Toll-like receptors: the swiss army knife of immunity and vaccine development

Immunotherapy in clinical canine leishmaniosis: a comparative update

Leishmaniosis due to Leishmania infantum is a complex infection that can affect both humans and dogs, and present a wide range of clinical signs and clinicopathological abnormalities. The conventional treatment of this disease is challenging due to the fact that complete parasitological cure commonly does not occur. Furthermore, treatment of the disease with the conventionally used drugs has several shortcomings. These include the need for long-term treatment, side effects and the formation of drug resistance. Moreover, it is important to highlight that the host immune responses play a crucial role in the outcome of this infection. For this reason, the use of immunotherapy in clinical leishmaniosis to improve the result of treatment with the conventional anti-leishmanial drugs by enhancing the immune response is imperative. The aim of this review is to provide a comparative overview of the wide range of immunotherapeutical approaches and strategies for the treatment of L. infantum infection in animals focusing on dogs.

New Rabies Vaccines for Use in Humans

Although vaccines are available, rabies still claims more than 55,000 human lives each year. In most cases, rabies vaccines are given to humans after their exposure to a rabid animal; pre-exposure vaccination is largely reserved for humans at high risk for contacts with the virus. Most cases of human rabies are transmitted by dogs. Dog rabies control by mass canine vaccination campaigns combined with intensive surveillance programs has led to a decline of human rabies in many countries but has been unsuccessful in others. Animal vaccination programs are also not suited to control human rabies caused by bat transmission, which is common in some Central American countries. Alternatively, or in addition, more widespread pre-exposure vaccination, especially in highly endemic remote areas, could be implemented. With the multiple dose regimens of current vaccines, pre-exposure vaccination is not cost effective for most countries and this warrants the development of new rabies vaccines, which are as safe as current vaccines, but achieve protective immunity after a single dose, and most importantly, are less costly. This chapter discusses novel rabies vaccines that are in late stage pre-clinical testing or have undergone clinical testing and their potential for replacing current vaccines.

TIR-TLR7 as a Molecular Adjuvant: Simultaneous Enhancing Humoral and Cell-Mediated Immune Responses Against Inactivated Infectious Bursal Disease Virus

Despite the robust induction of humoral immune responses, a limitation of many adjuvants is their weak stimulation of cellular immunity. The development of synthetic gene-encoding adjuvants for simultaneous induction of both humoral and cell-mediated immune responses is under study. In this study, we examined the impact of toll/interleukin-1 receptor (TIR) domain of toll-like receptor 7 (TLR7) as molecular adjuvants on potency of inactivated infectious bursal disease (IBD) vaccines. A total of 60 specific pathogen-free week-old chicks were randomized grouped to receive either TIR-TLR7-adjuvanted IBD-inactivated vaccine or inactivated IBD antigen along with an unvaccinated control. Serum antibody titers were measured to estimate the humoral immunity, as well as lymphocyte proliferation activity for cellular immune responses. The protection was estimated after challenge with a very virulent IBD virus (IBDV) strain at 4 weeks postvaccination. The results indicated that one dose of IBD/TIR-TLR7 vaccine induced specific antibody responses, whereas a lower response after administration of inactivated IBD antigen was observed. The stimulation of splenocytes results indicated that the TIR-TLR7 adjuvanted IBD vaccine is capable of modulating cell-mediated immune response in treated chickens. A full protection against IBDV infection was achieved by injection of one dose IBD/TIR-TLR7 vaccine in the challenge trial. This study demonstrated that codelivery of TIR-TLR7 with inactivated IBD antigen resulted in simultaneous enhancing immune responses against IBD.

Activation of Toll-like Receptor 2 (TLR2) induces Interleukin-6 trans-signaling

Signaling of the pleiotropic cytokine Interleukin-6 (IL-6) via its soluble IL-6R (sIL-6R) has been termed trans-signaling and is thought to be responsible for the pro-inflammatory properties of IL-6. The sIL-6R can be generated by alternative mRNA splicing or proteolytic cleavage of the membrane-bound IL-6R. However, which stimuli induce sIL-6R release and which endogenous signaling pathways are required for this process is poorly understood. Here, we show that activation of Toll-like receptor 2 (TLR2) on primary human peripheral blood mononuclear cells (PBMCs) and on the monocytic cell line THP-1 induces expression and secretion of IL-6 and the generation of sIL-6R. We show by flow cytometry that monocytes are a PBMC subset that expresses TLR2 in conjunction with the IL-6R and are the major cellular source for both IL-6 and sIL-6R. Mechanistically, we find that the metalloproteases ADAM10 and ADAM17 are responsible for cleavage of the IL-6R and therefore sIL-6R generation. Finally, we identify the Extracellular-signal Regulated Kinase (ERK) cascade as a critical pathway that differentially regulates both IL-6 and sIL-6R generation in monocytes.

A peptide-based vaccine for Mycobacterium avium subspecies paratuberculosis

Recent efforts to develop a live attenuated vaccine against Mycobacterium avium subsp. paratuberculosis (Map), the causative agent of Johne's disease (JD), revealed relA is important in Map virulence. Deletion of the relA gene impairs the ability of Map to establish a persistent infection. Analysis of the basis for this observation revealed infection with a relA deletion mutant (ΔrelA) elicits development of cytotoxic CD8 T cells (CTL) with the ability to kill intracellular bacteria. Further analysis of the recall response elicited by ΔrelA vaccination showed a 35 kDa membrane peptide (MMP) is one of the targets of the immune response, suggesting it might be possible to develop a peptide-based vaccine based on MMP. To explore this possibility, ex vivo vaccination studies were conducted with MMP alone and incorporated into a nanoparticle (NP) vector comprised of poly (D, L-lactide-co-glycolide) and monophosphoryl lipid A (PLGA/MPLA). As reported, ex vivo vaccination studies showed CD8 CTL were elicited with classic and monocyte derived dendritic cells (cDC and MoDC) pulsed with MMP alone and incorporated into a PGLA/MPLA vector. Incorporation of MMP into a NP vector enhanced the ability of CD8 CTL to kill intracellular bacteria. The findings indicate incorporation of MMP into a PGLA/MPLA nanoparticle vector is one of the possible ways to develop a MMP based vaccine for Johne's disease.

Geometry of a TLR2-Agonist-Based Adjuvant Can Affect the Resulting Antigen-Specific Immune Response

Targeted delivery of otherwise nonimmunogenic antigens to Toll-like receptors (TLRs) expressed on dendritic cells (DCs) has proven to be an effective means of improving immunogenicity. For this purpose, we have used a branched cationic lipopeptide, R₄Pam₂Cys, which is an agonist for TLR2 and enables electrostatic association with antigen for this purpose. Here, we compare the immunological properties of ovalbumin formulated with different geometrical configurations of R₄Pam₂Cys. Our results demonstrate that notwithstanding the presence of the same adjuvant, branched forms of R₄Pam₂Cys are more effective at inducing immune responses than are linear geometries. CD8⁺ T-cell-mediated responses are particularly improved, resulting in significantly higher levels of antigen-specific cytokine secretion and cytolysis of antigen-bearing target cells in vivo. The results correlate with the ability of branched R₄Pam₂Cys conformations to encourage higher levels of DC maturation and facilitate superior antigen uptake, leading to increased production of proinflammatory cytokines. These differences are not attributable to particle size because both branched and linear lipopeptides associate with antigen-forming complexes of similar size, but rather the ability of branched lipopeptides to induce more efficient TLR2-mediated cell signaling. Branched lipopeptides are also more resistant to trypsin-mediated proteolysis, suggesting greater stability than their linear counterparts. The branched lipopeptide facilitates presentation of antigen more efficiently to CD8⁺ T cells, resulting in rapid cell division and upregulation of early cell surface activation markers. These results as well as cognate recognition of Pam₂Cys by TLR2 indicate that the adjuvant's efficiency is also dependent on its geometry.

The Role of Toll-Like Receptors in Oncotherapy

Toll-like receptors (TLRs) are associated with tumor growth and immunosuppression, as well as apoptosis and immune system activation. TLRs can activate apoptosis and innate and adaptive immunity pathways, which can be pharmacologically targeted for the development of anticancer oncotherapies. Several studies and clinical trials indicate that TLR agonists are promising adjuvants or elements of novel therapies, particularly when used in conjunction with chemotherapy or radiotherapy. An increasing number of studies suggest that the activation of TLRs in various cancer types is related to oncotherapy; however, before this finding can be applied to clinical practice, additional studies are required. Research suggests that TLR agonists may have potential applications in cancer therapy; nevertheless, because TLR signaling can also promote tumorigenesis, a critical and comprehensive evaluation of TLR action is warranted. This review focuses on recent studies that have assessed the strengths and weaknesses of utilizing TLR agonists as potential anticancer agents.

Optimization of peptide-based cancer vaccine compositions, by sequential screening, using versatile liposomal platform

Therapeutic cancer vaccines need thoughtful design to efficiently deliver appropriate antigens and adjuvants to the immune system. In the current study, we took advantage of the versatility of a liposomal platform to conceive and customize vaccines containing three elements needed for the induction of efficient antitumor immunity: i) a CD4 epitope peptide able to activate CD4⁺ T helper cells, ii) a CD8 tumor-specific epitope peptide recognized by CD8⁺ T cytotoxic cells and iii) Pattern Recognition Receptor (PRR) agonists which stand as adjuvants. Each type of component, conjugated to liposomes, was evaluated individually by comparing their vaccine efficacy after immunization of naïve mice. These screening steps resulted in the optimization of three liposomal constructs bearing a peptide from HA influenza virus protein as CD4 epitope, a peptide from HPV16 E7 oncoprotein as CD8 epitope and TLR4, TLR2/6 or NOD1 agonists as adjuvant, which displayed antitumor efficiency against a mouse model of disseminated tumors transformed by HPV16. Our results validated the interest of our customizable liposomal platform as delivery system for cancer vaccination. We also demonstrated its interest as tool for vaccine design allowing the strategical selection of components, and the evaluation of epitope-adjuvant association.

Immunostimulatory Phosphatidylmonogalactosyldiacylglycerols (PGDG) from the Marine Diatom Thalassiosira weissflogii: Inspiration for a Novel Synthetic Toll-Like Receptor 4 Agonist

An unprecedented phosphatidylmonogalactosyldiacylglycerol pool (PGDG, 1) rich in polyunsaturated fatty acids was isolated from the marine diatoms Thalassiosira weissflogii. Here we report for the first time the NMR characterization of this rare lipid from marine organisms along with a synthetic strategy for the preparation of a PGDG analog (2). PGDG 1 exhibited immunostimulatory activity in human dendritic cells (DCs) and the synthetic PGDG 2 was prepared to explore its mechanism of action. A Toll-like receptor-4 (TLR-4) agonistic activity was evidenced in human and murine DCs underlying the antigen-specific T-cell activation of this class of molecules.

RNA is taking its Toll: Impact of RNA-specific Toll-like receptors on health and disease

RNA-sensing Toll-like receptors (TLRs) are often described as antiviral receptors of the innate immune system. However, the past decade has shown that the function and relevance of these receptors are far more complex. They were found to be essential for the detection of various bacterial, archaeal, and eukaryotic microorganisms and facilitate the discrimination between dead and living microbes. The cytokine and interferon response profile that is triggered has the potential to improve the efficacy of next-generation vaccines and may prevent the development of asthma and allergy. Nevertheless, the ability to recognize foreign RNA comes with a cost as also damaged host cells can release nucleic acids that might induce an inappropriate immune response. Thus, it is not surprising that RNA-sensing TLRs play a key role in various autoimmune diseases. However, promising new inhibitors and antagonists are on the horizon to improve their treatment.

Pharmacophore-based virtual screening approach for identification of potent natural modulatory compounds of human Toll-like receptor 7

Toll-like receptor 7 (TLR7) is a transmembrane glycoprotein playing very crucial role in the signaling pathways involved in innate immunity and has been demonstrated to be useful in fighting against infectious disease by recognizing viral ssRNA & specific small molecule agonists. In order to find novel human TLR7 (hTLR7) modulators, computational ligand-based pharmacophore modeling approach was used to identify the molecular chemical features required for the modulation of hTLR7 protein. A training set of 20 TLR7 agonists with their known experimental activity was used to create pharmacophore model using 3D-QSAR pharmacophore generation (HypoGen algorithm) module in Discovery Studio. The best developed hypothesis consists of four pharmacophoric features namely, one hydrogen bond donor (HBD), one ring aromatic (RA), and two hydrophobic (HY) character. The developed hypothesis was then validated by different methods such as cost analysis, test set method, and Fischer's test method for consistency. Hence, this validated model was further employed for screening of natural hit compounds from InterBioScreen Natural product database, consisting of more than 60,000 natural compounds and derivatives. The screened hit compounds were subsequently filtered by Lipinski's rule of 5, ADME and toxicity parameters and molecular docking studies to remove the false positive rates. Finally, molecular docking analysis led to identification of the (3a'S,6a'R)-3'-(3,4-dihydroxybenzyl)-5'-(3,4-dimethoxyphenethyl)-5-ethyl-3',3a'-dihydro-2'H-spiro[indoline-3,1'-pyrrolo[3,4-c]pyrrole]-2,4',6'(5'H,6a'H)-trione (Compound ID: STOCK1N-65837) as potent hTLR7 modulator due to its better docking score and molecular interactions compared to other compounds. The result of virtual screening was further validated using molecular dynamics (MD) simulation analysis. Thus, a 30 ns MD simulation analysis revealed high stability and effective binding of STOCK1N-65837 within the binding site of hTLR7. Therefore, the present study provides confidence for the utility of the selected chemical feature based pharmacophore model to design novel TLR7 modulators with desired biological activity.

Cancer Immunotherapy of TLR4 Agonist-Antigen Constructs Enhanced with Pathogen-Mimicking Magnetite Nanoparticles and Checkpoint Blockade of PD-L1

Despite the tremendous potential of Toll-like receptor 4 (TLR4) agonists in vaccines, their efficacy as monotherapy to treat cancer has been limited. Only some lipopolysaccharides (LPS) isolated from particular bacterial strains or structures like monophosphoryl lipid A (MPLA) derived from lipooligosaccharide (LOS), avoid toxic overactivation of innate immune responses while retaining adequate immunogenicity to act as adjuvants. Here, different LOS structures are incorporated into nanoparticle-filled phospholipid micelles for efficient vaccine delivery and more potent cancer immunotherapy. The structurally unique LOS of the plant pathogen Xcc is incorporated into phospholipid micelles encapsulating iron oxide nanoparticles, producing stable pathogen-mimicking nanostructures suitable for targeting antigen presenting cells in the lymph nodes. The antigen is conjugated via a hydrazone bond, enabling rapid, easy-to-monitor and high-yield antigen ligation at low concentrations. The protective effect of these constructs is investigated against a highly aggressive model for tumor immunotherapy. The results show that the nanovaccines lead to a higher-level antigen-specific cytotoxic T lymphocyte (CTL) effector and memory responses, which when combined with abrogation of the immunosuppressive programmed death-ligand 1 (PD-L1), provide 100% long-term protection against repeated tumor challenge. This nanovaccine platform in combination with checkpoint inhibition of PD-L1 represents a promising approach to improve the cancer immunotherapy of TLR4 agonists.

Norovirus antivirals: Where are we now?

Human noroviruses inflict a significant health burden on society and are responsible for approximately 699 million infections and over 200 000 estimated deaths worldwide each year. Yet despite significant research efforts, approved vaccines or antivirals to combat this pathogen are still lacking. Safe and effective antivirals are not available, particularly for chronically infected immunocompromised individuals, and for prophylactic applications to protect high‐risk and vulnerable populations in outbreak settings. Since the discovery of human norovirus in 1972, the lack of a cell culture system has hindered biological research and antiviral studies for many years. Recent breakthroughs in culturing human norovirus have been encouraging, however, further development and optimization of these novel methodologies are required to facilitate more robust replication levels, that will enable reliable serological and replication studies, as well as advances in antiviral development. In the last few years, considerable progress has been made toward the development of norovirus antivirals, inviting an updated review. This review focuses on potential therapeutics that have been reported since 2010, which were examined across at least two model systems used for studying human norovirus or its enzymes. In addition, we have placed emphasis on antiviral compounds with a defined chemical structure. We include a comprehensive outline of direct‐acting antivirals and offer a discussion of host‐modulating compounds, a rapidly expanding and promising area of antiviral research.

Costimulation through TLR2 Drives Polyfunctional CD8+ T Cell Responses

Optimal T cell activation requires Ag recognition through the TCR, engagement of costimulatory molecules, and cytokines. T cells can also directly recognize danger signals through the expression of TLRs. Whether TLR ligands have the capacity to provide costimulatory signals and enhance Ag-driven T cell activation is not well understood. In this study, we show that TLR2 and TLR7 ligands potently lower the Ag threshold for cytokine production in T cells. To investigate how TLR triggering supports cytokine production, we adapted the protocol for flow cytometry-based fluorescence in situ hybridization to mouse T cells. The simultaneous detection of cytokine mRNA and protein with single-cell resolution revealed that TLR triggering primarily drives de novo mRNA transcription. Ifng mRNA stabilization only occurs when the TCR is engaged. TLR2-, but not TLR7-mediated costimulation, can enhance mRNA stability at low Ag levels. Importantly, TLR2 costimulation increases the percentage of polyfunctional T cells, a hallmark of potent T cell responses. In conclusion, TLR-mediated costimulation effectively potentiates T cell effector function to suboptimal Ag levels.

Therapeutic potential of pteridine derivatives: A comprehensive review

Pteridines are aromatic compounds formed by fused pyrazine and pyrimidine rings. Many living organisms synthesize pteridines, where they act as pigments, enzymatic cofactors, or immune system activation molecules. This variety of biological functions has motivated the synthesis of a huge number of pteridine derivatives with the aim of studying their therapeutic potential. This review gathers the state-of-the-art of pteridine derivatives, describing their biological activities and molecular targets. The antitumor activity of pteridine-based compounds is one of the most studied and advanced therapeutic potentials, for which several molecular targets have been identified. Nevertheless, pteridines are also considered as very promising therapeutics for the treatment of chronic inflammation-related diseases. On the other hand, many pteridine derivatives have been tested for antimicrobial activities but, although some of them resulted to be active in preliminary assays, a deeper research is needed in this area. Moreover, pteridines may be of use in the treatment of many other diseases, such as diabetes, osteoporosis, ischemia, or neurodegeneration, among others. Thus, the diversity of the biological activities shown by these compounds highlights the promising therapeutic use of pteridine derivatives. Indeed, methotrexate, pralatrexate, and triamterene are Food and Drug Administration approved pteridines, while many others are currently under study in clinical trials.

Concise Review: TLR Pathway-miRNA Interplay in Mesenchymal Stromal Cells: Regulatory Roles and Therapeutic Directions

Mesenchymal stromal cells (MSCs) deploy Toll-like receptors (TLRs) to respond to exogenous and endogenous signals. Activation of TLR pathways in MSCs alters their inflammatory profile and immunomodulatory effects on cells from both the innate and adaptive immune systems. Micro-RNAs (miRNAs), whose expression is modulated by TLR activation, can regulate inflammatory responses by targeting components of the TLR signaling pathways either in MSCs or in the cells with which they interact. Here, we review how the miRNA-TLR pathway axis can regulate the immunomodulatory functions of MSCs, including their interactions with monocytes/macrophages and natural killer cells, and discuss the therapeutic implications for MSC-based therapies. Stem Cells 2018;36:1655-1662.

Trial Watch: Toll-like receptor agonists in cancer immunotherapy

Toll-like receptor (TLR) agonists demonstrate therapeutic promise as immunological adjuvants for anticancer immunotherapy. To date, three TLR agonists have been approved by US regulatory agencies for use in cancer patients. Additionally, the potential of hitherto experimental TLR ligands to mediate clinically useful immunostimulatory effects has been extensively investigated over the past few years. Here, we summarize recent preclinical and clinical advances in the development of TLR agonists for cancer therapy.

Establishment of a novel safety assessment method for vaccine adjuvant development

Vaccines effectively prevent infectious diseases. Many types of vaccines against various pathogens that threaten humans are currently in widespread use. Recently, adjuvant adaptation has been attempted to activate innate immunity to enhance the effectiveness of vaccines. The effectiveness of adjuvants for vaccinations has been demonstrated in many animal models and clinical trials. Although a highly potent adjuvant tends to have high effectiveness, it also has the potential to increase the risk of side effects such as pain, edema, and fever. Indeed, highly effective adjuvants, such as poly(I:C), have not been clinically applied due to their high risks of toxicity in humans. Therefore, the task in the field of adjuvant development is to clinically apply highly effective and non- or low-toxic adjuvant-containing vaccines. To resolve this issue, it is essential to ensure a low risk of side effects and the high efficacy of an adjuvant in the early developmental phases. This review summarizes the theory and history of the current safety assessment methods for adjuvants, using the inactivated influenza vaccine as a model. Our novel method was developed as a system to judge the safety of a candidate compound using biomarkers identified by genomic technology and statistical tools. A systematic safety assessment tool for adjuvants would be of great use for predicting toxicity during novel adjuvant development, screening, and quality control.

Adjuvant Potential of Poly-α-l-Glutamine from the Cell Wall of Mycobacterium tuberculosis

Novel adjuvants are in demand for improving the efficacy of human vaccines. The immunomodulatory properties of Mycobacterium tuberculosis cell wall components have been highlighted in the formulation of complete Freund's adjuvant (CFA). We have explored the adjuvant potential of poly-α-l-glutamine (PLG), a lesser-known constituent of the pathogenic mycobacterial cell wall. Immune parameters indicated that the adjuvant potency of PLG was statistically comparable to that of CFA and better than that of alum in the context of H1 antigen (Ag85B and ESAT-6 fusion). At 1 mg/dose, PLG augmented the immune response of Ag85B, BP26, and protective antigen (PA) by increasing serum antibodies and cytokines in the culture supernatant of antigen-stimulated splenocytes. PLG modulated the humoral response of vaccine candidate ESAT-6, eliciting significantly higher levels of total IgG and isotypes (IgG1, IgG2a, and IgG2b). Additionally, the splenocytes from PLG-adjuvanted mice displayed a robust increase in the Th1-specific gamma interferon, tumor necrosis factor alpha, interleukin-2 (IL-2), Th2-specific IL-6 and IL-10, and Th17-specific IL-17A cytokines upon antigenic stimulation. PLG improved the protective efficacy of ESAT-6 by reducing bacillary load in the lung and spleen as well as granuloma formation, and it helped in maintaining vital health parameters of mice challenged with M. tuberculosis The median survival time of PLG-adjuvanted mice was 205 days, compared to 146 days for dimethyl-dioctadecyl ammonium bromide-monophosphoryl lipid A (DDA-MPL)-vaccinated groups and 224 days for Mycobacterium bovis BCG-vaccinated groups. PLG enhanced the efficiency of the ESAT-6 vaccine to the level of BCG and better than that of DDA-MPL (P < 0.05), with no ill effect in C57BL/6J mice. Our results propose that PLG is a promising adjuvant candidate for advanced experimentation.

Toward the development of a one-dose classical swine fever subunit vaccine: antigen titration, immunity onset, and duration of immunity

Highly contagious classical swine fever (CSF) remains a major trade and health problem in the pig industry, resulting in large economic losses worldwide. In CSF-endemic countries, attenuated CSF virus (CSFV) vaccines have been routinely used to control the disease. However, eradication of CSFV in a geographical area would require permanent reduction to zero presence of the virus. It is therefore of paramount importance to develop a safe, potent, and non-infectious CSF vaccine. We have previously reported on a cost-effective CSF E2 subunit vaccine, KNB-E2, which can protect against CSF symptoms in a single dose containing 75 µg of recombinant CSFV glycoprotein E2. In this study, we report on a series of animal studies undertaken to elucidate further the efficacy of KNB-E2. We found that pigs vaccinated with a single KNB-E2 dose containing 25 µg of recombinant CSFV glycoprotein E2 were protected from clinical symptoms of CSF. In addition, KNB-E2-mediated reduction of CSF symptoms was observed at two weeks post-vaccination and the vaccinated pigs continued to exhibit reduced CSF clinical signs when virus challenged at two months and four months post-vaccination. These results suggest that KNB-E2 effectively reduces CSF clinical signs, indicating the potential of this vaccine for safely minimizing CSF-related losses.

Toll-like receptors signaling network in pre-eclampsia: An updated review

Toll-like receptors (TLRs) are innate immune cells receptors. They are expressed on leukocytes, epithelial cells, and more particularly on placental immune cells and chorion trophoblast. Upregulation of innate immune response occurs during normal pregnancy, but its excessive activity is involved in the pathology of pregnancy complications including pregnancy-induced hypertension and pre-eclampsia (PE). The recent studies about the overmuch inflammatory responses and aberrant placentation are associated with increased expression of TLRs in PE patients. This review has tried to focus on the relationship between some activities of TLRs and the risk of preeclampsia development.

The Complex Puzzle of Interactions Among Functional Food, Gut Microbiota, and Colorectal Cancer

Colorectal cancer exerts a strong influence on the epidemiological panorama worldwide, and it is directly correlated to etiologic factors that are substantiated by genetic and environmental elements. This complex mixture of factors also has a relationship involving the structural dependence and composition of the gut microbiome, leading to a dysbacteriosis process that may evolve to serious modifications in the intestinal lining, eventually causing the development of a neoplasm. The gastrointestinal tract presents defense strategies and immunological properties that interfere in intestinal permeability, inhibiting the bacterial translocation, thus maintaining the integrity of intestinal homeostasis. The modulation of the intestinal microbiome and the extinction of risk factors associated with intestinal balance losses, especially of environmental factors, make cell and defense alterations impossible. This modulation may be conducted by means of functional foods in the diet, especially soluble fibers, polyunsaturated fatty acids, antioxidants and prebiotics that signal immunomodulatory effects in the intestinal microbiota, with preventive and therapeutic action for colorectal cancer. In summary, this review focuses on the importance of dietary modulation of the intestinal microbiota as an instrument for dysbacteriosis and, consequently, for the prevention of colorectal cancer, suggesting anticarcinogenic, and antiangiogenic properties. Among the intestinal modulating agents considered here are functional foods, especially flaxseed, oat and soy, composing a Bioactive Food Compound.

Enhancement of Antitumor Vaccination by Targeting Dendritic Cell-Related IL-10

Understanding mechanisms associated to dendritic cell (DC) functions has allowed developing new antitumor therapeutic vaccination strategies. However, these vaccines have demonstrated limited clinical results. Although the low immunogenicity of tumor antigens used and the presence of tumor-associated suppressive factors may in part account for these results, intrinsic vaccine-related factors may also be involved. Vaccines modulate DC functions by inducing activating and inhibitory signals that determine ensuing T cell responses. In this mini review, we focus on IL-10, inhibitory cytokine induced in DC upon vaccination, which defines a suppressive cell subset, discussing its implications as a potential target in combined vaccination immunotherapies.

Monophosphoryl Lipid A and Pam3Cys Prevent the Increase in Seizure Susceptibility and Epileptogenesis in Rats Undergoing Traumatic Brain Injury

Five percent of all epilepsy cases are attributed to traumatic brain injury (TBI), which are known as post-traumatic epilepsy (PTE). Finding preventive strategies for PTE is valuable. Remarkable feature of TBI is activation of microglia and subsequent neuroinflammation, which provokes epileptogenesis. The toll-like receptor agonists monophosphoryl lipid A (MPL) and tri-palmitoyl-S-glyceryl-cysteine (Pam3Cys) are safe, well-tolerated and effective adjuvants existing in prophylactic human vaccines. We examined the impact of early injection of MPL and Pam3Cys to rats, on the rate of kindled seizures acquisition following TBI. Rats received a single dose (1 µg/rat) of MPL or Pam3Cys through intracerebroventricular injection. 5 days later, trauma was exerted to temporo-parietal cortex of rats by controlled cortical impact device. After 24 h, traumatic rats underwent amygdala kindling. Brain level of the inflammatory cytokine tumor necrosis factor-alpha (TNF-α) was also measured in traumatic rats by immunoblotting. Compared to non-traumatic (sham-operated) rats, traumatic rats showed three times lower seizure threshold (133 ± 5 µA vs. 416.3 ± 16 µA, p < 0.001); about three times less number of stimuli to become kindled (5 ± 1 vs. 14 ± 2, p < 0.01); longer duration of kindled seizure parameters including entire seizure behavior, generalized seizures, and afterdischarges (p < 0.001); and a two times increase in the TNF-α level. MPL and Pam3Cys did not change kindling rate and the seizure parameters in sham-operated rats. The MPL- and Pam3Cys-pretreated traumatic rats displayed seizure threshold, speed of kindling, and duration of kindled seizure parameters, similar to the non-traumatic rats. Pretreatment by MPL and Pam3Cys prevented the increase in TNF-α level by trauma. Given that MPL and Pam3Cys currently have clinical use as well-tolerated vaccines with reliable safety, they have the potential to be used in prevention of PTE.

In silico analysis of Schmidtea mediterranea TIR domain-containing proteins

While genetic evidence points towards an absence of Toll-Like Receptors (TLRs) in Platyhelminthes, the Toll/IL-1 Receptor (TIR)-domains that drive the assembly of signalling complexes downstream TLR are present in these organisms. Here, we undertook the characterisation of the repertoire of TIR-domain containing proteins in Schmidtea mediterranea in order to gain valuable information on TLR evolution in metazoan. We report the presence of twenty proteins containing between one and two TIR domains. In addition, our phylogenetic-based reconstruction approach identified Smed-SARM and Smed-MyD88 as conserved TLR adaptors.

Immunoinformatics-aided design of a potential multi-epitope peptide vaccine against Leishmania infantum

Visceral leishmaniasis (VL) or kala-azar, the most severe form of the disease, is endemic in more than eighty countries across the world. To date, there is no approved vaccine against VL in the market. Recent advances in reverse vaccinology could be promising approach in designing the efficient vaccine for VL treatment. In this study, an efficient multi-epitope vaccine against Leishmania infantum, the causative agent of VL, was designed using various computational vaccinology methods. Potential immunodominant epitopes were selected from four antigenic proteins, including histone H1, sterol 24-c-methyltransferase (SMT), Leishmania-specific hypothetical protein (LiHy), and Leishmania-specific antigenic protein (LSAP). To enhance vaccine immunogenicity, two resuscitation-promoting factor of Mycobacterium tuberculosis, RpfE and RpfB, were employed as adjuvants. All the aforesaid segments were joined using proper linkers. Homology modeling, followed by refinement and validation was performed to obtain a high-quality 3D structure of designed vaccine. Docking analyses and molecular dynamics (MD) studies indicated vaccine/TLR4 complex was in the stable form during simulation time. In sum, we expect our designed vaccine is able to induce humoral and cellular immune responses against L. infantum, and may be promising medication for VL, after in vitro and in vivo immunological assays.

Adjuvant effect of the novel TLR1/TLR2 agonist Diprovocim synergizes with anti-PD-L1 to eliminate melanoma in mice

Successful cancer immunotherapy entails activation of innate immune receptors to promote dendritic cell (DC) maturation, antigen presentation, up-regulation of costimulatory molecules, and cytokine secretion, leading to activation of tumor antigen-specific cytotoxic T lymphocytes (CTLs). Here we screened a synthetic library of 100,000 compounds for innate immune activators using TNF production by THP-1 cells as a readout. We identified and optimized a potent human and mouse Toll-like receptor (TLR)1/TLR2 agonist, Diprovocim, which exhibited an EC₅₀ of 110 pM in human THP-1 cells and 1.3 nM in primary mouse peritoneal macrophages. In mice, Diprovocim-adjuvanted ovalbumin immunization promoted antigen-specific humoral and CTL responses and synergized with anti-PD-L1 treatment to inhibit tumor growth, generating long-term antitumor memory, curing or prolonging survival of mice engrafted with the murine melanoma B16-OVA. Diprovocim induced greater frequencies of tumor-infiltrating leukocytes than alum, of which CD8 T cells were necessary for the antitumor effect of immunization plus anti-PD-L1 treatment.

Dendritic Cell-Targeted Nanovaccine Delivery System Prepared with an Immune-Active Polymer

Targeting dendritic cells (DCs), either ex vivo (Ex. Sipuleucel-T) or in vivo, for stimulating cellular immunity has been a leading approach for cancer vaccines. We have rationally engineered a nanoparticle (NP)-based delivery system for vaccines (InAc-NPs) using inulin acetate (InAc) as the polymer to target DCs. The material and the antigen-encapsulated InAc-NPs (∼190 nm in diameter) were characterized for their physicochemical properties. As a potent vaccine adjuvant, InAc-NPs activated TLR4 on multiple immune cells, including DCs and primary swine and human cells, to secrete various cytokines as detected by enzyme-linked immunosorbent assay and quantitative polymerase chain reaction. In addition, InAc-NPs promoted the maturation of DCs as observed by a decreased phagocytic ability and enhanced capability to activate various maturation markers (MHC-I, MHC-II, CD40, and CD80) quantified using flow cytometry. In mice, the InAc-NPs produced strong serum antibody titers (total IgG, IgG1, and IgG2a) against the encapsulated antigen (ovalbumin) similar to complete Freund's adjuvant. Additionally, as a dose-sparing delivery system, antigen delivered through InAc-NPs generated higher antibody titers (IgG1, 1.57 times; IgG-total, 1.66 times; and IgG2a, 29.8 times) even at 100 times less antigen dose. High amounts of cytokines representing both humoral (IL4 and IL10) and cell-mediated (IL2 and IFN-γ) immunities were secreted from splenocytes of mice immunized with InAc-NPs. Importantly, InAc-NPs provided complete protection in 100% of the vaccinated mice from metastasis of intravenously injected melanoma cells (B₁₆-F₁₀) to lungs. In addition, the InAc-NPs were cleared from the injection site within 30 h of injection (in vivo imaging) and displayed no toxicity at the injection site (histology). The current study demonstrates that the multifunctional InAc-based nanovaccine delivery system has potential applications in cancer immunotherapy and delivering vaccines against various infectious diseases.

Membrane vesicles from Pseudomonas aeruginosa activate the noncanonical inflammasome through caspase-5 in human monocytes

Outer membrane vesicles (OMVs) are constitutively produced by Gram-negative bacteria both in vivo and in vitro. These lipid-bound structures carry a range of immunogenic components derived from the parent cell, which are transported into host target cells and activate the innate immune system. Recent advances in the field have shed light on some of the multifaceted roles of OMVs in host-pathogen interactions. In this study, we investigated the ability of OMVs from two clinically important pathogens, Pseudomonas aeruginosa and Helicobacter pylori, to activate canonical and noncanonical inflammasomes. P. aeruginosa OMVs induced inflammasome activation in mouse macrophages, as evidenced by "speck" formation, as well as the cleavage and secretion of interleukin-1β and caspase-1. These responses were independent of AIM2 and NLRC4 canonical inflammasomes, but dependent on the noncanonical caspase-11 pathway. Moreover, P. aeruginosa OMVs alone were able to activate the inflammasome in a TLR-dependent manner, without requiring an exogenous priming signal. In contrast, H. pylori OMVs were not able to induce inflammasome activation in macrophages. Using CRISPR/Cas9 knockout THP-1 cells lacking the human caspase-11 homologs, caspase-4 and -5,we demonstrated that caspase-5 but not caspase-4 is required for inflammasome activation by P. aeruginosa OMVs in human monocytes. In contrast, free P. aeruginosa lipopolysaccharide (LPS) transfected into cells induced inflammasome responses via caspase-4. This suggests that caspase-4 and caspase-5 differentially recognize LPS depending on its physical form or route of delivery into the cell. These findings have relevance to Gram-negative infections in humans and the use of OMVs as novel vaccines.

Dual TLR agonist nanodiscs as a strong adjuvant system for vaccines and immunotherapy

Recent studies have shown that certain combinations of Toll-like receptor (TLR) agonists can induce synergistic immune activation. However, it remains challenging to achieve such robust responses in vivo in a manner that is effective, facile, and amenable for clinical translation. Here, we show that MPLA, a TLR4 agonist, and CpG, a TLR9 agonist, can be efficiently co-loaded into synthetic high-density lipoprotein nanodiscs, forming a potent adjuvant system (ND-MPLA/CpG) that can be readily combined with a variety of subunit antigens, including proteins and peptides. ND-MPLA/CpG significantly enhanced activation of dendritic cells, compared with free dual adjuvants or nanodiscs delivering a single TLR agonist. Importantly, mice immunized with physical mixtures of protein antigens ND-MPLA/CpG generated strong humoral responses, including induction of IgG responses against protein convertase subtilisin/kexin 9 (PCSK9), leading to 17-30% reduction of the total plasma cholesterol levels. Moreover, ND-MPLA/CpG exerted strong anti-tumor efficacy in multiple murine tumor models. Compared with free adjuvants, ND-MPLA/CpG admixed with ovalbumin markedly improved antigen-specific CD8+ T cell responses by 8-fold and promoted regression of B16F10-OVA melanoma (P < 0.0001). Furthermore, ND-MPLA/CpG admixed with E7 peptide antigen elicited ~20% E7-specific CD8+ T cell responses and achieved complete regression of established TC-1 tumors in all treated animals. Taken together, our work highlights the simplicity, versatility, and potency of dual TLR agonist nanodiscs for applications in vaccines and cancer immunotherapy.

Harnessing T Follicular Helper Cell Responses for HIV Vaccine Development

Passive administration of broadly neutralizing antibodies (bNAbs) capable of recognizing a broad range of viral strains to non-human primates has led to protection from infection with chimeric SIV/HIV virus (SHIV). This data suggests that generating protective antibody responses could be an effective strategy for an HIV vaccine. However, classic vaccine approaches have failed so far to induce such protective antibodies in HIV vaccine trials. HIV-specific bNAbs identified in natural infection show high levels of somatic hypermutations, demonstrating that they underwent extensive affinity maturation. It is likely that to gain ability to recognize diverse viral strains, vaccine-induced humoral responses will also require complex, iterative maturation. T follicular helper cells (Tfh) are a specialized CD4+ T cell subset that provides help to B cells in the germinal center for the generation of high-affinity and long-lasting humoral responses. It is therefore probable that the quality and quantity of Tfh responses upon vaccination will impact development of bNAbs. Here, we review studies that advanced our understanding of Tfh differentiation, function and regulation. We discuss correlates of Tfh responses and bNAb development in natural HIV infection. Finally, we highlight recent strategies to optimize Tfh responses upon vaccination and their impact on prophylactic HIV vaccine research.

Stable Nanoemulsions for the Delivery of Small Molecule Immune Potentiators

Adjuvants are required to enhance immune responses to typically poorly immunogenic recombinant antigens. Toll-like receptor agonists (TLRa) have been widely evaluated as adjuvants because they activate the innate immune system. Currently, licensed vaccines adjuvanted with TLRa include the TLR4 agonist monophosphoryl lipid, while additional TLRa are in clinical development. Unfortunately, naturally derived TLRa are often complex and heterogeneous entities, which brings formulation challenges. Consequently, the use of synthetic small-molecule TLRa has significant advantages because they are well-defined discrete molecules, which can be chemically modified to modulate their physicochemical properties. We previously described the discovery of a family of TLR7 agonists based on a benzonaphthyridine scaffold. In addition, we described how Alum could be used to deliver these synthetic TLRa. An alternative adjuvant approach with enhanced potency over Alum are squalene containing oil-in-water emulsions, which have been included in licensed influenza vaccines, including Fluad (MF59 adjuvanted) and Pandemrix (AS03 adjuvanted). Here, we describe how to enable the co-delivery of a TLR7 agonist in a squalene-based oil-in-water emulsion, for adjuvant evaluation.

Too much of a good thing: How modulating LTB4 actions restore host defense in homeostasis or disease

The ability to regulate inflammatory pathways and host defense mechanisms is critical for maintaining homeostasis and responding to infections and tissue injury. While unbalanced inflammation is detrimental to the host; inadequate inflammation might not provide effective signals required to eliminate pathogens. On the other hand, aberrant inflammation could result in organ damage and impair host defense. The lipid mediator leukotriene B₄ (LTB₄) is a potent neutrophil chemoattractant and recently, its role as a dominant molecule that amplifies many arms of phagocyte antimicrobial effector function has been unveiled. However, excessive LTB₄ production contributes to disease severity in chronic inflammatory diseases such as diabetes and arthritis, which could potentially be involved in poor host defense in these groups of patients. In this review we discuss the cellular and molecular programs elicited during LTB₄ production and actions on innate immunity host defense mechanisms as well as potential therapeutic strategies to improve host defense.

Toll-like receptors in immunity and inflammatory diseases: Past, present, and future

The immune system is a very diverse system of the host that evolved during evolution to cope with various pathogens present in the vicinity of environmental surroundings inhabited by multicellular organisms ranging from achordates to chordates (including humans). For example, cells of immune system express various pattern recognition receptors (PRRs) that detect danger via recognizing specific pathogen-associated molecular patterns (PAMPs) and mount a specific immune response. Toll-like receptors (TLRs) are one of these PRRs expressed by various immune cells. However, they were first discovered in the Drosophila melanogaster (common fruit fly) as genes/proteins important in embryonic development and dorso-ventral body patterning/polarity. Till date, 13 different types of TLRs (TLR1-TLR13) have been discovered and described in mammals since the first discovery of TLR4 in humans in late 1997. This discovery of TLR4 in humans revolutionized the field of innate immunity and thus the immunology and host-pathogen interaction. Since then TLRs are found to be expressed on various immune cells and have been targeted for therapeutic drug development for various infectious and inflammatory diseases including cancer. Even, Single nucleotide polymorphisms (SNPs) among various TLR genes have been identified among the different human population and their association with susceptibility/resistance to certain infections and other inflammatory diseases. Thus, in the present review the current and future importance of TLRs in immunity, their pattern of expression among various immune cells along with TLR based therapeutic approach is reviewed.

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TLRs are first described PRRs that revolutionized the biology of host-pathogen interaction and immune response

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The discovery of different TLRs in humans proved milestone in the field of innate immunity and inflammation

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The pattern of expression of all the TLRs expressed by human immune cells

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An association of various TLR SNPs with different inflammatory diseases

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Currently available drugs or vaccines based on TLRs and their future in drug targeting along with the role in reproduction, and regeneration

Progress in biopharmaceutical development

Since its introduction in 1982, biopharmaceutical drugs have revolutionized the treatment of a broad spectrum of diseases and are increasingly used in nearly all branches of medicine. In recent years, the biopharmaceuticals market has developed much faster than the market for all drugs and is believed to have great potential for further dynamic growth because of the tremendous demand for these drugs. Biobetters, which contain altered active pharmaceutical ingredients with enhanced efficacy, will play an important role in the development of biopharmaceuticals. Another significant group of biopharmaceuticals are biosimilars. Their introduction in the European Union and, recently, the Unites States markets will reduce the costs of biopharmaceutical treatment. This review highlights recent progress in the field of biopharmaceutical development and issues concerning the registration of innovative biopharmaceuticals and biosimilars. The leading class of biopharmaceuticals, the current biopharmaceuticals market, and forecasts are also discussed.

Viruses Seen by Our Cells: The Role of Viral RNA Sensors

The role of the innate immune response in detecting RNA viruses is crucial for the establishment of proper inflammatory and antiviral responses. Different receptors, known as pattern recognition receptors (PRRs), are present in the cytoplasm, endosomes, and on the cellular surface. These receptors have the capacity to sense the presence of viral nucleic acids as pathogen-associated molecular patterns (PAMPs). This recognition leads to the induction of type 1 interferons (IFNs) as well as inflammatory cytokines and chemokines. In this review, we provide an overview of the significant involvement of cellular RNA helicases and Toll-like receptors (TLRs) 3, 7, and 8 in antiviral immune defenses.

Role of lipoproteins and proprotein convertase subtilisin/kexin type 9 in endotoxin clearance in sepsis

PURPOSE OF REVIEW

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition is a recent high-impact cardiovascular intervention aimed at reducing low-density lipoprotein (LDL) cholesterol levels. Notably, pathogen lipids are also carried in lipoprotein particles and are cleared by hepatocyte LDL receptors. Therefore, the role of PCSK9 in sepsis is reviewed.

RECENT FINDINGS

Endogenous PCSK9 decreases clearance of LDL cholesterol by decreasing the number of LDL receptors on hepatocytes. Similarly, PCSK9 decreases clearance of pathogen lipids, such as endotoxin, carried in LDL. Pathogen lipids, such as lipopolysaccharide (LPS) from gram-negative organisms or lipoteichoic acid from gram-positive organisms, are carried in high-density lipoprotein, LDL, and very low-density lipoprotein particles. Transfer proteins that handle pathogen lipids (e.g., LPS binding protein) are homologous to transfer proteins that handle cholesterol (e.g., phospholipid transfer protein, cholesterol ester transfer protein). Reduction in PCSK9 function results in increased LPS clearance, a decreased inflammatory response, and improved clinical outcomes in mice. PCSK9 inhibition improves survival in septic mice. Similarly, humans who carry loss-of-function variants of the PCSK9 gene have increased survival in sepsis.

SUMMARY

PCSK9 inhibition may be a useful strategy to increase pathogen lipid clearance in the treatment of patients with sepsis.

TLR7 Agonists Display Potent Antiviral Effects against Norovirus Infection via Innate Stimulation

Norovirus infections are a significant health and economic burden globally, accounting for hundreds of millions of cases of acute gastroenteritis every year. In the absence of an approved norovirus vaccine, there is an urgent need to develop antivirals to treat chronic infections and provide prophylactic therapy to limit viral spread during epidemics and pandemics. Toll-like receptor (TLR) agonists have been explored widely for their antiviral potential, and several are progressing through clinical trials for the treatment of human immunodeficiency virus (HIV) and hepatitis B virus (HBV) and as adjuvants for norovirus viruslike particle (VLP) vaccines. However, norovirus therapies in development are largely direct-acting antivirals (DAAs) with fewer compounds that target the host. Our aim was to assess the antiviral potential of TLR7 agonist immunomodulators on norovirus infection using the murine norovirus (MNV) and human Norwalk replicon models. TLR7 agonists R-848, Gardiquimod, GS-9620, R-837, and loxoribine were screened using a plaque reduction assay, and each displayed inhibition of MNV replication (50% effective concentrations [EC₅₀s], 23.5 nM, 134.4 nM, 0.59 μM, 1.5 μM, and 79.4 μM, respectively). RNA sequencing of TLR7-stimulated cells revealed a predominant upregulation of innate immune response genes and interferon (IFN)-stimulated genes (ISGs) that are known to drive an antiviral state. Furthermore, the combination of R-848 and the nucleoside analogue (NA) 2'C-methylcytidine elicited a synergistic antiviral effect against MNV, demonstrating that combinational therapy of host modulators and DAAs might be used to reduce drug cytotoxicity. In summary, we have identified that TLR7 agonists display potent inhibition of norovirus replication and are a therapeutic option to combat norovirus infections.

TLR Agonists as Adjuvants for Cancer Vaccines

Toll-like receptors (TLRs) are one of the best characterised families of pattern recognition receptors (PRRs) and play a critical role in the host defence to infection. Accumulating evidence indicates that TLRs also participate in maintaining tissue homeostasis by controlling inflammation and tissue repair, as well as promoting antitumour effects via activation and modulation of adaptive immune responses. TLR agonists have successfully been exploited to ameliorate the efficacy of various cancer therapies. In this chapter, we will discuss the rationales of using TLR agonists as adjuvants to cancer treatments and summarise the recent findings of preclinical and clinical studies of TLR agonist-based cancer therapies.

Whole-organism phenotypic screening for anti-infectives promoting host health

To date, antibiotics have been identified on the basis of their ability to kill bacteria or inhibit their growth rather than directly for their capacity to improve clinical outcomes of infected patients. Although historically successful, this approach has led to the development of an antibiotic armamentarium that suffers from a number of shortcomings, including the inevitable emergence of resistance and, in certain infections, suboptimal efficacy leading to long treatment durations, infection recurrence, or high mortality and morbidity rates despite apparent bacterial sterilization. Conventional antibiotics fail to address the complexities of in vivo bacterial physiology and virulence, as well as the role of the host underlying the complex, dynamic interactions that cause disease. New interventions are needed, aimed at host outcome rather than microbiological cure. Here we review the role of screening models for cellular and whole-organism infection, including worms, flies, zebrafish, and mice, to identify novel therapeutic strategies and discuss their future implications.

Current Strategies to Enhance Anti-Tumour Immunity

The interaction of the immune system with cancer is complex, but new approaches are resulting in exciting therapeutic benefits. In order to enhance the immune response to cancer, immune therapies seek to either induce high avidity immune responses to tumour specific antigens or to convert the tumour to a more pro-inflammatory microenvironment. Strategies, including vaccination, oncolytic viruses, and adoptive cell transfer all seek to induce anti-tumour immunity. To overcome the suppressive tumour microenvironment checkpoint inhibitors and modulators of regulatory cell populations have been investigated. This review summarizes the recent advances in immune therapies and discusses the importance of combination therapies in the treatment of cancers.

Daily oscillations in expression and responsiveness of Toll-like receptors in splenic immune cells

Circadian rhythms refer to biologic processes that oscillate with an approximate 24-h period. These rhythms direct nearly all aspects of animal behavior and physiology. The aim of our study was to determine if Toll-like receptor (TLR) expression and responsiveness exhibit time-of-day dependent differences. Therefore, we isolated an adherent splenocyte population, which consisted primarily of B cells, dendritic cells, and macrophages, over the course of a 24-h light-dark period and measured daily changes in Tlr1-8 mRNA levels and cytokine expression after cells were challenged at Zeitgeber time (ZT) 1 or ZT13 with a TLR ligand. In addition, we assessed TLR3 protein levels in adherent splenocytes over the 24-h light-dark period and challenged mice at ZT1 or ZT13 with poly(I:C), the TLR3 ligand. Our study revealed that in this adherent cell population, all Tlrs exhibited rhythmic expression except Tlr2 and Tlr5, and all TLRs, except TLR8, demonstrated daily variations in responsiveness after challenge with their respective ligand. We also revealed that TLR3 protein levels fluctuate over the daily light-dark cycle in adherent splenocytes and mice exhibit a time-of-day dependent immune response when challenged with poly(I:C). Finally, we demonstrated that mRNA levels of Tlr2 and Tlr6 display rhythmic expression in splenic macrophages. Taken together, these findings could have important implications for TLR-directed therapeutics.

Potent anti-viral vaccine adjuvant based on pH-degradable nanogels with covalently linked small molecule imidazoquinoline TLR7/8 agonist

Improving the immunogenicity of subunit vaccines, in particular skewing of the immune response towards Th1 type immunity, is crucial for the development of effective vaccines against intracellular infections and for the development of anti-cancer vaccines. Small molecule TLR7/8 agonist hold high potential for this purpose, but suffer from an undesirable pharmacokinetic profile, resulting in systemic inflammatory responses. An effective solution to this problem is covalent ligation to a larger carrier. Here, a degradable nanogel carrier containing a covalently linked imidazoquinoline (IMDQ) TLR7/8 agonist is explored as adjuvant for vaccination against the respiratory syncytial virus (RSV). In vitro and in vivo experiments in mice provide a solid rational base for preferring nanogels over soluble polymers as IMDQ carrier in terms of cellular uptake and lymph node accumulation.

Next generation of immune checkpoint therapy in cancer: new developments and challenges

Immune checkpoints consist of inhibitory and stimulatory pathways that maintain self-tolerance and assist with immune response. In cancer, immune checkpoint pathways are often activated to inhibit the nascent anti-tumor immune response. Immune checkpoint therapies act by blocking or stimulating these pathways and enhance the body's immunological activity against tumors. Cytotoxic T lymphocyte-associated molecule-4 (CTLA-4), programmed cell death receptor-1 (PD-1), and programmed cell death ligand-1(PD-L1) are the most widely studied and recognized inhibitory checkpoint pathways. Drugs blocking these pathways are currently utilized for a wide variety of malignancies and have demonstrated durable clinical activities in a subset of cancer patients. This approach is rapidly extending beyond CTLA-4 and PD-1/PD-L1. New inhibitory pathways are under investigation, and drugs blocking LAG-3, TIM-3, TIGIT, VISTA, or B7/H3 are being investigated. Furthermore, agonists of stimulatory checkpoint pathways such as OX40, ICOS, GITR, 4-1BB, CD40, or molecules targeting tumor microenvironment components like IDO or TLR are under investigation. In this article, we have provided a comprehensive review of immune checkpoint pathways involved in cancer immunotherapy, and discuss their mechanisms and the therapeutic interventions currently under investigation in phase I/II clinical trials. We also reviewed the limitations, toxicities, and challenges and outline the possible future research directions.

Metazoan Parasite Vaccines: Present Status and Future Prospects

Eukaryotic parasites and pathogens continue to cause some of the most detrimental and difficult to treat diseases (or disease states) in both humans and animals, while also continuously expanding into non-endemic countries. Combined with the ever growing number of reports on drug-resistance and the lack of effective treatment programs for many metazoan diseases, the impact that these organisms will have on quality of life remain a global challenge. Vaccination as an effective prophylactic treatment has been demonstrated for well over 200 years for bacterial and viral diseases. From the earliest variolation procedures to the cutting edge technologies employed today, many protective preparations have been successfully developed for use in both medical and veterinary applications. In spite of the successes of these applications in the discovery of subunit vaccines against prokaryotic pathogens, not many targets have been successfully developed into vaccines directed against metazoan parasites. With the current increase in -omics technologies and metadata for eukaryotic parasites, target discovery for vaccine development can be expedited. However, a good understanding of the host/vector/pathogen interface is needed to understand the underlying biological, biochemical and immunological components that will confer a protective response in the host animal. Therefore, systems biology is rapidly coming of age in the pursuit of effective parasite vaccines. Despite the difficulties, a number of approaches have been developed and applied to parasitic helminths and arthropods. This review will focus on key aspects of vaccine development that require attention in the battle against these metazoan parasites, as well as successes in the field of vaccine development for helminthiases and ectoparasites. Lastly, we propose future direction of applying successes in pursuit of next generation vaccines.

Strategies for Generating Diverse Antibody Repertoires Using Transgenic Animals Expressing Human Antibodies

Therapeutic molecules derived from antibodies have become a dominant class of drugs used to treat human disease. Increasingly, therapeutic antibodies are discovered using transgenic animal systems that have been engineered to express human antibodies. While the engineering details differ, these platforms share the ability to raise an immune response that is comprised of antibodies with fully human idiotypes. Although the predominant transgenic host species has been mouse, the genomes of rats, rabbits, chickens, and cows have also been modified to express human antibodies. The creation of transgenic animal platforms expressing human antibody repertoires has revolutionized therapeutic antibody drug discovery. The observation that the immune systems of these animals are able to recognize and respond to a wide range of therapeutically relevant human targets has led to a surge in antibody-derived drugs in current development. While the clinical success of fully human monoclonal antibodies derived from transgenic animals is well established, recent trends have seen increasingly stringent functional design goals and a shift in difficulty as the industry attempts to tackle the next generation of disease-associated targets. These challenges have been met with a number of novel approaches focused on the generation of large, high-quality, and diverse antibody repertoires. In this perspective, we describe some of the strategies and considerations we use for manipulating the immune systems of transgenic animal platforms (such as XenoMouse^®) with a focus on maximizing the diversity of the primary response and steering the ensuing antibody repertoire toward a desired outcome.

Systemic administration of a TLR7 agonist attenuates regulatory T cells by dendritic cell modification and overcomes resistance to PD-L1 blockade therapy

Research on immune checkpoint blockade therapy has made great progress in cancer immunotherapy, but the number of patients who benefit from this therapy remains limited. In this study, we examined the effects of monotherapy with systemic low-dose resiquimod, a synthesized TLR7 agonist, and examined its combined effects with PD-L1 blockade in two PD-L1 blockade-resistant tumor models (SCCVII and Colon 26). Resiquimod monotherapy in SCCVII tumors, representing impaired CD8⁺ T cell function and accelerated regulatory T cells (Tregs) within the tumors, efficiently reduced tumor growth with more recruitment of CD8⁺ T cells and a reduction of Treg. The results of resiquimod monotherapy in Colon 26, representing impaired Treg recruitment, were inferior to that in SCCVII. Combined resiquimod treatment with PD-L1 blockade exerted clear additional effects, as it was associated with reduced tumor size, attenuation of Tregs, and an increased ratio of CD8⁺ T cells/Tregs in both tumors. Systemic administration of low-dose resiquimod induced a transient and rapid activation of plasmacytoid and conventional dendritic cells, resulting in enhanced priming of T cells in regional lymph nodes. Experiments with more limited doses of resiquimod that did not yield beneficial effects after single treatment, showed additional effects to PD-L1 blockade and comparable antitumor effects when the frequency of anti-PD-L1 therapy was decreased. Our results suggest that systemic administration of low-dose resiquimod is useful as a companion drug to PD-1/PD-L1 blockade therapy.