Enhancing Anti-G Antibody Induction by a Live Single-Cycle Prefusion F-Expressing RSV Vaccine Improves In Vitro and In Vivo Efficacy

The human respiratory syncytial virus (RSV) is a major cause of severe respiratory tract disease, and a vaccine is not available. We previously reported a novel live vaccine expressing prefusion-stabilized fusion protein (preF) in place of the native F protein (RSV-preF(Delta CT)). As preF is non-functional, RSV-preF(Delta CT) was amplified in a production line expressing a functional substitute, and exhibited a single-cycle replication phenotype, which holds several unique potential advantages. RSV-preF(Delta CT) prevented shedding and lung pathology after viral challenge in mice, but induced low levels of anti-attachment protein (G) antibodies (Abs). Given the significant contributions of anti-G Abs toward disease prevention, we generated modifications to RSV-preF(Delta CT) in an effort to induce higher anti-G Ab levels. The Ab levels were monitored after the prime-boost vaccination of mice with modified vaccines. The most successful modification for enhancing induced anti-G Abs was seen with the placement of G in the first genome position. This vaccine also reduced the pathology after challenge with a high dose of wt RSV, and outperformed the sera from wt RSV-vaccinated mice in in vitro neutralization. Thus, raising the anti-G Ab levels induced by RSV-preF(Delta CT) enhanced efficacy in vitro and in vivo, and constitutes an important next step in developing a live, single-cycle, efficacious vaccine for the human population.

Automated summary

The study utilized a novel vaccine to enhance the induction of anti-G antibodies against RSV, resulting in improved protection in mice experiments.