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Besides providing an essential protective barrier, airway epithelial cells directly sense pathogens and respond defensively. This is a frontline component of the innate immune system with specificity for different pathogen classes. It occurs in the context of numerous interactions with leukocytes, but here we focus on intrinsic epithelial mechanisms. Type 1 immune responses are directed primarily at intracellular pathogens, particularly viruses. Prominent stimuli include microbial nucleic acids and interferons released from neighboring epithelial cells. Epithelial responses revolve around changes in the expression of interferon-sensitive genes (ISGs) that interfere with viral replication, as well as the further induction of interferons that signal in autocrine and paracrine manners. Type 2 immune responses are directed primarily at helminths and fungi. Prominent pathogen stimuli include proteases and chitin, and important responses include mucin hypersecretion and chitinase release. Type 3 immune responses are directed primarily at extracellular microbial pathogens, including bacteria and fungi, as well as viruses during their extracellular phase of infection. Prominent microbial stimuli include bacterial wall components, such as lipopeptides and endotoxin, as well as microbial nucleic acids. Key responses are the release of reactive oxygen species (ROS) and antimicrobial peptides (AMPs). For all three types of response, paracrine signaling to neighboring epithelial cells induces resistance to infection over a wide field. Often, the epithelial effector molecules themselves also have signaling properties, in addition to the release of inflammatory cytokines that boost local innate immunity. Together, these epithelial mechanisms provide a powerful first line of pathogen defense, recruit leukocytes, and instruct adaptive immune responses.

Allergic asthma is a chronic inflammatory respiratory disease associated with eosinophilic infiltration, increased mucus production, airway hyperresponsiveness (AHR), and airway remodeling. Epidemiologic data has revealed that the prevalence of allergic sensitization and associated diseases has increased in the twentieth century. This has been hypothesized to be partly due to reduced contact with microbial organisms (the hygiene hypothesis) in industrialized society. Airway epithelial cells, once considered a static physical barrier between the body and the external world, are now widely recognized as immunologically active cells that can initiate, maintain, and restrain inflammatory responses, such as those that mediate allergic disease. Airway epithelial cells can sense allergens via myriad expression of Toll-like receptors (TLRs) and other pattern-recognition receptors (PRRs). We sought to determine whether the innate immune response stimulated by a combination of Pam2CSK4 (“Pam2”, TLR2/6 ligand) and a class C oligodeoxynucleotide ODN362 (“ODN”, TLR9 ligand) when delivered together by aerosol (“Pam2ODN”), can modulate the allergic immune response to allergens. Treatment with Pam2ODN 7 days before sensitization to House Dust Mite (HDM) extract resulted in a strong reduction in eosinophilic and lymphocytic inflammation. This Pam2ODN immunomodulatory effect was also seen using Ovalbumin (OVA) and A. oryzae (Ao) mouse models. The immunomodulatory effect was observed as much as 30 days before sensitization to HDM, but ineffective just 2 days after sensitization, suggesting that Pam2ODN immunomodulation lowers the allergic responsiveness of airway epithelial cells. Furthermore, Pam2 and ODN cooperated synergistically suggesting that this treatment is superior to any single agonist in the setting of allergen immunotherapy.One Sentence SummaryA synergistic combination of Toll-like Receptor agonists, delivered directly into the lung mucosa, can attenuate allergic responsiveness of airway epithelial cells and prevent host sensitization to aeroallergens.What is already knownAllergic sensitization has increased in the 20th century due to reduced contact with microbial organisms in industrialized society (ie. hygiene hypothesis)We have previously identified a pharmacological means to stimulate innate immunity of lung epithelial cells.What this study addsActivation of innate immunity in lung epithelial cells attenuates the allergic responsiveness of mice.Synergistic cooperation of pattern recognition receptors induces stronger immunomodulatory responsesWhat is the clinical significanceAerosolized Toll-like Receptor agonists have been demonstrated as safe in human clinical trialsThis study provides proof-of-principle that aerosolized toll-like receptor agonists could have clinical efficacy in the setting of the allergen immunotherapy

Objective: Viral pneumonias cause significant morbidity and mortality worldwide. The emergence of novel SARSCoV- 2 emphasizes the need for novel antiviral therapies. Dexamethasone (DXM) is one therapy that has recently been reported to confer benefit in severe SARS-CoV-2 infection. Our lab has recently reported that CD8+ T cells were associated with fatal immunopathology causing mortality in a mouse model of severe Sendai paramyxovirus (SeV) pneumonia, and this fatal immunopathology could be prevented either by eliciting a robust, early antiviral response via inhalational treatment with Toll-like receptor agonists (Pam2-ODN) or by depletion of CD8+ T cells during late stage SeV pneumonia. Given the lympholytic effects of DXM, we tested our hypothesis that the reported survival advantage of DXM in severe viral pneumonia derives from CD8+ T cell- mediated immunopathology. Methods: Mice were intrapharyngeally infected with SeV with or without Pam2-ODN pretreatment, then observed for 14 days. Some mice were intraperitoneally injected with DXM (5mg/kg) every day starting day 0 or day 8 after infection. CD8+ T cells were assessed on day 10 after infection by flow cytometry of digested mouse lungs. Results: Treatment with DXM starting on day 8 enhanced mouse survival of SeV pneumonia, whereas mice treated with DXM from day -1 onward demonstrated increased susceptibility to SeV pneumonia. Mice treated with CD8+ T cell depleting antibody on day 8 displayed 100% survival. DXM treated mice displayed reduced CD8+ T cells in comparison to PBS treated SeV challenged mice, supporting our hypothesis. Consistent with our recent report, mice aerosolized with Pam2-ODN displayed 100% survival of SeV pneumonia with reduced CD8+ T cell lung influx on day 10. Conclusion: These data suggest that the survival benefit of DXM in severe viral pneumonia results from reduced CD8+ T cell-mediated immunopathology. Improved outcomes appear likely to be achieved by either use of broad immunosuppressive agents such as DXM or a targeted approach to deplete CD8+ T cells during late-stage pneumonia such as COVID19. These data also provide a preclinical model to test other immunosuppressive agents and optimize timing and dosing of such agents.

Viral pneumonias remain global health threats, as exemplified in the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, requiring novel treatment strategies both early and late in the disease process. We have reported that mice treated before or soon after infection with a combination of inhaled Toll-like receptor (TLR) 2/6 and 9 agonists (Pam2-ODN) are broadly protected against microbial pathogens including respiratory viruses, but the mechanisms remain incompletely understood. The objective of this study was to validate strategies for immune modulation in a preclinical model of viral pneumonia and determine their mechanisms. Mice were challenged with the Sendai paramyxovirus in the presence or absence of Pam2-ODN treatment. Virus burden and host immune responses were assessed to elucidate Pam2-ODN mechanisms of action and to identify additional opportunities for therapeutic intervention. Enhanced survival of Sendai virus pneumonia with Pam2-ODN treatment was associated with reductions in lung virus burden and with virus inactivation before internalization. We noted that mortality in sham-treated mice corresponded with CD8+ T-cell lung inflammation on days 11-12 after virus challenge, after the viral burden had declined. Pam2-ODN blocked this injurious inflammation by minimizing virus burden. As an alternative intervention, depleting CD8+ T cells 8 days after viral challenge also decreased mortality. Stimulation of local innate immunity within the lungs by TLR agonists early in disease or suppression of adaptive immunity by systemic CD8+ T-cell depletion late in disease improves outcomes of viral pneumonia in mice. These data reveal opportunities for targeted immunomodulation to protect susceptible human subjects.

Viral pneumonia remains a global health threat requiring novel treatment strategies, as strikingly exemplified in the SARS-CoV-2 pandemic of 2019-2020. We have reported that mice treated with a combination of inhaled Toll-like receptor (TLR) 2/6 and TLR 9 agonists (Pam2-ODN) to stimulate innate immunity are broadly protected against respiratory pathogens, but the mechanisms underlying this protection remain incompletely elucidated. Here, we show in a lethal paramyxovirus model that Pam2-ODN-enhanced survival is associated with robust virus inactivation by reactive oxygen species (ROS), which occurs prior to internalization by lung epithelial cells. However, we also found that mortality in sham-treated mice temporally corresponded with CD8+ T cell-enriched lung inflammation that peaks on days 11-12 after viral challenge, when the viral burden has waned to a scarcely detectable level. Pam2-ODN treatment blocked this injurious inflammation by reducing the viral burden, and alternatively, depleting CD8+ T cells 8 days after viral challenge also decreased mortality. These findings reveal opportunities for targeted immunomodulation to protect susceptible individuals against the morbidity and mortality of respiratory viral infections.

Viral pneumonias remain a global health threat necessitating novel strategies to prevent and treat these lower respiratory tract infections. We have reported that mice treated with a combination of inhaled Toll-like receptor (TLR) 2/6 and TLR 9 agonists (Pam2-ODN) are broadly protected against respiratory pathogens. Although a single inhalation of Pam-ODN prevents acute morbidity and chronic complications associated with viral pneumonias, the mechanisms underlying this protection remain incompletely elucidated. Here, we show in a lethal paramyxovirus model that Pam2-ODN-enhanced survival is associated with robust virus inactivation that occurs prior to internalization by lung epithelial cells. However, it was also noted that viral mortality in sham-treated mice temporally corresponded with CD8+ T cell-enriched lung inflammation that peaks after the viral burden wanes. Pam2-ODN treatment also blocked this injurious inflammation, but the attenuation of lymphocytic inflammation and the reduction in virus burden were both lost when inducible reactive oxygen species generation was inhibited. Depleting CD8+ T cells before or after viral challenge underscored the balanced roles of CD8+ T cells in antiviral immunity and fatal immunopathology, but did not obviate the Pam2-ODN antiviral protection. These findings identify multifunctional inducible antiviral mechanisms and may reveal means to protect susceptible individuals against respiratory infections.

Background and purpose Respiratory viral infections play central roles in the initiation, exacerbation and progression of asthma in humans. An acute paramyxoviral infection in mice can cause a chronic lung disease that resembles human asthma. We sought to determine whether reduction of Sendai virus lung burden in mice by stimulating innate immunity with aerosolized Toll-like receptor (TLR) agonists could attenuate the severity of chronic asthma-like lung disease. Experimental approach Mice were treated by aerosol with 1-μM oligodeoxynucleotide (ODN) M362, an agonist of the TLR9 homodimer, and 4-μM Pam2CSK4 (Pam2), an agonist of the TLR2/6 heterodimer, within a few days before or after Sendai virus challenge. Key results Treatment with ODN/Pam2 caused ~75% reduction in lung Sendai virus burden 5 days after challenge. The reduction in acute lung virus burden was associated with marked reductions 49 days after viral challenge in eosinophilic and lymphocytic lung inflammation, airway mucous metaplasia, lumenal mucus occlusion and hyperresponsiveness to methacholine. Mechanistically, ODN/Pam2 treatment attenuated the chronic asthma phenotype by suppressing IL-33 production by type 2 pneumocytes, both by reducing the severity of acute infection and by down-regulating Type 2 (allergic) inflammation. Conclusion and implications These data suggest that treatment of susceptible human hosts with aerosolized ODN and Pam2 at the time of a respiratory viral infection might attenuate the severity of the acute infection and reduce initiation, exacerbation and progression of asthma.

Respiratory viral infections play central roles in the initiation, exacerbation and progression of asthma in humans. An acute paramyxoviral infection in mice can cause a chronic lung disease that resembles human asthma. We sought to determine whether reduction of Sendai virus lung burden in mice by stimulating innate immunity with aerosolized Toll-like receptor (TLR) agonists could attenuate the severity of chronic asthma-like lung disease. Treatment with 1 µM oligodeoxynucleotide (ODN) M362, an agonist of the TLR9 homodimer, and 4 µM Pam2CSK4 (Pam2), an agonist of the TLR2/6 heterodimer, within a few days before or after Sendai virus challenge, resulted in a ∼75% reduction in lung Sendai virus burden five days after challenge. The reduction in acute lung virus burden was associated with marked reductions 49 days after viral challenge in eosinophilic and lymphocytic lung inflammation, airway mucous metaplasia, lumenal mucus occlusion, and hyperresponsiveness to methacholine. Mechanistically, ODN/Pam2 treatment attenuated the chronic asthma phenotype by suppressing IL-33 production by type 2 pneumocytes, both by reducing the severity of acute infection and by downregulating Type 2 (allergic) inflammation. These data suggest that treatment of susceptible human hosts with aerosolized ODN and Pam2 at the time of a respiratory viral infection might attenuate the severity of the acute infection and reduce progression of asthma.One Sentence SummaryRespiratory viral infections can induce chronic airway disease, and we find that stimulating innate immunity within the lungs of mice reduces the severity of acute infection and development of a chronic asthma phenotype.

Respiratory viral infections cause significant morbidity and mortality worldwide, necessitating the development of novel strategies to prevent complications of respiratory infections. Our group has discovered the phenomenon of inducible epithelial resistance where mice treated with combination inhalation of Toll-like receptor (TLR) 2/6 and TLR9 agonists (Pam2-ODN) are protected against respiratory pathogens, including viruses. We investigated the mouse survival benefits of paramyxovirus, Sendai (SeV) infection and found that Pam2-ODN treatment one day prior to SeV challenge enhanced survival of mice. This protection was associated with reduced CD8+ T cell inflammation. Depletion of CD8+T cells prior to infection increased baseline virus susceptibility but did not affect protection afforded by Pam2-ODN. Depletion of CD8+T cells after viral burden waned but before peak mortality enhanced SeV pneumonia survival, even in the absence of Pam2-ODN pretreatment, revealing the profound role of CD8+ T cell mediated immunopathology in virus-induced mortality. We further demonstrated that Pam2-ODN treatment controls viral replication by inactivation of SeV prior to epithelial internalization. Epithelial generation of reactive oxygen species induced by Pam2-ODN treatment is necessary for SeV inactivation and preventing CD8+T cell mediated immunopathology. These findings highlight antiviral mechanisms of inducible epithelial resistance and may provide means to protect vulnerable immunocompromised patients against respiratory diseases.

Recent studies have linked exposure to microbes and a reduction of allergic diseases. We sought to determine whether activation of innate immunity by aerosolized Toll-like receptor (TLR) agonists could attenuate the development of allergic inflammation in mice. BALB/cJ mice were sensitized and challenged with House Dust Mite (HDM). Some mice were treated by aerosol with ligands for TLR9 (ODNm362) and TLR2/6 (Pam2CSK4) in combination (Pam2-ODN). Allergic inflammation was assessed by quantification of leukocytes in bronchoalveolar lavage fluid (BALF) and epithelial mucin content with periodic acid fluorescent Schiff stain (PAFS). Pam2-ODN-treated mice exhibited a 94% reduction in eosinophils, 90% reduction in lymphocytes, and a 44% reduction in epithelial mucin content. Lymphocyte subset analysis showed a 50% reduction in TH2 cells without a detectable change in any other TH subset. Using an alternate allergic inflammation model with Ovalbumin (OVA) Pam2-ODN-treated mice showed greater than 50% reductions in total and OVA-specific IgE serum concentrations. IgG2a concentrations, which are reduced in OVA-sensitized mice, returned to baseline with Pam2-ODN treatment. There is a stark contrast of the efficacy in mice treated before and after sensitization that suggests Pam2-ODN may modulate the tendency of sensitization when exposed to aeroallergens. Previous studies have shown that lung epithelial cells are required for Pam2-ODN lung responses, and taken together with these new data, Pam2-ODN may reprogram airway epithelial cells to be tolerogenic to aeroallergens, but additional investigation is required to understand the precise molecular mechanism of Pam2-ODN in this context.

Viral pneumonias cause profound worldwide morbidity, necessitating novel strategies to prevent and treat these potentially lethal infections. Stimulation of intrinsic lung defenses via inhalation of synergistically acting Toll-like receptor (TLR) agonists protects mice broadly against pneumonia, including otherwise-lethal viral infections, providing a potential opportunity to mitigate infectious threats. As intact lung epithelial TLR signaling is required for the inducible resistance and as these cells are the principal targets of many respiratory viruses, the capacity of lung epithelial cells to be therapeutically manipulated to function as autonomous antiviral effectors was investigated. Our work revealed that mouse and human lung epithelial cells could be stimulated to generate robust antiviral responses that both reduce viral burden and enhance survival of isolated cells and intact animals. The antiviral protection required concurrent induction of epithelial reactive oxygen species (ROS) from both mitochondrial and dual oxidase sources, although neither type I interferon enrichment nor type I interferon signaling was required for the inducible protection. Taken together, these findings establish the sufficiency of lung epithelial cells to generate therapeutically inducible antiviral responses, reveal novel antiviral roles for ROS, provide mechanistic insights into inducible resistance, and may provide an opportunity to protect patients from viral pneumonia during periods of peak vulnerability. IMPORTANCE Viruses are the most commonly identified causes of pneumonia and inflict unacceptable morbidity, despite currently available therapies. While lung epithelial cells are principal targets of respiratory viruses, they have also been recently shown to contribute importantly to therapeutically inducible antimicrobial responses. This work finds that lung cells can be stimulated to protect themselves against viral challenges, even in the absence of leukocytes, both reducing viral burden and improving survival. Further, it was found that the protection occurs via unexpected induction of reactive oxygen species (ROS) from spatially segregated sources without reliance on type I interferon signaling. Coordinated multisource ROS generation has not previously been described against viruses, nor has ROS generation been reported for epithelial cells against any pathogen. Thus, these findings extend the potential clinical applications for the strategy of inducible resistance to protect vulnerable people against viral infections and also provide new insights into the capacity of lung cells to protect against infections via novel ROS-dependent mechanisms.

The mostly widely used bronchodilators in asthma therapy are β2-adrenoreceptor (β2AR) agonists, but their chronic use causes paradoxical adverse effects. We have previously determined that β2AR activation is required for expression of the asthma phenotype in mice, but the cell types involved are unknown. We now demonstrate that β2AR signaling in the airway epithelium is sufficient to mediate key features of the asthmatic responses to IL-13 in murine models. Our data show that inhibition of β2AR signaling with an aerosolized antagonist attenuates airway hyperresponsiveness (AHR), eosinophilic inflammation, and mucus-production responses to IL-13, whereas treatment with an aerosolized agonist worsens these phenotypes, suggesting that β2AR signaling on resident lung cells modulates the asthma phenotype. Labeling with a fluorescent β2AR ligand shows the receptors are highly expressed in airway epithelium. In β2AR-/- mice, transgenic expression of β2ARs only in airway epithelium is sufficient to rescue IL-13-induced AHR, inflammation, and mucus production, and transgenic overexpression in WT mice exacerbates these phenotypes. Knockout of β-arrestin-2 (βarr-2-/-) attenuates the asthma phenotype as in β2AR-/- mice. In contrast to eosinophilic inflammation, neutrophilic inflammation was not promoted by β2AR signaling. Together, these results suggest β2ARs on airway epithelial cells promote the asthma phenotype and that the proinflammatory pathway downstream of the β2AR involves βarr-2. These results identify β2AR signaling in the airway epithelium as capable of controlling integrated responses to IL-13 and affecting the function of other cell types such as airway smooth muscle cells.

Influenza pneumonia remains a common and debilitating viral infection despite vaccination programs and antiviral agents developed for prophylaxis and treatment. The neuraminidase inhibitor oseltamivir is frequently prescribed for established influenza A virus infections, but the emergence of neuraminidase inhibitor resistant viruses, a brief therapeutic window and competing diagnoses complicate its use. PUL-042 is a clinical stage, aerosol drug comprised of synthetic ligands for Toll-like receptor (TLR) 2/6 and TLR 9. This host-targeted, innate immune stimulant broadly protects against bacterial, fungal and viral pneumonias, including those caused by influenza, when given prophylactically to animals. This study evaluated the therapeutic antiviral effects of PUL-042 against established influenza A pneumonia, when given alone or in combination with oseltamivir. Mice were treated with PUL-042 aerosol, oseltamivir or both at varying time points before or after challenge with influenza pneumonia. Treating established, otherwise lethal influenza A pneumonia (>1 LD100) with multiple inhaled doses of PUL-042 aerosol plus oral oseltamivir resulted in greater mouse survival than treatment with either drug alone. Single agent PUL-042 also protected mice against established infections following challenges with lower viral inocula (approximately 1 LD20). Aerosolized oseltamivir further enhanced survival when co-delivered with PUL-042 aerosol. The prophylactic and therapeutic benefits of PUL-042 were similar against multiple strains of influenza virus. In vitro influenza challenge of human HBEC3kt lung epithelial cells revealed PUL-042-induced protection against infection that was comparable to that observed in vivo. These studies offer new insights into means to protect susceptible populations against influenza A pneumonia.

Pneumonia represents a leading cause of death. Recently, a novel treatment strategy for pneumonia has involved enhancing the host pulmonary innate immune response by pre-exposure to aerosolized toll-like receptor (TLR)9 and TLR2/6 agonists, known as O/P. O/P inhalation in mice has been demonstrated to prime the lung inflammatory response, and thus increase survival against subsequent pneumonia infection while producing barely detectable increases in systemic cytokines. Here, we examined the safety of O/P treatment when used in mice that are inflamed systemically. Swiss-Webster mice were treated with two doses of aerosolized O/P (1x or 8x) vs phosphate buffered saline (PBS) either immediately before intraperitoneal injection of 0.1 mg/kg lipopolysaccharide (LPS) or PBS (equivolume) or 2 hours after. Sickness responses (reduced body weight, food intake, activity and social interaction) were examined at 2 and 5.5 h post-treatment. Immediately following behavioral testing, mice were euthanized, perfused with PBS, and brains, spleens, livers and lungs snap frozen for assessment of pro-inflammatory cytokine mRNAs. While O/P treatment alone increased lung IL-1β, IFNγ and TNF-α, no such effects were observed in the brain, spleen or liver. Furthermore, there was no evidence that O/P treatment administered before or after LPS had any synergizing effect to potentiate the cytokine response to LPS in any compartment measured. Supportive of these findings were the measures of sickness behaviors that did not show any increased sickness response in O/P-treated mice exposed to LPS, suggestive that the cytokine signal produced in the lungs from O/P inhalation did not propagate to the brain and synergize with LPS-induced neuroinflammation. These findings support the safety of the use of O/P inhalation as a preventative measure against pneumonia and demonstrate a unique ability of the lungs to compartmentalize pulmonary inflammation and limit propagation of the cytokine signal to the brain.

Infectious pneumonias are a leading cause of death worldwide, particularly among immunocompromised patients. Therapeutic stimulation of the lungs’ intrinsic defenses with a unique combination of inhaled Toll-like receptor agonists broadly protects mice against otherwise lethal pneumonias. As the survival benefit persists despite cytotoxic chemotherapy-related neutropenia, the cells required for protection were investigated. The inducibility of resistance was tested in mice with deficiencies of leukocyte lineages due to genetic deletions and in wild type mice with leukocyte populations significantly reduced by antibodies or toxins. Surprisingly, these serial reductions in leukocyte lineages did not appreciably impair inducible resistance, but targeted disruption of Toll-like receptor signaling in the lung epithelium resulted in complete abrogation of the protective effect. Isolated lung epithelial cells were also induced to kill pathogens in the absence of leukocytes. Proteomic and gene expression analyses of isolated epithelial cells and whole lungs revealed highly congruent antimicrobial responses. Taken together, these data indicate that lung epithelial cells are necessary and sufficient effectors of inducible resistance. These findings challenge conventional paradigms about the role of epithelia in antimicrobial defense and offer a novel potential intervention to protect patients with impaired leukocyte-mediated immunity from fatal pneumonias.

Respiratory surfaces are exposed to billions of particulates and pathogens daily. A protective mucus barrier traps and eliminates them through mucociliary clearance (MCC). However, excessive mucus contributes to transient respiratory infections and to the pathogenesis of numerous respiratory diseases. MUC5AC and MUC5B are evolutionarily conserved genes that encode structurally related mucin glycoproteins, the principal macromolecules in airway mucus. Genetic variants are linked to diverse lung diseases, but specific roles for MUC5AC and MUC5B in MCC, and the lasting effects of their inhibition, are unknown. Here we show that mouse Muc5b (but not Muc5ac) is required for MCC, for controlling infections in the airways and middle ear, and for maintaining immune homeostasis in mouse lungs, whereas Muc5ac is dispensable. Muc5b deficiency caused materials to accumulate in upper and lower airways. This defect led to chronic infection by multiple bacterial species, including Staphylococcus aureus, and to inflammation that failed to resolve normally. Apoptotic macrophages accumulated, phagocytosis was impaired, and interleukin-23 (IL-23) production was reduced in Muc5b(-/-) mice. By contrast, in mice that transgenically overexpress Muc5b, macrophage functions improved. Existing dogma defines mucous phenotypes in asthma and chronic obstructive pulmonary disease (COPD) as driven by increased MUC5AC, with MUC5B levels either unaffected or increased in expectorated sputum. However, in many patients, MUC5B production at airway surfaces decreases by as much as 90%. By distinguishing a specific role for Muc5b in MCC, and by determining its impact on bacterial infections and inflammation in mice, our results provide a refined framework for designing targeted therapies to control mucin secretion and restore MCC.

Despite widespread infection prevention efforts, pneumonia remains the leading cause of death among patients with acute leukemia, due to complex disease- and treatment-dependent immune defects. We have reported that a single inhaled treatment with a synergistic combination of Toll-like receptor 2/6 (TLR 2/6) and TLR9 agonists (Pam2-ODN) induces protective mucosal defenses in mice against a broad range of pathogens. As Pam2-ODN-induced protection persists despite depletion of several leukocyte populations, we tested whether it could prevent pneumonia in a mouse model of acute myeloid leukemia (AML) remission induction therapy. Pam2-ODN prevented death due to pneumonia caused by Pseudomonas aeruginosa, Streptococcus pneumoniae, and Aspergillus fumigatus when mice were heavily engrafted with leukemia cells, had severe chemotherapy-induced neutropenia or both. Pam2-ODN also extended survival of pneumonia in NSG mice engrafted with primary human AML cells. Protection was associated with rapid pathogen killing in the lungs at the time of infection and with reduced pathogen burdens at distant sites at the end of observation. Pathogen killing was inducible directly from isolated lung epithelial cells and was not abrogated by the presence of leukemia cells or cytotoxic agents. Pam2-ODN had no discernible effect on replication rate, total tumor population, or killing by chemotherapy of mouse or human leukemia cells, either in vitro or in vivo. Taken together, we report that therapeutic stimulation of lung epithelial defenses robustly protects against otherwise lethal pneumonias despite the profound immune dysfunction associated with acute leukemia and its treatment. These findings may suggest an opportunity to protect this population during periods of peak vulnerability.

Airway mucin secretion and MC (mast cell) degranulation must be tightly controlled for homoeostasis of the lungs and immune system respectively. We found the exocytic protein Munc18b to be highly expressed in mouse airway epithelial cells and MCs, and localized to the apical pole of airway secretory cells. To address its functions, we created a mouse with a severely hypomorphic Munc18b allele such that protein expression in heterozygotes was reduced by ~50%. Homozygous mutant mice were not viable, but heterozygotes showed a ~50% reduction in stimulated release of mucin from epithelial cells and granule contents from MCs. The defect in MCs affected only regulated secretion and not constitutive or transporter-mediated secretion. The severity of passive cutaneous anaphylaxis was also reduced by ~50%, showing that reduction of Munc18b expression results in an attenuation of physiological responses dependent on MC degranulation. The Munc18b promoter is controlled by INR (initiator), Sp1 (specificity protein 1), Ets, CRE (cAMP-response element), GRE (glucocorticoid-response element), GATA and E-box elements in airway epithelial cells; however, protein levels did not change during mucous metaplasia induced by allergic inflammation. Taken together, the results of the present study identify Munc18b as an essential gene that is a limiting component of the exocytic machinery of epithelial cells and MCs.

Epithelial surfaces throughout the body continuously sample and respond to environmental stimuli. The accessibility of lung epithelium to inhaled therapies makes it possible to stimulate local antimicrobial defences with aerosolized innate immune ligands. This strategy has been shown to be effective in preclinical models, as delivery of innate immune ligands to the lungs of laboratory animals results in protection from subsequent challenge with microbial pathogens. Survival of the animal host in this setting correlates directly with killing of pathogens within the lungs, indicating the induction of a resistance mechanism. Resistance appears to be mediated primarily by activated epithelial cells rather than recruited leucocytes. Resistance reaches a peak within hours and persists for several days. Innate immune ligands can interact synergistically under some circumstances, and synergistic combinations of innate ligands delivered by aerosol are capable of inducing a high level of broad host resistance to bacteria, fungi and viruses. The induction of innate antimicrobial resistance within the lungs could have clinical applications in the prevention of lower respiratory tract infection in subjects transiently at high risk. These include cancer patients undergoing myeloablative chemotherapy, intubated patients being mechanically ventilated, vulnerable individuals during seasonal influenza epidemics, asthmatic subjects experiencing a respiratory viral infection, and healthy subjects exposed to virulent pathogens from a bioterror attack or emergent pandemic. In summary, stimulation of the lung epithelium to induce localized resistance to infection is a novel strategy whose clinical utility will be assessed in the near future.

Respiratory viruses are frequent causes of asthma development and exacerbations. However, there are gaps in understanding how viral infections cause immuno-pathology in the host leading to asthma progression. We have previously shown that mice treated with a combination of Toll-like receptor (TLR) 2/6 and 9 agonists (Pam2-ODN) are protected against broad range of respiratory infections induced by viruses, fungi and bacteria. Pam2-ODN treatment one day prior to virus infection leads to enhanced survival with reduced lung viral burden in mice. Further, Pam2-ODN pretreatment also inhibits acute lung pathology caused by CD8+ T cells and prevents chronic asthmatic phenotype of eosinophilia, airway hyperreactivity and mucus metaplasia. This protective effect was accompanied by reduced virus-driven lung IL-33, which is necessary to induce chronic asthmatic phenotype. Interestingly, Pam2-ODN does not induce increased production of Type I or III Interferons (IFN), nor does the protective response require intact interferon signaling. Transcriptome profiling of the mouse lungs in the chronic phase of infection led to identification of genes involved in airway remodelling, epithelial cell differentiation and chemokine signalling. More importantly, we identified genes from the Pam2-ODN treatment group that are involved in reversing the viral infection effect on day 49. Taken together, our findings reveal novel type I IFN independent mechanisms to prevent virus-induced asthma, and may provide an opportunity to protect vulnerable populations.

Pneumonia is a serious problem worldwide. We recently demonstrated that innate defense mechanisms of the lung are highly inducible against pneumococcal pneumonia. To determine the breadth of protection conferred by stimulation of lung mucosal innate immunity, and to identify cells and signaling pathways activated by this treatment, mice were treated with an aerosolized bacterial lysate, then challenged with lethal doses of bacterial and fungal pathogens. Mice were highly protected against a broad array of Gram-positive, Gram-negative, and class A bioterror bacterial pathogens, and the fungal pathogen, Aspergillus fumigatus. Protection was associated with rapid pathogen killing within the lungs, and this effect was recapitulated in vitro using a respiratory epithelial cell line. Gene expression analysis of lung tissue showed marked activation of NF-kappaB, type I and II IFN, and antifungal Card9-Bcl10-Malt1 pathways. Cytokines were the most strongly induced genes, but the inflammatory cytokines TNF and IL-6 were not required for protection. Lung-expressed antimicrobial peptides were also highly up-regulated. Taken together, stimulated innate resistance appears to occur through the activation of multiple host defense signaling pathways in lung epithelial cells, inducing rapid pathogen killing, and conferring broad protection against virulent bacterial and fungal pathogens. Augmentation of innate antimicrobial defenses of the lungs might have therapeutic value for protection of patients with neutropenia or impaired adaptive immunity against opportunistic pneumonia, and for defense of immunocompetent subjects against a bioterror threat or epidemic respiratory infection.

Nontypeable Haemophilus influenzae (NTHi) commonly colonizes the lower airways of patients with chronic obstructive pulmonary disease (COPD). Whether it contributes to COPD progression is unknown. Here, we determined which aspects of the COPD phenotype can be induced by repetitive exposure to NTHi products. Mice were exposed weekly to an aerosolized NTHi lysate, and inflammation was evaluated by measurement of cells and cytokines in bronchoalveolar lavage fluid (BALF) and immunohistochemical staining; structural changes were evaluated histochemically by periodic acid fluorescent Schiff's reagent, Masson's trichrome, and Picrosirius red staining; mucin gene expression was measured by quantitative RT-PCR; and the role of TNF-alpha was examined by transgenic airway overexpression and use of an inhibitory antibody. NTHi lysate induced rapid activation of NF-kappaB in airway cells and increases of inflammatory cytokines and neutrophils in BALF. Repetitive exposure induced infiltration of macrophages, CD8+ T cells, and B cells around airways and blood vessels, and collagen deposition in airway and alveolar walls, but airway mucin staining and gel-forming mucin transcripts were not increased. Transgenic overexpression of TNF-alpha caused BALF neutrophilia and inflammatory cell infiltration around airways, but not fibrosis, and TNF-alpha neutralization did not reduce BALF neutrophilia in response to NTHi lysate. In conclusion, NTHi products elicit airway inflammation in mice with a cellular and cytokine profile similar to that in COPD, and cause airway wall fibrosis but not mucous metaplasia. TNF-alpha is neither required for inflammatory cell recruitment nor sufficient for airway fibrosis. Colonization by NTHi may contribute to the pathogenesis of small airways disease in patients with COPD.

In asthma, airflow obstruction is thought to result primarily from inflammation-triggered airway smooth muscle (ASM) contraction. However, anti-inflammatory and smooth muscle-relaxing treatments are often temporary or ineffective. Overproduction of the mucin MUC5AC is an additional disease feature that, while strongly associated pathologically, is poorly understood functionally. Here we show that Muc5ac is a central effector of allergic inflammation that is required for airway hyperreactivity (AHR) to methacholine (MCh). In mice bred on two well-characterized strain backgrounds (C57BL/6 and BALB/c) and exposed to two separate allergic stimuli (ovalbumin and Aspergillus extract), genetic removal of Muc5ac abolishes AHR. Residual MCh responses are identical to unchallenged controls, and although inflammation remains intact, heterogeneous mucous occlusion decreases by 74%. Thus, whereas inflammatory effects on ASM alone are insufficient for AHR, Muc5ac-mediated plugging is an essential mechanism. Inhibiting MUC5AC may be effective for treating asthma and other lung diseases where it is also overproduced.

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

Synaptotagmins (Syts) I and II are believed to act as Ca2+ sensors in the control of neurotransmission. Here we demonstrate that mast cells express Syt II in their lysosomal fraction. We further show that activation of mast cells by either aggregation of FcεRI or by Ca2+ ionophores results in exocytosis of lysosomes, in addition to the well documented exocytosis of their secretory granules. Syt II directly regulates lysosomal exocytosis, whereby overexpression of Syt II inhibited Ca2+-triggered release of the lysosomal processed form of cathepsin D, whereas suppression of Syt II expression markedly potentiated this release. These findings provide evidence for a novel function of Syt II in negatively regulating Ca2+-triggered exocytosis of lysosomes, and suggest that Syt II–regulated secretion from lysosomes may play an important role in mast cell biology.

Procalcitonin (PCT) is expressed in nonthryoidal tissues of humans during severe infections. Serum PCT levels are measured to diagnose and guide therapy, and there is some evidence that PCT may also contribute to the pathogenesis of sepsis. We tested whether disruption of the gene encoding PCT in mice affected the course of sepsis. Mice with exons 2–5 of the gene encoding calcitonin/calcitonin gene–related polypeptide α (Calca) knocked out and congenic C57BL/6J control mice were challenged with aerosolized Streptococcus pneumoniae or Pseudomonas aeruginosa, or injected intraperitoneally with S. pneumoniae. There were no significant differences in the survival of knockout and control mice in the two pneumonia models, and no significant differences in weight loss, splenic bacterial counts, or blood leukocyte levels in the peritoneal sepsis model. To verify disruption of the Calca gene in knockout mice, the absence of calcitonin in the serum of knockout mice and its presence and inducibility in control mice were confirmed. To evaluate PCT expression in nonthyroidal tissues of control mice, transcripts were measured in multiple organs. PCT transcripts were not significantly expressed in liver or spleen of control mice challenged with aerosolized P. aeruginosa or intraperitoneal endotoxin, and were expressed in lung only at low levels, even though serum IL-6 rose 3,548-fold. We conclude that mice are not an ideal loss-of-function model to test the role of PCT in the pathogenesis of sepsis because of low nonendocrine PCT expression during infection and inflammation. Nonetheless, our studies demonstrate that nonendocrine PCT expression is not necessary for adverse outcomes from sepsis.

β(2)-Adrenoceptor (β2AR) agonists are the most effective class of bronchodilators and a mainstay of asthma management. The first potent β2AR agonist discovered and widely used in reversing the airway constriction associated with asthma exacerbation was the endogenous activator of the β2AR, epinephrine. In this study, we demonstrate that activation of the β2AR by epinephrine is paradoxically required for development of the asthma phenotype. In an antigen-driven model, mice sensitized and challenged with ovalbumin showed marked elevations in three cardinal features of the asthma phenotype: inflammatory cells in their bronchoalveolar lavage fluid, mucin over production, and airway hyperresponsiveness. However, genetic depletion of epinephrine using mice lacking the enzyme to synthesize epinephrine, phenylethanolamine N-methyltransferase, or mice that had undergone pharmacological sympathectomy with reserpine to deplete epinephrine, had complete attenuation of these three cardinal features of the asthma phenotype. Furthermore, administration of the long-acting β2AR agonist, formoterol, a drug currently used in asthma treatment, to phenylethanolamine N-methyltransferase-null mice restored the asthma phenotype. We conclude that β2AR agonist-induced activation is needed for pathogenesis of the asthma phenotype. These findings also rule out constitutive signaling by the β2AR as sufficient to drive the asthma phenotype, and may help explain why chronic administration of β2AR agonists, such as formoterol, have been associated with adverse outcomes in asthma. These data further support the hypothesis that chronic asthma management may be better served by treatment with certain "β-blockers."

Infectious pneumonias exact an unacceptable mortality burden worldwide. Efforts to protect populations from pneumonia have focused historically on antibiotic development and vaccine-enhanced adaptive immunity. However, we have reported recently that the lungs’ innate defenses can be induced therapeutically by inhalation of a bacterial lysate that protects mice against otherwise lethal pneumonia. In this study, we tested in mice the hypothesis that TLRs are required for this antimicrobial phenomenon and found that resistance could not be induced in the absence of the TLR signaling adaptor protein MyD88. We then attempted to recapitulate the protection afforded by the bacterial lysate by stimulating the lung epithelium with aerosolized synthetic TLR ligands. Although most single or combination treatments yielded no protection, simultaneous treatment with ligands for TLR2/6 and TLR9 conferred robust, synergistic protection against virulent Gram-positive and Gram-negative pathogens. Protection was associated with rapid pathogen killing in the lungs, and pathogen killing could be induced from lung epithelial cells in isolation. Taken together, these data demonstrate the requirement for TLRs in inducible resistance against pneumonia, reveal a remarkable, unanticipated synergistic interaction of TLR2/6 and TLR9, reinforce the emerging evidence supporting the antimicrobial capacity of the lung epithelium, and may provide the basis for a novel clinical therapeutic that can protect patients against pneumonia during periods of peak vulnerability.

Background Lower respiratory tract infections continue to exact unacceptable worldwide mortality, often because the infecting pathogen cannot be identified. The respiratory epithelia provide protection from pneumonias through organism-specific generation of antimicrobial products, offering potential insight into the identity of infecting pathogens. This study assesses the capacity of the host gene expression response to infection to predict the presence and identity of lower respiratory pathogens without reliance on culture data. Methods Mice were inhalationally challenged with S. pneumoniae, P. aeruginosa, A. fumigatus or saline prior to whole genome gene expression microarray analysis of their pulmonary parenchyma. Characteristic gene expression patterns for each condition were identified, allowing the derivation of prediction rules for each pathogen. After confirming the predictive capacity of gene expression data in blinded challenges, a computerized algorithm was devised to predict the infectious conditions of subsequent subjects. Results We observed robust, pathogen-specific gene expression patterns as early as 2 h after infection. Use of an algorithmic decision tree revealed 94.4% diagnostic accuracy when discerning the presence of bacterial infection. The model subsequently differentiated between bacterial pathogens with 71.4% accuracy and between non-bacterial conditions with 70.0% accuracy, both far exceeding the expected diagnostic yield of standard culture-based bronchoscopy with bronchoalveolar lavage. Conclusions These data substantiate the specificity of the pulmonary innate immune response and support the feasibility of a gene expression-based clinical tool for pneumonia diagnosis.

Recent studies have demonstrated that K-ras mutations in lung epithelial cells elicit inflammation that promotes carcinogenesis in mice (intrinsic inflammation). The finding that patients with chronic obstructive pulmonary disease (COPD), an inflammatory disease of the lung, have an increased risk of lung cancer after controlling for smoking suggests a further link between lung cancer and extrinsic inflammation. Besides exposure to cigarette smoke, it is thought that airway inflammation in COPD is caused by bacterial colonization, particularly with non-typeable Hemophilus influenzae (NTHi). Previously, we have shown that NTHi-induced COPD-like airway inflammation promotes lung cancer in an airway conditional K-ras-induced mouse model. To further test the role of inflammation in cancer promotion, we administered the natural anti-inflammatory agent, curcumin, 1% in diet before and during weekly NTHi exposure. This significantly reduced the number of visible lung tumors in the absence of NTHi exposure by 85% and in the presence of NTHi exposures by 53%. Mechanistically, curcumin markedly suppressed NTHi-induced increased levels of the neutrophil chemoattractant keratinocyte-derived chemokine by 80% and neutrophils by 87% in bronchoalveolar lavage fluid. In vitro studies of murine K-ras-induced lung adenocarcinoma cell lines (LKR-10 and LKR-13) indicated direct anti-tumoral effects of curcumin by reducing cell viability, colony formation and inducing apoptosis. We conclude that curcumin suppresses the progression of K-ras-induced lung cancer in mice by inhibiting intrinsic and extrinsic inflammation and by direct anti-tumoral effects. These findings suggest that curcumin could be used to protract the premalignant phase and inhibit lung cancer progression in high-risk COPD patients.

Background Protective host responses to respiratory pathogens are typically characterized by inflammation. However, lung inflammation is not always protective and it may even become deleterious to the host. We have recently reported substantial protection against Streptococcus pneumoniae (pneumococcal) pneumonia by induction of a robust inflammatory innate immune response to an inhaled bacterial lysate. Conversely, the allergic inflammation associated with asthma has been proposed to promote susceptibility to pneumococcal disease. This study sought to determine whether preexisting allergic lung inflammation influences the progression of pneumococcal pneumonia or reduces the inducibilty of protective innate immunity against bacteria. Methods To compare the effect of different inflammatory and secretory stimuli on defense against pneumonia, intraperitoneally ovalbumin-sensitized mice were challenged with inhaled pneumococci following exposure to various inhaled combinations of ovalbumin, ATP, and/or a bacterial lysate. Thus, allergic inflammation, mucin degranulation and/or stimulated innate resistance were induced prior to the infectious challenge. Pathogen killing was evaluated by assessing bacterial CFUs of lung homogenates immediately after infection, the inflammatory response to the different conditions was evaluated by measurement of cell counts of bronchoalveolar lavage fluid 18 hours after challenge, and mouse survival was assessed after seven days. Results We found no differences in survival of mice with and without allergic inflammation, nor did the induction of mucin degranulation alter survival. As we have found previously, mice treated with the bacterial lysate demonstrated substantially increased survival at seven days, and this was not altered by the presence of allergic inflammation or mucin degranulation. Allergic inflammation was associated with predominantly eosinophilic infiltration, whereas the lysate-induced response was primarily neutrophilic. The presence of allergic inflammation did not significantly alter the neutrophilic response to the lysate, and did not affect the induced bacterial killing within the lungs. Conclusion These results suggest that allergic airway inflammation neither promotes nor inhibits progression of pneumococcal lung infection in mice, nor does it influence the successful induction of stimulated innate resistance to bacteria.

Chronic regular use of β 2 -adrenoceptor (β 2 -AR) agonists in asthma is associated with a loss of disease control and increased risk of death. Conversely, we have found that administration of β 2 -AR inverse agonists results in attenuation of the asthma phenotype in an allergen-driven murine model. Besides antagonizing agonist-induced signaling and reducing signaling by empty receptors, β-AR inverse agonists can also activate signaling by novel pathways. To determine the mechanism of the β-AR inverse agonists, we compared the asthma phenotype in β 2 -AR-null and wild-type mice. Antigen challenge of β 2 -AR-null mice produced results similar to what was observed with chronic β 2 -AR inverse agonist treatment, namely, reductions in mucous metaplasia, airway hyperresponsiveness (AHR), and inflammatory cells in the lungs. These results indicate that the effects of β 2 -AR inverse agonists are caused by inhibition of β 2 -AR signaling rather than by the induction of novel signaling pathways. Chronic administration of alprenolol, a β-blocker without inverse agonist properties, did not attenuate the asthma phenotype, suggesting that it is signaling by empty receptors, rather than agonist-induced β 2 -AR signaling, that supports the asthma phenotype. In conclusion, our results demonstrate that, in a murine model of asthma, β 2 -AR signaling is required for the full development of three cardinal features of asthma: mucous metaplasia, AHR, and the presence of inflammatory cells in the lungs.

Background Influenza pneumonia causes high mortality every year, and pandemic episodes kill millions of people. Influenza-related mortality has been variously ascribed to an ineffective host response that fails to limit viral replication, an excessive host inflammatory response that results in lung injury and impairment of gas exchange, or to bacterial superinfection. We sought to determine whether lung inflammation promoted or impaired host survival in influenza pneumonia. Methods and Findings To distinguish among these possible causes of influenza-related death, we induced robust lung inflammation by exposing mice to an aerosolized bacterial lysate prior to challenge with live virus. The treatment induced expression of the inflammatory cytokines IL-6 and TNF in bronchoalveolar lavage fluid 8- and 40-fold greater, respectively, than that caused by lethal influenza infection. Yet, this augmented inflammation was associated with striking resistance to host mortality (0% vs 90% survival, p = 0.0001) and reduced viral titers (p = 0.004). Bacterial superinfection of virus infected lungs was not observed. When mice were repeatedly exposed to the bacterial lysate, as would be clinically desirable during an influenza epidemic, there was no tachyphylaxis of the induced viral resistance. When the bacterial lysate was administered after the viral challenge, there was still some mortality benefit, and when ribavirin was added to the aerosolized bacterial lysate, host survival was synergistically improved (0% vs 93.3% survival, p

Airway mucus plugging has long been recognized as a principal cause of death in asthma. However, molecular mechanisms of mucin overproduction and secretion have not been understood until recently. These mechanisms are reviewed together with ongoing investigations relating them to lung pathophysiology.Of the five secreted gel-forming mucins in mammals, only MUC5AC and MUC5B are produced in significant quantities in intrapulmonary airways. MUC5B is the principal gel-forming mucin at baseline in small airways of humans and mice, and therefore likely performs most homeostatic clearance functions. MUC5AC is the principal gel-forming mucin upregulated in airway inflammation and is under negative control by forkhead box a2 (Foxa2) and positive control by hypoxia inducible factor-1 (HIF-1). Mucin secretion is regulated separately from production, principally by extracellular triphosphate nucleotides that bind P2Y2 receptors on the lumenal surface of airway secretory cells, generating intracellular second messengers that activate the exocytic proteins, Munc13-2 and synaptotagmin-2.Markedly upregulated production of MUC5AC together with stimulated secretion leads to airflow obstruction in asthma. As MUC5B appears to mediate homeostatic functions, it may be possible to selectively inhibit MUC5AC production without impairing airway function. The precise roles of mucin hypersecretion in asthma symptoms such as dyspnea and cough and in physiologic phenomena such as airway hyperresponsiveness remain to be defined.

Inhalational anthrax is initiated by the entry of Bacillus anthracis spores into the lung. A critical early event in the establishment of an infection is the dissemination of spores from the lung. Using in vitro cell culture assays, we previously demonstrated that B. anthracis spores are capable of entering into epithelial cells of the lung and crossing a barrier of lung epithelial cells without apparent disruption of the barrier integrity, suggesting a novel portal for spores to disseminate from the lung. However, in vivo evidence for spore uptake by epithelial cells has been lacking. Here, using a mouse model, we present evidence that B. anthracis spores are taken up by lung epithelial cells in vivo soon after spores are delivered into the lung. Immunofluorescence staining of thin sections of lungs from spore-challenged BALB/c mice revealed that spores were associated with the epithelial surfaces in the airway and the alveoli at 2 and 4 h postinoculation. Confocal analysis further indicated that some of the associated spores were surrounded by F-actin, demonstrating intracellular localization. These observations were further confirmed and substantiated by a quantitative method that first isolated lung cells from spore-challenged mice and then stained these cells with antibodies specific for epithelial cells and spores. The results showed that substantial amounts of spores were taken up by lung epithelial cells in vivo. These data, combined with those in our previous reports, provided powerful evidence that the lung epithelia were directly targeted by B. anthracis spores at early stages of infection.

The lungs are a common site of serious infection in both healthy and immunocompromised subjects, and the most likely route of delivery of a bioterror agent. Since the airway epithelium shows great structural plasticity in response to inflammatory stimuli, we hypothesized it might also show functional plasticity.To test the inducibility of lung defenses against bacterial challenge.Mice were treated with an aerosolized lysate of ultraviolet-killed nontypeable (unencapsulated) Haemophilus influenzae (NTHi), then challenged with a lethal dose of live Streptococcus pneumoniae (Spn) delivered by aerosol.Treatment with the NTHi lysate induced complete protection against challenge with a lethal dose of Spn if treatment preceded challenge by 4 to 24 hours. Lesser levels of protection occurred at shorter (83% at 2 h) and longer (83% at 48-72 h) intervals between treatment and challenge. There was also some protection when treatment was given 2 hours after challenge (survival increased from 14 to 57%), but not 24 hours after challenge. Protection did not depend on recruited neutrophils or resident mast cells and alveolar macrophages. Protection was specific to the airway route of infection, correlated in magnitude and time with rapid bacterial killing within the lungs, and was associated with increases of multiple antimicrobial polypeptides in lung lining fluid.We infer that protection derives from stimulation of local innate immune mechanisms, and that activated lung epithelium is the most likely cellular effector of this response. Augmentation of innate antimicrobial defenses of the lungs might have therapeutic value.

Single-dose administration of beta-adrenoceptor agonists produces bronchodilation and inhibits airway hyperresponsiveness (AHR), and is the standard treatment for the acute relief of asthma. However, chronic repetitive administration of beta-adrenoceptor agonists may increase AHR, airway inflammation, and risk of death. Based upon the paradigm shift that occurred with the use of beta-blockers in congestive heart failure, we previously determined that chronic administration of beta-blockers decreased AHR in a murine model of asthma. To elucidate the mechanisms for the beneficial effects of beta-blockers, we examined the effects of chronic administration of several beta-adrenoceptor ligands in a murine model of allergic asthma. Administration of beta-blockers resulted in a reduction in total cell counts, eosinophils, and the cytokines IL-13, IL-10, IL-5, and TGF-beta1 in bronchoalveolar lavage, and attenuated epithelial mucin content and morphologic changes. The differences in mucin content also occurred if the beta-blockers were administered only during the ovalbumin challenge phase, but administration of beta-blockers for 7 days was not as effective as administration for 28 days. These results indicate that in a murine model of asthma, chronic administration of beta-blockers reduces inflammation and mucous metaplasia, cardinal features of asthma that may contribute to airflow obstruction and AHR. Similar to heart failure, our results provide a second disease model in which beta-blockers producing an acutely detrimental effect may provide a therapeutically beneficial effect with chronic administration.

Airway mucus hypersecretion is a prominent feature of many obstructive lung diseases. We thus determined the ontogeny and exocytic phenotype of mouse airway mucous cells. In naive mice, ciliated (approximately 40%) and nonciliated (approximately 60%) epithelial cells line the airways, and > 95% of the nonciliated cells are Clara cells that contain Clara cell secretory protein (CCSP). Mucous cells comprise < 5% of the nonciliated cells. After sensitization and a single aerosol antigen challenge, alcian blue-periodic acid Schiff's positive mucous cell numbers increase dramatically, appearing 6 h after challenge (21% of nonciliated/nonbasal cells), peaking from Days 1-7 (99%), and persisting at Day 28 (65%). Throughout the induction and resolution of mucous metaplasia, ciliated and Clara cell numbers identified immunohistochemically change only slightly. Intracellular mucin content peaks at Day 7, and mucin expression is limited specifically to a Clara cell subset in airway generations 2-4 that continue to express CCSP. Functionally, Clara cells are secretory cells that express the regulated exocytic marker Rab3D and, in antigen-challenged mice, rapidly secrete mucin in response to inhaled ATP in a dose-dependent manner. Thus, Clara cells show great plasticity in structure and secretory products, yet have molecular and functional continuity in their identity as specialized apical secretory cells.