Respiratory reovirus 1/L induction of intraluminal fibrosis, a model of bronchiolitis obliterans organizing pneumonia, is dependent on T lymphocytes

Systematic Review of Systemic Corticosteroids for Treatment of Organizing Pneumonia

Introduction

Regardless corticosteroids are recommended for the treatment of organizing pneumonia there is limited evidence supporting this practice. Thus, we performed a systematic review of the literature on systemic corticosteroid treatment for organizing pneumonia.

Methods

A search was implemented in the PubMed database (Medline) for articles published in the last 20 years. Those studies with incomplete or insufficient data and case reports were excluded. We collected data including: demographics, clinical data, diagnostic procedures, aetiology, treatment regimen (drug, posology, duration, response) and evolution.

Results

A total of 135 publications were selected and finally 13 studies with 849 patients were included in the review: 12 retrospective observational studies and a single prospective observational study. Most of the patients were started on treatment with systemic corticosteroids - a total of 627 (30-100% depending on the series), but there was a great heterogeneity regarding drug, doses and duration. On those that started treatment, 226 (36%) presented a relapse of the disease during follow-up. Only one study provided information regarding treatment side-effects.

Conclusion

The findings of this systematic review show the low quality data supporting the use of corticosteroids for the treatment of organizing pneumonia. This highlights a need to undertake appropriately designed studies to investigate which is the most appropriate treatment regimen that trades off benefits and risks of prolonged corticosteroid administration.

IL13 May Play an Important Role in Developing Eosinophilic Chronic Rhinosinusitis and Eosinophilic Otitis Media with Severe Asthma

A woman in her 50s was a super responder to benralizumab administered for the treatment of severe bronchial asthma (BA) with eosinophilic chronic rhinosinusitis with nasal polyp (ECRS) and eosinophilic otitis media (EOM). She exhibited the gradual exacerbation of ECRS/EOM despite good control of BA approximately 1 year after benralizumab initiation. Therefore, the treatment was switched to dupilumab, and the condition of the paranasal sinuses and middle ear greatly improved with the best control of her asthma. The patient reported that her physical condition was the best of her life. However, she developed a pulmonary opacity on chest computed tomography after 6 months. Histological examination of the lung parenchyma and cell differentiation of the bronchoalveolar lavage fluid indicated atypical chronic eosinophilic pneumonia, and treatment was switched to mepolizumab. Similarly to the period of benralizumab treatment, exacerbation of ECRS/EOM reduced her quality of life approximately 10 months after the administration of mepolizumab. Dupilumab was again introduced as a replacement for mepolizumab. The clinical course and consideration of the interaction between inflammatory cells led us to speculate that interleukin-13 could play a key role in the development of ECRS/EOM with severe BA.

Chronic lymphocytic leukemia and the skin: implications for the dermatologist

B-cell chronic lymphocytic leukemia (CLL) is the most prevalent leukemia in the United States, and its diagnosis can have many dermatologic implications. For one, the cutaneous manifestations of CLL include several entities, most notably leukemia cutis, eosinophilic dermatosis of hematologic malignancy, and a heightened risk of skin infections. Additionally, CLL patients are at an increased risk of secondary malignancies, most commonly of the skin. Furthermore, a number of commonly utilized treatments for CLL have cutaneous implications which should be considered in the interdisciplinary management of CLL patients. In this review, we will provide an update on the diverse cutaneous manifestations of CLL and CLL-directed therapies in order to help guide dermatologic management of this increasingly prevalent patient population.

The contribution of animal models to understanding the role of the immune system in human idiopathic pulmonary fibrosis

Pulmonary fibrosis occurs in a heterogeneous group of lung disorders and is characterised by an excessive deposition of extracellular matrix proteins within the pulmonary interstitium, leading to impaired gas transfer and a loss of lung function. In the past 10 years, there has been a dramatic increase in our understanding of the immune system and how it contributes to fibrogenic processes within the lung. This review will compare some of the models used to investigate the pathogenesis and treatment of pulmonary fibrosis, in particular those used to study immune cell pathogenicity in idiopathic pulmonary fibrosis, highlighting their advantages and disadvantages in dissecting human disease.

Late Noninfectious Pulmonary Complications in Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation (HSCT) is an established therapeutic modality for a number of malignant and nonmalignant conditions. Pulmonary complications following HSCT are associated with increased mortality and morbidity. These complications may be classified into infectious versus noninfectious, and early versus late based on the time of occurrence post-transplant. Thus, exclusion of infectious etiologies is the first step in the diagnoses of pulmonary complications. Late onset noninfectious pulmonary complications typically occur 3 months post-transplant. Bronchiolitis obliterans is the major contributor to late-onset pulmonary complications, and its clinical presentation, pathogenesis, and current therapeutic approaches are discussed. Idiopathic pneumonia syndrome is another important complication which usually occurs early, although its onset may be delayed. Organizing pneumonia is important to recognize due to its responsiveness to corticosteroids. Other late onset noninfectious pulmonary complications discussed here include pulmonary venoocclusive disease, pulmonary cytolytic thrombi, pleuroparenchymal fibroelastosis, thoracic air leak syndrome, and posttransplant lymphoproliferative disorders.

In Vivo Live Imaging of Oncolytic Mammalian Orthoreovirus Expressing NanoLuc Luciferase in Tumor Xenograft Mice

Wild-type mammalian reoviruses (MRVs) have been evaluated as oncolytic agents against various cancers; however, genetic modification methods for improving MRV agents have not been exploited fully. In the present study, using MRV strain T1L, we generated a reporter MRV that expresses a NanoLuc luciferase (NLuc) gene and used it for noninvasive imaging of MRV infection in tumor xenograft mice. NLuc and a P2A self-cleaving peptide gene cassette were placed upstream of the L1 gene open reading frame to enable bicistronic expression of NLuc and the L1 gene product. BALB/c nude mice intranasally infected with MRV expressing NLuc (rsT1L-NLuc) displayed bioluminescent signals in the chest area at 4 days postinfection (dpi), which is consistent with natural MRV infection in the lung. Furthermore, to monitor tumor-selective infection by MRV, nude mice bearing human cancer xenografts were infected intravenously with rsT1L-NLuc. Bioluminescent signals were detected in tumors as early as 3 dpi and persisted for 2 months. The results demonstrate the utility of an autonomous replicating reporter MRV for noninvasive live imaging of replicating oncolytic MRV agents.IMPORTANCE Engineering of recombinant MRV for improved oncolytic activity has not yet been achieved due to difficulty in generating autonomous replicating MRV harboring transgenes. Here, we constructed a reporter MRV that can be used to monitor cancer-selective infection by oncolytic MRV in a mouse model. Among the numerous oncolytic viruses, MRV has an advantage in that the wild-type virus shows marked oncolytic activity in patients without any notable adverse effects. The reporter MRV developed herein will open avenues to the development of recombinant MRV vectors armed with anticancer transgenes.

Current Approach to Non-Infectious Pulmonary Complications of Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation is an established treatment for patients with a wide range of malignant and nonmalignant conditions. Noninfectious pulmonary complications still remain a leading cause of morbidity and mortality in these patients. Treating hematopoietic stem cell transplantation recipients with noninfectious pulmonary complications is still challenging, and the current treatment armamentarium and strategies are not adequate for patients receiving hematopoietic stem cell transplantation. Further trials are needed for a better description of the pathogenesis and the complete diagnostic criteria as well as for the development of effective therapeutic approaches for the management of noninfectious pulmonary complications of the hematopoietic stem cell transplantation. This review outlines the incidence, risk factors, pathogenesis, and clinical spectrum and discusses the current approaches to the management of noninfectious pulmonary complications of Hematopoietic stem cell transplantation.

Epigallocatechin-3-gallate inhibits TLR4 signaling through the 67-kDa laminin receptor and effectively alleviates acute lung injury induced by H9N2 swine influenza virus

Epigallocatechin-3-gallate (EGCG) was found to inhibit the Toll-like receptor 4 (TLR4) pathway involved in influenza virus pathogenesis. Here, the effect of EGCG on TLR4 in an H9N2 virus-induced acute lung injury mouse model was investigated. BALB/c mice were inoculated intranasally with A/Swine/Hebei/108/2002 (H9N2) virus or noninfectious allantoic fluid, and treated with EGCG and E5564 or normal saline orally for 5 consecutive days. PMVECs were treated with EGCG or anti-67kDa laminin receptor (LR). Lung physiopathology, inflammation, oxidative stress, viral replication, and TLR4/NF-κB/Toll-interacting protein (Tollip) pathway in lung tissue and/or PMVECs were investigated. EGCG attenuated lung histological lesions, decreased lung W/D ratio, cytokines levels, and inhibited MPO activity and prolonged mouse survival. EGCG treatment also markedly downregulated TLR4 and NF-κB protein levels but Tollip expression was upregulated compared with that in untreated H9N2-infected mice (P<0.05). In PMVECs, anti-67LR antibody treatment significantly downregulated Tollip levels; however, the TLR4 and NF-κB protein levels dramatically increased compared with that in the EGCG-treated group (P<0.05). EGCG remarkably downregulated TLR4 protein levels through 67LR/Tollip, decreased MPO activity and inflammatory cytokine levels, supporting EGCG as a potential therapeutic agent for managing acute lung injury induced by H9N2 SIV.

Cutaneous Adverse Events of Targeted Therapies for Hematolymphoid Malignancies

The identification of oncogenic drivers of liquid tumors has led to the rapid development of targeted agents with distinct cutaneous adverse event (AE) profiles. The diagnosis and management of these skin toxicities has motivated a novel partnership between dermatologists and oncologists in developing supportive oncodermatology clinics. In this article we review the current state of knowledge of clinical presentation, mechanisms, and management of the most common and significant cutaneous AEs observed during treatment with targeted therapies for hematologic and lymphoid malignancies. We systematically review according to drug-targeting pathway the cutaneous AE profiles of these drugs, and offer insight when possible into whether pharmacologic target versus immunologic modulation primarily underlie presentation. We include discussion of tyrosine kinase inhibitors (imatinib, dasatinib, nilotinib, bosutinib, ponatinib), blinatumomab, ibrutinib, idelalisib, anti-B cell antibodies (rituximab, ibritumomab, obinutuzumab, ofatumumab, tositumomab), immune checkpoint inhibitors (nivolumab, pembrolizumab), alemtuzumab, brentuximab, and proteasome inhibitors (bortezomib, carfilzomib, ixazomib). We highlight skin reactions seen with antiliquid but not solid tumor agents, draw attention to serious cutaneous AEs that might require therapy modification or cessation, and offer management strategies to permit treatment tolerability. We emphasize the importance of early diagnosis and treatment to minimize disruptions to care, optimize prognosis and quality of life, and promptly address life-threatening skin or infectious events. This evolving partnership between oncologists and dermatologists in the iterative characterization and management of skin toxicities will contribute to a better understanding of these drugs' cutaneous targets and improved patient care.

Organizing pneumonia in mice and men

BACKGROUND

Organizing pneumonia is a reaction pattern and an inflammatory response to acute lung injuries, and is characterized by intraluminal plugs of granulation tissue in distal airspaces. In contrast to other fibrotic pulmonary diseases, organizing pneumonia is generally responsive to corticosteroids. However, some patients do not respond to treatment, leading to respiratory failure and potentially death (up to 15 % of patients). In order to devise new therapeutic strategies, a better understanding of the disease's pathomechanisms is warranted. We previously generated a mouse model overexpressing CCL2, which generates organizing pneumonia-like changes, morphologically comparable to human patients. In this study, we investigated whether the histopathological similarities of human and murine pulmonary organizing pneumonia lesions also involve similar molecular pathways.

METHODS

We analyzed the similarities and differences of fibrosis-associated gene expression in individual compartments from patients with organizing pneumonia and transgenic (CCL2) mice using laser-assisted microdissection, real-time PCR and immunohistochemistry.

RESULTS

Gene expression profiling of human and murine organizing pneumonia lesions showed in part comparable expression levels of pivotal genes, notably of TGFB1/Tgfb1, TIMP1/Timp1, TIMP2/Timp2, COL3A1/Col3a1, CXCL12/Cxcl12, MMP2/Mmp2 and IL6/Il6. Hence, the transgenic CCL2 mouse model shows not only pathogenomic and morphological features of human organizing pneumonia but also a similar inflammatory profile.

CONCLUSIONS

We suggest that the CCL2-overexpressing transgenic mouse model (CCL2 Tg mice) is suitable for further investigation of fibrotic pulmonary remodeling, particularly of organizing pneumonia pathogenesis and for the search for novel therapeutic strategies.

Carnosine markedly ameliorates H9N2 swine influenza virus-induced acute lung injury

Oxidative stress injury is an important pathogenesis of influenza virus in critically ill patients. The present study investigated the efficacy of carnosine, an antioxidant and free radical scavenger, on a model of acute lung injury (ALI) induced by H9N2 swine influenza virus. Female specific-pathogen-free BALB/c mice were randomized into four groups and treated as follows: (1) H9N2 group, (2) mock control group, (3) H9N2+carnosine group and (4) carnosine control group. The H9N2 group mice were inoculated intranasally with A/Swine/Hebei/012/2008/ (H9N2) virus (100 μl) in allantoic fluid (AF), whilst mock-infected animals were intranasally inoculated with non-infectious AF. Carnosine [10 mg (kg body mass)- 1] was administered orally (100 μl) for 7 days consecutively. The survival rate, lung water content, TNF-α and IL-1β levels, lung histopathology, myeloperoxidase (MPO) activity, and Toll-like receptor (TLR)-4 levels were determined at 2, 4, 6, 8 and 14 days after inoculation. Carnosine treatment effectively decreased the mortality (43 versus 75 %, P < 0.05), significantly ameliorated pathological lesions in lungs and decreased the lung wet/dry mass ratio (P < 0.05). It also inhibited MPO activity, suppressed TNF-α and IL-1β release, decreased the H9N2 viral titre, and markedly inhibited levels of TLR-4 mRNA and protein in the lungs of infected mice (P < 0.05), which supported the use of carnosine for managing severe influenza cases.

Tocilizumab for refractory organising pneumonia associated with Sjögren's disease

Lung involvement in primary Sjögren syndrome occurs in approximately 10-20% of patients. Tocilizumab, an anti-interleukin-6 receptor antibody, has demonstrated efficacy and safety in small series of systemic sclerosis, and systemic lupus erythematosus, but its effect on interstitial lung manifestations of connective tissue diseases is not well known. We report the use of tocilizumab in a refractory organising pneumonia associated with Sjögren's disease. Our observation suggests that tocilizumab could be an alternative therapeutic in refractory organising pneumonia.

N-acetyl-l-cystine (NAC) protects against H9N2 swine influenza virus-induced acute lung injury

The antioxidant N-acetyl-l-cysteine (NAC) had been shown to inhibit replication of seasonal human influenza A viruses. Here, the effects of NAC on H9N2 swine influenza virus-induced acute lung injury (ALI) were investigated in mice. BALB/c mice were inoculated intranasally with 10⁷ 50% tissue culture infective doses (TCID₅₀) of A/swine/HeBei/012/2008/(H9N2) viruses with or without NAC treatments to induce ALI model. The result showed that pulmonary inflammation, pulmonary edema, MPO activity, total cells, neutrophils, macrophages, TNF-α, IL-6, IL-1β and CXCL-10 in BALF were attenuated by NAC. Moreover, our data showed that NAC significantly inhibited the levels of TLR4 protein and TLR4 mRNA in the lungs. Pharmacological inhibitors of TLR4 (E5564) exerted similar effects like those determined for NAC in H9N2 swine influenza virus-infected mice. These results suggest that antioxidants like NAC represent a potential additional treatment option that could be considered in the case of an influenza A virus pandemic.

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NAC protects against H9N2 swine influenza virus-induced acute lung injury (ALI).

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NAC protects against acute lung injury by inactivation of TLR4.

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Eritoran (E5564), a TLR4 antagonist, also protects against acute lung injury.

Herpes Simplex Pneumonia in an Immunocompetent Patient With Progression to Organizing Pneumonia

Background. Organizing pneumonia is an uncommon diffuse interstitial lung disease that affects the terminal and respiratory bronchioles, alveolar ducts, and alveoli. Most cases are idiopathic, but some are associated with infections. We present an uncommon case of organizing pneumonia associated with herpes simplex virus-1 (HSV-1). Case. A 39-year-old man with hypertension presented with dyspnea, fever, and productive cough for 2 weeks. He was treated for 5 days for acute bronchitis as an outpatient with no improvement. His examination revealed mild respiratory distress, O2 saturation 92% on room air, and right sided crackles. Labs included a white blood cell count of 19 300/µL. His chest x-ray showed bilateral infiltrates greater on the right. Bronchoalveolar lavage was positive for HSV-1; transbronchial biopsies showed focal pneumonitis with plentiful intra-alveolar macrophages. His respiratory status progressively deteriorated, and he was intubated for mechanical ventilation. He received 10 days of intravenous (IV) antibiotics and 14 days of IV acyclovir. He was readmitted 10 days later with worsening symptoms and was intubated for respiratory failure. His CT chest showed diffuse, patchy consolidation of both lungs, right more than left. Open lung biopsy showed extensive organizing pneumonia, diffuse alveolar damage, intra-alveolar macrophages, and pleural fibrosis; he was treated with IV corticosteroids. He was extubated after 10 days; within 2 weeks his chest x-ray was markedly improved. Discussion. Organizing pneumonia is usually idiopathic; infection is one of the secondary causes. To our knowledge this is only the second reported case associated with HSV. This association may have important pathogenic and therapeutic implications.

A nonpathogenic duck-origin H9N2 influenza A virus adapts to high pathogenicity in mice

H9N2 influenza viruses continue to circulate in wild birds and poultry in Eurasian countries and have repeatedly infected mammals, including pigs and humans, posing a significant threat to public health. To understand the adaptation of H9N2 influenza viruses to mammals, we serially passaged a nonpathogenic duck-origin H9N2 influenza virus, A/duck/Jiangsu/1/2008 (DK1), in mouse lungs. Increased virulence was detectable after five sequential passages, and a highly pathogenic mouse-adapted strain (DK1-MA) with a 50% mouse lethal dose of 10(2.37) 50% egg infectious dose was obtained after 18 passages. DK1-MA grew faster and reached significantly higher titers than DK1 in mouse lungs and could sporadically spread to other organs. Moreover, DK1-MA induced a greater magnitude of pulmonary edema and higher levels of inflammatory cellular infiltration in bronchoalveolar lavage fluids than DK1 did. Genomic sequence alignment revealed eight amino acid substitutions (HA-L80F, HA-N193D, NA-A27T, PB2-F404L, PA-D3V, PA-S225R, NP-V105M, M1-A166V) in six viral proteins of DK1-MA compared with DK1 virus. Except for HA-L80F, the other seven substitutions were all located in known functional regions involved in interaction of viral proteins or interaction between the virus and host factors. Taken together, our results suggest that multiple amino acid substitutions may be involved in the adaptation of H9N2 avian influenza virus to mice, resulting in lethal infection, enhanced viral replication, severe pulmonary edema, and excessive inflammatory cellular infiltration in lungs. These observations provide helpful insights into the pathogenic potential of H9N2 avian influenza viruses that could pose threats to human health in the future.

Reovirus-associated meningoencephalomyelitis in baboons

Baboon orthoreovirus (BRV) is associated with meningoencephalomyelitis (MEM) among captive baboons. Sporadic cases of suspected BRV-induced MEM have been observed at Southwest National Primate Research Center (SNPRC) for the past 20 years but could not be confirmed due to lack of diagnostic assays. An immunohistochemistry (IHC)-based assay using an antibody against BRV fusion-associated small transmembrane protein p15 and a conventional polymerase chain reaction (PCR)-based assay using primers specific for BRV were developed to detect BRV in archived tissues. Sixty-eight cases of suspected BRV-induced MEM from 1989 through 2010 were tested for BRV, alphavirus, and flavivirus by IHC. Fifty-nine of 68 cases (87%) were positive for BRV by immunohistochemistry; 1 tested positive for flavivirus (but was negative for West Nile virus and St Louis encephalitis virus by real-time PCR), and 1 virus isolation (VI) positive control tested negative for BRV. Sixteen cases (9 BRV-negative and 7 BRV-positive cases, by IHC), along with VI-positive and VI-negative controls, were tested by PCR for BRV. Three (of 9) IHC-negative cases tested positive, and 3 (of 7) IHC-positive cases tested negative by PCR for BRV. Both IHC and PCR assays tested 1 VI-positive control as negative (sensitivity: 75%). This study shows that most cases of viral MEM among baboons at SNPRC are associated with BRV infection, and the BRV should be considered a differential diagnosis for nonsuppurative MEM in baboons.

Respiratory infection of mice with mammalian reoviruses causes systemic infection with age and strain dependent pneumonia and encephalitis

BACKGROUND

Because mammalian reoviruses are isolated from the respiratory tract we modeled the natural history of respiratory infection of adult and suckling mice with T1 Lang (T1L) and T3 Dearing (T3D) reoviruses.

METHODS

Adult and suckling Balb/c mice were infected by the intranasal route and were assessed for dose response of disease as well as viral replication in the lung and other organs. Viral antigen was assessed by immunofluorescence and HRP staining of tissue sections and histopathology was assessed on formalin fixed, H + E stained tissue sections.

RESULTS

Intranasal infection of adult mice resulted in fatal respiratory distress for high doses (10(7) pfu) of T1L but not T3D. In contrast both T1L and T3D killed suckling mice at moderate viral dosages (10(5) pfu) but differed in clinical symptoms where T1L induced respiratory failure and T3D caused encephalitis. Infections caused transient viremia that resulted in spread to peripheral tissues where disease correlated with virus replication, and pathology. Immunofluorescent staining of viral antigens in the lung showed reovirus infection was primarily associated with alveoli with lesser involvement of bronchiolar epithelium. Immunofluorescent and HRP staining of viral antigens in brain showed infection of neurons by T3D and glial cells by T1L.

CONCLUSIONS

These mouse models of reovirus respiratory infection demonstrated age and strain dependent disease that are expected to be relevant to understanding and modulating natural and therapeutic reovirus infections in humans.

Curcumin modulates the inflammatory response and inhibits subsequent fibrosis in a mouse model of viral-induced acute respiratory distress syndrome

Acute Respiratory Distress Syndrome (ARDS) is a clinical syndrome characterized by diffuse alveolar damage usually secondary to an intense host inflammatory response of the lung to a pulmonary or extrapulmonary infectious or non-infectious insult often leading to the development of intra-alveolar and interstitial fibrosis. Curcumin, the principal curcumoid of the popular Indian spice turmeric, has been demonstrated as an anti-oxidant and anti-inflammatory agent in a broad spectrum of diseases. Using our well-established model of reovirus 1/L-induced acute viral pneumonia, which displays many of the characteristics of the human ALI/ARDS, we evaluated the anti-inflammatory and anti-fibrotic effects of curcumin. Female CBA/J mice were treated with curcumin (50 mg/kg) 5 days prior to intranasal inoculation with 10(7)pfu reovirus 1/L and daily, thereafter. Mice were evaluated for key features associated with ALI/ARDS. Administration of curcumin significantly modulated inflammation and fibrosis, as revealed by histological and biochemical analysis. The expression of IL-6, IL-10, IFNγ, and MCP-1, key chemokines/cytokines implicated in the development of ALI/ARDS, from both the inflammatory infiltrate and whole lung tissue were modulated by curcumin potentially through a reduction in the phosphorylated form of NFκB p65. While the expression of TGFß1 was not modulated by curcumin, TGFß Receptor II, which is required for TGFß signaling, was significantly reduced. In addition, curcumin also significantly inhibited the expression of α-smooth muscle actin and Tenascin-C, key markers of myofibroblast activation. This data strongly supports a role for curcumin in modulating the pathogenesis of viral-induced ALI/ARDS in a pre-clinical model potentially manifested through the alteration of inflammation and myofibroblast differentiation.

Lung Contusion: A Clinico-Pathological Entity with Unpredictable Clinical Course

Lung contusion is an entity involving injury to the alveolar capillaries, without any tear or cut in the lung tissue. This results in accumulation of blood and other fluids within the lung tissue. The excess fluid interferes with gas exchange leading to hypoxia. The pathophysiology of lung contusion includes ventilation/perfusion mismatching, increased intrapulmonary shunting, increased lung water, segmental lung damage, and a loss of compliance. Clinically, patient's presents with hypoxiemia, hypercarbia and increase in laboured breathing. Patients are treated with supplemental oxygen and mechanical ventilation whenever indicated. Treatment is primarily supportive. Computed tomography (CT) is very sensitive for diagnosing pulmonary contusion. Pulmonary contusion occurs in 25-35% of all blunt chest traumas.

Resolution of immune response by recombinant transforming growth factor-beta (rTGF-β) during influenza A virus infection

BACKGROUND & OBJECTIVES

Replication of influenza A virus in the respiratory tract leads to cell damage and liberation of cytokines and chemokines. The in vivo cytokine induction and modulation by recombinant transforming growth factor- β1 (rTGF-β1) has not been studied. Therefore, in the present study the effect of rTGF-β1, a potent immunomodulatory cytokine which has anti-inflammatory properties and downregulates the release of inflammatory molecules, against influenza-virus infection in the airway of mice was investigated.

METHODS

rTGF-β1 was administered intravenously to mice with concomitant intranasal infection of influenza A/Udorn/317/72 (H3N2) virus, and the survival rate, virus titre, histopathological changes and levels of factors regulating inflammation in the airway fluid were analysed.

RESULT

The immune response to influenza A virus was characterized by an influx of both macrophages and lymphocytes into the lungs of the infected host. rTGF-β1 significantly suppressed virus multiplication and improved the survival rate of mice. rTGF-β1 downregulated infiltration of neutrophils and the release of inflammatory molecules, such as interferon-gamma (IFN-γ), interleukin-1 β (IL-1β) and stimulated release of IL-10 that potentiates anti-inflammatory response into airway.

INTERPRETATION & CONCLUSIONS

A generalized pulmonary inflammation does not contribute to viral clearance but represents an immunological background within which antiviral immunity operates. Treatment with rTGF-β1 reduced macrophage count and neutrophils influx in lungs of infected mice.

Cryptogenic Organizing Pneumonia in Tomm5–/– Mice

Almost all mitochondrial proteins are encoded in the nuclear DNA and synthesized in the cytosol as pre-proteins. There is a protein translocase located in the mitochondrial outer membrane that transports mitochondrial pre-proteins into mitochondria. The central component of this translocase of the outer mitochondrial membrane (TOMM) complex is TOMM40, and TOMM5 is one of three small subunits associated with TOMM40. Translocase of outer mitochondrial membrane 5 homolog ( Tomm5–/–) knockout mice demonstrated an unexpected lung-specific phenotype characterized by widespread intra-alveolar fibrosis. Although TOMM5-deficient mice tested normal in a very broad range of phenotyping assays, they displayed histopathological lesions in the lung that were consistent with those reported in humans with cryptogenic organizing pneumonia (COP), which is also known as bronchiolitis obliterans organizing pneumonia (BOOP). The lesions had a patchy distribution in the lung and were characterized by the presence of intraluminal fibrogenic buds consisting of fibroblasts and myofibroblasts embedded in a loose connective tissue matrix that occupied the lumina of alveoli and alveolar ducts, with preservation of underlying alveolar architecture. In addition to macrophages, which were numerous in affected and surrounding alveoli, eosinophils comprised the most common and widespread inflammatory cell. Taken together, the findings in Tomm5–/– mice provide yet another example of the value of histopathology as a baseline assay in high-throughput phenotyping systems.

Histopathological analogies in chronic pulmonary lesions between cattle and humans: basis for an alternative animal model

Most of the natural cases of pneumonia in feedlot cattle are characterized by a longer clinical course due to chronic lung lesions. Microscopically, these lesions include interstitial fibroplasia, bronchitis, bronchiectasis, bronchiolitis obliterans, and epithelial metaplasia of the airways. Herein, the aim was to review, under a medical perspective, the pathologic mechanisms operating in these chronic pneumonic lesions in calves. Based on the similarities of these changes to those reported in bronchiolitis obliterans/organising pneumonia (BO/OP) and chronic obstructive pulmonary disease (COPD) in human beings, calves are proposed as an alternative animal model.

Acute respiratory distress syndrome induced by a swine 2009 H1N1 variant in mice

Background

Acute respiratory distress syndrome (ARDS) induced by pandemic 2009 H1N1 influenza virus has been widely reported and was considered the main cause of death in critically ill patients with 2009 H1N1 infection. However, no animal model has been developed for ARDS caused by infection with 2009 H1N1 virus. Here, we present a mouse model of ARDS induced by 2009 H1N1 virus.

Methodology Principal Findings

Mice were inoculated with A/swine/Shandong/731/2009 (SD/09), which was a 2009 H1N1 influenza variant with a G222D mutation in the hemagglutinin. Clinical symptoms were recorded every day. Lung injury was assessed by lung water content and histopathological observation. Arterial blood gas, leukocyte count in the bronchial alveolar lavage fluid and blood, virus titers, and cytokine levels in the lung were measured at various times post-inoculation. Mice infected with SD/09 virus showed typical ARDS symptoms characterized by 60% lethality on days 8–10 post-inoculation, highly edematous lungs, inflammatory cellular infiltration, alveolar and interstitial edema, lung hemorrhage, progressive and severe hypoxemia, and elevated levels of proinflammatory cytokines and chemokines.

Conclusions/Significance

These results suggested that we successfully established an ARDS mouse model induced by a virulent 2009 H1N1 variant without previous adaptation, which may be of benefit for evaluating the pathogenesis or therapy of human ARDS caused by 2009 H1N1 virus.

Bronchiolitis obliterans organizing pneumonia, 25 years: a variety of causes, but what are the treatment options?

Bronchiolitis obliterans organizing pneumonia is an inflammatory lung disease involving the distal bronchioles, respiratory bronchioles, bronchiolar ducts and alveoli. Its cause is generally unknown, but there are several known causes and associated systemic diseases. The clinical features include cough, shortness of breath and bilateral crackles. The vital capacity is slightly decreased, and the diffusing capacity is moderately to severely decreased. The high-resolution chest CT scan shows bilateral ground-glass opacities with air bronchograms and triangular, pleura-based opacities. Corticosteroid therapy is the best treatment option. The outcome of patients suffering from bronchiolitis obliterans organizing pneumonia is good, as up to 80% of individuals will be cured.

Stem cells in clinical practice: applications and warnings

Stem cells are a relevant source of information about cellular differentiation, molecular processes and tissue homeostasis, but also one of the most putative biological tools to treat degenerative diseases. This review focuses on human stem cells clinical and experimental applications. Our aim is to take a correct view of the available stem cell subtypes and their rational use in the medical area, with a specific focus on their therapeutic benefits and side effects. We have reviewed the main clinical trials dividing them basing on their clinical applications, and taking into account the ethical issue associated with the stem cell therapy.

Increased expression of tumor necrosis factor receptors in cryptogenic organizing pneumonia

BACKGROUND

TNF receptors (TNFR1 and TNFR2) and Fas belong to the system of apoptosis-signalling receptor molecules and may play a role in the pathogenesis of interstitial lung disease. Patients with cryptogenic organizing pneumonia (COP) usually respond well to corticosteroids, in contrast to those with idiopathic pulmonary fibrosis (IPF). This may be due to the different pathogenesis.

METHODS

The expression of TNFR1, TNFR2 and Fas on bronchoalveolar lavage (BAL) macrophages and lymphocytes was analysed in 9 patients with COP, 10 with IPF and 12 controls. The production of soluble TNFR1, 2 and TNF-α by alveolar macrophages was measured by ELISA.

RESULTS

TNFR1 and Fas expression on alveolar macrophages was significantly higher in COP than in controls and IPF. The expression of TNFR2 on alveolar macrophages was also increased in COP compared to controls. The expression of TNFR2 and Fas on lymphocytes was significantly higher in COP than in IPF and controls. In addition, the expression of TNFR1, TNFR2 and Fas on BAL cells correlated positively with BAL lymphocytes (p < 0.05 or p < 0.01). The production of sTNFR1 and 2 and TNF-α by macrophages in vitro was significantly increased in patients with COP compared to IPF and controls, spontaneously or with LPS stimulation (p < 0.05 or p < 0.01).There was a positive correlation between the spontaneous production of sTNFR2 and TNF-α (r = 0.494, p < 0.01).

CONCLUSIONS

This study showed an increased expression of TNF receptors and Fas on BAL cells in COP that may be indicative of the local inflammatory activity in the lung. The biologic effects of this expression needs further investigation.

Clinical features of late onset non-infectious pulmonary complications following pediatric allogeneic hematopoietic stem cell transplantation

BACKGROUND

Late onset non-infectious pulmonary complications (LONIPCs) are major causes of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). We evaluated the incidence and the outcomes of LONIPCs in children who underwent allo-HSCT.

METHODS

Data for 143 children who underwent allo-HSCT at Asan Medical Center between April 2002 and April 2009 were reviewed, and the 127 who survived more than three months were enrolled.

RESULTS

Eleven (8.7%) developed LONIPCs at a median eight months (range 3-14 months) after allo-HSCT, presenting with cough and dyspnea. Six had bronchiolitis obliterans and five had idiopathic pneumonia syndrome. FVC declined more significantly in LONIPC than in non-LONIPC patients three months after HSCT. A significant risk factor for the development of LONIPCs was chronic graft-versus-host disease (GVHD) (p = 0.002). At a median follow-up of 36 months, the three-yr overall survival rate in LONIPC patients was significantly lower than that of non-LONIPC patients (37.4% vs. 72.7%, p = 0.02). The major cause of death was respiratory failure.

CONCLUSIONS

Along with chronic GVHD, deterioration of pulmonary function at three months after HSCT may help in the early identification of patients at risk of subsequent LONIPCs. Considering the poor prognosis of LONIPC, strategies should be aimed at their prevention.

Bronchiolitis obliterans organizing pneumonia in Swine associated with porcine circovirus type 2 infection

Bronchiolitis obliterans organizing pneumonia (BOOP) is a chronic respiratory disease. Although the pathogenesis of BOOP is still incompletely understood, BOOP is responsive to steroids and has a good prognosis. In our five pigs with chronic postweaning multisystemic wasting syndrome (PMWS), typical BOOP lesions were revealed. All five porcine lungs showed typical intraluminal plugs, and porcine circovirus type 2 (PCV2) was identified. They also exhibited similar pathologic findings such as proliferation of type II pneumocytes and myofibroblasts (MFBs), extracellular collagen matrix (ECM) deposition, and fragmentation of elastic fibers. MFBs migration correlative molecules, for instance, gelatinase A, B and osteopontin, appeared strongly in the progressing marginal area of polypoid intraluminal plugs of fibrotic lesion. These molecules colocalized with the active MFBs. Both gelatinase activity and intercellular level of active MFBs were significantly increased (P < .05). Porcine chronic bronchopneumonia leads to BOOP and it is associated with PCV2 persistent infection. Swine BOOP demonstrates similar cellular constituents with human BOOP. Perhaps their molecular mechanisms of pathogenesis operate in a similar way. Thus we infer that the swine BOOP can be considered as a potential animal model for human BOOP associated with natural viral infection. Moreover, it is more convenient to obtain samples.

Differential role of the Fas/Fas ligand apoptotic pathway in inflammation and lung fibrosis associated with reovirus 1/L-induced bronchiolitis obliterans organizing pneumonia and acute respiratory distress syndrome

Bronchiolitis obliterans organizing pneumonia (BOOP) and acute respiratory distress syndrome (ARDS) are two clinically and histologically distinct syndromes sharing the presence of an inflammatory and fibrotic component. Apoptosis via the Fas/Fas ligand (FasL) pathway plays an important role in the development of acute lung injury and fibrosis characteristic of these and other pulmonary inflammatory and fibrotic syndromes. We evaluated the role of apoptosis via the Fas/FasL pathway in the development of pulmonary inflammation and fibrosis in reovirus 1/L-induced BOOP and ARDS. CBA/J mice were intranasally inoculated with saline, 1 x 10(6) (BOOP), or 1 x 10(7) (ARDS) PFU reovirus 1/L, and evaluated at various days postinoculation for in situ apoptosis by TUNEL analysis and Fas/FasL expression. Our results demonstrate the presence of apoptotic cells and up-regulation of Fas/FasL expression in alveolar epithelium and in infiltrating cells during the inflammatory and fibrotic stages of both reovirus 1/L-induced ARDS and BOOP. Treatment of mice with the caspase 8 inhibitor, zIETD-fmk, inhibited apoptosis, inflammation, and fibrotic lesion development in reovirus 1/L-induced BOOP and ARDS. However, CBA/KlJms-Fas(lpr-cg)/J mice, which carry a point mutation in the Fas cytoplasmic region that abolishes the ability of Fas to transduce an apoptotic signal, do not develop pulmonary inflammation and fibrotic lesions associated with reovirus 1/L-induced BOOP, but still develop inflammation and fibrotic lesions associated with reovirus 1/L-induced ARDS. These results suggest a differential role for the Fas/FasL apoptotic pathway in the development of inflammation and fibrotic lesions associated with BOOP and ARDS.

Acute respiratory distress syndrome induced by H9N2 virus in mice

H9N2 avian influenza viruses have repeatedly caused infections in swine and humans in some countries. The purpose of the present study was to evaluate the pulmonary pathology caused by H9N2 viral infection in mice. Six- to eight-week-old BALB/c mice were infected intranasally with 1 × 10⁴ MID₅₀ of A/Chicken/Hebei/4/2008(H9N2) virus. Clinical signs, pathological changes and viral replication in lungs, arterial blood gas, and cytokines in bronchoalveolar lavage fluid (BALF) were observed at different time points after infection. A control group was infected intranasally with noninfectious allantoic fluid. H9N2-infected mice exhibited severe respiratory syndrome, with a mortality rate of 60%. Gross observations showed that infected lungs were highly edematous. Major histopathological changes in infected lungs included diffuse pneumonia and alveolar damage, with neutrophil-dominant inflammatory cellular infiltration, interstitial and alveolar edema, hemorrhage, and severe bronchiolitis/peribronchiolitis. In addition, H9N2 viral infection resulted in severe progressive hypoxemia, lymphopenia, and a significant increase in neutrophils, tumor necrosis factor-α and interleukin-6 in BALF. The features described above satisfy the criteria for acute respiratory distress syndrome (ARDS). Our data show that H9N2 viral infection resulted in ARDS in mice, and this may facilitate studies of the pathogenesis of future potential H9N2 disease in humans.

Lung contusion: inflammatory mechanisms and interaction with other injuries

This article reviews current animal models and laboratory studies investigating the pathophysiology of lung contusion (LC), a common and severe condition in patients with blunt thoracic trauma. Emphasis is on studies elucidating cells, mediators, receptors, and processes important in the innate pulmonary inflammatory response that contribute to LC injury. Surfactant dysfunction in the pathogenesis of LC is also discussed, as is the potential role of epithelial cell or neutrophil apoptosis. Studies examining combination injuries where LC is exacerbated by secondary insults such as gastric aspiration in trauma patients are also noted. The need for continuing mechanism-based research to further clarify the pathophysiology of LC injury, and to define and test potential therapeutic interventions targeting specific aspects of inflammation or surfactant dysfunction to improve clinical outcomes in patients with LC, is also emphasized.

Late-onset non-infectious pulmonary complications following allogeneic hematopoietic stem cell transplantation in children

Late-onset non-infectious pulmonary complications (LONIPCs) that arise beyond 3 months after allogeneic hematopoietic SCT include bronchiolitis obliterans (BO), bronchiolitis obliterans with organizing pneumonia (BOOP) and idiopathic pneumonia syndrome (IPS). We retrospectively analyzed the incidence and outcome of LONIPCs among pediatric hematopoietic SCT recipients. We included 97 patients who survived for more than 3 months among the 114 who underwent allogeneic hematopoietic SCT between April 1997 and May 2007. Of the 97 enrolled patients, 10 (10.3%) developed LONIPCs at a median of 187 days after hematopoietic SCT (range, 123-826 days). Of the 10 patients with LONIPCs, eight had BO and two had IPS. Multivariate analysis showed that the onset of LONIPCs was associated with high-risk underlying disease and extensive chronic GVHD (hazard ratio, 5.42 (95% confidence interval, 1.36-21.7) and hazard ratio, 11.7 (95% confidence interval, 2.40-57.1), respectively). Only two patients responded to therapy with steroids and six of the 10 patients died. The 5-year OS rate was significantly lower among patients with, than without LONIPCs (28.0 vs 87.2%, P=0.000). Considering that we are lacking optimal therapies for LONIPCs, strategies aimed at the prevention of LONIPCs should be attempted.

Diffuse alveolar lesion in BALB/c mice induced with human reovirus BYD1 strain and its potential relation with SARS

The objective of this study was to investigate the pathogenicity and associated lesions of a new reovirus (ReoV) isolated from patients with Severe Acute Respiratory Syndrome (SARS) in China. Twenty-five four-week-old BALB/c female mice inoculated intranasally with either ReoV (strain BYD1) alone, or ReoV combined with SARS-CoV (strain BJF) displayed ejecting fur and loss of body weight compared with control animals. ReoV and SARS-CoV were isolated from most postmortem tissues. The histopathological features of ReoV infected animals consisted of diffuse alveolar damage, with scattered hemorrhage, hyaline membrane formation and interstitial pneumonia. A typical type II pneumocyte hyperplasia and fibrogranulomatous tissue formation in the alveolar septae were observed both in the animals inoculated simultaneously with these two viruses and in the animals inoculated firstly with SARS-CoV, followed by ReoV. The animals inoculated firstly with ReoV, followed with SARS-CoV displayed scattered hemorrhage in the alveolar septa. Furthermore, other lesions in above two combination groups included depletion of lymphocytes in the germinal center of lymph nodes in the lung hilus and the spleen, hemorrhagic necrosis in white pulp of spleen, hydroid degeneration, and fatty degeneration in the liver and kidney. Mice induced with SARS-CoV alone did not display clinical signs, characteristically hyaline membrane formation, hemorrhage and early pulmonary fibrosis in lung tissue. This study demonstrated that the newly isolated ReoV might be a virulent pathogen for BALB/c mice. Mice infected firstly with SARS-CoV, followed with ReoV developed a typical diffuse alveolar lesion.

Bronchiolitis obliterans syndrome (BOS), bronchiolitis obliterans organizing pneumonia (BOOP), and other late-onset noninfectious pulmonary complications following allogeneic hematopoietic stem cell transplantation

Pulmonary dysfunction is a significant complication following allogeneic hematopoietic stem cell transplantation (HSCT), and is associated with significant morbidity and mortality. Effective antimicrobial prophylaxis and treatment strategies have increased the incidence of noninfectious lung injury, which can occur in the early posttransplant period or in the months and years that follow. Late-onset noninfectious pulmonary complications are frequently encountered, but diagnostic criteria and terminology for these disorders can be confusing and therapeutic approaches are suboptimal. As a consequence, inaccurate diagnosis of these conditions may hamper the appropriate data collection, enrollment into clinical trials, and appropriate patient care. The purpose of this review is to clarify the pathogenesis and diagnostic criteria of representative conditions, such as bronchiolitis obliterans syndrome and bronchiolitis obliterans organizing pneumonia, and to discuss the appropriate diagnostic strategies and treatment options.

Lichenoid paraneoplastic pemphigus in the absence of detectable antibodies

Paraneoplastic pemphigus (PNP) has been described as an antibody-mediated mucocutaneous disease occurring almost exclusively in patients with lymphocytic neoplasms. We describe 4 patients with the clinical features of the lichenoid variant of PNP in the absence of detectable autoantibodies. On the basis of these findings, we conclude that the spectrum of PNP likely includes patients with disease predominantly or exclusively mediated by cytotoxic T cells rather than autoantibodies. The pathophysiology and range of PNP disease are likely more complex than was initially believed.

[Therapy for idiopathic interstitial pneumonias: steroids--and what else?]

Recently, the classification of diffuse parenchymal lung diseases was revised. Based on histologic criteria, six different syndromes of idiopathic interstitial pneumonias were defined in this new system. Several studies have shown that this classification is indeed of clinical relevance. Furthermore, immunological studies have revealed different pathomechanisms for the distinct diseases. Different treatment strategies have been developed for each class of idiopathic interstitial pneumonia. While in T-cell dependent disorders the benefit of immunosuppressive treatment has been described, in disorders with predominately fibrotic remodeling new treatment options are urgently needed, and only lung transplantation has been shown to improve mortality.

Acute respiratory distress syndrome induced by avian influenza A (H5N1) virus in mice

RATIONALE AND OBJECTIVE

The acute respiratory distress syndrome (ARDS) caused by avian influenza H5N1 viral infection has been reported in many humans since this virus was found to infect humans in Hong Kong in 1997, but no studies regarding an animal model of ARDS with H5N1 viral infection have been found in the literature. Here we present a mouse model of ARDS induced by H5N1 virus.

METHODS

Six- to 8-wk-old BALB/c mice were inoculated intranasally (50 micro l) with 1 x 10(2) 50% mouse infectious doses of A/Chicken/Hebei/108/2002 (H5N1) virus. Lung injury was assessed by observation of lung water content and histopathology. Arterial blood gas, white blood cell count in bronchial alveolar lavage fluid, and tumor necrosis factor-alpha and interleukin-6 in bronchoalveolar lavage fluid and serum were measured at the indicated time points.

RESULTS

Our data showed that H5N1 viral infection in mice resulted in typical ARDS, which was characterized by the following features: (1) about 80% of mice (13 of 16) dead on Days 6 to 8 postinoculation; (2) highly edematous lungs and dramatically increased lung wet:dry weight ratios and lung wet weight:body weight ratios; (3) inflammatory cellular infiltration, alveolar and interstitial edema, and hemorrhage in lungs; (4) progressive and severe hypoxemia; and (5) significant increase in neutrophils, tumor necrosis factor-alpha, and interleukin-6 in BALF.

CONCLUSION

These results suggested that we successfully established a mouse model of ARDS with H5N1 viral infection, which may benefit further investigation into the pathogenesis of human ARDS induced by H5N1 virus.

T-2 toxin impairment of enteric reovirus clearance in the mouse associated with suppressed immunoglobulin and IFN-gamma responses

Trichothecenes are exquisitely toxic to the gastrointestinal (GI) tract and leukocytes and thus are likely to impair gut immunity. The purpose of this research was to test the hypothesis that the Type A trichothecene T-2 toxin interferes with the gut mucosal immune response to enteric reovirus infection. Mice were exposed i.p. first to 1.75 mg/kg bw T-2 and then 2 h later with 3 × 10⁷ plaque-forming units of reovirus serotype 1, strain Lang (T1/L). As compared to vehicle-treated control, T-2-treated mice had dramatically elevated intestinal plaque-forming viral titers after 5 days and failed to completely clear the virus from intestine by 10 days. Levels of reovirus λ2 core spike (L2 gene) RNA in feces in T-2-treated mice were significantly higher at 1, 3, 5, and 7 days than controls. T-2 potentiated L2 mRNA expression in a dose-dependent manner with as little as 50 μg/kg of the toxin having a potentiative effect. T-2 exposure transiently suppressed induction of reovirus-specific IgA in feces (6 and 8 days) as well as specific IgA and IgG_2a in serum (5 days). This suppression corresponded to decreased secretion of reovirus-specific IgA and IgG_2a in Peyer's patch (PP) and lamina propria fragment cultures prepared 5 days after infection. T-2 suppressed IFN-γ responses in PP to reovirus at 3 and 7 days as compared to infected controls whereas IL-2 mRNA concentrations were unaffected. PP IL-6 mRNA levels were increased 2-fold 2 h after T-2 treatment, but no differences between infected T-2-exposed and infected vehicle-treated mice were detectable over the next 7 days. Overall, the results suggest that T-2 toxin increased both the extent of GI tract reovirus infection and fecal shedding which corresponded to both suppressed immunoglobulin and IFN-γ responses.

The evolution of isolated bilateral lung contusion from blunt chest trauma in rats: cellular and cytokine responses

Lung contusion is the leading cause of death from blunt thoracic trauma in adults, but its mechanistic pathophysiology remains unclear. This study uses a recently developed rat model to investigate the evolution of inflammation and injury in isolated lung contusion. Bilateral lung contusion with minimal cardiac trauma was induced in 54 anesthetized rats by dropping a 0.3-kg hollow cylindrical weight onto a precordial shield (impact energy, 2.45 Joules). Arterial oxygenation, pressure-volume (P-V) mechanics, histology, and levels of erythrocytes, leukocytes, albumin, and inflammatory mediators in bronchoalveolar lavage (BAL) were assessed at 8 min, at 4, 12, 24, and 48 h, and at 7 days after injury. The role of neutrophils in the evolution of inflammatory injury was also specifically studied by depleting these cells with intravenous vinblastine before lung contusion. Arterial oxygenation was severely reduced at 8 min to 24 h postcontusion, but became almost normal by 48 h. Levels of erythrocytes, leukocytes, and albumin in BAL were increased at <or=24 h, and returned toward normal by 48 h. Deficits in P-V mechanics were most apparent at 24 h postcontusion. Levels of macrophage inflammatory polypeptide-2, cytokine-induced neutrophil chemoattractant-1, and interleukin 6 in BAL peaked at 24 h, whereas monocyte chemoattractant protein-1 and interleukin 1beta peaked at 24 to 48 h postcontusion. Histology showed early hemorrhagic injury (8 min-12 h), with neutrophilic infiltration at 24 h and areas of bronchiolitis obliterans organizing pneumonia-associated fibrosis at 7 days. Vinblastine-treated neutropenic rats had significantly reduced lung injury based on total lung volume at 4 h and on BAL albumin levels at 24 h postcontusion. Inflammatory injury from isolated bilateral lung contusion in rats is most severe in the acute period (8 min-24 h) after initial blunt trauma, and includes a component of neutrophil-dependent pathology.