A Designed <i>α</i>‐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. <i>α</i>-galactosylceramide (<i>α</i>-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, <i>α</i>-GalCer-diol, with added hydroxyl groups in the acyl chain, is designed and synthesized. Structural analyses reveal stronger affinity between <i>α</i>-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-<i>γ</i> (IFN-<i>γ</i>). 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, <i>α</i>-GalCer-diol markedly boosts the expansion of the CD11b⁺ subpopulation and enhances IFN-<i>γ</i> content in CD11b⁺ cells. These reinforced Th1-type responses collectively endow <i>α</i>-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 <i>α</i>-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.