biostudies-literatureUnknown9(12)Bakkers MJGRespiratory syncytial virus (RSV) is a major cause of severe respiratory disease in infants and older people. Current RSV subunit vaccines are based on a fusion protein that is stabilized in the prefusion conformation and linked to a heterologous foldon trimerization domain to obtain a prefusion F (preF) trimer. Here we show that current RSV vaccines induce undesirable anti-foldon antibodies in non-human primates, mice and humans. To overcome this, we designed a foldon-free RSV preF trimer by elucidating the structural basis of trimerization-induced preF destabilization through molecular dynamics simulations and by introducing amino acid substitutions that negate hotspots of charge repulsion. The highly stable prefusion conformation was validated using antigenic and cryo-electron microscopNature microbiology3254-3267https://www.ebi.ac.uk/biostudies/studies/S-EPMC11602707biostudies-literatureA foldon-free prefusion F trimer vaccine for respiratory syncytial virus to reduce off-target immune responses.PMC11602707van der Fits LLe LVaneman JThoma AZahn Rvan Overveld DTettero LKoornneef ABakkers MJGCox FJuraszek Jvan den Hoogen WLangedijk JPMVoorzaat RYu XfalseA foldon-free prefusion F trimer vaccine for respiratory syncytial virus to reduce off-target immune responses.Respiratory syncytial virus (RSV) is a major cause of severe respiratory disease in infants and older people. Current RSV subunit vaccines are based on a fusion protein that is stabilized in the prefusion conformation and linked to a heterologous foldon trimerization domain to obtain a prefusion F (preF) trimer. Here we show that current RSV vaccines induce undesirable anti-foldon antibodies in non-human primates, mice and humans. To overcome this, we designed a foldon-free RSV preF trimer by elucidating the structural basis of trimerization-induced preF destabilization through molecular dynamics simulations and by introducing amino acid substitutions that negate hotspots of charge repulsion. The highly stable prefusion conformation was validated using antigenic and cryo-electron microscop2024-01-01T00:00:00Z2024 Dec2026-06-02T06:24:44.577Z2025-04-04T09:59:09.838ZS-EPMC116027073956766410.1038/s41564-024-01860-1