Fig. 6.

Rapid anti-plague immunity is induced by polymeric, but not monomeric, F1. Anti-F1 IgM a, Anti-F1 IgG b, Anti-F1 IgG1 c, and anti-F1 IgG3 d titers in the sera of C57BL/6J mice vaccinated with polymeric (20 μg/mouse, blue circles) or monomeric (20 μg/mouse, red squares) F1 at the indicated day post vaccination (n = 4 for all time points in both groups). Horizontal dashed line indicates the limit of detection. Short horizontal lines mark the GMTs ( ± 95% CI). (*P < 0.05, ***P < 0.001, ns = nonsignificant). e Survival rates of C57BL/6J mice vaccinated with polymeric (blue line; n = 8) or monomeric (red line; n = 8) F1 or with alum (black dashed line; n = 8) three days prior to a lethal challenge with Y. pestis Kim53. Green line marks the survival rates of mice similarly vaccinated with monomeric F1 and challenged 14 days afterwards