Bioactivities and Anti-Cancer Activities of NKT-Stimulatory Phenyl-Glycolipid Formulated with a PEGylated Lipid Nanocarrier

Purpose

The glycolipid α-galactosylceramide (α-GalCer), when presented by CD1d, can modulate the immune system through the activation of natural killer T (NKT) cells. Previously, we synthesized over 30 analogs of α-GalCer and identified a compound, C34, which features two phenyl rings on the acyl chain. C34 exhibited the most potent NKT-stimulating activities, characterized by strong Th1-biased cytokines and potent anti-tumor effects in several murine tumor models. Importantly, unlike α-GalCer, C34 did not induce NKT cell anergy. Despite these promising results, the clinical application of C34 is limited by its poor aqueous solubility. PEGylation enhances the solubility of hydrophobic drugs, and numerous PEGylated drugs have received clinical approval. Consequently, we assessed the biological activity of PEGylated C34 in this study.

Methods

Murine NK1.2 cells were cultured with A20-CD1d cells in the presence of either PEGylated lipid nanocarriers encapsulating C34 (PLN-C34) or C34 dissolved in DMSO to determine IL-2 production via ELISA. C57BL/6 mice were i.v. injected with C34 or PLN-C34 to examine cytokine profiles and immune cell populations using luminex and flow cytometry, respectively. The anticancer effects of C34 and PLN-C34 were evaluated in mice bearing TC-1 lung cancer and B16 melanoma tumors. Additionally, human PBMCs were cultured with C34 or PLN-C34 to measure cytokine production through luminex.

Results

PLN-C34 demonstrated a comparable capacity to C34 in activating the NKT cell line in vitro and inducing various cytokines in vivo. Furthermore, treatment with either PLN-C34 or C34 significantly prolonged the survival of TC-1- and B16F10-bearing mice to a similar extent. Additionally, PLN-C34 effectively stimulated cytokine responses in human NKT cells, comparable to those induced by C34.

Conclusion

These findings demonstrate that the newly formulated PLN-C34 retains NKT-stimulatory activity and anti-cancer efficacy of C34, supporting the potential of PLN as a solvent for C34 for further development in cancer therapy.

Diversification of a Novel α-Galactosyl Ceramide Hotspot Boosts the Adjuvant Properties in Parenteral and Mucosal Vaccines

The development of potent adjuvants is an important step for improving the performance of subunit vaccines. CD1d agonists, such as the prototypical α-galactosyl ceramide (α-GalCer), are of special interest due to their ability to activate iNKT cells and trigger rapid dendritic cell maturation and B-cell activation. Herein, we introduce a novel derivatization hotspot at the α-GalCer skeleton, namely the N-substituent at the amide bond. The multicomponent diversification of this previously unexplored glycolipid chemotype space permitted the introduction of a variety of extra functionalities that can either potentiate the adjuvant properties or serve as handles for further conjugation to antigens toward the development of self-adjuvanting vaccines. This strategy led to the discovery of compounds eliciting enhanced antigen-specific T cell stimulation and a higher antibody response when delivered by either the parenteral or the mucosal route, as compared to a known potent CD1d agonist. Notably, various functionalized α-GalCer analogues showed a more potent adjuvant effect after intranasal immunization than a PEGylated α-GalCer analogue previously optimized for this purpose. Ultimately, this work could open multiple avenues of opportunity for the use of mucosal vaccines against microbial infections.

Synthesis of 5-Thio-α-GalCer Analogues with Fluorinated Acyl Chain on Lipid Residue and Their Biological Evaluation

Invariant natural killer T (iNKT) cells are a subclass of T cells that initiates the secretion of T helper 1 and 2 cytokines after recognizing CD1d protein presented glycolipid antigens. In this Letter, we designed and synthesized a novel series of CD1d ligand α-galactosylceramides (α-GalCers) in which the acyl chain backbone of the lipid was incorporated with fluorine atoms. The in vivo evaluation of immunostimulatory activities revealed that the synthesized α-5-thio-galactopyranosyl-N-perfluorooctanoyl phytosphingosine exhibited a remarkable potency toward selectively enhancing T_H1 cytokine production with the IFN γ/IL-4 ratio of 9/1, while its perfluorotetradecanoyl counterpart showed T_H2 profile with an IFN γ/IL-4 ratio of 0.59/1. The analogues synthesized here would be used as probes to study lipid-protein interactions in α-GalCer/CD1d complexes.