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1.  FMS-Like Tyrosine Kinase 3 Ligand Treatment of Mice Aggravates Acute Lung Injury in Response to Streptococcus pneumoniae: Role of Pneumolysin 
Infection and Immunity  2012;80(12):4281-4290.
FMS-like tyrosine kinase-3 ligand (Flt3L) is a dendritic cell (DC) growth and differentiation factor with potential in antitumor therapies and antibacterial immunization strategies. However, the effect of systemic Flt3L treatment on lung-protective immunity against bacterial infection is incompletely defined. Here, we examined the impact of deficient (in Flt3L knockout [KO] mice), normal (in wild-type [WT] mice), or increased Flt3L availability (in WT mice pretreated with Flt3L for 3, 5, or 7 days) on lung DC subset profiles and lung-protective immunity against the major lung-tropic pathogen, Streptococcus pneumoniae. Although in Flt3L-deficient mice the numbers of DCs positive for CD11b (CD11bpos DCs) and for CD103 (CD103pos DCs) were diminished, lung permeability, a marker of injury, was unaltered in response to S. pneumoniae. In contrast, WT mice pretreated with Flt3L particularly responded with increased numbers of CD11bpos DCs and with less pronounced numbers of CD103pos DCs and impaired bacterial clearance and with increased lung permeability following S. pneumoniae challenge. Notably, infection of Flt3L-pretreated mice with S. pneumoniae lacking the pore-forming toxin, pneumolysin (PLY), resulted in substantially less lung CD11bpos DCs activation and reduced lung permeability. Collectively, this study establishes that Flt3L treatment enhances the accumulation of proinflammatory activated lung CD11bpos DCs which contribute to acute lung injury in response to PLY released by S. pneumoniae.
doi:10.1128/IAI.00854-12
PMCID: PMC3497444  PMID: 23006850
2.  TNF-related apoptosis-inducing ligand (TRAIL) exerts therapeutic efficacy for the treatment of pneumococcal pneumonia in mice 
The Journal of Experimental Medicine  2012;209(11):1937-1952.
Neutrophil-derived TRAIL induces apoptosis of alveolar macrophages, limiting the spread of S. pneumoniae infection.
Apoptotic death of alveolar macrophages observed during lung infection with Streptococcus pneumoniae is thought to limit overwhelming lung inflammation in response to bacterial challenge. However, the underlying apoptotic death mechanism has not been defined. Here, we examined the role of the TNF superfamily member TNF-related apoptosis-inducing ligand (TRAIL) in S. pneumoniae–induced macrophage apoptosis, and investigated the potential benefit of TRAIL-based therapy during pneumococcal pneumonia in mice. Compared with WT mice, Trail−/− mice demonstrated significantly decreased lung bacterial clearance and survival in response to S. pneumoniae, which was accompanied by significantly reduced apoptosis and caspase 3 cleavage but rather increased necrosis in alveolar macrophages. In WT mice, neutrophils were identified as a major source of intraalveolar released TRAIL, and their depletion led to a shift from apoptosis toward necrosis as the dominant mechanism of alveolar macrophage cell death in pneumococcal pneumonia. Therapeutic application of TRAIL or agonistic anti-DR5 mAb (MD5-1) dramatically improved survival of S. pneumoniae–infected WT mice. Most importantly, neutropenic mice lacking neutrophil-derived TRAIL were protected from lethal pneumonia by MD5-1 therapy. We have identified a previously unrecognized mechanism by which neutrophil-derived TRAIL induces apoptosis of DR5-expressing macrophages, thus promoting early bacterial killing in pneumococcal pneumonia. TRAIL-based therapy in neutropenic hosts may represent a novel antibacterial treatment option.
doi:10.1084/jem.20120983
PMCID: PMC3478925  PMID: 23071253
3.  Local delivery of Granulocyte/Macrophage Colony Stimulating Factor protects mice from lethal pneumococcal pneumonia1 
The growth factor granulocyte/macrophage-colony stimulating factor (GM-CSF) has an important role in pulmonary surfactant metabolism and the regulation of antibacterial activities of lung sentinel cells. However, the potential of intra-alveolar GM-CSF to augment lung protective immunity against inhaled bacterial pathogens has not been defined in preclinical infection models. We hypothesized that transient overexpression of GM-CSF in the lungs of mice by adenoviral gene transfer (Ad-GM-CSF) would protect mice from subsequent lethal pneumococcal pneumonia. Our data show that intra-alveolar delivery of Ad-GM-CSF led to sustained increased pSTAT5 expression and PU.1 protein expression in alveolar macrophages during a 28 day observation period. Pulmonary Ad-GM-CSF delivery two or four weeks prior to infection of mice with S. pneumoniae significantly reduced mortality rates relative to control vector treated mice. This increased survival was accompanied by increased iNOS expression, antibacterial activity and a significant reduction in caspase 3 dependent apoptosis and secondary necrosis of lung sentinel cells. Importantly, therapeutic treatment of mice with recombinant GM-CSF improved lung protective immunity and accelerated bacterial clearance after pneumococcal challenge. We conclude that prophylactic delivery of GM-CSF triggers long-lasting immunostimulatory effects in the lung in vivo and rescues mice from lethal pneumococcal pneumonia by improving antibacterial immunity. These data support use of novel antibiotic-independent immunostimulatory therapies to protect patients against bacterial pneumonias.
doi:10.4049/jimmunol.1101413
PMCID: PMC3595102  PMID: 22003204
GM-CSF; S. pneumoniae; PU.1; pneumonia; therapy; infection
4.  Dendritic Cell Depletion and Repopulation in the Lung after Irradiation and Bone Marrow Transplantation in Mice 
Dendritic cells (DCs) are essential for innate and adaptive immunity, but are purported to exhibit variable radiosensitivity in response to irradiation in various bone marrow transplantation (BMT) protocols. To address this controversy, we analyzed the magnitude of depletion and repopulation of both lung CD11bpos DC and CD103pos DC subsets in response to irradiation and BMT in a murine model. In our study, CD45.2pos donor bone marrow cells were transplanted into irradiated CD45.1pos recipient mice to examine the depletion of recipient DC subsets and the repopulation of donor DC subsets. We observed an apoptosis-mediated and necrosis-mediated depletion (> 90%) of the recipient CD103pos DC subset, and only a 50–60% depletion of recipient CD11bpos DCs from lung parenchymal tissue on Days 3 and 5, whereas recipient alveolar and lung macrophages were much less radiosensitive, showing an approximately 50% depletion by Days 14–21 after treatment. A repopulation of lung tissue with donor DC subsets had occurred by Days 10 and 28 for CD11bpos DCs and CD103pos DCs, whereas alveolar and lung macrophages were repopulated by 6 and 10 weeks after treatment. Furthermore, the infection of mice with Streptococcus pneumoniae further accelerated the turnover of lung DCs and lung macrophage subsets. Our data illustrate the vulnerability of lung CD103pos DCs and CD11bpos DCs to irradiation, and indicate that an accelerated turnover of lung DC subsets occurs, relative to pulmonary and lung macrophages. Our findings may have important implications in the development of adjuvant immune-stimulatory protocols that could reduce the risk of opportunistic infections in patients undergoing BMT.
doi:10.1165/rcmb.2010-0279OC
PMCID: PMC3361352  PMID: 21177980
dendritic cell; macrophage; pneumonia; Streptococcus pneumoniae; CD103
5.  Cathepsin G and Neutrophil Elastase Play Critical and Nonredundant Roles in Lung-Protective Immunity against Streptococcus pneumoniae in Mice ▿  
Infection and Immunity  2011;79(12):4893-4901.
Neutrophil serine proteases cathepsin G (CG), neutrophil elastase (NE), and proteinase 3 (PR3) have recently been shown to contribute to killing of Streptococcus pneumoniae in vitro. However, their relevance in lung-protective immunity against different serotypes of S. pneumoniae in vivo has not been determined so far. Here, we examined the effect of CG and CG/NE deficiency on the lung host defense against S. pneumoniae in mice. Despite similar neutrophil recruitment, both CG knockout (KO) mice and CG/NE double-KO mice infected with focal pneumonia-inducing serotype 19 S. pneumoniae demonstrated a severely impaired bacterial clearance, which was accompanied by lack of CG and NE but not PR3 proteolytic activity in recruited neutrophils, as determined using fluorescence resonance energy transfer (FRET) substrates. Moreover, both CG and CG/NE KO mice but not wild-type mice responded with increased lung permeability to infection with S. pneumoniae, resulting in severe respiratory distress and progressive mortality. Both neutrophil depletion and ablation of hematopoietic CG/NE in bone marrow chimeras abolished intra-alveolar CG and NE immunoreactivity and led to bacterial outgrowth in the lungs of mice, thereby identifying recruited neutrophils as the primary cellular source of intra-alveolar CG and NE. This is the first study showing a contribution of neutrophil-derived neutral serine proteases CG and NE to lung-protective immunity against focal pneumonia-inducing serotype 19 S. pneumoniae in mice. These data may be important for the development of novel intervention strategies to improve lung-protective immune mechanisms in critically ill patients suffering from severe pneumococcal pneumonia.
doi:10.1128/IAI.05593-11
PMCID: PMC3232647  PMID: 21911460
6.  Evaluation of Biophotonic Imaging To Estimate Bacterial Burden in Mice Infected with Highly Virulent Compared to Less Virulent Streptococcus pneumoniae Serotypes▿ †  
Bioluminescence imaging is an innovative, noninvasive tool to analyze infectious disease progression under real-life conditions in small laboratory animals. However, the relevance of bioluminescence imaging to monitor invasive compared to noninvasive bacterial infections of the lung has not been examined so far. In the current study, we systematically evaluated the importance of bioluminescence imaging to monitor pneumococcal disease progression by correlating biophotonic signals with lung bacterial loads in two mouse strains (BALB/c, C57BL/6) infected with either self-glowing, bioluminescent serotype 19 Streptococcus pneumoniae causing focal pneumonia or serotype 2 S. pneumoniae causing invasive pneumococcal disease. The best correlations between bioluminescence signals and lung CFU counts were observed in BALB/c mice compared to C57BL/6 mice just on day 3 after infection with invasive serotype 2 S. pneumoniae, while excellent correlations between photon counts and bacterial loads were observed in isolated lungs of BALB/c and C57BL/6 mice, irrespective of the employed pneumococcal serotype. Moreover, good correlations between biophotonic signals and CFU counts were also observed in mice upon infection with serotype 19 S. pneumoniae causing focal pneumonia in mice, again with best correlation values obtained for BALB/c mice at day 3 postinfection. Collectively, we show that the relevance of biophotonic imaging to monitor S. pneumoniae-induced lung infections in mice is largely influenced by the disease model under investigation. The provided data may be important for studies of infectious diseases.
doi:10.1128/AAC.00310-10
PMCID: PMC2916300  PMID: 20530224
7.  Micro-computed tomography of pulmonary fibrosis in mice induced by adenoviral gene transfer of biologically active transforming growth factor-β1 
Respiratory Research  2010;11(1):181.
Background
Micro-computed tomography (micro-CT) is a novel tool for monitoring acute and chronic disease states in small laboratory animals. Its value for assessing progressive lung fibrosis in mice has not been reported so far. Here we examined the importance of in vivo micro-CT as non-invasive tool to assess progression of pulmonary fibrosis in mice over time.
Methods
Pulmonary fibrosis was induced in mice by intratracheal delivery of an adenoviral gene vector encoding biologically active TGF-ß1 (AdTGF-ß1). Respiratory gated and ungated micro-CT scans were performed at 1, 2, 3, and 4 weeks post pulmonary adenoviral gene or control vector delivery, and were then correlated with respective histopathology-based Ashcroft scoring of pulmonary fibrosis in mice. Visual assessment of image quality and consolidation was performed by 3 observers and a semi-automated quantification algorithm was applied to quantify aerated pulmonary volume as an inverse surrogate marker for pulmonary fibrosis.
Results
We found a significant correlation between classical Ashcroft scoring and micro-CT assessment using both visual assessment and the semi-automated quantification algorithm. Pulmonary fibrosis could be clearly detected in micro-CT, image quality values were higher for respiratory gated exams, although differences were not significant. For assessment of fibrosis no significant difference between respiratory gated and ungated exams was observed.
Conclusions
Together, we show that micro-CT is a powerful tool to assess pulmonary fibrosis in mice, using both visual assessment and semi-automated quantification algorithms. These data may be important in view of pre-clinical pharmacologic interventions for the treatment of lung fibrosis in small laboratory animals.
doi:10.1186/1465-9921-11-181
PMCID: PMC3022722  PMID: 21176193
8.  Importance of CXC Chemokine Receptor 2 in Alveolar Neutrophil and Exudate Macrophage Recruitment in Response to Pneumococcal Lung Infection▿  
Infection and Immunity  2010;78(6):2620-2630.
Sustained neutrophilic infiltration is known to contribute to organ damage, such as acute lung injury. CXC chemokine receptor 2 (CXCR2) is the major receptor regulating inflammatory neutrophil recruitment in acute and chronic inflamed tissues. Whether or not the abundant neutrophil recruitment observed in severe pneumonia is essential for protective immunity against Streptococcus pneumoniae infections is incompletely defined. Here we show that CXCR2 deficiency severely perturbs the recruitment of both neutrophils and exudate macrophages associated with a massive bacterial outgrowth in distal airspaces after infection with S. pneumoniae, resulting in 100% mortality in knockout (KO) mice within 3 days. Moreover, irradiated wild-type mice reconstituted with increasing amounts of CXCR2 KO bone marrow (10, 25, 50, and 75% KO) have correspondingly decreased numbers of both neutrophils and exudate macrophages, which is associated with a stepwise increase in bacterial burden and a reciprocal stepwise decrease in survival in S. pneumoniae-induced pulmonary infection. Finally, application of the CXCR2 antagonist SB-225002 resulted in decreased alveolar neutrophil and exudate macrophage recruitment in mice along with increased lung bacterial loads after infection with S. pneumoniae. Together, these data show that CXC chemokine receptor 2 serves a previously unrecognized nonredundant role in the regulation of both neutrophil and exudate macrophage recruitment to the lung in response to S. pneumoniae infection. In addition, we demonstrate that a threshold level of 10 to 25% of reduced neutrophil recruitment is sufficient to cause increased mortality in mice infected with S. pneumoniae.
doi:10.1128/IAI.01169-09
PMCID: PMC2876546  PMID: 20368349
9.  Efficacy Profiles of Daptomycin for Treatment of Invasive and Noninvasive Pulmonary Infections with Streptococcus pneumoniae▿  
Daptomycin is a novel lipopeptide antibiotic with excellent activity against Gram-positive bacterial pathogens, but its therapeutic value for the treatment of invasive pneumococcal disease compared to that for the treatment of pneumococcal pneumonia is incompletely defined. We investigated the efficacy of daptomycin in two models of Streptococcus pneumoniae-induced lung infection, i.e., pneumococcal pneumonia and septic pneumococcal disease. Mice were infected with a bioluminescent, invasive serotype 2 S. pneumoniae strain or a less virulent serotype 19 S. pneumoniae strain and were then given semitherapeutic or therapeutic daptomycin or ceftriaxone. Readouts included survival; bacterial loads; and septic disease progression, as determined by biophotonic imaging. Semitherapeutic daptomycin treatment fully protected the mice against the progression of septic disease induced by serotype 2 S. pneumoniae, while therapeutic treatment of the mice with daptomycin or ceftriaxone led to ∼70% or ∼60% survival, respectively. In contrast, mice infected with serotype 19 S. pneumoniae developed severe pneumonia and lung leakage even in the presence of increased intra-alveolar daptomycin levels, resulting in only 40% survival, whereas the ceftriaxone-treated mice had 100% survival. Together, although daptomycin demonstrates little efficacy in the treatment of pneumococcal pneumonia, daptomycin is highly effective in preventing S. pneumoniae-induced septic death, thus possibly offering a therapeutic option for patients with life-threatening septic pneumococcal disease.
doi:10.1128/AAC.00943-09
PMCID: PMC2812129  PMID: 19917756
10.  Overexpression of cathepsin K in mice decreases collagen deposition and lung resistance in response to bleomycin-induced pulmonary fibrosis 
Respiratory Research  2008;9(1):54.
Background
Lung fibrosis is a devastating pulmonary disorder characterized by alveolar epithelial injury, extracellular matrix deposition and scar tissue formation. Due to its potent collagenolytic activity, cathepsin K, a lysosomal cysteine protease is an interesting target molecule with therapeutic potential to attenuate bleomycin-induced pulmonary fibrosis in mice. We here tested the hypothesis that over-expression of cathepsin K in the lungs of mice is protective in bleomycin-induced pulmonary fibrosis.
Methods
Wild-type and cathepsin K overexpressing (cathepsin K transgenic; cath K tg) mice were challenged intratracheally with bleomycin and sacrificed at 1, 2, 3 and 4 weeks post-treatment followed by determination of lung fibrosis by estimating lung collagen content, lung histopathology, leukocytic infiltrates and lung function. In addition, changes in cathepsin K protein levels in the lung were determined by immunohistochemistry, real time RT-PCR and western blotting.
Results
Cathepsin K protein levels were strongly increased in alveolar macrophages and lung parenchymal tissue of mock-treated cathepsin K transgenic (cath K tg) mice relative to wild-type mice and further increased particularly in cath K tg but also wild-type mice in response to bleomycin. Moreover, cath K tg mice responded with a lower collagen deposition in their lungs, which was accompanied by a significantly lower lung resistance (RL) compared to bleomycin-treated wild-type mice. In addition, cath K tg mice responded with a lower degree of lung fibrosis than wild-type mice, a process that was found to be independent of inflammatory leukocyte mobilization in response to bleomycin challenge.
Conclusion
Over-expression of cathepsin K reduced lung collagen deposition and improved lung function parameters in the lungs of transgenic mice, thereby providing at least partial protection against bleomycin-induced lung fibrosis.
doi:10.1186/1465-9921-9-54
PMCID: PMC2490691  PMID: 18638383
11.  Endotoxin induced peritonitis elicits monocyte immigration into the lung: implications on alveolar space inflammatory responsiveness 
Respiratory Research  2006;7(1):30.
Background
Acute peritonitis developing in response to gram-negative bacterial infection is known to act as a trigger for the development of acute lung injury which is often complicated by the development of nosocomial pneumonia. We hypothesized that endotoxin-induced peritonitis provokes recruitment of monocytes into the lungs, which amplifies lung inflammatory responses to a second hit intra-alveolar challenge with endotoxin.
Methods
Serum and lavage cytokines as well as bronchoalveolar lavage fluid cells were analyzed at different time points after intraperitoneal or intratracheal application of LPS.
Results
We observed that mice challenged with intraperitoneal endotoxin developed rapidly increasing serum and bronchoalveolar lavage fluid (BALF) cytokine and chemokine levels (TNFα, MIP-2, CCL2) and a nearly two-fold expansion of the alveolar macrophage population by 96 h, but this was not associated with the development of neutrophilic alveolitis. In contrast, expansion of the alveolar macrophage pool was not observed in CCR2-deficient mice and in wild-type mice systemically pretreated with the anti-CD18 antibody GAME-46. An intentional two-fold expansion of alveolar macrophage numbers by intratracheal CCL2 following intraperitoneal endotoxin did not exacerbate the development of acute lung inflammation in response to intratracheal endotoxin compared to mice challenged only with intratracheal endotoxin.
Conclusion
These data, taken together, show that intraperitoneal endotoxin triggers a CCR2-dependent de novo recruitment of monocytes into the lungs of mice but this does not result in an accentuation of neutrophilic lung inflammation. This finding represents a previously unrecognized novel inflammatory component of lung inflammation that results from endotoxin-induced peritonitis.
doi:10.1186/1465-9921-7-30
PMCID: PMC1388208  PMID: 16503998

Results 1-11 (11)