An immunostimulatory glycolipid that blocks SARS-CoV-2, RSV, and influenza infections in vivo

Rationally Designed Highly Potent NKT Cell Agonists with Different Cytokine Selectivity through Hydrogen-Bond Interaction

Synthetic α-galactosylceramide (αGalCer) and its analogues as powerful agonists for natural killer T (NKT) cell manipulation have received significant attention in immunotherapy and adjuvant development. However, identifying new potent NKT cell agonists, especially those with Th1 selectivity that promote anticancer effects, remains a challenging task. In this work, we introduced a sulfonamide group into the acyl chain of αGalCer to form additional hydrogen bonds to intensify the glycolipid/CD1d interaction. Two compounds GCS-11 and GCS-12 demonstrated remarkable potency while exhibiting different cytokine induction patterns. Compared to αGalCer, the Th1-biased GCS-11 exhibited a 6-fold increase in IFN-γ but not IL-4, while the Th1/2-balanced GCS-12 elicited 7- and 5-fold increase in IFN-γ and IL-4, respectively, in vivo. These findings place them among the most potent NKT cell agonists, with superior antitumor effects. Therefore, hydrogen-bond-involved derivatization could be a powerful strategy to develop potent and polarized NKT cell agonists for various immunotherapies.

Stereospecific Synthesis and Biological Evaluation of KRN7000 Analogues with Thio-modifications at the Acyl Moiety

α-Galactosylceramide (KRN7000 or α-GalCer) analogues terminated with phenyl (Ph) groups at the acyl moiety possess more potency than KRN7000 to activate invariant natural killer T (iNKT) cells for inducing a T helper 1 (Th1)-biased immune response. However, biological activities of phenyl glycolipids with thio-modifications at the acyl moiety remain unknown, and facile approaches for highly stereoselective synthesis of KRN7000 and its analogues are rather scarce. Herein, we exploited 4,6-di-O-tert-butylsilylene (DTBS)-directed stereospecific galactosylation to efficiently synthesize various α-GalCer analogues bearing thioamide, terminal thiophenyl and dual modifications at the acyl moiety. Biological evaluations suggest that a new analogue S34 featuring a terminal Ph-S-Ph-F group exhibits a more superior Th1-biased immune response in mice. Molecular docking analysis revealed that the introduction of a sulfur atom influences vital hydrogen bonding interactions between glycolipids and the cluster of differentiation 1d (CDld), thus adjusting the stability of the glycolipid-CDld complex.

Glycolipid antigen recognition by invariant natural killer T cells and its role in homeostasis and antimicrobial responses

Due to the COVID-19 pandemic, the importance of developing effective vaccines has received more attention than ever before. To maximize the effects of vaccines, it is important to select adjuvants that induce strong and rapid innate and acquired immune responses. Invariant natural killer T (iNKT) cells, which constitute a small population among lymphocytes, bypass the innate and acquired immune systems through the rapid production of cytokines after glycolipid recognition; hence, their activation could be used as a vaccine strategy against emerging infectious diseases. Additionally, the diverse functions of iNKT cells, including enhancing antibody production, are becoming more understood in recent years. In this review, we briefly describe the functional subset of iNKT cells and introduce the glycolipid antigens recognized by them. Furthermore, we also introduce novel vaccine development taking advantages of iNKT cell activation against infectious diseases.

IL-27 regulates the differentiation of follicular helper NKT cells via metabolic adaptation of mitochondria

Invariant natural killer T (iNKT) cells are innate-like T lymphocytes that express an invariant T cell receptor α chain and contribute to bridging innate and acquired immunity with rapid production of large amounts of cytokines after stimulation. Among effecter subsets of iNKT cells, follicular helper NKT (NKTFH) cells are specialized to help B cells. However, the mechanisms of NKTFH cell differentiation remain to be elucidated. In this report, we studied the mechanism of NKTFH cell differentiation induced by pneumococcal surface protein A and α-galactosylceramide (P/A) vaccination. We found that Gr-1+ cells helped iNKT cell proliferation and NKTFH cell differentiation in the spleen by producing interleukin-27 (IL-27) in the early phase after vaccination. The neutralization of IL-27 impaired NKTFH cell differentiation, which resulted in compromised antibody production and diminished protection against Streptococcus pneumoniae infection by the P/A vaccine. Our data indicated that Gr-1+ cell-derived IL-27 stimulated mitochondrial metabolism, meeting the energic demand required for iNKT cells to differentiate into NKTFH cells. Interestingly, Gr-1+ cell-derived IL-27 was induced by iNKT cells via interferon-γ production. Collectively, our findings suggest that optimizing the metabolism of iNKT cells was essential for acquiring specific effector functions, and they provide beneficial knowledge on iNKT cell-mediated vaccination-mediated therapeutic strategies.

Natural Killer T Cell Diversity and Immunotherapy

Invariant natural killer T cells (iNKTs), a type of unconventional T cells, share features with NK cells and have an invariant T cell receptor (TCR), which recognizes lipid antigens loaded on CD1d molecules, a major histocompatibility complex class I (MHC-I)-like protein. This interaction produces the secretion of a wide array of cytokines by these cells, including interferon gamma (IFN-γ) and interleukin 4 (IL-4), allowing iNKTs to link innate with adaptive responses. Interestingly, molecules that bind CD1d have been identified that enable the modulation of these cells, highlighting their potential pro-inflammatory and immunosuppressive capacities, as required in different clinical settings. In this review, we summarize key features of iNKTs and current understandings of modulatory α-galactosylceramide (α-GalCer) variants, a model iNKT cell activator that can shift the outcome of adaptive immune responses. Furthermore, we discuss advances in the development of strategies that modulate these cells to target pathologies that are considerable healthcare burdens. Finally, we recapitulate findings supporting a role for iNKTs in infectious diseases and tumor immunotherapy.

Intranasal Route: A Nasocerebral Approach against SARS-CoV-2 in NeuroCOVID

The nasal cavity is a prime site for viral load of SARS-CoV-2 in COVID-19, as is evident from the fact that this area has been used for sample collection for the diagnosis of COVID-19. The nasal cavity has a connection with the brain across the cribriform plate which has been reported to be a route of SARS-CoV-2 to the olfactory apparatus and the brain. Targeting the SARS-CoV-2 in the nasal cavity in patients presenting with COVID-19 and long-COVID can result in the prevention and treatment of neurological deficits and therefore needs to be prioritized as a route of potential significance.