A Designed α-GalCer Analog Promotes Considerable Th1 Cytokine Response by Activating the CD1d-iNKT Axis and CD11b-Positive Monocytes/Macrophages.

Abstract

Selective helper T cell 1 (Th1) priming agonists are a promising area of investigation for immunotherapeutic treatment of various diseases. α‐galactosylceramide (α‐GalCer, KRN7000), a well‐studied Th1‐polarizer, simultaneously induces helper T cell 2 (Th2)‐type responses, which is a major drawback for its clinical applications. Based on surflex‐docking computation, α‐GalCer‐diol, with added hydroxyl groups in the acyl chain, is designed and synthesized. Structural analyses reveal stronger affinity between α‐GalCer‐diol and cluster of differentiation 1d (CD1d), leading to enhanced antigen presentation by dendritic cells (DCs) and self‐activation, as reflected by tight binding of the T‐cell receptor (TCR)/KRN7000/CD1d ternary complex and elevated production of interleukin 12 (IL‐12) and interferon‐γ (IFN‐γ). Consequently, invariant natural killer T cells (iNKTs) are activated and exhibit an improved Th1‐type cytokine profile ex vivo and in vivo. Different from KRN7000, α‐GalCer‐diol markedly boosts the expansion of the CD11b+ subpopulation and enhances IFN‐γ content in CD11b+ cells. These reinforced Th1‐type responses collectively endow α‐GalCer‐diol more robust antitumor activity in a xenograft animal model using B16‐F10 melanoma cells. Together, the data demonstrate a new mechanism through which α‐GalCer‐diol induces stronger Th1‐type responses by stimulating CD11b+ leukocyte expansion and DC‐conducted CD1d‐restricted and TCR‐mediated iNKT activation. Hence, this study may facilitate the development of novel Th1 priming agonists.