ABSTRACT
Respiratory syncytial virus (RSV) is the major cause of lower respiratory tract disease in infants. Previously, we elucidated the antibody repertoire following primary RSV infection in infants. Whole genome-fragment phage display libraries (GFPDL) expressing linear and conformational epitopes from RSV bound 100-fold more phages within attachment protein (G) following primary RSV infection. The G-reactive epitopes spanned the N- and C-termini of G ectodomain, in addition to the central conserved domain (CCD). In the current study, we examined the contribution of antigenic regions of G outside of the CCD to RSV-specific immunity. We evaluated the immunogenicity, neutralization and protective efficacy of all RSV-G antigenic sites identified following primary RSV infection using recombinant E. coli expressed G ectodomain (REG), CCD-deleted G ectodomain (REG ΔCCD), N- and C-terminal G subdomains, and antigenic site peptides. The REG ΔCCD, N- and C-terminal subdomains and peptides generated antibody titers in rabbits and mice that bound fully glycosylated Recombinant Mammalian expressed G ectodomain (RMG) and intact RSV virion particles but minimal in vitro neutralization titers compared with the intact G ectodomain. Vaccinated mice were challenged intranasally with RSV-A2 Line 19F. Viral replication in nasal cavity and lungs was significantly reduced in vaccinated animals compared to unimmunized controls. Control of viral loads post-RSV challenge correlated with serum antibody binding to the virus particles. In addition, very low Th2/Th1 cytokine ratios were found in the lungs of REG ΔCCD vaccinated mice after challenge. These data demonstrate the presence of multiple protective sites in RSV G protein outside of the CCD that could contribute to the development of a bacterially produced unglycosylated G protein as safe and protective vaccine against RSV disease.
Subject(s)
Antibodies, Neutralizing , Respiratory Syncytial Virus Infections/prevention & control , Respiratory Syncytial Virus Vaccines , Viral Envelope Proteins/chemistry , Viral Envelope Proteins/immunology , A549 Cells , Animals , Antibodies, Neutralizing/chemistry , Antibodies, Neutralizing/genetics , Antibodies, Neutralizing/immunology , Cells, Cultured , Conserved Sequence/genetics , Cysteine/chemistry , Cysteine/genetics , Epitope Mapping , Epitopes/chemistry , Epitopes/genetics , Epitopes/immunology , Female , Humans , Immunization , Mice , Mice, Inbred BALB C , Protein Domains/genetics , Protein Domains/immunology , Rabbits , Respiratory Syncytial Virus Infections/immunology , Respiratory Syncytial Virus Infections/pathology , Respiratory Syncytial Virus Vaccines/chemical synthesis , Respiratory Syncytial Virus Vaccines/chemistry , Respiratory Syncytial Virus Vaccines/genetics , Respiratory Syncytial Virus, Human/chemistry , Respiratory Syncytial Virus, Human/genetics , Respiratory Syncytial Virus, Human/immunology , Viral Envelope Proteins/genetics , Viral Fusion Proteins/chemistry , Viral Fusion Proteins/genetics , Viral Fusion Proteins/immunologyABSTRACT
Respiratory syncytial virus (RSV) is the most important causative agent of respiratory tract infections. Young children with chronic lung or congenital heart disease are at increased risk for severe disease. Intensive research into a candidate vaccine has yielded live attenuated vaccines and subunit vaccines, which have been studied in humans. Although immunogenic, occurrence of upper respiratory tract infection symptoms with live attenuated vaccine prohibits evaluation in young infants. Subunit vaccines include purified F protein (PFP-1 and -2) and BBG2Na. PFP vaccines are effective in seropositive children, but also induce upper respiratory symptoms. BBG2Na was being investigated in phase III clinical trials, however, further development has now been discontinued. This review discusses recent advances in RSV vaccine development.
