Synthetic TLR4 Agonist Research Articles

TLR7 Negatively Regulates Dendrite Outgrowth through the Myd88-c-Fos-IL-6 Pathway

Toll-like receptors (TLRs) recognize both pathogen- and danger-associated molecular patterns and induce innate immune responses. Some TLRs are expressed in neurons and regulate neurodevelopment and neurodegeneration. However, the downstream signaling pathways and effectors for TLRs in neurons are still controversial. In this report, we provide evidence that TLR7 negatively regulates dendrite growth through the canonical myeloid differentiation primary response gene 88 (Myd88)-c-Fos-interleukin (IL)-6 pathway. Although both TLR7 and TLR8 recognize single-stranded RNA (ssRNA), the results of quantitative reverse transcription-PCR suggested that TLR7 is the major TLR recognizing ssRNA in brains. In both in vitro cultures and in utero electroporation experiments, manipulation of TLR7 expression levels was sufficient to alter neuronal morphology, indicating the presence of intrinsic TLR7 ligands. Besides, the RNase A treatment that removed ssRNA in cultures promoted dendrite growth. We also found that the addition of ssRNA and synthetic TLR7 agonists CL075 and loxoribine, but not R837 (imiquimod), to cultured neurons specifically restricted dendrite growth via TLR7. These results all suggest that TLR7 negatively regulates neuronal differentiation. In cultured neurons, TLR7 activation induced IL-6 and TNF-α expression through Myd88. Using Myd88-, IL-6-, and TNF-α-deficient neurons, we then demonstrated the essential roles of Myd88 and IL-6, but not TNF-α, in the TLR7 pathway to restrict dendrite growth. In addition to neuronal morphology, TLR7 knockout also affects mouse behaviors, because young mutant mice ∼2 weeks of age exhibited noticeably lower exploratory activity in an open field. In conclusion, our study suggests that TLR7 negatively regulates dendrite growth and influences cognition in mice.

MyD88 and TRIF synergistic interaction is required for TH1‐cell polarization with a synthetic TLR4 agonist adjuvant

Glucopyranosyl lipid adjuvant-stable emulsion (GLA-SE) is a synthetic adjuvant TLR4 agonist that promotes potent poly-functional T(H)1 responses. Different TLR4 agonists may preferentially signal via MyD88 or TIR-domain-containing adapter inducing IFN-beta (TRIF) to exert adjuvant effects; however, the contribution of MyD88 and TRIF signaling to the induction of polyclonal T(H)1 responses by TLR4 agonist adjuvants has not been studied in vivo. To determine whether GLA-SE preferentially signals through MyD88 or TRIF, we evaluated the immune response against a candidate tuberculosis (TB) vaccine Ag following immunization of mice lacking either signaling adapter compared with that of wild-type mice. We find that both MyD88 and TRIF are necessary for GLA-SE to induce a poly-functional T(H)1 immune response characterized by CD4(+) T cells producing IFN-γ, TNF, and IL-2, as well as IgG2c class switching, when paired with the TB vaccine Ag ID93. Accordingly, the protective efficacy of ID93/GLA-SE immunization against aerosolized Mycobacterium tuberculosis was lost when either signaling molecule was ablated. We demonstrate that MyD88 and TRIF must be expressed in the same cell for the in vivo T(H)1-skewing adjuvant activity, indicating that these two signaling pathways cooperate on an intracellular level. Thus engagement of both the MyD88 and TRIF signaling pathways are essential for the effective adjuvant activity of this TLR4 agonist.

Endotoxin Exposure during Sensitization to Blomia tropicalis Allergens Shifts TH2 Immunity Towards a TH17-Mediated Airway Neutrophilic Inflammation: Role of TLR4 and TLR2

Experimental evidence and epidemiological studies indicate that exposure to endotoxin lipopolysaccharide (eLPS) or other TLR agonists prevent asthma. We have previously shown in the OVA-model of asthma that eLPS administration during alum-based allergen sensitization blocked the development of lung TH2 immune responses via MyD88 pathway and IL-12/IFN-γ axis. In the present work we determined the effect of eLPS exposure during sensitization to a natural airborne allergen extract derived from the house dust mite Blomia tropicalis (Bt). Mice were subcutaneously sensitized with Bt allergens co-adsorbed onto alum with or without eLPS and challenged twice intranasally with Bt. Cellular and molecular parameters of allergic lung inflammation were evaluated 24 h after the last Bt challenge. Exposure to eLPS but not to ultrapure LPS (upLPS) preparation during sensitization to Bt allergens decreased the influx of eosinophils and increased the influx of neutrophils to the airways. Inhibition of airway eosinophilia was not observed in IFN-γdeficient mice while airway neutrophilia was not observed in IL-17RA-deficient mice as well in mice lacking MyD88, CD14, TLR4 and, surprisingly, TLR2 molecules. Notably, exposure to a synthetic TLR2 agonist (PamCSK4) also induced airway neutrophilia that was dependent on TLR2 and TLR4 molecules. In the OVA model, exposure to eLPS or PamCSK4 suppressed OVA-induced airway inflammation. Our results suggest that B. tropicalis allergens engage TLR4 that potentiates TLR2 signaling. This dual TLR activation during sensitization results in airway neutrophilic inflammation associated with increased frequency of lung TH17 cells. Our work highlight the complex interplay between bacterial products, house dust mite allergens and TLR signaling in the induction of different phenotypes of airway inflammation.

Novel combination of toll-like receptor (TLR)-7 agonist imiquimod and local radiotherapy in the treatment of breast cancer chest wall recurrences or skin metastases.

TPS3122 Background: To assess the local and systemic effects of the novel combination of local radiotherapy (RT) with imiquimod (IMQ) applied topically to breast cancer metastatic to skin, and measure immunologic correlates (clinicaltrials.gov NCT01421017). Breast cancer is the 2nd most common tumor to metastasize to the skin. Current therapies for unresectable skin lesions are rarely curative. Patients ultimately die of visceral metastases, necessitating more effective therapies. IMQ, a synthetic TLR-7 agonist has profound effects on the tumor immune microenvironment and can lead to regression of cutaneous breast cancer metastases (Adams, Clin Ca Res, 2012). The trial was designed based on accumulated data supporting the synergy of combined RT/immunotherapy (Formenti, JNCI, 2013), and pre-clinical data demonstrating the synergy of topical IMQ and local RT in a mouse model of mammary adenocarcinoma which ulcerates through the skin, and mimics a chest wall recurrence. In the mouse model, the combination was superior with complete regressions of the treated tumors, responses at untreated sites and improved survival (Dewan, Clin Ca Res, 2012). Methods: Eligibility: patients with biopsy-confirmed breast cancer, measurable disease and skin metastases, ECOG PS 0-2 and adequate organ/marrow function. RT is delivered to 1 area of skin metastases in 5 fractions of 6 Gy (days 1, 3, 5, 8, 10). IMQ cream is applied topically 5 nights/week for 8 weeks, beginning on day 1. Following a brief phase I portion to allow dose optimization in the event of unanticipated adverse events (3-3 design), the phase II study evaluates efficacy with 25 additional patients planned. Primary endpoint is the response rate in untreated distant metastases, assessed by immune-related response criteria. The local tumor responses and safety of the combination will also be determined; tumor biopsies will be studied for immune-mediated rejection signatures and peripheral lymphocytes for antigen-specific T and B cell responses. To date, 10 patients have been enrolled. The phase I portion has been successfully completed with 6 patients without DLT. Phase II enrollment has begun. Clinical trial information: NCT01421017.

Synthetic TLR4 agonist as a potential immunotherapy for melioidosis

Melioidosis, an infection caused by Gram-negative Burkholderia pseudomallei (Bp), has high clinical recurrence and mortality rates associated with pneumonia and sepsis. With the limitations in current therapeutic options and the lack of available human vaccines, development of novel countermeasures against Bp infection is vital. In this study, we evaluated the efficacy of an aminoalkyl glucosaminide 4-phosphate (AGP), a synthetic toll like receptor 4 agonist (CRX-527), in conferring protection against melioidosis in a murine model. Survival data showed 66% of mice treated with AGP prior to lethal intranasal Bp challenge survived and presented no signs of illness over a 3 months period. In contrast, all control mice succumbed to infection within 4 days. Kinetic study on organ bacterial burden demonstrated mice treated with AGP had dramatically reduced bacterial loads in both the lungs and spleens as compared to control mice. Notably, all but one AGP-treated mouse had no Bp growth in the blood as compared to overwhelming bacteraemia found in all control mice. The protective effect of CRX-527 was associated with a transient increase in pulmonary cytokine/ chemokine levels, which boosted the host’s innate immunity. This enabled rapid clearance of the pulmonary and systemic bacterial burden and prevented the development of sepsis. This study demonstrated the potential use of TLR4 agonist as a prophylactic immunotherapy in preventing melioidosis.

Molecular and Cellular Response Profiles Induced by the TLR4 Agonist-Based Adjuvant Glucopyranosyl Lipid A

BackgroundToll-like receptor (TLR)4 agonists are known potent immunostimulatory compounds. These compounds can be formulated as part of novel adjuvants to enhance vaccine medicated immune responses. However, the contribution of the formulation to the innate in vivo activity of TLR4 agonist compounds is not well understood.Methodology and Principal FindingsWe evaluated synthetic TLR4 agonist Glucopyranosyl Lipid A (GLA) for its effects on molecular and cellular innate immune responses in the murine model. Microarray techniques were used to compare the responses to GLA in an aqueous formulation or in an oil-in-water Stable Emulsion formulation (GLA-SE) versus either SE alone or the mineral salt aluminum hydroxide (alum) at the muscle injection site over multiple timepoints. In contrast to the minimal gene upregulation induced by SE and alum, both GLA and GLA-SE triggered MyD88- and TRIF-dependent gene expression. Genes for chemokines, cytokine receptors, signaling molecules, complement, and antigen presentation were also strongly upregulated by GLA and GLA-SE. These included chemokines for TH1-type T cells (CXCL9 and CXCL10) and mononuclear leukocytes (CCL2, CCL3) among others. GLA-SE induced stronger and more sustained gene upregulation than GLA in the muscle; GLA-SE induced genes were also detected in local draining lymph nodes and at lower levels in peripheral blood. Both GLA and GLA-SE resulted in increased cellular trafficking to the draining lymph nodes and upregulated MHC molecules and ICAM1 on local dendritic cells. GLA and GLA-SE transiently upregulated circulating MCP-1, TNFα, IFNγ and IP-10 in blood.Conclusions/SignificanceWhile GLA and GLA-SE activate a large number of shared innate genes and proteins, GLA-SE induces a quantitatively and qualitatively stronger response than GLA, SE or alum. The genes and proteins upregulated could be used to facilitate selection of appropriate adjuvant doses in vaccine formulations.

IL-12hi Rapamycin-Conditioned Dendritic Cells Mediate IFN-γ-Dependent Apoptosis of Alloreactive CD4+ T Cells and Limit Graft-Versus-Host Diseas

AbstractAbstract 4110 Introduction:Rapamycin (RAPA) inhibits the serine/threonine kinase mammalian Target of Rapamycin to profoundly modulate immune cell function. Dendritic cells (DC) exposed to RAPA (RAPA-DC) exhibit tolerogenic properties, including promotion of experimental cardiac allograft survival. RAPA-DC enrich for CD4+FoxP3+ regulatory T cells and induce alloreactive T cell apoptosis and anergy. Yet, paradoxically, RAPA-DC secrete increased IL-12, which is central for the generation of IFN-γ+CD4+ T helper type 1 cells. IFN-γ can be pro-apoptotic, and IL-12-driven IFN-γ inhibits graft-versus-host disease (GVHD) following hematopoietic stem cell transplantation. We hypothesized that IL-12hi RAPA-DC, unlike control (CTR)-DC, would be effective in the prevention of GVHD by supporting IFN-γ-mediated apoptosis of alloreactive T cells. Methods:DC were generated from C57BL/6 (H2-b) or B6.129S7-Ifngr1tm1Agt/J (IFN-γ-R−/− [H2-b]) bone marrow (BM) in 7 day (d) culture in the absence (CTR-DC) or presence of RAPA (RAPA-DC). CTR- and RAPA-DC cultures remained either untreated or were stimulated via TLR4 with LPS (100 ng/ml) for an additional 18 hours. Washed and CD11c+ purified DC from these groups were then used as stimulators of allogeneic CD4+ T cells (BALB/c [H2-d] or CByJ.129S7(B6)-Ifngr1tm1Agt/J [IFN-γ-R−/− {H2-d}]) in 5 d mixed leukocyte reaction (MLR) with or without anti-IFN-γ antibody. T cell apoptosis was quantified using an Annexin V Apoptosis Detection kit. The capacity of DC to prevent GVHD was assessed in irradiated BALB/c mice reconstituted with 5×106 T cell-depleted B6 BM on d0. Recipient mice received 1×106 CD11c+ BALB/c DC (CTR-, RAPA-, or LPS-exposed DC) on d0 and 1×106 B6 T cells on d1. Mice were monitored daily, and moribund mice or those with >20% weight loss were euthanized. Results:Compared to CTR-DC, especially when LPS-stimulated, RAPA-DC induced increased apoptosis (Annexin V+7-AAD+) of alloreactive CD4+ T cells in MLR (13.9±1.6% versus 7.1±0.2%; +LPS: 30.6±3.4% versus 14.7±3.6%; both p<0.05). Neutralization of IFN-γ in co-cultures containing LPS-stimulated RAPA-DC decreased levels of apoptosis to those of LPS-exposed CTR-DC (18.5±1.3% versus 14.7±3.6%; NS). IFN-γ-R−/− CD4+ T cells exposed to LPS-stimulated IL-12hi RAPA-DC exhibited decreased apoptosis when compared to wild-type CD4+ T cells (WT 15.7±3.6% versus IFN-γ-R−/− 4.9±1.1%; p<0.05) (Figure 1). There was no difference in the extent of apoptosis of alloreactive CD4+ T cells induced by IFN-γ-R−/− RAPA-DC compared to WT RAPA-DC (10.6±7.6% versus 12.4±7.6% respectively; +LPS: 30.1±16.3% versus 27.3±12.0%; both p=NS) (Figure 2). The addition of anti-IFN-γ mAb to LPS-stimulated IFN-γ-R−/− RAPA-DC significantly decreased levels of CD4+ T cell apoptosis comparable to LPS-stimulated WT CTR-DC (18.0±10.3% versus 22.0±6.3%, p<0.05). Depletion of IFN-γ did not impact on the Treg-enriching capacity (CD4hiFoxP3+/CD4hiFoxP3−) of RAPA-DC (24.2±0.4% versus 29.2±6.2% with anti-IFN-γ mAb; p=NS). Further, whereas CTR-DC and LPS-exposed CTR-DC did not prolong survival, IL-12hi RAPA-DC significantly prolonged survival from GVHD (median survival in days: GVHD, 17.5 d; RAPA-DC, 27 d, p=NS compared to GVHD; RAPA-DC + LPS, 35 d, p<0.01; syngeneic control, >50 d, p<0.01) (Figure 3). In contrast, CTR-DC had comparable GVHD mortality (21 d, p=NS). Conclusions:Increased apoptosis induced by LPS-stimulated IL-12hi RAPA-DC is mediated directly on CD4+ allogeneic T cells via IFN-γ and not through actions on DC. Thus, increased IL-12 may support IFN-γ-mediated activation-induced cell death while sparing regulatory T cells and may underlie the capacity of LPS-exposed RAPA-DC to prevent GVHD. IL-12hi human RAPA-DC, generated with the aid of endotoxin-free, synthetic TLR4 agonists, may offer a means to harness the demonstrated capacity of both IL-12 and tolerogenic DC to prevent GVHD following hematopoietic stem cell transplant. [Display omitted] [Display omitted] [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Type III IFNs are produced by and stimulate human plasmacytoid dendritic cells.

Plasmacytoid dendritic cells (pDC) are rare cells found in peripheral blood and lymphoid tissues. pDC are considered to be "professional" type I IFN-producing cells and produce 10- to 100-fold more IFN-α than other cell types in response to enveloped viruses or synthetic TLR7 and TLR9 agonists. In this study, purified pDC were found to express high levels of IFN-λ receptor mRNA, as well as cell-surface IFN-λ receptor. We have developed intracellular flow cytometry assays using Abs to IFN-λ1/3 or -λ2 to assess the expression of IFN-λ proteins by pDC. We observed that a subset of human pDC expresses only intracellular IFN-α, whereas another subset produces both IFN-α and IFN-λ after stimulation with virus or the TLR9 agonist, CpG A; the cells that coexpressed IFN-α and IFN-λ were the cells with the highest levels of IFN-α expression. Ab cross-linking of CD4 or CD303 molecules on pDC inhibited both HSV-induced IFN-λ and IFN-α production. Like the production of IFN-α, the HSV-induced IFN-λ production in pDC was mediated through TLR9 and independent of virus replication. Exogenous IFN-λ treatment of pDC resulted in increased virus-induced expression of both IFN-α and IFN-λ. In addition, both exogenous IFN-λ and -α inhibited dexamethasone-induced apoptosis of pDC. We conclude that pDC are major producers of IFN-λ1 and -λ2 in response to viral stimulation and also express functional receptors for this cytokine. Thus, IFN-λ can serve as an autocrine signal to strengthen the antiviral response of pDC by increasing IFN-α and IFN-λ production, resulting in prolonged pDC survival.

Glucopyranosyl Lipid Adjuvant (GLA), a Synthetic TLR4 Agonist, Promotes Potent Systemic and Mucosal Responses to Intranasal Immunization with HIVgp140

Successful vaccine development against HIV will likely require the induction of strong, long-lasting humoral and cellular immune responses in both the systemic and mucosal compartments. Based on the known immunological linkage between the upper-respiratory and urogenital tracts, we explored the potential of nasal adjuvants to boost immunization for the induction of vaginal and systemic immune responses to gp140. Mice were immunized intranasally with HIV gp140 together with micellar and emulsion formulations of a synthetic TLR4 agonist, Glucopyranosyl Lipid Adjuvant (GLA) and responses were compared to R848, a TLR7/8 agonist, or chitosan, a non TLR adjuvant. GLA and chitosan but not R848 greatly enhanced serum immunoglobulin levels when compared to antigen alone. Both GLA and chitosan induced high IgG and IgA titers in nasal and vaginal lavage and feces. The high IgA and IgG titers in vaginal lavage were associated with high numbers of gp140-specific antibody secreting cells in the genital tract. Whilst both GLA and chitosan induced T cell responses to immunization, GLA induced a stronger Th17 response and chitosan induced a more Th2 skewed response. Our results show that GLA is a highly potent intranasal adjuvant greatly enhancing humoral and cellular immune responses, both systemically and mucosally.

Systemic inflammation after aortic cross clamping is influenced by Toll-like receptor 2 preconditioning and deficiency

BackgroundThe perioperative morbidity and mortality of abdominal aortic aneurysm repair is linked to systemic inflammation. Important triggers of the latter are Toll-like receptors (TLRs), which play a central role in innate immunity. Ischemia/reperfusion (I/R) injury can be influenced by either TLR stimulation before I/R (preconditioning) or TLR dysfunction (deficiency or polymorphism). The influence of TLR2 stimulation or deficiency on systemic cytokine release and organ damage after aortic cross clamping has not been evaluated yet. MethodsWild type (WT) and TLR2-deficient mice were subjected to 1 h ischemia and 2 or 4 h reperfusion of the infrarenal aorta. One group of WT mice was preconditioned with the synthetic TLR2 agonist Pam3Cys-Ser-Lys4 (Pam3CSK4). Sham-operated animals without I/R served as controls. Plasma levels of interleukin (IL)-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12, granulocyte macrophage–colony stimulating factor, tumor necrosis factor-α, alanine transaminase (ALT), aspartate transaminase (AST), lactate dehydrogenase (LDH), and creatinine were measured. ResultsI/R injury caused by transient clamping of the infrarenal aorta led to a time-dependent increase of all measured cytokines except IL-4, IL-5, and granulocyte macrophage–colony stimulating factor. This was accompanied by elevated markers of organ damage (ALT, AST, and LDH) except creatinine. Preconditioning with Pam3CSK4 led to lower plasma concentrations of all cytokines, with the exception of anti-inflammatory IL-10 which was significantly upregulated. Furthermore, ALT, AST, and LDH plasma concentrations were lower in the preconditioning group. TLR2-deficient mice similarly showed reduced signs of systemic inflammation and organ damage, although less distinctive. IL-2, IL-6, IL-12, ALT, and LDH were time dependently lower compared with WT mice. IL-10 concentration was higher in TLR2-deficient mice compared with WT. ConclusionsBoth, preconditioning via TLR2 and TLR2 deficiency, ameliorate systemic inflammation and organ damage during I/R injury caused by clamping of the infrarenal aorta. Compared with untreated WT animals, Pam3CSK4 preconditioned and TLR2-deficient mice showed lower concentrations of pro-inflammatory cytokines, whereas anti-inflammatory IL-10 was elevated in both groups. This was accompanied by reduced organ dysfunction parameters.

Modulation of protection against Mycobacterium tuberculosis by adjuvants that elicit different T cell responses. (166.18)

Abstract The use of an adjuvant within a vaccine can influence and direct the immune response to enable a desired outcome. A T helper 1 (Th1) response, including antigen-specific production of interferon-gamma (IFN-γ), is needed to protect against Mycobacterium tuberculosis. A successful subunit vaccine should include not only an appropriate antigen but also a proper adjuvant to ensure that a Th1 mediated cellular response is induced. Only a few adjuvants have been approved for use in human vaccines such as Alum and oil-in-water (o/w) based emulsions, including MF59 (Novartis), AS03 (GSK Biologics), AF03 (Sanofi) and liposomes (Crucell). These adjuvants primarily induce humoral responses. A new adjuvant in approved products is AS04, which combines the TLR-4 agonist monophosphoryl lipid A (MPL) with Alum. In this study we combine our candidate TB vaccine, ID93, with a synthetic TLR-4 agonist, glucopyranosyl lipid adjuvant (GLA) mixed with a stable o/w emulsion (SE). Both SE and GLA-SE induce potent cellular responses when combined with ID93 in mice. ID93/GLA-SE induced multifunctional CD4+ Th1 cell responses (IFN-γ, TNF-α, IL-2) in mice and protected both mice and guinea pigs against M. tuberculosis. In contrast, ID93/SE in the absence of GLA induced IL-5 and provided no protection, as assessed by bacterial burden, survival, and pathology. These results demonstrate the importance of properly formulating subunit vaccines with effective adjuvants for use against TB.

Discovery of novel TLR modulators by Molecular Modeling and Virtual Screening

Toll-like receptors (TLRs) play a crucial role in the onset of innate immunity by distinguishing between endogenous and pathogen-associated molecular patterns. TLR2, in cooperation with TLR1 and TLR6, recognizes several microbial components such as lipoteichoic acids and lipoproteins [1]. Toll-like receptors have been broadly reported to contribute to several inflammatory chronic diseases and autoimmune diseases [2]. In this study we aim to discover new TLR2 modulating agents through computer-aided drug design. Based on recently identified synthetic TLR2 agonists [3] and antagonists [4], a shape and chemical-feature based similarity search was performed against a library of 260.071 compounds provided by the National Cancer Institute (NCI) [5]. This led to several virtual hits, which were tested in vitro in a cell-based assay. Several compounds with biological activity on TLR2 signaling in general and TLR1 signaling specifically were identified. To further optimize these biologically validated virtual hits, molecular interaction fields (MIFs) for the dimerization of TLR2 and TLR1 were developed. Feature-based MIFs allowed for the manual creation of virtual compounds that fulfill an optimized interaction pattern, which led to a 3D pharmacophore that was used for a second virtual screening to select compounds for biological testing.

Intradermally administered TLR4 agonist GLA-SE enhances the capacity of human skin DCs to activate T cells and promotes emigration of Langerhans cells

The natural TLR4 agonist lipopolysaccharide (LPS) has notable adjuvant activity. However, it is not useful as a vaccine adjuvant due to its toxicity. Glucopyranosyl lipid A (GLA) is a synthetic derivative of the lipid A tail of LPS with limited cytotoxicity, but strong potential to induce immune responses in mice, guinea pigs, non-human primates, and humans. In this study we determined how this synthetic TLR4 agonist affects the function of different subsets of human skin dendritic cells (DCs). The effect of GLA in an aqueous formulation (GLA-AF) or in an oil-in-water emulsion (GLA-SE) was compared to that of LPS and TLR3 agonist poly(I:C) using a human skin explant model with intradermal injections for the administration of the agonists. Intradermal injection of GLA-SE or LPS, but not GLA-AF, enhanced the emigration of CD1ahigh/langerin+ Langerhans cells (LCs), but not dermal DCs (DDCs). LCs and CD14− DDCs exhibited an enhanced mature phenotype following intradermal administration of either of the two GLA formulations tested, similar to DCs that emigrated from LPS-injected skin. However, only injection of GLA-SE resulted in a significant increase in the production of the wide range of cytokines that is observed with LPS. Moreover, DCs that emigrated from GLA-SE-injected skin induced stronger CD4+ T-cell activation, as indicated by a more pronounced T-cell proliferation, than DCs from skin injected with GLA-AF or LPS. Altogether, our data show that GLA-SE has a notable potency to stimulate the function of skin DCs, indicating that GLA-SE may be a good candidate as adjuvant for vaccines administered via the intradermal route.

MF59 oil-in-water emulsion in combination with a synthetic TLR4 agonist (E6020) is a potent adjuvant for a combination Meningococcus vaccine

The inclusion of a potent TLR4 immune potentiator to a recombinant antigen vaccine formulation enhances both the magnitude and the breadth of the engendered immune response. One such immune potentiator (TLR4 agonist E6020) was evaluated with recombinant Men B antigens delivered in MF59 sub-micron adjuvant emulsion. The ability of this formulation to enhance serum antibody and bactercidal titers was investigated. The co-delivery of E6020 within MF59 enhanced both the serum and bactericidal titers for Men B antigens and for Men B antigens combined with Men ACWY-CRM conjugate vaccine. The delivery of TLR4 agonist within MF59 emulsion oil droplets leads to a more potent response in comparison to the TLR4 when admixed with MF59 emulsion.

Therapy with TLR7 Agonists Induces Lymphopenia: Correlating Pharmacology to Mechanism in a Mouse Model

Synthetic TLR7 agonists have been proposed as oral replacements for interferonα (IFNα) therapy in the treatment of hepatitis C virus infection. However, adverse effects, such as lymphopenia and cardiovascular irregularities, have been observed in the clinical following treatment with TLR7 agonists. We wished to understand and characterise the relationship between TLR7 agonism and adverse effects. We compared responses to two prototypic TLR7 agonists (Resiquimod: R-848; and PF-04878691) in a mouse model and compared the responses to treatment with IFNα. We measured clinically relevant adverse effects such as lymphopenia and cardiovascular irregularities and related them to plasma drug levels and clinically relevant efficacy biomarkers such as the pro-inflammatory cytokine IP-10, 2'5'OAS and TLR7 receptor expression. By 2 h post dose all agents had induced a dose-dependent transient lymphopenia. IFNα increased heart rate immediately following dosing, persisting for 5 h, whilst PF-04878691 induced significant reductions in blood pressure. Lymphopenia co-incided with maximum plasma drug levels, raised levels of IP-10 and the auto-induction of TLR7 expression in the blood and lymph nodes. Peak levels of 2'5'OAS occurred at 24 h post-dose and only at doses which also induced lymphopenia. We conclude that systemic delivery of TLR7 agonists or IFNα induces similar exaggerated pharmacology, consistent with there being a narrow therapeutic window between efficacy and safety. This clinically validated mouse model will help to investigate whether more potent agonists or optimised dosing schedules, will be successful strategies for targeting TLR7 in patients.

KSAC, a Defined Leishmania Antigen, plus Adjuvant Protects against the Virulence of L. major Transmitted by Its Natural Vector Phlebotomus duboscqi

BackgroundRecombinant KSAC and L110f are promising Leishmania vaccine candidates. Both antigens formulated in stable emulsions (SE) with the natural TLR4 agonist MPL® and L110f with the synthetic TLR4 agonist GLA in SE protected BALB/c mice against L. major infection following needle challenge. Considering the virulence of vector-transmitted Leishmania infections, we vaccinated BALB/c mice with either KSAC+GLA-SE or L110f+GLA-SE to assess protection against L. major transmitted via its vector Phlebotomus duboscqi.MethodsMice receiving the KSAC or L110f vaccines were challenged by needle or L. major-infected sand flies. Weekly disease progression and terminal parasite loads were determined. Immunological responses to KSAC, L110f, or soluble Leishmania antigen (SLA) were assessed throughout vaccination, three and twelve weeks after immunization, and one week post-challenge.ResultsFollowing sand fly challenge, KSAC-vaccinated mice were protected while L110f-vaccinated animals showed partial protection. Protection correlated with the ability of SLA to induce IFN-γ-producing CD4+CD62LlowCCR7low effector memory T cells pre- and post-sand fly challenge.ConclusionsThis study demonstrates the protective efficacy of KSAC+GLA-SE against sand fly challenge; the importance of vector-transmitted challenge in evaluating vaccine candidates against Leishmania infection; and the necessity of a rapid potent Th1 response against Leishmania to attain true protection.

The Importance of Adjuvant Formulation in the Development of a Tuberculosis Vaccine

An effective protein-based vaccine for tuberculosis will require a safe and effective adjuvant. There are few adjuvants in approved human vaccines, including alum and the oil-in-water-based emulsions MF59 (Novartis Vaccines and Diagnostics), AS03 and AS04 (GlaxoSmithKline Biologics), AF03 (Sanofi), and liposomes (Crucell). When used with pure, defined proteins, both alum and emulsion adjuvants are effective at inducing primarily humoral responses. One of the newest adjuvants in approved products is AS04, which combines monophosphoryl lipid A, a TLR-4 agonist, with alum. In this study, we compared two adjuvants: a stable oil-in-water emulsion (SE) and a stable oil-in-water emulsion incorporating glucopyranosyl lipid adjuvant, a synthetic TLR-4 agonist (GLA-SE), each together with a recombinant protein, ID93. Both the emulsion SE and GLA-SE adjuvants induce potent cellular responses in combination with ID93 in mice. ID93/SE induced Th2-biased immune responses, whereas ID93/GLA-SE induced multifunctional CD4(+) Th1 cell responses (IFN-γ, TNF-α, and IL-2). The ID93/GLA-SE vaccine candidate induced significant protection in mice and guinea pigs, whereas no protection was observed with ID93/SE, as assessed by reductions in bacterial burden, survival, and pathology. These results highlight the importance of properly formulating subunit vaccines with effective adjuvants for use against tuberculosis.

A new synthetic TLR4 agonist, GLA, allows dendritic cells targeted with antigen to elicit Th1 T-cell immunity in vivo.

Protein-based vaccines offer safety and cost advantages but require adjuvants to induce immunity. Here we examined the adjuvant capacity of glucopyranosyl lipid A (GLA), a new synthetic non-toxic analogue of lipopolysaccharide. In mice, in comparison with non-formulated LPS and monophosphoryl lipid A, formulated GLA induced higher antibody titers and generated Type 1 T-cell responses to HIV gag-p24 protein in spleen and lymph nodes, which was dependent on TLR4 expression. Immunization was greatly improved by targeting HIV gag p24 to DCs with an antibody to DEC-205, a DC receptor for antigen uptake and processing. Subcutaneous immunization induced antigen-specific T-cell responses in the intestinal lamina propria. Immunity did not develop in mice transiently depleted of DCs. To understand how GLA works, we studied DCs directly from vaccinated mice. Within 4 h, GLA caused DCs to upregulate CD86 and CD40 and produce cytokines including IL-12p70 in vivo. Importantly, DCs removed from mice 4 h after vaccination became immunogenic, capable of inducing T-cell immunity upon injection into naïve mice. These data indicate that a synthetic and clinically feasible TLR4 agonist rapidly stimulates full maturation of DCs in vivo, allowing for adaptive immunity to develop many weeks to months later.

NOD2 Deficiency Results in Increased Susceptibility to Peptidoglycan-Induced Uveitis in Mice

The innate immune receptor NOD2 is a genetic cause of uveitis (Blau syndrome). Intriguingly, in the intestine where polymorphisms of NOD2 predispose to Crohn's disease, NOD2 reportedly suppresses inflammation triggered by the bacterial cell wall component, peptidoglycan (PGN). Whether NOD2 exerts a similar capacity in the regulation of ocular inflammation to PGN has not been explored. NOD2, NOD1, or MyD88 knockout (KO) mice and their wild-type (WT) controls were administered an intravitreal injection of PGN (a metabolite of which is the NOD2 agonist, muramyl dipeptide), or synthetic TLR2/1 and TLR2/6 agonists, Pam₃CSK4 and FSL-1. Ocular inflammation was assessed by intravital microscopy and histopathology. Cytokine production in eye tissue homogenates was measured by ELISA. PGN triggered uveitis in mice. This inflammation was abolished in the absence of the TLR signaling mediator MyD88. NOD2 exerted a negative regulatory role because PGN-triggered eye inflammation was exacerbated in NOD2 KO mice. Increased intravascular response coincided with enhanced leukocytes within the aqueous and vitreous humors. The enhanced susceptibility of NOD2 KO mice to PGN uveitis coincided with increased cytokine production of IL-12p40, IL-17, and IL-23 but not IL-12p70, TNFα, or IFNγ. NOD1 deficiency did not result in the same sensitivity to PGN. Ocular inflammation induced by synthetic TLR2 agonists required MyD88 but not NOD2 or NOD1. NOD2 may serve differential roles in the eye to promote inflammation while also tempering cell responses to PGN akin to what has been reported in colitis.

TLR2 signaling improves immunoregulation to prevent type 1 diabetes

Signaling through TLR2 promotes inflammation and modulates CD4(+) CD25(+) Tregs. We assessed mechanistically how this molecule would alter immunoregulation in type 1 diabetes (T1D). We also asked whether TLR2 may be involved in our recent discovery that viral infection can protect from autoimmune diabetes by expanding and invigorating Tregs. Treatment of prediabetic mice with a synthetic TLR2 agonist diminished T1D and increased the number and function of CD4(+) CD25(+) Tregs, also conferring DCs with tolerogenic properties. TLR2 ligation also promoted the expansion of Tregs upon culture with DCs and ameliorated their capacity to prevent the disease. Protection from T1D by lymphocytic choriomeningitis virus (LCMV) infection depended on TLR2. LCMV increased the frequency of CD4(+) CD25(+) Tregs and their production of TGF-β more significantly in WT than TLR2-deficient mice. Furthermore, LCMV infection in vivo or LCMV-infected DCs in vitro rendered, via TLR2, CD4(+) CD25(+) Tregs capable of diminishing T1D. We identify novel mechanisms by which TLR2 promotes immunoregulation and controls autoimmune diabetes in naïve or infected hosts. This work should help understand T1D etiology and develop novel immune-based therapeutic interventions.