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Screening Bioactive Nanoparticles in Phagocytic Immune Cells for Inhibitors of Toll-like Receptor Signaling
Published on: July 26, 2017
Enhanced immunostimulatory activity of in silico discovered agonists of Toll-like receptor 2 (TLR2)
M S Murgueitio1, S Ebner2, P Hörtnagl3
1Pharmaceutical Chemistry, Institute of Pharmacy, Freie Universität Berlin, Königin-Luise Str. 2-4, 14195 Berlin, Germany.
Background:
Emergent therapies in anticancer vaccination use Toll-like receptors (TLRs) agonists as dendritic cell (DC) vaccine adjuvants. DCs from the patient are isolated, stimulated with TLR agonists and tumor antigens ex vivo and then infused back into the patient. Although some TLR ligands have been tested in clinical trials, novel TLR agonists with improved immunomodulatory properties are essential to optimize treatment success. We report on the discovery of small-molecule TLR2 agonists, with favorable properties as synthetic adjuvants.
Methods:
We performed a shape- and featured-based similarity virtual screening against a commercially available compound library. The selected virtual hits were experimentally tested in TLR2-reporter cells and their activity in phagocytes and DCs was characterized. A binding model of the compounds to TLR2 (docking studies) was proposed.
Results:
Through a virtual screening approach against a library of three million compounds four virtual hits (AG1, AG2, AG3, AG4) were found to synergistically augment the NF-kB activation induced by the lipopeptide ligand Pam3CSK4 in luciferase reporter assays using HEK293-TLR2 cells. Biacore experiments indicated that AG1-AG4 are ago-allosteric modulators of TLR2 and AG2 bound TLR2 with high affinity (KD 0.8μM). The compounds induced TNF-α production in human peripheral blood mononuclear cells (PBMCs) and they activated DCs as indicated by IL-12 production and upregulation of CD83/CD86.
Conclusions:
Following a combined in silico/in vitro approach we have discovered TLR2-agonists (AG1-AG4) that activate human and mouse immune cells.
General Significance:
We introduce four novel TLR2 ago-allosteric modulators that stimulate myeloid cell activity and constitute promising candidates as synthetic adjuvants.
Insights
Researchers discovered novel small-molecule Toll-like receptor 2 (TLR2) agonists. These compounds show promise as synthetic adjuvants to enhance anticancer vaccine efficacy by activating immune cells.
Area of Science:
- Immunology
- Pharmacology
Background:
- Anticancer vaccines increasingly use Toll-like receptors (TLRs) agonists as dendritic cell (DC) vaccine adjuvants.
- Current TLR agonists have limitations, necessitating novel compounds with enhanced immunomodulatory properties for improved treatment outcomes.
- The development of effective synthetic adjuvants is crucial for optimizing cancer immunotherapy.
Purpose of the Study:
- To discover and characterize novel small-molecule TLR2 agonists with potential as synthetic adjuvants for cancer vaccines.
- To evaluate the immunomodulatory properties of newly identified TLR2 agonists in preclinical models.
Main Methods:
- Utilized shape- and featured-based similarity virtual screening against a large compound library.
- Experimentally validated virtual hits using TLR2-reporter cells, phagocytes, and DCs.
- Performed docking studies to propose binding models of compounds to TLR2.
Main Results:
- Identified four virtual hits (AG1-AG4) that synergistically enhance NF-kB activation in HEK293-TLR2 cells.
- AG1-AG4 were confirmed as ago-allosteric modulators of TLR2, with AG2 exhibiting high affinity.
- Compounds induced TNF-α production in PBMCs and activated DCs, evidenced by IL-12 production and CD83/CD86 upregulation.
Conclusions:
- Discovered novel TLR2 agonists (AG1-AG4) using a combined in silico/in vitro approach.
- These agonists activate human and mouse immune cells, demonstrating potential as synthetic adjuvants.
- The identified TLR2 modulators stimulate myeloid cell activity and represent promising candidates for cancer immunotherapy.
