Augmented lung inflammation protects against influenza A pneumonia

The RNA receptor RIG-I binding synthetic oligodeoxynucleotide promotes pneumonia survival

Pneumonia is a worldwide threat to public health, demanding novel preventative and therapeutic strategies. The lung epithelium is a critical environmental interface that functions as a physical barrier to pathogen invasion while also actively sensing and responding to pathogens. We have reported that stimulating lung epithelial cells with a combination therapeutic consisting of a diacylated lipopeptide and a synthetic CpG oligodeoxynucleotide (ODN) induces synergistic pneumonia protection against a wide range of pathogens. We report here that mice deficient in TLR9, the previously described receptor for ODN, still displayed partial ODN-induced protection. This prompted us to seek an alternate ODN receptor, and we discovered by mass spectroscopy that the RNA sensor RIG-I could also bind DNA-like ODN. ODN binding by RIG-I resulted in MAVS-dependent pneumonia-protective signaling events. While RIG-I is essential to native defenses against viral infections, we report that therapeutic RIG-I activation with ODN promoted pathogen killing and host survival following both viral and bacterial challenges. These data indicate that maximal ODN-induced pneumonia protection requires activation of both the TLR9/MyD88 and RIG-I/MAVS signaling pathways. These findings not only identify what we believe to be a novel pattern recognition receptor for DNA-like molecules, but reveal a potential therapeutic strategy to protect susceptible individuals against lethal pneumonias during periods of peak vulnerability.

Oral Cavity Microbiome Impact on Respiratory Infections Among Children

Background

The respiratory system, traditionally considered antiseptic, harbors a diverse and dynamic bacterial microbiome. Recent advancements in microbiome research have revealed its significant influence on both innate and adaptive immunity, particularly in the context of respiratory infections in children. This article also provides an overview of the types of bacteria that commonly affect the respiratory system, including Streptococcus pneumoniae, Moraxella catarrhalis and Haemophilus influenzae. These bacteria are prevalent in pediatric populations and significantly contribute to the development and severity of respiratory tract infections (RTIs).

Purpose

This review aims to evaluate the impact of the oral cavity and upper respiratory microbiome on the susceptibility and severity of respiratory infections in pediatric populations. We specifically focus on how early colonization patterns of bacteria such as Moraxella and Streptococcus contribute to the development of respiratory tract infections in children from birth through adolescence.

Methods

A thorough literature review was performed, focusing on studies publishing between 2004 and 2023. The review included research exploring the role of the upper respiratory microbiome in pediatric populations, with a specific focus on children aged birth to 18 years. Emphasis was placed on microbial characterization, the modulation of immune responses in respiratory tract infections, and the potential therapeutic applications of microbiome-targeted interventions.

Results

The findings suggest that the composition and disruption of the upper respiratory microbiome significantly influence clinical outcomes in children with respiratory infections. Notably, dysbiosis in the microbiome has been linked to increased susceptibility to repeated infections, highlighting the importance of maintaining microbial balance for optimal respiratory health.

Conclusion

Understanding the impact of oral cavity and upper respiratory microbiome could lead to improved management and prevention strategies for respiratory infections in children. This review underscores the potential of microbiome modulation, including the use of probiotics as a therapeutic approach to enhance clinical outcomes in pediatric respiratory infections.

Pertussis toxin-dependent and -independent protection by Bordetella pertussis against influenza

Bacterial-viral co-infections are frequent, but their reciprocal effects are not well understood. Here, we examined the effect Bordetella pertussis infection and the role of pertussis toxin (PT) on influenza A virus (IAV) infection and disease. In C57BL/6J mice, prior nasal administration of virulent B. pertussis BPSM and PT-deficient BPRA provided effective and sustained protection from IAV-induced mortality. However, BPSM or BPRA administered together with purified PT (BPRA + PT) had a stronger protective effect on weight loss compared to BPRA alone, reduced the viral load, and induced IL-17A in the lungs. In IL-17-/- mice, BPSM- and BPRA + PT-mediated protection against viral replication was abolished, while BPSM, BPRA and BPRA + PT provided similar levels of protection against IAV-induced mortality and weight loss. In conclusion, B. pertussis infection protects against influenza by two mechanisms: one reducing viral replication depending on PT and IL-17, and the other, independently of PT and IL-17, resulting in protection against influenza disease without reducing the viral load.

Protective interplay: Mycobacterium tuberculosis diminishes SARS-CoV-2 severity through innate immune priming

At the beginning of the COVID-19 pandemic those with underlying chronic lung conditions, including tuberculosis (TB), were hypothesized to be at higher risk of severe COVID-19 disease. However, there is inconclusive clinical and preclinical data to confirm the specific risk SARS-CoV-2 poses for the millions of individuals infected with Mycobacterium tuberculosis (M.tb). We and others have found that compared to singly infected mice, mice co-infected with M.tb and SARS-CoV-2 leads to reduced SARS-CoV-2 severity compared to mice infected with SARS-CoV-2 alone. Consequently, there is a large interest in identifying the molecular mechanisms responsible for the reduced SARS-CoV-2 infection severity observed in M.tb and SARS-CoV-2 co-infection. To address this, we conducted a comprehensive characterization of a co-infection model and performed mechanistic in vitro modeling to dynamically assess how the innate immune response induced by M.tb restricts viral replication. Our study has successfully identified several cytokines that induce the upregulation of anti-viral genes in lung epithelial cells, thereby providing protection prior to challenge with SARS-CoV-2. In conclusion, our study offers a comprehensive understanding of the key pathways induced by an existing bacterial infection that effectively restricts SARS-CoV-2 activity and identifies candidate therapeutic targets for SARS-CoV-2 infection.

Advances in Bacterial Lysate Immunotherapy for Infectious Diseases and Cancer

Antigenic cell fragments, pathogen-associated molecular patterns, and other immunostimulants in bacterial lysates or extracts may induce local and systemic immune responses in specific and nonspecific paradigms. Based on current knowledge, this review aimed to determine whether bacterial lysate has comparable functions in infectious diseases and cancer treatment. In infectious diseases, including respiratory and urinary tract infections, immune system activation by bacterial lysate can identify and combat pathogens. Commercially available bacterial lysates, including OM-85, Ismigen, Lantigen B, and LW 50020, were effective in children and adults in treating respiratory tract infections, chronic obstructive pulmonary disease, rhinitis, and rhinosinusitis with varying degrees of success. Moreover, OM-89, Uromune, Urovac, Urivac, and ExPEC4V showed therapeutic benefits in controlling urinary tract infections in adults, especially women. Bacterial lysate-based therapeutics are safe, well-tolerated, and have few side effects, making them a good alternative for infectious disease management. Furthermore, a nonspecific immunomodulation by bacterial lysates may stimulate innate immunity, benefiting cancer treatment. "Coley's vaccine" has been used to treat sarcomas, carcinomas, lymphomas, melanomas, and myelomas with varying outcomes. Later, several similar bacterial lysate-based therapeutics have been developed to treat cancers, including bladder cancer, non-small cell lung cancer, and myeloma; among them, BCG for in situ bladder cancer is well-known. Proinflammatory cytokines, including IL-1, IL-6, IL-12, and TNF-α, may activate bacterial antigen-specific adaptive responses that could restore tumor antigen recognition and response by tumor-specific type 1 helper cells and cytotoxic T cells; therefore, bacterial lysates are worth investigating as a vaccination adjuvants or add-on therapies for several cancers.

Epithelial immunomodulation by aerosolized Toll-like receptor agonists prevents allergic inflammation in airway mucosa in mice

Allergic asthma is a chronic inflammatory respiratory disease associated with eosinophilic infiltration, increased mucus production, airway hyperresponsiveness, and airway remodeling. Epidemiologic data reveal 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 expression of myriad Toll-like receptors (TLRs) and other pattern-recognition receptors. 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 the lung, and reduces the likelihood of inappropriate sensitization to aeroallergens. Furthermore, Pam2 and ODN cooperated synergistically suggesting that this treatment is superior to any single agonist in the setting of allergen immunotherapy.

Active disease-related compound identification based on capsule network

Pneumonia, especially corona virus disease 2019 (COVID-19), can lead to serious acute lung injury, acute respiratory distress syndrome, multiple organ failure and even death. Thus it is an urgent task for developing high-efficiency, low-toxicity and targeted drugs according to pathogenesis of coronavirus. In this paper, a novel disease-related compound identification model-based capsule network (CapsNet) is proposed. According to pneumonia-related keywords, the prescriptions and active components related to the pharmacological mechanism of disease are collected and extracted in order to construct training set. The features of each component are extracted as the input layer of capsule network. CapsNet is trained and utilized to identify the pneumonia-related compounds in Qingre Jiedu injection. The experiment results show that CapsNet can identify disease-related compounds more accurately than SVM, RF, gcForest and forgeNet.

Trained immunity induction by the inactivated mucosal vaccine MV130 protects against experimental viral respiratory infections

MV130 is an inactivated polybacterial mucosal vaccine that confers protection to patients against recurrent respiratory infections, including those of viral etiology. However, its mechanism of action remains poorly understood. Here, we find that intranasal prophylaxis with MV130 modulates the lung immune landscape and provides long-term heterologous protection against viral respiratory infections in mice. Intranasal administration of MV130 provides protection against systemic candidiasis in wild-type and Rag1-deficient mice lacking functional lymphocytes, indicative of innate immune-mediated protection. Moreover, pharmacological inhibition of trained immunity with metformin abrogates the protection conferred by MV130 against influenza A virus respiratory infection. MV130 induces reprogramming of both mouse bone marrow progenitor cells and in vitro human monocytes, promoting an enhanced cytokine production that relies on a metabolic shift. Our results unveil that the mucosal administration of a fully inactivated bacterial vaccine provides protection against viral infections by a mechanism associated with the induction of trained immunity.

Enhancement of immune responses by co-stimulation of TLR3 - TLR7 agonists as a potential therapeutics against rabies in mouse model

Rabies is always fatal, when post-exposure prophylaxis is administered after the onset of clinical symptoms. To date, there is no effective treatment of rabies once clinical symptoms has initiated. Therefore, we aimed to provide evidences which indicate the promising effects of combination treatment with TLR agonists following rabies infection. Four groups of rabies infected-mice (10-mice/group) were treated with PolyI:C 50 μg (a TLR3 agonist), Imiquimod50 μg (a TLR7 agonist), (Poly + Imi)25 μg and (Poly + Imi)50 μg respectively. The immune responses in each experimental groups were investigated in the brain through evaluation of GFAP, MAP2, CD4, HSP70, TLR3, TLR7 and apoptotic cell expression as well as determination of IFN-γ, TNF-α and IL-4, levels. The treatment with combination of agonists (Poly + Imi)50 μg/mouse resulted a 75% decrease of mortality rate and better extended survival time following street rabies virus infection. Higher number of CD4⁺T cells, TLR3 and TLR7 expression in the brain parenchyma observed in the groups receiving both combined agonist therapies at the levels of 25 μg and 50 μg. In spite of decreased number of neuronal cell, significant higher number of astrocytes was shown in the group given (Poly + Imi)25 μg. The obtained results also pointed to the dramatic decrease of HSP70 expression in all groups of infected mice whereas higher number of apoptotic cells and Caspase 8 expression were recorded in (Poly + Imi)25 μg treated group. Furthermore, the cytokine profile consisting the increased levels of TNF-α, IFN-γ and IL-4 revealed that both humoral and cellular responses were highly modulated in combination therapy of 50 μg of Imiquimod and Poly I:C. Reduced viral load as quantified by real-time PCR of rabies N gene expression in the brain also correlated with the better survival of agonist-treated groups of mice. Based on obtained results, we have presented evidences of beneficial utilization of combined agonist therapy composed of TLR3/TLR7 ligands. This treatment regimen extended survival of infected mice and decreased significantly their mortality rate. We believe that the results of synergy-inducing protection of both TLR3/TLR7 agonists lead to the enhancement of innate immune responses cells residing in the CNS which warrant the studies to further understanding of crosstalk mechanisms in cellular immunity against rabies in the future.

Topical Microbial Therapeutics against Respiratory Viral Infections

Emerging evidence suggests that microbial therapeutics can prevent and treat respiratory viral diseases, especially when applied directly to the airways. This review presents established beneficial effects of locally administered microbial therapeutics against respiratory viral diseases and the inferred related molecular mechanisms. Several mechanisms established in the intestinal probiotics field as well as novel, niche-specific insights are relevant in the airways. Studies at cellular and organism levels highlight biologically plausible but strain-specific and host and virus context-dependent mechanisms, underlying the potential of beneficial bacteria. Large-scale clinical studies can now be rationally designed to provide a bench-to-bedside translation of the multifactorial bacterial mechanisms within the host respiratory tract, to diminish the incidence and severity of viral infections and the concomitant complications.

How to Train Your Dragon: Harnessing Gamma Delta T Cells Antiviral Functions and Trained Immunity in a Pandemic Era

The emergence of viruses with pandemic potential such as the SARS-CoV-2 coronavirus causing COVID-19 poses a global health challenge. There is remarkable progress in vaccine technology in response to this threat, but their design often overlooks the innate arm of immunity. Gamma Delta (γδ) T cells are a subset of T cells with unique features that gives them a key role in the innate immune response to a variety of homeostatic alterations, from cancer to microbial infections. In the context of viral infection, a growing body of evidence shows that γδ T cells are particularly equipped for early virus detection, which triggers their subsequent activation, expansion and the fast deployment of antiviral functions such as direct cytotoxic pathways, secretion of cytokines, recruitment and activation of other immune cells and mobilization of a trained immunity memory program. As such, γδ T cells represent an attractive target to stimulate for a rapid and effective resolution of viral infections. Here, we review the known aspects of γδ T cells that make them crucial component of the immune response to viruses, and the ways that their antiviral potential can be harnessed to prevent or treat viral infection.

Granulocyte macrophage colony-stimulating factor has come of age: From a vaccine adjuvant to antiviral immunotherapy

GM-CSF acts as a pro-inflammatory cytokine and a key growth factor produced by several immune cells such as macrophages and activated T cells. In this review, we discuss recent studies that point to the crucial role of GM-CSF in the immune response against infections. Upon induction, GM-CSF activates four main signalling networks including the JAK/STAT, PI3K, MAPK, and NFκB pathways. Many of these transduction pathways such as JAK/STAT signal via proteins commonly activated with other antiviral signalling cascades, such as those induced by IFNs. GM-CSF also helps defend against respiratory infections by regulating alveolar macrophage differentiation and enhancing innate immunity in the lungs. Here, we also summarize the numerous clinical trials that have taken advantage of GM-CSF's mechanistic attributes in immunotherapy. Moreover, we discuss how GM-CSF is used as an adjuvant in vaccines and how its activity is interfered with to reduce inflammation such as in the case of COVID-19. This review brings forth the current knowledge on the antiviral actions of GM-CSF, the associated signalling cascades, and its application in immunotherapy.

Covid-19: Perspectives on Innate Immune Evasion

The ongoing outbreak of Coronavirus disease 2019 infection achieved pandemic status on March 11, 2020. As of September 8, 2020 it has caused over 890,000 mortalities world-wide. Coronaviral infections are enabled by potent immunoevasory mechanisms that target multiple aspects of innate immunity, with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) able to induce a cytokine storm, impair interferon responses, and suppress antigen presentation on both MHC class I and class II. Understanding the immune responses to SARS-CoV-2 and its immunoevasion approaches will improve our understanding of pathogenesis, virus clearance, and contribute toward vaccine and immunotherepeutic design and evaluation. This review discusses the known host innate immune response and immune evasion mechanisms driving SARS-CoV-2 infection and pathophysiology.

Epithelial dysfunction, respiratory infections and asthma: the importance of immunomodulation. A focus on OM-85

INTRODUCTION

Damage to the respiratory epithelium, is often a multifactorial phenomenon. The risk for developing a damage in respiratory epithelium and recurrent respiratory infections may vary among individuals. Preventive measures are based on strengthening the immune function, thus increasing the natural response to pathogens. Immunomodulatory agents are: i. synthetic molecules; ii. Probiotics, prebiotics, symbiotics; iii. Lysates, bacterial extracts immunomodulators: OM-85, RU 41740, D53; iv. Trace elements, vitamins. OM-85 is used for the prevention of recurrent respiratory tract infections and/or exacerbations both in adults and children, showing a good efficacy and safety profile. Its active principle, an extract of bacterial lysates isolated from 21 known respiratory pathogenic strains, shows protection against airway infections of bacterial and viral origin.

AREAS COVERED

This non-systematic review focuses on bacterial lysates and in particular on OM-85 and its effects on respiratory epithelium function and activity in asthma respiratory infections. Studies were selected by PubMed search of "bacterial lysate" or "OM-85" and "respiratory epithelium" or "respiratory infections", from 1993 to 2019.

EXPERT OPINION

Results highlight the ability of OM-85 to trigger immunomodulatory and protective immune responses against different pathogens in vivo, including influenza and respiratory syncytial virus as well bacterial superinfection following influenza.

A new perspective for mitigation of SARS-CoV-2 infection: priming the innate immune system for viral attack

The course of infection by SARS-CoV-2 frequently includes a long asymptomatic period, followed in some individuals by an immune dysregulation period that may lead to complications and immunopathology-induced death. This course of disease suggests that the virus often evades detection by the innate immune system. We suggest a novel therapeutic approach to mitigate the infection's severity, probability of complications and duration. We propose that priming an individual's innate immune system for viral attack shortly before it is expected to occur may allow pre-activation of the preferable trajectory of immune response, leading to early detection of the virus. Priming can be carried out, for example, by administering a standard vaccine or another reagent that elicits a broad anti-viral innate immune response. By the time that the expected SARS-CoV-2 infection occurs, activation cascades will have been put in motion and levels of immune factors needed to combat the infection will have been elevated. The infection would thus be cleared faster and with less complication than otherwise, alleviating adverse clinical outcomes at the individual level. Moreover, priming may also mitigate population-level risk by reducing need for hospitalizations and decreasing the infectious period of individuals, thus slowing the spread and reducing the impact of the epidemic. In view of the latter consideration, our proposal may have a significant epidemiological impact even if applied primarily to low-risk individuals, such as young adults, who often show mild symptoms or none, by shortening the period during which they unknowingly infect others. The proposed view is, at this time, an unproven hypothesis. Although supported by robust bio-medical reasoning and multiple lines of evidence, carefully designed clinical trials are necessary.

Pulmonary and systemic responses to aerosolized lysate of Staphylococcus aureus and Escherichia coli in calves

Background

Constitutive and inducible defenses protect the respiratory tract from bacterial infection. The objective of this study was to characterize the response to an aerosolized lysate of killed bacteria, as a basis for studying the regulation and in vivo effects of these inducible innate immune responses.

Results

Bacterial lysate consisting of heat-killed and sonicated Staphylococcus aureus and Escherichia coli was aerosolized to 6 calves and systemic and pulmonary innate immune and inflammatory responses were measured in the first 24 h relative to baseline. Evaluated parameters included clinical parameters (body temperature and heart and respiratory rates), blood acute phase proteins and leukocyte counts, and leukocytes and proteins in bronchoalveolar lavage fluid. Mild clinical signs with increased heart rates and rectal temperatures developed following administration of the lysate, with resolution by 24 h. Serum haptoglobin and plasma fibrinogen concentrations were elevated at 24 h relative to baseline. Bronchoalveolar lavage fluid (BALF) had increased cellularity and increased proportion of neutrophils, as well as higher concentrations of interleukin (IL)-8, IL-10 and total protein at 24 h relative to baseline. Mass spectrometry identified 965 unique proteins in BALF: 19 proteins were increased and 26 proteins were decreased relative to baseline. The upregulated proteins included those involved in innate immunity including activation of complement, neutrophils and platelets. At postmortem examination, calves receiving higher doses of lysate had areas of lobular consolidation and interlobular edema. Histologically, neutrophils were present within bronchioles and to a lesser extent within alveoli. Calves receiving highest doses of lysate had patchy areas of neutrophils, hemorrhage and hyaline membranes within alveoli.

Conclusions

Aerosolization of bacterial lysate stimulated an innate immune response in lungs and airways, with alveolar damage observed at higher doses. Such a stimulus could be of value for investigating the effects of inducible innate immune responses on occurrence of disease, or for evaluating how stress, drugs or genetics affect these dynamic responses of the respiratory tract.

Inducible epithelial resistance against acute Sendai virus infection prevents chronic asthma-like lung disease in mice

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.

New therapeutic targets for the prevention of infectious acute exacerbations of COPD: role of epithelial adhesion molecules and inflammatory pathways

Chronic respiratory diseases are among the leading causes of mortality worldwide, with the major contributor, chronic obstructive pulmonary disease (COPD) accounting for approximately 3 million deaths annually. Frequent acute exacerbations (AEs) of COPD (AECOPD) drive clinical and functional decline in COPD and are associated with accelerated loss of lung function, increased mortality, decreased health-related quality of life and significant economic costs. Infections with a small subgroup of pathogens precipitate the majority of AEs and consequently constitute a significant comorbidity in COPD. However, current pharmacological interventions are ineffective in preventing infectious exacerbations and their treatment is compromised by the rapid development of antibiotic resistance. Thus, alternative preventative therapies need to be considered. Pathogen adherence to the pulmonary epithelium through host receptors is the prerequisite step for invasion and subsequent infection of surrounding structures. Thus, disruption of bacterial-host cell interactions with receptor antagonists or modulation of the ensuing inflammatory profile present attractive avenues for therapeutic development. This review explores key mediators of pathogen-host interactions that may offer new therapeutic targets with the potential to prevent viral/bacterial-mediated AECOPD. There are several conceptual and methodological hurdles hampering the development of new therapies that require further research and resolution.

Impact of the Respiratory Microbiome on Host Responses to Respiratory Viral Infection

Viruses are responsible for most of both upper and lower acute respiratory infections (ARIs). The microbiome—the ecological community of microorganisms sharing the body space, which has gained considerable interest over the last decade—is modified in health and disease states. Even if most of these disturbances have been previously described in relation to chronic disorders of the gastrointestinal microbiome, after a short reminder of microbiome characteristics and methods of characterization, this review will describe the impact of the microbiome (mainly respiratory) on host responses to viral ARIs. The microbiome has a direct environmental impact on the host cells but also an indirect impact on the immune system, by enhancing innate or adaptive immune responses. In microbial infections, especially in viral infections, these dramatic modifications could lead to a dramatic impact responsible for severe clinical outcomes. Studies focusing on the microbiome associated with transcriptomic analyses of the host response and deep characterization of the pathogen would lead to a better understanding of viral pathogenesis and open avenues for biomarker development and innovative therapeutics.

Chronic lung inflammation primes humoral immunity and augments antipneumococcal resistance

Airway epithelial cells (AECs) display remarkable plasticity in response to infectious stimuli and their functional adaptations are critical for antimicrobial immunity. However, the roles of AECs and humoral mediators to host defense in non-communicable lung inflammation remain elusive. We dissected pulmonary defense against Streptococcus pneumoniae in hosts with pre-existing inflammatory conditions (SPC-HAxTCR-HA mice). Lung tissue transcriptomics and bronchoalveolar lavage fluid (BALF) proteomics revealed an induction of humoral defense mechanisms in inflamed lungs. Accordingly, besides antibacterial proteins and complement components being overrepresented in inflamed lungs, elevated polymeric immunoglobulin receptor (pIgR)-expression in AECs correlated with increased secretory immunoglobulin (SIg) transport. Consequently, opsonization assays revealed augmented pneumococcal coverage by SIgs present in the BALF of SPC-HAxTCR-HA mice, which was associated with enhanced antipneumococcal resistance. These findings emphasize the immunologic potential of AECs as well as their central role in providing antibacterial protection and put forward pIgR as potential target for therapeutic manipulation in infection-prone individuals.

Administration of immunobiotic Lactobacillus plantarum delays but does not prevent lethal pneumovirus infection in Rag1-/- mice

Administration of immunobiotic Lactobacillus plantarum (Lp) directly to the respiratory mucosa promotes cross-protection against lethal pneumovirus infection via B-cell-independent mechanisms. In this study, we examined Lp-mediated cross protection in Rag1^-/- mice which cannot clear virus from lung tissue. Although Lp was initially protective, Rag1^-/- mice ultimately succumbed to a delayed lethal outcome associated with local production of the proinflammatory cytokines CCL1, -2, and -7, granulocyte recruitment, and ongoing virus replication. By contrast, CD8^null mice, which are fully capable of clearing virus, are protected by Lp with no delayed lethal outcome, granulocyte recruitment to the airways, or induction of CCL7. Repeated administration of Lp to virus-infected Rag1^-/- mice had no impact on delayed mortality. Moreover, administration of Lp to the respiratory mucosa resulted in no induction of IFN-α or -β in Rag1^-/- or wild-type mice, and IFN-abR gene deletion had no impact on Lp-mediated protection. Overall, our findings indicate that although Lp administered to the respiratory tract has substantial impact on lethal virus-induced inflammation in situ, endogenous virus clearance mechanisms are needed to promote sustained protection. Our results suggest that a larger understanding of the mechanisms and mediators that limit acute virus-induced inflammation may yield new and useful therapeutic modalities.

Do antiepileptic drugs increase the risk of infectious diseases? A meta-analysis of placebo-controlled studies

AIMS

Experimental studies show that some antiepileptic drugs (AEDs) may modify natural immune defences, thus influencing the risk of developing infectious diseases. The aim of this meta-analysis was to explore whether AEDs as a class of drugs or singularly may increase risk of infectious diseases.

METHODS

A meta-analysis of all randomized, double-blind, placebo-controlled trials (RCTs) investigating any AED in any condition was performed. All terms that could be coded in the System Organ Classes (SOCs) of infections and infestations using the Medical Dictionary for Regulatory Activities were recorded. Additional subanalyses were performed also pooling together AEDs sharing similar mechanisms of action.

RESULTS

Two hundreds and sixty-nine double-blind, placebo-controlled studies were identified and, among them, 127 RCTs with 16 AEDs (brivaracetam, gabapentin, lacosamide, levetiracetam, lamotrigine, oxcarbazepine, perampanel, pregabalin, phenytoin, remacemide, retigabine, rufinamide, tiagabine, topiramate, valproate, zonisamide) reported at least one of 19 symptoms or diseases that could be included in the Medical Dictionary for Regulatory Activities SOC term infections and infestations. These terms were singularly recorded and then pooled together in the SOC term infection and infestation. Topiramate was significantly associated with an increased risk of infection (risk difference = 0.04; 95% confidence interval = 0.01/0.06), while oxcarbazepine was significantly associated with a lower risk (-0.005; -0.09/-0.01). Risk difference of all studies with all AEDs showed a slight, but significantly increased risk of infection (0.01; 0.00/0.002). Levetiracetam and brivaracetam RCTs, when pooled together, were associated with a significantly increased risk of infection (0.03; 0.01/0.05).

CONCLUSIONS

Some AEDs are associated with a mild increased risk of infection.

Orally administered live attenuated Salmonella Typhimurium protects mice against lethal infection with H1N1 influenza virus

Pre-stimulation of toll-like receptors (TLRs) by agonists has been shown to increase protection against influenza virus infection. In this study, we evaluated the protective response generated against influenza A/Puerto Rico/8/1934 (PR8; H1N1) virus by oral and nasal administration of live attenuated Salmonella enterica serovar Typhimurium, JOL911 strain, in mice. Oral and nasal inoculation of JOL911 significantly increased the mRNA copy number of TLR-2, TLR4 and TLR5, and downstream type I interferon (IFN) molecules, IFN-α and IFN-β, both in peripheral blood mononuclear cells (PBMCs) and in lung tissue. Similarly, the mRNA copy number of interferon-inducible genes (ISGs), Mx and ISG15, were significantly increased in both the orally and the nasally inoculated mice. Post PR8 virus lethal challenge, the nasal JOL911 and the PBS control group mice showed significant loss of body weight with 70% and 100% mortality, respectively, compared to only 30% mortality in the oral JOL911 group mice. Post sub-lethal challenge, the significant reduction in PR8 virus copy number in lung tissue was observed in oral [on day 4 and 6 post-challenge (dpc)] and nasal (on 4dpc) than the PBS control group mice. The lethal and sub-lethal challenge showed that the generated stimulated innate resistance (StIR) in JOL911 inoculated mice conferred resistance to acute and initial influenza infection but might not be sufficient to prevent the PR8 virus invasion and replication in the lung. Overall, the present study indicates that oral administration of attenuated S. Typhimurium can pre-stimulate multiple TLR pathways in mice to provide immediate early StIR against a lethal H1N1 virus challenge.

Viral-bacterial interactions in the respiratory tract

In the respiratory tract, viruses and bacteria can interact on multiple levels. It is well known that respiratory viruses, particularly influenza viruses, increase the susceptibility to secondary bacterial infections. Numerous mechanisms, including compromised physical and immunological barriers, and changes in the microenvironment have hereby been shown to contribute to the development of secondary bacterial infections. In contrast, our understanding of how bacteria shape a response to subsequent viral infection is still limited. There is emerging evidence that persistent infection (or colonization) of the lower respiratory tract (LRT) with potential pathogenic bacteria, as observed in diseases like chronic obstructive pulmonary disease or cystic fibrosis, modulates subsequent viral infections by increasing viral entry receptors and modulating the inflammatory response. Moreover, recent studies suggest that even healthy lungs are not, as had long been assumed, sterile. The composition of the lung microbiome may thus modulate responses to viral infections. Here we summarize the current knowledge on the co-pathogenesis between viruses and bacteria in LRT infections.

The Role of Antimicrobial Peptides in Influenza Virus Infection and Their Potential as Antiviral and Immunomodulatory Therapy

Influenza A virus (IAV) remains a major threat that can cause severe morbidity and mortality due to rapid genomic variation. Resistance of IAVs to current anti-IAV drugs has been emerging, and antimicrobial peptides (AMPs) have been considered to be potential candidates for novel treatment against IAV infection. AMPs are endogenous proteins playing important roles in host defense through direct antimicrobial and antiviral activities and through immunomodulatory effects. In this review, we will discuss the anti-IAV and immunomodulatory effects of classical AMPs (defensins and cathelicidins), and proteins more recently discovered to have AMP-like activity (histones and Alzheimer's associated β-amyloid). We will discuss the interactions between AMPs and other host defense proteins. Major emphasis will be placed on novel synthetic AMPs derived from modification of natural proteins, and on potential methods of increasing expression of endogenous AMPs, since these approaches may lead to novel antiviral therapeutics.

Exposure to common respiratory bacteria alters the airway epithelial response to subsequent viral infection

Background

Colonization of the airways with potential pathogenic bacteria is observed in a number of chronic respiratory diseases, such as COPD or cystic fibrosis. Infections with respiratory viruses are known triggers of exacerbations of these diseases. We here investigated if pre-exposure to bacteria alters the response of lung epithelial cells to subsequent viral infection.

Methods

Bronchial epithelial cells (BEAS-2B cells and primary bronchial epithelial cells) were exposed to heat-inactivated Haemophilus influenzae, Pseudomonas aeruginosa or Streptococcus pneumoniae and subsequently infected with respiratory syncytial virus (RSV), type 2 human adenovirus or influenza B. Levels of pro-inflammatory cytokines, viral replication and expression of pattern recognition receptors were determined in culture supernatants and/or cell lysates.

Results

Exposure of BEAS-2B cells to H. influenzae before and during RSV-infection synergistically increased the release of IL-6 (increase above calculated additive effect at 72 h: 56 % ± 3 %, mean ± SEM) and IL-8 (53 % ± 12 %). This effect was sustained even when bacteria were washed away before viral infection and was neither associated with enhanced viral replication, nor linked to increased expression of key pattern recognition receptors. P. aeruginosa enhanced the release of inflammatory cytokines to a similar extent, yet only if bacteria were also present during viral infection. S. pneumoniae did not enhance RSV-induced cytokine release. Surprisingly, adenovirus infection significantly reduced IL-6 release in cells exposed to either of the three tested bacterial strains by on average more than 50 %. Infection with influenza B on the other hand did not affect cytokine production in BEAS-2B cells exposed to the different bacterial strains.

Conclusion

Pre-exposure of epithelial cells to bacteria alters the response to subsequent viral infection depending on the types of pathogen involved. These findings highlight the complexity of microbiome interactions in the airways, possibly contributing to the susceptibility to exacerbations and the natural course of airway diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-016-0382-z) contains supplementary material, which is available to authorized users.

Pulmonary immunostimulation with MALP-2 in influenza virus-infected mice increases survival after pneumococcal superinfection

Pulmonary infection with influenza virus is frequently complicated by bacterial superinfection, with Streptococcus pneumoniae being the most prevalent causal pathogen and hence often associated with high morbidity and mortality rates. Local immunosuppression due to pulmonary influenza virus infection has been identified as a major cause of the pathogenesis of secondary bacterial lung infection. Thus, specific local stimulation of the pulmonary innate immune system in subjects with influenza virus infection might improve the host defense against secondary bacterial pathogens. In the present study, we examined the effect of pulmonary immunostimulation with Toll-like receptor 2 (TLR-2)-stimulating macrophage-activating lipopeptide 2 (MALP-2) in influenza A virus (IAV)-infected mice on the course of subsequent pneumococcal superinfection. Female C57BL/6N mice infected with IAV were treated with MALP-2 on day 5 and challenged with S. pneumoniae on day 6. Intratracheal MALP-2 application increased proinflammatory cytokine and chemokine release and enhanced the recruitment of leukocytes, mainly neutrophils, into the alveolar space of IAV-infected mice, without detectable systemic side effects. Local pulmonary instillation of MALP-2 in IAV-infected mice 24 h before transnasal pneumococcal infection considerably reduced the bacterial number in the lung tissue without inducing exaggerated inflammation. The pulmonary viral load was not altered by MALP-2. Clinically, MALP-2 treatment of IAV-infected mice increased survival rates and reduced hypothermia and body weight loss after pneumococcal superinfection compared to those of untreated coinfected mice. In conclusion, local immunostimulation with MALP-2 in influenza virus-infected mice improved pulmonary bacterial elimination and increased survival after subsequent pneumococcal superinfection.

Mapping the pulmonary environment of animals protected from virulent H1N1 influenza infection using the TLR-2 agonist Pam₂Cys

We have previously shown that intranasal administration of the Toll-like receptor-2 agonist, S-(2,3-bis(palmitoyloxy)propyl) cysteine (Pam2Cys), provides immediate and antigen independent protection against challenge with influenza virus. Here we characterize the cellular pulmonary environments of mice which had either been treated with Pam2Cys or placebo and then challenged with influenza virus. We show that Pam2Cys treatment results in the influx of innate immune cells into the lungs and that depletion of phagocytic cells from this influx using clodronate-loaded liposomes caused a reduction in the number of interstitial macrophages and monocytes. This resulted in abolition of the protective effect indicating the importance of this cellular subset in Pam2Cys-mediated protection.

Generation of Adaptive Immune Responses Following Influenza Virus Challenge is Not Compromised by Pre-Treatment with the TLR-2 Agonist Pam2Cys

Immunostimulatory agents provide a new category of anti-microbial agents that activate the host’s innate immune system allowing control of viral and/or bacterial infections. The TLR-2 agonist PEG-Pam₂Cys has been shown to mediate potent anti-viral activity against influenza viruses when administered prophylactically (1). Here, we demonstrate that the treatment of mice with PEG-Pam₂Cys does not compromise their ability to generate adaptive immune responses following subsequent challenge with influenza virus. The antibody induced in mice pre-treated with Pam₂Cys possessed hemagglutination-inhibiting activities and the CD8⁺ T-cell responses that were elicited provided protection against heterologous viral challenge. In the absence of an effective influenza vaccine, an agent that provides immediate protection against the virus and does not compromise the induction of influenza-specific immunity on exposure to infectious virus provides an opportunity for population immunity to be achieved through natural exposure to virus.

Delivery of GM-CSF to Protect against Influenza Pneumonia

Background

Since adaptive immunity is thought to be central to immunity against influenza A virus (IAV) pneumonias, preventive strategies have focused primarily on vaccines. However, vaccine efficacy has been variable, in part because of antigenic shift and drift in circulating influenza viruses. Recent studies have highlighted the importance of innate immunity in protecting against influenza.

Methods

Granulocyte-macrophage colony stimulating factor (GM-CSF) contributes to maturation of mononuclear phagocytes, enhancing their capacity for phagocytosis and cytokine production.

Results

Overexpression of granulocyte macrophage-colony stimulating factor (GM-CSF) in the lung of transgenic mice provides remarkable protection against IAV, which depends on alveolar macrophages (AM). In this study, we report that pulmonary delivery of GM-CSF to wild type young and aged mice abrogated mortality from IAV.

Conclusion

We also demonstrate that protection is species specific and human GM-CSF do not protect the mice nor stimulates mouse immunity. We also show that IAV-induced lung injury is the culprit for side-effects of GM-CSF in treating mice after IAV infection, and introduce a novel strategy to deliver the GM-CSF to and retain it in the alveolar space even after IAV infection.

TGF-β-induced IL-6 prevents development of acute lung injury in influenza A virus-infected F508del CFTR-heterozygous mice

As the eighth leading cause of annual mortality in the USA, influenza A viruses are a major public health concern. In 20% of patients, severe influenza progresses to acute lung injury (ALI). However, pathophysiological mechanisms underlying ALI development are poorly defined. We reported that, unlike wild-type (WT) C57BL/6 controls, influenza A virus-infected mice that are heterozygous for the F508del mutation in the cystic fibrosis transmembrane conductance regulator (HETs) did not develop ALI. This effect was associated with higher IL-6 and alveolar macrophages (AMs) at 6 days postinfection (d.p.i.) in HET bronchoalveolar lavage fluid (BALF). In the present study, we found that HET AMs were an important source of IL-6 at 6 d.p.i. Infection also induced TGF-β production by HET but not WT mice at 2 d.p.i. TGF-β neutralization at 2 d.p.i. (TGF-N) significantly reduced BALF IL-6 in HETs at 6 d.p.i. Neither TGF-N nor IL-6 neutralization at 4 d.p.i. (IL-6-N) altered postinfection weight loss or viral replication in either mouse strain. However, both treatments increased influenza A virus-induced hypoxemia, pulmonary edema, and lung dysfunction in HETs to WT levels at 6 d.p.i. TGF-N and IL-6-N did not affect BALF AM and neutrophil numbers but attenuated the CXCL-1/keratinocyte chemokine response in both strains and reduced IFN-γ production in WT mice. Finally, bone marrow transfer experiments showed that HET stromal and myeloid cells are both required for protection from ALI in HETs. These findings indicate that TGF-β-dependent production of IL-6 by AMs later in infection prevents ALI development in influenza A virus-infected HET mice.

Enhanced Mucosal Antibody Production and Protection against Respiratory Infections Following an Orally Administered Bacterial Extract

Secondary bacterial infections following influenza infection are a pressing problem facing respiratory medicine. Although antibiotic treatment has been highly successful over recent decades, fatalities due to secondary bacterial infections remain one of the leading causes of death associated with influenza. We have assessed whether administration of a bacterial extract alone is sufficient to potentiate immune responses and protect against primary infection with influenza, and secondary infections with either Streptococcus pneumoniae or Klebsiella pneumoniae in mice. We show that oral administration with the bacterial extract, OM-85, leads to a maturation of dendritic cells and B-cells characterized by increases in MHC II, CD86, and CD40, and a reduction in ICOSL. Improved immune responsiveness against influenza virus reduced the threshold of susceptibility to secondary bacterial infections, and thus protected the mice. The protection was associated with enhanced polyclonal B-cell activation and release of antibodies that were effective at neutralizing the virus. Taken together, these data show that oral administration of bacterial extracts provides sufficient mucosal immune stimulation to protect mice against a respiratory tract viral infection and associated sequelae.

Pneumonia during remission induction chemotherapy in patients with acute leukemia

BACKGROUND

Pneumonia is a major cause of death during induction chemotherapy for acute leukemia. The purpose of this study was to quantify the incidence, risk factors, and outcomes of pneumonia in patients with acute leukemia.

METHODS

We conducted a retrospective cohort study of 801 patients with acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), or acute lymphocytic leukemia (ALL) who underwent induction chemotherapy.

MEASUREMENTS AND MAIN RESULTS

Pneumonia was present at induction start in 85 patients (11%). Of the 716 remaining patients, 148 (21%) developed pneumonia. The incidence rate of pneumonia was higher in MDS and AML than in ALL (0.013 vs. 0.008 vs. 0.003 pneumonias per day, respectively; P < 0.001). In multivariate analysis, age greater than or equal to 60 years, AML, low platelet count, low albumin level, neutropenia, and neutrophil count greater than 7,300 were risk factors. The case fatality rate of pneumonia was 17% (40 of 233). Competing risk analysis demonstrated that in the absence of pneumonia, death was rare: 28-day mortality was 6.2% for all patients but only 1.26% in those without pneumonia. Compared with patients without pneumonia, patients with pneumonia had more intensive care unit days, longer hospital stays, and 49% higher costs (P < 0.001).

CONCLUSIONS

Pneumonia after induction chemotherapy for acute leukemia continues to be common, and it is the most important determinant of early mortality after induction chemotherapy. Given the high incidence, morbidity, mortality, and cost of pneumonia, interventions aimed at prevention are warranted in patients with acute leukemia.

Activation of lung toll-like receptors does not exacerbate sickness responses to lipopolysaccharide in mice

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 stimulate innate lung immunity, 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 (1× or 8×) vs phosphate buffered saline (PBS) either immediately before intraperitoneal injection of 0.1mg/kg lipopolysaccharide (LPS) or PBS (equivolume) or 2h after. Sickness responses (reduced body weight, food intake, activity and social interaction) were examined at 2 and 5.5h 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.

B cells are not essential for Lactobacillus-mediated protection against lethal pneumovirus infection

We have shown previously that priming of respiratory mucosa with live Lactobacillus species promotes robust and prolonged survival from an otherwise lethal infection with pneumonia virus of mice, a property known as heterologous immunity. Lactobacillus priming results in a moderate reduction in virus recovery and a dramatic reduction in virus-induced proinflammatory cytokine production; the precise mechanisms underlying these findings remain to be elucidated. Because B cells have been shown to promote heterologous immunity against respiratory virus pathogens under similar conditions, in this study we explore the role of B cells in Lactobacillus-mediated protection against acute pneumovirus infection. We found that Lactobacillus-primed mice feature elevated levels of airway Igs IgG, IgA, and IgM and lung tissues with dense, B cell (B220(+))-enriched peribronchial and perivascular infiltrates with germinal centers consistent with descriptions of BALT. No B cells were detected in lung tissue of Lactobacillus-primed B cell deficient μMT mice or Jh mice, and Lactobacillus-primed μMT mice had no characteristic infiltrates or airway Igs. Nonetheless, we observed diminished virus recovery and profound suppression of virus-induced proinflammatory cytokines CCL2, IFN-γ, and CXCL10 in both wild-type and Lactobacillus-primed μMT mice. Furthermore, Lactobacillus plantarum-primed, B cell-deficient μMT and Jh mice were fully protected from an otherwise lethal pneumonia virus of mice infection, as were their respective wild-types. We conclude that B cells are dispensable for Lactobacillus-mediated heterologous immunity and were not crucial for promoting survival in response to an otherwise lethal pneumovirus infection.

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.

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

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

Lung epithelial cells are essential effectors of inducible resistance to pneumonia

Infectious pneumonias are the 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 (TLR) 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 TLR 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.

pairheatmap: comparing expression profiles of gene groups in heatmaps

This paper presents a new visualization software called pairheatmap, which is able to generate and compare two heatmaps so as to compare expression patterns of gene groups. It adds a conditioning variable such as time to the heatmap, and provides separate clustering for row groups in the first heatmap in order to visualize pattern changes between two heatmaps. pairheatmap is developed in R statistical environment. It provides: (1) the flexible framework for comparing two heatmaps; and (2) high-quality figures based on R package grid. The general architecture can be efficiently incorporated into bioinformatics pipeline. The package and user documentation are free to download at http://cran.r-project.org/web/packages/pairheatmap/index.html.

The amazing innate immune response to influenza A virus infection

Influenza A viruses (IAVs) remain a major health threat and a prime example of the significance of innate immunity. Our understanding of innate immunity to IAV has grown dramatically, yielding new concepts that change the way we view innate immunity as a whole. Examples include the role of p53, autophagy, microRNA, innate lymphocytes, endothelial cells and gut commensal bacteria in pulmonary innate immunity. Although the innate response is largely beneficial, it also contributes to major complications of IAV, including lung injury, bacterial super-infection and exacerbation of reactive airways disease. Research is beginning to dissect out which components of the innate response are helpful or harmful. IAV uses its limited genetic complement to maximum effect. Several viral proteins are dedicated to combating innate responses, while other viral structural or replication proteins multitask as host immune modulators. Many host innate immune proteins also multitask, having roles in cell cycle, signaling or normal lung biology. We summarize the plethora of new findings and attempt to integrate them into the larger picture of how humans have adapted to the threat posed by this remarkable virus. We explore how our expanded knowledge suggests ways to modulate helpful and harmful inflammatory responses, and develop novel treatments.

Induction of innate immunity in lungs with virus-like nanoparticles leads to protection against influenza and Streptococcus pneumoniae challenge

Nanoparticles composed of the coat protein of a plant virus (papaya mosaic virus; PapMV) and a single-stranded RNA (ssRNA) trigger a strong innate immune stimulation in the lungs of the animals a few hours following instillation. A rapid recruitment of neutrophils, monocytes/macrophages and lymphocytes follows. This treatment was able to provide protection to an influenza challenge that lasts at least 5 days. Protection could be recalled for longer periods by repeating the instillations once per week for more than 10 weeks. The treatment also conferred protection to a lethal challenge with Streptococcus pneumoniae--the major cause of bacterial pneumonia. Finally, we also showed that the nanoparticles could be used to treat mice infected with influenza and significantly decrease morbidity. These data strengthen the potential for using PapMV nanoparticles as non-specific inducers of the innate immune response in lungs during viral pandemics or to combat bioterrorist attack.

FROM THE CLINICAL EDITOR

In this study, virus-like nanoparticles were utilized to induce innate immune responses in a mouse model. They were also demonstrated to provide enhanced immune responses during actual pneumonia and ongoing viral infection. Strategies like this may become very helpful in human applications, including bioterrorism countermeasures.

Newer influenza antivirals, biotherapeutics and combinations

This summary provides an overview of investigational antiviral agents for influenza and of future directions for development of influenza therapeutics. While progress in developing clinically useful antiviral agents for influenza has been generally slow, especially with respect to seriously ill and high-risk patients, important clinical studies of intravenous neuraminidase inhibitors, antibodies and drug combinations are currently in progress. The current decade offers the promise of developing small molecular weight inhibitors with novel mechanisms of action, including host-directed therapies, new biotherapeutics and drug combinations, that should provide more effective antiviral therapies and help mitigate the problem of antiviral resistance. Immunomodulatory interventions also offer promise but need to be based on better understanding of influenza pathogenesis, particularly in seriously ill patients. The development of combination interventions, immunomodulators and host-directed therapies presents unique clinical trial design and regulatory hurdles that remain to be addressed.

Lactobacillus priming of the respiratory tract: Heterologous immunity and protection against lethal pneumovirus infection

We showed previously that wild-type mice primed via intranasal inoculation with live or heat-inactivated Lactobacillus species were fully (100%) protected against the lethal sequelae of infection with the virulent pathogen, pneumonia virus of mice (PVM), a response that is associated with diminished expression of proinflammatory cytokines and diminished virus recovery. We show here that 40% of the mice primed with live Lactobacillus survived when PVM challenge was delayed for 5months. This robust and sustained resistance to PVM infection resulting from prior interaction with an otherwise unrelated microbe is a profound example of heterologous immunity. We undertook the present study in order to understand the nature and unique features of this response. We found that intranasal inoculation with L. reuteri elicited rapid, transient neutrophil recruitment in association with proinflammatory mediators (CXCL1, CCL3, CCL2, CXCL10, TNF-alpha and IL-17A) but not Th1 cytokines. IFNγ does not contribute to survival promoted by Lactobacillus-priming. Live L. reuteri detected in lung tissue underwent rapid clearance, and was undetectable at 24h after inoculation. In contrast, L. reuteri peptidoglycan (PGN) and L. reuteri genomic DNA (gDNA) were detected at 24 and 48h after inoculation, respectively. In contrast to live bacteria, intranasal inoculation with isolated L. reuteri gDNA elicited no neutrophil recruitment, had minimal impact on virus recovery and virus-associated production of CCL3, and provided no protection against the negative sequelae of virus infection. Isolated PGN elicited neutrophil recruitment and proinflammatory cytokines but did not promote sustained survival in response to subsequent PVM infection. Overall, further evaluation of the responses leading to Lactobacillus-mediated heterologous immunity may provide insight into novel antiviral preventive modalities.

Toll-like receptor 3 gene polymorphisms and severity of pandemic A/H1N1/2009 influenza in otherwise healthy children

BACKGROUND

Toll-like receptors (TLRs) form an essential part of the innate immune system, which plays a fundamental role in rapidly and effectively controlling infections and initiating adaptive immunity. There are no published data concerning the importance of polymorphisms of TLRs in conditioning susceptibility to influenza or the severity of the disease. The aim of this study was to evaluate whether selected polymorphisms of TLR2, TLR3 and TLR4 influence the incidence and clinical picture of pandemic A/H1N1/2009 influenza.

RESULTS

The study involved 272 healthy children attending our Emergency Room for influenza-like illness (ILI), including 51 (18.8%) with pandemic A/H1N1/2009 influenza as revealed by real-time polymerase chain reaction, and 164 healthy controls examined after minor surgery. Genomic DNA was extracted from whole blood samples and five single-nucleotide polymorphisms (SNPs) were studied: TLR2 rs5743708, TLR3 rs5743313, TLR3 rs5743315, TLR4 rs4986790 and TLR4 rs4986791. The TLR3 rs5743313/CT polymorphism was found in all of the children with pneumonia and influenza infection, but in a significantly smaller number of those with A/H1N1/2009 influenza without pneumonia (<0.0001). TLR2, TLR3 rs5743315/AC and TLR4 polymorphisms were equally distributed in all of the groups regardless of the presence of the pandemic A/H1N1/2009 virus and clinical diagnosis. Viral load was comparable in all of the study groups.

CONCLUSIONS

There is a close relationship between the presence of TLR3 rs5743313/CT and an increased risk of pneumonia in children infected by the pandemic A/H1N1/2009 influenza virus.

Interactions between Streptococcus pneumoniae and influenza virus: a mutually beneficial relationship?

Historically, most research on infectious diseases has focused on infections with single pathogens. However, infections with pathogens often occur in the context of pre-existing viral and bacterial infections. Clinically, this is of particular relevance for coinfections with Streptococcus pneumoniae and influenza virus, which together are an important cause of global morbidity and mortality. In recent years new evidence has emerged regarding the underlying mechanisms of influenza virus-induced susceptibility to secondary pneumococcal infections, in particular regarding the sustained suppression of innate recognition of S. pneumoniae. Conversely, it is also increasingly being recognized that there is not a unidirectional effect of the virus on S. pneumoniae, but that asymptomatic pneumococcal carriage may also affect subsequent influenza virus infection and the clinical outcome. Here, we will review both aspects of pneumococcal influenza virus infection, with a particular focus on the age-related differences in pneumococcal colonization rates and invasive pneumococcal disease.

Surfactant protein D (SP-D) alters cellular uptake of particles and nanoparticles

Surfactant protein D (SP-D) is primarily expressed in the lungs and modulates pro- and anti-inflammatory processes to toxic challenge, maintaining lung homeostasis. We investigated the interaction between NPs and SP-D and subsequent uptake by cells involved in lung immunity. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) measured NP aggregation, particle size and charge in native human SP-D (NhSP-D) and recombinant fragment SP-D (rfhSP-D). SP-D aggregated NPs, especially following the addition of calcium. Immunohistochemical analysis of A549 epithelial cells investigated the co-localization of NPs and rfhSP-D. rfhSP-D enhanced the co-localisation of NPs to epithelial A549 cells in vitro. NP uptake by alveolar macrophages (AMs) and lung dendritic cells (LDCs) from C57BL/6 and SP-D knock-out mice were compared. AMs and LDCs showed decreased uptake of NPs in SP-D deficient mice compared to wild-type mice. These data confirmed an interaction between SP-D and NPs, and subsequent enhanced NP uptake.