Synthesis of Branched Trehalose Glycolipids and Their Mincle Agonist Activity

Abstract

The macrophage inducible C-type lectin (Mincle) is a pattern recognition receptor that recognizes trehalose dimycolate (TDM), and trehalose dibehenate (TDB) and related trehalose diesters, and thus represents a promising target for the development of vaccine adjuvants based on the trehalose glycolipid scaffold. To this end, we report on the synthesis of a series of long-chain α-branched, β-modified trehalose monoesters and diesters to explore how glycolipid structure affects signaling through Mincle. Key steps in our synthetic strategy include a Fráter-Seebach α-alkylation to install the C aliphatic lipid on a malic acid derivative, and the formation of a β,γ-epoxide as an intermediate from which modifications to the β-position of the lipid can be made. Biological evaluation of the derivatives using nuclear factor of activated T cells (NFAT)-green fluorescent protein (GFP) reporter cell lines expressing mMincle or hMincle revealed that the hMincle agonist activity of all diesters was superior to that of the current lead trehalose glycolipid adjuvant TDB, while the activity of several monoesters was similar to that of their diester counterparts for mMincle, but all showed reduced hMincle agonist activity. Taken together, diesters 2d-g are thus potent Mincle agonists and promising vaccine adjuvants.

Design of Trehalose‐Based Amide/Sulfonamide C‐type Lectin Receptor Signaling Compounds

“…After several attempts, we were not able to isolate the corresponding sulfonamide analogue of UM1088 but we were able to synthesize 7 h, the sulfonamide analogue of 5 k. These compounds were assayed for the secretion of inflammatory cytokines TNF, IL-1β, and IL-6 in human PBMC's. [5] Surprisingly, compounds bearing the sulfonamide functional group did not promote IL-6 production from human PBMCs (Figure 3) with the exception of low-level activity observed for plate coated 7 h and 7 i. The response was verified through the observed mild production of TNF and IL-1β only at the high concentrations.…”

“…[3,4] TDM and TDB have the ability to stimulate the innate and early adaptive immune response that has led to an interest in the potential of these molecules as adjuvants. [5] In particular, TDB has shown promise as a vaccine adjuvant for both tuberculosis and HIV when formulated in the CAF01 liposome system. [6] TDM, TDB, and TDCM, [7a] demonstrated that these glycolipids are potent agonists, [7] although TDM and TDCM have proven to be too reactogenic for human vaccine applications.…”

“…Supernatants were collected and evaluated for IL-6 levels by ELISA. TDB and TDM, which are Mincle ligands, [5] were used as a positive control in the assay. Recently, Lang and co-workers [22] demonstrated IL-6 production by stimulation of isolated APCs with TDM and TDB.…”

Emerging glyco‐based strategies to steer immune responses

“…Both compounds induced high levels of TNFα in mouse and human DCs and macrophages and strong Th1 and Th17 responses in vivo . Indeed, several studies have identified novel TDM and TDB analogues that have superior agonistic activity [ 105 , 106 ].…”

Design of Potent Mincle Signalling Agonists Based on an Alkyl b- Glucoside Template

“…25 As our analogues are alkylated cholesterol derivatives, and signal through both mouse and human Mincle, it seems unlikely that the cholesteryl Please do not adjust margins Please do not adjust margins moiety binds at the CRAC site of Mincle and is likely simply a surrogate for a lipid group. This work builds on related efforts exploring structure activity relationships of acyl-hexoses (as analogues of glucose monomycolate), 15,16 glycosyloxy-stearates (as analogues of the mannosyloxymannitol glycolipid from Malassezia pachydermatis), 28 glycerolipids (as analogues of glycerol monomycolate), 27,29 mono- 13 and diacyl trehaloses, 12,30 and lipidated diaroyltrehaloses (as analogues of brartemicin). 14,31 The present work is notable for the simplicity of the resulting agonists and the fact that unlike acyl-hexoses they exist as single stereoisomers.…”