TLR9 agonist is potent innate immune booster. As a prototype, synthetic oligodeoxynucleotides (ODN) holding unmethylated deoxycytosine-deoxyguanosine (CpG) motifs has been entered immunotherapeutic clinical trial against infection (i.e, hepatitis B, C), tumor or asthma. Toward optimal tailoring for treatment of these incurable diseases, the designing of CpG ODN with new functional properties is essential. Currently three (A, B, C) classes of TLR9 agonists have been described: The recently emerged C-Class ODN is the hybrid pros between A- and B-Class ODN in that they induce strong B-cell activation comparable to B-Class ODN together with IFN-alpha secretion comparable to A-Class ODN. In this study, we investigated in vitro cytokine profile and signaling cascade from the activation of mitogen-activated protein kinases (MAPKs), such as p38, c-Jun NH2-terminal kinase (JNK), extracellular receptor kinase (ERK) to NF-κB activation as well as in vivo tumor protection in mice using new C-class CpG. In brief, new C-Class CpG motif immunomer induced cellular proliferation and higher interleukin (IL)-6, IL-12 secretion in murine splenocytes. New immunomer evoked the activation of MAPKs in cell lines (U937, RAW264.7, and EL4) by differential manner, consequently leading to activate transcription factor NF-κB via degradation of IκBα in the corresponding cell lines. More importantly, new C-class CpG immunomer exerted significant protection in C57BL6 mice challenged with B16BL6 melanoma and EL4 T cell lymphoma. Given these activities profiling, new C-Class CpG is strong Th1 booster with the stimulation of IL-12 secretion as well as strong NK activation. Now, further studies on these mechanisms via structural modification of CpG DNA are underway.
[Proc Amer Assoc Cancer Res, Volume 46, 2005]