Figure 2

Humoral responses following XBB.1.5 booster in mice. (a) Pseudovirus neutralization titers were determined in mouse sera collected one week after a primary series with bivalent Prototype rS + BA.5 rS (left graph series), and following a boost with monovalent XBB.1.5 (middle graph series) or XBB.1.16 (right graph series) vaccines (sera collected two weeks after booster dose). Note that all immunizations were administered with 5 µg Matrix-M adjuvant. Open circles represent individual data points, solid bars represent group geometric mean titers, error bars represent 95% confidence intervals, and the horizontal dashed line represents the assay limit of detection (LOD). Statistically significant differences between the two booster groups are marked with asterisks: *P < 0.05. Pooled sera were analyzed for Day 21 data where indicated with an asterisk on the x-axis label. (b) Pseudovirus neutralizing titers presented in (a) were subjected to antigenic cartography analysis. Each small square corresponds to one animal and each grid square corresponds to one antigenic distance of twofold change in neutralization titer with fold differences given below each map. Smaller antigenic distance fold-change between two variants indicates higher cross-neutralizing antibody titers.