The plain and CpG-adjuvanted PS3 vaccines generate a persistent pool of BM plasma cells. Ten-week-old mice received a single injection of PS3 followed or not by CpG1668 injection 2 days later or were immunized twice with PS3TT with a 28-day interval. (A-B) Sera from 5 mice in each group were collected at different time points after primary immunization (PS3 and CpG-adjuvanted PS3) or secondary immunization (PS3TT), and IgM (A) and IgG (B) titers were determined by ELISA. (C-D) Numbers of PS3-specific IgM (C) and IgG (D) ASCs in the spleen. Spleens from 5 mice in each group were collected at the indicated time points after primary immunization (PS3 and CpG-adjuvanted PS3) or secondary immunization (PS3TT), and ASC numbers were determined by ELISPOT. (E-F) Numbers of PS3-specific IgM (E) and IgG (F) ASCs in the BM. ASC numbers were determined as in panels C and D. Results are expressed as means ± SEM of the values collected in 5 individual mice.