A CpG 1018 adjuvanted neuraminidase vaccine provides robust protection from influenza virus challenge in mice

Influenza virus infections pose a significant threat to global health. Vaccination is the main countermeasure against influenza virus spread, however, the effectiveness of vaccines is variable. Current seasonal influenza virus vaccines mostly rely on the immunodominant hemagglutinin (HA) glycoprotein on the viral surface, which usually leads to a narrow and strain-specific immune response. The HA undergoes constant antigenic drift, which can lead to a dramatic loss in vaccine effectiveness, requiring the annual reformulation and readministration of influenza virus vaccines. Recently, it has been demonstrated that the subdominant glycoprotein, neuraminidase (NA), is an attractive target for vaccine development. Here, we tested a newly developed recombinant influenza virus N1 neuraminidase vaccine candidate, named N1-MPP, adjuvanted with CpG 1018, a TLR9 agonist. Additionally, N2-MPP and B-NA-MPP vaccine constructs have been generated to cover the range of influenza viruses that are seasonally circulating in humans. These constructs have been characterized in vitro and in vivo regarding their functionality and protective potential. Furthermore, a trivalent NA-MPP mix was tested. No antigenic competition between the individual NA constructs was detected. By adjuvating the recombinant protein constructs with CpG 1018 it was possible to induce a strong and robust immune response against the NA, which provided full protection against morbidity and mortality after high lethal challenges in vivo. This study provides important insights for the development of a broadly protective NA-based influenza virus vaccine candidate.

Adjuvanting a subunit SARS-CoV-2 vaccine with clinically relevant adjuvants induces durable protection in mice

Adjuvants enhance the magnitude and the durability of the immune response to vaccines. However, there is a paucity of comparative studies on the nature of the immune responses stimulated by leading adjuvant candidates. In this study, we compared five clinically relevant adjuvants in mice-alum, AS03 (a squalene-based adjuvant supplemented with α-tocopherol), AS37 (a TLR7 ligand emulsified in alum), CpG1018 (a TLR9 ligand emulsified in alum), O/W 1849101 (a squalene-based adjuvant)-for their capacity to stimulate immune responses when combined with a subunit vaccine under clinical development. We found that all four of the adjuvant candidates surpassed alum with respect to their capacity to induce enhanced and durable antigen-specific antibody responses. The TLR-agonist-based adjuvants CpG1018 (TLR9) and AS37 (TLR7) induced Th1-skewed CD4+ T cell responses, while alum, O/W, and AS03 induced a balanced Th1/Th2 response. Consistent with this, adjuvants induced distinct patterns of early innate responses. Finally, vaccines adjuvanted with AS03, AS37, and CpG1018/alum-induced durable neutralizing-antibody responses and significant protection against the B.1.351 variant 7 months following immunization. These results, together with our recent results from an identical study in non-human primates (NHPs), provide a comparative benchmarking of five clinically relevant vaccine adjuvants for their capacity to stimulate immunity to a subunit vaccine, demonstrating the capacity of adjuvanted SARS-CoV-2 subunit vaccines to provide durable protection against the B.1.351 variant. Furthermore, these results reveal differences between the widely-used C57BL/6 mouse strain and NHP animal models, highlighting the importance of species selection for future vaccine and adjuvant studies.

A Phase Ib Open-Label, Multicenter Study of Inhaled DV281, a TLR9 Agonist, in Combination with Nivolumab in Patients with Advanced or Metastatic Non-small Cell Lung Cancer

PURPOSE

Although PD-(L)1 inhibitors have shown efficacy in advanced/metastatic non-small cell lung cancer (NSCLC), many patients do not respond to this treatment and more effective combinations with acceptable toxicities are needed. To assess the potential benefit of combining localized innate immune stimulation with checkpoint blockade, the TLR9 agonist DV281 was combined with nivolumab in a phase Ib study.

PATIENTS AND METHODS

Patients after one or two prior lines of systemic therapy were enrolled in a dose-escalation study with a 3+3 design. DV281 was administered via inhalation in five dose cohorts at 1 to 25 mg; nivolumab 240 mg was administered intravenously every 2 weeks. Safety, tolerability, pharmacodynamics, and response to treatment were assessed.

RESULTS

Twenty-six patients with advanced NSCLC enrolled. Baseline programmed death ligand 1 (PD-L1) expression was present in 16 patients (61.5%); 21 (80.7%) had received previous anti-PD-1/PD-L1. Thirteen patients (50%) had stable disease, nine (34.6%) had progressive disease, and four (15.4%) were not evaluable. Median duration of disease control was 124 days. Adverse events were seen in 16 patients (61.5%), mostly grade 1/2 chills, fatigue, flu-like symptoms, diarrhea, and rash; there was only one grade 3 adverse event (dyspnea). Pharmacodynamic assessment, measured by IFN- inducible gene expression, showed target engagement in all dose cohorts. Systemic pharmacodynamic responses plateaued in the 2 highest dose cohorts.

CONCLUSIONS

DV281 with nivolumab was well tolerated with target engagement observed at every dose. Pharmacodynamic advantages at doses above 10 mg were unclear. The long duration of disease control in 50% of patients suggests clinically relevant activity in this population of heavily pretreated patients.

A Phase 2a, Double-Blind, Placebo-controlled Randomized Trial of Inhaled TLR9 Agonist AZD1419 in Asthma

Rationale: To examine the potential of TLR9 (Toll-like receptor 9) activation to modulate the type 2 immune response in asthma.Objectives: To evaluate efficacy and safety of AZD1419, an inhaled TLR9 agonist, in a phase 2a, randomized, double-blind trial.Methods: Adult patients with asthma with a history of elevated eosinophils (>250 cells/μl) were randomized 1:1 to receive 13 once-weekly doses of inhaled AZD1419 (1, 4, or 8 mg; n = 40) or placebo (n = 41). Inhaled corticosteroids and long-acting β₂-agonist were tapered down and then discontinued. The last four doses of AZD1419 were given without maintenance medication, followed by a 40-week observation period. Primary endpoint was time to loss of asthma control (LOC).Measurements and Main Results: AZD1419 induced a T-helper cell type 1-type IFN response with a sustained reduction in markers of type 2 inflammation. However, there were no statistically significant differences between AZD1419 and placebo for time to LOC, proportion of patients with LOC, changes in Asthma Control Questionnaire-five-item version, exacerbations, reliever use, FEV₁, peak expiratory flow, or fractional exhaled nitric oxide (Fe_NO). LOC was predicted by an early rise in Fe_NO in 63% of patients. Despite withdrawal of maintenance treatment, 24 patients completed the study without LOC; AZD1419 n = 11, placebo n = 13. Adverse events were balanced across groups, with no deaths or serious adverse events judged as causally related to AZD1419.Conclusions: AZD1419 was safe and well tolerated but did not lead to improved asthma control, despite reducing markers of type 2 inflammation. Results suggest that a novel accelerated step-down approach based on Fe_NO is possible for patients with well-controlled asthma.

Development of CpG-adjuvanted stable prefusion SARS-CoV-2 spike antigen as a subunit vaccine against COVID-19

The COVID-19 pandemic is a worldwide health emergency which calls for an unprecedented race for vaccines and treatment. In developing a COVID-19 vaccine, we applied technology previously used for MERS-CoV to produce a prefusion-stabilized SARS-CoV-2 spike protein, S-2P. To enhance immunogenicity and mitigate the potential vaccine-induced immunopathology, CpG 1018, a Th1-biasing synthetic toll-like receptor 9 (TLR9) agonist was selected as an adjuvant candidate. S-2P in combination with CpG 1018 and aluminum hydroxide (alum) was found to be the most potent immunogen and induced high titer of neutralizing antibodies in sera of immunized mice against pseudotyped lentivirus reporter or live wild-type SARS-CoV-2. In addition, the antibodies elicited were able to cross-neutralize pseudovirus containing the spike protein of the D614G variant, indicating the potential for broad spectrum protection. A marked Th1 dominant response was noted from cytokines secreted by splenocytes of mice immunized with CpG 1018 and alum. No vaccine-related serious adverse effects were found in the dose-ranging study in rats administered single- or two-dose regimens of S-2P combined with CpG 1018 alone or CpG 1018 with alum. These data support continued development of CHO-derived S-2P formulated with CpG 1018 and alum as a candidate vaccine to prevent COVID-19 disease.

Low-dose metronomic cyclophosphamide complements the actions of an intratumoral C-class CpG TLR9 agonist to potentiate innate immunity and drive potent T cell-mediated anti-tumor responses

The synthetic oligonucleotide SD-101 is a potent and specific agonist for toll-like receptor 9. Intratumoral injection of SD-101 induces significant anti-tumor immunity in preclinical and clinical studies, especially when combined with PD-1 blockade. To build upon this strategy, we studied the enhancement of SD-101 activities by combination with low-dose cyclophosphamide, a well-characterized agent with potentially complementary activities. In multiple mouse tumor models, we demonstrate substantial anti-tumor activity of the combination, compared to each single agent. Combination therapy generated CD8+ T cell dependent immunity leading to rejection of both non-injected and injected tumors and long-term survival, even in very large tumors. Mechanistic studies encompassing global gene expression changes and characterization of immune cell infiltrates show the rapid, sequential induction of innate and adaptive responses and identify discrete contributions of SD-101 and cyclophosphamide. Importantly, these changes were prominent in tumors not injected directly with SD-101. Combination treatment resulted in creation of a permissive environment for a systemic anti-tumor immune response, including a reduction of intratumoral regulatory T cells (Tregs) and an increase in "M1" versus "M2" tumor-associated macrophage (TAM) phenotypes. Additionally, we observed increased immunogenic cell death as well as antigen processing in response to combination treatment.

Abstract 2259: Tumor abscopal responses induced by the TLR9 agonist, SD-101, are strongly potentiated by a HDAC class I inhibitor, domatinostat

In cancer settings severe T cell exhaustion is one major road block limiting immunotherapy efficacy. Epigenetic changes happening during T cell effector differentiation lock T cells in a non-programmable state which limits the efficacy of checkpoint blockade. In addition, histone modification has been reported to critically modulate MHC I and II expression on tumor cells and influx of T cells into tumor.

We have previously shown that intratumoral administration of a TLR9 agonist, SD-101, induces T cell responses capable of attacking tumor lesions throughout the body. SD-101, combined with the PD-1 inhibitor pembrolizumab, is currently being investigated in patients with metastatic melanoma and head and neck cancer with encoraging results. Domatinostat (4SC AG) is a well-tolerated orally available selective class I histone deacetylase inhibitor HDACi) with demonstrated anti-tumor activity in hematological cancers as well as in numerous animal models of solid tumors as monotherapy and in combination with checkpoint blockade. Domatinostat is currently being investigated in patients with metastatic melanoma and gastrointestinal cancers in combination with PD(L)-1 antibodies.

This study addresses whether the addition of domatinostat to the SD-101 regimen would potentiate the T cell response induced by SD-101. Studies were conducted in multiple syngeneic models in which tumors grow in multiple site of the body but only one is treated intratumorally with SD-101 and domatinostat is given systemically (oral). SD-101 and domatinostat were given alone or in combination, at clinically relevant dosages. The combination of intratumoral SD-101 and domatinostat induced substantial regression of the primary tumor (injected) and distant site cutaneous tumors, as well as lung metastases

The combination was superior to either agent given alone and led to increased tumor specific cytotoxic CD8 T cells (CTL) infiltrating distant site lesions. CTL’s were characterized by a low exhaustion phenotype, increased proliferative capacity and increased co-expression of cytolytic markers, CD107 and GranzymeB. Gene expression profiling was performed on abscopal tumors using the PanCancer immune profiling panel from Nanostring.

The combination of SD-101 and domatinostat led to upregulation of multiple immune related signatures indicating increased T, NK and dendritic cell functions. Notably, the combination of SD-101 and domatinostat was more efficacious than SD-101 combined with various other epigenetic compounds. The addition of PD-1

blockade to SD-101 and domatinostat further boosted T cell responses leading to rejection in mice with high metastatic burdens. These results suggest that domatinostat acts on SD-101 primed tumor specific CD8+ T cells to expand them, render them more cytolytic and facilitate their infiltration in abscopal tumors.

Citation Format: Émilie Degagné, Jose Romo, Marilena Gallotta, Shravan Kannan, Robert L. Coffman, Cristiana Guiducci. Tumor abscopal responses induced by the TLR9 agonist, SD-101, are strongly potentiated by a HDAC class I inhibitor, domatinostat [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2259.

Preclinical development of the TLR9 agonist DV281 as an inhaled aerosolized immunotherapeutic for lung cancer: Pharmacological profile in mice, non-human primates, and human primary cells

CpG-motif-containing oligodeoxynucleotides (CpG-ODN) activate innate immunity through Toll-Like Receptor (TLR) 9 signaling and generate local immune responses when delivered directly to the lung. Herein we describe pharmacological studies in mice, cynomolgus monkeys, and in human primary cells which support the development of DV281, a C-class CpG-ODN, as an inhaled aerosolized immunotherapeutic for lung cancer to be combined with an inhibitor of the anti-programmed cell death protein 1 (PD‑1) immune checkpoint. In vitro, DV281 potently induced Interferon (IFN)‑α from monkey and human peripheral blood mononuclear cells (PBMCs), stimulated interleukin‑6 production and proliferation in human B cells, and induced TLR9-dependent cytokine responses from mouse splenocytes. Intranasal delivery of DV281 to mice led to substantial but transient cytokine and chemokine responses in the lung. Lung responses to repeated intranasal DV281 were partially to fully reversible 2 weeks after the final dose and were absent in TLR9-deficient mice. Single escalating doses of aerosolized DV281 in monkeys induced dose-dependent induction of IFN-regulated genes in bronchoalveolar lavage cells and blood. In a repeat-dose safety study in monkeys, inhaled DV281 was well-tolerated, and findings were mechanism of action-related and non-adverse. Co-culture of human PBMC with DV281 and anti-PD‑1 antibody did not augment cytokine or cellular proliferation responses compared to DV281 alone, indicating that the combination did not lead to dysregulated cytokine responses. These studies support clinical development of inhaled aerosolized DV281 as a combination therapy with anti-PD‑1 antibody for lung cancer immunotherapy.

In Situ Vaccination with a TLR9 Agonist and Local Low-Dose Radiation Induces Systemic Responses in Untreated Indolent Lymphoma

This multicenter phase I/II clinical trial evaluated intratumoral SD-101, a TLR9 agonist, and low-dose radiation in patients with untreated indolent lymphoma. Twenty-nine enrolled patients received 4 Gy of radiation followed by 5 weekly intratumoral injections of SD-101 at a single tumor site. No treatment-related grade 4 or serious adverse events occurred. Nearly all patients had tumor reduction at their treated site. More importantly, 24 patients had tumor reduction at their nontreated sites, with 5 patients achieving a partial response and one achieving a complete response. Treatment-related increases of CD8+ and CD4+ effector T cells and decreases of T follicular helper and T regulatory cells (Treg) were observed in the tumor microenvironment. Low pretreatment levels of CD4+ Tregs, proliferating CD8+ T cells, and Granzyme B+ CD8+ T cells were associated with favorable outcomes. Intratumoral SD-101 in combination with low-dose radiation is well tolerated and results in regression of both treated and untreated sites of disease.Significance: In situ vaccination with the TLR9 agonist SD-101, along with low-dose radiation, was safe and induced systemic responses in patients with indolent lymphoma. Low levels of CD4+ Tregs, proliferating CD8+ T cells, and Granzyme B+ CD8+ T cells in the tumor microenvironment predicted favorable response to treatment. Cancer Discov; 8(10); 1258-69. ©2018 AACR. This article is highlighted in the In This Issue feature, p. 1195.

SD-101 in Combination with Pembrolizumab in Advanced Melanoma: Results of a Phase Ib, Multicenter Study

PD-1 inhibitors are approved for treating advanced melanoma, but resistance has been observed. This phase Ib trial evaluated intratumoral SD-101, a synthetic CpG oligonucleotide that stimulates Toll-like receptor 9 (TLR9), in combination with pembrolizumab in patients with unresectable or metastatic malignant melanoma. The most common adverse events related to SD-101 were injection-site reactions and transient, mild-to-moderate "flu-like" symptoms. Among the 9 patients naïve to anti-PD-1 therapy, the overall response rate (ORR) was 78%. The estimated 12-month progression-free survival rate was 88%, and the overall survival rate was 89%. Among 13 patients having prior anti-PD-1 therapy, the ORR was 15%. RNA profiling of tumor biopsies demonstrated increased CD8⁺ T cells, natural killer cells, cytotoxic cells, dendritic cells, and B cells. The combination of intratumoral SD-101 and pembrolizumab was well tolerated and induced broad immune activation in the tumor microenvironment with durable tumor responses in both peripheral and visceral lesions.Significance: These early data demonstrate that the combination of pembrolizumab with intratumoral SD-101 is well tolerated and can induce immune activation at the tumor site. Combining an intratumoral TLR9 innate immune stimulant with PD-1 blockade can potentially increase clinical efficacy with minimal additional toxicity relative to PD-1 blockade alone. Cancer Discov; 8(10); 1250-7. ©2018 AACR. This article is highlighted in the In This Issue feature, p. 1195.

Inhaled TLR9 Agonist Renders Lung Tumors Permissive to PD-1 Blockade by Promoting Optimal CD4+ and CD8+ T-cell Interplay

Currently approved inhibitors of the PD-1/PD-L1 pathway represent a major advance for the treatment of lung cancers, yet they are ineffective in a majority of patients due to lack of preexisting T-cell reactivity. Here, we show that a TLR9 agonist delivered by inhalation is able to prime T-cell responses against poorly immunogenic lung tumors and to complement the effects of PD-1 blockade. Inhaled TLR9 agonist causes profound remodeling in tumor-bearing lungs, leading to the formation of tertiary lymphoid structures adjacent to the tumors, CD8⁺ T-cell infiltration into the tumors, dendritic cell expansion, and antibody production. Inhalation of TLR9 agonist also increased the pool of functional PD-1^lowT-bet^high effector CD8⁺ T cells in tumor-bearing lungs. Effector CD8⁺ T cells generated by inhaled TLR9 agonist treatment were licensed by PD-1 blockade to become highly functional CTLs, leading to a durable rejection of both lung tumors and tumor lesions outside the lungs. CD4⁺ T cells activated in response to inhaled TLR9 play a critical role in this process by controlling the proliferation, preventing exhaustion, and guiding the differentiation of optimally functional CTLs. This study characterizes a strategy to apply localized TLR9 stimulation to a tumor type not accessible for direct injection, a strategy that may expand the therapeutic potential of PD-1 blockade in non-small cell lung cancer.Significance: These findings demonstrate that local delivery of a toll-like receptor 9 agonist can change the immune content of an entire organ and enhance the efficacy of immune checkpoint inhibition.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/17/4943/F1.large.jpg Cancer Res; 78(17); 4943-56. ©2018 AACR.

Combination immunotherapy with TLR agonists and checkpoint inhibitors suppresses head and neck cancer

Checkpoint inhibitors have demonstrated efficacy in patients with recurrent or metastatic head and neck squamous cell carcinoma (HNSCC). However, the majority of patients do not benefit from these agents. To improve the efficacy of checkpoint inhibitors, intratumoral (i.t.) injection with innate immune activators, TLR7 and TLR9 agonists, were tested along with programmed death-1 receptor (PD-1) blockade. The combination therapy suppressed tumor growth at the primary injected and distant sites in human papillomavirus-negative (HPV-negative) SCC7 and MOC1, and HPV-positive MEER syngeneic mouse models. Abscopal effects and suppression of secondary challenged tumor suggest that local treatment with TLR agonists in combination with anti-PD-1 provided systemic adaptive immunity. I.t. treatment with a TLR7 agonist increased the ratio of M1 to M2 tumor-associated macrophages (TAMs) and promoted the infiltration of tumor-specific IFNγ-producing CD8+ T cells. Anti-PD-1 treatment increased T cell receptor (TCR) clonality of CD8+ T cells in tumors and spleens of treated mice. Collectively, these experiments demonstrate that combination therapy with i.t. delivery of TLR agonists and PD-1 blockade activates TAMs and induces tumor-specific adaptive immune responses, leading to suppression of primary tumor growth and prevention of metastasis in HNSCC models.

Abstract LB-239: Pharmacodynamic changes confirm the mechanism of action mediating SD-101 efficacy, in combination with pembrolizumab, in a phase 1b/2 study in metastatic melanoma (MEL-01)

Introduction: SD-101 is a synthetic CpG oligonucleotide agonist of Toll-like receptor 9. SD-101 stimulates dendritic cells to release interferon-alpha and mature into antigen presenting cells that effectively activate T cell responses. Pembrolizumab is a PD-1 inhibitor that has been approved for the treatment of multiple tumors including metastatic melanoma. In mouse tumor models, SD-101 synergizes with anti-PD-1 inducing substantial infiltration of tumor-reactive T cells and durable, complete responses in all treated animals. The MEL-01 trial assesses the safety and preliminary efficacy of SD-101 in combination with pembrolizumab in stage IIIC-IV melanoma. Previously presented clinical data suggest enhanced efficacy for this combination. Biomarker data from the MEL-01 trial support the mechanism of action of SD-101.

Methods: The dose escalation phase of this trial is a modified 3 + 3 design with 4 dose levels of SD-101 (1, 2, 4, and 8 mg) in combination with pembrolizumab. SD-101 is injected into a single tumor lesion qw X 4 followed by q3w X 7. Pembrolizumab is dosed at 200 mg IV q3w. Specimens for biomarker analyses included biopsies of the injected tumor and peripheral blood, and were taken before and after treatment (Days 29, 85 and 169). Biopsies were analyzed by multiplexed immunohistochemistry and Nanostring to evaluate the immunophenotype of the tumor environment. Peripheral blood collected immediately before and 24 hours after dosing was analyzed by qPCR with a panel of interferon (IFN) responsive genes to confirm target engagement. Tumor responses were assessed using RECIST v1.1.

Results: IFN signature profiling in blood indicated that SD-101 engages its target in a dose-dependent manner. In tumor biopsies taken after the fourth intratumoral injection, an elevated IFN signature was also observed, confirming persistent local immune activation. Nanostring assessments demonstrated increases in multiple immune cell types in tumors in a subset of patients. In particular, an increase in Th1 responses and a decrease in Th2 responses were found, a shift which is consistent the mechanism of action of SD-101. Immunophenotypic signatures generally correlated with tumor response and were greater in patients naïve to PD-1 treatment compared to patients who previously progressed on PD-1 treatment. Signals for immune suppression generally showed an inverse correlation with clinical response. An elevated CD8 profile was detected by Nanostring and confirmed by immunohistochemistry showing increased CD8+ T cell infiltration in tumors.

Conclusions: Biomarker assessments of the tumor microenvironment in melanoma patients receiving SD-101 and pembrolizumab demonstrate an immunophenotype with CD8 infiltration and a Th1 driven immune response consistent with the mechanism of action and anti-tumor activity of this combination.

Citation Format: Albert Candia, Cristiana Guiducci, Robert L. Coffman, Graeme Currie, Abraham Leung, Robert Janssen, Shivaani Kummar, Sanjiv Agarwala, John Nemunaitis, Rene Gonzalez, Joseph Drabick, Antoni Ribas. Pharmacodynamic changes confirm the mechanism of action mediating SD-101 efficacy, in combination with pembrolizumab, in a phase 1b/2 study in metastatic melanoma (MEL-01) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-239. doi:10.1158/1538-7445.AM2017-LB-239

Abstract 4696: Development of an inhaled TLR9 agonist for the immunotherapy of lung cancer

CpG-oligonucleotides (CpG-ODN) stimulate innate immune responses through Toll-like receptor-9 (TLR9). Intratumoral (IT) administration of CpG-ODN has been shown to be safe and clinically effective in humans and in multiple animal species. An important feature of local administration of a CpG-ODN is the ability to stimulate immune responses that control the growth of distant, uninjected tumors. Such treatment is especially effective when combined with a complementary mode of immunotherapy, such as anti-PD-1 or radiation. However, repeated IT injection is not practical for many tumor types, including most lung cancers. In mild asthmatic patients and healthy subjects, CpG-ODN have demonstrated safety and pharmacologic activity when delivered by inhalation directly to the lungs. Thus, inhaled CpG presents an alternative to IT injection for primary lung cancers and for other tumor types with prominent lung metastases. In the 4T1 mouse model of metastatic breast cancer, treatment of mice with a CpG-ODN administered intranasally led to a marked reduction in the number of lung metastases. This reduction was accompanied by infiltration of tumors with activated CD8+ and CD4+ T cells and the formation of highly organized tertiary lymphoid structures. These changes are similar to those observed after IT injection of solid tumors growing subcutaneously, and are consistent with changes observed in human tumors responsive to immunotherapy. In the 4T1 model, intranasal CpG-ODN strongly synergized with systemic anti-PD-1 treatment and induced complete clearance of lung tumors, as well as metastases in tissues not exposed to the CpG-ODN, including liver, pancreas and bone. This generation of systemic immunity resulted in long-term survival in the majority of mice. Immune cell subset depletion studies implicate both CD8 and CD4 T cells in the rejection of lung tumors treated with inhaled CpG-ODN plus anti-PD1. Dynavax has developed a CpG-ODN, DV281, that is optimized for aerosol delivery and plans to initiate clinical studies in NSCLC patients in 2017.

Citation Format: Marilena Gallotta, Hikmat Assi, Robert L. Coffman, Cristiana Guiducci. Development of an inhaled TLR9 agonist for the immunotherapy of lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4696. doi:10.1158/1538-7445.AM2017-4696

Optimization, Production, and Characterization of a CpG-Oligonucleotide-Ficoll Conjugate Nanoparticle Adjuvant for Enhanced Immunogenicity of Anthrax Protective Antigen

We have synthesized and characterized a novel phosphorothioate CpG oligodeoxynucleotide (CpG ODN)-Ficoll conjugated nanoparticulate adjuvant, termed DV230-Ficoll. This adjuvant was constructed from an amine-functionalized-Ficoll, a heterobifunctional linker (succinimidyl-[(N-maleimidopropionamido)-hexaethylene glycol] ester) and the CpG-ODN DV230. Herein, we describe the evaluation of the purity and reactivity of linkers of different lengths for CpG-ODN-Ficoll conjugation, optimization of linker coupling, and conjugation of thiol-functionalized CpG to maleimide-functionalized Ficoll and process scale-up. Physicochemical characterization of independently produced lots of DV230-Ficoll reveal a bioconjugate with a particle size of approximately 50 nm and covalent attachment of more than 100 molecules of CpG per Ficoll. Solutions of purified DV230-Ficoll were stable for at least 12 months at frozen and refrigerated temperatures and stability was further enhanced in lyophilized form. Compared to nonconjugated monomeric DV230, the DV230-Ficoll conjugate demonstrated improved in vitro potency for induction of IFN-α from human peripheral blood mononuclear cells and induced higher titer neutralizing antibody responses against coadministered anthrax recombinant protective antigen in mice. The processes described here establish a reproducible and robust process for the synthesis of a novel, size-controlled, and stable CpG-ODN nanoparticle adjuvant suitable for manufacture and use in vaccines.

A CpG-Ficoll Nanoparticle Adjuvant for Anthrax Protective Antigen Enhances Immunogenicity and Provides Single-Immunization Protection against Inhaled Anthrax in Monkeys

Nanoparticulate delivery systems for vaccine adjuvants, designed to enhance targeting of secondary lymphoid organs and activation of APCs, have shown substantial promise for enhanced immunopotentiation. We investigated the adjuvant activity of synthetic oligonucleotides containing CpG-rich motifs linked to the sucrose polymer Ficoll, forming soluble 50-nm particles (DV230-Ficoll), each containing >100 molecules of the TLR9 ligand, DV230. DV230-Ficoll was evaluated as an adjuvant for a candidate vaccine for anthrax using recombinant protective Ag (rPA) from Bacillus anthracis. A single immunization with rPA plus DV230-Ficoll induced 10-fold higher titers of toxin-neutralizing Abs in cynomolgus monkeys at 2 wk compared with animals immunized with equivalent amounts of monomeric DV230. Monkeys immunized either once or twice with rPA plus DV230-Ficoll were completely protected from challenge with 200 LD50 aerosolized anthrax spores. In mice, DV230-Ficoll was more potent than DV230 for the induction of innate immune responses at the injection site and draining lymph nodes. DV230-Ficoll was preferentially colocalized with rPA in key APC populations and induced greater maturation marker expression (CD69 and CD86) on these cells and stronger germinal center B and T cell responses, relative to DV230. DV230-Ficoll was also preferentially retained at the injection site and draining lymph nodes and produced fewer systemic inflammatory responses. These findings support the development of DV230-Ficoll as an adjuvant platform, particularly for vaccines such as for anthrax, for which rapid induction of protective immunity and memory with a single injection is very important.

OX40 Ligand Contributes to Human Lupus Pathogenesis by Promoting T Follicular Helper Response

Increased activity of T follicular helper (Tfh) cells plays a major pathogenic role in systemic lupus erythematosus (SLE). However, the mechanisms that cause aberrant Tfh cell responses in SLE remain elusive. Here we showed the OX40 ligand (OX40L)-OX40 axis contributes to the aberrant Tfh response in SLE. OX40L was expressed by myeloid antigen-presenting cells (APCs), but not B cells, in blood and in inflamed tissues in adult and pediatric SLE patients. The frequency of circulating OX40L-expressing myeloid APCs positively correlated with disease activity and the frequency of ICOS(+) blood Tfh cells in SLE. OX40 signals promoted naive and memory CD4(+) T cells to express multiple Tfh cell molecules and were sufficient to induce them to become functional B cell helpers. Immune complexes containing RNA induced OX40L expression on myeloid APCs via TLR7 activation. Our study provides a rationale to target the OX40L-OX40 axis as a therapeutic modality for SLE.

A novel TLR-9 agonist C792 inhibits plasmacytoid dendritic cell-induced myeloma cell growth and enhance cytotoxicity of bortezomib

Our prior study in multiple myeloma (MM) patients showed increased numbers of plasmacytoid dendritic cells (pDCs) in the bone marrow (BM), which both contribute to immune dysfunction as well as promote tumor cell growth, survival and drug resistance. Here we show that a novel Toll-like receptor (TLR-9) agonist C792 restores the ability of MM patient-pDCs to stimulate T-cell proliferation. Coculture of pDCs with MM cells induces MM cell growth; and importantly, C792 inhibits pDC-induced MM cell growth and triggers apoptosis. In contrast, treatment of either MM cells or pDCs alone with C792 does not affect the viability of either cell type. In agreement with our in vitro data, C792 inhibits pDC-induced MM cell growth in vivo in a murine xenograft model of human MM. Mechanistic studies show that C792 triggers maturation of pDCs, enhances interferon-α and interferon-λ secretion and activates TLR-9/MyD88 signaling axis. Finally, C792 enhances the anti-MM activity of bortezomib, lenalidomide, SAHA or melphalan. Collectively, our preclinical studies provide the basis for clinical trials of C792, either alone or in combination, to both improve immune function and overcome drug resistance in MM.

A limited CpG-containing oligodeoxynucleotide therapy regimen induces sustained suppression of allergic airway inflammation in mice

BACKGROUND

CpG-containing oligodeoxynucleotides (CpG-ODNs) are potent inhibitors of T helper 2 mediated allergic airway disease in sensitised mice challenged with allergen. A single treatment has transient effects but a limited series of treatments has potential to achieve clinically meaningful sustained inhibition of allergic airway disease.

OBJECTIVE

To optimise the treatment regimen for sustained efficacy and to determine the mechanisms of action in mice of an inhaled form of CpG-ODN being developed for human asthma treatment.

METHODS

We set up a chronic allergic-asthma model using ragweed-sensitised mice exposed weekly to intranasal ragweed. Using this model, the effects of a limited series of weekly intranasal 1018 ISS (CpG-ODN; B-class) treatments were evaluated during treatment and for several weeks after treatments had stopped but weekly allergen exposures continued. Treatment efficacy was evaluated by measuring effects on lung T helper 2 cytokines and eosinophilia, and lung dendritic cell function and T-cell responses.

RESULTS

Twelve intranasal 1018 ISS treatments induced significant suppression of bronchoalveolar lavage eosinophilia and interleukin 4, 5 and 13 levels. This suppression of allergic T helper 2 parameters was maintained through 13 weekly ragweed exposures administered after treatment cessation. Subsequent experiments demonstrated that at least five treatments were required for lasting suppression. Although CpG-ODN induced moderate T helper 1 responses, suppression of allergic airway disease did not require interferon γ but was associated with induction of a regulatory T-cell response.

CONCLUSIONS

A short series of CpG-ODN treatments results in sustained suppression of allergic lung inflammation induced by a clinically relevant allergen.

RNA recognition by human TLR8 can lead to autoimmune inflammation

High expression level of human TLR8 in mice results in spontaneous, multiorgan inflammation attributable in part to increased DC activation.

Studies on the role of the RNA receptor TLR8 in inflammation have been limited by its different function in human versus rodents. We have generated multiple lines of transgenic mice expressing different levels of human TLR8. The high copy number chimeras were unable to pass germline; developed severe inflammation targeting the pancreas, salivary glands, and joints; and the severity of the specific phenotypes closely correlated with the huTLR8 expression levels. Mice with relatively low expression levels survived and bred successfully but had increased susceptibility to collagen-induced arthritis, and the levels of huTLR8 correlated with proinflammatory cytokines in the joints of the animals. At the cellular level, huTLR8 signaling exerted a DC-intrinsic effect leading to up-regulation of co-stimulatory molecules and subsequent T cell activation. A pathogenic role for TLR8 in human diseases was suggested by its increased expression in patients with systemic arthritis and the correlation of TLR8 expression with the elevation of IL-1β levels and disease status. We found that the consequence of self-recognition via TLR8 results in a constellation of diseases, strikingly distinct from those related to TLR7 signaling, and points to specific inflammatory diseases that may benefit from inhibition of TLR8 in humans.

Assessing the safety of adjuvanted vaccines

Despite the very low risk-to-benefit ratio of vaccines, fear of negative side effects has discouraged many people from getting vaccinated, resulting in reemergence of previously controlled diseases such as measles, pertussis, and diphtheria. Part of this fear stems from the lack of public awareness of the many preclinical and clinical safety evaluations that vaccines must undergo before they are available to the general public, as well as from misperceptions of what adjuvants are or why they are used in vaccines. The resultant "black box" leads to a preoccupation with rare side effects (such as autoimmune diseases) that are speculated, but not proven, to be linked to some vaccinations. The focus of this review article is to open this black box and provide a conceptual framework for how vaccine safety is traditionally assessed. We discuss the strengths and shortcomings of tools that can be and are used preclinically (in animal studies), translationally (in biomarker studies with human sera or cells), statistically (for disease epidemiology), and clinically (in the design of human trials) to help ascertain the risk of the infrequent and delayed adverse events that arise in relation to adjuvanted vaccine administration.

Netting neutrophils are major inducers of type I IFN production in pediatric systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by a breakdown of tolerance to nuclear antigens and the development of immune complexes. Genomic approaches have shown that human SLE leukocytes homogeneously express type I interferon (IFN)-induced and neutrophil-related transcripts. Increased production and/or bioavailability of IFN-α and associated alterations in dendritic cell (DC) homeostasis have been linked to lupus pathogenesis. Although neutrophils have long been shown to be associated with lupus, their potential role in disease pathogenesis remains elusive. Here, we show that mature SLE neutrophils are primed in vivo by type I IFN and die upon exposure to SLE-derived anti-ribonucleoprotein antibodies, releasing neutrophil extracellular traps (NETs). SLE NETs contain DNA as well as large amounts of LL37 and HMGB1, neutrophil proteins that facilitate the uptake and recognition of mammalian DNA by plasmacytoid DCs (pDCs). Indeed, SLE NETs activate pDCs to produce high levels of IFN-α in a DNA- and TLR9 (Toll-like receptor 9)-dependent manner. Our results reveal an unsuspected role for neutrophils in SLE pathogenesis and identify a novel link between nucleic acid-recognizing antibodies and type I IFN production in this disease.

Selective utilization of Toll-like receptor and MyD88 signaling in B cells for enhancement of the antiviral germinal center response

The contribution of Toll-like receptor (TLR) signaling to T cell-dependent (TD) antibody responses was assessed by using mice lacking the TLR signaling adaptor MyD88 in individual cell types. When a soluble TLR9 ligand was used as adjuvant for a protein antigen, MyD88 was required in dendritic cells but not in B cells to enhance the TD antibody response, regardless of the inherent immunogenicity of the antigen. In contrast, a TLR9 ligand contained within a virus-like particle substantially augmented the TD germinal center IgG antibody response, and this augmentation required B cell MyD88. The ability of B cells to discriminate between antigens based on the physical form of a TLR ligand probably reflects an adaptation to facilitate strong antiviral antibody responses.

Autoimmune skin inflammation is dependent on plasmacytoid dendritic cell activation by nucleic acids via TLR7 and TLR9

Lupus-prone mice develop a chronic inflammatory response to cutaneous injury that depends on the production of type I interferon, TLR7, and TLR9.

Recognition of endogenous DNA and RNA by cells expressing TLR7 and TLR9 is an important contributor to the pathogenesis of systemic lupus erythematosus and has been suggested to contribute to cutaneous lupus and to a group of related inflammatory skin diseases termed interface dermatitis. We have developed a mouse model of TLR7- and TLR9-dependent skin inflammation using tape stripping. In normal mice, this resulted in a rapid but transient inflammatory cell infiltration accompanied by induction of type I IFN production by plasmacytoid dendritic cells (PDCs) and release of extracellular traps and proinflammatory cytokines by neutrophils. These responses were strongly reduced in MyD88-deficient mice and in mice treated with a bifunctional inhibitor of TLR7 and TLR9. In contrast, in lupus-prone (NZBxNZW)F₁ mice, tape stripping induced the development of chronic lesions characterized by a persistent type I IFN gene signature and many clinical and histological features of cutaneous lupus. Depletion of PDCs before injury prevented the development of skin lesions, whereas treatment with a bifunctional TLR7/9 inhibitor before tape stripping or after the initial lesion was established led to a significant reduction of the disease. These data suggest that inhibitors of TLR7 and TLR9 signaling have potential therapeutic application for the treatment of interface dermatitis.

Vaccine adjuvants: putting innate immunity to work

Adjuvants enhance immunity to vaccines and experimental antigens by a variety of mechanisms. In the past decade, many receptors and signaling pathways in the innate immune system have been defined and these innate responses strongly influence the adaptive immune response. The focus of this review is to delineate the innate mechanisms by which adjuvants mediate their effects. We highlight how adjuvants can be used to influence the magnitude and alter the quality of the adaptive response in order to provide maximum protection against specific pathogens. Despite the impressive success of currently approved adjuvants for generating immunity to viral and bacterial infections, there remains a need for improved adjuvants that enhance protective antibody responses, especially in populations that respond poorly to current vaccines. However, the larger challenge is to develop vaccines that generate strong T cell immunity with purified or recombinant vaccine antigens.

CpG-containing immunostimulatory DNA sequences elicit TNF-alpha-dependent toxicity in rodents but not in humans

CpG-containing immunostimulatory DNA sequences (ISS), which signal through TLR9, are being developed as a therapy for allergic indications and have proven to be safe and well tolerated in humans when administrated via the pulmonary route. In contrast, ISS inhalation has unexplained toxicity in rodents, which express TLR9 in monocyte/macrophage lineage cells as well as in plasmacytoid DCs (pDCs) and B cells, the principal TLR9-expressing cells in humans. We therefore investigated the mechanisms underlying this rodent-specific toxicity and its implications for humans. Mice responded to intranasally administered 1018 ISS, a representative B class ISS, with strictly TLR9-dependent toxicity, including lung inflammation and weight loss, that was fully reversible and pDC and B cell independent. Knockout mouse experiments demonstrated that ISS-induced toxicity was critically dependent on TNF-alpha, with IFN-alpha required for TNF-alpha induction. In contrast, human PBMCs, human alveolar macrophages, and airway-derived cells from Ascaris suum-allergic cynomolgus monkeys did not produce appreciable TNF-alpha in vitro in response to ISS stimulation. Moreover, sputum of allergic humans exposed to inhaled ISS demonstrated induction of IFN-inducible genes but minimal TNF-alpha induction. These data demonstrate that ISS induce rodent-specific TNF-alpha-dependent toxicity that is absent in humans and reflective of differential TLR9 expression patterns in rodents versus humans.

Development of TLR inhibitors for the treatment of autoimmune diseases

SUMMARY

The innate immune system is a critical element of protection from invading pathogens. The specific receptors that recognize various components of the pathogens trigger signals that result in the production of proinflammatory cytokines as well as the activation of antigen-presenting cells, which activate the adaptive immune system. The discovery of the Toll-like receptors (TLRs) as important components of pathogen recognition has brought new understanding of the key signaling molecules involves in innate immune activation. Interestingly, it appears that most TLRs can recognize self-ligands as well and that mechanisms are required to discriminate between self and non-self ligands. One of these mechanisms is the expression of all the nucleic acid-specific TLR in endosomal compartments and not on the cell surface. Inappropriate activation of TLRs by self-components can result in sterile inflammation or autoimmunity. For example, TLR7 and TLR9 activation by endogenous RNA and DNA, transported to the endosomes in the form of immune complexes or non-covalently associated with cationic peptides, could be an important mechanism involved in promoting diseases such as systemic lupus erythematosus and psoriasis. In this review, we discuss the rationale for self-recognition by TLR7 and TLR9 as an important part of the development of lupus and other autoimmune diseases. We describe novel inhibitors of these receptors and provide evidence to support their use as novel therapeutic agents for autoimmunity.

Biomarkers measuring the activity of Toll-like receptor ligands in clinical development programs

Efforts to develop therapeutic approaches based on stimulation of Toll-like receptor (TLR) pathways have increased in recent years (Nat Med 13:552-559). The effectiveness of TLR agonists is currently being tested in diseases such as cancer, asthma, allergic rhinitis, and viral infections (J Clin Invest 117: 1184-1194; Blood 105: 489-495; Proc Am Thorac Soc 4:289-294; N Engl J Med 355:1445-1455; Am J Respir Crit Care Med 174:15-20). For a successful clinical trial program, it is important to know whether the therapeutic agent under development is both pharmacologically active and activating the intended pathway in humans. A biomarker reflecting this in an accurate and sensitive manner greatly facilitates dose/regimen-finding and is a "must-have." In this chapter, we describe a polymerase chain reaction (PCR)-based method that quantifies gene expression levels indicative of TLR-stimulation in human samples. We focus on genes specifically induced in an IFN-alpha-dependent manner, as this pathway is activated after stimulation of both TLR-7 and TLR-9. We demonstrate that IFN-alpha-inducible gene expression levels can be successfully applied in a clinical trial setting as a marker of drug activity in a variety of human samples, including peripheral blood mononuclear cells (PBMC), cells derived from the airways, as well as cells from induced-sputum.

Signalling pathways leading to IFN-alpha production in human plasmacytoid dendritic cell and the possible use of agonists or antagonists of TLR7 and TLR9 in clinical indications

Plasmacytoid dendritic cells (PDC) are highly specialized immune cells capable of producing large amounts of type I and III IFN in response to viral infection. This response is mediated through TLR7 and TLR9 signalling pathways. In addition, PDC can differentiate into fully mature dendritic cells able to efficiently crosspresent viral antigens, thus playing an important role in adaptive immunity. This dual property of PDC is being used in clinical settings where synthetic TLR7 and TLR9 ligands are currently evaluated in clinical trials for the treatment of viral infections, allergies and cancers. Interestingly, there is evidence suggesting that chronic activation of PDC by endogenous RNA and DNA containing immune complexes maybe an important mechanism of driving autoimmunity and significant efforts to develop bi-functional antagonists of TLR7 and TLR9 are currently underway.

CpG oligodeoxynucleotides alter lymphocyte and dendritic cell trafficking in humans

PURPOSE

CpG oligodeoxynucleotides (CpG-ODN) are being investigated as cancer vaccine adjuvants because they mature plasmacytoid dendritic cells (PDC) into potent antigen-presenting cells. CpG-ODN also induce PDC to secrete chemokines that alter lymphocyte migration. Whether CpG-ODN TLR signals enhance antigen-specific immunity and/or trafficking in humans is unknown.

EXPERIMENTAL DESIGN

We conducted a phase I study of CpG-ODN (1018 ISS) given as a vaccine adjuvant with granulocyte-macrophage colony-stimulating factor (GM-CSF) to induce T-cell immunity to a peptide vaccine from the tumor-associated antigen hTERT.

RESULTS

The adjuvant effect was limited; only 1 of 16 patients showed a high-frequency hTERT-specific tetramer CD8(+) T-cell response. However, CpG-ODN induced marked, transient peripheral blood lymphopenia. Biopsies showed dense lymphocytic infiltration at the vaccine site clustered around activated PDC. In vitro, CpG-ODN-treated PDC induced T-cell migration, showing that CpG-ODN stimulation of human PDC was sufficient to chemoattract T cells.

CONCLUSIONS

Our results show that (a) CpG-ODN with GM-CSF may not be an effective adjuvant strategy for hTERT peptide vaccines but (b) GM-CSF/CpG-ODN causes a PDC-mediated chemokine response that recruits T-cell migration to the peripheral tissues. These findings suggest a novel therapeutic role for targeted injections of CpG-ODN to direct lymphocyte migration to specific sites such as the tumor bed.

PI3K is critical for the nuclear translocation of IRF-7 and type I IFN production by human plasmacytoid predendritic cells in response to TLR activation

Plasmacytoid predendritic cells (pDCs) are the main producers of type I interferon (IFN) in response to Toll-like receptor (TLR) stimulation. Phosphatidylinositol-3 kinase (PI3K) has been shown to be activated by TLR triggering in multiple cell types; however, its role in pDC function is not known. We show that PI3K is activated by TLR stimulation in primary human pDCs and demonstrate, using specific inhibitors, that PI3K is required for type I IFN production by pDCs, both at the transcriptional and protein levels. Importantly, PI3K was not involved in other proinflammatory responses of pDCs, including tumor necrosis factor α and interleukin 6 production and DC differentiation. pDCs preferentially expressed the PI3K δ subunit, which was specifically involved in the control of type I IFN production. Although uptake and endosomal trafficking of TLR ligands were not affected in the presence of PI3K inhibitors, there was a dramatic defect in the nuclear translocation of IFN regulatory factor (IRF) 7, whereas nuclear factor κB activation was preserved. Thus, PI3K selectively controls type I IFN production by regulating IRF-7 nuclear translocation in human pDCs and could serve as a novel target to inhibit pathogenic type I IFN in autoimmune diseases.

Reversal of polarized T helper 1 and T helper 2 cell populations in murine leishmaniasis

T helper 1 (Th1) and Th2 cells are the major subsets of fully differentiated CD4+ T cells in the mouse. The spectrum of cytokines characteristic of each subset determines the distinctive regulatory and effector functions mediated by each subset. We have used the murine model of Leishmania major infection to study the question of whether highly polarized populations of normal T cells are as stable in their cytokine phenotype as Th clones or whether the phenotype can be altered with regulatory cytokines. Interleukin 4 (IL-4) appears to be a key cytokine for Th2 responses as it is necessary for both the initial differentiation of Th responses to L. major and the stability of ongoing responses. Furthermore, IL-4 is capable of converting highly polarized Th1 responses to Th2 responses either in vitro or when adoptively transferred to severe combined immunodeficiency mice.

Therapeutic targeting of innate immunity with Toll-like receptor agonists and antagonists

The identification of the antigen recognition receptors for innate immunity, most notably the Toll-like receptors, has sparked great interest in therapeutic manipulation of the innate immune system. Toll-like receptor agonists are being developed for the treatment of cancer, allergies and viral infections, and as adjuvants for potent new vaccines to prevent or treat cancer and infectious diseases. As recognition grows of the role of inappropriate Toll-like receptor stimulation in inflammation and autoimmunity, significant efforts have begun to develop antagonists to Toll-like receptors as well.

Toll-like Receptor Recognition Regulates Immunodominance in an Antimicrobial CD4+ T Cell Response

Although Toll-like Receptors (TLRs) play a major function in innate recognition of pathogens, their role in antigen processing and presentation in vivo is poorly understood. Here we establish that Toxoplasma gondii profilin, a TLR11 ligand present in the parasite, is an immunodominant antigen in the CD4(+) T cell response to the pathogen. The immunogenicity of profilin was entirely dependent on both TLR11 recognition and signaling through the adaptor myeloid differentiation factor 88 (MyD88). Selective responsiveness to this parasite protein was regulated at the level of antigen presentation by dendritic cells (DC) and required both TLR signaling and major histocompatibility complex (MHC) class II recognition acting in cis. These findings support a major influence of TLR recognition in antigen presentation by DC in vivo and establish a mechanism by which TLR ligand association regulates the immunogenicity of microbial antigens.

Origins of the T(H)1-T(H)2 model: a personal perspective

Robert L. Coffman recounts how his work on immunoglobulin E regulation along with data from Tim Mosmann on the functional heterogeneity of T cell clones led to the T helper type 1-T helper type 2 hypothesis.

Properties regulating the nature of the plasmacytoid dendritic cell response to Toll-like receptor 9 activation

Human plasmacytoid dendritic cells (PDCs) can produce interferon (IFN)-α and/or mature and participate in the adaptive immune response. Three classes of CpG oligonucleotide ligands for Toll-like receptor (TLR)9 can be distinguished by different sequence motifs and different abilities to stimulate IFN-α production and maturation of PDCs. We show that the nature of the PDC response is determined by the higher order structure and endosomal location of the CpG oligonucleotide. Activation of TLR9 by the multimeric CpG-A occurs in transferrin receptor (TfR)-positive endosomes and leads exclusively to IFN-α production, whereas monomeric CpG-B oligonucleotides localize to lysosome-associated membrane protein (LAMP)-1–positive endosomes and promote maturation of PDCs. However, CpG-B, when complexed into microparticles, localizes in TfR-positive endosomes and induces IFN-α from PDCs, whereas monomeric forms of CpG-A localize to LAMP-1–positive endosomes accompanied by the loss of IFN-α production and a gain in PDC maturation activity. CpG-C sequences, which induce both IFN-α and maturation of PDCs, are distributed in both type of endosomes. Encapsulation of CpG-C in liposomes stable above pH 5.75 completely abrogated the IFN-α response while increasing PDC maturation. This establishes that the primary determinant of TLR9 signaling is not valency but endosomal location and demonstrates a strict compartmentalization of the biological response to TLR9 activation in PDCs.

Immunostimulatory Sequences Regulate Interferon-inducible Genes but not Allergic Airway Responses

RATIONALE

1018 ISS is a synthetic oligonucleotide containing immunostimulatory CpG motifs. In animal studies, 1018 ISS effectively inhibited Th2-mediated lung inflammation, including eosinophil infiltration, and airway hyperresponsiveness.

OBJECTIVES

To evaluate whether 1018 ISS has activity in subjects with allergic asthma.

METHODS

Forty subjects (n = 21, 1018 ISS; n = 19, placebo) were enrolled in a randomized, double-blind, placebo-controlled, parallel-group study to examine safety, pharmacologic activity, and efficacy of 1018 ISS on allergen-induced airway responses. Subjects received 36 mg of 1018 ISS or placebo by nebulization weekly for 4 wk.

MEASUREMENTS

Allergen inhalation challenge was performed 24 h after the 2nd and 4th doses to measure the early and late fall in FEV(1). Sputum cells and peripheral blood mononuclear cells were collected before and after dosing, and gene expression was measured by quantitative polymerase chain reaction.

MAIN RESULTS

Treatment with 1018 ISS significantly increased expression of interferon (IFN)-gamma and IFN-inducible genes, such as IFN-gamma-inducible 10 kD protein (IP10), monokine induced by IFN-gamma (MIG), IFN-stimulated gene (ISG)-54, monocyte chemotactic protein (MCP)-1, and MCP-2 from cells collected postdose (p < 0.05). There was no attenuation of the early or late decrease in FEV(1) after 1018 ISS compared with placebo, nor a reduction in allergen-induced sputum eosinophils or Th2-related gene expression measured in sputum cells.

CONCLUSIONS

This study demonstrated that 1018 ISS is safe and pharmacologically active in the respiratory tract of asthmatics but, at this dose regimen, did not inhibit a fall in FEV(1) or other key features of the response to inhaled allergen challenge. This suggests that induction of IFN and IFN-inducible genes alone is not sufficient to inhibit allergen-induced responses in asthmatic subjects.

Nucleic acids of mammalian origin can act as endogenous ligands for Toll-like receptors and may promote systemic lupus erythematosus

Raised serum levels of interferon (IFN)-alpha have been observed in systemic lupus erythematosus (SLE) patients, and these levels are correlated with both disease activity and severity. The origin of this IFN-alpha is still unclear, but increasing evidence suggests the critical involvement of activated plasmacytoid predendritic cells (PDCs). In SLE patients, DNA and RNA viruses, as well as immune complexes (ICs), that consist of autoantibodies specific to self-DNA and RNA protein particles can stimulate production of IFN-alpha. We have developed three series of oligonucleotide (ODN)-based inhibitors of Toll-like receptor (TLR) signaling. These ODNs include inhibitors of TLR9, inhibitors of TLR7 but not TLR9, and sequences that inhibit both TLR7 and TLR9. Specificity of these inhibitors is confirmed by inhibition of IFN-alpha production by PDCs in response to DNA or RNA viruses. We show that mammalian DNA and RNA, in the form of ICs, are potent self-antigens for TLR9 and TLR7, respectively, and induce IFN-alpha production by PDCs. This work suggests that TLRs may have a critical role in the promotion of lupus through the induction of IFN-alpha by PDCs. These inhibitors of TLR signaling thus represent novel therapeutic agents with potential for the treatment of lupus.

Airway generation-specific differences in the spatial distribution of immune cells and cytokines in allergen-challenged rhesus monkeys

BACKGROUND

Accumulation of immune cell populations and their cytokine products within tracheobronchial airways contributes to the pathogenesis of allergic asthma. It has been postulated that peripheral regions of the lung play a more significant role than proximal airways with regard to inflammatory events and airflow obstruction.

OBJECTIVE

To determine whether immune cell populations and associated cytokines are uniformly distributed throughout the conducting airway tree in a non-human primate model of allergic asthma.

METHODS

We used a stereologic approach with a stratified sampling scheme to measure the volume density of immune cells within the epithelium and interstitium of trachea and 4-5 intrapulmonary airway generations from house dust mite (HDM) (Dermatophagoides farinae)-challenged adult monkeys. In conjunction with immune cell distribution profiles, mRNA levels for 21 cytokines/chemokines and three chemokine receptors were evaluated at four different airway generations from microdissected lungs.

RESULTS

In HDM-challenged monkeys, the volume of CD1a+ dendritic cells, CD4+ T helper lymphocytes, CD25+ cells, IgE+ cells, eosinophils, and proliferating cells were significantly increased within airways. All five immune cell types accumulated within airways in unique patterns of distribution, suggesting compartmentalized responses with regard to trafficking. Although cytokine mRNA levels were elevated throughout the conducting airway tree of HDM-challenged animals, the distal airways (terminal and respiratory bronchioles) exhibited the most pronounced up-regulation.

CONCLUSION

These findings demonstrate that key effector immune cell populations and cytokines associated with asthma differentially accumulate within distinct regions and compartments of tracheobronchial airways from allergen-challenged primates.

Immunostimulatory oligonucleotides block allergic airway inflammation by inhibiting Th2 cell activation and IgE-mediated cytokine induction

A single treatment with a CpG-containing immunostimulatory DNA sequence (ISS) given before allergen challenge can inhibit T helper type 2 cell (Th2)–mediated airway responses in animal models of allergic asthma; however, the mechanism of this inhibition remains largely undefined. Here, we demonstrate that airway delivery of ISS before allergen challenge in Th2-primed mice acts in two distinct ways to prevent the allergic responses to this challenge. The first is to prevent induction of cytokines from allergen-specific Th2 cells, as demonstrated by the nearly complete inhibition of Th2 cytokine production, Th2-dependent functional responses, and gene induction patterns. ISS inhibits the Th2 response by rendering lung antigen-presenting cells (APCs) unable to effectively present antigen to Th2 cells, but not to Th1 cells. This loss of APC function correlates with a reduced expression of costimulatory molecules, including programmed cell death ligand (PD-L)1, PD-L2, CD40, CD80, CD86, and inducible T cell costimulator, and of major histocompatibility complex class II on CD11c⁺APCs from the airways of ISS-treated mice. The second important action of ISS is inhibition of immunoglobulin E–dependent release of Th2 cytokines, especially interleukin 4, from basophils and/or mast cells in the airways of Th2-primed mice. Thus, inhibition by ISS of allergic responses can be explained by two novel mechanisms that culminate in the inhibition of the principal sources of type 2 cytokines in the airways.

Human TLR-7-, -8-, and -9-mediated induction of IFN-alpha/beta and -lambda Is IRAK-4 dependent and redundant for protective immunity to viruses

Five TLRs are thought to play an important role in antiviral immunity, sensing viral products and inducing IFN-alpha/beta and -lambda. Surprisingly, patients with a defect of IRAK-4, a critical kinase downstream from TLRs, are resistant to common viruses. We show here that IFN-alpha/beta and -lambda induction via TLR-7, TLR-8, and TLR-9 was abolished in IRAK-4-deficient blood cells. In contrast, IFN-alpha/beta and -lambda were induced normally by TLR-3 and TLR-4 agonists. Moreover, IFN-beta and -lambda were normally induced by TLR-3 agonists and viruses in IRAK-4-deficient fibroblasts. We further show that IFN-alpha/beta and -lambda production in response to 9 of 11 viruses tested was normal or weakly affected in IRAK-4-deficient blood cells. Thus, IRAK-4-deficient patients may control viral infections by TLR-3- and TLR-4-dependent and/or TLR-independent production of IFNs. The TLR-7-, TLR-8-, and TLR-9-dependent induction of IFN-alpha/beta and -lambda is strictly IRAK-4 dependent and paradoxically redundant for protective immunity to most viruses in humans.