P31

The mycotoxin Beauvericin exhibits immunostimulatory effects on dendritic cells via activating the TLR4 signaling pathway

YANG X. ¹, ALI S. ¹, RICHTER L. ¹, SCHÄFER V. ¹, SCHLIEHE-DIECKS J. ², FRANK M. ³, LARSEN P. ⁵, SKERRA J. ⁵, ISLAM H. ⁶, WACHTMEISTER T. ⁷, ALTER C. ⁸, BHATIA S. ², KÖHRER K. ⁷, KIRSCHNING C. ⁶, WEIGHARDT H. ⁹, KALINKE U. ^5,10, KALSCHEUER R. ³, UHRBERG M. ⁴, SCHEU S. ¹

¹ Institute of Medical Microbiology and Hospital Hygiene, Heinrich Heine University Düsseldorf, Düsseldorf, Germany; ² Department of Pediatric Oncology, Hematology and Clinical Immunology, Medical Faculty, Heinrich-Heine University Düsseldorf, Düsseldorf, Germany; ³ Institute of Pharmaceutical Biology and Biotechnology, Heinrich Heine University Düsseldorf, Düsseldorf, Germany; ⁴ Institute for Transplantation Diagnostics and Cell Therapeutics, Medical Faculty, Heinrich-Heine University Düsseldorf, Düsseldorf, Germany; ⁵ Institute for Experimental Infection Research, TWINCORE, Centre for Experimental and Clinical Infection Research, a joint venture between the Helmholtz Centre for Infection Research and the Hannover Medical School, Hannover, Germany; ⁶ Institute of Medical Microbiology, University Hospital of Essen, University of Duisburg-Essen, Essen, Germany; ⁷ Biological and Medical Research Center (BMFZ), Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany; ⁸ Institute of Molecular Cardiology, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany; ⁹ Immunology and Environment, Life & Medical Sciences (LIMES) Institute, University of Bonn, Bonn, Germany; ¹⁰ Cluster of Excellence - Resolving Infection Susceptibility (RESIST, EXC 2155), Hannover Medical School, Hannover, Germany

1.Objectives
Our aim is to evaluate the effects of the natural compound Beauvericin on dendritic cells and elucidate the underlying mechanisms.
2.Materials & Methods
GM-CSF-cultured bone marrow derived dendritic cells (BMDCs) were generated from C57BL/6, IL-12p40/GFP-reporter mice, and MyD88^-/-, MyD88/TRIF^-/- and TLR4^-/-mice. Immune activating capacities of Beauvericin on BMDCs and T cell proliferation were detected by flow cytometry. The impact of Beauvericin on cytokine production was measured by ELISA. The effects of Beauvericin on TLR4 signaling was detected by Luciferase reporter assays. Differential gene expression induced by Beauvericin was analyzed by RNA sequencing.
3.Results
We found that the cyclic hexadepsipeptide Beauvericin can activate BMDCs to induce IL-12 and IFNβ production, thereby enhancing Th1 cell differentiation and proliferation. However, IL-12 and IFNβ production are not observed in Beauvericin stimulated MyD88^-/- and MyD88/TRIF^-/-BMDCs. Furthermore, TLR4^-/-BMDCs are not responding to Beauvericin treatment in this way, suggesting Beauvericin activates BMDCs via TLR4 signaling pathways. Consistently, luciferase reporter assays showed that BEA stimulation significantly promotes NF-κB activation in mTLR4/CD14/MD2 overexpressing but not control HEK-293 cells. RNA-sequencing analyses further confirmed that BEA induces transcriptional changes associated with the TLR4 signaling pathway in addition to pathways specific for Beauvericin but not LPS stimulation.
4.Conclusions
Beauvericin can activate BMDCs via the TLR4 signaling pathway, but it induces a gene expression profile different from LPS. Our observations suggest that this compound can be exploited as a promising candidate structure for vaccine adjuvants or cancer immunotherapies.
5.Acknowledgements
This work was funded by the Deutsche Forschungsgemeinschaft (German Research Foundation) DFG-270650915/GRK2158.