Increased resistance against acute polymicrobial sepsis in mice challenged with immunostimulatory CpG oligodeoxynucleotides is related to an enhanced innate effector cell response

Recent reports support the concept that the major defect in polymicrobial sepsis is an impaired immunologic response to infection. Oligodeoxynucleotides containing CpG sequence motifs (CpG-ODN) were previously shown to induce immune protection in models of chronic infection with intracellular bacteria, parasites, and viruses due to their ability to augment IFN-gamma-dependent Th1 responses. Here, we demonstrate that challenging mice with CpG-ODN substantially increases the resistance against acute polymicrobial sepsis. Systemic levels of IL-12, IL-18, and IL-10 were not altered in CpG-ODN-treated mice as compared with controls. In contrast, administration of CpG-ODN resulted in a strongly enhanced accumulation of neutrophils at the primary site of infection. Neutrophils of CpG-ODN-treated mice exhibited an up-regulation of phagocytic receptors, an increased phagocytic activity, and an elevated production of reactive oxygen metabolites. These results suggest that the protective effects of CpG-ODNs in acute polymicrobial sepsis are related to an enhanced effector cell response of innate immunity. CpG-ODN may therefore represent potent agents for the treatment of sepsis-associated immunoparalysis.