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Respiratory infections caused by multidrug-resistant Acinetobacter baumannii are difficult to treat and associated with high mortality among critically ill hospitalized patients. Bacteriophages (phages) eliminate pathogens with high host specificity and efficacy. However, the lack of appropriate preclinical experimental models hampers the progress of clinical development of phages as therapeutic agents. Therefore, we tested the efficacy of a purified lytic phage, vB_AbaM_Acibel004, against multidrug-resistant A. baumannii clinical isolate RUH 2037 infection in immunocompetent mice and a human lung tissue model. Sham- and A. baumannii-infected mice received a single-dose of phage or buffer via intratracheal aerosolization. Group-specific differences in bacterial burden, immune and clinical responses were compared. Phage-treated mice not only recovered faster from infection-associated hypothermia but also had lower pulmonary bacterial burden, lower lung permeability, and cytokine release. Histopathological examination revealed less inflammation with unaffected inflammatory cellular recruitment. No phage-specific adverse events were noted. Additionally, the bactericidal effect of the purified phage on A. baumannii was confirmed after single-dose treatment in an ex vivo human lung infection model. Taken together, our data suggest that the investigated phage has significant potential to treat multidrug-resistant A. baumannii infections and further support the development of appropriate methods for preclinical evaluation of antibacterial efficacy of phages.

Vaccine-associated enhanced respiratory disease (VAERD) is a severe complication for some respiratory infections. To investigate the potential for VAERD induction in coronavirus disease 2019 (COVID-19), we evaluate two vaccine leads utilizing a severe hamster infection model: a T helper type 1 (T(H)1)-biased measles vaccine-derived candidate and a T(H)2-biased alum-adjuvanted, non-stabilized spike protein. The measles virus (MeV)-derived vaccine protects the animals, but the protein lead induces VAERD, which can be alleviated by dexamethasone treatment. Bulk transcriptomic analysis reveals that our protein vaccine prepares enhanced host gene dysregulation in the lung, exclusively up-regulating mRNAs encoding the eosinophil attractant CCL-11, T(H)2-driving interleukin (IL)-19, or T(H)2 cytokines IL-4, IL-5, and IL-13. Single-cell RNA sequencing (scRNA-seq) identifies lung macrophages or lymphoid cells as sources, respectively. Our findings imply that VAERD is caused by the concerted action of hyperstimulated macrophages and T(H)2 cytokine-secreting lymphoid cells and potentially links VAERD to antibody-dependent enhancement (ADE). In summary, we identify the cytokine drivers and cellular contributors that mediate VAERD after T(H)2-biased vaccination.

The Roborovski dwarf hamster Phodopus roborovskii belongs to the Phodopus genus, one of the seven within Cricetinae subfamily. Like other rodents such as mice, rats, or ferrets, hamsters can be important animal models for a range of diseases. Whereas the Syrian hamster from the genus Mesocricetus is now widely used as a model for mild-to-moderate coronavirus disease 2019, Roborovski dwarf hamster shows a severe-to-lethal course of disease upon infection with the novel human coronavirus severe acute respiratory syndrome coronavirus 2.

Vaccines are a cornerstone in COVID-19 pandemic management. Here, we compare immune responses to and preclinical efficacy of the mRNA vaccine BNT162b2, an adenovirus-vectored spike vaccine, and the live-attenuated-virus vaccine candidate sCPD9 after single and double vaccination in Syrian hamsters. All regimens containing sCPD9 showed superior efficacy. The robust immunity elicited by sCPD9 was evident in a wide range of immune parameters after challenge with heterologous SARS-CoV-2 including rapid viral clearance, reduced tissue damage, fast differentiation of pre-plasmablasts, strong systemic and mucosal humoral responses, and rapid recall of memory T cells from lung tissue. Our results demonstrate that use of live-attenuated vaccines may offer advantages over available COVID-19 vaccines, specifically when applied as booster, and may provide a solution for containment of the COVID-19 pandemic.

Vaccine-associated enhanced respiratory disease (VAERD) is a severe complication for some respiratory infections. To investigate the potential for VAERD induction in coronavirus disease 2019 (COVID-19), we evaluate two vaccine leads utilizing a severe hamster infection model: a T helper type 1 (T

For coronavirus disease 2019 (COVID-19), effective and well-understood treatment options are still scarce. Since vaccine efficacy is challenged by novel variants, short-lasting immunity, and vaccine hesitancy, understanding and optimizing therapeutic options remains essential. We aimed at better understanding the effects of two standard-of-care drugs, dexamethasone and anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies, on infection and host responses. By using two COVID-19 hamster models, pulmonary immune responses were analyzed to characterize effects of single or combinatorial treatments. Pulmonary viral burden was reduced by anti-SARS-CoV-2 antibody treatment and unaltered or increased by dexamethasone alone. Dexamethasone exhibited strong anti-inflammatory effects and prevented fulminant disease in a severe disease model. Combination therapy showed additive benefits with both anti-viral and anti-inflammatory potency. Bulk and single-cell transcriptomic analyses confirmed dampened inflammatory cell recruitment into lungs upon dexamethasone treatment and identified a specifically responsive subpopulation of neutrophils, thereby indicating a potential mechanism of action. Our analyses confirm the anti-inflammatory properties of dexamethasone and suggest possible mechanisms, validate anti-viral effects of anti-SARS-CoV-2 antibody treatment, and reveal synergistic effects of a combination therapy, thus informing more effective COVID-19 therapies.

Since December 2019, the novel human coronavirus SARS-CoV-2 has spread globally, causing millions of deaths. Unprecedented efforts have enabled development and authorization of a range of vaccines, which reduce transmission rates and confer protection against the associated disease COVID-19. These vaccines are conceptually diverse, including e.g. classical adjuvanted whole-inactivated virus, viral vectors, and mRNA vaccines.We have analysed two prototypic model vaccines, the strongly TH1-biased measles vaccine-derived candidate MeVvac2-SARS2-S(H) and a TH2-biased Alum-adjuvanted, non-stabilized Spike (S) protein side-by-side, for their ability to protect Syrian hamsters upon challenge with a low-passage SARS-CoV-2 patient isolate. As expected, the MeVvac2-SARS2-S(H) vaccine protected the hamsters safely from severe disease. In contrast, the protein vaccine induced vaccine-associated enhanced respiratory disease (VAERD) with massive infiltration of eosinophils into the lungs. Global RNA-Seq analysis of hamster lungs revealed reduced viral RNA and less host dysregulation in MeVvac2-SARS2-S(H) vaccinated animals, while S protein vaccination triggered enhanced host gene dysregulation compared to unvaccinated control animals. Of note, mRNAs encoding the major eosinophil attractant CCL-11, the TH2 response-driving cytokine IL-19, as well as TH2-cytokines IL-4, IL-5, and IL-13 were exclusively up-regulated in the lungs of S protein vaccinated animals, consistent with previously described VAERD induced by RSV vaccine candidates. IL-4, IL-5, and IL-13 were also up-regulated in S-specific splenocytes after protein vaccination. Using scRNA-Seq, T cells and innate lymphoid cells were identified as the source of these cytokines, while Ccl11 and Il19 mRNAs were expressed in lung macrophages displaying an activated phenotype. Interestingly, the amount of viral reads in this macrophage population correlated with the abundance of Fc-receptor reads. These findings suggest that VAERD is triggered by induction of TH2-type helper cells secreting IL-4, IL-5, and IL-13, together with stimulation of macrophage subsets dependent on non-neutralizing antibodies. Via this mechanism, uncontrolled eosinophil recruitment to the infected tissue occurs, a hallmark of VAERD immunopathogenesis. These effects could effectively be treated using dexamethasone and were not observed in animals vaccinated with MeVvac2-SARS2-S(H).Taken together, our data validate the potential of TH2-biased COVID-19 vaccines and identify the transcriptional mediators that underlie VAERD, but confirm safety of TH1-biased vaccine concepts such as vector-based or mRNA vaccines. Dexamethasone, which is already in use for treatment of severe COVID-19, may alleviate such VAERD, but in-depth scrutiny of any next-generation protein-based vaccine candidates is required, prior and after their regulatory approval.

Atherosclerosis is one of the leading causes of death worldwide. Biomathematical modelling of the underlying disease and therapy processes might be a useful aid to develop and improve preventive and treatment concepts of atherosclerosis. We here propose a biomathematical model of murine atherosclerosis under different diet and treatment conditions including lipid modulating compound and antibiotics. The model is derived by translating known biological mechanisms into ordinary differential equations and by assuming appropriate response kinetics to the applied interventions. We explicitly describe the dynamics of relevant immune cells and lipid species in atherosclerotic lesions including the degree of blood vessel occlusion due to growing plaques. Unknown model parameters were determined by fitting the predictions of model simulations to time series data derived from mice experiments. Parameter fittings resulted in a good agreement of model and data for all 13 experimental scenarios considered. The model can be used to predict the outcome of alternative treatment schedules of combined antibiotic, immune modulating, and lipid lowering agents under high fat or normal diet. We conclude that we established a comprehensive biomathematical model of atherosclerosis in mice. We aim to validate the model on the basis of further experimental data.

The Roborovski dwarf hamster Phodopus roborovskii belongs to the Phodopus genus, one of seven within Cricetinae subfamily. Like other rodents such as mice, rats or ferrets, hamsters can be important animal models for a range of diseases. Whereas the Syrian hamster from the genus Mesocricetus is now widely used as a model for mild to moderate COVID-19, Roborovski dwarf hamster show a severe to lethal course of disease upon infection with the novel human coronavirus SARS-CoV-2.

Idiopathic pulmonary fibrosis (IPF) is a deadly condition characterized by progressive respiratory dysfunction. Exacerbations due to airway infections are believed to promote disease progression, and presence of Streptococcus in the lung microbiome has been associated with the progression of IPF and mortality. The aim of this study was to analyze the effect of lung fibrosis on susceptibility to pneumococcal pneumonia and bacteremia. The effects of subclinical (low dose) infection with Streptococcus pneumoniae were studied in a well characterized fos-related antigen-2 (Fra-2) transgenic (TG) mouse model of spontaneous, progressive pulmonary fibrosis. Forty-eight hours after transnasal infection with S. pneumoniae, bacterial load was assessed in lung tissue, bronchoalveolar lavage (BAL), blood, and spleen. Leukocyte subsets and cytokine levels were analyzed in BAL and blood. Lung compliance and arterial blood gases were assessed. In contrast to wildtype mice, low dose lung infection with S. pneumoniae in Fra-2 TG mice resulted in substantial pneumonia including weight loss, increased lung bacterial load, and bacteremia. BAL alveolar macrophages were reduced in Fra-2 TG mice compared to the corresponding WT mice. Proinflammatory cytokines and chemokines (IL-1β, IL-6, TNF-α, and CXCL1) were elevated upon infection in BAL supernatant and plasma of Fra-2 TG mice. Lung compliance was decreased in Fra-2 TG mice following low dose infection with S. pneumoniae. Pulmonary fibrosis increases susceptibility to pneumococcal pneumonia and bacteremia possibly via impaired alveolar bacterial clearance.

In COVID-19, immune responses are key in determining disease severity. However, cellular mechanisms at the onset of inflammatory lung injury in SARS-CoV-2 infection, particularly involving endothelial cells, remain ill-defined. Using Syrian hamsters as model for moderate COVID-19, we conducted a detailed longitudinal analysis of systemic and pulmonary cellular responses, and corroborated it with datasets from COVID-19 patients. Monocyte-derived macrophages in lungs exerted the earliest and strongest transcriptional response to infection, including induction of pro-inflammatory genes, while epithelial cells showed weak activation. Without evidence for productive infection, endothelial cells reacted, depending on cell subtypes, by strong and early expression of anti-viral, pro-inflammatory, and T cell recruiting genes. Recruitment of cytotoxic T cells as well as emergence of IgM antibodies preceded viral clearance at day 5 post infection. Investigating SARS-CoV-2 infected Syrian hamsters can thus identify cell type-specific effector functions, provide detailed insights into pathomechanisms of COVID-19, and inform therapeutic strategies.

In COVID-19, the immune response largely determines disease severity and is key to therapeutic strategies. Cellular mechanisms contributing to inflammatory lung injury and tissue repair in SARS-CoV-2 infection, particularly endothelial cell involvement, remain ill-defined. We performed detailed spatiotemporal analyses of cellular and molecular processes in SARS-CoV-2 infected Syrian hamsters. Comparison of hamster single-cell sequencing and proteomics with data sets from COVID-19 patients demonstrated inter-species concordance of cellular and molecular host-pathogen interactions. In depth vascular and pulmonary compartment analyses (i) supported the hypothesis that monocyte-derived macrophages dominate inflammation, (ii) revealed endothelial inflammation status and T-cell attraction, and (iii) showed that CD4+ and CD8+ cytotoxic T-cell responses precede viral elimination. Using the Syrian hamster model of self-limited moderate COVID-19, we defined the specific roles of endothelial and epithelial cells, among other myeloid and non-myeloid lung cell subtypes, for determining the disease course.

Introduction: In 2014, the WHO proclaimed the beginning of a post-antibiotic era [1]. As alternatives to antibiotics, bacteriophages are increasingly coming into focus to combat the increasing number of resistant bacteria. In order to reach infected sites in the lungs and reduce unwanted systemic effects, nebulization of drugs is a favorable way of application. The infectivity of phages with different tail lengths after nebulization was tested under various conditions. This project is part of Phage4Cure, a BMBF-funded study examining the use of phages against lung infections. Methods: Long-tailed (Siphoviridae), short-tailed (Podoviridae) and medium long tailed (Myoviridae) phages from the order Caudovirales were analyzed. Four different phages per morphotype were nebulized with a JET nebulizer. Additionally, three phages (two Myoviridae, one Podovirus) were purified according to laboratory standards. By using the double-agar overlay method, titers after nebulization were compared to the stock solution. Results: Phages of the type Siphoviridae showed the highest titer losses during nebulization and Podoviridae the lowest. Among the Myoviridae variable and phage-dependent titer loss was observed. In the mesh nebulization system, all three phages showed a loss of titer after nebulization independent of the purification degree. Only one of the purified phages showed a higher titer loss after nebulization compared to lysate. Conclusion: For successful phage inhalation therapy, the effects of nebulizer technology, the size of the phage tail and purity must be considered. [1] www.who.int/mediacentre/news/releases/2014/amr-report/en/

Community-acquired pneumonia by primary or superinfections with Streptococcus pneumoniae can lead to acute respiratory distress requiring mechanical ventilation. The pore-forming toxin pneumolysin alters the alveolar-capillary barrier and causes extravasation of protein-rich fluid into the interstitial pulmonary tissue, which impairs gas exchange. Platelets usually prevent endothelial leakage in inflamed pulmonary tissue by sealing inflammation-induced endothelial gaps. We not only confirm that S pneumoniae induces CD62P expression in platelets, but we also show that, in the presence of pneumolysin, CD62P expression is not associated with platelet activation. Pneumolysin induces pores in the platelet membrane, which allow anti-CD62P antibodies to stain the intracellular CD62P without platelet activation. Pneumolysin treatment also results in calcium efflux, increase in light transmission by platelet lysis (not aggregation), loss of platelet thrombus formation in the flow chamber, and loss of pore-sealing capacity of platelets in the Boyden chamber. Specific anti-pneumolysin monoclonal and polyclonal antibodies inhibit these effects of pneumolysin on platelets as do polyvalent human immunoglobulins. In a post hoc analysis of the prospective randomized phase 2 CIGMA trial, we show that administration of a polyvalent immunoglobulin preparation was associated with a nominally higher platelet count and nominally improved survival in patients with severe S pneumoniae–related community-acquired pneumonia. Although, due to the low number of patients, no definitive conclusion can be made, our findings provide a rationale for investigation of pharmacologic immunoglobulin preparations to target pneumolysin by polyvalent immunoglobulin preparations in severe community-acquired pneumococcal pneumonia, to counteract the risk of these patients becoming ventilation dependent. This trial was registered at www.clinicaltrials.gov as #NCT01420744.

Background Antibiotic exposure alters the microbiota, which can impact the inflammatory immune responses. Critically ill patients frequently receive antibiotic treatment and are often subjected to mechanical ventilation, which may induce local and systemic inflammatory responses and development of ventilator-induced lung injury (VILI). The aim of this study was to investigate whether disruption of the microbiota by antibiotic therapy prior to mechanical ventilation affects pulmonary inflammatory responses and thereby the development of VILI. Methods Mice underwent 6–8 weeks of enteral antibiotic combination treatment until absence of cultivable bacteria in fecal samples was confirmed. Control mice were housed equally throughout this period. VILI was induced 3 days after completing the antibiotic treatment protocol, by high tidal volume (HTV) ventilation (34 ml/kg; positive end-expiratory pressure = 2 cmH2O) for 4 h. Differences in lung function, oxygenation index, pulmonary vascular leakage, macroscopic assessment of lung injury, and leukocyte and lymphocyte differentiation were assessed. Control groups of mice ventilated with low tidal volume and non-ventilated mice were analyzed accordingly. Results Antibiotic-induced microbiota depletion prior to HTV ventilation led to aggravation of VILI, as shown by increased pulmonary permeability, increased oxygenation index, decreased pulmonary compliance, enhanced macroscopic lung injury, and increased cytokine/chemokine levels in lung homogenates. Conclusions Depletion of the microbiota by broad-spectrum antibiotics prior to HTV ventilation renders mice more susceptible to developing VILI, which could be clinically relevant for critically ill patients frequently receiving broad-spectrum antibiotics. Electronic supplementary material The online version of this article (10.1186/s13054-018-2213-8) contains supplementary material, which is available to authorized users.

The molecular mechanisms that control innate immune cell trafficking during chronic infection and inflammation, such as in tuberculosis (TB), are incompletely understood. During active TB, myeloid cells infiltrate the lung and sustain local inflammation. While the chemoattractants that orchestrate these processes are increasingly recognized, the posttranscriptional events that dictate their availability are unclear. We identified microRNA-223 (miR-223) as an upregulated small noncoding RNA in blood and lung parenchyma of TB patients and during murine TB. Deletion of miR-223 rendered TB-resistant mice highly susceptible to acute lung infection. The lethality of miR-223(–/–) mice was apparently not due to defects in antimycobacterial T cell responses. Exacerbated TB in miR-223(–/–) animals could be partially reversed by neutralization of CXCL2, CCL3, and IL-6, by mAb depletion of neutrophils, and by genetic deletion of Cxcr2. We found that miR-223 controlled lung recruitment of myeloid cells, and consequently, neutrophil-driven lethal inflammation. We conclude that miR-223 directly targets the chemoattractants CXCL2, CCL3, and IL-6 in myeloid cells. Our study not only reveals an essential role for a single miRNA in TB, it also identifies new targets for, and assigns biological functions to, miR-223. By regulating leukocyte chemotaxis via chemoattractants, miR-223 is critical for the control of TB and potentially other chronic inflammatory diseases.

Human immune system mice are highly valuable for in vivo dissection of human immune responses. Although they were employed for analyzing tuberculosis (TB) disease, there is little data on the spatial organization and cellular composition of human immune cells in TB granuloma pathology in this model. We demonstrate that human immune system mice, generated by transplanted human fetal liver derived hematopoietic stem cells develop a continuum of pulmonary lesions upon Mycobacterium tuberculosis aerosol infection. In particular, caseous necrotic granulomas, which contribute to prolonged TB treatment time, developed, and had cellular phenotypic spatial-organization similar to TB patients. By comparing two recommended drug regimens, we confirmed observations made in clinical settings: Adding Moxifloxacin to a classical chemotherapy regimen had no beneficial effects on bacterial eradication. We consider this model instrumental for deeper understanding of human specific features of TB pathogenesis and of particular value for the pre-clinical drug development pipeline.

Background: Neutrophils are important components of innate immune responses against bacterial infections, yet excessive neutrophil responses might result in life-threatening lung injury. Neutrophil recruitment to sites of inflammation is partly mediated by the chemokine receptor CXCR2. Chemokines, like the CXCR2 ligands, which target a shared receptor, are generally considered redundant. However, we and others described their individual spatial and temporal regulation patterns. Aims and Objectives: To investigate if pneumocyte-derived ligand CXCL5 plays a superordinate role in acute lung injury. Methods: Murine models of ventilator-induced lung injury (VILI) and pneumococcal pneumonia in CXCL5-deficient (Cxcl5‒/‒) and wild-type (WT) mice. Results: Following mechanical ventilation, absence of CXCL5 resulted in reduced alveolar neutrophil recruitment and decreased vascular leakage. Depletion of neutrophils prior to VILI confirmed their impact on lung barrier disruption. In line, in response to pulmonary Streptococcus pneumoniae infection, neutrophil recruitment significantly depended on CXCL5 signaling. Reduced neutrophil numbers resulted in increased bacterial burden in Cxcl5‒/‒ compared to WT mice without affecting overall survival rates. Notably, despite elevated bacterial burden, vascular leakage was reduced in the absence of CXCL5. Conclusions: Our results confirm the non-redundancy of CXCR2 ligands and highlight the importance of CXCL5 in neutrophil recruitment and development of lung barrier failure in acute lung injury. Targeting CXCL5 may possibly provide a therapeutic perspective in pneumonia and mechanical ventilation.

Purpose: CAP is frequent, with severe manifestations, suffering, and high costs. Improvement of risk stratification by blood gene expression biomarkers predicting severe outcomes may support clinical decision-making and reduce mortality of CAP patients. Patients and methods: In the PROGRESS study, hospitalized CAP was followed for 28 days with daily clinical assessment for five and sampling of peripheral blood for four days. Disease severity was operationalized by SOFA score. Death and requirement of intensive care with pneumonia-specific treatment were considered severe endpoint. Time series gene expression data were analyzed for prediction of CAP severity and for pathway activation. Results were compared with gene-expression data from sepsis studies. Results: Several genes were strongly associated with future severe disease, >5000 genes were associated with current CAP severity, and >250 with current severe endpoint. Increasing CAP severity correlated with increased inactivation of immune-related pathways, especially related to T-cells. Published expression signatures correlated well with current but poorly predict future CAP severity. We created a new classifier to predict future severe endpoints and compared it with prediction based on the SOFA score. Conclusion: CAP severity correlated with substantial gene expression regulation of immune-related pathways. There are candidates for new biomarkers for improving diagnosis, risk stratification, therapy decisions, and outcome for patients with CAP.

Background Community-acquired pneumonia (CAP) remains a major cause of death worldwide. Mechanisms underlying the detrimental outcome despite adequate antibiotic therapy and comorbidity management are still not fully understood. Methods To model timely versus delayed antibiotic therapy in patients, mice with pneumococcal pneumonia received ampicillin twice a day starting early (24 h) or late (48 h) after infection. Clinical readouts and local and systemic inflammatory mediators after early and late antibiotic intervention were examined. Results Early antibiotic intervention rescued mice, limited clinical symptoms and restored fitness, whereas delayed therapy resulted in high mortality rates. Recruitment of innate immune cells remained unaffected by antibiotic therapy. However, both early and late antibiotic intervention dampened local levels of inflammatory mediators in the alveolar spaces. Early treatment protected from barrier breakdown, and reduced levels of vascular endothelial growth factor (VEGF) and perivascular and alveolar edema formation. In contrast, at 48 h post infection, increased pulmonary leakage was apparent and not reversed by late antibiotic treatment. Concurrently, levels of VEGF remained high and no beneficial effect on edema formation was evident despite therapy. Moreover, early but not late treatment protected mice from a vast systemic inflammatory response. Conclusions Our data show that only early antibiotic therapy, administered prior to breakdown of the alveolar–capillary barrier and systemic inflammation, led to restored fitness and rescued mice from fatal streptococcal pneumonia. The findings highlight the importance of identifying CAP patients prior to lung barrier failure and systemic inflammation and of handling CAP as a medical emergency. Electronic supplementary material The online version of this article (10.1186/s13054-018-2224-5) contains supplementary material, which is available to authorized users.

The secreted airway mucus cell protein chloride channel regulator, calcium-activated 1, CLCA1, plays a role in inflammatory respiratory diseases via as yet unidentified pathways. For example, deficiency of CLCA1 in a mouse model of acute pneumonia resulted in reduced cytokine expression with less leukocyte recruitment and the human CLCA1 was shown to be capable of activating macrophages in vitro. Translation of experimental data between human and mouse models has proven problematic due to several CLCA species-specific differences. We therefore characterized activation of macrophages by CLCA1 in detail in solely murine ex vivo and in vitro models. Only alveolar but not bone marrow-derived macrophages freshly isolated from C57BL6/J mice increased their expression levels of several pro-inflammatory and leukotactic cytokines upon CLCA1 stimulation. Among the most strongly regulated genes, we identified the host-protective and immunomodulatory airway mucus component BPIFA1, previously unknown to be expressed by airway macrophages. Furthermore, evidence from an in vivo Staphylococcus aureus pneumonia mouse model suggests that CLCA1 may also modify BPIFA1 expression in airway epithelial cells. Our data underscore and specify the role of mouse CLCA1 in inflammatory airway disease to activate airway macrophages. In addition to its ability to upregulate cytokine expression which explains previous observations in the Clca1-deficient S. aureus pneumonia mouse model, modulation of BPIFA1 expression expands the role of CLCA1 in airway disease to involvement in more complex downstream pathways, possibly including liquid homeostasis, airway protection, and antimicrobial defense. Electronic supplementary material The online version of this article (10.1007/s00418-018-1664-y) contains supplementary material, which is available to authorized users.

Descriptive histopathology of mouse models of pneumonia is essential in assessing the outcome of infections, molecular manipulations, or therapies in the context of whole lungs. Quantitative comparisons between experimental groups, however, have been limited to laborious stereology or ill-defined scoring systems that depend on the subjectivity of a more or less experienced observer. Here, we introduce self-learning digital image analyses that allow us to transform optical information from whole mouse lung sections into statistically testable data. A pattern-recognition-based software and a nuclear count algorithm were adopted to quantify user-defined pathologies from whole slide scans of lungs infected with Streptococcus pneumoniae or influenza A virus compared with PBS-challenged lungs. The readout parameters "relative area affected" and "nuclear counts per area" are proposed as relevant criteria for the quantification of lesions from hematoxylin and eosin-stained sections, also allowing for the generation of a heat map of, for example, immune cell infiltrates with anatomical assignments across entire lung sections. Moreover, when combined with immunohistochemical labeling of marker proteins, both approaches are useful for the identification and counting of, for example, immune cell populations, as validated here by direct comparisons with flow cytometry data. The solutions can easily and flexibly be adjusted to specificities of different models or pathogens. Automated digital analyses of whole mouse lung sections may set a new standard for the user-defined, high-throughput comparative quantification of histological and immunohistochemical images. Still, our algorithms established here are only a start, and need to be tested in additional studies and other applications in the future.

Background: Global spread of multidrug resistant (MDR) bacteria is one of the biggest threats in modern medicine. Acinetobacter baumannii is a feared cause of lung infections particularly in critically ill patients lacking antibiotic options. Therefore, rediscovery of phage therapy has gained attention as treatment option due to its specificity and effectivity. Aims: This preclinical study evaluated the efficacy and safety of a novel phage preparation in a mouse model of A. baumannii lung infection. Methods: Mice were infected with a MDR A. baumannii strain [1]. Phage Acibel004 [2] was produced as suspension including efficient depletion of endotoxins using a newly established protocol. Solvent or phages were sprayed intratracheally 12 hours after infection. Clinical parameters, bacterial load, cell influx, lung permeability and cytokine release were quantified and histopathological examination was performed. Results: Phage-treated mice recovered faster from infection-associated hypothermia. Phage treatment reduced bacterial loads in lungs and BAL 48 hours after infection. Moreover, lung permeability and cytokine release were reduced. Histopathological examination of lungs revealed lesser extent of inflammation in phage-treated mice with unaffected cellular recruitment. No adverse effects were observed. Conclusion: For the first time, a highly purified phage against A. baumannii was successfully used to treat lung infection in vivo. The current preclinical data support the concept of phage-based therapy against pulmonary A. baumannii infections. [1] Knapp, S. et al. Am J Respir Crit Care Med 2006; 1;173(1):122-9 [2] Merabishvili, M. et al. PLoS One 2014; 11;9(8):e104853

Photodynamic therapy (PDT) has emerged as an effective and minimally invasive cancer treatment modality. In the present study, two novel phthalocyanines, tetra‑triethyleneoxysulfonyl substituted zinc phthalocyanine (ZnPc) and dihydroxy‑2,9(10),16(17),23(24)‑tetrakis(4,7,10‑trioxaundecan‑1‑sulfonyl) silicon phthalocyanine (Pc32), were investigated as photosensitizers (PS) for PDT of cholangiocarcinoma (CC). ZnPc showed a pronounced dose‑dependent and predominantly cytoplasmic accumulation in EGI‑1 and TFK‑1 CC cell lines. Pc32 also accumulated in the CC cells, but this was less pronounced. Without photoactivation, the PS did not exhibit any antiproliferative or cytotoxic effects. Upon photoactivation, ZnPc induced the formation of reactive oxygen species (ROS) and immediate phototoxicity, leading to a dose‑dependent decrease in cell proliferation, and an induction of mitochondria‑driven apoptosis and cell cycle arrest of EGI‑1 and TFK‑1 cells. Although photoactivated Pc32 also induced ROS formation in the two cell lines, the extent was less marked, compared with that induced by ZnPc‑PDT, and pronounced antipoliferative effects occurred only in the less differentiated EGI‑1 cells, whereas the more differentiated TFK‑1 cells did not show sustained growth inhibition upon Pc32‑PDT induction. In vivo examinations on the antiangiogenic potency of the novel PS were performed using chorioallantoic membrane (CAM) assays, which revealed reduced angiogenic sprouting with a concomitant increase in nonperfused regions and degeneration of the vascular network of the CAM following induction with ZnPc‑PDT only. The study demonstrated the pronounced antiproliferative and antiangiogenic potency of ZnPc as a novel PS for PDT, meriting further elucidation as a promising PS for the photodynamic treatment of CC.

Background: Pneumonia may result in life-threatening lung failure due to an exaggerated host-pathogen interaction. Angiopoietin- (Ang-)1 mediated Tie2-activation reduced and the antagonist Ang-2 increased inflammation and permeability in sepsis. The role of Ang-2 in severe pneumonia is unclear. Thus, we newly established an inducible Ang-2-knockout (KO) mouse and investigated the impact of Ang-2 expression on the pulmonary endothelial barrier. Methods: Isolated lung endothelial cells (LECs) of inducible Ang-2loxP/loxP-ERT2cre+/- mice (Ang-2-KO) and control littermates Ang-2loxP/loxP-ERT2cre-/- (WT) were treated with 4-hydroxytamoxifen for knockdown (KD)-induction, and stimulated with pneumolysin (PLY). VE-cadherin was stained. Further, mice were injected with tamoxifen for KD-induction and infected with Streptococcus pneumoniae (S. pneumoniae). Pulmonary permeability, inflammation response, bacterial burden and lung histomorphology were analysed 48h later. KD was controlled by PCR, Ang-2-ELISA, histological staining and RT-real-time-qPCR. Results: In vitro LECs of Ang-2-KO mice showed less damage after PLY-stimulation. In vivo the Ang-2-KO mice had reduced Ang-2-mRNA in lung tissue and isolated LECs, decreased Ang-2-plasma levels and less pulmonary Ang-2 expression. S. pneumoniae infected Ang-2-KO mice showed no differences in lung permeability, in pulmonary and systemic immune responses or in bacterial loads compared to WT animals. Conclusion: Our data suggest that an incomplete Ang-2 knockdown has a protective effect on endothelial integrity in vitro but no significant influence on pulmonary barrier function in mice with pneumococcal pneumonia.