🤧 RSV Vaccine Mechanism Simulator

Stabilized Prefusion F-Protein as Vaccine Antigen

The vaccine delivers a locked prefusion shape of the RSV fusion protein.

• Arexvy/Abrysvo: Vaccines (approved 2023)
• Prefusion F: Antigen form (engineered stable)
• Recombinant: Platform (protein subunit)
• F-protein: Target (fusion machinery)

Why prefusion shape matters

Locking F-protein pre-fusion exposes better neutralizing epitopes.

Antigen-Presenting Cells Detect the Antigen

Dendritic cells capture antigen and present it to helper T cells.

• Dendritic: Cell type (antigen-presenting)
• MHC-II: Signal (presentation pathway)
• T-helper: Response (activation)
• Days 1-3: Timeframe (post-injection)

From antigen to activation

Recognition triggers downstream B-cell help signals.

B Cells Differentiate into Antibody-Secreting Plasma Cells

Activated B cells expand and mature into plasma cells over weeks.

• ~Week 4: Peak titer (post-vaccination)
• IgG: Antibody type (neutralizing)
• Plasma cells: Cell source (bone marrow, lymph)
• B cells: Memory (long-term)

Titer rise over time

Antibody levels climb quickly then plateau and slowly decline.

Circulating Antibodies Bind RSV F-Protein Spikes

Neutralizing antibodies attach directly to F-protein on virions.

• Site Ø/V: Binding site (prefusion epitopes)
• Neutralization: Effect (blocks infectivity)
• Microneutralization: Assay (titer measured)
• RSV-A/B: Coverage (both subtypes)

Antibody-virion binding

Bound antibodies coat spikes, tagging virions as neutralized.

Fusion Blockade Prevents Host Cell Entry

Antibody-coated F-protein cannot trigger membrane fusion into cells.

• ~82%: Efficacy older adults (severe disease)
• ~82%: Efficacy maternal (infant protection)
• Fusion block: Mechanism (entry prevented)
• Reduced LRTD: Outcome (lower respiratory disease)

End result of protection

Virus is neutralized before it can fuse and infect cells.

Placeholder: durability declines gradually after peak response.