Design and assessment of dimeric trehalose glycolipids as a strategy to enhance Mincle-mediated vaccine adjuvanticity

Abstract

It has been suggested that the clustering of the macrophage inducible C-type lectin (Mincle), either with itself or with the related macrophage C-type lectin (MCL), can lead to improved Mincle-mediated signalling and adjuvant activity. To this end, we synthesised dimeric ligands that contained Mincle agonists trehalose dibehenate (TDB) or C18-brartemicin (C18Brar), and which were linked by C5, C10 or C14 acyl chains. Using mMincle NFAT-GFP reporter cells and murine WT and Mincle^−/− bone marrow derived macrophages (BMDMs), we demonstrated that the dimeric ligands activate Mincle signalling, with the C10-linked TDB dimer 3b leading to high levels of IL-1β, IL-6 and, in particular, TNF-α in vitro. Dimer 3b was then tested for its adjuvant properties in vivo using OVA as a model antigen and was found to induce significantly more germinal centre B cells compared to OVA alone and TDB + OVA (unconjugated); however neither TDB nor dimer 3b led to an increase in T cell numbers relative to OVA alone. Taken together, these data provide proof of concept that dimeric Mincle ligands are a new class of potential Mincle-mediated vaccine adjuvants.