A Recombinant Respiratory Syncytial Virus Vaccine Candidate Attenuated by a Low-Fusion F Protein Is Immunogenic and Protective against Challenge in Cotton Rats.
Although respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections in infants, a safe and effective vaccine is not yet available. Live-attenuated vaccines (LAVs) are the most advanced vaccine candidates in RSV-naive infants. However, designing an LAV with appropriate attenuation yet sufficient immunogenicity has proven challenging. In this study, we implemented reverse genetics to address these obstacles with a multifaceted LAV design that combined the codon deoptimization of genes for nonstructural proteins NS1 and NS2 (dNS), deletion of the small hydrophobic protein (ΔSH) gene, and replacement of the wild-type fusion (F) protein gene with a low-fusion RSV subgroup B F consensus sequence of the Buenos Aires clade (BAF). This vaccine candidate, RSV-A2-dNS-ΔSH-BAF (DB1), was attenuated in two models of primary human airway epithelial cells and in the upper and lower airways of cotton rats. DB1 was also highly immunogenic in cotton rats and elicited broadly neutralizing antibodies against a diverse panel of recombinant RSV strains. When vaccinated cotton rats were challenged with wild-type RSV A, DB1 reduced viral titers in the upper and lower airways by 3.8 log10 total PFU and 2.7 log10 PFU/g of tissue, respectively, compared to those in unvaccinated animals (P < 0.0001). DB1 was thus attenuated, highly immunogenic, and protective against RSV challenge in cotton rats. DB1 is the first RSV LAV to incorporate a low-fusion F protein as a strategy to attenuate viral replication and preserve immunogenicity.



RSV is a leading cause of infant hospitalizations and deaths. The development of an effective vaccine for this high-risk population is therefore a public health priority. Although live-attenuated vaccines have been safely administered to RSV-naive infants, strategies to balance vaccine attenuation with immunogenicity have been elusive. In this study, we introduced a novel strategy to attenuate a recombinant RSV vaccine by incorporating a low-fusion, subgroup B F protein in the genetic background of codon-deoptimized nonstructural protein genes and a deleted small hydrophobic protein gene. The resultant vaccine candidate, DB1, was attenuated, highly immunogenic, and protective against RSV challenge in cotton rats.
Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA.|Children's Healthcare of Atlanta, Atlanta, Georgia, USA.
Christina A
CA
Rostad
Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA.|Children's Healthcare of Atlanta, Atlanta, Georgia, USA.
Christopher C
CC
Stobart
Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA.
Brian E
BE
Gilbert
Marsico Lung Institute and Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
Ray J
RJ
Pickles
Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA.|Children's Healthcare of Atlanta, Atlanta, Georgia, USA.
Anne L
AL
Hotard
Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA.|Children's Healthcare of Atlanta, Atlanta, Georgia, USA.
Jia
J
Meng
Sigmovir Biosystems Inc., Rockville, Maryland, USA.
Jorge C G
JCG
Blanco
Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Syed M
SM
Moin
Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Barney S
BS
Graham
Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA.|Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA.
Pedro A
PA
Piedra
Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA martin.moore@emory.edu.|Children's Healthcare of Atlanta, Atlanta, Georgia, USA.
Martin L
ML
Moore
D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood; D000914:Antibodies, Viral / Q000097:blood; D002460:Cell Line; D004195:Disease Models, Animal; D004847:Epithelial Cells / Q000502:physiology / Q000821:virology; D006801:Humans; D018357:Respiratory Syncytial Virus Infections / Q000473:pathology / Q000517:prevention & control*; D022261:Respiratory Syncytial Virus Vaccines / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D018113:Respiratory Syncytial Virus, Human / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity; D012136:Respiratory Syncytial Viruses; D012137:Respiratory System / Q000821:virology; D059386:Reverse Genetics; D016205:Sigmodontinae; D016896:Treatment Outcome; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D014760:Viral Fusion Proteins / Q000235:genetics*; D019562:Viral Load
D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; C526850:F protein, human respiratory syncytial virus; D022261:Respiratory Syncytial Virus Vaccines; D014613:Vaccines, Attenuated; D014760:Viral Fusion Proteins