Toll-like receptor ligands and atopy: a coin with at least two sides

Intranasal administration of a synthetic TLR4 agonist INI-2004 significantly reduces allergy symptoms following therapeutic administration in a murine model of allergic sensitization

Introduction

Atopic diseases have been steadily increasing over the past decades and effective disease-modifying treatment options are urgently needed. These studies introduce a novel synthetic Toll-like receptor 4 (TLR4) agonist, INI-2004, with remarkable efficacy as a therapeutic intranasal treatment for seasonal allergic rhinitis.

Methods

Using a murine airway allergic sensitization model, the impact of INI-2004 on allergic responses was assessed.

Results

One or two intranasal doses of INI-2004 significantly reduced airway resistance, eosinophil influx, and Th2 cytokine production - providing strong evidence of allergic desensitization. Further investigations revealed that a liposomal formulation of INI-2004 exhibited better safety and efficacy profiles compared to aqueous formulations. Importantly, the liposomal formulation demonstrated a 1000-fold increase in the maximum tolerated intravenous dose in pigs. Pre-clinical GLP toxicology studies in rats and pigs confirmed the safety of liposomal INI-2004, supporting its selection for human clinical trials.

Discussion

These findings lay the groundwork for the ongoing clinical evaluation of INI-2004 in allergic rhinitis as a stand-alone therapy for individuals poly-sensitized to multiple seasonal allergens. The study underscores the significance of innovative immunotherapy approaches in reshaping the landscape of allergic rhinitis management.

Radiation-Detoxified Form of Endotoxin Effectively Activates Th1 Responses and Attenuates Ragweed-Induced Th2-Type Airway Inflammation in Mice

Urbanization with reduced microbial exposure is associated with an increased burden of asthma and atopic symptoms. Conversely, environmental exposure to endotoxins in childhood can protect against the development of allergies. Our study aimed to investigate whether the renaturation of the indoor environment with aerosolized radiation-detoxified lipopolysaccharide (RD-LPS) has a preventative effect against the development of ragweed-induced Th2-type airway inflammation. To explore this, cages of six-week-old BALB/c mice were treated daily with aerosolized native LPS (N-LPS) or RD-LPS. After a 10-week treatment period, mice were sensitized and challenged with ragweed pollen extract, and inflammatory cell infiltration into the airways was observed. As dendritic cells (DCs) play a crucial role in the polarization of T-cell responses, in our in vitro experiments, the effects of N-LPS and RD-LPS were compared on human monocyte-derived DCs (moDCs). Mice in RD-LPS-rich milieu developed significantly less allergic airway inflammation than mice in N-LPS-rich or common environments. The results of our in vitro experiments demonstrate that RD-LPS-exposed moDCs have a higher Th1-polarizing capacity than moDCs exposed to N-LPS. Consequently, we suppose that the aerosolized, non-toxic RD-LPS applied in early life for the renaturation of urban indoors may be suitable for the prevention of Th2-mediated allergies in childhood.

Patterns of Early-Life Gut Microbial Colonization during Human Immune Development: An Ecological Perspective

Alterations in gut microbial colonization during early life have been reported in infants that later developed asthma, allergies, type 1 diabetes, as well as in inflammatory bowel disease patients, previous to disease flares. Mechanistic studies in animal models have established that microbial alterations influence disease pathogenesis via changes in immune system maturation. Strong evidence points to the presence of a window of opportunity in early life, during which changes in gut microbial colonization can result in immune dysregulation that predisposes susceptible hosts to disease. Although the ecological patterns of microbial succession in the first year of life have been partly defined in specific human cohorts, the taxonomic and functional features, and diversity thresholds that characterize these microbial alterations are, for the most part, unknown. In this review, we summarize the most important links between the temporal mosaics of gut microbial colonization and the age-dependent immune functions that rely on them. We also highlight the importance of applying ecology theory to design studies that explore the interactions between this complex ecosystem and the host immune system. Focusing research efforts on understanding the importance of temporally structured patterns of diversity, keystone groups, and inter-kingdom microbial interactions for ecosystem functions has great potential to enable the development of biologically sound interventions aimed at maintaining and/or improving immune system development and preventing disease.

The infant gut bacterial microbiota and risk of pediatric asthma and allergic diseases

Among the many areas being revolutionized by the recent introduction of culture-independent microbial identification techniques is investigation of the relationship between close contact with large animals, antibiotics, breast feeding, mode of birth, and other exposures during infancy as related to a reduced risk of asthma and allergic disease. These exposures were originally clustered under the "Hygiene Hypothesis" which has evolved into the "Microbiota Hypothesis". This review begins by summarizing epidemiologic studies suggesting that the common feature of these allergy risk-related exposures is their influence on the founding and early development of a child's gut microbiota. Next, studies using culture-independent techniques are presented showing that children who have experienced the exposures of interest have altered gut microbiota. Finally, selected mouse and human studies are presented which begin to corroborate the protective exposures identified in epidemiologic studies by elucidating mechanisms through which microbes can alter immune development and function. These microbially driven immune alterations demonstrate that microbial exposures in many cases could alter the risk of subsequent allergic disease and asthma. Hopefully, a better understanding of how microbes influence allergic disease will lead to safe and effective methods for reducing the prevalence of all forms of allergic disease.

IgE serum concentration against airborne fungi in children with respiratory allergies

Background

To evaluate total and specific E immunoglobulin (IgE) antibody concentrations in underage subjects with respiratory allergic diseases.

Methods

This study was a transversal-type study in 100 underage subjects between 4 and 14 years old, with asthma and/or allergic rhinitis. Total and specific IgE were quantified for airborne fungi in the city of São Luís, Maranhão, Brazil. Five distinct regions—North, South, Center, East and West—were selected so fungi could be collected monthly for 1 year. Twenty genera were identified. Aspergillus, Penicillium, Fusarium and Neurospora were selected for the preparation of sensitizing antigens from ELISA dishes. IgE total concentrations were estimated using the same method.

Results

IgE total serum concentration was increased in 97 % of the atopic subjects: 75 % of the subjects presented increased IgE anti-Aspergillus concentrations, 87 % presented IgE anti-Penicillium, 45 % presented IgE anti-Fusarium, and 46 % presented IgE anti-Neurospora.

Conclusions

Atopic subjects presented simultaneous IgE total and specific elevations for the tested fungi, possibly due to polysensitization caused by the presence of fungi in all of the areas all year. However, determining the clinical significance of the results was not yet possible because most of the data were isolated variables.

Novel, Alternative, and Controversial Therapies of Rhinitis

Rhinitis is a multifactorial disease characterized by sneezing, rhinorrhea, postnasal drip, and nasal congestion. This condition affects 10% to 40% of the population and is responsible for billions of spent health care dollars and impairment in quality of life for those affected. Currently available medical and vaccine therapies are effective for a large segment of this population; however, a subset of patients still has difficult-to-control rhinitis. This article reviews the current progress being made in novel drug and vaccine development and delves into alternative medical, surgical, and homeopathic strategies that may be promising adjunctive treatments for the difficult-to-treat rhinitis patient.

Discovery of 6-Amino-2-{[(1S)-1-methylbutyl]oxy}-9-[5-(1-piperidinyl)pentyl]-7,9-dihydro-8H-purin-8-one (GSK2245035), a Highly Potent and Selective Intranasal Toll-Like Receptor 7 Agonist for the Treatment of Asthma

Induction of IFNα in the upper airways via activation of TLR7 represents a novel immunomodulatory approach to the treatment of allergic asthma. Exploration of 8-oxoadenine derivatives bearing saturated oxygen or nitrogen heterocycles in the N-9 substituent has revealed a remarkable selective enhancement in IFNα inducing potency in the nitrogen series. Further potency enhancement was achieved with the novel (S)-pentyloxy substitution at C-2 leading to the selection of GSK2245035 (32) as an intranasal development candidate. In human cell cultures, compound 32 resulted in suppression of Th2 cytokine responses to allergens, while in vivo intranasal administration at very low doses led to local upregulation of TLR7-mediated cytokines (IP-10). Target engagement was confirmed in humans following single intranasal doses of 32 of ≥20 ng, and reproducible pharmacological response was demonstrated following repeat intranasal dosing at weekly intervals.

Early clinical evaluation of the intranasal TLR7 agonist GSK2245035: Use of translational biomarkers to guide dosing and confirm target engagement

Modulation of the airways' immune milieu is a key therapeutic goal for remission from respiratory allergies. To explore this hypothesis, GSK2245035, a selective Toll-like receptor 7 (TLR7) agonist with preferential Type-1 interferon (IFN)-stimulating properties, was developed for intranasal application. Doses for clinical assessment were extrapolated from translational biomarker studies in primates. Randomized, double-blind, placebo-controlled trials in healthy volunteers and patients with allergic rhinitis demonstrated that intranasal GSK2245035 doses <100 ng were tolerated and did not cause nasal inflammation. Higher doses were not tested due to considerable cytokine release syndrome-related symptoms observed at 100 ng. Clear target engagement, reflected by local and peripheral increase of IFN-gamma-inducible protein-10, was observed at 20 ng, indicating IFN-stimulated immune changes at tolerated doses. Repeat intranasal administration at weekly intervals did not tolerize or amplify the pharmacological response. Intranasal GSK2245035 has an acceptable safety profile at doses that induce local TLR7-mediated immune responses.

Inhaled house dust programs pulmonary dendritic cells to promote type 2 T-cell responses by an indirect mechanism

The induction of allergen-specific T helper 2 (Th2) cells by lung dendritic cells (DCs) is a critical step in allergic asthma development. Airway delivery of purified allergens or microbial products can promote Th2 priming by lung DCs, but how environmentally relevant quantities and combinations of these factors affect lung DC function is unclear. Here, we investigated the ability of house dust extract (HDE), which contains a mixture of environmental adjuvants, to prime Th2 responses against an innocuous inhaled antigen. Inhalational exposure to HDE conditioned lung conventional DCs, but not monocyte-derived DCs, to induce antigen-specific Th2 differentiation. Conditioning of DCs by HDE was independent of Toll-like receptor 4 signaling, indicating that environmental endotoxin is dispensable for programming DCs to induce Th2 responses. DCs directly treated with HDE underwent maturation but were poor stimulators of Th2 differentiation. In contrast, DCs treated with bronchoalveolar lavage fluid (BALF) from HDE-exposed mice induced robust Th2 differentiation. DC conditioning by BALF was independent of the proallergic cytokines IL-25, IL-33, and thymic stromal lymphopoietin. BALF treatment of DCs resulted in upregulation of CD80 but low expression of CD40, CD86, and IL-12p40, which was associated with Th2 induction. These findings support a model whereby environmental adjuvants in house dust indirectly program DCs to prime Th2 responses by triggering the release of endogenous soluble factor(s) by airway cells. Identifying these factors could lead to novel therapeutic targets for allergic asthma.

Glucocorticoid-induced leucine zipper is downregulated in human alveolar macrophages upon Toll-like receptor activation

Induction of the glucocorticoid-induced leucine zipper (GILZ) by glucocorticoids plays a role in their antiinflammatory action, whereas GILZ expression is reduced under inflammatory conditions. The mechanisms regulating GILZ expression during inflammation, however, have not yet been characterized. Here, we investigated GILZ expression in human alveolar macrophages (AMs) following Toll-like receptor (TLR) activation. Macrophages were shown to predominantly express GILZ transcript variant 2. Lipopolysaccharide-treated AMs, THP-1 cells, and lungs of lipopolysaccharide-exposed mice displayed decreased GILZ protein and mRNA levels. The effect was strictly dependent on the adapter molecule MyD88, as shown by using specific ligands or a knockdown strategy. Investigations on the functional significance of GILZ downregulation performed by GILZ knockdown revealed a proinflammatory response, as indicated by increased cytokine expression and NF-κB activity. We found that TLR activation reduced GILZ mRNA stability, which was mediated via the GILZ 3'-untranslated region. Finally, involvement of the mRNA-binding protein tristetraprolin (TTP) is suggested, since TTP overexpression or knockdown modulated GILZ expression and TTP was induced in a MyD88-dependent fashion. Taken together, our data show a MyD88- and TTP-dependent GILZ downreg-ulation in human macrophages upon TLR activation. Suppression of GILZ is mediated by mRNA destabilization, which might represent a regulatory mechanism in macrophage activation.

TLR4 and TLR9 Expression in Different Phenotypes of Rhinitis

Background. Toll-like receptors (TLRs) represent a family of evolutionarily conserved proteins, that represent a fundamental link between innate and adaptive immune responses. Aim. The purpose of this study was to investigate the expression of TLR4 and TLR9 in the normal nasal mucosa and in the mucosa of subjects with different phenotypes of rhinitis. Methodology. A confocal analysis of TLR4 and TLR9 (co)expression was carried out on biopsies from the inferior turbinate obtained from 4 patients affected by persistent allergic rhinitis, 8 patients with chronic rhino-sinusitis, and 6 patients with vasomotor rhinitis The results were compared with those of specimens obtained from 4 subjects undergoing nasal surgery, but with signs of nasal inflammation. Results. TLR4 and TLR9 were expressed in the healthy nasal mucosa; TLR4 and TLR9 expression was significantly decreased in allergic rhinitis. TLR4 was over expressed in the epithelium of chronic rhino-sinusitis. Both TLRs were co-expressed in the sub-epithelial infiltrate of chronic and vasomotor rhinitis, even though this expression was higher in the former compared with the latter. Conclusions. This study indicates that TLR4 and TLR9 show a different pattern of expression in different phenotypes of rhinitis, possibly related to the type and severity of the disease.

Pulmonary endotoxin tolerance protects against cockroach allergen-induced asthma-like inflammation in a mouse model

BACKGROUND

Compounds which activate the innate immune system, such as lipopolysaccharide, are significant components of ambient air, and extremely difficult to remove from the environment. It is currently unclear how prior inhalation of endotoxin affects allergen sensitization. We examined whether lung-specific endotoxin tolerance induction prior to sensitization can modulate the response to allergen.

METHODS

Endotoxin tolerance was induced by repeated intratracheal exposure to endotoxin. All mice were then sensitized and challenged by direct intratracheal instillation of cockroach allergen.

RESULTS

After allergen sensitization and challenge, endotoxin tolerant mice had significantly decreased airways hyperresponsiveness to methacholine challenge, which was confirmed by invasive lung function tests. Decreased goblet cell hyperplasia and mucus production were also found by histological assessment. Tolerant mice were protected from airway eosinophilia through the mechanism of reduced CCL11 and CCL24. Interestingly, endotoxin tolerant mice had only a modest reduction in cockroach-specific IgE; however, total IgE was significantly reduced.

CONCLUSIONS

These data show that induction of endotoxin tolerance prior to sensitization protects against the hallmark features of asthma-like inflammation, and that transient modulation of innate immunity can have long-lasting effects on adaptive responses.

A systematic review and meta-analysis of the effects of pasteurization on milk vitamins, and evidence for raw milk consumption and other health-related outcomes

Pasteurization of milk ensures safety for human consumption by reducing the number of viable pathogenic bacteria. Although the public health benefits of pasteurization are well established, pro-raw milk advocate organizations continue to promote raw milk as "nature's perfect food." Advocacy groups' claims include statements that pasteurization destroys important vitamins and that raw milk consumption can prevent and treat allergies, cancer, and lactose intolerance. A systematic review and meta-analysis was completed to summarize available evidence for these selected claims. Forty studies assessing the effects of pasteurization on vitamin levels were found. Qualitatively, vitamins B12 and E decreased following pasteurization, and vitamin A increased. Random effects meta-analysis revealed no significant effect of pasteurization on vitamin B6 concentrations (standardized mean difference [SMD], -2.66; 95% confidence interval [CI], -5.40, 0.8; P = 0.06) but a decrease in concentrations of vitamins B1 (SMD, -1.77; 95% CI, -2.57, -0.96; P < 0.001), B2 (SMD, -0.41; 95% CI, -0.81, -0.01; P < 0.05), C (SMD, -2.13; 95% CI, -3.52, -0.74; P < 0.01), and folate (SMD, -11.99; 95% CI, -20.95, -3.03; P < 0.01). The effect of pasteurization on milk's nutritive value was minimal because many of these vitamins are naturally found in relatively low levels. However, milk is an important dietary source of vitamin B2, and the impact of heat treatment should be further considered. Raw milk consumption may have a protective association with allergy development (six studies), although this relationship may be potentially confounded by other farming-related factors. Raw milk consumption was not associated with cancer (two studies) or lactose intolerance (one study). Overall, these findings should be interpreted with caution given the poor quality of reported methodology in many of the included studies.

Reducing LPS content in cockroach allergens increases pulmonary cytokine production without increasing inflammation: a randomized laboratory study

Background

Endotoxins are ubiquitously present in the environment and constitute a significant component of ambient air. These substances have been shown to modulate the allergic response, however a consensus has yet to be reached whether they attenuate or exacerbate asthmatic responses. The current investigation examined whether reducing the concentration of lipopolysaccharide (LPS) in a house dust extract (HDE) containing high concentrations of both cockroach allergens [1] and LPS would attenuate asthma-like pulmonary inflammation.

Methods

Mice were sensitized with CRA and challenged with the intact HDE, containing 182 ng of LPS, or an LPS-reduced HDE containing 3 ng LPS, but an equivalent amount of CRA. Multiple parameters of asthma-like pulmonary inflammation were measured.

Results

Compared to HDE challenged mice, the LPS-reduced HDE challenged mice had significantly reduced TNFα levels in the bronchoalveolar lavage fluid. Plasma levels of IgE and IgG1 were significantly reduced, however no change in CRA-specific IgE was detected. In HDE mice, plasma IgG2a levels were similar to naïve mice, while LPS-reduced HDE mice had significantly greater concentrations. Reduced levels of LPS in the HDE did not decrease eosinophil or neutrophil recruitment into the alveolar space. Equivalent inflammatory cell recruitment occurred despite having generally higher pulmonary concentrations of eotaxins and CXC chemokines in the LPS-reduced HDE group. LPS-reduced HDE challenge induced significantly higher concentrations of IFNγ, and IL-5 and IL-13 in the BAL fluid, but did not decrease airways hyperresponsiveness or airway resistance to methacholine challenge. Conclusion: These data show that reduction of LPS levels in the HDE does not significantly protect against the severity of asthma-like pulmonary inflammation.

Dangerous allergens: why some allergens are bad actors

Immune responses can be compartmentalized into innate versus adaptive components. This relatively recent dichotomy positioned the innate immune system at the interface between the host and the external environment and provided a new conceptual framework with which to view allergic diseases, including asthma. Airway epithelial cells and dendritic cells are key components of the innate immune system in the nose and lung and are now known to be intimately involved in allergen recognition and in modulating allergic immune responses. Here we review current thinking about how these two key cell types sense and respond to inhaled allergens, and emphasize how an understanding of "allergic innate immunity" can translate into new thinking about mechanisms of allergen sensitization and potentially lead to new therapeutic targets.

Dangerous allergens: innate immunity, dendritic cells and allergic asthma

Immune responses can be compartmentalized into innate versus adaptive components. This relatively recent dichotomy positioned the innate immune system at the interface between the host and the external environment, and provided a new conceptual framework with which to view allergic diseases, including asthma. Among the cells of the innate immune system, antigen-presenting dendritic cells are now thought to be intimately involved in allergen recognition, as well as modulating allergic immune responses. This review summarizes current thinking regarding the role of dendritic cells in allergic asthma and concludes with a summary of emerging concepts in the field.

Epidemiology of asthma: risk factors for development

This comprehensive review of the recent literature was undertaken to determine the current state of knowledge of the risk factors involved in the development of asthma in order to focus investigations in a proposed new longitudinal birth cohort study. The origins of asthma appear to lie in the prenatal and early postnatal period, and renewed investigations in this period with long-term close follow-up and objective phenotypic characterization will help to unravel the role of the multiple putative environmental factors in the development of asthma. It is only after understanding these effects that one can hope to design rational prevention studies for asthma.

Regulatory T cells contribute to allergen tolerance induced by daily airway immunostimulant exposures

Endotoxin and other immunostimulants ubiquitous in ambient air are potent mucosal adjuvants, yet only a minority of individuals develop aeroallergen hypersensitivities, whereas the majority develop tolerance. These investigations were performed to reconcile this paradox. During initial experiments, mice received a primary series of weekly intranasal OVA immunizations (1(0) vaccination). Selected mice also received intranasal sterile house dust extract (HDE) with each OVA vaccination, at a dose previously found to exert adjuvant activity. A third group of OVA-vaccinated mice received intranasal HDE on a daily basis, but at one seventh the adjuvant dose, beginning 1 week before the first and ending with the last 1(0) OVA vaccination. Mice were then left untreated for 4 weeks, and then received a secondary series of weekly intranasal OVA immunizations with adjuvant doses of HDE (2(0) sensitization). Three weeks later, OVA-specific airway challenges and immune responses were assessed. Analogous experiments were conducted with LPS. Mice receiving daily intranasal HDE or LPS during 1(0) OVA vaccination were highly resistant to 2(0) sensitization, whereas the mice in other experimental groups readily developed Th2-biased airway hypersensitivity. Tolerance was associated with poor OVA-specific CD4 cell proliferation and with local natural T-regulatory cell (Treg) expansion. Finally, Treg depletion by delivery of the anti-CD25 monoclonal antibody during 1(0) vaccination attenuated the tolerogenic effects of daily airway HDE exposures. These studies suggest that regular airway immunostimulant exposures selectively increase local Treg numbers and activity in an antigen-independent manner, thereby promoting the development of aeroallergen tolerance.

Regulation of aeroallergen immunity by the innate immune system: laboratory evidence for a new paradigm

Over the last decade, it has become increasingly clear that innate responses to microbes are mediated largely by toll-like receptors (TLRs), which recognize a diverse family of molecules produced by viruses, bacteria and fungi. This article will present evidence that TLRs also play a dominant role in innate responses to non-infectious immunostimulatory materials present in house dust extracts (HDEs) and the living environments they represent. However, our investigations challenge the commonly held view that microbial products in ambient air protect against the allergic march by promoting protective Th1 biased responses to inspired aeroallergens. Instead, all HDEs studied to date have preferentially promoted the development of Th2 biased airway hypersensitivities when used as adjuvants for intranasal (i.n.) vaccination. In contrast, daily low dose i.n. HDE delivery was found to promote the development of aeroallergen tolerance. This article will review these experimental findings as evidence to propose a new paradigm by which airborne TLR ligands and other stimulants of innate immunity may influence aeroallergen specific immunity and the genesis of allergic respiratory diseases.

Determinants of allergenicity

The question "What makes an allergen an allergen?" has puzzled generations of researchers, and we still do not have a conclusive answer. Despite increasing knowledge about the molecular and functional characteristics of allergens that have been identified, we still do not fully understand why some proteins are clinically relevant allergens and most are not. Different approaches have been taken to identify the structural and functional features of allergens, aiming at developing methods to predict allergenicity and thus to identify allergens. However, none of these methods has allowed a reliable discrimination between allergenic and nonallergenic compounds on its own. This review sums up diverse determinants that contribute to the phenomenon of allergenicity and outlines that in addition to the structure and function of the allergen, factors derived from allergen carriers, the environment, and the susceptible individual are of importance.

Allergen tolerance versus the allergic march: the hygiene hypothesis revisited

In addition to genetics, several environmental variables appear to impact allergic risk. Meta-analyses of epidemiologic studies presented in this article demonstrate a correlation between specific ambient exposures (eg, livestock, pets, endotoxin, and unpasteurized milk ingestion) and reduced allergic risk during childhood. Additional laboratory investigations discussed in this review characterized the intrinsic immunostimulatory activities of living environments. Considered together, results of these investigations suggest a novel paradigm by which early-life home exposures to microbial products and other allergen-nonspecific immunostimulants modify allergic risk.

Airway house dust extract exposures modify allergen-induced airway hypersensitivity responses by TLR4-dependent and independent pathways

TLR ligands and other allergen-nonspecific immunostimulatory molecules are ubiquitous in ambient air and have profound modulatory activities in animal models of allergic asthma. However, several of these molecules have been shown to promote exaggerated Th2-biased airway hypersensitivity responses (AHRs), whereas others attenuate the asthmatic phenotype. Therefore, it has proven difficult to extrapolate experimental results with purified molecules toward a more general understanding of the allergen-nonspecific immunomodulatory influence of living environments on the natural history of allergic asthma. These investigations determined how regular and intermittent airway exposures to an unpurified, but sterile house dust extract standard (HDEst) affected the OVA-specific AHR and immune status of previously Th2-sensitized mice. Low-dose daily and high-dose intermittent HDEst exposures modulated ongoing AHRs considerably, reducing eosinophil recruitment and methacholine responsiveness, while increasing neutrophilic inflammation. However, only daily airway delivery of low-dose HDEst attenuated OVA-specific Th2 cytokine production and Th2-biased AHRs to allergen challenge 1 mo later. Finally, whereas LPS mimicked many of the immunomodulatory characteristics of HDEst in this murine asthma model, daily airway HDEst delivery was highly effective in attenuating the AHR of OVA/alum-sensitized TLR4-deficient mice. Taken together, these investigations provide direct evidence that living environments contain allergen-nonspecific immunostimulatory molecules that influence the airway hypersensitivity status of allergen-sensitized mice by TLR4-dependent and independent mechanisms.

Primary prevention of allergic diseases: current concepts and mechanisms

: Atopic diseases, the new "epidemic of the twenty-first century" and a central health problem of industrial nations, call for the development of innovative primary prevention strategies. The present review provides an overview of current experimental and immunomodulatory procedures and their underlying mechanisms.

Update on toll-like receptor-directed therapies for human disease

Innate responses to microbes are mediated in large part by toll-like receptors (TLRs), which recognise a diverse range of molecules produced by viruses, bacteria and fungi. Great effort has been directed towards translating this knowledge into the development of new therapies for a wide spectrum of diseases, including infectious, malignant, autoimmune and allergic diseases. This review will provide a brief update on completed, ongoing and planned clinical trials of TLR ligand-based therapies for the treatment of diseases in humans.

Defining a role for ambient TLR ligand exposures in the genesis and prevention of allergic diseases

Environmental variables responsible for the increasing allergic disease burden observed in developed countries over the last century have yet to be adequately characterized. Meta-analyses of epidemiological studies presented in the first half of this paper demonstrate a correlation between farm-associated exposures (i.e., livestock, pets, unpasteurized milk, and endotoxin) and a reduction in allergic risk during childhood. Laboratory investigations discussed in the second half of the paper characterize the intrinsic immunostimulatory activities of living environments. Considered together, experimental findings presented herein suggest a novel paradigm by which early life home exposures to microbial products and other allergen-nonspecific immunostimulants modify allergic risk.

Advances in basic and clinical immunology in 2006

This article reviews the progress in the field of basic and clinical immunology in 2006, focusing on the articles published in the Journal. The role of Toll-like receptors in the immune response was explored in detail in several articles. The knowledge gained in these investigations is being used to develop strategies that enhance the immunogenicity of vaccines to prevent infectious diseases and to have an immunomodulatory effect on allergic diseases. Other components of the innate immunity reported on were the recognition of allergens with lipid-derived motifs by CD1d-restricted T cells and the role of dendritic cells in the development of an allergic response. More than 120 primary immunodeficiencies were defined at a molecular level, and biological agents such as TNF-alpha antagonists and IFN-alpha were shown to have therapeutic use. New anti-HIV drugs that block cell entry were proven to be effective, thus offering alternative therapies to respond to the development of multidrug-resistant HIV strains. The modern understanding of immunologic concepts is helping to elucidate the mechanisms of defense against viruses, bacteria, and parasites; as a result, strategies to improve management and prevention continue to emerge.

Advances in environmental and occupational disorders 2006

In 2006, there continued to be significant contributions to the Journal in the area of environmental and occupational allergy. In addition to very strong clinical observations, there were a number of studies that examined the effect of environmental agents on cellular and molecular processes in allergy, and molecular approaches were also used in investigations of allergen structure and biology. The Journal also received a number of very strong epidemiologic studies examining several aspects of environmental and occupational allergy. Thus, this particular area of our specialty thrives as a result of clinical, mechanistic, epidemiologic, and translational observations. This article reviews a number of these papers presented in the Journal in 2006.