A respiratory syncytial virus (RSV) F protein nanoparticle vaccine focuses antibody responses to a conserved neutralization domain

Abstract

A stabilized form of the respiratory syncytial virus (RSV) fusion (F) protein has been explored as a vaccine to prevent viral infection because it presents several potent neutralizing epitopes. Here, we used a structure-based rational design to optimize antigen presentation and focus antibody (Ab) responses to key epitopes on the pre-fusion (pre-F) protein. This protein was fused to ferritin nanoparticles (pre-F-NP) and modified with glycans to mask nonneutralizing or poorly neutralizing epitopes to further focus the Ab response. The multimeric pre-F-NP elicited durable pre-F–specific Abs in nonhuman primates (NHPs) after >150 days and elicited potent neutralizing Ab (NAb) responses in mice and NHPs in vivo, as well as in human cells evaluated in the in vitro MIMIC system. This optimized pre-F-NP stimulated a more potent Ab response than a representative pre-F trimer, DS-Cav1. Collectively, this pre-F vaccine increased the generation of NAbs targeting the desired pre-F conformation, an attribute that facilitates the development of an effective RSV vaccine.

A single immunization with spike-functionalized ferritin vaccines elicits neutralizing antibody responses against SARS-CoV-2 in mice

“…Unlike nanoparticle platforms that require post-purification conjugation of an antigen to a carrier or scaffold, here spike functionalized nanoparticles were produced by transfecting a single plasmid encoding the spike fused to the ferritin subunit into mammalian cells. We built on existing work using ferritin nanoparticles to display other viral antigens for vaccine development (30)(31)(32)(33)(34)(35)(36) and designed nanoparticles displaying the SARS-Cov-2 spike ectodomain. Importantly, the two ferritin-based antigens that we designed (S-Fer and SΔC-Fer) expressed comparably to spike trimers (S-GCN4 and SΔC-GCN4) in mammalian cells ( Figure S1), indicating that fusing the spike to ferritin does not negatively impact protein production.…”

Technological approaches to streamline vaccination schedules, progressing towards single-dose vaccines

“…Nanoparticles have been successfully used to develop HBV and HPV vaccines and can be used as scaffolds to design highly immunogenic multivariant antigens. For example, in the works from Yassine et al and Kanekiyo et al, ferritin, a self-assembling protein nanoparticle with robust thermal and chemical stabilities, has been used as a scaffold to present a multivalent array of influenza virus hemagglutinin (HA) with its native trimeric conformation intact; this structure-based design strategy has led to the development of a potent and broad-coverage influenza vaccine that is now being tested in a phase I clinical trial [60][61][62][63] . In another study from Marcandalli et al a single-immunization with a nanoparticle-based RSV vaccine outperformed the nonnanoparticle formulation in inducing T follicular helper (Tfh) cells and germinal center (GC) B cells 64 , highlighting the value of adopting a strategy of multi-copy antigen display in the designing of next-generation vaccines.…”

Immune response to vaccine candidates based on different types of nanoscaffolded RBD domain of the SARS-CoV-2 spike protein

“…Higher stoichiometries of the assemblies can even more efficiently mask scaffold domains. Ferritin forms a 24-meric cage and has been frequently used for the presentation of polypeptide antigens as it can present 8 trimers on each particle 38,65,39 . However, the density of RBD domains at its surface is, according to the molecular model, lower than for the other designed assemblies (Fig.…”

“…4). Several scaffolds for protein oligomerization with well-defined structure have been used for vaccines against different antigens, including many from viruses 31,38,39,46,65,76 .…”

“…Presentation of the target antigen domain in the multimeric form may be accomplished by chemical conjugation of a viral protein domain to the nanoparticle or by a genetic fusion to the scaffold-forming polypeptide domain. Examples of the attachment of immunogenic domains to the virus-like capsule are capsid proteins of bacterial, plant or animal viruses such as Q, HPV, JCV, HBcAg, cowpea chlorotic mottle virus capsids 35 and many others, nonviral protein compartments such as ferritin, lumazine synthase and encapsulin 31,[36][37][38][39] and de novo designed protein or DNA cages [40][41][42][43][44][45][46] .…”