Serial evaluation of high-resolution CT findings in patients with pneumonia in novel swine-origin influenza A (H1N1) virus infection

[Pulmonary fibrosis after a new coronavirus infection - versions and controversies: A review]

Fibrosis is a dynamic process characterized by a typical cascade of events as a result of overexpressed repair of connective tissue in response to injury, and manifested by excessive accumulation of extracellular matrix. The development of fibrosis is a determining factor in the pathogenesis, clinical course and prognosis of many diseases, among which interstitial lung diseases occupy a special place. According to a large Russian registry (ClinicalTrials.gov: NCT04492384), in a third of patients with COVID-19, the volume of lung parenchyma involvement exceeds 50% (CT 3-4). The rapid growth in the number of patients who have had a coronavirus infection with lung damage has raised the issues of its long-term consequences to the number of the most relevant in internal medicine of the current time. Often, in the outcome of a coronavirus infection, patients retain clinical and functional changes that are similar to interstitial lung diseases of a different origin, the prognosis of which is determined by the development of interstitial fibrosis and the rate of its progression. This article is an attempt to consider topical issues of fibrogenesis in patients who have undergone a new coronavirus infection through the prism of polar data on immunobiology, clinical course and prognosis.

Long-term outcomes of survivors with influenza A H1N1 virus-induced severe pneumonia and ARDS: a single-center prospective cohort study

Introduction

Systematic evaluation of long-term outcomes in survivors of H1N1 is still lacking. This study aimed to characterize long-term outcomes of severe H1N1-induced pneumonia and acute respiratory distress syndrome (ARDS).

Method

This was a single-center, prospective, cohort study. Survivors were followed up for four times after discharge from intensive care unit (ICU) by lung high-resolution computed tomography (HRCT), pulmonary function assessment, 6-minute walk test (6MWT), and SF-36 instrument.

Result

A total of 60 survivors of H1N1-induced pneumonia and ARDS were followed up for four times. The carbon monoxide at single breath (DLCO) of predicted values and the 6MWT results didn't continue improving after 3 months. Health-related quality of life didn't change during the 12 months after ICU discharge. Reticulation or interlobular septal thickening on HRCT did not begin to improve significantly until the 12-month follow-up. The DLCO of predicted values showed negative correlation with the severity degree of primary disease and reticulation or interlobular septal thickening, and a positive correlation with physical functioning. The DLCO of predicted values and reticulation or interlobular septal thickening both correlated with the highest tidal volume during mechanical ventilation. Levels of fibrogenic cytokines had a positive correlation with reticulation or interlobular septal thickening.

Conclusion

The improvements in pulmonary function and exercise capacity, imaging, and health-related quality of life had different time phase and impact on each other during 12 months of follow-up. Long-term outcomes of pulmonary fibrosis might be related to the lung injury and excessive lung fibroproliferation at the early stage during ICU admission.

Quantitative inspiratory-expiratory chest CT findings in COVID-19 survivors at the 6-month follow-up

We evaluated pulmonary sequelae in COVID-19 survivors by quantitative inspiratory-expiratory chest CT (QCT) and explored abnormal pulmonary diffusion risk factors at the 6-month follow-up. This retrospective study enrolled 205 COVID-19 survivors with baseline CT data and QCT scans at 6-month follow-up. Patients without follow-up pulmonary function tests were excluded. All subjects were divided into group 1 (carbon monoxide diffusion capacity [DL_CO] < 80% predicted, n = 88) and group 2 (DL_CO ≥ 80% predicted, n = 117). Clinical characteristics and lung radiological changes were recorded. Semiquantitative total CT score (0-25) was calculated by adding five lobes scores (0-5) according to the range of lesion involvement (0: no involvement; 1: < 5%; 2: 5-25%; 3: 26-50%; 4: 51-75%; 5: > 75%). Data was analyzed by two-sample t-test, Spearman test, etc. 29% survivors showed air trapping by follow-up QCT. Semiquantitative CT score and QCT parameter of air trapping in group 1 were significantly greater than group 2 (p < 0.001). Decreased DL_CO was negatively correlated with the follow-up CT score for ground-glass opacity (r = - 0.246, p = 0.003), reticulation (r = - 0.206, p = 0.002), air trapping (r = - 0.220, p = 0.002) and relative lung volume changes (r = - 0.265, p = 0.001). COVID-19 survivors with lung diffusion deficits at 6-month follow-up tended to develop air trapping, possibly due to small-airway impairment.

Virus infection induced pulmonary fibrosis

Pulmonary fibrosis is the end stage of a broad range of heterogeneous interstitial lung diseases and more than 200 factors contribute to it. In recent years, the relationship between virus infection and pulmonary fibrosis is getting more and more attention, especially after the outbreak of SARS-CoV-2 in 2019, however, the mechanisms underlying the virus-induced pulmonary fibrosis are not fully understood. Here, we review the relationship between pulmonary fibrosis and several viruses such as Human T-cell leukemia virus (HTLV), Human immunodeficiency virus (HIV), Cytomegalovirus (CMV), Epstein–Barr virus (EBV), Murine γ-herpesvirus 68 (MHV-68), Influenza virus, Avian influenza virus, Middle East Respiratory Syndrome (MERS)-CoV, Severe acute respiratory syndrome (SARS)-CoV and SARS-CoV-2 as well as the mechanisms underlying the virus infection induced pulmonary fibrosis. This may shed new light on the potential targets for anti-fibrotic therapy to treat pulmonary fibrosis induced by viruses including SARS-CoV-2.

Long COVID: "And the fire rages on"

With the increasing cohort of COVID-19 survivors worldwide, we now realize the proportionate rise in post-COVID-19 syndrome. In this review article, we try to define, summarize, and classify this syndrome systematically. This would help clinicians to identify and manage this condition more efficiently. We propose a tool kit that might be useful in recording follow-up data of COVID-19 survivors.

Dynamically linking influenza virus infection kinetics, lung injury, inflammation, and disease severity

Influenza viruses cause a significant amount of morbidity and mortality. Understanding host immune control efficacy and how different factors influence lung injury and disease severity are critical. We established and validated dynamical connections between viral loads, infected cells, CD8⁺ T cells, lung injury, inflammation, and disease severity using an integrative mathematical model-experiment exchange. Our results showed that the dynamics of inflammation and virus-inflicted lung injury are distinct and nonlinearly related to disease severity, and that these two pathologic measurements can be independently predicted using the model-derived infected cell dynamics. Our findings further indicated that the relative CD8⁺ T cell dynamics paralleled the percent of the lung that had resolved with the rate of CD8⁺ T cell-mediated clearance rapidly accelerating by over 48,000 times in 2 days. This complimented our analyses showing a negative correlation between the efficacy of innate and adaptive immune-mediated infected cell clearance, and that infection duration was driven by CD8⁺ T cell magnitude rather than efficacy and could be significantly prolonged if the ratio of CD8⁺ T cells to infected cells was sufficiently low. These links between important pathogen kinetics and host pathology enhance our ability to forecast disease progression, potential complications, and therapeutic efficacy.

Heterogeneity of post-COVID impairment: interim analysis of a prospective study from Czechia

We stratified post-COVID patients into four newly established clinical groups based on the presence or absence of at least one subjective respiratory symptom and at least one objective sign of pulmonary involvement. Nearly half of outpatients and one third of hospitalized post-COVID patients had objective signs of pulmonary involvement without accompanying subjective respiratory symptoms three months after diagnosis.

Therapeutic targets in lung tissue remodelling and fibrosis

Structural changes involving tissue remodelling and fibrosis are major features of many pulmonary diseases, including asthma, chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF). Abnormal deposition of extracellular matrix (ECM) proteins is a key factor in the development of tissue remodelling that results in symptoms and impaired lung function in these diseases. Tissue remodelling in the lungs is complex and differs between compartments. Some pathways are common but tissue remodelling around the airways and in the parenchyma have different morphologies. Hence it is critical to evaluate both common fibrotic pathways and those that are specific to different compartments; thereby expanding the understanding of the pathogenesis of fibrosis and remodelling in the airways and parenchyma in asthma, COPD and IPF with a view to developing therapeutic strategies for each. Here we review the current understanding of remodelling features and underlying mechanisms in these major respiratory diseases. The differences and similarities of remodelling are used to highlight potential common therapeutic targets and strategies. One central pathway in remodelling processes involves transforming growth factor (TGF)-β induced fibroblast activation and myofibroblast differentiation that increases ECM production. The current treatments and clinical trials targeting remodelling are described, as well as potential future directions. These endeavours are indicative of the renewed effort and optimism for drug discovery targeting tissue remodelling and fibrosis.

A Follow-Up Study of Lung Function and Chest Computed Tomography at 6 Months after Discharge in Patients with Coronavirus Disease 2019

We aimed to investigate changes in pulmonary function and computed tomography (CT) findings in patients with coronavirus disease 2019 (COVID-19) during the recovery period. COVID-19 patients underwent symptom assessment, pulmonary function tests, and high-resolution chest CT 6 months after discharge from the hospital. Of the 54 patients enrolled, 31 and 23 were in the moderate and severe group, respectively. The main symptoms 6 months after discharge were fatigue and exertional dyspnea, experienced by 24.1% and 18.5% of patients, respectively, followed by smell and taste dysfunction (9.3%) and cough (5.6%). One patient dropped out of the pulmonary function tests. Of the remaining 54 patients, 41.5% had pulmonary dysfunction. Specifically, 7.5% presented with restrictive ventilatory dysfunction (forced vital capacity <80% of the predicted value), 18.9% presented with small airway dysfunction, and 32.1% presented with pulmonary diffusion impairment (diffusing capacity for carbon monoxide <80% of the predicted value). Of the 54 patients enrolled, six patients dropped out of the chest CT tests. Eleven of the remaining 48 patients presented with abnormal lung CT findings 6 months after discharge. Patients with residual lung lesions were more common in the severe group (52.6%) than in the moderate group (3.4%); a higher proportion of patients had involvement of both lungs (42.1% vs. 3.4%) in the severe group. The residual lung lesions were mainly ground-glass opacities (20.8%) and linear opacities (14.6%). Semiquantitative visual scoring of the CT findings revealed significantly higher scores in the left, right, and both lungs in the severe group than in the moderate group. COVID-19 patients 6 months after discharge mostly presented with fatigue and exertional dyspnea, and their pulmonary dysfunction was mostly characterized by pulmonary diffusion impairment. As revealed by chest CT, the severe group had a higher prevalence of residual lesions than the moderate group, and the residual lesions mostly manifested as ground-glass opacities and linear opacities.

COVID-19 or non-COVID viral pneumonia: How to differentiate based on the radiologic findings?

Influenza viruses were responsible for most adult viral pneumonia. Presently, coronavirus disease 2019 (COVID-19) has evolved into serious global pandemic. COVID-19 outbreak is expected to persist in months to come that will be synchronous with the influenza season. The management, prognosis, and protection for these two viral pneumonias differ considerably and differentiating between them has a high impact on the patient outcome. Reverse transcriptase polymerase chain reaction is highly specific but has suboptimal sensitivity. Chest computed tomography (CT) has a high sensitivity for detection of pulmonary disease manifestations and can play a key-role in diagnosing COVID-19. We reviewed 47 studies and delineated CT findings of COVID-19 and influenza pneumonia. The differences observed in the chest CT scan can be helpful in differentiation. For instance, ground glass opacities (GGOs), as the most frequent imaging finding in both diseases, can differ in the pattern of distribution. Peripheral and posterior distribution, multilobular distribution, pure or clear margin GGOs were more commonly reported in COVID-19, whereas central or peri-bronchovascular GGOs and pure consolidations were more seen in influenza A (H1N1). In review of other imaging findings, further differences were noticed. Subpleural curvilinear lines, sugar melted sign, intra-lesional vascular enlargement, reverse halo sign, and fibrotic bands were more reported in COVID-19 than H1N1, while air space nodule, tree-in-bud, bronchiectasia, pleural effusion, and cavitation were more seen in H1N1. This delineation, when combined with clinical manifestations and laboratory results may help to differentiate these two viral infections.

miR-29a is a negative regulator of influenza virus infection through targeting of the frizzled 5 receptor

Influenza A virus (IAV) infections result in a large number of deaths and substantial economic losses each year. MicroRNAs repress gene expression and are involved in virus-host interactions. miR-29a is known to have anti-tumor and anti-fibrotic effects. However, the role of miR-29a in IAV infection is unclear. In the present study, we investigated the effect of miR-29a on IAV infection and the mechanisms by which it functions. IAV infection was found to cause decreased miR-29a expression in lung epithelial A549 cells and mouse lungs. Overexpression of miR-29a reduced IAV mRNA and protein levels and progeny virus production in HEK293 and A549 cells. Inhibition of IAV infection by miR-29a was observed with different strains of IAV, including A/PR/8/34, A/WSN/1933, and clinical isolates A/OK/3052/09 and A/OK/309/06 H3N2. Knockout of miR-29a using CRISPR/Cas9 resulted in an increase in viral mRNA and protein levels, confirming that miR-29a suppresses IAV infection. A 3' untranslated region (3'-UTR) reporter assay showed that miR-29a had binding sites in the 3'-UTR of the Wnt-Ca²⁺ signaling receptor frizzled 5 gene, and overexpression of miR-29a reduced the level of the endogenous frizzled 5 protein. Wnt5a treatment of HEK293 and A549 cells enhanced IAV infection. Our results suggest that miR-29a inhibits IAV infection, probably via the frizzled 5 receptor.

Association of Underlying Diseases and Clinical Characteristics with Mortality in Patients with 2019 Novel Coronavirus in Iran

Objectives: The first case of 2019 novel coronavirus disease (COVID-19) was reported in Iran in February 2020. Here, we report the epidemiological and clinical characteristics of patients with COVID-19 and factors associated with mortality in these patients. Methods: A retrospective cohort study was conducted from February 22, 2020, to March 24, 2020, in Golestan Hospital in Kermanshah, Iran. Demographic data including underlying diseases and clinical data including the presenting symptoms, chest computed tomography (CT) scan, reverse transcription polymerase chain reaction (RT-PCR) test results, and outcomes were extracted from electronic medical records. Simple and multiple logistic regression methods were used to explore the factors associated with mortality. Results: Of 245 patients admitted with COVID-19, 155 (63.30%) were male. The mean age of the subjects was 54.68 ± 19.21. Forty-five (18.48%) patients had underlying diseases. Common symptoms were dyspnea (n = 137; 55.9%), cough (n = 93; 38.0%), and fever (n = 78; 31.8%). All patients had pneumonia with abnormal findings on chest CT scan (100%), and RT-PCR test results were positive in 87 (35.50%) patients. Of the total admitted cases, 38 (15.5%) patients died during hospitalization. An old age (OR = 1.09; 95% CI: 1.02 to 1.06), history of heart disease (OR = 5.07; 95% CI: 1.46 to 17.58), hypertension (OR = 5.82; 95% CI: 1.13 to 30.04), smoking (OR = 11.44; 95% CI: 1.01 to 29.53), history of at least one underlying disease (OR = 3.31; 95%CI: 1.54 to 7.09), and symptoms of decreased consciousness at the time of admission (OR = 24.23; 95% CI: 2.62 to 223.39) were associated with mortality. Also, the symptoms of cough (OR = 0.383; 95% CI: 0.17 to 0.88) and fever (OR = 0.278; 95% CI: 0.10 to 0.74) had a negative association with mortality. Conclusions: In the current study, factors including old age, smoking, symptoms of decreased consciousness, and underlying diseases such as heart disease, hypertension, and history of at least one underlying disease were associated with mortality. Factors associated with mortality should be considered so that we can better manage patients with COVID-19.

Analysis of Chest CT Results of Coronavirus Disease 2019 (COVID-19) Patients at First Follow-Up

Objective

To investigate the dissipation and outcomes of pulmonary lesions at the first follow-up of patients who recovered from moderate and severe cases of COVID-19.

Methods

From January 21 to March 3, 2020, a total of 136 patients with COVID-19 were admitted to our hospital. According to inclusion and exclusion criteria, 52 patients who recovered from COVID-19 were included in this study, including 33 moderate cases and 19 severe cases. Three senior radiologists independently and retrospectively analyzed the chest CT imaging data of 52 patients at the last time of admission and the first follow-up after discharge, including primary manifestations, concomitant manifestations, and degree of residual lesion dissipation.

Results

At the first follow-up after discharge, 16 patients with COVID-19 recovered to normal chest CT appearance, while 36 patients still had residual pulmonary lesions, mainly including 33 cases of ground-glass opacity, 5 cases of consolidation, and 19 cases of fibrous strip shadow. The proportion of residual pulmonary lesions in severe cases (17/19) was statistically higher than in moderate cases (19/33) (χ ² = 5.759, P < 0.05). At the first follow-up, residual pulmonary lesions were dissipated to varying degrees in 47 cases, and lesions remained unchanged in 5 cases. There were no cases of increased numbers of lesions, enlargement of lesions, or appearance of new lesions. The dissipation of residual pulmonary lesions in moderate patients was statistically better than in severe patients (Z = -2.538, P < 0.05).

Conclusion

Clinically cured patients with COVID-19 had faster dissipation of residual pulmonary lesions after discharge, while moderate patients had better dissipation than severe patients. However, at the first follow-up, most patients still had residual pulmonary lesions, which were primarily ground-glass opacity and fibrous strip shadow. The proportion of residual pulmonary lesions was higher in severe cases of COVID-19, which required further follow-up.

Validation of a composed COVID-19 chest radiography score: the CARE project

OBJECTIVES

The aim of this study was to validate a composed coronavirus disease 2019 (COVID-19) chest radiography score (CARE) based on the extension of ground-glass opacity (GG) and consolidations (Co), separately assessed, and to investigate its prognostic performance.

METHODS

COVID-19-positive patients referring to our tertiary centre during the first month of the outbreak in our area and with a known outcome were retrospectively evaluated. Each lung was subdivided into three areas and a three-grade score assessing the extension of GG and Co was used. The CARE was derived from the sum of the subscores. A mixed-model ANOVA with post hoc Bonferroni correction was used to evaluate whether differences related to the referring unit (emergency room, COVID-19 wards and intensive care unit (ICU)) occurred. Logistic regression analyses were used to investigate the impact of CARE, patients' age and sex on the outcome. To evaluate the prognostic performance of CARE, receiver operating characteristic curves were computed for the entire stay and at admission only.

RESULTS

A total of 1203 chest radiographs of 175 patients (120 males; mean age 67.81±15.5 years old) were examined. On average, each patient underwent 6.8±10.3 radiographs. Patients in ICU as well as deceased patients showed higher CARE scores (p<0.05, each). Age, Co and CARE significantly influenced the outcome (p<0.05 each). The CARE demonstrated good accuracy (area under the curve (AUC)=0.736) using longitudinal data as well as at admission only (AUC=0.740). A CARE score of 17.5 during hospitalisation showed 75% sensitivity and 69.9% specificity.

CONCLUSIONS

The CARE was demonstrated to be a reliable tool to assess the severity of pulmonary involvement at chest radiography with a good prognostic performance.

CT manifestations of coronavirus disease-2019: A retrospective analysis of 73 cases by disease severity

PURPOSE

To report CT features of coronavirus disease-2019 (COVID-19) in patients with various disease severity.

METHODS

The CT manifestations and clinical data of 73 patients with COVID-19 were retrospectively collected in 6 hospitals from Jan 21 to Feb 3, 2020. We analyzed the initial and follow-up CT features of patients with disease severity, according to the Guidelines for the Diagnosis and Treatment of New Coronavirus Pneumonia.

RESULTS

Six patients (8%) were diagnosed as mild type pneumonia; these patients had no obvious abnormal CT findings or manifested mild changes of lung infection. All 43 patients (59 %) with common type presented unique or multiple ground-glass opacities (GGO) in the periphery of the lungs, with or without interlobular septal thickening. In the 21 patients (29 %) with severe type, extensive GGO and pulmonary consolidation were found in 16 cases (16/21, 76 %) and 5 cases (24 %), respectively. An extensive "white lung", with atelectasis and pleural effusion were found in critical type patients (3, 4%). On the resolutive phase of the disease, CT abnormalities showed complete resolution, or demonstrated residual linear opacities.

CONCLUSIONS

Different CT features are seen according to disease severity, which can help COVID-19 stratification.

Influenza A virus H1N1 associated pneumonia - acute and late aspects evaluated with high resolution tomography in hospitalized patients

Background

Influenza A (H1N1) virus often compromises the respiratory tract, leading to pneumonia, which is the principal cause of death in these patients. The purpose of this study was to review the acute and late phase pulmonary findings in influenza A(H1N1) associated pneumonia using high resolution computed tomography (HRCT), and to determine the importance of performing end expiration series.

Methods

Between July and August 2009, 140 patients presented with influenza A (H1N1) confirmed by real-timepolymerase chain reaction. Out of these, 27 patients underwent HRCT in the acute and late phases of pneumonia, allowing for a comparative study. Late phase exams were performed due to clinical worsening and up to 120 days later in patients with persistent complaints of dyspnea.

Results

Ground glass opacities, consolidations, and the combination of both were associated with the acute phase, whereas persistence or worsening of the lesions, lesion improvement, and air trapping in the end expiration series (as seen using HRCT, n=6) were observed in the late phase.

Conclusions

In the HRCT end expiration series, air trapping was found in the late phase of H1N1 associated pneumonia. Generally, these exams are not evaluated in research articles, and air trapping has not previously been studied using the end expiration series. Our study brings more scientific knowledge about aspects of pulmonary involvement by influenza A (H1N1), through evaluation with end expiration series, which makes the CT exam dynamic, translating the respiratory movement, and showing bronchial alteration.

Macrophage PPAR-γ suppresses long-term lung fibrotic sequelae following acute influenza infection

Influenza virus causes a heterogeneous respiratory infectious disease ranging from self-limiting symptoms to non-resolving pathology in the lungs. Worldwide, seasonal influenza infections claim ~500,000 lives annually. Recent reports describe pathologic pulmonary sequelae that result in remodeling the architecture of lung parenchyma following respiratory infections. These dysfunctional recovery processes that disproportionately impact the elderly have been understudied. Macrophages are involved in tissue remodeling and are critical for survival of severe influenza infection. Here, we found intrinsic deficiency of the nuclear receptor PPAR-γ in myeloid cells delayed the resolution of pulmonary inflammation following influenza infection. Mice with myeloid cell-specific PPAR-γ deficiency subsequently presented with increased influenza-induced deposition of pulmonary collagen compared to control mice. This dysfunctional lung remodeling was progressive and sustained for at least 3 months following infection of mice with myeloid PPAR-γ deficiency. These progressive changes were accompanied by a pro-fibrotic gene signature from lung macrophages and preceded by deficiencies in activation of genes involved with damage repair. Importantly similar aberrant gene expression patterns were also found in a secondary analysis of a study where macrophages were isolated from patients with fibrotic interstitial lung disease. Quite unexpectedly, mice with PPAR-γ deficient macrophages were more resistant to bleomycin-induced weight loss whereas extracellular matrix deposition was unaffected compared to controls. Therefore PPAR-γ expression in macrophages may be a pathogen-specific limiter of organ recovery rather than a ubiquitous effector pathway in response to generic damage.

Lung Transplantation in Pulmonary Fibrosis Secondary to Influenza A Pneumonia

Influenza A (H1N1) can rapidly progress to acute respiratory distress syndrome and pulmonary fibrosis. We describe a 45-year-old man with acute respiratory distress syndrome and progressive lung fibrosis secondary to H1N1 pneumonia who was treated for 45 days with venovenous extracorporeal membrane oxygenation as a rescue utility and bridge to bilateral lung transplantation. The patient was saved and lived well. Lung transplantation may be a viable alternative for patients with lung fibrosis secondary to H1N1-induced acute respiratory distress syndrome in very selected situations.

Imaging of Emerging Infectious Diseases

Purpose of Review

Emerging infectious diseases have seen a record increase in prevalence, and understanding their management is critical in an increasingly global community. In this paper, we review current literature detailing the role of radiology in the diagnosis and treatment of the Ebola (EVD), Zika (ZVD), Chikungunya (CHIKF), H1N1, Middle East Respiratory (MERS), and Severe Acute Respiratory Syndrome (SARS) viruses.

Recent Findings

Complex protocols are required to safely use portable imaging in EVD to prevent nosocomial spread of disease. In ZVD, antenatal ultrasound can detect fetal abnormalities early, allowing implementation of care and support to affected families. Imaging is useful in assessing the extent of involvement of chronic CHIKF and monitoring treatment effect. Chest radiography and CT play a more direct role in the diagnosis and monitoring of the viral infections with primarily respiratory manifestations (H1N1, MERS, and SARS).

Summary

Radiology plays a variable role in emerging infectious diseases, requiring an understanding of disease transmission and safe imaging practices, as well as imaging features that affect clinical management.

IL-6 ameliorates acute lung injury in influenza virus infection

Interleukin 6 (IL-6) is involved in innate and adaptive immune responses to defend against pathogens. It also participates in the process of influenza infection by affecting viral clearance and immune cell responses. However, whether IL-6 impacts lung repair in influenza pathogenesis remains unclear. Here, we studied the role of IL-6 in acute influenza infection in mice. IL-6-deficient mice infected with influenza virus exhibited higher lethality, lost more body weight and had higher fibroblast accumulation and lower extracellular matrix (ECM) turnover in the lung than their wild-type counterparts. Deficiency in IL-6 enhanced proliferation, migration and survival of lung fibroblasts, as well as increased virus-induced apoptosis of lung epithelial cells. IL-6-deficient lung fibroblasts produced elevated levels of TGF-β, which may contribute to their survival. Furthermore, macrophage recruitment to the lung and phagocytic activities of macrophages during influenza infection were reduced in IL-6-deficient mice. Collectively, our results indicate that IL-6 is crucial for lung repair after influenza-induced lung injury through reducing fibroblast accumulation, promoting epithelial cell survival, increasing macrophage recruitment to the lung and enhancing phagocytosis of viruses by macrophages. This study suggests that IL-6 may be exploited for lung repair during influenza infection.

CT findings in viral lower respiratory tract infections caused by parainfluenza virus, influenza virus and respiratory syncytial virus

Viral lower respiratory tract infections (LRTIs) can present with a variety of computed tomography (CT) findings. However, identifying the contribution of a particular virus to CT findings is challenging due to concomitant infections and the limited data on the CT findings in viral LRTIs. We therefore investigate the CT findings in different pure viral LRTIs.All patients who underwent bronchoalveolar lavage (BAL) and were diagnosed with LRTIs caused by parainfluenza virus (PIV), influenza virus, or respiratory syncytial virus (RSV) between 1998 and 2014 were enrolled in a tertiary hospital in Seoul, South Korea. A pure viral LRTI was defined as a positive viral culture from BAL without any positive evidence from respiratory or blood cultures, or from polymerase chain reaction (PCR), or from serologic tests for bacteria, fungi, mycobacteria, or other viruses.CT images of 40 patients with viral LRTIs were analyzed: 14 with PIV, 14 with influenza virus, and 12 with RSV. Patch consolidation (≥1 cm or more than 1 segmental level) was found only in PIV (29%) (P = 0.03), by which CT findings caused by PIV could resemble those seen in bacterial LRTIs. Ground-glass opacities were seen in all cases of influenza virus and were more frequent than in PIV (71%) and RSV (67%) (P = 0.05). Bronchial wall thickening was more common in influenza virus (71%) and RSV (67%) LRTIs than PIV LRTIs (21%) (P = 0.02). With respect to anatomical distribution, PIV infections generally affected the lower lobes (69%), while influenza virus mostly caused diffuse changes throughout the lungs (57%), and RSV frequently formed localized patterns in the upper and mid lobes (44%).The CT findings in LRTIs of PIV, influenza virus, and RSV can be distinguished by certain characteristics. These differences could be useful for early differentiation of these viral LRTIs, and empirical use of appropriate antiviral agents.

Swine flu fibrosis: Regressive or progressive?

Swine flu influenza had spread the world over in 2009. The main pathology was bilateral pneumonia. Majority of these cases recovered from pneumonia fully. Though in some cases, pulmonary fibrosis was reported as a sequel. However, long-term progression of such pulmonary fibrosis is uncertain. We are hereby reporting two cases of swine flu that showed residual pulmonary fibrosis. The clinical and laboratory parameters were also recorded. In both the cases, radiological shadows and spirometric values did not show deterioration. We conclude that swine flu pulmonary fibrosis is not a progressive condition.

DAMPs and influenza virus infection in ageing

Influenza A virus (IAV) is a serious global health problem worldwide due to frequent and severe outbreaks. IAV causes significant morbidity and mortality in the elderly population, due to the ineffectiveness of the vaccine and the alteration of T cell immunity with ageing. The cellular and molecular link between ageing and virus infection is unclear and it is possible that damage associated molecular patterns (DAMPs) may play a role in the raised severity and susceptibility of virus infections in the elderly. DAMPs which are released from damaged cells following activation, injury or cell death can activate the immune response through the stimulation of the inflammasome through several types of receptors found on the plasma membrane, inside endosomes after endocytosis as well as in the cytosol. In this review, the detriment in the immune system during ageing and the links between influenza virus infection and ageing will be discussed. In addition, the role of DAMPs such as HMGB1 and S100/Annexin in ageing, and the enhanced morbidity and mortality to severe influenza infection in ageing will be highlighted.

Thin-section computed tomography detects long-term pulmonary sequelae 3 years after novel influenza A virus-associated pneumonia

BACKGROUND

The aim of this research was to evaluate long-term pulmonary sequelae on paired inspiration-expiration thin-section computed tomography (CT) scans 3 years after influenza A (H1N1) virus-associated pneumonia, and to analyze the affecting factors on pulmonary fibrosis.

METHODS

Twenty-four patients hospitalized with H1N1 virus-associated pneumonia at our hospital between September 2009 and January 2010 were included. The patients underwent thin-section CT 3 years after recovery. Abnormal pulmonary lesion patterns (ground-glass opacity, consolidation, parenchymal bands, air trapping, and reticulation) and evidence of fibrosis (architectural distortion, traction bronchiectasis, or honeycombing) were evaluated on follow-up thin-section CT. Patients were assigned to Group 1 (with CT evidence of fibrosis) and Group 2 (without CT evidence of fibrosis). Demographics, rate of mechanical ventilation therapy, rate of intensive care unit admission, cumulative prednisolone-equivalent dose, laboratory tests results (maximum levels of alanine aminotransferase, aspartate transaminase [AST], lactate dehydrogenase [LDH], and creatine kinase [CK]), and peak radiographic opacification of 24 patients during the course of their illness in the hospital were compared between two groups.

RESULTS

Parenchymal abnormality was present in 17 of 24 (70.8%) patients and fibrosis occurred in 10 of 24 (41.7%) patients. Patients in Group 1 (10/24; 41.7%) had a higher rate of mechanical ventilation therapy (Z = -2.340, P = 0.019), higher number of doses of cumulative prednisolone-equivalent (Z = -2.579, P = 0.010), higher maximum level of laboratory tests results (AST [Z = -2.140, P = 0.032], LDH [Z = -3.227, P = 0.001], and CK [Z = -3.345, P = 0.019]), and higher peak opacification on chest radiographs (Z = -2.743, P = 0.006) than patients in group 2 (14/24; 58.3%).

CONCLUSIONS

H1N1 virus-associated pneumonia frequently is followed by long-term pulmonary sequelae, including fibrotic changes, in lung parenchyma. Patients who need more steroid therapy, need more mechanical ventilation therapy, had higher laboratory tests results (maximum levels of AST, LDH, and CK), and had higher peak opacification on chest radiographs during treatment are more likely to develop lung fibrosis.

Longitudinal changes of pneumonia complicating novel influenza A (H1N1) by high-resolution computed tomography

Purpose

To assess lung lesions in patients with pneumonia complicating novel influenza A (H1N1) by serial high-resolution computed tomography (HRCT) during the early, progressive and convalescent stages.

Samples and methods

Serial HRCT scans in 39 patients with pneumonia complicating novel influenza A (H1N1) were reviewed for predominant patterns of lung abnormalities as well as distribution and extent of involvement. Longitudinal changes were assessed at different time points.

Results

In the early stage, the most common HRCT finding was patchy ground-glass opacity (GGO) (n = 4, 54.7%). In the progressive stage, bilaterally distributed GGO mixed with consolidation was the most commonly observed feature (n = 28, 71.8%). The diffuse pattern deteriorated to a peak (n = 17, 43.6%) at this stage. In the convalescent stage, the most common finding was fibrosis (n = 25, 64.1%). Averagely, fibrosis was observed at d 18.5 ± 6.4 after the onset of symptoms. Three patterns of longitudinal changes of the lesions were observed, including: type 1, improvement after deterioration; type 2, concurrent improvement and deterioration followed by improvement; and type 3, gradual improvement. Type 1 was the more common pattern (n = 27, 69.2%). Complete serial HRCT scans from initial and final scan were obtained in 24 patients, and the mean CT score peaked at d 8–14 of the illness.

Conclusion

HRCT may play a role in detecting and characterizing pulmonary lesions for the cases of pneumonia complicating influenza A. In addition, it may contribute to monitoring longitudinal changes of pneumonia and assessing therapeutic response.

Influenza promotes collagen deposition via αvβ6 integrin-mediated transforming growth factor β activation

Influenza infection exacerbates chronic pulmonary diseases, including idiopathic pulmonary fibrosis. A central pathway in the pathogenesis of idiopathic pulmonary fibrosis is epithelial injury leading to activation of transforming growth factor β (TGFβ). The mechanism and functional consequences of influenza-induced activation of epithelial TGFβ are unclear. Influenza stimulates toll-like receptor 3 (TLR3), which can increase RhoA activity, a key event prior to activation of TGFβ by the αvβ6 integrin. We hypothesized that influenza would stimulate TLR3 leading to activation of latent TGFβ via αvβ6 integrin in epithelial cells. Using H1152 (IC50 6.1 μm) to inhibit Rho kinase and 6.3G9 to inhibit αvβ6 integrins, we demonstrate their involvement in influenza (A/PR/8/34 H1N1) and poly(I:C)-induced TGFβ activation. We confirm the involvement of TLR3 in this process using chloroquine (IC50 11.9 μm) and a dominant negative TLR3 construct (pZERO-hTLR3). Examination of lungs from influenza-infected mice revealed augmented levels of collagen deposition, phosphorylated Smad2/3, αvβ6 integrin, and apoptotic cells. Finally, we demonstrate that αvβ6 integrin-mediated TGFβ activity following influenza infection promotes epithelial cell death in vitro and enhanced collagen deposition in vivo and that this response is diminished in Smad3 knock-out mice. These data show that H1N1 and poly(I:C) can induce αvβ6 integrin-dependent TGFβ activity in epithelial cells via stimulation of TLR3 and suggest a novel mechanism by which influenza infection may promote collagen deposition in fibrotic lung disease.

Influenza A (H1N1) pneumonia: HRCT findings

OBJECTIVE:

To describe aspects found on HRCT scans of the chest in patients infected with the influenza A (H1N1) virus.

METHODS:

We retrospectively analyzed the HRCT scans of 71 patients (38 females and 33 males) with H1N1 infection, confirmed through laboratory tests, between July and September of 2009. The HRCT scans were interpreted by two thoracic radiologists independently, and in case of disagreement, the decisions were made by consensus.

RESULTS:

The most common HRCT findings were ground-glass opacities (85%), consolidation (64%), or a combination of ground-glass opacities and consolidation (58%). Other findings were airspace nodules (25%), bronchial wall thickening (25%), interlobular septal thickening (21%), crazy-paving pattern (15%), perilobular pattern (3%), and air trapping (3%). The findings were frequently bilateral (89%), with a random distribution (68%). Pleural effusion, when observed, was typically minimal. No lymphadenopathy was identified.

CONCLUSIONS:

The most common findings were ground-glass opacities and consolidations, or a combination of both. Involvement was commonly bilateral with no axial or craniocaudal predominance in the distribution. Although the major tomographic findings in H1N1 infection are nonspecific, it is important to recognize such findings in order to include infection with the H1N1 virus in the differential diagnosis of respiratory symptoms.

Computed tomography findings in patients with H1N1 influenza A infection

The present study aimed to review high resolution computed tomography findings in patients with H1N1 influenza A infection. The most common tomographic findings include ground-glass opacities, areas of consolidation or a combination of both patterns. Some patients may also present bronchial wall thickening, airspace nodules, crazy-paving pattern, perilobular opacity, air trapping and findings related to organizing pneumonia. These abnormalities are frequently bilateral, with subpleural distribution. Despite their nonspecificity, it is important to recognize the main tomographic findings in patients affected by H1N1 virus in order to include this possibility in the differential diagnosis, characterize complications and contribute in the follow-up, particularly in cases of severe disease.