[CpG-ODN is a potential candidate adjuvant for human vaccines]

To evaluate the adjuvanticity of CpG-ODN for human vaccines in animal models.

To find suitable animal models, the human CpG-ODN were examined for their in vitro immunostimulatory activities for murine and Rhesus monkey immune cells. Then by using recombinant HBsAg as a model antigen, the adjuvanticity of human CpG-ODN was evaluated in the animal models.

Rhesus monkey B cells responded well to all the human CpG-ODN, similarly as that of human B cells. In contrast, only the human CpG-ODN with the CpG motif 5'GTCGTT 3' (CpG2006 etc) could induce murine splenocytes to secret IgM and IFN-gamma, while those with the CpG motif 5'GTCGTC 3' (CpGT7 etc) had less or no effects. The results suggested that Rhesus monkeys and mice could be used as animal models to evaluate the in vivo activities of different human CpG-ODN. Immunized with HBsAg combined with various human CpG-ODN, the mice elicited a stronger Th1 humoral immunity. Consistent with the in vitro findings, CpG-ODN with the CpG motif 5'GTCGTT 3' were more potent than those with the CpG motif 5'GTCGTC 3'. But of note, all the sequences had the same ability for modulation of Th1/Th2 immune response, with the ratio of IgG2a/IgG1 around 1. However, human CpG-ODN had less adjuvanticity for HBsAg in Rhesus monkeys; only CpGT7 increased the antibody titers by 2 times, while CpG2006 had no effect.

The preliminary results derived from animal models showed that CpG-ODN was a potential candidate Th1 adjuvant for human vaccines.