A novel vaccine adjuvant comprised of a synthetic innate defence regulator peptide and CpG oligonucleotide links innate and adaptive immunity.

There has been an increased demand for the development of novel vaccine adjuvants that lead to enhanced induction of protection from infectious challenges and development of immunological memory. A novel vaccine adjuvant was developed comprising a complex containing CpG oligonucleotide and the synthetic cationic innate defence regulator peptide HH2 that has enhanced immune modulating activities. The complex of HH2 and the CpG oligonucleotide 10101 was a potent inducer of cytokine/chemokine expression ex vivo, retained activity following extended storage, had low associated cytotoxicity, and upregulated surface marker expression in dendritic cells, a critical activity for a vaccine adjuvant. Immunization of mice with a coformulation of the HH2-CpG complex and pertussis toxoid significantly enhanced the induction of toxoid-specific antibody titres when compared to toxoid alone, inducing high titres of IgG1 and IgG2a, typical of a balanced Th1/Th2 response, and also led to high IgA titres. This study demonstrates the potential application of the HH2-CpG complex as a vaccine adjuvant.