Enhancement of immunomodulatory activity by liposome-encapsulated natural phosphodiester bond CpG-DNA in a human B cell line

Abstract

Natural phosphodiester bond CpG-DNA that contains immunomodulatory CpG motifs (PO-DNA) upregulates the expression of proinflammatory cytokines and induces an Ag-driv-en Th1 response in a CG sequence-dependent manner in mice. In humans, only phosphorothioate backbone-modified CpG-DNA (PS-DNA) and not PO-DNA has immunomodulatory activity. In this study, we found that liposome-encapsulated PO-DNA upregulated the expression of human β-defensin-2 (hBD-2) and major histocompatibility class II molecules (HLA-DRA) in a CG sequence-dependent and liposome dependent manner in human B cells. Of the three different liposomes, DOTAP has the unique ability to enhance the im-munomodulatory activity of PO-DNA. In contrast, HLA-DRA and hBD-2 promoter activation can be induced by liposome encapsulated PS-DNA in a CG sequence-independent manner, depending on the CpG-DNA species. Our observations dem-onstrate that, when encapsulated with a proper liposome in the immune system, natural PO-DNA has the potential to be a useful therapy for the regulation of the innate immune response.