Bacillus anthracis capsule promotes TNF-α expression and NF-kB activation through activation of TLR2 in phorbol 12-myristate 13-acetate-differentiated THP-1 and human monocyte-derived dendritic cells (111.14)

Abstract

Abstract Anthrax is a highly lethal infectious disease caused by the spore-forming Bacillus anthracis. Poly-γ-D-glutamic acid (PGA) capsule is one of the major virulence factors of B. anthracis. Recently, efforts have been made to include PGA as a component of anthrax vaccine; however, the innate immune response of PGA itself has been poorly investigated. In this study, we characterized the innate immune response elicited by PGA in the human monocytic cell line THP-1, which was differentiated into macrophages with phorbol 12-myristate 13-acetate (PMA) and human monocyte-derived dendritic cells (hMoDCs). The treatment of PGA on differentiated THP-1 cells and hMoDCs leads to the specific extracellular release of TNF-alfa in dose-dependent manner as shown by ELISA. Subsequently ELISA results were validated by microarray analysis and RT-PCR. In addition, the increase of TNF-alfa production was inhibited by TLR2-blocking antibody, TL2.1, indicating the enhancement of cytokine productions is TLR2-dependent. Also, we confirmed that PGA-induced TNF-alfa production occurs via activation of transcription factors nuclear factor (NF)-kB through RT-PCR and phosphorylation of IkB by Western blot analysis. These data indicate that PGA of B. anthracis elicite TNF-alfa production through TLR2 pathway via NF-kB activation in PMA-differentiated THP-1 cells and hMoDCs.