Fig. 3: Preclinical evaluation of vaccine integrity (ChAd155-RSV) after two years of storage at 5 °C.

The evaluation of vaccine integrity (ChAd155-RSV; 1 × 10⁸ particles) after two years of storage at 5 °C (T24) was performed in comparison to the vaccine immediately after lyophilisation (T0), frozen at −80 °C and, in comparison to a formaldehyde-inactivated respiratory syncytial virus (RSV) vaccine (FI-RSV) and challenge RSV (RSVA2). Evaluations were performed in the RSV-challenge model in mice, where mice were vaccinated on Day 0 and 21 and challenged on Day 35 with RSVA2. (a) Viral load in the lung tissue at Day 40; (b) RSV-neutralizing titres on Day 35 and Day 40 (by effective dilution for 50% neutralization [ED50]) where each dot-plot corresponds to individual animals and the horizontal line represents the geometric mean for each group with the 95% confidence intervals; (c) RSV-specific IFN-γ-ELISpots from stimulated splenocytes harvested at Day 40 where each dot-plot corresponds to individual animals and the horizontal line represents the mean for each group with the standard deviation. (d) Pathology analysis of the lung tissue at Day 40, based on eosinophil staining (left graph) and mucus-producing goblet-cell induction (periodic acid Schiff [PAS] staining of basement membrane [BM], right graph) where each dot-plot corresponds to individual animals and the horizontal line represents the mean for each group with the standard deviation. Six mice per group were used in the analysis of vaccine effectiveness (a and d), and five mice per group were used in the analysis of immunogenicity (b and c).