Researchers engineered a stable version of the RSV F glycoprotein to maintain antigenic site Ø, which is targeted by potent RSV-neutralizing antibodies. This site is crucial for eliciting strong neutralizing immune responses. By stabilizing the prefusion conformation of RSV F, the study demonstrated that variants of RSV F with stabilized site Ø elicited significantly higher neutralizing titers in mice and non-human primates compared to postfusion forms. These variants retained antigenic site Ø even under extreme conditions, showing enhanced stability and immunogenicity. Structural analysis revealed that mutations such as S190F-V207L and D486H-E487Q-F488W-D489H improved the stability and conformation of RSV F, preserving the prefusion state. The DS-Cav1-TriC variant showed the best balance of stability and immunogenicity, leading to high neutralizing titers. The study highlights the importance of structure-based design in vaccine development, emphasizing the role of antigenic site Ø in eliciting protective immunity against RSV. The findings suggest that targeting this site could lead to more effective vaccines against RSV.Researchers engineered a stable version of the RSV F glycoprotein to maintain antigenic site Ø, which is targeted by potent RSV-neutralizing antibodies. This site is crucial for eliciting strong neutralizing immune responses. By stabilizing the prefusion conformation of RSV F, the study demonstrated that variants of RSV F with stabilized site Ø elicited significantly higher neutralizing titers in mice and non-human primates compared to postfusion forms. These variants retained antigenic site Ø even under extreme conditions, showing enhanced stability and immunogenicity. Structural analysis revealed that mutations such as S190F-V207L and D486H-E487Q-F488W-D489H improved the stability and conformation of RSV F, preserving the prefusion state. The DS-Cav1-TriC variant showed the best balance of stability and immunogenicity, leading to high neutralizing titers. The study highlights the importance of structure-based design in vaccine development, emphasizing the role of antigenic site Ø in eliciting protective immunity against RSV. The findings suggest that targeting this site could lead to more effective vaccines against RSV.