Longevity of the serological response following a single vaccination with monomeric F1 and polymeric F1 either alone or with LcrV. (A) Anti-F1 IgG titers measured in the sera of CD-1 female mice 180 days post a single vaccination with polymeric F1 (pF1, 80 µg/mouse), polymeric F1 + LcrV (pF1 + V, 80 µg each/mouse), monomeric F1 (mF1, 80 µg/mouse), and monomeric F1 + LcrV (mF1 + V, 80 µg each/mouse). (B) Anti-LcrV IgG titers that were measured in the sera of the mice as described in (A). The dashed horizontal line marks the limit of detection. n.s. = nonsignificant, * = p < 0.05, *** = p < 0.001.