RSV Vaccine Candidate Demonstrates Safety but no Increase in RSV-Neutralizing Antibody Titers

The respiratory syncytial virus (RSV) vaccine V-306 was safe and well-tolerated in its first-in-human study, researchers reported in the journal Vaccines. 

“Virometix (Schlieren, Switzerland) developed V-306, a synthetic virus-like particle-based vaccine candidate displaying multiple RSV F site II (FsII) protein mimetics as the antigenic epitope,” wrote corresponding author Lilli Stergiou, PhD, of Virometix, and coauthors in the study background. “The V-306 vaccine isolates a key neutralizing epitope to ‘instruct’ the immune system to respond effectively and in a targeted manner, omitting epitopes that might mask the overall protective response.”

The double-blind, placebo-controlled, dose-escalating study included 60 healthy women between the ages of 18 and 45. Three cohorts received 2 intramuscular administrations of V-306 or placebo at doses of either 15 µg, 50 µg, or 150 µg on days 0 and 56. Within each cohort, 15 women received the vaccine and 5 received placebo.

According to the study findings, the 50-µg and 150-µg doses of the vaccine induced an increase in immunoglobulin G (IgG), specific of FsII protein mimetics, from 28 days after the first injection that lasted at least 4 months after the second injection.

“This did not translate into an increase in RSV-neutralizing antibody titers, which were already high at baseline,” researchers reported. “No increase in the anti-F protein-specific IgG titers was observed, which were also high in most subjects at baseline due to past natural infections.”

At all dose levels, V-306 was safe and well tolerated, the study showed. No serious adverse events or vaccine-associated enhanced respiratory disease occurred.

“In conclusion,” researchers wrote, “several future modifications of the vaccine, as well as refinements to the study population and assay conditions, will likely improve the results of vaccination.”

Reference:
Leroux-Roels I, Bruhwyler J, Stergiou L, et al. Double-blind, placebo-controlled, dose-escalating study evaluating the safety and immunogenicity of an epitope-specific chemically defined nanoparticle RSV vaccine. Vaccines. 2023;11(2):367. doi:10.3390/vaccines11020367