Toll-Like Receptor 9-Dependent Activation of Bone Marrow-Derived Dendritic Cells by URA5 DNA from Cryptococcus neoformans

作者：Tanaka Misuzu; Ishii Keiko; Nakamura Yuri; Miyazato Akiko; Maki Atsuko; Abe Yuzuru; Miyasaka Tomomitsu; Yamamoto Hideki; Akahori Yukiko; Fue Misaki; Takahashi Yurie; Kanno Emi; Maruyama Ryoko; Kawakami Kazuyoshi^*

来源：Infection and Immunity, 2012, 80(2): 778-786.

DOI：10.1128/IAI.05570-11

Cryptococcus neoformans is an opportunistic fungal pathogen that causes meningoencephalitis in immunocompromised patients. Recently, we reported that Toll-like receptor 9 (TLR9) is involved in host defense against C. neoformans: specifically, it detects the pathogen%26apos;s DNA. In the present study, we aimed to elucidate the mechanisms underlying TLR9-mediated activation of innate immune responses by using the URA5 gene, which encodes a virulent component of this fungal pathogen. A PCR-amplified 345-bp URA5 gene fragment induced interleukin-12 p40 (IL-12p40) production by bone marrow-derived dendritic cells (BM-DCs) in a TLR9-dependent manner. Similar activity was detected in the 5%26apos; 129-bp DNA fragment of URA5 and in a synthesized oligodeoxynucleotide (ODN) with the same sequence. Shorter ODN fragments, which contained GTCGGT or GAC-GAT but had only 24 or 21 bases, induced IL-12p40 production and CD40 expression by BM-DCs, but this activity vanished when the CG sequence was replaced by GC or when a phosphorothioate modification was introduced. IL-12p40 production caused by active ODN was strikingly enhanced by treatment with DOTAP, a cationic lipid that increases the uptake of DNA by BM-DCs, though DOTAP failed to induce IL-12p40 production by inactive ODN and did not affect the activity of an ODN-containing canonical CpG motif. There was no apparent difference in intracellular trafficking between active and inactive ODNs. Finally, an extremely high dose of inactive ODN suppressed IL-12p40 production by BM-DCs that had been stimulated with active ODN. These results suggest that the C. neofortnans URA5 gene activates BM-DCs through a TLR9-mediated signaling pathway, using a mechanism possibly independent of the canonical CpG motif.

• 出版日期2012-2