Regulation of immunological homeostasis in the respiratory tract

Particles internalization, oxidative stress, apoptosis and pro-inflammatory cytokines in alveolar macrophages exposed to cement dust

Exposure to cement dust is one of the most common occupational dust exposures worldwide, but the mechanism of toxicity has not been fully elucidated. Cement dust (N) and clinker (C) samples collected from Nigeria and another sample of cement dust (U) collected from USA were evaluated using alveolar macrophage (NR8383) cell culture to determine the contribution of different sources of cement dust in the severity of cement dust toxicity. Cement dust particles internalization and morphologic alterations using transmission electron microscopy (TEM), cytotoxicity, apoptotic cells induction, intracellular reactive oxygen species generation, glutathione reduction, TNF-α, IL-1β, and CINC-3 secretion in alveolar macrophages (NR8383) exposed to cement dust and clinker samples were determined. Particles were internalized into the cytoplasmic vacuoles, with cells exposed to U showing increased cell membrane blebbing. Also, NR8383 exposed to U show more significant ROS generation, apoptotic cells induction and decreased glutathione. Interleukin-1β and TNF-α secretion were significantly more in cells exposed to both cement dust samples compared with clinker, while CINC-3 secretion was significantly more in cells exposed to clinker (p < 0.05). Endocytosis, oxidative stress induced-apoptosis and induction of pro-inflammatory cytokines may be key mechanisms of cement dust immunotoxicity in the lung and toxicity may be factory dependent.

Transient ablation of alveolar macrophages leads to massive pathology of influenza infection without affecting cellular adaptive immunity

Alveolar macrophages (AMs), localized at the pulmonary air-tissue interface, are one of the first lines of defense that interact with inhaled airborne pathogens such as influenza viruses. By using a new CD169-DTR transgenic mouse strain we demonstrate that specific and highly controlled in vivo ablation of this myeloid cell subset leads to severe impairment of the innate, but not adaptive, immune responses and critically affects the progression of the disease. In fact, AM-ablated mice, infected with a normally sublethal dose of PR8 influenza virus, showed dramatically increased virus load in the lungs, severe airway inflammation, pulmonary edema and vascular leakage, which caused the death of the infected animals. Our data highlight the possibilities for new therapeutic strategies focusing on modulation of AMs, which may efficiently boost innate responses to influenza infections.

Defective respiratory tract immune surveillance in asthma: a primary causal factor in disease onset and progression

The relative importance of respiratory viral infections vs inhalant allergy in asthma pathogenesis is the subject of ongoing debate. Emerging data from long-term prospective birth cohorts are bringing increasing clarity to this issue, in particular through the demonstration that while both of these factors can contribute independently to asthma initiation and progression, their effects are strongest when they act in synergy to drive cycles of episodic airways inflammation. An important question is whether susceptibility to infection and allergic sensitization in children with asthma arises from common or shared defect(s). We argue here that susceptibility to recurrent respiratory viral infections, failure to generate protective immunologic tolerance to aeroallergens, and ultimately the synergistic interactions between inflammatory pathways triggered by concomitant responses to these agents all result primarily from functional deficiencies within the cells responsible for local surveillance for antigens impinging on airway surfaces: the respiratory mucosal dendritic cell (DC) network. The effects of these defects in DCs from children wtih asthma are accentuated by parallel attenuation of innate immune functions in adjacent airway epithelial cells that reduce their resistance to the upper respiratory viral infections, which are the harbingers of subsequent inflammatory events at asthma lesion site(s) in the lower airways. An important common factor underpinning the innate immune functions of these unrelated cell types is use of an overlapping series of pattern recognition receptors (exemplified by the Toll-like receptor family), and variations in the highly polymorphic genes encoding these receptors and related molecules in downstream signaling pathways appear likely contributors to these shared defects. Findings implicating recurrent respiratory infections in adult-onset asthma, much of which is nonatopic, suggest a similar role for deficient immune surveillance in this phenotype of the disease.

Promotion of lung health: NHLBI Workshop on the Primary Prevention of Chronic Lung Diseases

Lung-related research primarily focuses on the etiology and management of diseases. In recent years, interest in primary prevention has grown. However, primary prevention also includes "health promotion" (actions in a population that keep an individual healthy). We encourage more research on population-based (public health) strategies that could not only maximize lung health but also mitigate "normal" age-related declines-not only for spirometry but across multiple measures of lung health. In developing a successful strategy, a "life course" approach is important. Unfortunately, we are unable to achieve the full benefit of this approach until we have better measures of lung health and an improved understanding of the normal trajectory, both over an individual's life span and possibly across generations. We discuss key questions in lung health promotion, with an emphasis on the upper (healthier) end of the distribution of lung functioning and resiliency and briefly summarize the few interventions that have been studied to date. We conclude with suggestions regarding the most promising future research for this important, but largely neglected, area of lung research.

Progress in tuberculosis vaccine development and host-directed therapies--a state of the art review

Tuberculosis continues to kill 1·4 million people annually. During the past 5 years, an alarming increase in the number of patients with multidrug-resistant tuberculosis and extensively drug-resistant tuberculosis has been noted, particularly in eastern Europe, Asia, and southern Africa. Treatment outcomes with available treatment regimens for drug-resistant tuberculosis are poor. Although substantial progress in drug development for tuberculosis has been made, scientific progress towards development of interventions for prevention and improvement of drug treatment outcomes have lagged behind. Innovative interventions are therefore needed to combat the growing pandemic of multidrug-resistant and extensively drug-resistant tuberculosis. Novel adjunct treatments are needed to accomplish improved cure rates for multidrug-resistant and extensively drug-resistant tuberculosis. A novel, safe, widely applicable, and more effective vaccine against tuberculosis is also desperately sought to achieve disease control. The quest to develop a universally protective vaccine for tuberculosis continues. So far, research and development of tuberculosis vaccines has resulted in almost 20 candidates at different stages of the clinical trial pipeline. Host-directed therapies are now being developed to refocus the anti-Mycobacterium tuberculosis-directed immune responses towards the host; a strategy that could be especially beneficial for patients with multidrug-resistant tuberculosis or extensively drug-resistant tuberculosis. As we are running short of canonical tuberculosis drugs, more attention should be given to host-directed preventive and therapeutic intervention measures.

TLR Agonists as Modulators of the Innate Immune Response and Their Potential as Agents Against Infectious Disease

Immunotherapies that can either activate or suppress innate immune responses are being investigated as treatments against infectious diseases and the pathology they can cause. The objective of these therapies is to elicit protective immune responses thereby limiting the harm inflicted by the pathogen. The Toll-like receptor (TLR) signaling pathway plays critical roles in numerous host immune defenses and has been identified as an immunotherapeutic target against the consequences of infectious challenge. This review focuses on some of the recent advances being made in the development of TLR-ligands as potential prophylactic and/or therapeutic agents.

Airway epithelial regulation of pulmonary immune homeostasis and inflammation

Recent genetic, structural and functional studies have identified the airway and lung epithelium as a key orchestrator of the immune response. Further, there is now strong evidence that epithelium dysfunction is involved in the development of inflammatory disorders of the lung. Here we review the characteristic immune responses that are orchestrated by the epithelium in response to diverse triggers such as pollutants, cigarette smoke, bacterial peptides, and viruses. We focus in part on the role of epithelium-derived interleukin (IL)-25, IL-33 and thymic stromal lymphopoietin (TSLP), as well as CC family chemokines as critical regulators of the immune response. We cite examples of the function of the epithelium in host defense and the role of epithelium dysfunction in the development of inflammatory diseases.

CD11c⁺ cells primed with unrelated antigens facilitate an accelerated immune response to influenza virus in mice

Recent evidence suggests that an individual's unique history and sequence of exposures to pathogens and antigens may dictate downstream immune responses to disparate antigens. We show that the i.n. delivery of nonreplicative virus-like particles (VLPs), which bear structural but no antigenic similarities to respiratory pathogens, acts to prime the lungs of both C56BL/6 and BALB/c mice, facilitating heightened and accelerated primary immune responses to high-dose influenza challenge, thus providing a nonpathogenic model of innate imprinting. These responses correspond closely to those observed following natural infection with the opportunistic fungus, Pneumocystis murina, and are characterized by accelerated antigen processing by DCs and alveolar macrophages, an enhanced influx of cells to the local tracheobronchial lymph node, and early upregulation of T-cell co-stimulatory/adhesion molecules. CD11c⁺ cells, which have been directly exposed to VLPs or Pneumocystis are necessary in facilitating enhanced clearance of influenza virus, and the repopulation of the lung by Ly-6C⁺ precursors relies on CCR2 expression. Thus, immune imprinting 72 h after VLP-priming, or 2 weeks after Pneumocystis-priming is CCR2-mediated and results from the enhanced antigen processing, maturation, and trafficking abilities of DCs and alveolar macrophages, which cause accelerated influenza-specific primary immune responses and result in superior viral clearance.

Two-photon intravital imaging of lungs during anthrax infection reveals long-lasting macrophage-dendritic cell contacts

The dynamics of the lung immune system at the microscopic level are largely unknown because of inefficient methods of restraining chest motion during image acquisition. In this study, we developed an improved intravital method for two-photon lung imaging uniquely based on a posteriori parenchymal tissue motion correction. We took advantage of the alveolar collagen pattern given by the second harmonic generation signal as a reference for frame registration. We describe here for the first time a detailed dynamic account of two major lung immune cell populations, alveolar macrophages and CD11b-positive dendritic cells, during homeostasis and infection by spores of Bacillus anthracis, the agent of anthrax. We show that after alveolar macrophages capture spores, CD11b-positive dendritic cells come in prolonged contact with infected macrophages. Dendritic cells are known to carry spores to the draining lymph nodes and elicit the immune response in pulmonary anthrax. The intimate and long-lasting contacts between these two lines of defense may therefore coordinate immune responses in the lung through an immunological synapse-like process.

Role of major histocompatibility complex class II expression by non-hematopoietic cells in autoimmune and inflammatory disorders: facts and fiction

It is well established that interactions between CD4(+) T cells and major histocompatibility complex class II (MHCII) positive antigen-presenting cells (APCs) of hematopoietic origin play key roles in both the maintenance of tolerance and the initiation and development of autoimmune and inflammatory disorders. In sharp contrast, despite nearly three decades of intensive research, the functional relevance of MHCII expression by non-hematopoietic tissue-resident cells has remained obscure. The widespread assumption that MHCII expression by non-hematopoietic APCs has an impact on autoimmune and inflammatory diseases has in most instances neither been confirmed nor excluded by indisputable in vivo data. Here we review and put into perspective conflicting in vitro and in vivo results on the putative impact of MHCII expression by non-hematopoietic APCs--in both target organs and secondary lymphoid tissues--on the initiation and development of representative autoimmune and inflammatory disorders. Emphasis will be placed on the lacunar status of our knowledge in this field. We also discuss new mouse models--developed on the basis of our understanding of the molecular mechanisms that regulate MHCII expression--that constitute valuable tools for filling the severe gaps in our knowledge on the functions of non-hematopoietic APCs in inflammatory conditions.

Tidal volume drives inflammation during mechanical ventilation for viral respiratory infection

OBJECTIVE

Respiratory syncytial virus lower respiratory tract infection is the most frequent cause of respiratory insufficiency necessitating mechanical ventilation in infants during the winter season. Recently, we presented a new animal model to show that mechanical ventilation aggravates respiratory syncytial virus-induced pulmonary inflammation by distinct mechanisms. We now use this model to study whether low tidal volume mechanical ventilation causes less ventilator-induced lung injury in the presence of respiratory syncytial virus lower respiratory tract infection.

DESIGN

Randomized controlled experimental study.

SETTING

University Medical Center animal laboratory.

SUBJECTS

Male BALB/c mice, 6-8 weeks old and weighing 20-28 g.

INTERVENTIONS

Mice were inoculated with respiratory syncytial virus or mock virus on day 0 and ventilated on day 1 or 5 with high (12 mL/kg) or low (6 mL/kg) tidal volume for 5 hours.

MEASUREMENTS AND MAIN RESULTS

Total and differential cell counts as well as cytokine concentrations were determined in bronchoalveolar lavage fluid. Compared with nonventilated respiratory syncytial virus-infected mice, high tidal volume ventilation of respiratory syncytial virus-infected mice on day 5 enhanced bronchoalveolar lavage fluid total cell count (0.35 vs 0.99 × 10e6/mL; p < 0.01), neutrophils (0.02 vs 0.17 × 10e6/mL; p < 0.01), interleukin-6 (58 vs 250 pg/mL; p < 0.01), and keratinocyte-derived chemokine (95 vs 335 pg/mL; p < 0.01) levels. In low tidal volume ventilation of respiratory syncytial virus-infected mice, no significant difference in cell counts or cytokine concentrations was observed compared with spontaneous breathing respiratory syncytial virus-infected controls on both days.

CONCLUSIONS

Low tidal volume mechanical ventilation causes less ventilation-induced cellular and cytokine influx into the bronchoalveolar space during respiratory syncytial virus lower respiratory tract infection.

Human tonsil-derived dendritic cells are poor inducers of T cell immunity to mucosally encountered pathogens

The mucosal immune system must initiate and regulate protective immunity, while balancing this immunity with tolerance to harmless antigens and bacterial commensals. We have explored the hypothesis that mucosal dendritic cells (DC) control the balance between regulation and immunity, by studying the responses of human tonsil-derived DC to Neisseria meningitidis as a model organism. We show that tonsil DC are able to sample their antigenic environment, internalizing Nm and expressing high levels of HLA-DR and CD86. However, in comparison to monocyte-derived DC (moDC), they respond to pathogen encounter with only low level cytokine production, largely dominated by TGFβ. Functionally, tonsil DC also only stimulated low levels of antigen-specific T cell proliferation and cytokine production when compared to moDC. We therefore propose that the default role for DC in the nasopharynx is to maintain tolerance/ignorance of the large volume of harmless antigens and bacterial commensals encountered at the nasopharyngeal mucosa.

New vaccines against influenza virus

Vaccination is one of the most effective and cost-benefit interventions that prevent the mortality and reduce morbidity from infectious pathogens. However, the licensed influenza vaccine induces strain-specific immunity and must be updated annually based on predicted strains that will circulate in the upcoming season. Influenza virus still causes significant health problems worldwide due to the low vaccine efficacy from unexpected outbreaks of next epidemic strains or the emergence of pandemic viruses. Current influenza vaccines are based on immunity to the hemagglutinin antigen that is highly variable among different influenza viruses circulating in humans and animals. Several scientific advances have been endeavored to develop universal vaccines that will induce broad protection. Universal vaccines have been focused on regions of viral proteins that are highly conserved across different virus subtypes. The strategies of universal vaccines include the matrix 2 protein, the hemagglutinin HA2 stalk domain, and T cell-based multivalent antigens. Supplemented and/or adjuvanted vaccination in combination with universal target antigenic vaccines would have much promise. This review summarizes encouraging scientific advances in the field with a focus on novel vaccine designs.

Nasal epithelial repair and remodeling in physical injury, infection, and inflammatory diseases

PURPOSE OF REVIEW

To summarize the current knowledge of cellular and molecular mechanisms of nasal epithelial repair and remodeling during physical and pathophysiological conditions.

RECENT FINDINGS

Nasal epithelial repair and remodeling is a highly organized and well coordinated process, involving inflammation, proliferation, differentiation, matrix deposition, and remodeling, and is regulated by a wide variety of growth factors and cytokines. From the in-vivo and in-vitro studies conducted in both human and animal models, undifferentiated basal cells (progenitors) are able to migrate from adjacent epithelium, spread over the denuded basement membrane, and proliferate in injured regions (self-renewal) in necessary (homeostasis) or excessive (hyperplasia) degree. Progenitor cells reorient to an apical-basal polarity, and progressively differentiate into ciliated and nonciliated columnar cells and goblet cells, reconstituting a functional respiratory epithelium after several weeks. This recovery process can be observed during various types and severity of injury, and also in common nasal diseases, including acute viral, allergic, and nonallergic rhinitis, as well as chronic rhinosinusitis with and without nasal polyps.

SUMMARY

Although nearly 10 000 articles about nasal epithelium have been published in the last decade, the mechanisms underlying the nasal epithelial repair are still understood at only a superficial descriptive level. In order to advance rhinology to the next level of a comprehensive knowledge of the orchestrated genetic and molecular processes acting during epithelial repair, combined clinical and experimental studies using sophisticated investigational plans to elucidate the functions of both the protein-coding and regulatory portions of the human genome are required.

NOX2 in lung inflammation: quantum dot based in situ imaging of NOX2-mediated expression of vascular cell adhesion molecule-1

Quantum dot (QD) imaging is a powerful tool for studying signaling pathways as they occur. Here we employ this tool to study adhesion molecule expression with lung inflammation in vivo. A key event in pulmonary inflammation is the regulation of vascular endothelial cell adhesion molecule-1 (VCAM), which drives activated immune cell adherence. The induction of VCAM expression is known to be associated with reactive oxygen species (ROS) production, but the exact mechanism or the cellular source of ROS that regulates VCAM in inflamed lungs is not known. NADPH oxidase 2 (NOX2) has been reported to be a major source of ROS with pulmonary inflammation. NOX2 is expressed by both endothelial and immune cells. Here we use VCAM-targeted QDs in a mouse model to show that NOX2, specifically endothelial NOX2, induces VCAM expression with lung inflammation in vivo.

STP Position Paper

The Scientific and Regulatory Policy Committee of the Society of Toxicologic Pathology (STP) appointed a working group to address risk assessment for increases in alveolar macrophages following inhalation of pharmaceutical materials. This position paper provides recommendations for inhalation study–specific terminology and interpretation based on literature and information from marketed inhaled drugs. Based on a weight-of-the-evidence approach, and with appropriate consideration of the physical and pharmacological characteristics of the compound, uncomplicated increases in the size or number of alveolar macrophages in nonclinical species are interpreted as nonadverse.

Chronic follicular bronchiolitis requires antigen-specific regulatory T cell control to prevent fatal disease progression

To study regulatory T (Treg) cell control of chronic autoimmunity in a lymphoreplete host, we created and characterized a new model of autoimmune lung inflammation that targets the medium and small airways. We generated transgenic mice that express a chimeric membrane protein consisting of hen egg lysozyme and a hemoglobin epitope tag under the control of the Clara cell secretory protein promoter, which largely limited transgene expression to the respiratory bronchioles. When Clara cell secretory protein-membrane hen egg lysozyme/hemoglobin transgenic mice were crossed to N3.L2 TCR transgenic mice that recognize the hemoglobin epitope, the bigenic progeny developed dense, pseudo-follicular lymphocytic peribronchiolar infiltrates that resembled the histological pattern of follicular bronchiolitis. Aggregates of activated IFN-γ- and IL-17A-secreting CD4(+) T cells as well as B cells surrounded the airways. Lung pathology was similar in Ifng(-/-) and Il17a(-/-) mice, indicating that either cytokine is sufficient to establish chronic disease. A large number of Ag-specific Treg cells accumulated in the lesions, and Treg cell depletion in the affected mice led to an interstitial spread of the disease that ultimately proved fatal. Thus, Treg cells act to restrain autoimmune responses, resulting in an organized and controlled chronic pathological process rather than a progressive disease.

Cry1Ac protoxin from Bacillus thuringiensis promotes macrophage activation by upregulating CD80 and CD86 and by inducing IL-6, MCP-1 and TNF-α cytokines

Bacillus thuringiensis Cry1Ac protoxin (pCry1Ac) is a promising mucosal adjuvant, but its action mechanism is unknown. We examined in vivo whether pCry1Ac promotes the activation of macrophages in the peritoneum, spleen and mesenteric lymph nodes or in the lungs and bronchoalveolar lavage after intraperitoneal or intranasal pCry1Ac administration, respectively, in BALB/c mice. pCry1Ac upregulated the costimulatory molecules CD80 and CD86 in these macrophages, but with distinct kinetics. In vitro stimulation of resident macrophages with pCry1Ac upregulated CD80 and CD86 and enhanced the production of the pro-inflammatory cytokines TNF-α, IL-6 and MCP-1. To investigate whether the pCry1Ac-induced activation was mediated through MAPK pathways, we pretreated RAW 264.7 cells with signaling inhibitors of MEK, JNK and p38 MAPKs (PD98059, SP600125 and SB203580, respectively). pCry1Ac-induced upregulation of CD86 and CD80 was partially inhibited by the MEK inhibitor. While LPS-induced upregulation mechanisms of CD80 and CD86 appear to be different; as these were particularly inhibited by MEK and JNK inhibitors, respectively. pCry1Ac-induced IL-6 and MCP-1 production was especially inhibited with the p38 MAPK inhibitor, whereas TNF-α was only slightly inhibited upon treatment with JNK and p38 MAPK inhibitors. Therefore macrophage stimulation with pCry1Ac induced the upregulation of CD80 and CD86, and the production of IL-6, TNF-α and MCP-1, possibly, through the MEK and p38 MAPK pathways. It also promoted the nuclear translocation of NF-κB p50 and p65, the upregulation of MHC-II, and the activation of T CD4+ cells. These results suggest that pCry1Ac induced macrophage activation through mechanisms which differ partially from the LPS-induced.

Curcumin prevents replication of respiratory syncytial virus and the epithelial responses to it in human nasal epithelial cells

The human nasal epithelium is the first line of defense during respiratory virus infection. Respiratory syncytial virus (RSV) is the major cause of bronchitis, asthma and severe lower respiratory tract disease in infants and young children. We previously reported in human nasal epithelial cells (HNECs), the replication and budding of RSV and the epithelial responses, including release of proinflammatory cytokines and enhancement of the tight junctions, are in part regulated via an NF-κB pathway. In this study, we investigated the effects of the NF-κB in HNECs infected with RSV. Curcumin prevented the replication and budding of RSV and the epithelial responses to it without cytotoxicity. Furthermore, the upregulation of the epithelial barrier function caused by infection with RSV was enhanced by curcumin. Curcumin also has wide pharmacokinetic effects as an inhibitor of NF-κB, eIF-2α dephosphorylation, proteasome and COX2. RSV-infected HNECs were treated with the eIF-2α dephosphorylation blocker salubrinal and the proteasome inhibitor MG132, and inhibitors of COX1 and COX2. Treatment with salubrinal, MG132 and COX2 inhibitor, like curcumin, prevented the replication of RSV and the epithelial responses, and treatment with salubrinal and MG132 enhanced the upregulation of tight junction molecules induced by infection with RSV. These results suggest that curcumin can prevent the replication of RSV and the epithelial responses to it without cytotoxicity and may act as therapy for severe lower respiratory tract disease in infants and young children caused by RSV infection.

Failure of respiratory defenses in the pathogenesis of bacterial pneumonia of cattle

The respiratory system is well defended against inhaled bacteria by a dynamic system of interacting layers, including mucociliary clearance, host defense factors including antimicrobial peptides in the epithelial lining fluid, proinflammatory responses of the respiratory epithelium, resident alveolar macrophages, and recruited neutrophils and monocytes. Nevertheless, these manifold defenses are susceptible to failure as a result of stress, glucocorticoids, viral infections, abrupt exposure to cold air, and poor air quality. When some of these defenses fail, the lung can be colonized by bacterial pathogens that are equipped to evade the remaining defenses, resulting in the development of pneumonia. This review considers the mechanisms by which these predisposing factors compromise the defenses of the lung, with a focus on the development of bacterial pneumonia in cattle and supplemented with advances based on mouse models and the study of human disease. Deepening our understanding of how the respiratory defenses fail is expected to lead to interventions that restore these dynamic immune responses and prevent disease.

Marked induction of matrix metalloproteinase-10 by respiratory syncytial virus infection in human nasal epithelial cells

Respiratory syncytial virus (RSV) is an important pathogen of bronchiolitis, asthma, and severe lower respiratory tract disease in infants and young children. Matrix metalloproteinases (MMPs) play key roles in viral infection, inflammation and remodeling of the airway. However, the roles and regulation of MMPs in human nasal epithelial cells (HNECs) after RSV infection remain unclear. To investigate the regulation of MMP induced after RSV infection in HNECs, an RSV-infected model of HNECs in vitro was used. It was found that mRNA of MMP-10 was markedly increased in HNECs after RSV infection, together with induction of mRNAs of MMP-1, -7, -9, and -19. The amount of MMP-10 released from HNECs was also increased in a time-dependent manner after RSV infection as was that of chemokine RANTES. The upregulation of MMP-10 in HNECs after RSV infection was prevented by inhibitors of NF-κB and pan-PKC with inhibition of RSV replication, whereas it was prevented by inhibitors of JAK/STAT, MAPK, and EGF receptors without inhibition of RSV replication. In lung tissue of an infant with severe RSV infection in which a few RSV antibody-positive macrophages were observed, MMP-10 was expressed at the apical side of the bronchial epithelial cells and alveolar epithelial cells. In conclusion, MMP-10 induced by RSV infection in HNECs is regulated via distinct signal transduction pathways with or without relation to RSV replication. MMP-10 may play an important role in the pathogenesis of RSV diseases and it has the potential to be a novel marker and therapeutic target for RSV infection.

Alveolar macrophages contribute to respiratory tolerance by inducing FoxP3 expression in naive T cells

Alveolar macrophages (AMs) from mice and humans have long been known to contribute to maintaining tolerance in the lung. Studies have shown that AMs can induce anergy in CD4(+) T cells. Nitric oxide, prostaglandins, and leukotrienes have been implicated in AM-mediated tolerance. However, it remains unclear what effect, if any, AMs exert on FoxP3 induction in CD4(+) T cells from mice and humans, and whether or not other immunomodulators might play a role. AMs were isolated from bronchoalveolar lavage (BAL) fluid from either mice or humans, and cocultured with enriched naive CD4(+)FoxP3(-) T cells. We show here for the first time that AMs and AM-conditioned media (AM-CM) from mice and humans induced FoxP3 expression in naive CD4(+) T cells in vitro, an outcome that was reversed in part either by inhibiting retinoic acid (RA) binding to its receptor (RAR), or by blocking transforming growth factor (TGF)-β₁ signaling. A nasal administration of the RAR antagonist reduced the frequencies of CD4(+)FoxP3(+) T cells in the lungs of mice after aerosol challenge with Bordetella pertussis. In addition, we found that the intranasal vaccination of mice with ovalbumin (OVA) protein in conjunction with an RAR inhibitor led to a significant increase in OVA-specific serum IgE. Our findings suggest that AMs can mediate tolerance in the lungs of mice and humans via RA and TGF-β₁. These data may have implications in the development of nasal vaccines in the future.

Viral infection of the lung: host response and sequelae

Because of its essential role in gas exchange and oxygen delivery, the lung has evolved a variety of strategies to control inflammation and maintain homeostasis. Invasion of the lung by pathogens (and in some instances exposure to certain noninfectious particulates) disrupts this equilibrium and triggers a cascade of events aimed at preventing or limiting colonization (and more importantly infection) by pathogenic microorganisms. In this review we focus on viral infection of the lung and summarize recent advances in our understanding of the triggering of innate and adaptive immune responses to viral respiratory tract infection, mechanisms of viral clearance, and the well-recognized consequences of acute viral infection complicating underlying lung diseases, such as asthma.

Vitamin D induces interleukin-1β expression: paracrine macrophage epithelial signaling controls M. tuberculosis infection

Although vitamin D deficiency is a common feature among patients presenting with active tuberculosis, the full scope of vitamin D action during Mycobacterium tuberculosis (Mtb) infection is poorly understood. As macrophages are the primary site of Mtb infection and are sites of vitamin D signaling, we have used these cells to understand the molecular mechanisms underlying modulation of the immune response by the hormonal form of vitamin D, 1,25-dihydroxyvitamin D (1,25D). We found that the virulent Mtb strain H37Rv elicits a broad host transcriptional response. Transcriptome profiling also revealed that the profile of target genes regulated by 1,25D is substantially altered by infection, and that 1,25D generally boosts infection-stimulated cytokine/chemokine responses. We further focused on the role of 1,25D- and infection-induced interleukin 1β (IL-1β) expression in response to infection. 1,25D enhanced IL-1β expression via a direct transcriptional mechanism. Secretion of IL-1β from infected cells required the NLRP3/caspase-1 inflammasome. The impact of IL-1β production was investigated in a novel model wherein infected macrophages were co-cultured with primary human small airway epithelial cells. Co-culture significantly prolonged survival of infected macrophages, and 1,25D/infection-induced IL-1β secretion from macrophages reduced mycobacterial burden by stimulating the anti-mycobacterial capacity of co-cultured lung epithelial cells. These effects were independent of 1,25D-stimulated autophagy in macrophages but dependent upon epithelial IL1R1 signaling and IL-1β-driven epithelial production of the antimicrobial peptide DEFB4/HBD2. These data provide evidence that the anti-microbial actions of vitamin D extend beyond the macrophage by modulating paracrine signaling, reinforcing its role in innate immune regulation in humans.

In 2010 there were ∼9 million cases of tuberculosis and 1.4 million deaths, representing the second largest cause of death worldwide and the leading cause of death from a curable disease. M. tuberculosis (Mtb) replicates within cells of the immune system called macrophages over an approximate 72 hour period, ultimately inducing cell death. Notably, macrophages are sites of vitamin D signaling, and there is broad evidence that vitamin D modulates macrophage responses to Mtb. Elevated levels of TB have long been associated with vitamin D deficiency, strongly suggesting that vitamin D supplementation may be of therapeutic benefit. In this study we profile the host macrophage response to Mtb infection through the use of high-throughput genomics techniques. From this we have discovered that the dominant function of vitamin D is the modulation of the levels of specific cytokines, mediators of immune cell to cell signaling. Of particular interest was the increase in IL-1β signaling, which we show to be directly regulated by vitamin D. We also show that this increase in IL-1β is critical for driving a signaling cascade between macrophages and lung epithelial cells leading to epithelial antimicrobial peptide production that helps to contain Mtb infection in our model culture system.

Role of staphylococcal superantigens in airway disease

Staphylococcus aureus is a common human pathogen, which is regularly part of the normal microflora found in the nose and skin. It represents a significant threat to human health, not in the least because of its capability to produce exotoxins, which have superantigenic properties. These exotoxins, in particular the staphylococcal enterotoxins (SEs), are known to be involved in the modulation and aggravation of airway inflammation. Indeed, recent studies show an important impact of SEs on the natural course of allergic rhinitis, nasal polyposis, asthma and COPD. This review outlines the current knowledge on the influence of SEs on airway inflammation. We highlight, in particular, the recent evidence on their role in asthma.

Mucosal and systemic immune responses to Mycobacterium tuberculosis antigen 85A following its co-delivery with CpG, MPLA or LTB to the lungs in mice

Pulmonary vaccination is a promising route for immunization against tuberculosis because the lung is the natural site of infection with Mycobacterium tuberculosis. Yet, adjuvants with a suitable safety profile need to be found to enhance mucosal immunity to recombinant antigens. The aim of this study was to evaluate the immunogenicity, the safety and the protective efficacy of a subunit vaccine composed of the immunodominant mycolyl-transferase antigen 85A (Ag85A) and one of three powerful mucosal adjuvants: the oligodeoxynucleotide containing unmethylated cytosine-phosphate-guanine motifs (CpG), the monophosphoryl lipid A of Salmonella minnesota (MPLA) or the B subunit of heat-labile enterotoxin of Escherichia coli (LTB). BALB/c mice were vaccinated in the deep lungs. Our results showed that lung administration of these adjuvants could specifically induce different types of T cell immunity. Both CpG and MPLA induced a Th-1 type immune response with significant antigen-specific IFN-γ production by spleen mononuclear cells in vitro and a tendency of increased IFN-γ in the lungs. Moreover, MPLA triggered a Th-17 response reflected by high IL-17A levels in the spleen and lungs. By contrast, LTB promoted a Th-2 biased immune response, with a production of IL-5 but not IFN-γ by spleen mononuclear cells in vitro. CpG did not induce inflammation in the lungs while LTB and MPLA showed a transient inflammation including a neutrophil influx one day after pulmonary administration. Pulmonary vaccination with Ag85A without or with MPLA or LTB tended to decrease bacterial counts in the spleen and lungs following a virulent challenge with M. tuberculosis H37Rv. In conclusion, CpG and MPLA were found to be potential adjuvants for pulmonary vaccination against tuberculosis, providing Th-1 and Th-17 immune responses and a good safety profile.

IL-7 production in murine lymphatic endothelial cells and induction in the setting of peripheral lymphopenia

IL-7 is a required factor for T-cell homeostasis. Because of low expression levels and poor reagent availability, the cellular sources of IL-7 have proven challenging to characterize. In this study, we describe a reporter mouse in which enhanced GFP is expressed from the endogenous Il7 locus. We show that IL-7 is produced by lymphatic endothelial cells (LECs) distributed throughout the systemic lymphatic vasculature as well as by fibroblastic reticular cells, and that phosphorylation of STAT5 in lymphocytes is higher in lymphatics than in blood. Furthermore, in nodes depleted of lymphocytes, Il7 transcription is increased in stromal but not in myeloid subsets. These data support recent findings that lymphocyte homeostasis is influenced by access to secondary lymphoid organs and point to LECs as an important in vivo source of IL-7, bathing trafficking immune cells under both resting and lymphopenic conditions.

The alveolar microenvironment of patients infected with human immunodeficiency virus does not modify alveolar macrophage interactions with Streptococcus pneumoniae

We tested the hypothesis that HIV infection results in activation of alveolar macrophages and that this might be associated with impaired defense against pneumococcus. We compared alveolar macrophages and lymphocytes in 131 bronchoalveolar lavage samples from HIV-infected and healthy controls using inflammatory gene microarrays, flow cytometry, real-time PCR, and enzyme-linked immunosorbent assay (ELISA) to determine the pattern of macrophage activation associated with HIV infection and the effect of this activation on defense against pneumococcus. We used gamma interferon (IFN-γ) priming to mimic the cellular milieu in HIV-infected lungs. InnateDB and BioLayout 3D were used to analyze the interactions of the upregulated genes. Alveolar macrophages from HIV-infected adults showed increased gene expression and cytokine production in a classical pattern. Bronchoalveolar lavage from HIV-infected subjects showed excess CD8(+) lymphocytes with activated phenotype. Toll-like receptor 4 (TLR4) expression was increased in macrophages from HIV-infected subjects, but function was similar between the groups; lung lavage fluid did not inhibit TLR function in transfected HeLa cells. Alveolar macrophages from HIV-infected subjects showed normal binding and internalization of opsonized pneumococci, with or without IFN-γ priming. Alveolar macrophages from HIV-infected subjects showed classical activation compared to that of healthy controls, but this does not alter macrophage interactions with pneumococci.

The influence of cigarette smoking on viral infections: translating bench science to impact COPD pathogenesis and acute exacerbations of COPD clinically

COPD is a complex syndrome that poses a serious health threat to &gt;1.1 billion smokers worldwide. The stable disease is punctuated by episodes of acute exacerbation, which are predominantly the result of viral and bacterial infections. Despite their devastating health impact, mechanisms underlying disease exacerbations remain poorly understood. Mounting evidence suggests that cigarette smoke profoundly affects the immune system, compromising the host's ability to mount appropriate immune and inflammatory responses against microbial agents. This review highlights recent advances in our understanding of the impact of cigarette smoke on type 1 interferon and IL-1 signaling cascades. The immune defects caused by cigarette smoke on these two key pathways contribute to the seemingly contradictory nature of cigarette smoke as both a damaging and a proinflammatory factor as well as an immunosuppressive factor. Understanding the impact of cigarette smoke on the immune system may unravel novel targets for therapies that could affect acute exacerbations and COPD pathogenesis.

Activation of NLRP3 inflammasome in alveolar macrophages contributes to mechanical stretch-induced lung inflammation and injury

Mechanical ventilation of lungs is capable of activating the innate immune system and inducing sterile inflammatory response. The proinflammatory cytokine IL-1β is among the definitive markers for accurately identifying ventilator-induced lung inflammation. However, mechanisms of IL-1β release during mechanical ventilation are unknown. In this study, we show that cyclic stretch activates the nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasomes and induces the release of IL-1β in mouse alveolar macrophages via caspase-1- and TLR4-dependent mechanisms. We also observed that NADPH oxidase subunit gp91(phox) was dispensable for stretch-induced cytokine production, whereas mitochondrial generation of reactive oxygen species was required for stretch-induced NLRP3 inflammasome activation and IL-1β release. Further, mechanical ventilation activated the NLRP3 inflammasomes in mouse alveolar macrophages and increased the production of IL-1β in vivo. IL-1β neutralization significantly reduced mechanical ventilation-induced inflammatory lung injury. These findings suggest that the alveolar macrophage NLRP3 inflammasome may sense lung alveolar stretch to induce the release of IL-1β and hence may contribute to the mechanism of lung inflammatory injury during mechanical ventilation.

TRIF is required for TLR4 mediated adjuvant effects on T cell clonal expansion

Toll like receptor 4 (TLR4) is an important pattern recognition receptor with the ability to drive potent innate immune responses and also to modulate adaptive immune responses needed for long term protection. Activation of TLR4 by its ligands is mediated by engagement of the adapter proteins MyD88 (myeloid differentiation factor 88) and TRIF (Toll-interleukin 1 receptor domain-containing adapter inducing interferon-beta). Previously, we showed that TRIF, but not MyD88, plays an important role in allowing TLR4 agonists to adjuvant early T cell responses. In this study, we investigated the T cell priming events that are regulated specifically by the TRIF signaling branch of TLR4. We found that TRIF deficiency prevented the TLR4 agonist lipid A from enhancing T cell proliferation and survival in an adoptive transfer model of T cell priming. TRIF deficient DC showed defective maturation as evidenced by their failure to upregulate co-stimulatory molecules in response to lipid A stimulation. Importantly, TRIF alone caused CD86 and CD40 upregulation on splenic DC, but both TRIF and MyD88 were required for CD80 upregulation. The impairment of T cell adjuvant effects and defective DC maturation in TRIF ^lps/lps mice after TLR4 stimulation was mainly due to loss of type I IFN production, indicating that type I interferons are central to TLR4's adjuvant effects. These results are useful for the continued development of TLR4 based vaccine adjuvants that avoid inflammatory risks while retaining beneficial immune response.

Nasally administered Lactobacillus rhamnosus accelerate the recovery of humoral immunity in B lymphocyte-deficient malnourished mice

The ability of nasally administered Lactobacillus rhamnosus CRL1505 to accelerate the recovery of respiratory B cell-mediated immunity against pneumococcal infection in replete malnourished mice was evaluated. Weaned mice were malnourished after consumption of a protein-free diet for 21 d. Malnourished mice were fed a balanced conventional diet (BCD) for 7 d (BCD group) or a BCD for 7 d with supplemental L. rhamnosus CRL1505 by the nasal route during the last 2 d (BCD+Lr group). Nonreplete malnourished and normal mice were used as the malnourished (MNC) and the well-nourished (WNC) control groups, respectively. Mice were challenged with Streptococcus pneumoniae at the end of each dietary treatment. The immune response was studied before the challenge and at different times postinfection. The MNC mice had less resistance to pneumococcal infection, fewer mature and immature B cells in lung and spleen, and a reduced production of specific antibodies compared with WNC mice. The BCD treatment did not induce a complete normalization of the number B cell populations and antibody amounts. However, the BCD+Lr group had normal numbers of spleen and lung B cells. Moreover, the BCD+Lr mice had a significantly lower susceptibility to S. pneumoniae infection and higher amounts of anti-pneumococcal antibodies. Although further studies are necessary to clarify the effect of malnutrition and nasally administered lactobacilli in other immune cell populations involved in the protection against respiratory pathogens, this work gives evidence of the importance of using nasal priming with probiotics to accelerate the recovery of respiratory immunity in immunocompromised malnourished hosts.

Vitamin D and respiratory infections in infants and toddlers: a nutri-shine perspective

There is compelling evidence of a global problem of poor vitamin D status in expecting mothers and postnatal life; and even more critical, is the evidence showing the association of vitamin D deficiency with increased morbidity and mortality risks from respiratory infections. Viral and bacterial pneumonia kills more children than any other illness, accounting for 19 % of all deaths in children less than five years of age worldwide; and under-nutrition, which includes vitamin D insufficiency/deficiency, has been implicated in 53 % of all these deaths. Poor vitamin D status is a result of insufficient sunlight exposure and/or poor dietary intake. Greater understanding of the role of vitamin D deficiency in precipitating lung infections grew from the use of rodent models and observational and intervention studies in infants and toddlers. Vitamin D adequacy is important to maintaining the key protective mechanism of developing lungs since it mediates the synthesis of antimicrobial peptides, the lungs strongest defense against viral and bacterial pathogens. If vitamin D intervention currently under study in several clinical trials is proven successful, then implementation of new fortification practices, revised guidelines for healthy sun exposure and public health programs for vitamin D supplementation of pregnant/lactating women and their infants may be effective strategies to aide in preventing neonates and children under five from developing pneumonia. Globally, there is potential to save more than a million young lives with preventive treatment, a compelling reason why the efficacy of optimizing vitamin D mediated defense against respiratory pathogens in infants and children merits further study.

Assessment of immunotoxicity using precision-cut tissue slices

1.When the immune system encounters incoming infectious agents, this generally leads to immunity. The evoked immune response is usually robust, but can be severely perturbed by potentially harmful environmental agents such as chemicals, pharmaceuticals and allergens. 2.Immunosuppression, hypersensitivity and autoimmunity may occur due to changed immune activity. Evaluation of the immunotoxic potency of agents as part of risk assessment is currently established in vivo with animal models and in vitro with cell lines or primary cells. 3.Although in vivo testing is usually the most relevant situation for many agents, more and more in vitro models are being developed for assessment of immunotoxicity. In this context, hypersensitivity and immunosuppression are considered to be a primary focus for developing in vitro methods. Three-dimensional organotypic tissue models are also part of current research in immunotoxicology. 4.In recent years, there has been a revival of interest in organotypic tissue models. In the context of immunotoxicity testing, precision-cut lung slices in particular have been intensively studied. Therefore, this review is very much focused on pulmonary immunotoxicology. Respiratory hypersensitivity and inflammation are further highlighted aspects of this review. Immunotoxicity assessment currently is of limited use in other tissue models, which are therefore described only briefly within this review.

Novel cellular targets of AhR underlie alterations in neutrophilic inflammation and inducible nitric oxide synthase expression during influenza virus infection

The underlying reasons for variable clinical outcomes from respiratory viral infections remain uncertain. Several studies suggest that environmental factors contribute to this variation, but limited knowledge of cellular and molecular targets of these agents hampers our ability to quantify or modify their contribution to disease and improve public health. The aryl hydrocarbon receptor (AhR) is an environment-sensing transcription factor that binds many anthropogenic and natural chemicals. The immunomodulatory properties of AhR ligands are best characterized with extensive studies of changes in CD4(+) T cell responses. Yet, AhR modulates other aspects of immune function. We previously showed that during influenza virus infection, AhR activation modulates neutrophil accumulation in the lung, and this contributes to increased mortality in mice. Enhanced levels of inducible NO synthase (iNOS) in infected lungs are observed during the same time frame as AhR-mediated increased pulmonary neutrophilia. In this study, we evaluated whether these two consequences of AhR activation are causally linked. Reciprocal inhibition of AhR-mediated elevations in iNOS and pulmonary neutrophilia reveal that although they are contemporaneous, they are not causally related. We show using Cre/loxP technology that elevated iNOS levels and neutrophil number in the infected lung result from separate, AhR-dependent signaling in endothelial and respiratory epithelial cells, respectively. Studies using mutant mice further reveal that AhR-mediated alterations in these innate responses to infection require a functional nuclear localization signal and DNA binding domain. Thus, gene targets of AhR in non-hematopoietic cells are important new considerations for understanding AhR-mediated changes in innate anti-viral immunity.

Lung natural killer cells in mice: phenotype and response to respiratory infection

Natural killer (NK) cells have a specialized function in peripheral organs, which is determined by the organ-specific niches. We have attempted to explore whether lung NK cells display a particular phenotype according to their function in the unique pulmonary environment in health or during respiratory infection in mice. In healthy mice, higher frequencies of NK cells among lymphocytes were detected in the lung than in other tissues (lymph node, bone marrow, spleen, blood and liver), and lung NK cells maintained a more mature phenotype, implying that lung NK cells were critical for the pulmonary immune response. However, lung NK cells expressed higher levels of inhibitory receptors and lower levels of activating receptors, migration/adhesion-associated molecules and co-stimulatory molecules than splenic NK cells, implying that lung NK cells were quiescent, and the activation of lung NK cells was tightly regulated by the pulmonary environment in health. During respiratory infection, lung NK cells could be activated and express functional molecules (CD107a and interferon-γ) to take part in the response to infection quickly. These results suggested that the unique pulmonary environment promotes the development of NK cells with a lung-specific phenotype.

The pharmacological modulation of allergen-induced asthma

Aeroallergens are the most common triggers for the development of asthma. Recent birth cohort studies have identified viral infections occurring against a background of aeroallergen sensitization as a potent risk factor for initiation of asthma. Viral infection enhances immunopathogenic potential of pre-existing inhalant allergy via modulating airway mucosal dendritic cells. By using an allergen inhalation challenge clinical model, studies have shown that the late asthma response (LAR) is associated with more pronounced allergen-induced airway inflammation and airway hyperresponsiveness. The degree of airway eosinophilia, regulated by bone marrow progenitor cells and interleukin-5 level, correlates with the magnitude of the LAR and the increase in hyperresponsiveness. Both myeloid and plasmacytoid dendritic cell subsets have been involved in the pathogenesis of allergen-induced LAR. Myeloid dendritic cells are responsible for the allergen presentation and induction of inflammation and plasmacytoid dendritic cells play a role in the resolution of allergen-induced inflammation. A variety of potential new classes of asthma medication has also been evaluated with the allergen inhalation challenge in mild asthmatic subjects. Examples are TPI ASM8, an inhaled anti-sense oligonucleotide drug product, which attenuated both early and LARs via inhibition of the target gene mRNA of chemokine receptor 3, and the common β chain of interleukin-3, interleukin-5 and granulocyte-macrophage colony-stimulating factor receptor. Anti-human antibody interleukin-13 (IM-638) significantly attenuated both early and late allergen-induced asthma response. Pitrakinra, which targets both interleukin-4 and interleukin-13, substantially diminishes allergen-induced airway responses. Allergen-induced airway responses are a valuable way to evaluate the activity of possible new therapies in asthmatic airways.

Evasion of influenza A viruses from innate and adaptive immune responses

The influenza A virus is one of the leading causes of respiratory tract infections in humans. Upon infection with an influenza A virus, both innate and adaptive immune responses are induced. Here we discuss various strategies used by influenza A viruses to evade innate immune responses and recognition by components of the humoral and cellular immune response, which consequently may result in reduced clearing of the virus and virus-infected cells. Finally, we discuss how the current knowledge about immune evasion can be used to improve influenza A vaccination strategies.

Establishment of a reverse genetics system for studying human bocavirus in human airway epithelia

Human bocavirus 1 (HBoV1) has been identified as one of the etiological agents of wheezing in young children with acute respiratory-tract infections. In this study, we have obtained the sequence of a full-length HBoV1 genome (including both termini) using viral DNA extracted from a nasopharyngeal aspirate of an infected patient, cloned the full-length HBoV1 genome, and demonstrated DNA replication, encapsidation of the ssDNA genome, and release of the HBoV1 virions from human embryonic kidney 293 cells. The HBoV1 virions generated from this cell line-based production system exhibits a typical icosahedral structure of approximately 26 nm in diameter, and is capable of productively infecting polarized primary human airway epithelia (HAE) from the apical surface. Infected HAE showed hallmarks of lung airway-tract injury, including disruption of the tight junction barrier, loss of cilia and epithelial cell hypertrophy. Notably, polarized HAE cultured from an immortalized airway epithelial cell line, CuFi-8 (originally derived from a cystic fibrosis patient), also supported productive infection of HBoV1. Thus, we have established a reverse genetics system and generated the first cell line-based culture system for the study of HBoV1 infection, which will significantly advance the study of HBoV1 replication and pathogenesis.

Human bocavirus 1 (HBoV1) has been identified as one of the etiological agents of wheezing in young children with acute respiratory-tract infections. HBoV1 productively infects polarized primary human airway epithelia. However, no cell lines permissive to HBoV1 infection have yet been established. More importantly, the sequences at both ends of the HBoV1 genome have remained unknown. We have resolved both of these issues in this study. We have sequenced a full-length HBoV1 genome and cloned it into a plasmid. We further demonstrated that this HBoV1 plasmid replicated and produced viruses in human embryonic kidney 293 cells. Infection of these HBoV1 progeny virions produced obvious cytopathogenic effects in polarized human airway epithelia, which were represented by disruption of the epithelial barrier. Moreover, we identified an airway epithelial cell line supporting HBoV1 infection, when it was polarized. This is the first study to obtain the full-length HBoV1 genome, to demonstrate pathogenesis of HBoV1 infection in human airway epithelia, and to identify the first cell line to support productive HBoV1 infection.

Immunogenicity and protective efficacy of heterologous prime-boost regimens with mycobacterial vaccines and recombinant adenovirus- and poxvirus-vectored vaccines against murine tuberculosis

OBJECTIVES

To evaluate regimens using bacillus Calmette-Guérin (BCG) or recombinant BCG (rBCG) overexpressing Ag85B for priming, followed by boosting with a modified vaccinia virus Ankara strain (MVA) and/or adenovirus vector (AD) expressing an Ag85B-ESAT6 fusion protein.

METHODS

Cellular and humoral immune responses were determined after subcutaneous vaccination, which was employed to trigger systemic immunity against intravenous infection in a mouse model of tuberculosis (TB). Bacterial loads and lung histology were evaluated.

RESULTS

The relative IgG2a and IgG1 antibody levels indicated that the viral-vectored vaccines generated a T-helper type 1 (Th1)-biased response after two doses of viral boost vaccinations. Boosting BCG-primed mice with viral vaccines induced a Th1 immune response that included both CD4 and CD8 T-cells generating antigen-specific interferon-gamma (IFN-γ) and CD8 T cytotoxic activity. Only mice vaccinated with two different viral boosters after BCG priming exhibited a significant reduction in bacterial burden in the lung after challenge. Histology examinations confirmed the attenuation of lung damage and more compact granulomas. After mycobacteria priming, boosting with AD85B-E6 followed by MVA85B-E6 afforded better protection than the reverse order of administration of the viral vectors.

CONCLUSIONS

This study demonstrates the potential of multiple heterologous viral booster vaccines, although the exact correlates of protection and optimal regimens should be further investigated for the rational design of future vaccine strategies.

Therapeutical measures to control airway tolerance in asthma and lung cancer

Airway tolerance is a specialized immunological surveillance which is activated by the cells of the lung to deal with and distinguish between innocuous and pathogenic inhalants. However, this distinction does not always occur. Airway tolerance is necessary to avoid the development of allergic disorders, such as asthma, which is dominated by a pathological expansion of Th2 and Th17 cells in the airways. By contrast, tumor cells induce tolerogenic factors in their microenvironment to evade T-cell mediated anti-tumor-immune responses. This review updates current understandings on the effect of the cytokines TGF-β, IL-10, and IL-17A on the lung immune responses to antigen, and analyzes their involvement in allergic asthma and lung cancer. The aim of the review is to evaluate where therapeutic intervention may be feasible and where it might fail. The multifunctional role of these cytokines further complicates the decision on the timing and concentration for their use as therapeutical targets. In fact, TGF-β has suppressive activity in early tumorigenesis, but may become tumor-promoting in the later stages of the disease. This dual behavior is sometimes due to changes in the cellular target of TGF-β, and to the expansion of the induced (i)-Tregs. Similarly, IL-17A has been found to elicit pro- as well as anti-tumor properties. Thus, this pro-inflammatory cytokine induces the production of IL-6 which interferes with Treg development. Yet IL-17A could promote tumor growth in conjunction with IL-6-dependent activation of Stat3. Thus, understanding the mechanisms of airway tolerance could help to improve the therapy to both, allergic asthma and lung cancer. Hereby, asthma therapy aims to induce and maintain tolerance to inhaled allergens and therapy against lung cancer tries to inhibit the tolerogenic response surrounding the tumor.