce its sensitivity to neutralization in vitro by incubation with soluble heparin, did not reduce its efficiency of growth in vitro, and resulted in only a modest reduction in vivo. Thus, the putative heparin-binding domain is not the sole determinant of heparin sensitivity and is not a critical functional domain.
authors.affiliation: Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, 7 Center Dr. MSC 0720, Bethesda, Maryland 20892-0720, USA.
authors.forename: M N
authors.initials: MN
authors.lastname: Teng
authors.forename: S S
authors.initials: SS
authors.lastname: Whitehead
authors.forename: P L
authors.initials: PL
authors.lastname: Collins
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism / Q000821:virology; D002522:Chlorocebus aethiops; D004305:Dose-Response Relationship, Drug; D015707:HN Protein / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009154:Mutation; D018357:Respiratory Syncytial Virus Infections / Q000821:virology*; D012136:Respiratory Syncytial Viruses / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D014709:Vero Cells; D014759:Viral Envelope Proteins; D014779:Virus Replication / Q000187:drug effects
chemical_list: D015707:HN Protein; D014759:Viral Envelope Proteins; C116204:attachment protein G; D006493:Heparin