Adjuvant synergy in the response to hepatitis B vaccines

Abstract

The adjuvant properties of interleukin-12 (IL-12) and a phosphorothioate oligodeoxynucleotide (S-ODN) hexamer consisting of the sequence, 5′-GACGTT-3′, were evaluated in mice using hepatitis B (HBs) protein and DNA vaccines. GACGTT was an effective adjuvant when co-injected with HBs protein intramuscularly or when injected at the same anatomic site within 1 day before or 1 day after injection of the protein. Surprisingly, IL-12 had a negligible adjuvant effect when co-injected with HBsAg; however, when bound to “alum”, IL-12 stimulated a dramatic increase in anti-HBs titers and a switch from a TH2 to a TH1 response profile as evidenced by an increase in IgG2a subclass anti-HBs antibodies and the ability to secrete interferon-γ (IFN-γ) upon in vitro stimulation with an HBs peptide. Interestingly, aluminum phosphate was a far better co-adjuvant (with IL-12) than was aluminum hydroxide even though both “alums” bound >99% of the IL-12. Finally, the combination of IL-12, GACGTT, and aluminum phosphate was found to elicit a markedly polarized TH1 response. The results indicate that aluminum phosphate is highly effective at delivering an antigen (HBsAg) together with TH1 adjuvants such as IL-12 and GACGTT resulting in a shift from a TH2 to a TH1 response.