title: Identification of residues in the human respiratory syncytial virus fusion protein that modulate fusion activity and pathogenesis.
abstract: Human respiratory syncytial virus (RSV) lower respiratory tract infection can result in inflammation and mucus plugging of airways. RSV strain A2-line19F induces relatively high viral load and mucus in mice. The line 19 fusion (F) protein harbors five unique residues compared to the non-mucus-inducing strains A2 and Long, at positions 79, 191, 357, 371, and 557. We hypothesized that differential fusion activity is a determinant of pathogenesis. In a cell-cell fusion assay, line 19 F was more fusogenic than Long F. We changed the residues unique to line 19 F to the corresponding residues in Long F and identified residues 79 and 191 together as responsible for high fusion activity. Surprisingly, mutation of residues 357 or 357 with 371 resulted in gain of fusion activity. Thus, we generated RSV F mutants with a range of defined fusion activity and engineered these into recombinant viruses. We found a clear, positive correlation between fusion activity and early viral load in mice; however, we did not detect a correlation between viral loads and levels of airway mucin expression. The F mutant with the highest fusion activity, A2-line19F-K357T/Y371N, induced high viral loads, severe lung histopathology, and weight loss but did not induce high levels of airway mucin expression. We defined residues 79/191 as critical for line 19 F fusion activity and 357/371 as playing a role in A2-line19F mucus induction. Defining the molecular basis of the role of RSV F in pathogenesis may aid vaccine and therapeutic strategies aimed at this protein.
  
  
  OBJECTIVE
  Human respiratory syncytial virus (RSV) is the most important lower respiratory tract pathogen of infants for which there is no vaccine. Elucidating mechanisms of RSV pathogenesis is important for rational vaccine and drug design. We defined specific amino acids in the fusion (F) protein of RSV strain line 19 critical for fusion activity and elucidated a correlation between fusion activity and viral load in mice. Further, we identified two distinct amino acids in F as contributing to the mucogenic phenotype of the A2-line19F virus. Taken together, these results illustrate a role for RSV F in virulence.
authors.affiliation: Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA Children's Healthcare of Atlanta, Atlanta, Georgia, USA.
authors.forename: Anne L
authors.initials: AL
authors.lastname: Hotard
authors.affiliation: Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA Children's Healthcare of Atlanta, Atlanta, Georgia, USA.
authors.forename: Sujin
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA Children's Healthcare of Atlanta, Atlanta, Georgia, USA.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Currier
authors.affiliation: Department of Pathology, Microbiology and Immunology, Vanderbilt Medical Center, Nashville, Tennessee, USA Department of Pediatrics, Vanderbilt Medical Center, Nashville, Tennessee, USA The Vanderbilt Vaccine Center of Vanderbilt Medical Center, Nashville, Tennessee, USA.
authors.forename: James E
authors.initials: JE
authors.lastname: Crowe
authors.affiliation: Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA.
authors.forename: Kaori
authors.initials: K
authors.lastname: Sakamoto
authors.affiliation: Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennesee, USA.
authors.forename: Dawn C
authors.initials: DC
authors.lastname: Newcomb
authors.affiliation: Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennesee, USA.
authors.forename: R Stokes
authors.initials: RS
authors.lastname: Peebles
authors.affiliation: Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia, USA.
authors.forename: Richard K
authors.initials: RK
authors.lastname: Plemper
authors.affiliation: Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA Children's Healthcare of Atlanta, Atlanta, Georgia, USA martin.moore@emory.edu.
authors.forename: Martin L
authors.initials: ML
authors.lastname: Moore
mesh_terms: D000818:Animals; D002460:Cell Line; D004252:DNA Mutational Analysis; D004195:Disease Models, Animal; D005260:Female; D006651:Histocytochemistry; D006801:Humans; D008168:Lung / Q000473:pathology / Q000821:virology; D008807:Mice, Inbred BALB C; D018357:Respiratory Syncytial Virus Infections / Q000473:pathology / Q000821:virology; D018113:Respiratory Syncytial Virus, Human / Q000472:pathogenicity / Q000502:physiology*; D014760:Viral Fusion Proteins / Q000235:genetics* / Q000378:metabolism*; D019562:Viral Load; D053586:Virus Internalization; D015431:Weight Loss
chemical_list: C526850:F protein, human respiratory syncytial virus; D014760:Viral Fusion Proteins