Structure-Function Implications of the Ability of Monoclonal Antibodies Against α-Galactosylceramide-CD1d Complex to Recognize β-Mannosylceramide Presentation by CD1d

Abstract

iNKT cells are CD1d-restricted T cells recognizing lipid antigens. The prototypic iNKT cell-agonist α-galactosylceramide (α-GalCer) alongside compounds with similar structures induces robust proliferation and cytokine production of iNKT cells and protects against cancer in vivo. Monoclonal antibodies (mAbs) that detect CD1d-α-GalCer complexes have provided critical information for understanding of antigen presentation of iNKT cell agonists. Although most iNKT cell agonists with antitumor properties are α-linked glycosphingolipids that can be detected by anti-CD1d-α-GalCer mAbs, β-ManCer, a glycolipid with a β-linkage, induces strong antitumor immunity via mechanisms distinct from those of α-GalCer. In this study, we unexpectedly discovered that anti-CD1d-α-GalCer mAbs directly recognized β-ManCer-CD1d complexes and could inhibit β-ManCer stimulation of iNKT cells. The binding of anti-CD1d-α-GalCer mAb with β-ManCer-CD1d complexes was also confirmed by plasmon resonance and could not be explained by α-anomer contamination. The binding of anti-CD1d-α-GalCer mAb was also observed with CD1d loaded with another β-linked glycosylceramide, β-GalCer (C26:0). Detection with anti-CD1d-α-GalCer mAbs indicates that the interface of the β-ManCer-CD1d complex exposed to the iNKT cell TCR can assume a structure like that of CD1d-α-GalCer, despite its disparate carbohydrate structure. These results suggest that certain β-linked monoglycosylceramides can assume a structural display similar to that of CD1d-α-GalCer and that the data based on anti-CD1d-α-GalCer binding should be interpreted with caution.

Chemical Biology of αGalCer: A Chemist's Toolbox for the Stimulation of Invariant Natural Killer T (iNKT) Cells

“…We expect that this, combined with immunological investigations proving their utility and advances in chemical synthesis, will underpin future studies that can pave the way for clinical use of compounds exploiting this biological mechanism. Here, we have described studies centered on αGalCer, however there is a future beyond galactose, as evident by studies of e. g. βManCer [167] and even non‐glycosylated lipids [168] …”

The role of NKT cells in gastrointestinal cancers

“…Interestingly, α-GalCer and β-ManCer-loaded tetramers conjugated with different fluorochromes stained the same type I NKT cell population, indicating that they were not acting through different cells. 44 Furthermore, it was shown that combinatorial treatment with suboptimal doses of α-GalCer and β-ManCer can synergize and provide superior protection against tumors compared to treatment with either alone. 43 The unique properties of β-ManCer may warrant its clinical development, especially in cases where α-GalCer is not effective.…”

Synthetic preparation and immunological evaluation of β-mannosylceramide and related N-acyl analogues

“…δ H (500 MHz, CDCl 3 ): 7.45-7.27 (15H, m), 7.21 (2H, dd, J = 7.7, 1.9 Hz), 4.89 (1H, d, J = 10.9 Hz), 4.78 (1H, d, J = 11.9 Hz), 4.67 (1H, d, J = 11.9 Hz), 4.63 (1H, d, J = 12.2 Hz), 4.57 (1H, d, J = 10.3 Hz), 4.55 (1H, d, J = 9.7 Hz), 4.50 (1H, d, J = 1.1 Hz), 4.23-4.08 (3H, m), 3.99 (1H, dd, J = 10.6, 2.8 Hz), 3.91 (1H, t, J = 9.2 Hz), 3.86 (1H, dd, J = 9.6, 5.5 Hz), 3.78 (1H, dd, J = 10.9, 2.3 Hz), 3.73 (1H, dd, J = 10.9, 5.2 Hz), 3.64-3.55 (2H, m), 3.45 (1H, ddd, J = 9.6, 5. (15).-Triflic acid (15 μL, 0.170 mmol) was added to a mixture of thioglycoside 14 (240 mg, 0.458 mmol), alcohol 7 (323 mg, 0.552 mmol), and NIS (190 mg, 0.802 mmol) in anhydrous CH 2 Cl 2 (5 mL) containing pre-activated 4 Å MS at −10 °C under argon. When TLC indicated completion (ca.…”

“…More recently, Terabe et al demonstrated anti-CD1d-α-GalCer monoclonal antibodies can directly recognized β-ManCer-CD1d complexes and inhibit iNKT cell stimulation by β-ManCer. 15 This result led the authors to postulate that β-ManCer can adopt a structural arrangement similar to α-GalCer within the CD1d presenting molecule, a feat that eludes other β-linked glycosylceramides. A potential problem encountered with stimulation of APCs by α-GalCer is that it induces iNKT cells to become hypo-responsive and unable to produce the same response on re-stimulation.…”