Modulation of Gene Expression Related to Toll-Like Receptor Signaling in Dendritic Cells by Poly(-Glutamic Acid) Nanoparticles

Poly(-glutamic acid) (-PGA) nanoparticles (NPs) have previously been reported as an efficient antigen delivery system with adjuvant activity. In this study, the gene expression in murine bone marrow-derived dendritic cells (DCs) treated with -PGA NPs was examined by oligonucleotide microarray analysis and compared with that in cells treated with other adjuvants. The gene expression of proinflammatory chemokines, cytokines, and costimulatory molecules was upregulated considerably in DCs treated with -PGA NPs. The upregulation pattern was similar to that in DCs treated with lipopolysaccharide (LPS) but not to that in DCs treated with unparticulate -PGA. The activation of DCs by -PGA NPs was confirmed by real-time reverse transcriptase PCR (RT-PCR) analysis of genes related to Toll-like receptor (TLR) signaling. The effect of -PGA NPs on DCs was not annihilated by treatment with polymyxin B, an inhibitor of LPS. Furthermore, the immunization of mice with -PGA NPs carrying ovalbumin (OVA) as an antigen significantly induced antigen-specific CD8 T cells and antigen-specific production of interleukin-2, tumor necrosis factor alpha, and gamma interferon from the cells. Such activities of -PGA NPs were more potent than those obtained with immunization with OVA plus aluminum hydroxide or OVA plus complete Freund’s adjuvant. These results suggest that -PGA NPs induce a CD8 T-cell response by activating innate immunity in a fashion different from that of LPS. Thus, -PGA NPs may be an attractive candidate to be developed further as a vaccin