CpG DNA induces stronger immune responses with less toxicity than other adjuvants.

The ability to augment protective immune responses with minimal side effects is quintessential for a good adjuvant. This study has compared various adjuvants that are used in animal research (Freund's complete and incomplete adjuvants, Titermax Gold), are licensed for human use (alum), or are in clinical testing for humans (monophosphoryl lipid, CpG DNA), for their ability to augment humoral responses to a model antigen (hepatitis B surface antigen) and for the degree of damage they caused in the injected muscle. According to the data, the adjuvant combination CpG DNA+alum had the greatest potential to augment immune responses with minimal side effects at the injection site. Evaluation of antibody isotypes indicated Th2 responses (no IgG2a) with all adjuvants except monophosphoryl lipid and CpG DNA, which gave mixed Th1/Th2 responses (IgG1 and IgG2a). Strong Th1 responses (predominantly IgG2a) were obtained with combinations of CpG DNA with other adjuvants.