Toll-like receptor agonists and alpha-galactosylceramide synergistically enhance the production of interferon-gamma in murine splenocytes

Rapid protection against viral infections by chemokine-accelerated post-exposure vaccination

Introduction

Prophylactic vaccines generate strong and durable immunity to avoid future infections, whereas post-exposure vaccinations are intended to establish rapid protection against already ongoing infections. Antiviral cytotoxic CD8+ T cells (CTL) are activated by dendritic cells (DCs), which themselves must be activated by adjuvants to express costimulatory molecules and so-called signal 0-chemokines that attract naive CTL to the DCs.

Hypothesis

Here we asked whether a vaccination protocol that combines two adjuvants, a toll-like receptor ligand (TLR) and a natural killer T cell activator, to induce two signal 0 chemokines, synergistically accelerates CTL activation.

Methods

We used a well-characterized vaccination model based on the model antigen ovalbumin, the TLR9 ligand CpG and the NKT cell ligand α-galactosylceramide to induce signal 0-chemokines. Exploiting this vaccination model, we studied detailed T cell kinetics and T cell profiling in different in vivo mouse models of viral infection.

Results

We found that CTL induced by both adjuvants obtained a head-start that allowed them to functionally differentiate further and generate higher numbers of protective CTL 1-2 days earlier. Such signal 0-optimized post-exposure vaccination hastened clearance of experimental adenovirus and cytomegalovirus infections.

Conclusion

Our findings show that signal 0 chemokine-inducing adjuvant combinations gain time in the race against rapidly replicating microbes, which may be especially useful in post-exposure vaccination settings during viral epi/pandemics.

Innate lymphoid cells and innate-like T cells in cancer - at the crossroads of innate and adaptive immunity

Immunotherapies targeting conventional T cells have revolutionized systemic treatment for many cancers, yet only a subset of patients benefit from these approaches. A better understanding of the complex immune microenvironment of tumours is needed to design the next generation of immunotherapeutics. Innate lymphoid cells (ILCs) and innate-like T cells (ILTCs) are abundant, tissue-resident lymphocytes that have recently been shown to have critical roles in many types of cancers. ILCs and ILTCs rapidly respond to changes in their surrounding environment and act as the first responders to bridge innate and adaptive immunity. This places ILCs and ILTCs as pivotal orchestrators of the final antitumour immune response. In this Review, we outline hallmarks of ILCs and ILTCs and discuss their emerging role in antitumour immunity, as well as the pathophysiological adaptations leading to their pro-tumorigenic function. We explore the pleiotropic, in parts redundant and sometimes opposing, mechanisms that underlie the delicate interplay between the different subsets of ILCs and ILTCs. Finally, we highlight their role in amplifying and complementing conventional T cell functions and summarize immunotherapeutic strategies for targeting ILCs and ILTCs in cancer.

α-Galactosylceramide and its analog OCH differentially affect the pathogenesis of ISO-induced cardiac injury in mice

Immunotherapies for cancers may cause severe and life-threatening cardiotoxicities. The underlying mechanisms are complex and largely elusive. Currently, there are several ongoing clinical trials based on the use of activated invariant natural killer T (iNKT) cells. The potential cardiotoxicity commonly associated with this particular immunotherapy has yet been carefully evaluated. The present study aims to determine the effect of activated iNKT cells on normal and β-adrenergic agonist (isoproterenol, ISO)-stimulated hearts. Mice were treated with iNKT stimulants, α-galactosylceramide (αGC) or its analog OCH, respectively, to determine their effect on ISO-induced cardiac injury. We showed that administration of αGC (activating both T helper type 1 (Th1)- and T helper type 2 (Th2)-liked iNKT cells) significantly accelerated the progressive cardiac injury, leading to enhanced cardiac hypertrophy and cardiac fibrosis with prominent increases in collagen deposition and TGF-β1, IL-6, and alpha smooth muscle actin expression. In contrast to αGC, OCH (mainly activating Th2-liked iNKT cells) significantly attenuated the progression of cardiac injury and cardiac inflammation induced by repeated infusion of ISO. Flow cytometry analysis revealed that αGC promoted inflammatory macrophage infiltration in the heart, while OCH was able to restrain the infiltration. In vitro coculture of αGC- or OCH-pretreated primary peritoneal macrophages with primary cardiac fibroblasts confirmed the profibrotic effect of αGC and the antifibrotic effect of OCH. Our results demonstrate that activating both Th1- and Th2-liked iNKT cells is cardiotoxic, while activating Th2-liked iNKT cells is likely cardiac protective, which has implied key differences among subpopulations of iNKT cells in their response to cardiac pathological stimulation.

Intranasal Therapeutic Peptide Vaccine Promotes Efficient Induction and Trafficking of Cytotoxic T Cell Response for the Clearance of HPV Vaginal Tumors

Human papillomavirus (HPV)-induced cancers continue to affect millions of women around the world, and the five year survival rate under the current standard of care for these cancers is less than 60% in some demographics. Therefore there is still an unmet need to develop an effective therapy that can be easily administered to treat established HPV cervical cancer lesions. We sought to investigate the potential of an intranasal HPV peptide therapeutic vaccine incorporating the combination of α-Galactosylceramide (α-GalCer) and CpG-ODN adjuvants (TVAC) against established HPV genital tumors in a syngeneic C57BL/6J mouse model. We obtained evidence to show that TVAC, delivered by the mucosal intranasal route, induced high frequencies of antigen-specific CD8 T cells concurrent with significant reduction in the immunosuppressive regulatory T cells and myeloid derived suppressor cells in the tumor microenvironment (TME), correlating with sustained elimination of established HPV genital tumors in over 85% of mice. Inclusion of both the adjuvants in the vaccine was necessary for significant increase of antigen-specific CD8 T cells to the tumor and antitumor efficacy because vaccination incorporating either adjuvant alone was inefficient. These results strongly support the utility of the TVAC administered by needle-free intranasal route as a safe and effective strategy for the treatment of established genital HPV tumors.

Codelivery of mRNA with α-Galactosylceramide Using a New Lipopolyplex Formulation Induces a Strong Antitumor Response upon Intravenous Administration

Recently, the use of mRNA-based vaccines for cancer immunotherapy has gained growing attention. Several studies have shown that mRNA delivered in a vectorized format can generate a robust and efficient immune response. In this work, a new lipopolyplex vector (multi-LP), incorporating the immune adjuvant α-galactosylceramide (α-GalCer) and a multivalent cationic lipid, was proposed for the in vivo delivery of mRNA into antigen-presenting cells. We demonstrate that dendritic cells (DCs) can be targeted in vivo by intravenous administration of a α-GalCer-/mRNA-loaded multi-LP vector, without the need for its functionalization with cell-specific antibodies or ligands. The multi-LP nanoparticles loaded with a reporter mRNA efficiently led to high expression of the enhanced green fluorescence protein in DCs both in vitro and in vivo, exhibiting an intrinsic selectivity for DCs. Finally, the TRP2-mRNA/α-GalCer-based multi-LP vaccine induced a significant therapeutic effect against a highly malignant B16-F10 melanoma tumor. This study provides the first evidence that a combination of antigen-mRNA and α-GalCer can be used as an effective antitumor vaccine, inducing strong innate and adaptive immune responses.

Sphingolipids in early viral replication and innate immune activation

In this review, we summarize the mechanisms by which sphingolipids modulate virus multiplication and the host innate immune response, using a number of host-virus systems as illustrative models. Sphingolipids exert diverse functions, both at the level of the viral life cycle and in the regulation of antiviral immune responses. Sphingolipids may influence viral replication in three ways: by serving as (co)receptors during viral entry, by modulating virus replication, and by shaping the antiviral immune response. Several studies have demonstrated that sphingosine kinases (SphK) and their product, sphingosine-1-phosphate (S1P), enhance the replication of influenza, measles, and hepatitis B virus (HBV). In contrast, ceramides, particularly S1P and SphK1, influence the expression of type I interferon (IFN-I) by modulating upstream antiviral signaling and enhancing dendritic cell maturation, differentiation, and positioning in tissue. The synthetic molecule α-galactosylceramide has also been shown to stimulate natural killer cell activation and interferon (IFN)-γ secretion. However, to date, clinical trials have failed to demonstrate any clinical benefit for sphingolipids in the treatment of cancer or HBV infection. Taken together, these findings show that sphingolipids play an important and underappreciated role in the control of virus replication and the innate immune response.

Thermostability of the coating, antigen and immunostimulator in an adjuvanted oral capsule vaccine formulation

Oral vaccines present an attractive alternative to injectable vaccines for enteric diseases due to ease of delivery and the induction of intestinal immunity at the site of infection. However, susceptibility to gastrointestinal proteolysis, limited transepithelial uptake and a lack of clinically acceptable adjuvants present significant challenges. A further challenge to mass vaccination in developing countries is the very expensive requirement to maintain the cold chain. We recently described the effectiveness of a Single Multiple Pill^® (SmPill^®) adjuvanted capsule approach to enhance the effectiveness of a candidate enterotoxigenic Escherichia coli (ETEC) oral vaccine. Here it was demonstrated that this delivery system maintains the antigenicity of ETEC colonisation factor antigen I (CFA/I) and the immunostimulatory activity of the orally active α-Galactosylceramide (α-GalCer) adjuvant after storage of SmPill^® minispheres under room temperature and extreme storage conditions for several months. In addition, the internal structure of the cores of SmPill^® minispheres and antigen release features at intestinal pH were found to be preserved under all these conditions. However, changes in the surface morphology of SmPill^® minispheres leading to the antigen release at gastric pH were observed after a few weeks of storage under extreme conditions. Those modifications were prevented by the introduction of an Opadry^® White film coating layer between the core of SmPill^® minispheres and the enteric coating. Under these conditions, protection against antigen release at gastric pH was maintained even under high temperature and humidity conditions. These results support the potential of the SmPill^® minisphere approach to maintain the stability of an adjuvanted whole cell killed oral vaccine formulation.

Engaging Natural Killer T Cells as 'Universal Helpers' for Vaccination

Conventional vaccine adjuvants enhance peptide-specific T-cell and B-cell responses by modifying peptide stability or uptake or by binding to pattern-recognition receptors on antigen-presenting cells (APCs). This article discusses the application of a distinct mechanism of adjuvant activity: the activation of type I, or invariant, natural killer T (iNKT) cells to drive cellular and humoral immune responses. Using a semi-invariant T-cell receptor (TCR), iNKT cells recognize glycolipid antigens presented on cluster of differentiation (CD)-1d molecules. When their ligands are presented in concert with peptides, iNKT cells can provide T-cell help, 'licensing' APCs to augment peptide-specific T-cell and antibody responses. We discuss the potential benefits and limitations of exploiting iNKT cells as 'universal helpers' to enhance vaccine responses for the treatment and prevention of cancer and infectious diseases.

Small-Molecule Carbohydrate-Based Immunostimulants

In this review, we discuss small-molecule, carbohydrate-based immunostimulants that target Toll-like receptor 4 (TLR-4) and cluster of differentiation 1D (CD1d) receptors. The design and use of these molecules in immunotherapy as well as results from their use in clinical trials are described. How these molecules work and their utilization as vaccine adjuvants are also discussed. Future applications and extensions for the use of these analogues as therapeutic agents will be outlined.

Novel Types of Small RNA Exhibit Sequence- and Target-dependent Angiogenesis Suppression Without Activation of Toll-like Receptor 3 in an Age-related Macular Degeneration (AMD) Mouse Model

RNA interference (RNAi) has become a powerful tool for suppressing gene expression in vitro and in vivo. A great deal of evidence has demonstrated the potential for the use of synthetic small interfering RNAs (siRNAs) as therapeutic agents. However, the application of siRNA to clinical medicine is still limited, mainly due to sequence-independent suppression of angiogenesis mediated by Toll-like receptor 3 (TLR3). Here, we describe novel types of synthetic RNA, named nkRNA and PnkRNA, that exhibit sequence-specific gene silencing through RNAi without activating TLRs or RIG-I–like receptor signaling. In addition, we confirmed the therapeutic effect for the novel types of RNA in an animal model of age-related macular degeneration (AMD) without retinal degeneration. These data indicate that nkRNA and PnkRNA are of great potential utility as therapies against blinding choroidal neovascularization due to AMD.

Co-operation of α-galactosylceramide-loaded tumour cells and TLR9 agonists induce potent anti-tumour responses in a murine colon cancer model

Dendritic cells (DCs) and invariant natural killer T (iNKT) cells play important roles in linking innate immunity and adaptive immunity. Mature DCs activated by Toll-like receptor (TLR) agonists directly activate iNKT cells and the iNKT ligand α-galactosylceramide (α-Galcer) can induce DC maturation, resulting in enhanced protective immune responses. In the present study, we aimed to boost anti-tumour immunity in a murine colon cancer model by synergizing DCs and iNKT cells using α-Galcer-loaded tumour cells (tumour-Gal) and the TLR9 agonist cytosine-phosphorothioate-guanine (CpG1826). The vaccine strategy was sufficient to inhibit growth of established tumours and prolonged survival of tumour-bearing mice. Importantly, the immunization induced an adaptive memory immune response as the survivors from primary tumour inoculations were resistant to a tumour re-challenge. Furthermore, injection of tumour-Gal with CpG1826 resulted in iNKT cell activation and DC maturation as defined by interferon (IFN)-γ secretion by iNKT, natural killer (NK) cells and interleukin (IL)-12 by DCs. Immunohistochemistry analysis revealed that cluster of differentiation (CD)4(+) T-cells and CD8(+) T-cells played important roles in anti-tumour immunity. Additionally, the vaccine redirected Th2 (T-helper cell type 2) responses toward Th1 (T-helper cell type 1) responses with increases in IL-2, IFN-γ expression and decreases in IL-4 and IL-5 expression after immunization with tumour-Gal with CpG1826. Taken together, our results demonstrated a novel vaccination by synergizing tumour-Gal and CpG1826 against murine colon cancer, which can be further developed as tumour-specific immunotherapy against human cancer.

Activated NKT Cells Can Condition Different Splenic Dendritic Cell Subsets To Respond More Effectively to TLR Engagement and Enhance Cross-Priming

The function of dendritic cells (DCs) can be modulated through multiple signals, including recognition of pathogen-associated molecular patterns, as well as signals provided by rapidly activated leukocytes in the local environment, such as innate-like T cells. In this article, we addressed the possibility that the roles of different murine DC subsets in cross-priming CD8(+) T cells can change with the nature and timing of activatory stimuli. We show that CD8α(+) DCs play a critical role in cross-priming CD8(+) T cell responses to circulating proteins that enter the spleen in close temporal association with ligands for TLRs and/or compounds that activate NKT cells. However, if NKT cells are activated first, then CD8α(-) DCs become conditioned to respond more vigorously to TLR ligation, and if triggered directly, these cells can also contribute to priming of CD8(+) T cell responses. In fact, the initial activation of NKT cells can condition multiple DC subsets to respond more effectively to TLR ligation, with plasmacytoid DCs making more IFN-α and both CD8α(+) and CD8α(-) DCs manufacturing more IL-12. These results suggest that different DC subsets can contribute to T cell priming if provided appropriately phased activatory stimuli, an observation that could be factored into the design of more effective vaccines.

NK and NKT Cell Depletion Alters the Outcome of Experimental Pneumococcal Pneumonia: Relationship with Regulation of Interferon-γ Production

Background. Natural killer (NK) and natural killer T (NKT) cells contribute to the innate host defense but their role in bacterial sepsis remains controversial. Methods. C57BL/6 mice were infected intratracheally with 5 × 10(5) cfu of Streptococcus pneumoniae. Animals were divided into sham group (Sham); pretreated with isotype control antibody (CON) group; pretreated with anti-asialo GM1 antibody (NKd) group; and pretreated with anti-CD1d monoclonal antibody (NKTd) group before bacterial challenge. Serum and tissue samples were analyzed for bacterial load, cytokine levels, splenocyte apoptosis rates, and cell characteristics by flow cytometry. Splenocyte miRNA expression was also analyzed and survival was assessed. Results. NK cell depletion prolonged survival. Upon inhibition of NKT cell activation, spleen NK (CD3-/NK1.1+) cells increased compared to all other groups. Inhibition of NKT cell activation led to higher bacterial loads and increased levels of serum and splenocyte IFN-γ. Splenocyte miRNA analysis showed that miR-200c and miR-29a were downregulated, while miR-125a-5p was upregulated, in anti-CD1d treated animals. These changes were moderate after NK cell depletion. Conclusions. NK cells appear to contribute to mortality in pneumococcal pneumonia. Inhibition of NKT cell activation resulted in an increase in spleen NK (CD3-/NK1.1+) cells and a higher IFN-γ production, while altering splenocyte miRNA expression.

Inhibition of indoleamine 2,3-dioxygenase activity enhances the anti-tumour effects of a Toll-like receptor 7 agonist in an established cancer model

Toll-like receptor (TLR) agonists have been shown to have anti-tumour activity in basic research and clinical studies. However, TLR agonist monotherapy does not sufficiently eliminate tumours. Activation of the innate immune response by TLR agonists is effective at driving adaptive immunity via interleukin-12 (IL-12) or IL-1, but is counteracted by the simultaneous induction of immunosuppressive cytokines and other molecules, including IL-10, transforming growth factor-β, and indoleamine 2,3-dioxygenase (IDO). In the present study, we evaluated the anti-cancer effect of the TLR7 agonist, imiquimod (IMQ), in the absence of IDO activity. The administration of IMQ in IDO knockout (KO) mice inoculated with tumour cells significantly suppressed tumour progression compared with that in wild-type (WT) mice, and improved the survival rate. Moreover, injection with IMQ enhanced the tumour antigen-specific T helper type 1 response in IDO-KO mice with tumours. Combination therapy with IMQ and an IDO inhibitor also significantly inhibited tumour growth. Our results indicated that the enhancement of IDO expression with TLR agonists in cancer treatment might impair host anti-tumour immunity while the inhibition of IDO could enhance the therapeutic efficacy of TLR agonists via the increase of T helper type 1 immune response.

α-Galactosylceramide stimulates splenic lymphocyte proliferation in vitro and increases antibody production in vivo in late neonatal-age mice

The neonatal stage is characterized by weak responses to various infections and vaccines, thus the development of efficient formulas to improve vaccine effectiveness is of high priority. The glycolipid alpha galactosylceramide (αGalCer) is known as a potent immune modulator due mainly to natural killer (NK) T cell activation. Using a mouse tetanus toxoid (TT) immunization model, we observed that neonatal mice given αGalCer at the time of primary immunization on postnatal day (pnd) 17 had a significantly higher TT-specific immunoglobulin (Ig)M response as well as a memory IgG response, while αGalCer given on pnd 7 resulted in only marginal boosting. Consistently, immunostaining of the spleen sections from αGalCer-treated pnd 17 immunized neonates showed a higher number of Ki67(+) cells in the splenic germinal centre area, suggesting a stronger response after immunization. In-vitro kinetic studies revealed that spleen cells from newborn to pnd 7 neonates did not respond to αGalCer stimulation, whereas cell proliferation was increased markedly by αGalCer after pnd 7, and became dramatic around neonatal pnd 17-18, which was accompanied by increased B, T and NK T cell populations in the spleen. In addition, in pnd 17 spleen cells, αGalCer significantly stimulated the production of NK T cytokines, interleukin (IL)-4 and interferon (IFN)-γ, and promoted the proliferation of CD23(+) B cells, a subset of B cells enriched in germinal centres. These data suggest that αGalCer is an effective immune stimulus in the late neonatal stage, and thus may be useful in translational studies to test as a potential adjuvant to achieve a more efficient response to immunization.

Dendritic cell SIRT1-HIF1α axis programs the differentiation of CD4+ T cells through IL-12 and TGF-β1

The differentiation of naive CD4(+) T cells into distinct lineages plays critical roles in mediating adaptive immunity or maintaining immune tolerance. In addition to being a first line of defense, the innate immune system also actively instructs adaptive immunity through antigen presentation and immunoregulatory cytokine production. Here we found that sirtuin 1 (SIRT1), a type III histone deacetylase, plays an essential role in mediating proinflammatory signaling in dendritic cells (DCs), consequentially modulating the balance of proinflammatory T helper type 1 (TH1) cells and antiinflammatory Foxp3(+) regulatory T cells (T(reg) cells). Genetic deletion of SIRT1 in DCs restrained the generation of T(reg) cells while driving TH1 development, resulting in an enhanced T-cell-mediated inflammation against microbial responses. Beyond this finding, SIRT1 signaled through a hypoxia-inducible factor-1 alpha (HIF1α)-dependent pathway, orchestrating the reciprocal TH1 and T(reg) lineage commitment through DC-derived IL-12 and TGF-β1. Our studies implicates a DC-based SIRT1-HIF1α metabolic checkpoint in controlling T-cell lineage specification.

“Pruning of biomolecules and natural products (PBNP)”: an innovative paradigm in drug discovery

Smart Schneider: ‘Nature’ is the most intelligent tailor with an ability to utilize the resources. Researchers are still at an infant stage learning this art. The present review highlights some of the man made pruning of bio-molecules and NPs (PBNP) in finding chemicals with a better therapeutic index.

Combination therapy with α-galactosylceramide and a Toll-like receptor agonist exerts an augmented suppressive effect on lung tumor metastasis in a mouse model

α-galactosylceramide (GalCer), which is a natural killer T (NKT) cell ligand, has been reported to exert therapeutic effects against cancer in humans and mice. Toll-like receptor (TLR) agonists systemically or locally boost antitumor efficacy in mouse cancer models. In our previous study, the co-administration of GalCer and a TLR agonist synergistically enhanced interferon-γ (IFN-γ) production in mouse splenocytes in vitro and in vivo. The increased IFN-γ production promoted a tumor antigen-specific Th1 response. Therefore, co-treatment with GalCer and a TLR agonist is expected to exert an enhanced antitumor effect. In the present study, we examined the effect of GalCer and lipopolysaccharide (LPS) combination therapy in a mouse lung-metastasis model. GalCer and LPS combination therapy markedly decreased the number of lung metastatic tumor nodes. Co-treatment with GalCer and LPS enhanced the mRNA expression of CXCL9 and CXCL10 in mediastinal lymph nodes (MLNs) and increased the number of CD8+ cells in the MLNs. Furthermore, the depletion of CD8+ T cells canceled the antitumor effect of GalCer and LPS combination therapy. Thus, GalCer and LPS combination therapy significantly enhanced tumor antigen-specific immune responses and suppressed tumor growth in a mouse lung-metastasis model.