NFκB- and MAP-Kinase Signaling Contribute to the Activation of Murine Myeloid Dendritic Cells by a Flagellin A:Allergen Fusion Protein.

ABSTRACT

Fusion proteins incorporating the TLR5-ligand flagellin are currently undergoing clinical trials as vaccine candidates for many diseases. We recently reported a flagellinallergen fusion protein containing the TLR5-ligand flagellin A (FlaA) from Listeriamonocytogenes and the major birch pollen allergen Bet v 1 (rFlaABetv1) to prevent allergic sensitization in an experimental mouse model. This study analyzes the signaling pathways contributing to rFlaABetv1-mediated pro- and anti-inflammatory cytokine secretion and cell metabolism in myeloid dendritic cells (mDCs) in vitro. The influence of mammalian target of rapamycin (mTOR)-, NF?B-, and MAP kinase (MAPK)-signaling on cytokine secretion and metabolic activity of bone marrow (BM)-derived mDCs stimulated with rFlaABetv1 were investigated by pre-treatment with either mTOR- (rapamycin), NF?B- (dexamethason, BMS-345541, TPCA-1, triptolide, or BAY-11) or MAPK- (SP600125, U0126, or SB202190) inhibitors, respectively. rFlaABetv1-mediated IL-10 secretion as well as activation of mDC metabolism, rather than pro-inflammatory cytokine secretion, were inhibited by rapamycin. Inhibition of NFκB-signaling suppressed rFlaABetv1-induced IL-12, while inhibition of MAPK-signaling dose-dependently suppressed rFlaABetv1-induced IL-10 as well as pro-inflammatory IL-6 and TNF-α production. Notably, with the exception of a partial JNK-dependency, rFlaABetv1-mediated effects on mDC metabolism were mostly NF?B- and MAPK-independent. Therefore, MAPK-mediated activation of both NFκB- and mTOR-signaling likely is a key pathway for the production of pro- and anti-inflammatory cytokines by flagellin fusion protein vaccines.