CD1d–lipid-antigen recognition by the semi-invariant NKT T-cell receptor

A Humanized Mouse Model Coupled with Computational Analysis Identifies Potent Glycolipid Agonist of Invariant NKT Cells

Invariant natural killer T (iNKT) cells play an important role in many innate and adaptive immune responses, with potential applications in cancer immunotherapy. The glycolipid KRN7000, an α-galactosylceramide, potently activates iNKT cells but has shown limited anticancer effects in human clinical trials conducted so far. In spite of almost three decades of structure-activity relationship studies, no alternative glycolipid has yet emerged as a superior clinical candidate. One reason for the slow progress in this area is that standard mouse models do not accurately reflect the specific ligand recognition by human iNKT cells and their requirements for activation. Here we evaluated a series of KRN7000 analogues using a recently developed humanized mouse model that expresses a human αTCR chain sequence and human CD1d. In this process, a more stimulatory, previously reported but largely overlooked glycolipid was identified, and its activity was probed and rationalized via molecular simulations.

Epigenetic dysregulation in Alzheimer's disease peripheral immunity

The peripheral immune system in Alzheimer's disease (AD) has not been thoroughly studied with modern sequencing methods. To investigate epigenetic and transcriptional alterations to the AD peripheral immune system, we used single-cell sequencing strategies, including assay for transposase-accessible chromatin and RNA sequencing. We reveal a striking amount of open chromatin in peripheral immune cells in AD. In CD8 T cells, we uncover a cis-regulatory DNA element co-accessible with the CXC motif chemokine receptor 3 gene promoter. In monocytes, we identify a novel AD-specific RELA transcription factor binding site adjacent to an open chromatin region in the nuclear factor kappa B subunit 2 gene. We also demonstrate apolipoprotein E genotype-dependent epigenetic changes in monocytes. Surprisingly, we also identify differentially accessible chromatin regions in genes associated with sporadic AD risk. Our findings provide novel insights into the complex relationship between epigenetics and genetic risk factors in AD peripheral immunity.

Mouse mucosal-associated invariant T cell receptor recognition of MR1 presenting the vitamin B metabolite, 5-(2-oxopropylideneamino)-6-d-ribitylaminouracil

Mucosal-associated invariant T (MAIT) cells can elicit immune responses against riboflavin-based antigens presented by the evolutionary conserved MHC class I related protein, MR1. While we have an understanding of the structural basis of human MAIT cell receptor (TCR) recognition of human MR1 presenting a variety of ligands, how the semi-invariant mouse MAIT TCR binds mouse MR1-ligand remains unknown. Here, we determine the crystal structures of 2 mouse TRAV1-TRBV13-2+ MAIT TCR-MR1-5-OP-RU ternary complexes, whose TCRs differ only in the composition of their CDR3β loops. These mouse MAIT TCRs mediate high affinity interactions with mouse MR1-5-OP-RU and cross-recognize human MR1-5-OP-RU. Similarly, a human MAIT TCR could bind mouse MR1-5-OP-RU with high affinity. This cross-species recognition indicates the evolutionary conserved nature of this MAIT TCR-MR1 axis. Comparing crystal structures of the mouse versus human MAIT TCR-MR1-5-OP-RU complexes provides structural insight into the conserved nature of this MAIT TCR-MR1 interaction and conserved specificity for the microbial antigens, whereby key germline-encoded interactions required for MAIT activation are maintained. This is an important consideration for the development of MAIT cell-based therapeutics that will rely on preclinical mouse models of disease.

Phase I/IIa Trial in Advanced Pancreatic Ductal Adenocarcinoma Treated with Cytotoxic Drug-Packaged, EGFR-Targeted Nanocells and Glycolipid-Packaged Nanocells

PURPOSE

We assessed the safety and efficacy of an EGFR-targeted, super-cytotoxic drug, PNU-159682-packaged nanocells with α-galactosyl ceramide-packaged nanocells (E-EDV-D682/GC) in patients with advanced pancreatic ductal adenocarcinoma (PDAC) who had exhausted all treatment options.

PATIENTS AND METHODS

ENG9 was a first-in-man, single-arm, open-label, phase I/IIa, dose-escalation clinical trial. Eligible patients had advanced PDAC, Eastern Cooperative Oncology Group status 0 to 1, and failed all treatments. Primary endpoints were safety and overall survival (OS).

RESULTS

Of 25 enrolled patients, seven were withdrawn due to rapidly progressive disease and one patient withdrew consent. All 25 patients were assessed for toxicity, 24 patients were assessed for OS, which was also assessed for 17 patients completing one treatment cycle [evaluable subset (ES)]. Nineteen patients (76.0%) experienced at least one treatment-related adverse event (graded 1 to 2) resolving within hours. There were no safety concerns, dose reductions, patient withdrawal, or treatment-related deaths.

Median OS (mOS) was 4.4 months; however, mOS of the 17 ES patients was 6.9 months [208 days; range, 83-591 days; 95.0% confidence interval (CI), 5.6-10.3 months] and mOS of seven patients who did not complete one cycle was 1.8 months (54 days; range, 21-72; 95.0% CI, 1.2-2.2 months). Of the ES, 47.1% achieved stable disease and one partial response. Ten subjects in the ES survived over 6 months, the longest 19.7 months. During treatments, 82.0% of the ES maintained stable weight.

CONCLUSIONS

E-EDV-D682/GC provided significant OS, minimal side effects, and weight stabilization in patients with advanced PDAC. Advanced PDAC can be safely treated with super-cytotoxic drugs via EnGeneIC Dream Vectors to overcome multidrug resistance.

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.

NKT Agonist-Antigen Conjugates as Cancer Vaccines

Natural killer T (NKT) cells are a population of innate-like T cells capable of enhancing both innate and adaptive immune responses. Co-delivering an NKT cell agonist and antigen can provide molecular signals to antigen-presenting cells, such as dendritic and B cells, that facilitate strong antigen-specific adaptive immune responses. Accordingly, there has been a significant number of developmental NKT cell-dependent vaccine therapies developed, particularly in the last decade, with many incorporating cancer antigens. In this review, we summarize studies that chemically conjugate the NKT cell agonist and antigen as an effective strategy for agonist-antigen co-delivery to drive antitumor responses.

Enhanced CD1d phosphatidylserine presentation using a single-domain antibody promotes immunomodulatory CD1d-TIM-3 interactions

BACKGROUND

CD1d is a monomorphic major histocompatibility complex class I-like molecule that presents lipid antigens to distinct T-cell subsets and can be expressed by various malignancies. Antibody-mediated targeting of CD1d on multiple myeloma cells was reported to induce apoptosis and could therefore constitute a novel therapeutic approach.

METHODS

To determine how a CD1d-specific single-domain antibody (VHH) enhances binding of the early apoptosis marker annexin V to CD1d+ tumor cells we use in vitro cell-based assays and CRISPR-Cas9-mediated gene editing, and to determine the structure of the VHH1D17-CD1d(endogenous lipid) complex we use X-ray crystallography.

RESULTS

Anti-CD1d VHH1D17 strongly enhances annexin V binding to CD1d+ tumor cells but this does not reflect induction of apoptosis. Instead, we show that VHH1D17 enhances presentation of phosphatidylserine (PS) in CD1d and that this is saposin dependent. The crystal structure of the VHH1D17-CD1d(endogenous lipid) complex demonstrates that VHH1D17 binds the A'-pocket of CD1d, leaving the lipid headgroup solvent exposed, and has an electro-negatively charged patch which could be involved in the enhanced PS presentation by CD1d. Presentation of PS in CD1d does not trigger phagocytosis but leads to greatly enhanced binding of T-cell immunoglobulin and mucin domain containing molecules (TIM)-1 to TIM-3, TIM-4 and induces TIM-3 signaling.

CONCLUSION

Our findings reveal the existence of an immune modulatory CD1d(PS)-TIM axis with potentially unexpected implications for immune regulation in both physiological and pathological conditions.

CD1 lipidomes reveal lipid-binding motifs and size-based antigen-display mechanisms

The CD1 system binds lipid antigens for display to T cells. Here, we solved lipidomes for the four human CD1 antigen-presenting molecules, providing a map of self-lipid display. Answering a basic question, the detection of >2,000 CD1-lipid complexes demonstrates broad presentation of self-sphingolipids and phospholipids. Whereas peptide antigens are chemically processed, many lipids are presented in an unaltered form. However, each type of CD1 protein differentially edits the self-lipidome to show distinct capture motifs based on lipid length and chemical composition, suggesting general antigen display mechanisms. For CD1a and CD1d, lipid size matches the CD1 cleft volume. CD1c cleft size is more variable, and CD1b is the outlier, where ligands and clefts show an extreme size mismatch that is explained by uniformly seating two small lipids in one cleft. Furthermore, the list of compounds that comprise the integrated CD1 lipidome supports the ongoing discovery of lipid blockers and antigens for T cells.

CD1 displays its own negative regulators

After two decades of the study of lipid antigens that activate CD1-restricted T cells, new studies show how autoreactive αβ T-cell receptors (TCRs) can directly recognize the outer surface of CD1 proteins in ways that are lipid-agnostic. Most recently, this lipid agnosticism has turned to negativity, with the discovery of natural CD1 ligands that dominantly negatively block autoreactive αβ TCR binding to CD1a and CD1d. This review highlights the basic differences between positive and negative regulation of cellular systems. We outline strategies to discover lipid inhibitors of CD1-reactive T cells, whose roles in vivo are becoming clear, especially in CD1-mediated skin disease.

Association of circulating markers with cognitive decline after radiation therapy for brain metastasis

BACKGROUND

A recent phase III trial (NCT01372774) comparing use of stereotactic radiosurgery [SRS] versus whole-brain radiation therapy [WBRT] after surgical resection of a single brain metastasis revealed that declines in cognitive function were more common with WBRT than with SRS. A secondary endpoint in that trial, and the primary objective in this secondary analysis, was to identify baseline biomarkers associated with cognitive impairment after either form of radiotherapy for brain metastasis. Here we report our findings on APOE genotype and serum levels of associated proteins and their association with radiation-induced neurocognitive decline.

METHODS

In this retrospective analysis of prospectively collected samples from a completed randomized clinical trial, patients provided blood samples every 3 months that were tested by genotyping and enzyme-linked immunosorbent assay, and results were analyzed in association with cognitive impairment.

RESULTS

The APOE genotype was not associated with neurocognitive impairment at 3 months. However, low serum levels of ApoJ, ApoE, or ApoA protein (all P < .01) and higher amyloid beta (Aβ 1-42) levels (P = .048) at baseline indicated a greater likelihood of neurocognitive decline at 3 months after SRS, whereas lower ApoJ levels were associated with decline after WBRT (P = .014).

CONCLUSIONS

Patients with these pretreatment serum markers should be counseled about radiation-related neurocognitive decline.

Die Kämpfe únd schláchten-the struggles and battles of innate-like effector T lymphocytes with microbes

The large majority of lymphocytes belong to the adaptive immune system, which are made up of B2 B cells and the αβ T cells; these are the effectors in an adaptive immune response. A multitudinous group of lymphoid lineage cells does not fit the conventional lymphocyte paradigm; it is the unconventional lymphocytes. Unconventional lymphocytes-here called innate/innate-like lymphocytes, include those that express rearranged antigen receptor genes and those that do not. Even though the innate/innate-like lymphocytes express rearranged, adaptive antigen-specific receptors, they behave like innate immune cells, which allows them to integrate sensory signals from the innate immune system and relay that umwelt to downstream innate and adaptive effector responses. Here, we review natural killer T cells and mucosal-associated invariant T cells-two prototypic innate-like T lymphocytes, which sense their local environment and relay that umwelt to downstream innate and adaptive effector cells to actuate an appropriate host response that confers immunity to infectious agents.

Towards a better understanding of human iNKT cell subpopulations for improved clinical outcomes

Invariant natural killer T (iNKT) cells are a unique T lymphocyte population expressing semi-invariant T cell receptors (TCRs) that recognise lipid antigens presented by CD1d. iNKT cells exhibit potent anti-tumour activity through direct killing mechanisms and indirectly through triggering the activation of other anti-tumour immune cells. Because of their ability to induce potent anti-tumour responses, particularly when activated by the strong iNKT agonist αGalCer, they have been the subject of intense research to harness iNKT cell-targeted immunotherapies for cancer treatment. However, despite potent anti-tumour efficacy in pre-clinical models, the translation of iNKT cell immunotherapy into human cancer patients has been less successful. This review provides an overview of iNKT cell biology and why they are of interest within the context of cancer immunology. We focus on the iNKT anti-tumour response, the seminal studies that first reported iNKT cytotoxicity, their anti-tumour mechanisms, and the various described subsets within the iNKT cell repertoire. Finally, we discuss several barriers to the successful utilisation of iNKT cells in human cancer immunotherapy, what is required for a better understanding of human iNKT cells, and the future perspectives facilitating their exploitation for improved clinical outcomes.

Epigenetic control of CD1D expression as a mechanism of resistance to immune checkpoint therapy in poorly immunogenic melanomas

Immune Checkpoint Therapies (ICT) have revolutionized the treatment of metastatic melanoma. However, only a subset of patients reaches complete responses. Deficient β2-microglobulin (β2M) expression impacts antigen presentation to T cells, leading to ICT resistance. Here, we investigate alternative β2M-correlated biomarkers that associate with ICT resistance. We shortlisted immune biomarkers interacting with human β2M using the STRING database. Next, we profiled the transcriptomic expression of these biomarkers in association with clinical and survival outcomes in the melanoma GDC-TCGA-SKCM dataset and a collection of publicly available metastatic melanoma cohorts treated with ICT (anti-PD1). Epigenetic control of identified biomarkers was interrogated using the Illumina Human Methylation 450 dataset from the melanoma GDC-TCGA-SKCM study. We show that β2M associates with CD1d, CD1b, and FCGRT at the protein level. Co-expression and correlation profile of B2M with CD1D, CD1B, and FCGRT dissociates in melanoma patients following B2M expression loss. Lower CD1D expression is typically found in patients with poor survival outcomes from the GDC-TCGA-SKCM dataset, in patients not responding to anti-PD1 immunotherapies, and in a resistant anti-PD1 pre-clinical model. Immune cell abundance study reveals that B2M and CD1D are both enriched in tumor cells and dendritic cells from patients responding to anti-PD1 immunotherapies. These patients also show increased levels of natural killer T (NKT) cell signatures in the tumor microenvironment (TME). Methylation reactions in the TME of melanoma impact the expression of B2M and SPI1, which controls CD1D expression. These findings suggest that epigenetic changes in the TME of melanoma may impact β2M and CD1d-mediated functions, such as antigen presentation for T cells and NKT cells. Our hypothesis is grounded in comprehensive bioinformatic analyses of a large transcriptomic dataset from four clinical cohorts and mouse models. It will benefit from further development using well-established functional immune assays to support understanding the molecular processes leading to epigenetic control of β2M and CD1d. This research line may lead to the rational development of new combinatorial treatments for metastatic melanoma patients that poorly respond to ICT.

UcTCRdb: An unconventional T cell receptor sequence database with online analysis functions

Unlike conventional major histocompatibility complex (MHC) class I and II molecules reactive T cells, the unconventional T cell subpopulations recognize various non-polymorphic antigen-presenting molecules and are typically characterized by simplified patterns of T cell receptors (TCRs), rapid effector responses and ‘public’ antigen specificities. Dissecting the recognition patterns of the non-MHC antigens by unconventional TCRs can help us further our understanding of the unconventional T cell immunity. The small size and irregularities of the released unconventional TCR sequences are far from high-quality to support systemic analysis of unconventional TCR repertoire. Here we present UcTCRdb, a database that contains 669,900 unconventional TCRs collected from 34 corresponding studies in humans, mice, and cattle. In UcTCRdb, users can interactively browse TCR features of different unconventional T cell subsets in different species, search and download sequences under different conditions. Additionally, basic and advanced online TCR analysis tools have been integrated into the database, which will facilitate the study of unconventional TCR patterns for users with different backgrounds. UcTCRdb is freely available at http://uctcrdb.cn/.

Cell-free protein synthesis of CD1E and B2M protein and in vitro interaction

CD1E, one of the most important glycolipid antigens on T cell membranes, is required for glycolipid antigen presentation on the cell surface. Cell-based recombinant expression systems have many limitations for synthesizing transmembrane proteins such as CD1E, including low protein yields and miss folding. To overcome these challenges, here we successfully synthesized high-quality soluble CD1E using an E.coli cell-free protein synthesis system (CFPS) with the aid of detergent. Following purification by Ni²⁺ affinity chromatography, we were able to obtain CD1E with ≥90% purity. Furthermore, we used the string website to predict the protein interaction network of CD1E and identified a potential binding partner━B2M. Similarly, we synthesized soluble B2M in the E.coli CFPS. Finally, we verified the interaction between CD1E and B2M by using Surface Plasmon Resonance (SPR). Taken together, the methods described here provide an alternative way to obtain active transmembrane protein and may facilitate future structural and functional studies on CD1E.

Graft-versus-Host Disease Modulation by Innate T Cells

Allogeneic cell therapies, defined by genetically mismatched transplantation, have the potential to become a cost-effective solution for cell-based cancer immunotherapy. However, this type of therapy is often accompanied by the development of graft-versus-host disease (GvHD), induced by the mismatched major histocompatibility complex (MHC) between healthy donors and recipients, leading to severe complications and death. To address this issue and increase the potential for allogeneic cell therapies in clinical practice, minimizing GvHD is a crucial challenge. Innate T cells, encompassing subsets of T lymphocytes including mucosal-associated invariant T (MAIT) cells, invariant natural killer T (iNKT) cells, and gamma delta T (γδ T) cells, offer a promising solution. These cells express MHC-independent T-cell receptors (TCRs), allowing them to avoid MHC recognition and thus GvHD. This review examines the biology of these three innate T-cell populations, evaluates research on their roles in GvHD modulation and allogeneic stem cell transplantation (allo HSCT), and explores the potential futures for these therapies.

αβ T-cell receptor recognition of self-phosphatidylinositol presented by CD1b

CD1 glycoproteins present lipid-based antigens to T-cell receptors (TCRs). A role for CD1b in T-cell-mediated autoreactivity was proposed when it was established that CD1b can present self-phospholipids with short alkyl chains (∼C34) to T cells; however, the structural characteristics of this presentation and recognition are unclear. Here, we report the 1.9 Å resolution binary crystal structure of CD1b presenting a self-phosphatidylinositol-C34:1 and an endogenous scaffold lipid. Moreover, we also determined the 2.4 Å structure of CD1b-phosphatidylinositol complexed to an autoreactive αβ TCR, BC8B. We show that the TCR docks above CD1b and directly contacts the presented antigen, selecting for both the phosphoinositol headgroup and glycerol neck region via antigen remodeling within CD1b and allowing lateral escape of the inositol moiety through a channel formed by the TCR α-chain. Furthermore, through alanine scanning mutagenesis and surface plasmon resonance, we identified key CD1b residues mediating this interaction, with Glu-80 abolishing TCR binding. We in addition define a role for both CD1b α1 and CD1b α2 molecular domains in modulating this interaction. These findings suggest that the BC8B TCR contacts both the presented phospholipid and the endogenous scaffold lipid via a dual mechanism of corecognition. Taken together, these data expand our understanding into the molecular mechanisms of CD1b-mediated T-cell autoreactivity.

LilrB3 is a putative cell surface receptor of APOE4

The three isoforms of apolipoprotein E (APOE2, APOE3, and APOE4) only differ in two amino acid positions but exert quite different immunomodulatory effects. The underlying mechanism of such APOE isoform dependence remains enigmatic. Here we demonstrate that APOE4, but not APOE2, specifically interacts with the leukocyte immunoglobulin-like receptor B3 (LilrB3). Two discrete immunoglobin-like domains of the LilrB3 extracellular domain (ECD) recognize a positively charged surface patch on the N-terminal domain (NTD) of APOE4. The atomic structure reveals how two APOE4 molecules specifically engage two LilrB3 molecules, bringing their intracellular signaling motifs into close proximity through formation of a hetero-tetrameric complex. Consistent with our biochemical and structural analyses, APOE4, but not APOE2, activates human microglia cells (HMC3) into a pro-inflammatory state in a LilrB3-dependent manner. Together, our study identifies LilrB3 as a putative immune cell surface receptor for APOE4, but not APOE2, and may have implications for understanding the biological functions as well as disease relevance of the APOE isoforms.

Engagement with the TCR induces plasticity in antigenic ligands bound to MHC class I and CD1 molecules

Complementarity-determining regions (CDRs) of αβ T-cell receptors (TCRs) sense peptide-bound MHC (pMHC) complexes via chemical interactions, thereby mediating antigen specificity and MHC restriction. Flexible finger-like movement of CDR loops contributes to the establishment of optimal interactions with pMHCs. In contrast, peptide ligands captured in MHC molecules are considered more static because of the rigid hydrogen-bond network that stabilizes peptide ligands in the antigen-binding groove of MHC molecules. An array of crystal structures delineating pMHC complexes in TCR-docked and TCR-undocked forms is now available, which enables us to assess TCR engagement-induced conformational changes in peptide ligands. In this short review, we overview conformational changes in MHC class I-bound peptide ligands upon TCR docking, followed by those for CD1-bound glycolipid ligands. Finally, we analyze the co-crystal structure of the TCR:lipopeptide-bound MHC class I complex that we recently reported. We argue that TCR engagement-induced conformational changes markedly occur in lipopeptide ligands, which are essential for exposure of a primary T-cell epitope to TCRs. These conformational changes are affected by amino acid residues, such as glycine, that do not interact directly with TCRs. Thus, ligand recognition by specific TCRs involves not only T-cell epitopes but also non-epitopic amino acid residues. In light of their critical function, we propose to refer to these residues as non-epitopic residues affecting ligand plasticity and antigenicity (NR-PA).

Innate immunity and early liver inflammation

The innate system constitutes a first-line defence mechanism against pathogens. 80% of the blood supply entering the human liver arrives from the splanchnic circulation through the portal vein, so it is constantly exposed to immunologically active substances and pathogens from the gastrointestinal tract. Rapid neutralization of pathogens and toxins is an essential function of the liver, but so too is avoidance of harmful and unnecessary immune reactions. This delicate balance of reactivity and tolerance is orchestrated by a diverse repertoire of hepatic immune cells. In particular, the human liver is enriched in many innate immune cell subsets, including Kupffer cells (KCs), innate lymphoid cells (ILCs) like Natural Killer (NK) cells and ILC-like unconventional T cells - namely Natural Killer T cells (NKT), γδ T cells and Mucosal-associated Invariant T cells (MAIT). These cells reside in the liver in a memory-effector state, so they respond quickly to trigger appropriate responses. The contribution of aberrant innate immunity to inflammatory liver diseases is now being better understood. In particular, we are beginning to understand how specific innate immune subsets trigger chronic liver inflammation, which ultimately results in hepatic fibrosis. In this review, we consider the roles of specific innate immune cell subsets in early inflammation in human liver disease.

Glioma diagnosis and therapy: Current challenges and nanomaterial-based solutions

Glioma is often referred to as one of the most dreadful central nervous system (CNS)-specific tumors with rapidly-proliferating cancerous glial cells, accounting for nearly half of the brain tumors at an annual incidence rate of 30-80 per a million population. Although glioma treatment remains a significant challenge for researchers and clinicians, the rapid development of nanomedicine provides tremendous opportunities for long-term glioma therapy. However, several obstacles impede the development of novel therapeutics, such as the very tight blood-brain barrier (BBB), undesirable hypoxia, and complex tumor microenvironment (TME). Several efforts have been dedicated to exploring various nanoformulations for improving BBB permeation and precise tumor ablation to address these challenges. Initially, this article briefly introduces glioma classification and various pathogenic factors. Further, currently available therapeutic approaches are illustrated in detail, including traditional chemotherapy, radiotherapy, and surgical practices. Then, different innovative treatment strategies, such as tumor-treating fields, gene therapy, immunotherapy, and phototherapy, are emphasized. In conclusion, we summarize the article with interesting perspectives, providing suggestions for future glioma diagnosis and therapy improvement.

Efficient synthesis of α-galactosylceramide and its C-6 modified analogs

The synthesis of α-galactosylceramide (KRN7000) and its C-6 modified analogs remains a challenge due to the difficult α-1,2-cis-glycosidic bond. A non-participating benzyl (Bn) protecting group has been commonly used to favor the α-glycosylation product. Here, we report the α-selective glycosylation by using a bulky 4,6-O-di-tert-butylsilylene (DTBS) galactosyl donor, regardless of the 2-benzoyl (Bz) participating group. Compared with Bn, Bz groups can be selectively removed in basic conditions without impacting the C-6 azide modification. The azide has the potential for clicking with alkyne or being easily transformed to other functional groups.

Diversity-Oriented Synthesis of a Molecular Library of Immunomodulatory α-Galactosylceramides with Fluorous-Tag-Assisted Purification and Evaluation of Their Bioactivities in Regard to IL-2 Secretion

Structural variants of α-galactosylceramide (α-GalCer) that stimulate invariant natural killer T (iNKT) cells constitute an emerging class of immunomodulatory agents in development for numerous biological applications. Variations in lipid chain length and/or fatty acids in these glycoceramides selectively trigger specific pro-inflammatory responses. Studies that would link a specific function to a structurally distinct α-GalCer rely heavily on the availability of homogeneous and pure materials. To address this need, we report herein a general route to the diversification of the ceramide portion of α-GalCer glycolipids. Our convergent synthesis commences from common building blocks and relies on the Julia–Kocienski olefination as a key step. A cleavable fluorous tag is introduced at the non-reducing end of the sugar that facilitates quick purification of products by standard fluorous solid-phase extraction. The strategy enabled the rapid generation of a focused library of 61 α-GalCer analogs by efficiently assembling various lipids and fatty acids. Furthermore, when compared against parent α-GalCer in murine cells, many of these glycolipid variants were found to have iNKT cell stimulating activity similar to or greater than KRN7000. ELISA assaying indicated that glycolipids carrying short fatty N-acyl chains (1fc and 1ga), an unsubstituted (1fh and 1fi) or CF3-substituted phenyl ring at the lipid tail, and a flexible, shorter fatty acyl chain with an aromatic ring (1ge, 1gf, and 1gg) strongly affected the activation of iNKT cells by the glycolipid-loaded antigen-presenting molecule, CD1d. This indicates that the method may benefit the design of structural modifications to potent iNKT cell-binding glycolipids.

Glycoconjugates: Synthesis, Functional Studies, and Therapeutic Developments

Glycoconjugates are major constituents of mammalian cells that are formed via covalent conjugation of carbohydrates to other biomolecules like proteins and lipids and often expressed on the cell surfaces. Among the three major classes of glycoconjugates, proteoglycans and glycoproteins contain glycans linked to the protein backbone via amino acid residues such as Asn for N-linked glycans and Ser/Thr for O-linked glycans. In glycolipids, glycans are linked to a lipid component such as glycerol, polyisoprenyl pyrophosphate, fatty acid ester, or sphingolipid. Recently, glycoconjugates have become better structurally defined and biosynthetically understood, especially those associated with human diseases, and are accessible to new drug, diagnostic, and therapeutic developments. This review describes the status and new advances in the biological study and therapeutic applications of natural and synthetic glycoconjugates, including proteoglycans, glycoproteins, and glycolipids. The scope, limitations, and novel methodologies in the synthesis and clinical development of glycoconjugates including vaccines, glyco-remodeled antibodies, glycan-based adjuvants, glycan-specific receptor-mediated drug delivery platforms, etc., and their future prospectus are discussed.

Immunomodulatory Cell Therapy Using αGalCer-Pulsed Dendritic Cells Ameliorates Heart Failure in a Murine Dilated Cardiomyopathy Model

BACKGROUND

Dilated cardiomyopathy (DCM) is a life-threatening disease, resulting in refractory heart failure. An immune disorder underlies the pathophysiology associated with heart failure progression. Invariant natural killer T (iNKT) cell activation is a prospective therapeutic strategy for ischemic heart disease. However, its efficacy in nonischemic cardiomyopathy, such as DCM, remains to be elucidated, and the feasible modality for iNKT cell activation in humans is yet to be validated.

METHODS

Dendritic cells isolated from human volunteers were pulsed with α-galactosylceramide ex vivo, which were used as α-galactosylceramide-pulsed dendritic cells (αGCDCs). We treated DCM mice harboring mutated troponin T^{ΔK210/ΔK210} with αGCDCs and evaluated the efficacy of iNKT cell activation on heart failure in DCM mice. Furthermore, we investigated the molecular basis underlying its therapeutic effects in these mice and analyzed primary cardiac cells under iNKT cell-secreted cytokines.

RESULTS

The number of iNKT cells in the spleens of DCM mice was reduced compared with that in wild-type mice, whereas αGCDC treatment activated iNKT cells, prolonged survival of DCM mice, and prevented decline in the left ventricular ejection fraction for 4 weeks, accompanied by suppressed interstitial fibrosis. Mechanistically, αGCDC treatment suppressed TGF (transforming growth factor)-β signaling and expression of fibrotic genes and restored vasculature that was impaired in DCM hearts by upregulating angiopoietin 1 (Angpt1) expression. Consistently, IFNγ (interferon gamma) suppressed TGF-β-induced Smad2/3 signaling and the expression of fibrotic genes in cardiac fibroblasts and upregulated Angpt1 expression in cardiomyocytes via Stat1.

CONCLUSIONS

Immunomodulatory cell therapy with αGCDCs is a novel therapeutic strategy for heart failure in DCM.

Development of Nasal Vaccines and the Associated Challenges

Viruses, bacteria, fungi, and several other pathogenic microorganisms usually infect the host via the surface cells of respiratory mucosa. Nasal vaccination could provide a strong mucosal and systemic immunity to combat these infections. The intranasal route of vaccination offers the advantage of easy accessibility over the injection administration. Therefore, nasal immunization is considered a promising strategy for disease prevention, particularly in the case of infectious diseases of the respiratory system. The development of a nasal vaccine, particularly the strategies of adjuvant and antigens design and optimization, enabling rapid induction of protective mucosal and systemic responses against the disease. In recent times, the development of efficacious nasal vaccines with an adequate safety profile has progressed rapidly, with effective handling and overcoming of the challenges encountered during the process. In this context, the present report summarizes the most recent findings regarding the strategies used for developing nasal vaccines as an efficient alternative to conventional vaccines.

Identification of a broad lipid repertoire associated to the endothelial cell protein C receptor (EPCR)

Evidence is mounting that the nature of the lipid bound to the endothelial cell protein C receptor (EPCR) has an impact on its biological roles, as observed in anticoagulation and more recently, in autoimmune disease. Phosphatidylethanolamine and phosphatidylcholine species dominate the EPCR lipid cargo, yet, the extent of diversity in the EPCR-associated lipid repertoire is still unknown and remains to be uncovered. We undertook mass spectrometry analyses to decipher the EPCR lipidome, and identified species not yet described as EPCR ligands, such as phosphatidylinositols and phosphatidylserines. Remarkably, we found further, more structurally divergent lipids classes, represented by ceramides and sphingomyelins, both in less abundant quantities. In support of our mass spectrometry results and previous studies, high-resolution crystal structures of EPCR in three different space groups point to a prevalent diacyl phospholipid moiety in EPCR’s pocket but a mobile and ambiguous lipid polar head group. In sum, these studies indicate that EPCR can associate with varied lipid classes, which might impact its properties in anticoagulation and the onset of autoimmune disease.

Gut Microbiota-Derived Unconventional T Cell Ligands: Contribution to Host Immune Modulation

Besides the prototypic innate and adaptive pathways, immune responses by innate-like lymphocytes have gained significant attention due to their unique roles. Among innate-like lymphocytes, unconventional T cells such as NKT cells and mucosal-associated invariant T (MAIT) cells recognize small nonpeptide molecules of specific chemical classes. Endogenous or microbial ligands are loaded to MHC class I-like molecule CD1d or MR1, and inducing immediate effector T cell and ligand structure is one of the key determinants of NKT/MAIT cell functions. Unconventional T cells are in close, constant contact with symbiotic microbes at the mucosal layer, and CD1d/MR1 can accommodate diverse metabolites produced by gut microbiota. There is a strong interest to identify novel immunoactive molecules of endobiotic (symbiont-produced) origin as new NKT/MAIT cell ligands, as well as new cognate Ags for previously uncharacterized unconventional T cell subsets. Further studies will open an possibility to explore basic biology as well as therapeutic potential.

A self-adjuvanting anti-tumor nanoliposomal vaccine based on fluorine-substituted MUC1 glycopeptide

Herein, a self-adjuvanting fluorinated MUC1-based nanoliposomal antitumor vaccine was constructed for the first time. Both the tumor-associated antigen and the mode of its presentation affect the immune response for antitumor vaccines.

Atypical sideways recognition of CD1a by autoreactive γδ T cell receptors

CD1a is a monomorphic antigen-presenting molecule on dendritic cells that presents lipids to αβ T cells. Whether CD1a represents a ligand for other immune receptors remains unknown. Here we use CD1a tetramers to show that CD1a is a ligand for Vδ1⁺ γδ T cells. Functional studies suggest that two γδ T cell receptors (TCRs) bound CD1a in a lipid-independent manner. The crystal structures of three Vγ4Vδ1 TCR-CD1a-lipid complexes reveal that the γδ TCR binds at the extreme far side and parallel to the long axis of the β-sheet floor of CD1a’s antigen-binding cleft. Here, the γδ TCR co-recognises the CD1a heavy chain and β2 microglobulin in a manner that is distinct from all other previously observed γδ TCR docking modalities. The ‘sideways’ and lipid antigen independent mode of autoreactive CD1a recognition induces TCR clustering on the cell surface and proximal T cell signalling as measured by CD3ζ phosphorylation. In contrast with the ‘end to end’ binding of αβ TCRs that typically contact carried antigens, autoreactive γδ TCRs support geometrically diverse approaches to CD1a, as well as antigen independent recognition.

T cell receptors are generally thought to contact antigens presented in an end to end configuration. Here the authors show a geometrically alternate sideways mode of recognition of the antigen-presenting molecule CD1a by a γδ T cell receptor.

Deconstructing iNKT cell development at single-cell resolution

Invariant natural killer T (iNKT) cells are increasingly regarded as disease biomarkers and immunotherapeutic targets. However, a greater understanding of their biology is necessary to effectively target these cells in the clinic. The discovery of iNKT1/2/17 cell effector subsets was a milestone in our understanding of iNKT cell development and function. Recent transcriptomic studies have uncovered an even greater heterogeneity and challenge our understanding of iNKT cell ontogeny and effector differentiation. We propose a refined model whereby iNKT cells differentiate through a dynamic and continuous instructive process that requires the accumulation and integration of various signals within the thymus or peripheral tissues. Within this framework, we question the existence of true iNKT2 cells and discuss the parallels between mouse and human iNKT cells.

The perception and response of T cells to a changing environment are based on the law of initial value

αβ T cells are critical components of the adaptive immune system and are capable of inducing sterilizing immunity after pathogen infection and eliminating transformed tumor cells. The development and function of T cells are controlled through the T cell antigen receptor, which recognizes peptides displayed on major histocompatibility complex (MHC) molecules. Here, we review how T cells generate the ability to recognize self-peptide-bound MHC molecules and use signals derived from these interactions to instruct cellular development, activation thresholds, and functional specialization in the steady state and during immune responses. We argue that the basic tenants of T cell development and function follow Weber-Fetcher's law of just noticeable differences and Wilder's law of initial value. Together, these laws argue that the ability of a system to respond and the quality of that response are scalable to the basal state of that system. Manifestation of these laws in T cells generates clone-specific activation thresholds that are based on perceivable differences between homeostasis and pathogen encounter (self versus nonself discrimination), as well as poised states for subsequent differentiation into specific effector cell lineages.

Hidden Relationships between N-Glycosylation and Disulfide Bonds in Individual Proteins

N-Glycosylation (NG) and disulfide bonds (DBs) are two prevalent co/post-translational modifications (PTMs) that are often conserved and coexist in membrane and secreted proteins involved in a large number of diseases. Both in the past and in recent times, the enzymes and chaperones regulating these PTMs have been constantly discovered to directly interact with each other or colocalize in the ER. However, beyond a few model proteins, how such cooperation affects N-glycan modification and disulfide bonding at selective sites in individual proteins is largely unknown. Here, we reviewed the literature to discover the current status in understanding the relationships between NG and DBs in individual proteins. Our results showed that more than 2700 human proteins carry both PTMs, and fewer than 2% of them have been investigated in the associations between NG and DBs. We summarized both these proteins with the reported relationships in the two PTMs and the tools used to discover the relationships. We hope that, by exposing this largely understudied field, more investigations can be encouraged to unveil the hidden relationships of NG and DBs in the majority of membranes and secreted proteins for pathophysiological understanding and biotherapeutic development.

Recent Development in NKT-Based Immunotherapy of Glioblastoma: From Bench to Bedside

Glioblastoma multiforme (GBM) is an aggressive and dismal disease with a median overall survival of around 15 months and a 5-year survival rate of 7.2%. Owing to genetic mutations, drug resistance, disruption to the blood–brain barrier (BBB)/blood–brain tumor barrier (BBTB), and the complexity of the immunosuppressive environment, the therapeutic approaches to GBM represent still major challenges. Conventional therapies, including surgery, radiotherapy, and standard chemotherapy with temozolomide, have not resulted in satisfactory improvements in the overall survival of GBM patients. Among cancer immunotherapeutic approaches, we propose that adjuvant NKT immunotherapy with invariant NKT (iNKT) and cytokine-induced killer (CIK) cells may improve the clinical scenario of this devastating disease. Considering this, herein, we discuss the current strategies of NKT therapy for GBM based primarily on in vitro/in vivo experiments, clinical trials, and the combinatorial approaches with future therapeutic potential.

6″-Modifed α-GalCer-peptide conjugate vaccine candidates protect against liver-stage malaria

Self-adjuvanting vaccines consisting of peptide epitopes conjugated to immune adjuvants are a powerful way of generating antigen-specific immune responses. We previously showed that a Plasmodium-derived peptide conjugated to a rearranged form of α-galactosylceramide (α-GalCer) could stimulate liver-resident memory T (T_RM) cells that were effective killers of liver-stage Plasmodium berghei ANKA (Pba)-infected cells. To investigate if similar or even superior T_RM responses can be induced by modifying the α-GalCer adjuvant, we created new conjugate vaccine cadidates by attaching an immunogenic Plasmodium-derived peptide antigen to 6″-substituted α-GalCer analogues. Vaccine synthesis involved developing an efficient route to α-galactosylphytosphingosine (α-GalPhs), from which the prototypical iNKT cell agonist, α-GalCer, and its 6″-deoxy-6″-thio and -amino analogues were derived. Attaching a cathepsin B-cleavable linker to the 6″-modified α-GalCer created pro-adjuvants bearing a pendant ketone group available for peptide conjugation. Optimized reaction conditions were developed that allow for the efficient conjugation of peptide antigens to the pro-adjuvants via oxime ligation to create new glycolipid-peptide (GLP) conjugate vaccines. A single dose of the vaccine candidates induced acute NKT and Plasmodium-specific CD8⁺ T cell responses that generated potent hepatic T_RM responses in mice. Our findings demonstrate that attaching antigenic peptides to 6″-modifed α-GalCer generates powerful self-adjuvanting conjugate vaccine candidates that could potentially control hepatotropic infections such as liver-stage malaria.

Candidate vaccines comprised of peptide antigen conjugated to 6″-modified α-GalCer analogues generate potent hepatic T_RM responses in mice with a single dose inducing protective immunity against malaria in a Plasmodium sporozoite challenge model.

Identification of Two Subsets of Murine DC1 Dendritic Cells That Differ by Surface Phenotype, Gene Expression, and Function

Classical dendritic cells (cDCs) in mice have been divided into 2 major subsets based on the expression of nuclear transcription factors: a CD8⁺Irf8⁺Batf3 dependent (DC1) subset, and a CD8^-Irf4⁺ (DC2) subset. We found that the CD8⁺DC1 subset can be further divided into CD8⁺DC1a and CD8⁺DC1b subsets by differences in surface receptors, gene expression, and function. Whereas all 3 DC subsets can act alone to induce potent Th1 cytokine responses to class I and II MHC restricted peptides derived from ovalbumin (OVA) by OT-I and OT-II transgenic T cells, only the DC1b subset could effectively present glycolipid antigens to natural killer T (NKT) cells. Vaccination with OVA protein pulsed DC1b and DC2 cells were more effective in reducing the growth of the B16-OVA melanoma as compared to pulsed DC1a cells in wild type mice. In conclusion, the Batf3-/- dependent DC1 cells can be further divided into two subsets with different immune functional profiles in vitro and in vivo.

Brief homogeneous TCR signals instruct common iNKT progenitors whose effector diversification is characterized by subsequent cytokine signaling

Innate-like T cell populations expressing conserved TCRs play critical roles in immunity through diverse developmentally acquired effector functions. Focusing on the prototypical lineage of invariant natural killer T (iNKT) cells, we sought to dissect the mechanisms and timing of fate decisions and functional effector differentiation. Utilizing induced expression of the semi-invariant NKT cell TCR on double positive thymocytes, an initially highly synchronous wave of iNKT cell development was triggered by brief homogeneous TCR signaling. After reaching a uniform progenitor state characterized by IL-4 production potential and proliferation, effector subsets emerged simultaneously, but then diverged toward different fates. While NKT17 specification was quickly completed, NKT1 cells slowly differentiated and expanded. NKT2 cells resembled maturing progenitors, which gradually diminished in numbers. Thus, iNKT subset diversification occurs in dividing progenitor cells without acute TCR input but utilizes multiple active cytokine signaling pathways. These data imply a two-step model of iNKT effector differentiation.

Our evolving understanding of the role of the γδ T cell receptor in γδ T cell mediated immunity

The γδ T cell immune cell lineage has remained relatively enigmatic and under-characterised since their identification. Conversely, the insights we have, highlight their central importance in diverse immunological roles and homeostasis. Thus, γδ T cells are considered as potentially a new translational tool in the design of new therapeutics for cancer and infectious disease. Here we review our current understanding of γδ T cell biology viewed through a structural lens centred on the how the γδ T cell receptor mediates ligand recognition. We discuss the limited knowledge of antigens, the structural basis of such reactivities and discuss the emerging trends of γδ T cell reactivity and implications for γδ T cell biology.

Benzofuran sulfonates and small self-lipid antigens activate type II NKT cells via CD1d

Natural killer T (NKT) cells detect lipids presented by CD1d. Most studies focus on type I NKT cells that express semi-invariant αβ T cell receptors (TCR) and recognize α-galactosylceramides. However, CD1d also presents structurally distinct lipids to NKT cells expressing diverse TCRs (type II NKT cells), but our knowledge of the antigens for type II NKT cells is limited. An early study identified a nonlipidic NKT cell agonist, phenyl pentamethyldihydrobenzofuransulfonate (PPBF), which is notable for its similarity to common sulfa drugs, but its mechanism of NKT cell activation remained unknown. Here, we demonstrate that a range of pentamethylbenzofuransulfonates (PBFs), including PPBF, activate polyclonal type II NKT cells from human donors. Whereas these sulfa drug-like molecules might have acted pharmacologically on cells, here we demonstrate direct contact between TCRs and PBF-treated CD1d complexes. Further, PBF-treated CD1d tetramers identified type II NKT cell populations expressing αβTCRs and γδTCRs, including those with variable and joining region gene usage (TRAV12-1-TRAJ6) that was conserved across donors. By trapping a CD1d-type II NKT TCR complex for direct mass-spectrometric analysis, we detected molecules that allow the binding of CD1d to TCRs, finding that both selected PBF family members and short-chain sphingomyelin lipids are present in these complexes. Furthermore, the combination of PPBF and short-chain sphingomyelin enhances CD1d tetramer staining of PPBF-reactive T cell lines over either molecule alone. This study demonstrates that nonlipidic small molecules, which resemble sulfa drugs implicated in systemic hypersensitivity and drug allergy reactions, are targeted by a polyclonal population of type II NKT cells in a CD1d-restricted manner.

Adoptive Transfer of Autologous Invariant Natural Killer T Cells as Immunotherapy for Advanced Hepatocellular Carcinoma: A Phase I Clinical Trial

Lessons Learned

Administration of autologous invariant natural killer T (iNKT) cells was safe and well‐tolerated in patients with hepatocellular carcinoma (Barcelona Clinic Liver Cancer stage B/C).

Expanded iNKT cells produced T‐helper 1–like responses with possible antitumor activity.

No severe adverse events were observed in any of the enrolled patients, including one patient who received 10¹⁰ in vitro–expanded autologous iNKT cells as a single infusion.

Background

Invariant natural killer T cells co‐express T‐cell antigen receptor and natural killer (NK) cell receptors. Invariant natural killer T (iNKT) cells exhibit antitumor activity, but their numbers and functions are impaired in patients with hepatocellular carcinoma (HCC). The adoptive transfer of iNKT cells might treat advanced HCC.

Methods

This phase I study (NCT03175679) enrolled 10 patients with HCC (Barcelona Clinic Liver Cancer [BCLC] stage B/C) at Beijing YouAn Hospital (April 2017 to May 2018). iNKT cells isolated from peripheral blood mononuclear cells (PBMCs) were expanded and alpha‐galactosylceramide (α‐GalCer)–pulsed. Dosage escalated from 3 × 10⁷ to 6 × 10⁷ to 9 × 10⁷ cells/m² (3+3 design). An exploratory dose trial (1 × 10¹⁰ cells/m²) was conducted in one patient.

Results

Expanded iNKT cells produced greater quantities of T‐helper 1 (Th1) cytokines (e.g., interferon‐gamma, perforin, and granzyme B) but less interleukin‐4 than nonexpanded iNKT cells. Circulating numbers of iNKT cells and activated NK cells were increased after iNKT cell infusion. Most treatment‐related adverse events were grade 1–2, and three grade 3 adverse events were reported; all resolved without treatment. Four patients were progression‐free at 5.5, 6, 7, and 11 months after therapy, and one patient was alive and without tumor recurrence at the last follow‐up. Five patients died at 1.5 to 11 months after treatment.

Conclusion

Autologous iNKT cell treatment is safe and well‐tolerated. Expanded iNKT cells produce Th1‐like responses with possible antitumor activity. The antitumor effects of iNKT cell infusion in patients with advanced HCC merit further investigation.

CD1a selectively captures endogenous cellular lipids that broadly block T cell response

We optimized lipidomics methods to broadly detect endogenous lipids bound to cellular CD1a proteins. Whereas membrane phospholipids dominate in cells, CD1a preferentially captured sphingolipids, especially a C42, doubly unsaturated sphingomyelin (42:2 SM). The natural 42:2 SM but not the more common 34:1 SM blocked CD1a tetramer binding to T cells in all human subjects tested. Thus, cellular CD1a selectively captures a particular endogenous lipid that broadly blocks its binding to TCRs. Crystal structures show that the short cellular SMs stabilized a triad of surface residues to remain flush with CD1a, but the longer lipids forced the phosphocholine group to ride above the display platform to hinder TCR approach. Whereas nearly all models emphasize antigen-mediated T cell activation, we propose that the CD1a system has intrinsic autoreactivity and is negatively regulated by natural endogenous inhibitors selectively bound in its cleft. Further, the detailed chemical structures of natural blockers could guide future design of therapeutic blockers of CD1a response.

A multilayered immune system through the lens of unconventional T cells

The unconventional T cell compartment encompasses a variety of cell subsets that straddle the line between innate and adaptive immunity, often reside at mucosal surfaces and can recognize a wide range of non-polymorphic ligands. Recent advances have highlighted the role of unconventional T cells in tissue homeostasis and disease. In this Review, we recast unconventional T cell subsets according to the class of ligand that they recognize; their expression of semi-invariant or diverse T cell receptors; the structural features that underlie ligand recognition; their acquisition of effector functions in the thymus or periphery; and their distinct functional properties. Unconventional T cells follow specific selection rules and are poised to recognize self or evolutionarily conserved microbial antigens. We discuss these features from an evolutionary perspective to provide insights into the development and function of unconventional T cells. Finally, we elaborate on the functional redundancy of unconventional T cells and their relationship to subsets of innate and adaptive lymphoid cells, and propose that the unconventional T cell compartment has a critical role in our survival by expanding and complementing the role of the conventional T cell compartment in protective immunity, tissue healing and barrier function.

The Role of NKT Cells in Glioblastoma

Glioblastoma is an aggressive and deadly cancer, but to date, immunotherapies have failed to make significant strides in improving prognoses for glioblastoma patients. One of the current challenges to developing immunological interventions for glioblastoma is our incomplete understanding of the numerous immunoregulatory mechanisms at play in the glioblastoma tumor microenvironment. We propose that Natural Killer T (NKT) cells, which are unconventional T lymphocytes that recognize lipid antigens presented by CD1d molecules, may play a key immunoregulatory role in glioblastoma. For example, evidence suggests that the activation of type I NKT cells can facilitate anti-glioblastoma immune responses. On the other hand, type II NKT cells are known to play an immunosuppressive role in other cancers, as well as to cross-regulate type I NKT cell activity, although their specific role in glioblastoma remains largely unclear. This review provides a summary of our current understanding of NKT cells in the immunoregulation of glioblastoma as well as highlights the involvement of NKT cells in other cancers and central nervous system diseases.

CD36 family members are TCR-independent ligands for CD1 antigen-presenting molecules

CD1c presents lipid-based antigens to CD1c-restricted T cells, which are thought to be a major component of the human T cell pool. However, the study of CD1c-restricted T cells is hampered by the presence of an abundantly expressed, non-T cell receptor (TCR) ligand for CD1c on blood cells, confounding analysis of TCR-mediated CD1c tetramer staining. Here, we identified the CD36 family (CD36, SR-B1, and LIMP-2) as ligands for CD1c, CD1b, and CD1d proteins and showed that CD36 is the receptor responsible for non-TCR-mediated CD1c tetramer staining of blood cells. Moreover, CD36 blockade clarified tetramer-based identification of CD1c-restricted T cells and improved identification of CD1b- and CD1d-restricted T cells. We used this technique to characterize CD1c-restricted T cells ex vivo and showed diverse phenotypic features, TCR repertoire, and antigen-specific subsets. Accordingly, this work will enable further studies into the biology of CD1 and human CD1-restricted T cells.

Reduced dose of PTCy followed by adjuvant α-galactosylceramide enhances GVL effect without sacrificing GVHD suppression

Posttransplantation cyclophosphamide (PTCy) has become a popular option for haploidentical hematopoietic stem cell transplantation (HSCT). However, personalized methods to adjust immune intensity after PTCy for each patient’s condition have not been well studied. Here, we investigated the effects of reducing the dose of PTCy followed by α-galactosylceramide (α-GC), a ligand of iNKT cells, on the reciprocal balance between graft-versus-host disease (GVHD) and the graft-versus-leukemia (GVL) effect. In a murine haploidentical HSCT model, insufficient GVHD prevention after reduced-dose PTCy was efficiently compensated for by multiple administrations of α-GC. The ligand treatment maintained the enhanced GVL effect after reduced-dose PTCy. Phenotypic analyses revealed that donor-derived B cells presented the ligand and induced preferential skewing to the NKT2 phenotype rather than the NKT1 phenotype, which was followed by the early recovery of all T cell subsets, especially CD4⁺Foxp3⁺ regulatory T cells. These studies indicate that α-GC administration soon after reduced-dose PTCy restores GVHD-preventing activity and maintains the GVL effect, which is enhanced by reducing the dose of PTCy. Our results provide important information for the development of a novel strategy to optimize PTCy-based transplantation, particularly in patients with a potential relapse risk.

The nonclassical immune surveillance for ERAAP function

The peptide repertoire presented by MHC class I molecules on the cell surface is essential for the immune surveillance of intracellular pathogens and transformed cells. The generation of this peptide repertoire is critically dependent on the endoplasmic reticulum aminopeptidase associated with antigen processing (ERAAP). Loss of ERAAP function leads to the generation of a profoundly disrupted peptide repertoire including many novel and immunogenic peptides. Strikingly, a large fraction of these novel peptides on ERAAP-KO cells are presented by the nonclassical MHC Ib molecule, Qa-1^b. One immunodominant Qa-1^b-restricted novel peptide is recognized by a unique CD8⁺ T cell population showing features of both conventional cytotoxic T cells and unconventional innate-like T cells. While much remains to be uncovered, here we summarize the latest discoveries of our lab on the important immune surveillance of ERAAP function mediated by nonclassical MHC Ib molecules and their unusual cognate T cells.