CpG-DNA stimulates cellular and humoral immunity and promotes Th1 differentiation in aged BALB/c mice

We examined whether CpG-DNA could be used as adjuvant to induce a T helper cell type-1 (Th1) immunity in aged BALB/c mice that showed a Th2 polarization. Bordetella pertussis and complete Freund's adjuvant (CFA) were used as well. Immunization with ovalbumin (OVA)/CpG-DNA showed that the immunoglobulin G (IgG)2a/IgG1 ratio and OVA-specific T cell response were similar in young and aged mice. OVA/CpG-DNA induced the secretion of interferon-gamma (IFN-gamma) and absence of interleukin (IL)-5. Similar results were found in mice immunized with OVA/CFA. When mice were immunized with OVA/B. pertussis, we found that the IgG2a/IgG1 ratio and OVA-specific T cell response were lower in aged mice and elicited IFN-gamma and IL-5. In vitro CpG-DNA stimulated antigen-presenting cells to display IL-12 and up-regulate the expression of major histocompatibility complex class II and B7-2 on B cells as efficiently in aged as in young mice, but the up-regulation of B7-1 was stronger in aged mice. The findings demonstrate that CpG-DNA is able to induce a young-like Th1 specific immune response in aged mice.