title: Cotton rat immune responses to virus-like particles containing the pre-fusion form of respiratory syncytial virus fusion protein.
abstract: BACKGROUND
  Virus-like particles (VLPs) based on Newcastle disease virus (NDV) core proteins, M and NP, and containing two chimera proteins, F/F and H/G, composed of the respiratory syncytial virus (RSV) fusion protein (F) and glycoprotein (G) ectodomains fused to the transmembrane and cytoplasmic domains of the NDV F and HN proteins, respectively, stimulate durable, protective anti-RSV neutralizing antibodies in mice. Furthermore, immunization of mice with a VLP containing a F/F chimera protein with modifications previously reported to stabilize the pre-fusion form of the RSV F protein resulted in significantly improved neutralizing antibody titers over VLPs containing the wild type F protein. The goal of this study was to determine if VLPs containing the pre-fusion form of the RSV F protein stimulated protective immune responses in cotton rats, a more RSV permissive animal model than mice.
  
  
  METHODS
  Cotton rats were immunized intramuscularly with VLPs containing stabilized pre-fusion F/F chimera protein as well as the H/G chimera protein. The anti-RSV F and RSV G antibody responses were determined by ELISA. Neutralizing antibody titers in sera of immunized animals were determined in plaque reduction assays. Protection of the animals from RSV challenge was assessed. The safety of the VLP vaccine was determined by monitoring lung pathology upon RSV challenge of immunized animals.
  
  
  RESULTS
  The Pre-F/F VLP induced neutralizing titers that were well above minimum levels previously proposed to be required for a successful vaccine and titers significantly higher than those stimulated by RSV infection. In addition, Pre-F/F VLP immunization stimulated higher IgG titers to the soluble pre-fusion F protein than RSV infection. Cotton rats immunized with Pre-F/F VLPs were protected from RSV challenge, and, importantly, the VLP immunization did not result in enhanced respiratory disease upon RSV challenge.
  
  
  CONCLUSIONS
  VLPs containing the pre-fusion RSV F protein have characteristics required for a safe, effective RSV vaccine.
authors.affiliation: Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA, 01655, USA. lori.mcGinnes@umassmed.edu.
authors.forename: Lori McGinnes
authors.initials: LM
authors.lastname: Cullen
authors.affiliation: Sigmovir Biosystems Inc., Rockville, MD, 20850, USA. j.blanco@sigmovir.com.
authors.forename: Jorge C G
authors.initials: JC
authors.lastname: Blanco
authors.affiliation: Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA, 01655, USA. trudy.morrison@umassmed.edu.|Program in Immunology and Microbiology, University of Massachusetts Medical School, Worcester, MA, 01655, USA. trudy.morrison@umassmed.edu.
authors.forename: Trudy G
authors.initials: TG
authors.lastname: Morrison
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood; D000914:Antibodies, Viral / Q000097:blood; D001717:Birds; D019556:COS Cells; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D004195:Disease Models, Animal; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005347:Fibroblasts / Q000821:virology; D006801:Humans; D007114:Immunization; D008168:Lung / Q000473:pathology; D051379:Mice; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000276:immunology*; D018357:Respiratory Syncytial Virus Infections / Q000276:immunology*; D012136:Respiratory Syncytial Viruses; D016205:Sigmodontinae; D016622:Silver Staining; D058425:Vaccines, Virus-Like Particle / Q000276:immunology*; D014709:Vero Cells
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D011993:Recombinant Fusion Proteins; D058425:Vaccines, Virus-Like Particle