Rational design of a highly immunogenic prefusion-stabilized F glycoprotein antigen for a respiratory syncytial virus vaccine

Abstract

Respiratory syncytial virus (RSV) is the leading, global cause of serious respiratory disease in infants and is an important cause of respiratory illness in older adults. No RSV vaccine is currently available. The RSV fusion (F) glycoprotein is a key antigen for vaccine development, and its prefusion conformation is the target of the most potent neutralizing antibodies. Here, we describe a computational and experimental strategy for designing immunogens that enhance the conformational stability and immunogenicity of RSV prefusion F. We obtained an optimized vaccine antigen after screening nearly 400 engineered F constructs. Through in vitro and in vivo characterization studies, we identified F constructs that are more stable in the prefusion conformation and elicit ~10-fold higher serum neutralizing titers in cotton rats than DS-Cav1. The stabilizing mutations of the lead construct (847) were introduced onto F glycoprotein backbones of strains representing the dominant circulating genotypes of the two major RSV subgroups, A and B. Immunization of cotton rats with a bivalent vaccine formulation of these antigens conferred complete protection against RSV challenge, with no evidence of disease enhancement. The resulting bivalent RSV prefusion F investigational vaccine has recently been shown to be efficacious against RSV disease in two pivotal phase 3 efficacy trials, one for passive protection of infants by immunization of pregnant women and the second for active protection of older adults by direct immunization.

All Eyes on the Prefusion-Stabilized F Construct, but Are We Missing the Potential of Alternative Targets for Respiratory Syncytial Virus Vaccine Design?

“…In this construct, three mutations were introduced, namely a disulfide bridge (T103C-I148C), cavity filling (S190I) using non-polar amino acids and a charge neutralization mutation (D486S), to reduce ionic repulsion or enhance ionic attraction between residues that are proximate to each other at the trimer interface in the prefusion conformation. Construct 847 was most able to elicit consistently high nAb titers in mice and cotton rats, approximately 50 times higher than immunization with postfusion F [ 104 ]. Pfizer created a bivalent prefusion vaccine (RSVpreF) starting from construct 847, composed of equal amounts of recombinant RSV prefusion F derived from circulating A and B strains and without the use of an adjuvant [ 104 , 105 ].…”

Design of hepadnavirus core protein-based chimeric virus-like particles carrying epitopes from respiratory syncytial virus

“…Recently, two vaccines, i.e., Arexvy made by GSK and Abrysvo by Pfizer, were approved by the U.S. Food and Drug Administration (FDA) to protect against RSV. Both vaccines used the RSV F protein stabilized in its prefusion conformation as the antigen 11 , 46 . Our study adopted another strategy for possible RSV vaccine design, in which the potent neutralizing epitopes derived from RSV F protein were grafted onto the surface of the virus-like particle (VLP) formed by the hepadnavirus core proteins.…”

Antigen spacing on protein nanoparticles influences antibody responses to vaccination

“…Our strategy was similar to those used to stabilize HA stem and coronavirus Spike S2 antigens by deleting undesired domains and then repairing the resulting conformational changes or instabilities with stabilizing mutations or topological rearrangements (Yassine et al 2015;Corbett et al 2019;Impagliazzo et al 2015;Hsieh et al 2021;Bowen et al 2022). We focused on restoring the native-like closed trimeric arrangement of the displayed RBDs by strengthening the interactions between protomers, an approach that has been used to stabilize other oligomeric antigens in native-like conformations (Impagliazzo et al 2015;Ellis et al 2022;Milder et al 2022;Joyce et al 2016;Che et al 2023;Stewart-Jones et al 2021;Hsieh et al 2022;Chuang et al 2017;de Taeye et al 2015;Rutten et al 2018). Trimer closure required both computationally designed hydrophobic interactions at the trimer interface and a rigid, disulfide-mediated connection to an underlying trimerization domain.…”