Activation of human invariant natural killer T cells with a thioglycoside analogue of α-galactosylceramide

Abstract

Activation of CD1d-restricted invariant NKT (iNKT) cells with the glycolipid α-galactosylceramide (α-GalCer) confers protection against disease in murine models, however, clinical trials in humans have had limited impact. We synthesized a novel thioglycoside analogue of α-GalCer, denoted α-S-GalCer, and tested its efficacy for stimulating human iNKT cells in vitro. α-S-GalCer stimulated cytokine release by iNKT cells in a CD1d-dependent manner and primed CD1d(+) target cells for lysis. α-S-GalCer-stimulated iNKT cells induced maturation of monocyte-derived dendritic cells into antigen-presenting cells that released IL-12 and small amounts of IL-10. The nature and potency of α-S-GalCer and α-GalCer in human iNKT cell activation were similar. However, in contrast to α-GalCer, α-S-GalCer did not activate murine iNKT cells in vivo. Because of its enhanced stability in biological systems, α-S-GalCer may be superior to α-GalCer as a parent compound for developing adjuvant therapies for humans.

Synthesis and immunostimulatory activity of two α-S-galactosyl phenyl-capped ceramides

“…Mock-transfected or CD1d-transfected HeLa cells were pulsed for 18-24 hours with medium alone or with 0.1, 1 or 10 µg/mL of glycolipid antigen. 13,19 Equal numbers of expanded and rested NKT cells were added for a further 24 hours and cell supernatants were then harvested and assayed for the T H 1, T H 2 and regulatory cytokines IFN-γ, IL-4 and IL-10, Compound 1 or Compound 2 at 0.1, 1 and 10 µg/mL (increasing concentrations denoted by triangles). After 24 hours equal numbers of expanded human NKT cells were added.…”

“…Coupling constants (J) are reported in Hertz (Hz). 13 C NMR spectra were recorded at 75 or 100 MHz by using CDCl 3 or C 5 D 5 N as solvent and are reported in δ relative to the response of the solvent and the signals were assigned with the aid of DEPT, HSQC spectra. Yields refer to chromatographically pure compounds and are calculated based on reagents consumed.…”

“…3, 30.8, 30.6, 30.48, 30.46, 30.44, 30.38, 30.31, 30.30, 30.24, 30.20, 30.07, 30.01, 27.1, 26.9, 23.4 (10 5 cells/well) as described previously 13,19 . α-GalCer and α-S-GalCer were added at concentrations of 0.1 µg/ml, whereas Compounds 1 and 2 were tested at 0.1, 1 and 10 µg/ml.…”

“…The subsequent bioassay demonstrated that the α-S-GalCer possessed similar potency to KRN7000 in human NKT cell activation, and stimulated cytokine release in a similar CD1d-dependent manner as well. 13 Therefore, the thioglycoside analogues may be superior to KRN7000 as a parent compound for developing immunostimulants for humans in view of its bioactivity, stability, ease of synthesis, and flexibility in terms of the preparation of other analogues. Based on this work, we wish to report here the synthesis of two new thioglycoside analogues of α-GalCer, 1 and 2 containing a terminal phenyl group in the fatty acid chain with the long-term aim of developing therapeutic analogues with greater anticancer efficacy.…”

Synthesis and Biological Activities of 5-Thio-α-GalCers

“…Comparing to the O-glycoside KRN7000, α-C-GalCer showed a stronger Th1 response in vivo, whereas the analogue α-S-GalCer did not activate the murine iNKT cells both in vitro and in vivo, but stimulated human iNKT cells in vitro. 36 Literature search revealed that very few examples have been found for carbohydrates having the ring sulfur structure in natural products, 37 one interesting report is the 5-thio-D-mannopyranose isolated from metabolites of the marine sponge Clathria pyramida (Lendenfled) with antimicrobial activity. 38 In a molecular modeling study, the carbon−sulfur bond is proposed to be more soft with regard to absorb the deviations of bond lengths and bond angles between ethers and thioethers, thereby minimizing structural changes of carbohydrate moieties.…”