Effect of CpG Oligonucleotides on Vaccine-Induced B Cell Memory

Adding synthetic oligodeoxynucleotides containing unmethylated CpG motifs to Anthrax vaccine adsorbed (AVA, the licensed human vaccine) increases the speed and magnitude of the resultant Ab response. Ab titers persist in the protective range for >1 year, significantly longer than in animals vaccinated with AVA alone. Unexpectedly, a majority of mice immunized with CpG-adjuvanted AVA maintained resistance to anthrax infection even after their Ab titers had declined into the subprotective range. The survival of these animals was mediated by the de novo production of protective Abs by high affinity memory B cells re-stimulated immediately after challenge. Thus, a previously unrecognized benefit of CpG oligodeoxynucleotides adjuvants is their ability to expand the long-lived memory B cell population. Current findings demonstrate that CpG-adjuvanted AVA mediates protection both by stimulating a strong/persistent serum Ab response and by generating a high-affinity long-lived pool of memory B cells.