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

Induction of protective immune responses at respiratory mucosal sites

Many pathogens enter the host through mucosal sites. Thus, interfering with pathogen entry through local neutralization at mucosal sites therefore is an effective strategy for preventing disease. Mucosally administered vaccines have the potential to induce protective immune responses at mucosal sites. This manuscript delves into some of the latest developments in mucosal vaccination, particularly focusing on advancements in adjuvant technologies and the role of these adjuvants in enhancing vaccine efficacy against respiratory pathogens. It highlights the anatomical and immunological complexities of the respiratory mucosal immune system, emphasizing the significance of mucosal secretory IgA and tissue-resident memory T cells in local immune responses. We further discuss the differences between immune responses induced through traditional parenteral vaccination approaches vs. mucosal administration strategies, and explore the protective advantages offered by immunization through mucosal routes.

CpG oligonucleotides induce acute murine thrombocytopenia dependent on toll-like receptor 9 and spleen tyrosine kinase pathways

BACKGROUND

CpG oligonucleotides (ODNs) are synthetic single-stranded DNA sequences that act as immunostimulants. They have been increasingly used to treat several cancers; however, thrombocytopenia is a potential recognized side effect of some sequences.

OBJECTIVES

We tested the ability of 2 CpG ODNs (ODN 2395 and ISIS 120704) to induce thrombocytopenia when administered to BALB/c mice and determined mechanisms associated with thrombocytopenia.

METHODS

BALB/c mice were prebled and then injected with titrated doses of CpG ODNs, and platelet counts were determined. The mice were treated with intravenous immunoglobulin (IVIg) or various inhibitors and antagonists of toll-like receptor 9 (TLR9) and spleen tyrosine kinase (Syk) to determine their effects on thrombocytopenia.

RESULTS

Compared with saline-treated mice or mice treated with 2'-O-methoxyethyl-modified antisense ODN, both ODN 2395 and ISIS 120704 induced acute dose-dependent thrombocytopenia within 3 and 24 hours, respectively. The thrombocytopenia was associated with significant increases in plasma monocyte chemoattractant protein 1. IVIg administration significantly rescued the CpG ODN-induced thrombocytopenia, as did treatment with either a Syk inhibitor or TLR9 antagonists. In vitro, CpG ODN could activate human platelets and this correlated significantly with enhanced IVIg- and Syk-dependent phagocytosis by THP-1 monocytes.

CONCLUSION

These results suggest that CpG ODNs induce acute inflammatory-associated (IVIg-sensitive) thrombocytopenia that can be alleviated by Syk- or TLR9-blockade, and an IVIg- and Syk-dependent platelet clearance pathway appears primarily responsible for the thrombocytopenia.

Mitochondrial DNA and Inflammation in Alzheimer's Disease

Mitochondrial dysfunction and neuroinflammation are implicated in the pathogenesis of most neurodegenerative diseases, such as Alzheimer's disease (AD). In fact, although a growing number of studies show crosstalk between these two processes, there remain numerous gaps in our knowledge of the mechanisms involved, which requires further clarification. On the one hand, mitochondrial dysfunction may lead to the release of mitochondrial damage-associated molecular patterns (mtDAMPs) which are recognized by microglial immune receptors and contribute to neuroinflammation progression. On the other hand, inflammatory molecules released by glial cells can influence and regulate mitochondrial function. A deeper understanding of these mechanisms may help identify biomarkers and molecular targets useful for the treatment of neurodegenerative diseases. This review of works published in recent years is focused on the description of the mitochondrial contribution to neuroinflammation and neurodegeneration, with particular attention to mitochondrial DNA (mtDNA) and AD.

Adjuvants approved for human use: What do we know and what do we need to know for designing good adjuvants?

Adjuvants represent one of the most significant biotechnological solutions regarding vaccine development, thereby broadening the amount of candidates which can now be used and tested in vaccine formulations targeting various pathogens, as antigens which were previously discarded due to their low or null immunogenicity can now be included. Adjuvant development research has grown side-by-side with an increasing body of knowledge regarding immune systems and their recognition of foreign microorganisms. Alum-derived adjuvants were used in human vaccines for many years, even though complete understanding of their vaccination-related mechanism of action was lacking. The amount of adjuvants approved for human use has increased recently in line with attempts to interact with and stimulate the immune system. This review is aimed at summarising what is known about adjuvants, focusing on those approved for use in humans, their mechanism of action and why they are so necessary for vaccine candidate formulations; it also discusses what the future may hold in this growing research field.

Inflammatory Non-CpG Antisense Oligonucleotides Are Signaling Through TLR9 in Human Burkitt Lymphoma B Bjab Cells

Nucleic acid-based phosphorothioate containing antisense oligonucleotides (PS-ASOs) have the potential to activate cellular innate immune responses, and the level of activation can vary quite dramatically with sequence. Minimizing the degree of proinflammatory effect is one of the main selection criteria for compounds intended to move into clinical trials. While a recently developed human peripheral blood mononuclear cell (hPBMC)-based assay showed excellent ability to detect innate immune active PS-ASOs, which can then be discarded from the developmental process, this assay is highly resource intensive and easily affected by subject variability. This compelled us to develop a more convenient high-throughput assay. In this study, we describe a new in vitro assay, utilizing a cultured human Bjab cell line, which was developed and validated to identify PS-ASOs that may cause innate immune activation. The assay was calibrated to replicate results from the hPBMC assay. The Bjab assay was designed to be high throughput and more convenient by using RT-qPCR readout of mRNA of the chemokine Ccl22. The Bjab assay was also shown to be highly reproducible and to provide a large dynamic range in determining the immune potential of PS-ASOs through comparison to known benchmark PS-ASO controls that were previously shown to be safe or inflammatory in clinical trials. In addition, we demonstrate that Bjab cells can be used to provide mechanistic information on PS-ASO TLR9-dependent innate immune activation.

Early-Stage Identification and Avoidance of Antisense Oligonucleotides Causing Species-Specific Inflammatory Responses in Human Volunteer Peripheral Blood Mononuclear Cells

A human peripheral blood mononuclear cell (PBMC)-based assay was developed to identify antisense oligonucleotide (ASO) with the potential to activate a cellular innate immune response outside of an acceptable level. The development of this assay was initiated when ISIS 353512 targeting the messenger ribonucleic acid for human C-reactive protein (CRP) was tested in a phase I clinical trial, in which healthy human volunteers unexpectedly experienced increases in interleukin-6 (IL-6) and CRP. This level of immune stimulation was not anticipated following rodent and nonhuman primate safety studies in which no evidence of exaggerated proinflammatory effects were observed. The IL-6 increase induced by ISIS 353512 was caused by activation of B cells. The IL-6 induction was inhibited by chloroquine pretreatment of PBMCs and the nature of ASOs suggested that the response is mediated by a Toll-like receptor (TLR), in all likelihood TLR9. While assessing the inter PBMC donor variability, two classes of human PBMC responders to ISIS 353512 were identified (discriminator and nondiscriminators). The discriminator donor PBMCs were shown to produce low level of IL-6 after 24 h in culture, in the absence of ASO treatment. The PBMC assay using discriminator donors was shown to be reproducible, allowing to assess reliably the immune potential of ASOs by comparison to known benchmark ASO controls that were previously shown to be either safe or inflammatory in clinical trials. Clinical Trial registration numbers: NCT00048321 NCT00330330 NCT00519727.

CpG 1018® adjuvant enhances Tdap immune responses against Bordetella pertussis in mice

Bordetella pertussis is the causative agent of whooping cough (pertussis), a severe respiratory disease that can be fatal, particularly in infants. Despite high vaccine coverage, pertussis remains a problem because the currently used DTaP and Tdap vaccines do not completely prevent infection or transmission. It is well established that the alum adjuvant is a potential weakness of the acellular vaccines because the immunity provided by it is short-term. We aimed to evaluate the potential of CpG 1018® adjuvant to improve antibody responses and enhance protection against B. pertussis challenge in a murine model. A titrated range of Tdap vaccine doses were evaluated in order to best identify the adjuvant capability of CpG 1018. Antibody responses to pertussis toxin (PT), filamentous hemagglutinin (FHA), or the whole bacterium were increased due to the inclusion of CpG 1018. In B. pertussis intranasal challenge studies, we observed improved protection and bacterial clearance from the lower respiratory tract due to adding CpG 1018 to 1/20th the human dose of Tdap. Further, we determined that Tdap and Tdap + CpG 1018 were both capable of facilitating clearance of strains that do not express pertactin (PRN^-), which are rising in prevalence. Functional phenotyping of antibodies revealed that the inclusion of CpG 1018 induced more bacterial opsonization and antibodies of the Th1 phenotype (IgG2a and IgG2b). This study demonstrates the potential of adding CpG 1018 to Tdap to improve immunogenicity and protection against B. pertussis compared to the conventional, alum-only adjuvanted Tdap vaccine.

Systemic delivery of a targeted synthetic immunostimulant transforms the immune landscape for effective tumor regression

Promoting immune activation within the tumor microenvironment (TME) is a promising therapeutic strategy to reverse tumor immunosuppression and elicit anti-tumor immunity. To enable tumor-localized immunotherapy following intravenous administration, we chemically conjugated a polyspecific integrin-binding peptide (PIP) to an immunostimulant (Toll-like receptor 9 [TLR9] agonist: CpG) to generate a tumor-targeted immunomodulatory agent, referred to as PIP-CpG. We demonstrate that systemic delivery of PIP-CpG induces tumor regression and enhances therapeutic efficacy compared with untargeted CpG in aggressive murine breast and pancreatic cancer models. Furthermore, PIP-CpG transforms the immune-suppressive TME dominated by myeloid-derived suppressor cells into a lymphocyte-rich TME infiltrated with activated CD8+ T cells, CD4+ T cells, and B cells. Finally, we show that T cells are required for therapeutic efficacy and that PIP-CpG treatment generates tumor-specific CD8+ T cells. These data demonstrate that conjugation to a synthetic tumor-targeted peptide can improve the efficacy of systemically administered immunostimulants and lead to durable anti-tumor immune responses.

Phosphate-mediated coanchoring of RBD immunogens and molecular adjuvants to alum potentiates humoral immunity against SARS-CoV-2

There is a need for additional rapidly scalable, low-cost vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to achieve global vaccination. Aluminum hydroxide (alum) adjuvant is the most widely available vaccine adjuvant but elicits modest humoral responses. We hypothesized that phosphate-mediated coanchoring of the receptor binding domain (RBD) of SARS-CoV-2 together with molecular adjuvants on alum particles could potentiate humoral immunity by promoting extended vaccine kinetics and codelivery of vaccine components to lymph nodes. Modification of RBD immunogens with phosphoserine (pSer) peptides enabled efficient alum binding and slowed antigen clearance, leading to notable increases in germinal center responses and neutralizing antibody titers in mice. Adding phosphate-containing CpG or saponin adjuvants to pSer-RBD:alum immunizations synergistically enhanced vaccine immunogenicity in mice and rhesus macaques, inducing neutralizing responses against SARS-CoV-2 variants. Thus, phosphate-mediated coanchoring of RBD and molecular adjuvants to alum is an effective strategy to enhance the efficacy of SARS-CoV-2 subunit vaccines.

Innate immunity stimulation via CpG oligodeoxynucleotides ameliorates Alzheimer's disease pathology in aged squirrel monkeys

Alzheimer's disease is the most common cause of dementia and the only illness among the top 10 causes of death for which there is no disease-modifying therapy. The failure rate of clinical trials is very high, in part due to the premature translation of successful results in transgenic mouse models to patients. Extensive evidence suggests that dysregulation of innate immunity and microglia/macrophages plays a key role in Alzheimer's disease pathogenesis. Activated resident microglia and peripheral macrophages can display protective or detrimental phenotypes depending on the stimulus and environment. Toll-like receptors (TLRs) are a family of innate immune regulators known to play an important role in governing the phenotypic status of microglia. We have shown in multiple transgenic Alzheimer's disease mouse models that harnessing innate immunity via TLR9 agonist CpG oligodeoxynucleotides (ODNs) modulates age-related defects associated with immune cells and safely reduces amyloid plaques, oligomeric amyloid-β, tau pathology, and cerebral amyloid angiopathy (CAA) while promoting cognitive benefits. In the current study we have used a non-human primate model of sporadic Alzheimer's disease pathology that develops extensive CAA-elderly squirrel monkeys. The major complications in current immunotherapeutic trials for Alzheimer's disease are amyloid-related imaging abnormalities, which are linked to the presence and extent of CAA; hence, the prominence of CAA in elderly squirrel monkeys makes them a valuable model for studying the safety of the CpG ODN-based concept of immunomodulation. We demonstrate that long-term use of Class B CpG ODN 2006 induces a favourable degree of innate immunity stimulation without producing excessive or sustained inflammation, resulting in efficient amelioration of both CAA and tau Alzheimer's disease-related pathologies in association with behavioural improvements and in the absence of microhaemorrhages in aged elderly squirrel monkeys. CpG ODN 2006 has been well established in numerous human trials for a variety of diseases. The present evidence together with our earlier, extensive preclinical research, validates the beneficial therapeutic outcomes and safety of this innovative immunomodulatory approach, increasing the likelihood of CpG ODN therapeutic efficacy in future clinical trials.

Emerging concepts in the science of vaccine adjuvants

Adjuvants are vaccine components that enhance the magnitude, breadth and durability of the immune response. Following its introduction in the 1920s, alum remained the only adjuvant licensed for human use for the next 70 years. Since the 1990s, a further five adjuvants have been included in licensed vaccines, but the molecular mechanisms by which these adjuvants work remain only partially understood. However, a revolution in our understanding of the activation of the innate immune system through pattern recognition receptors (PRRs) is improving the mechanistic understanding of adjuvants, and recent conceptual advances highlight the notion that tissue damage, different forms of cell death, and metabolic and nutrient sensors can all modulate the innate immune system to activate adaptive immunity. Furthermore, recent advances in the use of systems biology to probe the molecular networks driving immune response to vaccines ('systems vaccinology') are revealing mechanistic insights and providing a new paradigm for the vaccine discovery and development process. Here, we review the 'known knowns' and 'known unknowns' of adjuvants, discuss these emerging concepts and highlight how our expanding knowledge about innate immunity and systems vaccinology are revitalizing the science and development of novel adjuvants for use in vaccines against COVID-19 and future pandemics.

The impact of immuno-aging on SARS-CoV-2 vaccine development

The SARS-CoV-2 pandemic has almost 56 million confirmed cases resulting in over 1.3 million deaths as of November 2020. This infection has proved more deadly to older adults (those >65 years of age) and those with immunocompromising conditions. The worldwide population aged 65 years and older is increasing, and the total number of aged individuals will outnumber those younger than 65 years by the year 2050. Aging is associated with a decline in immune function and chronic activation of inflammation that contributes to enhanced viral susceptibility and reduced responses to vaccination. Here we briefly review the pathogenicity of the virus, epidemiology and clinical response, and the underlying mechanisms of human aging in improving vaccination. We review current methods to improve vaccination in the older adults using novel vaccine platforms and adjuvant systems. We conclude by summarizing the existing clinical trials for a SARS-CoV-2 vaccine and discussing how to address the unique challenges for vaccine development presented with an aging immune system.

Pulmonary Delivery of Nanoparticle-Bound Toll-like Receptor 9 Agonist for the Treatment of Metastatic Lung Cancer

CpG oligodeoxynucleotides are potent toll-like receptor (TLR) 9 agonists and have shown promise as anticancer agents in preclinical studies and clinical trials. Binding of CpG to TLR9 initiates a cascade of innate and adaptive immune responses, beginning with activation of dendritic cells and resulting in a range of secondary effects that include the secretion of pro-inflammatory cytokines, activation of natural killer cells, and expansion of T cell populations. Recent literature suggests that local delivery of CpG in tumors results in superior antitumor effects as compared to systemic delivery. In this study, we utilized PRINT (particle replication in nonwetting templates) nanoparticles as a vehicle to deliver CpG into murine lungs through orotracheal instillations. In two murine orthotopic metastasis models of non-small-cell lung cancer-344SQ (lung adenocarcinoma) and KAL-LN2E1 (lung squamous carcinoma), local delivery of PRINT-CpG into the lungs effectively promoted substantial tumor regression and also limited systemic toxicities associated with soluble CpG. Furthermore, cured mice were completely resistant to tumor rechallenge. Additionally, nanodelivery showed extended retention of CpG within the lungs as well as prolonged elevation of antitumor cytokines in the lungs, but no elevated levels of proinflammatory cytokines in the serum. These results demonstrate that PRINT-CpG is a potent nanoplatform for local treatment of lung cancer that has collateral therapeutic effects on systemic disease and an encouraging toxicity profile and may have the potential to treat lung metastasis of other cancer types.

Innate Immune Response against Hepatitis C Virus: Targets for Vaccine Adjuvants

Despite successful treatments, hepatitis C virus (HCV) infections continue to be a significant world health problem. High treatment costs, the high number of undiagnosed individuals, and the difficulty to access to treatment, particularly in marginalized susceptible populations, make it improbable to achieve the global control of the virus in the absence of an effective preventive vaccine. Current vaccine development is mostly focused on weakly immunogenic subunits, such as surface glycoproteins or non-structural proteins, in the case of HCV. Adjuvants are critical components of vaccine formulations that increase immunogenic performance. As we learn more information about how adjuvants work, it is becoming clear that proper stimulation of innate immunity is crucial to achieving a successful immunization. Several hepatic cell types participate in the early innate immune response and the subsequent inflammation and activation of the adaptive response, principally hepatocytes, and antigen-presenting cells (Kupffer cells, and dendritic cells). Innate pattern recognition receptors on these cells, mainly toll-like receptors, are targets for new promising adjuvants. Moreover, complex adjuvants that stimulate different components of the innate immunity are showing encouraging results and are being incorporated in current vaccines. Recent studies on HCV-vaccine adjuvants have shown that the induction of a strong T- and B-cell immune response might be enhanced by choosing the right adjuvant.

A Novel C Type CpG Oligodeoxynucleotide Exhibits Immunostimulatory Activity In Vitro and Enhances Antitumor Effect In Vivo

Background

C type CpG oligodeoxynucleotides (CpG-C ODNs), possessing the features of both A type and B type CpG ODNs, exert a variety of immunostimulatory activities and have been demonstrated as an effective antitumor immunotherapy. Based on the structural characteristics, we designed 20 potential ODNs with the aim of synthesizing an optimal, novel CpG-C ODN specific to human and murine Toll-like receptor 9 (TLR9). We also sought to investigate the in vitro immunostimulatory and in vivo antitumor effects of the novel CpG-C ODN.

Methods

Twenty potential CpG-C ODNs were screened for their ability to secrete interferon (IFN)-α, and interleukin (IL)-6 and tumor necrosis factor (TNF)-α production for the three most promising sequences were assayed in human peripheral blood mononuclear cells (PBMCs) by enzyme-linked immunosorbent assay (ELISA) or cytometric bead array assay. The functions of human and mouse B cells, and cytokine production in mice induced by the most promising sequence, HP06T07, were determined by flow cytometry and ELISA. Growth and morphology of tumor tissues in in vivo murine models inoculated with CT26 cells were analyzed by a growth inhibition assay and immunohistochemistry, respectively.

Results

Among the 20 designed ODNs, HP06T07 significantly induced IFN-α, IL-6, and TNF-α secretion, and promoted B-cell activation and proliferation in a dose-dependent manner in human PBMCs and mouse splenocytes in vitro. Intratumoral injection of HP06T07 notably suppressed tumor growth and prolonged survival in the CT26 subcutaneous mouse model in a dose-dependent manner. HP06T07 administered nine times at 2-day intervals (I2) eradicated tumor growth at both primary and distant sites of CT26 tumors. HP06T07 restrained tumor growth by increasing the infiltration of T cells, NK cells, and plasmacytoid dendritic cells (pDCs).

Conclusions

HP06T07, a novel CpG-C ODN, shows potent immunostimulatory activity in vitro and suppresses tumor growth in the CT26 subcutaneous mouse model.

Unmethylated CpG motif-containing genomic DNA fragment of Bacillus calmette-guerin promotes macrophage functions through TLR9-mediated activation of NF-B and MAPKs signaling pathways

The potency of synthetic CpG-oligo-deoxynucleotides (CpG-ODNs) adjuvants in modulating the immune cell functions through the TLR pathway has been tested and reported previously. However, the cellular signaling involved in the stimulation of macrophages by natural, CpG motif-containing adjuvant and the effector functions modulated by such stimulation has not been well studied. Here, we used in vitro and ex vivo murine macrophage assay systems, and mouse model of in vivo stimulation to explore the signaling pathway and the effector functions mediated by BC01. Results show that BC01 can induce the production of TNF-α and MCP-1 in macrophages by up-regulating the activation of NF-κB and MAPKs signaling pathway, and elevated the expression of MHC-II, CD40, CD80, and CD86. Upon stimulation with BC01, the peritoneal macrophages isolated from TLR9−/− mice produced significantly low levels of pro-inflammatory cytokines, attenuated the activation of NF-κB and MAPKs signaling pathways, and showed reduced phagocytosis. Following in vivo stimulation with BC01, the TLR9−/− mice produced significantly lower levels of pro-inflammatory cytokines in the serum and lymph nodes showed reduced cell proliferation. These results indicate that BC01 is an efficient agonist of TLR9 that can significantly enhance the host-protective immune functions of macrophages.

Bioinspired nucleic acid structures for immune modulation

Nucleic acids have both extensive physiological function and structural potential, rendering them quintessential engineering biomaterials. As carriers of precisely-tunable genetic information, both DNA and RNA can be synthetically generated to form a myriad of structures and to transmit specific genetic code. Importantly, recent studies have shown that DNA and RNA, both in their native and engineered forms, can function as potent regulators of innate immunity, capable of initiating and modulating immune responses. In this review, we highlight recent advances in biomaterials inspired by the various interactions of nucleic acids and the immune system. We discuss key advances in self-assembled structures based on exogenous nucleic acids and engineering approaches to apply endogenous nucleic acids as found in immunogenic cell death and extracellular traps. In addition, we discuss new strategies to control dinucleotide signaling and provide recent examples of biomaterials designed for cancer immunotherapy with STING agonists.

TLRs in pulmonary diseases

Toll-like receptors (TLRs) comprise a clan of proteins involved in identification and triggering a suitable response against pathogenic attacks. As lung is steadily exposed to multiple infectious agents, antigens and host-derived danger signals, the inhabiting stromal and myeloid cells of the lung express an aggregate of TLRs which perceive the endogenously derived damage-associated molecular patterns (DAMPs) along with pathogen associated molecular patterns (PAMPs) and trigger the TLR-associated signalling events involved in host defence. Thus, they form an imperative component of host defence activation in case of microbial infections as well as non-infectious pulmonary disorders such as interstitial lung disease, acute lung injury and airways disease, such as COPD and asthma. They also play an equally important role in lung cancer. Targeting the TLR signalling network would pave ways to the design of more reliable and effective vaccines against infectious agents and control deadly infections, desensitize allergens and reduce inflammation. Moreover, TLR agonists may act as adjuvants by increasing the efficiency of cancer vaccines, thereby contributing their role in treatment of lung cancer too. Overall, TLRs present a compelling and expeditiously bolstered area of research and addressing their signalling events would be of significant use in pulmonary diseases.

Potential Novel Approaches to Understand the Pathogenesis and Treat Alzheimer's Disease

There is growing genetic and proteomic data highlighting the complexity of Alzheimer's disease (AD) pathogenesis. Greater use of unbiased "omics" approaches is being increasingly recognized as essential for the future development of effective AD research, that need to better reflect the multiple distinct pathway abnormalities that can drive AD pathology. The track record of success in AD clinical trials thus far has been very poor. In part, this high failure rate has been related to the premature translation of highly successful results in animal models that mirror only limited aspects of AD pathology to humans. We highlight our recent efforts to increase use of human tissue to gain a better understanding of the AD pathogenesis subtype variety and to develop several distinct therapeutic approaches tailored to address this diversity. These therapeutic approaches include the blocking of the Aβ/apoE interaction, stimulation of innate immunity, and the simultaneous blocking of Aβ/tau oligomer toxicity. We believe that future successful therapeutic approaches will need to be combined to better reflect the complexity of the abnormal pathways triggered in AD pathogenesis.

Future horizons in Alzheimer's disease research

There are growing genetic, transcriptomic and proteomic data pointing to the complexity of Alzheimer's disease (AD) pathogenesis. Unbiased "omics" approaches are essential for the future development of effective AD research, which will need to be combined and personalized, given that multiple distinct pathways can drive AD pathology. It is essential to gain a better understanding of the AD pathogenesis subtype variety and to develop several distinct therapeutic approaches tailored to address this diversity, as well as the common presence of mixed pathologies. These nonmutually exclusive therapeutic approaches include the targeting of multiple toxic oligomeric species concurrently, targeting the apolipoprotein E/amyloid β interaction and the modulation of innate immunity, as well as more "out of the box" ideas such as targeting infectious agents that may play a role in AD.

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.

NGF steers microglia toward a neuroprotective phenotype

Microglia are the sentinels of the brain but a clear understanding of the factors that modulate their activation in physiological and pathological conditions is still lacking. Here we demonstrate that Nerve Growth Factor (NGF) acts on microglia by steering them toward a neuroprotective and anti-inflammatory phenotype. We show that microglial cells express functional NGF receptors in vitro and ex vivo. Our transcriptomic analysis reveals how, in primary microglia, NGF treatment leads to a modulation of motility, phagocytosis and degradation pathways. At the functional level, NGF induces an increase in membrane dynamics and macropinocytosis and, in vivo, it activates an outward rectifying current that appears to modulate glutamatergic neurotransmission in nearby neurons. Since microglia are supposed to be a major player in Aβ peptide clearance in the brain, we tested the effects of NGF on its phagocytosis. NGF was shown to promote TrkA-mediated engulfment of Aβ by microglia, and to enhance its degradation. Additionally, the proinflammatory activation induced by Aβ treatment is counteracted by the concomitant administration of NGF. Moreover, by acting specifically on microglia, NGF protects neurons from the Aβ-induced loss of dendritic spines and inhibition of long term potentiation. Finally, in an ex-vivo setup of acute brain slices, we observed a similar increase in Aβ engulfment by microglial cells under the influence of NGF. Our work substantiates a role for NGF in the regulation of microglial homeostatic activities and points toward this neurotrophin as a neuroprotective agent in Aβ accumulation pathologies, via its anti-inflammatory activity on microglia.

Intracerebroventricular Administration of a 2'-O-Methyl Phosphorothioate Antisense Oligonucleotide Results in Activation of the Innate Immune System in Mouse Brain

Antisense oligonucleotides (AONs) are versatile molecules that can be used to modulate gene expression by binding to RNA. The therapeutic potential of AONs appears particularly high in the central nervous system, due to excellent distribution and uptake in brain cells, as well as good tolerability in clinical trials thus far. Nonetheless, immune stimulation in response to AON treatment in the brain remains a concern. For this reason we performed RNA sequencing analysis of brain tissue from mice treated intracerebroventricularly with phosphorothioate, 2′-O-methyl modified AONs. A significant upregulation of immune system associated genes was observed in brains of AON treated mice, with the striatum showing largest transcriptional changes. Strongest upregulation was seen for the antiviral enzyme 2′-5′-oligoadenylate synthase-like protein 2 (Oasl2) and Bone marrow stromal antigen 2 (Bst2). Histological analysis confirmed activation of microglia and astrocytes in striatum. The upregulation of immune system associated genes was detectable for at least 2 months after the last AON administration, consistent with a continuous immune response to the AON.

Development of the CpG Adjuvant 1018: A Case Study

The development of aluminum salts (alum) as vaccine adjuvants was an empirical process with little understanding of the mechanism of action and, with decades of use, it has become clear that there is a need for alternatives where alum-based adjuvants are suboptimal. Oligonucleotides containing unmethylated CpG sequences represent one alternative as they are potent stimulators of the vertebrate innate immune system through activation of Toll-like receptor-9. This chapter outlines the methods used by Dynavax Technologies to progress a CpG-containing oligonucleotide sequence termed 1018 through preclinical and clinical testing as an adjuvant for immunization against hepatitis B virus (HBV). 1018 is a short (22-mer) oligonucleotide sequence containing CpG motifs active in both rodents and primates. Preclinical testing of hepatitis B surface antigen (HBsAg) + 1018 in comparison to HBsAg + alum demonstrated induction of substantially higher antibody titers and a favorable safety profile for 1018. Most importantly, clinical studies with HBsAg vaccination consistently demonstrate more rapid induction of protective antibody titers with 1018 compared to alum in all populations studied, including groups that are harder to immunize such as the elderly and immunocompromised individuals. These studies represent the basis for use of the CpG-motif-containing oligonucleotide 1018 as an improved adjuvant for HBsAg immunogenicity. HBsAg + 1018 (HEPLISAV-B^™) is currently in late-stage clinical testing for prophylactic immunization against HBV.

Adjuvants

Developing new vaccines against emerging pathogens or pathogens where variability of antigenic sites presents a challenge, the inclusion of stimulators of the innate immune system is critical to mature the immune response in a way that allows high avidity recognition while preserving the ability to react to drifted serovars. The innate immune system is an ancient mechanism for recognition of nonself and the first line of defense against pathogen insult. By triggering innate receptors, adjuvants can boost responses to vaccines and enhance the quality and magnitude of the resulting immune response. This chapter: (1) describes the innate immune system, (2) provides examples of how adjuvants are formulated to optimize their effectiveness, and (3) presents examples of how adjuvants can improve outcomes of immunization.

Human innate responses and adjuvant activity of TLR ligands in vivo in mice reconstituted with a human immune system

TLR ligands (TLR-Ls) represent a class of novel vaccine adjuvants. However, their immunologic effects in humans remain poorly defined in vivo. Using a humanized mouse model with a functional human immune system, we investigated how different TLR-Ls stimulated human innate immune response in vivo and their applications as vaccine adjuvants for enhancing human cellular immune response. We found that splenocytes from humanized mice showed identical responses to various TLR-Ls as human PBMCs in vitro. To our surprise, various TLR-Ls stimulated human cytokines and chemokines differently in vivo compared to that in vitro. For example, CpG-A was most efficient to induce IFN-α production in vitro. In contrast, CpG-B, R848 and Poly I:C stimulated much more IFN-α than CpG-A in vivo. Importantly, the human innate immune response to specific TLR-Ls in humanized mice was different from that reported in C57BL/6 mice, but similar to that reported in nonhuman primates. Furthermore, we found that different TLR-Ls distinctively activated and mobilized human plasmacytoid dendritic cells (pDCs), myeloid DCs (mDCs) and monocytes in different organs. Finally, we showed that, as adjuvants, CpG-B, R848 and Poly I:C can all enhance antigen specific CD4+ T cell response, while only R848 and Poly I:C induced CD8+ cytotoxic T cells response to a CD40-targeting HIV vaccine in humanized mice, correlated with their ability to activate human mDCs but not pDCs. We conclude that humanized mice serve as a highly relevant model to evaluate and rank the human immunologic effects of novel adjuvants in vivo prior to testing in humans.

Stimulating Innate Immunity to Enhance Radiation Therapy-Induced Tumor Control

Novel ligands that target Toll-like receptors and other innate recognition pathways represent a potent strategy for modulating innate immunity to generate antitumor immunity. Although many of the current clinically successful immunotherapies target adaptive T-cell responses, both preclinical and clinical studies suggest that adjuvants have the potential to enhance the scope and efficacy of cancer immunotherapy. Radiation may be a particularly good partner to combine with innate immune therapies, because it is a highly efficient means to kill cancer cells but may fail to send the appropriate inflammatory signals needed to act as an efficient endogenous vaccine. This may explain why although radiation therapy is a highly used cancer treatment, true abscopal effects-regression of disease outside the field without additional systemic therapy-are extremely rare. This review focuses on efforts to combine innate immune stimuli as adjuvants with radiation, creating a distinct and complementary approach from T cell-targeted therapies to enhance antitumor immunity.

Innate Immunity Stimulation via Toll-Like Receptor 9 Ameliorates Vascular Amyloid Pathology in Tg-SwDI Mice with Associated Cognitive Benefits

Alzheimer's disease (AD) is characterized by the presence of parenchymal amyloid-β (Aβ) plaques, cerebral amyloid angiopathy (CAA) and neurofibrillary tangles. Currently there are no effective treatments for AD. Immunotherapeutic approaches under development are hampered by complications related to ineffectual clearance of CAA. Genome-wide association studies have demonstrated the importance of microglia in AD pathogenesis. Microglia are the primary innate immune cells of the brain. Depending on their activation state and environment, microglia can be beneficial or detrimental. In our prior work, we showed that stimulation of innate immunity with Toll-like receptor 9 agonist, class B CpG (cytosine-phosphate-guanine) oligodeoxynucleotides (ODNs), can reduce amyloid and tau pathologies without causing toxicity in Tg2576 and 3xTg-AD mouse models. However, these transgenic mice have relatively little CAA. In the current study, we evaluated the therapeutic profile of CpG ODN in a triple transgenic mouse model, Tg-SwDI, with abundant vascular amyloid, in association with low levels of parenchymal amyloid deposits. Peripheral administration of CpG ODN, both before and after the development of CAA, negated short-term memory deficits, as assessed by object-recognition tests, and was effective at improving spatial and working memory evaluated using a radial arm maze. These findings were associated with significant reductions of CAA pathology lacking adverse effects. Together, our extensive evidence suggests that this innovative immunomodulation may be a safe approach to ameliorate all hallmarks of AD pathology, supporting the potential clinical applicability of CpG ODN.

SIGNIFICANCE STATEMENT

Recent genetic studies have underscored the emerging role of microglia in Alzheimer's disease (AD) pathogenesis. Microglia lose their amyloid-β-clearing capabilities with age and as AD progresses. Therefore, the ability to modulate microglia profiles offers a promising therapeutic avenue for reducing AD pathology. Current immunotherapeutic approaches have been limited by poor clearance of a core AD lesion, cerebral amyloid angiopathy (CAA). The present study used Tg-SwDI mice, which have extensive CAA. We found that stimulation of the innate immune system and microglia/macrophage activation via Toll-like receptor 9 using CpG (cytosine-phosphate-guanine) oligodeoxynucleotides (ODNs) leads to cognitive improvements and CAA reduction, without associated toxicity. Our data indicate that this novel concept of immunomodulation represents a safer method to reduce all aspects of AD pathology and provide essential information for potential clinical use of CpG ODN.

Extracellular histones, cell-free DNA, or nucleosomes: differences in immunostimulation

In inflammation, extensive cell death may occur, which results in the release of chromatin components into the extracellular environment. Individually, the purified chromatin components double stranded (ds)DNA and histones have been demonstrated, both in vitro and in vivo, to display various immunostimulatory effects, for example, histones induce cytotoxicity and proinflammatory signaling through toll-like receptor (TLR)2 and 4, while DNA induces signaling through TLR9 and intracellular nucleic acid sensing mechanisms. However, DNA and histones are organized in nucleosomes in the nucleus, and evidence suggests that nucleosomes are released as such in inflammation. The cytotoxicity and proinflammatory signaling induced by nucleosomes have not been studied as extensively as the separate effects brought about by histones and dsDNA, and there appear to be some marked differences. Remarkably, little distinction between the different forms in which histones circulate has been made throughout literature. This is partly due to the limitations of existing techniques to differentiate between histones in their free or DNA-bound form. Here we review the current understanding of immunostimulation induced by extracellular histones, dsDNA and nucleosomes, and discuss the importance of techniques that in their detection differentiate between these different chromatin components.

Sensing of dangerous DNA

The presence of damaged and microbial DNA can pose a threat to the survival of organisms. Cells express various sensors that recognize specific aspects of such potentially dangerous DNA. Recognition of damaged or microbial DNA by sensors induces cellular processes that are important for DNA repair and inflammation. Here, we review recent evidence that the cellular response to DNA damage and microbial DNA are tightly intertwined. We also discuss insights into the parameters that enable DNA sensors to distinguish damaged and microbial DNA from DNA present in healthy cells.

A small molecule inhibitor for ATPase activity of Hsp70 and Hsc70 enhances the immune response to protein antigens

The ATPase activities of Hsp70 and Hsc70 are known to be responsible for regulation of various biological processes. However, little is known about the roles of Hsp70 and Hsc70 in modulation of immune responses to antigens. In the present study, we investigated the effect of apoptozole (Az), a small molecule inhibitor of Hsp70 and Hsc70, on immune responses to protein antigens. The results show that mice administered with both protein antigen and Az produce more antibodies than those treated with antigen alone, showing that Az enhances immune responses to administered antigens. Treatment of mice with Az elicits production of antibodies with a high IgG2c/IgG1 ratio and stimulates the release of Th1 and Th2-type cytokines, suggesting that Az activates the Th1 and Th2 immune responses. The observations made in the present study suggest that inhibition of Hsp70 and Hsc70 activities could be a novel strategy designing small molecule-based adjuvants in protein 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.

CpGB DNA activates dermal macrophages and specifically recruits inflammatory monocytes into the skin

Toll-like receptor 9 (TLR9) drives innate immune responses after recognition of foreign or endogenous DNA containing unmethylated CpG motifs. DNA-mediated TLR9 activation is highly implicated in the pathogenesis of several autoimmune skin diseases, yet its contribution to the inflammation seen in these diseases remains unclear. In this study, TLR9 ligand, CpGB DNA, was administered to mice via a subcutaneous osmotic pump with treatment lasting 1 or 4 weeks. Gene expression and immunofluorescence analyses were used to determine chemokine expression and cell recruitment in the skin surrounding the pump outlet. CpGB DNA skin treatment dramatically induced a marked influx of CD11b+ F4/80+ macrophages, increasing over 4 weeks of treatment, and induction of IFNγ and TNFα expression. Chemokines, CCL2, CCL4, CCL5, CXCL9 and CXCL10, were highly induced in CpGB DNA-treated skin, although abrogation of these signalling pathways individually did not alter macrophage accumulation. Flow cytometry analysis showed that TLR9 activation in the skin increased circulating CD11b+ CD115+ Ly6C(hi) inflammatory monocytes following 1 week of CpGB DNA treatment. Additionally, skin-resident CD11b+ cells were found to initially take up subcutaneous CpGB DNA and propagate the subsequent immune response. Using diphtheria toxin-induced monocyte depletion mouse model, gene expression analysis demonstrated that CD11b+ cells are responsible for the CpGB DNA-induced cytokine and chemokine response. Overall, these data demonstrate that chronic TLR9 activation induces a specific inflammatory response, ultimately leading to a striking and selective accumulation of macrophages in the skin.

Absent in melanoma 2 triggers a heightened inflammasome response in ascitic fluid macrophages of patients with cirrhosis

BACKGROUND & AIMS

Inflammation is a common event in the pathogenesis of liver cirrhosis. The inflammasome pathway has acquired significant relevance in the pathogenesis of inflammation, but its role in the inflammatory response in patients with decompensated cirrhosis remains unexplored.

METHODS

We performed a prospective study in which 44 patients with decompensated cirrhosis and 12 healthy volunteers were included. We isolated macrophages from blood and ascitic fluid and assessed the expression and activation of the inflammasome, its response to priming by bacterial products, and its association with the degree of liver disease.

RESULTS

Macrophages from sterile ascitic fluids showed constitutive activation of caspase-1 and a marked increase in the expression of IL-1β, IL-18, and absent in melanoma 2 (AIM2) when compared to blood macrophages. Pre-stimulation of blood-derived macrophages from cirrhotic patients with bacterial DNA increased the expression of AIM2 and induced a higher AIM2-mediated inflammasome response than priming with other bacterial products such as lipopolysaccharide. By contrast, activation of the AIM2 inflammasome did not require a priming signal in ascitic fluid-derived macrophages, demonstrating the preactivated state of the inflammasome in these cells. Last, higher IL-1β and IL-18 production by ascitic fluid macrophages correlated with a more advanced Child-Pugh score.

CONCLUSIONS

The inflammasome is highly activated in the ascitic fluid of cirrhotic patients, which may explain the exacerbated inflammatory response observed in these patients under non-infected conditions. Clinically, activation of the inflammasome is associated with a higher degree of liver disease.

Oxidative modification enhances the immunostimulatory effects of extracellular mitochondrial DNA on plasmacytoid dendritic cells

Inflammation is associated with oxidative stress and characterized by elevated levels of damage-associated molecular pattern (DAMP) molecules released from injured or even living cells into the surrounding microenvironment. One of these endogenous danger signals is the extracellular mitochondrial DNA (mtDNA) containing evolutionary conserved unmethylated CpG repeats. Increased levels of reactive oxygen species (ROS) generated by recruited inflammatory cells modify mtDNA oxidatively, resulting primarily in accumulation of 8-oxo-7,8-dihydroguanine (8-oxoG) lesions. In this study, we examined the impact of native and oxidatively modified mtDNAs on the phenotypic and functional properties of plasmacytoid dendritic cells (pDCs), which possess a fundamental role in the regulation of inflammation and T cell immunity. Treatment of human primary pDCs with native mtDNA up-regulated the expression of a costimulatory molecule (CD86), a specific maturation marker (CD83), and a main antigen-presenting molecule (HLA-DQ) on the cell surface, as well as increased TNF-α and IL-8 production from the cells. These effects were more apparent when pDCs were exposed to oxidatively modified mtDNA. Neither native nor oxidized mtDNA molecules were able to induce interferon (IFN)-α secretion from pDCs unless they formed a complex with human cathelicidin LL-37, an antimicrobial peptide. Interestingly, simultaneous administration of a Toll-like receptor (TLR)9 antagonist abrogated the effects of both native and oxidized mtDNAs on human pDCs. In a murine model, oxidized mtDNA also proved a more potent activator of pDCs compared to the native form, except for induction of IFN-α production. Collectively, we demonstrate here for the first time that elevated levels of 8-oxoG bases in the extracellular mtDNA induced by oxidative stress increase the immunostimulatory capacity of mtDNA on pDCs.

Safety, tolerability, and biomarkers of the treatment of mice with aerosolized Toll-like receptor ligands

We have previously discovered a synergistically therapeutic combination of two Toll-like receptor ligands, an oligodeoxynucleotide (ODN) and Pam2CSK4. Aerosolization of these ligands stimulates innate immunity within the lungs to prevent pneumonia from bacterial and viral pathogens. Here we examined the safety and tolerability of this treatment in mice, and characterized the expression of biomarkers of innate immune activation. We found that neutrophils appeared in lung lavage fluid 4 h after treatment, reached a peak at 48 h, and resolved by 7 days. The peak of neutrophil influx was accompanied by a small increase in lung permeability. Despite the abundance of neutrophils in lung lavage fluid, only rare neutrophils were visible histopathologically in the interstitium surrounding bronchi and veins and none were visible in alveolar airspaces. The cytokines interleukin 6 (IL-6), tumour necrosis factor, and Chemokine (C-X-C motif) ligand 2 rose several hundred-fold in lung lavage fluid 4 h after treatment in a dose-dependent and synergistic manner, providing useful biomarkers of lung activation. IL-6 rose fivefold in serum with delayed kinetics compared to its rise in lavage fluid, and might serve as a systemic biomarker of immune activation of the lungs. The dose–response relationship of lavage fluid cytokines was preserved in mice that underwent myeloablative treatment with cytosine arabinoside to model the treatment of hematologic malignancy. There were no overt signs of distress in mice treated with ODN/Pam2CSK4 in doses up to eightfold the therapeutic dose, and no changes in temperature, respiratory rate, or behavioral signs of sickness including sugar water preference, food disappearance, cage exploration or social interaction, though there was a small degree of transient weight loss. We conclude that treatment with aerosolized ODN/Pam2CSK4 is well tolerated in mice, and that innate immune activation of the lungs can be monitored by the measurement of inflammatory cytokines in lung lavage fluid and serum.

Innate immune protection against infectious diseases by pulmonary administration of a phospholipid-conjugated TLR7 ligand

Pulmonary administration of Toll-like receptor (TLR) ligands protects hosts from inhaled pathogens. However, systemic side effects induced by TLR stimulation limit clinical development. Here, a small-molecule TLR7 ligand conjugated with phospholipid, 1V270 (also designated TMX201), was tested for innate immune activation and its ability to prevent pulmonary infection in mice. We hypothesized that phospholipid conjugation would increase internalization by immune cells and localize the compound in the lungs, thus avoiding side effects due to systemic cytokine release. Pulmonary 1V270 administration increased innate cytokines and chemokines in bronchial alveolar lavage fluids, but neither caused systemic induction of cytokines nor B cell proliferation in distant lymphoid organs. 1V270 activated pulmonary CD11c+ dendritic cells, which migrated to local lymph nodes. However, there was minimal cell infiltration into the pulmonary parenchyma. Prophylactic administration of 1V270 significantly protected mice from lethal infection with Bacillus anthracis, Venezuelan equine encephalitis virus and H1N1 influenza virus. The maximum tolerated dose of 1V270 by pulmonary administration was 75 times the effective therapeutic dose. Therefore, pulmonary 1V270 treatment can protect the host from different infectious agents by stimulating local innate immune responses while exhibiting an excellent safety profile.

Intratumoral delivery of low doses of anti-CD40 mAb combined with monophosphoryl lipid a induces local and systemic antitumor effects in immunocompetent and T cell-deficient mice

In this study, an agonistic anti-CD40 monoclonal antibody was combined with monophosphoryl lipid A (MPL), a nontoxic derivative of lipopolysaccharide and agonist of toll-like receptor-4, to assess the immunomodulatory and antitumor synergy between the 2 agents in mice. Anti-CD40 was capable of priming macrophages to subsequent ex vivo activation by MPL in immunocompetent and T-cell-depleted mice. Intraperitoneal injections of anti-CD40+MPL induced additive to synergistic suppression of poorly immunogenic B16-F10 melanoma growing subcutaneously in syngeneic mice. When anti-CD40+MPL were injected directly into the subcutaneous tumor, the combination treatment was more effective, even with a 25-fold reduction in dose. Low-dose intratumoral treatment also slowed the growth of a secondary tumor growing simultaneously at a distant, untreated site. Antitumor effects were also induced in severe combined immunodeficiency mice and in T-cell-depleted C57BL/6 mice. Taken together, our results show that the antitumor effects of anti-CD40 are enhanced by subsequent treatment with MPL, even in T-cell-deficient hosts. These preclinical data suggest that an anti-CD40+MPL combined regimen is appropriate for clinical testing in human patients, including cancer patients who may be immunosuppressed from prior chemotherapy.

Accelerating next-generation vaccine development for global disease prevention

Vaccines are among the greatest successes in the history of public health. However, past strategies for vaccine development are unlikely to succeed in the future against major global diseases such as AIDS, tuberculosis, and malaria. For such diseases, the correlates of protection are poorly defined and the pathogens evade immune detection and/or exhibit extensive genetic variability. Recent advances have heralded in a new era of vaccine discovery. However, translation of these advances into vaccines remains impeded by lack of understanding of key vaccinology principles in humans. We review these advances toward vaccine discovery and suggest that for accelerating successful vaccine development, new human immunology-based clinical research initiatives be implemented with the goal of elucidating and more effectively generating vaccine-induced protective immune responses.

Anti-tumor activity of CpG-ODN aerosol in mouse lung metastases

Studies in preclinical models have demonstrated the superior anti-tumor effect of CpG oligodeoxynucleotides (CpG-ODN) when administered at the tumor site rather than systemically. We evaluated the effect of aerosolized CpG-ODN on lung metastases in mice injected with immunogenic N202.1A mammary carcinoma cells or weakly immunogenic B16 melanoma cells. Upon reaching the bronchoalveolar space, aerosolized CpG-ODN activated a local immune response, as indicated by production of IL-12p40, IFN-γ and IL-1β and by recruitment and maturation of DC cells in bronchoalveolar lavage fluid of mice. Treatment with aerosolized CpG-ODN induced an expansion of CD4+ cells in lung and was more efficacious than systemic i.p. administration against experimental lung metastases of immunogenic N202.1A mammary carcinoma cells, whereas only i.p. delivery of CpG-ODN provided anti-tumor activity, which correlated with NK cell expansion in the lung, against lung metastases of the poorly immunogenic B16 melanoma. The inefficacy of aerosol therapy to induce NK expansion was related to the presence of immunosuppressive macrophages in B16 tumor-bearing lungs, as mice depleted of these cells by clodronate treatment responded to aerosol CpG-ODN through expansion of the NK cell population and significantly reduced numbers of lung metastases. Our results indicate that tumor immunogenicity and the tumor-induced immunosuppressive environment are critical factors to the success of CpG therapy in the lung, and point to the value of routine sampling of the lung immune environment in defining an optimal immunotherapeutic strategy.

Nucleic acid sensing at the interface between innate and adaptive immunity in vaccination

The demand is currently high for new vaccination strategies, particularly to help combat problematic intracellular pathogens, such as HIV and malarial parasites. In the past decade, the identification of host receptors that recognize pathogen-derived nucleic acids has revealed an essential role for nucleic acid sensing in the triggering of immunity to intracellular pathogens. This Review first addresses our current understanding of the nucleic acid-sensing immune machinery. We then explain how the study of nucleic acid-sensing mechanisms not only has revealed their central role in driving the responses mediated by many current vaccines, but is also revealing how they could be harnessed for the design of new vaccines.

Encapsulating immunostimulatory CpG oligonucleotides in listeriolysin O-liposomes promotes a Th1-type response and CTL activity

Immunostimulatory sequences (ISS) are short DNA sequences containing unmethylated CpG dimers that have multiple effects on the host immune system, including the ability to stimulate antigen-specific cytotoxic T lymphocytes (CTLs) and drive Th1-type immune responses. Listeriolysin O (LLO)-containing pH-sensitive liposomes have been shown to efficiently deliver macromolecules to the cytosol of APCs and efficiently stimulate CTLs. We hypothesized that encapsulating ISS-oligodeoxyribonucleotides (ODNs) in this delivery system would enhance the cell-mediated immune response and skew Th1-type responses in protein antigen-based vaccination utilizing LLO-liposomes. In vitro studies indicated that coencapsulation of ISS in LLO-liposomes engendered activation of the NF-κB pathway while maintaining the efficient cytosolic delivery of antigen mediated by the coencapsulated LLO. Antigen-specific CTL responses monitored by using the model antigen ovalbumin (OVA) in mice were enhanced when mice were immunized with OVA and ISS-ODN-containing LLO-liposomes compared with those immunized with OVA-containing LLO-liposomes. The enhanced immune responses were of the Th1-type as monitored by the robust OVA-specific IgG2a induction and the OVA CD8 peptide-stimulated IFN-γ secretion. Our study suggests that including ISS-ODN in LLO-containing pH-sensitive liposomes yields a vaccine delivery system that enhances the cell-mediated immune response and skews this response toward the Th1-type.

Dual role of Toll-like receptors in asthma and chronic obstructive pulmonary disease

During the last decade, significant research has been focused on Toll-like receptors (TLRs) in the pathogenesis of airway diseases. TLRs are pattern recognition receptors that play pivotal roles in the detection of and response to pathogens. Because of the involvement of TLRs in innate and adaptive immunity, these receptors are currently being exploited as possible targets for drug development. Asthma and chronic obstructive pulmonary disease (COPD) are chronic inflammatory airway diseases in which innate and adaptive immunity play an important role. To date, asthma is the most common chronic disease in children aged 5 years and older. COPD is prevalent amongst the elderly and is currently the fifth-leading cause of death worldwide with still-growing prevalence. Both of these inflammatory diseases result in shortness of breath, which is treated, often ineffectively, with bronchodilators and glucocorticosteroids. Symptomatic treatment approaches are similar for both diseases; however, the underlying immunological mechanisms differ greatly. There is a clear need for improved treatment specific for asthma and for COPD. This review provides an update on the role of TLRs in asthma and in COPD and discusses the merits and difficulties of targeting these proteins as novel treatment strategies for airway diseases. TLR agonist, TLR adjuvant, and TLR antagonist therapies could all be argued to be effective in airway disease management. Because of a possible dual role of TLRs in airway diseases with shared symptoms and risk factors but different immunological mechanisms, caution should be taken while designing pulmonary TLR-based therapies.

Absence of unspecific innate immune cell activation by GATA-3-specific DNAzymes

DNAzymes of the 10-23 family represent an important class of antisense molecules with implications for therapeutic treatment of diseases. These molecules are single-stranded oligodeoxynucleotides combining the high specificity of oligonucleotide base pairing with an inherent RNA-cleaving enzymatic activity. However, like other oligonucleotide-based molecules these substances might exert so-called off-target effects, which have not been investigated so far for this molecule class. Therefore, the present study investigates putative off-target effects of DNAzymes on innate immune mechanisms using GATA-3-specific DNAzymes that have recently been developed as novel therapeutic approach for the treatment of allergic diseases including allergic asthma. The conserved catalytic domain of 10-23 DNAzymes contains a CpG motif that may stimulate innate immune cells via Toll-like receptor 9 (TLR-9). Therefore, potential TLR-9-mediated as well as TLR-9 independent cell activation was investigated using TLR-9-transfected HEK293 cells, macrophage cell lines and primary innate immune cells. Furthermore, putative effects of GATA-3-specific DNAzymes on the activation of neutrophil granulocytes and degranulation of mast cells/basophils were analyzed. In summary, no innate immune cell-stimulating activities of the tested DNAzymes were observed in any of the systems. Consequently, use of GATA-3-specific DNAzymes may represent a novel and highly specific approach for the treatment of allergic diseases.

CpG still rocks! Update on an accidental drug

The discovery of the CpG motif in 1995 led to a change in the perception of the immune stimulatory effects of oligodeoxynucleotides (ODN) from an unwanted nonspecific effect to a highly evolved immune defense that can be selectively triggered for a wide range of therapeutic applications. Over the last decade dozens of human clinical trials have been conducted with different CpG ODN in thousands of humans for applications ranging from vaccine adjuvant to immunotherapies for allergy, cancer, and infectious diseases. Along with many positive results have come some failures showing the limitations of several therapeutic approaches. This review summarizes these results to provide an overview of the clinical development of CpG ODN.

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.

The role of Bcl-xL in mouse RPE cell survival

PURPOSE. Retinal pigment epithelial (RPE) cell survival plays a critical role in normal physiology and in retinal diseases, such as age-related macular degeneration (AMD) and proliferative vitreoretinopathy (PVR). We have previously demonstrated that Bcl-x(L) is an important cell survival protein in human RPE (hRPE) cells. Herein, we determined the role of Bcl-x(L) as a survival protein in mouse RPE (mRPE) cells. METHODS. Survival factor gene expression and Bcl-x(L) protein distribution were determined using qRT-PCR and immunohistochemistry, respectively. Cultured mRPE cells were transfected with two modified 2'-O-methoxyethoxy antisense oligonucleotides (ASOs): Bcl-x(L)-mismatched control and Bcl-x(L)-specific. Bcl-x(L) protein levels were analyzed using Western blot. To determine the effects of survival factor regulation in mRPE cells, cultured cells were treated for 24 hours with mouse TNF-α, human IL-1β, and human TNF-α. RESULTS. Bcl-x(L) was the most highly expressed survival factor in both mouse eyecup and cultured mRPE cells, whereas Bax was the most highly expressed antisurvival factor. Bcl-x(L) was expressed in the RPE layer, and the distribution among the retinal layers was similar to that observed in human eyecups. IL-1β and TNF-α had minimal effect on Bcl-x(L) and Bax expression and strongly upregulated Traf-1. Transfection with Bcl-x(L)-specific ASO resulted in markedly diminished Bcl-x(L) gene expression, Bcl-x(L) protein levels, and cell number. CONCLUSIONS. Bcl-x(L) is the most highly expressed survival gene in mRPE cells and is essential for mRPE cell survival. Our data suggest that mouse tissue is an appropriate model for investigations of RPE survival factor genes.