The Tuberculous Granuloma and Preexisting Immunity.

Pulmonary granulomas are widely considered the epicenters of the immune response to Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB). Recent animal studies have revealed factors that either promote or restrict TB immunity within granulomas. These models, however, typically ignore the impact of preexisting immunity on cellular organization and function, an important consideration because most TB probably occurs through reinfection of previously exposed individuals. Human postmortem research from the pre-antibiotic era showed that infections in Mtb-naïve individuals (primary TB) versus those with prior Mtb exposure (postprimary TB) have distinct pathologic features. We review recent animal findings in TB granuloma biology, which largely reflect primary TB. We also discuss our current understanding of postprimary TB lesions, about which much less is known. Many knowledge gaps remain, particularly regarding how preexisting immunity shapes granuloma structure and local immune responses at Mtb infection sites.

Impact of Respiratory Syncytial Virus Infection on Host Functions: Implications for Antiviral Strategies.

Respiratory syncytial virus (RSV) is one of the leading causes of viral respiratory tract infection in infants, the elderly, and the immunocompromised worldwide, causing more deaths each year than influenza. Years of research into RSV since its discovery over 60 yr ago have elucidated detailed mechanisms of the host-pathogen interface. RSV infection elicits widespread transcriptomic and proteomic changes, which both mediate the host innate and adaptive immune responses to infection, and reflect RSV's ability to circumvent the host stress responses, including stress granule formation, endoplasmic reticulum stress, oxidative stress, and programmed cell death. The combination of these events can severely impact on human lungs, resulting in airway remodeling and pathophysiology. The RSV membrane envelope glycoproteins (fusion F and attachment G), matrix (M) and nonstructural (NS) 1 and 2 proteins play key roles in modulating host cell functions to promote the infectious cycle. This review presents a comprehensive overview of how RSV impacts the host response to infection and how detailed knowledge of the mechanisms thereof can inform the development of new approaches to develop RSV vaccines and therapeutics.

Aspecific binding of anti-NK1.1 antibodies on myeloid cells in an experimental model for malaria-associated acute respiratory distress syndrome.

BACKGROUND: Conventional natural killer (cNK) cells play an important role in the innate immune response by directly killing infected and malignant cells and by producing pro- and anti-inflammatory cytokines. Studies on their role in malaria and its complications have resulted in conflicting results. METHODS: Using the commonly used anti-NK1.1 depletion antibodies (PK136) in an in-house optimized experimental model for malaria-associated acute respiratory distress syndrome (MA-ARDS), the role of cNK cells was investigated. Moreover, flow cytometry was performed to characterize different NK cell populations. RESULTS: While cNK cells were found to be dispensable in the development of MA-ARDS, the appearance of a NK1.1+ cell population was observed in the lungs upon infection despite depletion with anti-NK1.1. Detailed characterization of the unknown population revealed that this population consisted of a mixture of monocytes and macrophages that bind the anti-NK1.1 antibody in an aspecific way. This aspecific binding may occur via Fcγ receptors, such as FcγR4. In contrast, in vivo depletion using anti-NK1.1 antibodies was proved to be specific for cNK cells. CONCLUSION: cNK cells are dispensable in the development of experimental MA-ARDS. Moreover, careful flow cytometric analysis, with a critical mindset in relation to potential aspecific binding despite the use of commercially available Fc blocking reagents, is critical to avoid misinterpretation of the results.

Accelerated silicosis in sandblasters: Pathology, mineralogy, and clinical correlates.

BACKGROUND: With increasing reports of accelerated and acute silicosis, PMF, and autoimmune disease among coal miners and silica-exposed countertop workers, we present previously incompletely-described pulmonary pathology of accelerated silicosis and correlations with mineralogy, radiography, and disease progression in 46 Texas oilfield pipe sandblasters who were biopsied between 1988 and 1995. METHODS: Worker examinations included pulmonary function tests, chest X-ray (CXR), high-resolution computed tomography (HRCT), and Gallium-67 scans. Quantitative mineralogic analysis of pulmonary parenchymal burden of silica, silicates, and metal particles used scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM EDS). RESULTS: Workers had clinical deterioration after <10 years exposure in dusty workplaces. Although initial CXR was normal in 54%, Gallium-67 scans were positive in 68% of those with normal CXR, indicating pulmonary inflammation. The histology of accelerated silicosis is diffuse interstitial infiltration of macrophages filled with weakly birefringent particles with or without silicotic nodules or alveolar proteinosis. Lung silica concentrations were among the highest in our database, showing a dose-response relationship with CXR, HRCT, and pathologic changes (macrophages, fibrosis, and silicotic nodules). Radiographic scores and diffusing capacity worsened during observation. Silica exposure was intensified, patients presented younger, with shorter exposure, more severe clinical abnormalities, higher lung particle burdens, and more rapid progression in a subset of patients exposed to recycled blasting sand. CONCLUSIONS: Accelerated silicosis may present with a normal CXR despite significant histopathology. Multivariable analyses showed silica, and not other particles, is the driver of observed radiologic, physiologic, and histologic outcomes. Eliminating this preventable disease requires higher physician, public health, and societal awareness.

Correlation exploration among CT imaging, pathology and genotype of pulmonary ground-glass opacity.

To analyse the clinical features, imaging manifestation, pathological typing and genetic testing results of patients undergoing surgery for ground-glass opacity (GGO) nodules, and explore the reasonable diagnosis and treatment program for GGO patients as to provide the basis for the establishment of GGO treatment process. This study is an exploratory study. 465 cases with GGO confirmed by HRCT, undergoing surgery and approved by pathologic diagnosis in Shanghai pulmonary hospital were enrolled in this study. All the patients with GGO were cases with single lesion. The relationship between the clinical, imaging, pathological and molecular biological data of single GGO were statistically studied. (1) Among 465 cases, the median age was 58 years and females were 315 (67.7%); there were 397 (85.4%) non-smoking, and 354 cases (76.1%) had no clinical symptoms. There were 33 cases of benign and 432 cases of malignant GGO. Significant differences were observed on the size, vacuole sign, pleural indentation and blood vessel sign of GGO between two groups (p < 0.05). Of 230 mGGO, there were no AAH, 13 cases of AIS, 25 cases of MIA and 173 cases of invasive adenocarcinoma. The probability of solid nodules in invasive adenocarcinoma was higher than that in micro invasive carcinoma, and the difference was statistically significant (p < 0.05). 360 cases were followed up with the average follow-up time of 6.05 months, and GGO of 34 cases (9.4%) increased. (2) In 428 adenocarcinoma samples approved by pathologic diagnosis, there were 262 (61.2%) lesions of EGFR mutation, 14 (3.3%) lesions of KRAS mutation, 1 (0.2%) lesion of Braf mutation, 9 (2.1%) lesions of EML4-ALK gene fusion and 2 (0.5%) lesions of ROS1 fusion. The detection rate of gene mutation in mGGO was higher than that of pGGO. During the follow-up period, genetic testing results of 32 GGO showed that EGFR mutation rate was 53.1%, ALK positive rate of 6.3%, KRAS mutation rate of 3.1% and no ros1 and BRAF gene mutation. No statistically significant difference was observed in comparison with unchanged GGO. (3) EGFR mutation rate of invasive adenocarcinoma was the highest (168/228, 73.7%), mainly in the 19Del and L858R point mutations. No KRAS mutation was found in atypical adenoma hyperplasia. No significant difference was observed on the mutation rate of KRAS between different types of GGO (p = 0.811). EML4-ALK fusion gene was mainly detected in invasive adenocarcinoma (7/9). GGO tends to occur in young, non-smoking women. The size of GGO is related to the degree of malignancy. Pleural depression sign, vacuole sign and vascular cluster sign are all characteristic images of malignant GGO. pGGO and mGGO reflect the pathological development of GGO. During the follow-up, it is found that GGO increases and solid components appear, which is the indication of surgical resection. The detection rate of EGFR mutations in mGGO and invasive adenocarcinoma is high. pGGO has heterogeneity in imaging, pathology and molecular biology. Heterogeneity research helps to formulate correct individualized diagnosis and treatment plans.

Circulating markers of extracellular matrix remodelling in severe COVID-19 patients.

BACKGROUND: Abnormal remodelling of the extracellular matrix (ECM) has generally been linked to pulmonary inflammation and fibrosis and may also play a role in the pathogenesis of severe COVID-19. To further elucidate the role of ECM remodelling and excessive fibrogenesis in severe COVID-19, we examined circulating levels of mediators involved in various aspects of these processes in COVID-19 patients. METHODS: Serial blood samples were obtained from two cohorts of hospitalised COVID-19 patients (n = 414). Circulating levels of ECM remodelling mediators were quantified by enzyme immunoassays in samples collected during hospitalisation and at 3-month follow-up. Samples were related to disease severity (respiratory failure and/or treatment at the intensive care unit), 60-day total mortality and pulmonary pathology after 3-months. We also evaluated the direct effect of inactivated SARS-CoV-2 on the release of the different ECM mediators in relevant cell lines. RESULTS: Several of the measured markers were associated with adverse outcomes, notably osteopontin (OPN), S100 calcium-binding protein A12 and YKL-40 were associated with disease severity and mortality. High levels of ECM mediators during hospitalisation were associated with computed tomography thorax pathology after 3-months. Some markers (i.e. growth differential factor 15, galectin 3 and matrix metalloproteinase 9) were released from various relevant cell lines (i.e. macrophages and lung cell lines) in vitro after exposure to inactivated SARS-CoV-2 suggesting a direct link between these mediators and the causal agent of COVID-19. CONCLUSION: Our findings highlight changes to ECM remodelling and particularly a possible role of OPN, S100A12 and YKL-40 in the pathogenesis of severe COVID-19.

Single-Cell Landscape of Lungs Reveals Key Role of Neutrophil-Mediated Immunopathology during Lethal SARS-CoV-2 Infection.

Due to the limitation of human studies with respect to individual difference or the accessibility of fresh tissue samples, how severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection results in pathological complications in lung, the main site of infection, is still incompletely understood. Therefore, physiologically relevant animal models under realistic SARS-CoV-2 infection conditions would be helpful to our understanding of dysregulated inflammation response in lung in the context of targeted therapeutics. Here, we characterized the single-cell landscape in lung and spleen upon SARS-CoV-2 infection in an acute severe disease mouse model that replicates human symptoms, including severe lung pathology and lymphopenia. We showed a reduction of lymphocyte populations and an increase of neutrophils in lung and then demonstrated the key role of neutrophil-mediated lung immunopathology in both mice and humans. Under severe conditions, neutrophils recruited by a chemokine-driven positive feedback produced elevated "fatal signature" proinflammatory genes and pathways related to neutrophil activation or releasing of granular content. In addition, we identified a new Cd177high cluster that is undergoing respiratory burst and Stfahigh cluster cells that may dampen antigen presentation upon infection. We also revealed the devastating effect of overactivated neutrophil by showing the highly enriched neutrophil extracellular traps in lung and a dampened B-cell function in either lung or spleen that may be attributed to arginine consumption by neutrophil. The current study helped our understanding of SARS-CoV-2-induced pneumonia and warranted the concept of neutrophil-targeting therapeutics in COVID-19 treatment. IMPORTANCE We demonstrated the single-cell landscape in lung and spleen upon SARS-CoV-2 infection in an acute severe disease mouse model that replicated human symptoms, including severe lung pathology and lymphopenia. Our comprehensive study revealed the key role of neutrophil-mediated lung immunopathology in SARS-CoV-2-induced severe pneumonia, which not only helped our understanding of COVID-19 but also warranted the concept of neutrophil targeting therapeutics in COVID-19 treatment.

Pulmonary Histopathologic Findings in Pediatric Patients After Hematopoietic Stem Cell Transplantation: An Autopsy Study.

BACKGROUND: Pathologic characterization of pulmonary complications following hematopoietic stem cell transplantation (HSCT) is limited. We describe lung findings in pediatric patients who died following HSCT and attempt to identify potential clinical associations. METHODS: Pathology databases at Texas Children's Hospital and the Children's Hospital of Philadelphia were queried (2013-2018 CHOP and 2017-2018 TCH). Electronic medical records and slides were reviewed. RESULTS: Among 29 patients, 19 received HSCT for hematologic malignancy, 8 for non-malignant hematologic disorders, and 2 for metastatic solid tumors. Twenty-five patients (86%) showed 1 or more patterns of acute and organizing lung injury. Sixty-two percent had microvascular sclerosis, with venous involvement noted in most cases and not correlating with clinical history of pulmonary hypertension, clinical transplant-associated thrombotic microangiopathy, irradiation, or graft-versus-host disease. Features suggestive of graft-versus-host-disease were uncommon: 6 patients had lymphocytic bronchiolitis, and only 2 patients had evidence of bronchiolitis obliterans (both clinically unexpected), both with a mismatched unrelated donor transplant. CONCLUSIONS: Acute and subacute alveolar injury (diffuse alveolar damage or organizing pneumonia) is common in pediatric patients who died following HSCT and is difficult to assign to a specific etiology. Microvascular sclerosis was frequent and did not correlate with a single distinct clinical feature.

Poxvirus-encoded TNF receptor homolog dampens inflammation and protects from uncontrolled lung pathology during respiratory infection.

Ectromelia virus (ECTV) causes mousepox, a surrogate mouse model for smallpox caused by variola virus in humans. Both orthopoxviruses encode tumor necrosis factor receptor (TNFR) homologs or viral TNFR (vTNFR). These homologs are termed cytokine response modifier (Crm) proteins, containing a TNF-binding domain and a chemokine-binding domain called smallpox virus-encoded chemokine receptor (SECRET) domain. ECTV encodes one vTNFR known as CrmD. Infection of ECTV-resistant C57BL/6 mice with a CrmD deletion mutant virus resulted in uniform mortality due to excessive TNF secretion and dysregulated inflammatory cytokine production. CrmD dampened pathology, leukocyte recruitment, and inflammatory cytokine production in lungs including TNF, IL-6, IL-10, and IFN-γ. Blockade of TNF, IL-6, or IL-10R function with monoclonal antibodies reduced lung pathology and provided 60 to 100% protection from otherwise lethal infection. IFN-γ caused lung pathology only when both the TNF-binding and SECRET domains were absent. Presence of the SECRET domain alone induced significantly higher levels of IL-1ß, IL-6, and IL-10, likely overcoming any protective effects that might have been afforded by anti-IFN-γ treatment. The use of TNF-deficient mice and those that express only membrane-associated but not secreted TNF revealed that CrmD is critically dependent on host TNF for its function. In vitro, recombinant Crm proteins from different orthopoxviruses bound to membrane-associated TNF and dampened inflammatory gene expression through reverse signaling. CrmD does not affect virus replication; however, it provides the host advantage by enabling survival. Host survival would facilitate virus spread, which would also provide an advantage to the virus.

Effect of Allium cepa extract on total and differential WBC, TP level, oxidant and antioxidant biomarkers, and lung pathology in ovalbumin-sensitized rats.

BACKGROUND: Previous studies have shown that Allium cepa (A. cepa) has relaxant and anti-inflammatory effects. In this research, A. cepa extract was examined for its prophylactic effect on lung inflammation and oxidative stress in sensitized rats. METHODS: Total and differential white blood cell (WBC) count in the blood, serum levels of oxidant and antioxidant biomarkers, total protein (TP) in bronchoalveolar lavage fluid (BALF), and lung pathology were investigated in control group (C), sensitized group (S), and sensitized groups treated with A. cepa and dexamethasone. RESULTS: Total and most differential WBC count, TP, NO2, NO3, MDA (malondialdehyde), and lung pathological scores were increased while lymphocytes, superoxide dismutase (SOD), catalase (CAT), and thiol were decreased in sensitized animals compared to controls (p < 0.01 to p < 0.001). Treatment with all concentrations of extract significantly improved total WBC, TP, NO2, NO3, interstitial fibrosis, and emphysema compared to the S group (p < 0.05 to p < 0.001). Two higher concentrations of the extract significantly decreased neutrophil and monocyte count, malondialdehyde, bleeding and epithelial damage but increased lymphocyte, CAT, and thiol compared to the S group (p < 0.05 to p < 0.001). Dexamethasone treatment also substantially improved most measured parameters (p < 0.05 to p < 0.001), but it did not change eosinophil percentage. It was proposed that A. cepa extract could affect lung inflammation and oxidative stress in sensitized rats.

A Rabbit Model to Study Antibiotic Penetration at the Site of Infection for Nontuberculous Mycobacterial Lung Disease: Macrolide Case Study.

Nontuberculous mycobacterial pulmonary disease (NTM-PD) is a potentially fatal infectious disease requiring long treatment duration with multiple antibiotics and against which there is no reliable cure. Among the factors that have hampered the development of adequate drug regimens is the lack of an animal model that reproduces the NTM lung pathology required for studying antibiotic penetration and efficacy. Given the documented similarities between tuberculosis and NTM immunopathology in patients, we first determined that the rabbit model of active tuberculosis reproduces key features of human NTM-PD and provides an acceptable surrogate model to study lesion penetration. We focused on clarithromycin, a macrolide and pillar of NTM-PD treatment, and explored the underlying causes of the disconnect between its favorable potency and pharmacokinetics and inconsistent clinical outcome. To quantify pharmacokinetic-pharmacodynamic target attainment at the site of disease, we developed a translational model describing clarithromycin distribution from plasma to lung lesions, including the spatial quantitation of clarithromycin and azithromycin in mycobacterial lesions of two patients on long-term macrolide therapy. Through clinical simulations, we visualized the coverage of clarithromycin in plasma and four disease compartments, revealing heterogeneous bacteriostatic and bactericidal target attainment depending on the compartment and the corresponding potency against nontuberculous mycobacteria in clinically relevant assays. Overall, clarithromycin's favorable tissue penetration and lack of bactericidal activity indicated that its clinical activity is limited by pharmacodynamic, rather than pharmacokinetic, factors. Our results pave the way toward the simulation of lesion pharmacokinetic-pharmacodynamic coverage by multidrug combinations to enable the prioritization of promising regimens for clinical trials.

Comparative characterization of SARS-CoV-2 variants of concern and mouse-adapted strains in mice.

SARS-CoV-2 has evolved into a panel of variants of concern (VOCs) and constituted a sustained threat to global health. The wildtype (WT) SARS-CoV-2 isolates fail to infect mice, while the Beta variant, one of the VOCs, has acquired the capability to infect standard laboratory mice, raising a spreading risk of SARS-CoV-2 from humans to mice. However, the infectivity and pathogenicity of other VOCs in mice remain not fully understood. In this study, we systematically investigated the infectivity and pathogenicity of three VOCs, Alpha, Beta, and Delta, in mice in comparison with two well-understood SARS-CoV-2 mouse-adapted strains, MASCp6 and MASCp36, sharing key mutations in the receptor-binding domain (RBD) with Alpha or Beta, respectively. Our results showed that the Beta variant had the strongest infectivity and pathogenicity among the three VOCs, while the Delta variant only caused limited replication and mild pathogenic changes in the mouse lung, which is much weaker than what the Alpha variant did. Meanwhile, Alpha showed comparable infectivity in lungs in comparison with MASCp6, and Beta only showed slightly lower infectivity in lungs when compared with MASCp36. These results indicated that all three VOCs have acquired the capability to infect mice, highlighting the ongoing spillover risk of SARS-CoV-2 from humans to mice during the continued evolution of SARS-CoV-2, and that the key amino acid mutations in the RBD of mouse-adapted strains may be referenced as an early-warning indicator for predicting the spillover risk of newly emerging SARS-CoV-2 variants.

Esc peptides as novel potentiators of defective cystic fibrosis transmembrane conductance regulator: an unprecedented property of antimicrobial peptides.

Mutations in the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) protein lead to persistent lung bacterial infections, mainly due to Pseudomonas aeruginosa, causing loss of respiratory function and finally death of people affected by CF. Unfortunately, even in the era of CFTR modulation therapies, management of pulmonary infections in CF remains highly challenging especially for patients with advanced stages of lung disease. Recently, we identified antimicrobial peptides (AMPs), namely Esc peptides, with potent antipseudomonal activity. In this study, by means of electrophysiological techniques and computational studies we discovered their ability to increase the CFTR-controlled ion currents, by direct interaction with the F508del-CFTR mutant. Remarkably, this property was not explored previously with any AMPs or peptides in general. More interestingly, in contrast with clinically used CFTR modulators, Esc peptides would give particular benefit to CF patients by combining their capability to eradicate lung infections and to act as promoters of airway wound repair with their ability to ameliorate the activity of the channel with conductance defects. Overall, our findings not only highlighted Esc peptides as the first characterized AMPs with a novel property, that is the potentiator activity of CFTR, but also paved the avenue to investigate the functions of AMPs and/or other peptide molecules, for a new up-and-coming pharmacological approach to address CF lung disease.

Body mass index across adulthood and the development of airflow obstruction and emphysema.

BACKGROUND: Low body mass index (BMI) is associated with COPD, but temporal relationships between airflow obstruction (AO) development and emphysematous change are unclear. We investigated longitudinal changes in BMI, AO, and lung density throughout adulthood using data from the Framingham Offspring Cohort (FOC). METHODS: BMI trajectories were modelled throughout adulthood in 4587 FOC participants from Exam 2 (mean age = 44), through Exam 9 (mean age = 71), in AO participants and non-AO participants (AO n = 1036), determined by spirometry, using fractional polynomial growth curves. This process was repeated for low lung density (LLD) and non LLD participants (LLD n = 225) determined by Computed Tomography. Spirometry decline was compared separately between tertiles of BMI in those aged <40 years and associations between fat and lean mass (measured using Dual Energy X-ray Absorptiometry, DEXA) and development of AO and LLD were also assessed. Additional analyses were performed with adjustment for smoking volume. RESULTS: The BMI trajectory from 30 years of age was visually lower in the AO group than both non-AO smokers (non-

Lung Findings in Minimally Invasive Tissue Sampling (MITS) Examinations of Fetal and Preterm Neonatal Deaths: A Report From the PURPOSe Study.

BACKGROUND: Complete diagnostic autopsy (CDA) is considered to be the gold-standard procedure that aids in determination of cause of death in stillbirths and neonatal deaths. However, CDA is not routinely practiced in South Asian countries due to religious beliefs, lack of expertise, and lack of resources. Minimally invasive tissue sampling (MITS) has been recommended as a less mutilating and less expensive alternative to CDA for obtaining tissues for analysis. The present study aims to evaluate the yield of lung tissue and histological findings using MITS as part of a cause of death analysis for stillborns and preterm neonatal deaths. METHODS: Data were collected during an observational multicenter prospective study called the Project to Understand and Research Preterm birth and Stillbirth (PURPOSe) conducted in India and Pakistan. After obtaining written informed consent from parents, the eligible stillbirths and neonatal deaths were subjected to MITS using a standard protocol. The tissues were obtained from both lungs for histological and microbiological analysis. RESULTS: At both sites, a total of 453 stillbirths and 352 neonatal deaths underwent MITS. For stillbirths and neonatal deaths, the yield of lung tissue using MITS was high (92%). Intrauterine fetal distress and respiratory distress syndrome were the leading lung pathologies reported in stillbirths and neonatal deaths, respectively. CONCLUSIONS: MITS appears to be a reasonable alternative to CDA in obtaining and evaluating lung tissue to inform accurate cause of death analysis in stillbirth and preterm deaths.

IL-6 family cytokines in respiratory health and disease.

Chronic lung diseases including asthma, chronic obstructive pulmonary disease (COPD) and lung fibrosis represent a major burden on healthcare systems with limited effective therapeutic options. Developing effective treatments for these debilitating diseases requires an understanding of how alterations at the molecular level affect lung macroscopic architecture. A common theme among these lung disorders is the presence of an underlying dysregulated immune system which can lead to sustained chronic inflammation. In this respect, several inflammatory cytokines have been implicated in the pathogenesis of lung diseases, thus leading to the notion that cytokines are attractive therapeutic targets for these disorders. In this review, we discuss and highlight the recent breakthroughs that have enhanced our understanding of the role of the interleukin (IL)-6 family of cytokines in lung homeostasis and chronic diseases including asthma, COPD, lung fibrosis and lung cancer.

Progression to fibrosing diffuse alveolar damage in a series of 30 minimally invasive autopsies with COVID-19 pneumonia in Wuhan, China.

AIMS: Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), infection has been deemed as a global pandemic by the World Health Organisation. While diffuse alveolar damage (DAD) is recognised to be the primary manifestation of COVID-19 pneumonia, there has been little emphasis on the progression to the fibrosing phase of DAD. This topic is of great interest, due to growing concerns regarding the potential long-term complications in prolonged survivors. METHODS AND RESULTS: Here we report a detailed histopathological study of 30 autopsy cases with COVID-19 virus infection, based on minimally invasive autopsies performed between February and March, 2020. The mean age was 69 years, with 20 (67%) males and 10 (33%) females and frequent (70.0%) underlying comorbidities. The duration of illness ranged from 16 to 82 (median = 42) days. Histologically, the most common manifestation was diffuse alveolar damage (DAD) in 28 (93.3%) cases which showed predominantly acute (32%), organising (25%) and/or fibrosing (43%) patterns. Patients with fibrosing DAD were one decade younger (P = 0.034) and they had a longer duration of illness (P = 0.033), hospitalisation (P = 0.037) and mechanical ventilation (P = 0.014) compared to those with acute DAD. Patients with organising DAD had a longer duration of illness (P = 0.032) and hospitalisation (P = 0.023) compared to those with acute DAD. CONCLUSIONS: COVID-19 pneumonia patients who develop DAD can progress to the fibrosing pattern. While we observed fibrosing DAD in fatal cases, whether or not surviving patients are at risk for developing pulmonary fibrosis and the frequency of this complication will require further clinical and radiological follow-up studies.

Tracking the time course of pathological patterns of lung injury in severe COVID-19.

BACKGROUND: Pulmonary involvement in COVID-19 is characterized pathologically by diffuse alveolar damage (DAD) and thrombosis, leading to the clinical picture of Acute Respiratory Distress Syndrome. The direct action of SARS-CoV-2 in lung cells and the dysregulated immuno-coagulative pathways activated in ARDS influence pulmonary involvement in severe COVID, that might be modulated by disease duration and individual factors. In this study we assessed the proportions of different lung pathology patterns in severe COVID-19 patients along the disease evolution and individual characteristics. METHODS: We analysed lung tissue from 41 COVID-19 patients that died in the period March-June 2020 and were submitted to a minimally invasive autopsy. Eight pulmonary regions were sampled. Pulmonary pathologists analysed the H&E stained slides, performing semiquantitative scores on the following parameters: exudative, intermediate or advanced DAD, bronchopneumonia, alveolar haemorrhage, infarct (%), arteriolar (number) or capillary thrombosis (yes/no). Histopathological data were correlated with demographic-clinical variables and periods of symptoms-hospital stay. RESULTS: Patient´s age varied from 22 to 88 years (18f/23 m), with hospital admission varying from 0 to 40 days. All patients had different proportions of DAD in their biopsies. Ninety percent of the patients presented pulmonary microthrombosis. The proportion of exudative DAD was higher in the period 0-8 days of hospital admission till death, whereas advanced DAD was higher after 17 days of hospital admission. In the group of patients that died within eight days of hospital admission, elderly patients had less proportion of the exudative pattern and increased proportions of the intermediate patterns. Obese patients had lower proportion of advanced DAD pattern in their biopsies, and lower than patients with overweight. Clustering analysis showed that patterns of vascular lesions (microthrombosis, infarction) clustered together, but not the other patterns. The vascular pattern was not influenced by demographic or clinical parameters, including time of disease progression. CONCLUSION: Patients with severe COVID-19 present different proportions of DAD patterns over time, with advanced DAD being more prevalent after 17 days, which seems to be influenced by age and weight. Vascular involvement is present in a large proportion of patients, occurs early in disease progression, and does not change over time.

Nonclinical Safety Assessment of an Inhaled Formulation of Serelaxin: A Recombinant Human Protein in Rats and Cynomolgus Monkeys (Macaca fascicularis).

Serelaxin is a recombinant human relaxin-2 intended for cardiovascular indications. Inhalation was chosen as alternative route to intravenous to allow daily administration for chronic applications and home treatment. A total of 4 short-term studies were conducted in rats and cynomolgus monkeys with inhaled formulation of serelaxin at dose up to 10 mg/kg/d. All rats and cynomolgus macaques receiving serelaxin were exposed to the test item. One rat and approximately 50% of macaques developed immunogenicity, which did not appear to affect exposure. No adverse effect on respiratory function or systemic changes was noted. Both species developed similar microscopic lesions characterized by eosinophilic cell infiltration around bronchi; however, in the rat, this was more pronounced and extended to a perivascular location. In addition, in the rat, serelaxin showed eosinophilic crystalline material associated with macrophages in the alveoli and bronchioles. In macaques, serelaxin induced minimal macrophage infiltrates in alveoli and perivascular/peribronchiolar mononuclear cell infiltrations. The minimal airway eosinophilic/mononuclear inflammatory cell infiltrations were considered to be nonadverse in macaques due to the minimal severity and the lack of any other alterations in the lung parenchyma. In the rat, the presence of eosinophilic crystalline material and macrophage response, characterized as precipitated test article, was considered adverse.

Primary capicua transcriptional repressor-rearranged sarcoma of the lung.

A 60-year-old man had a malignant left lower lung tumour with no metastases and underwent video-assisted thoracoscopic left lower lobectomy and lymphadenectomy. Pathological examination led to a diagnosis of capicua transcriptional repressor (CIC)-rearranged sarcoma. He has had 3.5 years of recurrence-free survival. CIC-rearranged sarcoma is a Ewing-like sarcoma that shows pathological findings similar to Ewing sarcoma. Most of CIC-rearranged sarcoma is CIC-double homeobox 4 protein (DUX4) fusion. Pulmonary CIC-rearranged sarcoma is extremely rare and has an unfavourable prognosis. However, complete resection can produce prognosis of long-term survival, and thus, surgery is an important option.