The role of interleukine-12 in protection induced by CpG ODN against Listeria monocytogenes in BALB/c and C57BL/6

Synthetic oligodeoxynucleotides containing CpG motifs have several immune effects such as cytokine production in normal mice. In this study, we demonstrated the protective effect of CpG ODN against Listeria monocytogenes in BALB/c and C57BL/6. With a single dose of 40 μg/mouse of CpG ODN 48 h before bacterial challenge, protection was achieved in both strains of mice based on survival rates compared with controls. Serum IL-12 from each mouse was measured by using enzyme-linked immunosorbent assay (ELISA), at day 0 (48 h after CpG treatment) and at days 5, 11, and 15 after bacterial challenge. It was shown that serum IL-12 was only elevated at day 0 in BALB/c mice. However, for C57BL/6 mice, IL-12 was elevated at days 0, 5, and 11. These data support the hypothesis that CpG DNA motifs activate protective innate immune defenses.