Resolving Viral-Induced Secondary Bacterial Infection in COPD: A Concise Review

Neutrophil-to-Lymphocyte Ratio (NLR), Platelet-to-Lymphocyte Ratio (PLR) and Monocyte-to-Lymphocyte Ratio (MLR) as Biomarkers in Diagnosis Evaluation of Acute Exacerbation of Chronic Obstructive Pulmonary Disease: A Retrospective, Observational Study

Purpose

Hierarchical management is advocated in China to effectively manage chronic obstructive pulmonary disease (COPD) patients and reduce the incidence and mortality of acute exacerbation of COPD (AE-COPD). However, primary and community hospitals often have limited access to advanced equipment and technology. Complete blood count (CBC), which is commonly used in these hospitals, offers the advantages of being cost-effective and easily accessible. This study aims to evaluate the significance of routine blood indicators in aiding of diagnosing AE-COPD.

Patients and Methods

In this research, we enrolled a total of 112 patients diagnosed with AE-COPD, 92 patients with stable COPD, and a control group comprising 60 healthy individuals. Clinical characteristics, CBC parameters, and serum CRP levels were collected within two hours. To assess the associations between NLR/PLR/MLR and CRP by Spearman correlation test. The diagnostic accuracy of NLR, PLR and MLR in AE-COPD was assessed using Receiver Operating Characteristic Curve (ROC) and the area under the curve (AUC). Binary Logistic Regression analysis was conducted for the indicators of NLR, PLR and MLR.

Results

We found that patients with AE-COPD had significantly higher levels of NLR, PLR and MLR in contrast to patients with stable COPD. Additionally, the study revealed a noteworthy correlation between CRP and NLR (rs=0.5319, P<0.001), PLR (rs=0.4424, P<0.001), and MLR (rs=0.4628, P<0.001). By utilizing specific cut-off values, the amalgamation of NLR, PLR and MLR augmented diagnostic sensitivity. Binary logistic regression analysis demonstrated that heightened NLR and MLR act as risk factors for the progression of AE-COPD.

Conclusion

The increasing levels of NLR, PLR and MLR could function as biomarkers, akin to CRP, for diagnosis and assessment of acute exacerbations among COPD patients. Further research is required to validate this concept.

Unveiling the anti-inflammatory potential of Acalypha indica L. and analyzing its research trend: digging deep to learn deep

The plant Acalypha indica L. is a well-known traditional plant belonging to the family Euphorbiaceae. Traditional practices of the plant claim to treat asthma, pneumonia, wound healing, rheumatoid arthritis, bronchitis, and skin disorders. The major phytochemicals reported are cyanogenic glucosides, tannins, coumarins, flavonoid glycosides, fatty acids, and volatile oils. To summarize the anti-inflammatory potential of Acalypha indica extract and its phytochemicals through preclinical studies. The search terms include anti-inflammatory, Acalypha indica, and Acalypha indica extract independently or in combination with pro-inflammatory markers using various databases, including Scopus, Web of Science, PubMed, ProQuest, and Google Scholar. The results of preclinical studies confirm that Acalypha indica exhibits strong anti-inflammatory activity. Most of the experimental studies that have been conducted on plant extract are protein denaturation, human red blood cell membrane stabilization assay, and carrageenan-induced inflammation models. However, the molecular mechanism in these studies is still unclear to demonstrate its anti-inflammatory effects. Acalypha indica possesses anti-inflammatory effects that may be due to the presence of phenolic compounds especially flavonoids present in the Acalypha indica. Thus, further research is needed, to understand mechanistic insights of the plant phytochemicals to represent anti-inflammatory properties.

Immunomodulatory Effects of Fluoroquinolones in Community-Acquired Pneumonia-Associated Acute Respiratory Distress Syndrome

Community-acquired pneumonia is reported as one of the infectious diseases that leads to the development of acute respiratory distress syndrome. The innate immune system is the first line of defence against microbial invasion; however, its dysregulation during infection, resulting in an increased pathogen load, stimulates the over-secretion of chemokines and pro-inflammatory cytokines. This phenomenon causes damage to the epithelial-endothelial barrier of the pulmonary alveoli and the leakage of the intravascular protein into the alveolar lumen. Fluoroquinolones are synthetic antimicrobial agents with immunomodulatory properties that can inhibit bacterial proliferation as well as exhibit anti-inflammatory activities. It has been demonstrated that the structure of fluoroquinolones, particularly those with a cyclopropyl group, exerts immunomodulatory effects. Its capability to inhibit phosphodiesterase activity leads to the accumulation of intracellular cAMP, which subsequently enhances PKA activity, resulting in the inhibition of transcriptional factor NF-κB and the activation of CREB. Another mechanism reported is the inhibition of TLR and ERK signalling pathways. Although the sequence of events has not been completely understood, significant progress has been made in comprehending the specific mechanisms underlying the immunomodulatory effects of fluoroquinolones. Here, we review the indirect immunomodulatory effects of FQs as an alternative to empirical therapy in patients diagnosed with community-acquired pneumonia.

The Molecular Blueprint for Chronic Obstructive Pulmonary Disease (COPD): A New Paradigm for Diagnosis and Therapeutics

The global prevalence of chronic obstructive pulmonary disease (COPD) has increased over the last decade and has emerged as the third leading cause of death worldwide. It is characterized by emphysema with prolonged airflow limitation. COPD patients are more susceptible to COVID-19 and increase the disease severity about four times. The most used drugs to treat it show numerous side effects, including immune suppression and infection. This review discusses a narrative opinion and critical review of COPD. We present different aspects of the disease, from cellular and inflammatory responses to cigarette smoking in COPD and signaling pathways. In addition, we highlighted various risk factors for developing COPD apart from smoking, like occupational exposure, pollutants, genetic factors, gender, etc. After the recent elucidation of the underlying inflammatory signaling pathways in COPD, new molecular targeted drug candidates for COPD are signal-transmitting substances. We further summarize recent developments in biomarker discovery for COPD and its implications for disease diagnosis. In addition, we discuss novel drug targets for COPD that could be explored for drug development and subsequent clinical management of cardiovascular disease and COVID-19, commonly associated with COPD. Our extensive analysis of COPD cause, etiology, diagnosis, and therapeutic will provide a better understanding of the disease and the development of effective therapeutic options. In-depth knowledge of the underlying mechanism will offer deeper insights into identifying novel molecular targets for developing potent therapeutics and biomarkers of disease diagnosis.

The first arriving virus shapes within-host viral diversity during natural epidemics

Viral diversity has been discovered across scales from host individuals to populations. However, the drivers of viral community assembly are still largely unknown. Within-host viral communities are formed through co-infections, where the interval between the arrival times of viruses may vary. Priority effects describe the timing and order in which species arrive in an environment, and how early colonizers impact subsequent community assembly. To study the effect of the first-arriving virus on subsequent infection patterns of five focal viruses, we set up a field experiment using naïve Plantago lanceolata plants as sentinels during a seasonal virus epidemic. Using joint species distribution modelling, we find both positive and negative effects of early season viral infection on late season viral colonization patterns. The direction of the effect depends on both the host genotype and which virus colonized the host early in the season. It is well established that co-occurring viruses may change the virulence and transmission of viral infections. However, our results show that priority effects may also play an important, previously unquantified role in viral community assembly. The assessment of these temporal dynamics within a community ecological framework will improve our ability to understand and predict viral diversity in natural systems.

Analysis of the correlation between BMI and respiratory tract microbiota in acute exacerbation of COPD

Objective

To investigate the distribution differences in the respiratory tract microbiota of AECOPD patients in different BMI groups and explore its guiding value for treatment.

Methods

Sputum samples of thirty-eight AECOPD patients were collected. The patients were divided into low, normal and high BMI group. The sputum microbiota was sequenced by 16S rRNA detection technology, and the distribution of sputum microbiota was compared. Rarefaction curve, α-diversity, principal coordinate analysis (PCoA) and measurement of sputum microbiota abundance in each group were performed and analyzed by bioinformatics methods.

Results

1. The rarefaction curve in each BMI group reached a plateau. No significant differences were observed in the OTU total number or α-diversity index of microbiota in each group. PCoA showed significant differences in the distance matrix of sputum microbiota between the three groups, which was calculated by the Binary Jaccard and the Bray Curtis algorithm. 2. At the phylum level, most of the microbiota were Proteobacteria, Bacteroidetes Firmicutes, Actinobacteria, and Fusobacteria. At the genus level, most were Streptococcus, Prevotella, Haemophilus, Neisseria and Bacteroides. 3. At the phylum level, the abundance of Proteobacteria in the low group was significantly higher than that in normal and high BMI groups, the abundances of Firmicutes in the low and normal groups were significantly lower than that in high BMI groups. At the genus level, the abundance of Haemophilus in the low group was significantly higher than that in high BMI group, and the abundances of Streptococcus in the low and normal BMI groups were significantly lower than that in the high BMI group.

Conclusions

1. The sputum microbiota of AECOPD patients in different BMI groups covered almost all microbiota, and BMI had no significant association with total number of respiratory tract microbiota or α-diversity in AECOPD patients. However, there was a significant difference in the PCoA between different BMI groups. 2. The microbiota structure of AECOPD patients differed in different BMI groups. Gram-negative bacteria (G-) in the respiratory tract of patients predominated in the low BMI group, while gram-positive bacteria (G+) predominated in the high BMI group.

cAMP-PDE signaling in COPD: Review of cellular, molecular and clinical features

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death among non-contagious diseases in the world. PDE inhibitors are among current medicines prescribed for COPD treatment of which, PDE-4 family is the predominant PDE isoform involved in hydrolyzing cyclic adenosine monophosphate (cAMP) that regulates the inflammatory responses in neutrophils, lymphocytes, macrophages and epithelial cells The aim of this study is to investigate the cellular and molecular mechanisms of cAMP-PDE signaling, as an important pathway in the treatment management of patients with COPD. In this review, a comprehensive literature review was performed about the effect of PDEs in COPD. Generally, PDEs are overexpressed in COPD patients, resulting in cAMP inactivation and decreased cAMP hydrolysis from AMP. At normal amounts, cAMP is one of the essential agents in regulating metabolism and suppressing inflammatory responses. Low amount of cAMP lead to activation of downstream inflammatory signaling pathways. PDE4 and PDE7 mRNA transcript levels were not altered in polymorphonuclear leukocytes and CD8 lymphocytes originating from the peripheral venous blood of stable COPD subjects compared to healthy controls. Therefore, cAMP-PDE signaling pathway is one of the most important signaling pathways involved in COPD. By examining the effects of different drugs in this signaling pathway critical steps can be taken in the treatment of this disease.

Use of Systemic Antibiotics in Patients with COVID-19 in Colombia: A Cross-Sectional Study

Antibiotics are frequently prescribed to patients with COVID-19. The aim was to determine the pattern of use of systemic antibiotics in a group of patients diagnosed with COVID-19 in Colombia between 2020-2022. This was a descriptive cross-sectional study designed to identify antibiotics prescription patterns for patients diagnosed with COVID-19 treated in eight clinics in Colombia. The AWaRe tool of the World Health Organization (WHO) was used to classify the antibiotics. A total of 10,916 patients were included. The median age was 57 years, and 56.4% were male. A total of 57.5% received antibiotics, especially ampicillin/sulbactam (58.8%) and clarithromycin (47.9%). Most of the antibiotics were classified as Watch (65.1%), followed by Access (32.6%) and Reserve (2.4%). Men (OR: 1.29; 95%CI: 1.17-1.43), older adults (OR: 1.67; 95%CI: 1.48-1.88), patients with dyspnea (OR: 1.26; 95%CI: 1.13-1.41), rheumatoid arthritis (OR: 1.94; 95%CI: 1.17-3.20), and high blood pressure at admission (OR: 1.45; 95%CI: 1.29-1.63), patients treated in-hospital (OR: 5.15; 95%CI: 4.59-5.77), patients admitted to the ICU (OR: 10.48; 95%CI: 8.82-12.45), patients treated with systemic glucocorticoids (OR: 3.60; 95%CI: 3.21-4.03) and vasopressors (OR: 2.10; 95%CI: 1.60-2.75), and patients who received invasive mechanical ventilation (OR: 2.37; 95%CI: 1.82-3.09) were more likely to receive a systemic antibiotic. Most of the patients diagnosed with COVID-19 received antibiotics, despite evidence showing that bacterial coinfection is rare. Antibiotics from the Watch group predominated, a practice that goes against WHO recommendations.

The Influence of Influenza Virus Infections in Patients with Chronic Obstructive Pulmonary Disease

Introduction

Chronic obstructive pulmonary disease (COPD) is a common disease and is preventable and treatable. A previous study showed that influenza virus infections were also associated with the risk of acute exacerbation in patients with COPD, and other studies showed that the influenza virus might increase the risk of stroke. However, studies on the influence of influenza infection among COPD patients are limited. In this study, we review the role of influenza infection in contributing to mortality, pneumonia, respiratory failure, COPD acute exacerbation, and ischemic stroke among COPD patients.

Materials and Methods

We performed a population-based cohort study of COPD patients using data from Taiwan between January 1, 2011, and December 31, 2019. We excluded patients with lung cancer, lung transplantation and asthma. We also excluded patients who lacked COPD medication prescriptions and those treated with anti-influenza drugs without flu diagnosis records. Patients with missing or incomplete data were also excluded from the study cohort.

Results

After 1:1 matching by age, sex, COPD duration, diagnosed years and comorbidities, we enrolled 10,855 cases and controls for further analysis. The risks of pneumonia, respiratory failure, COPD acute exacerbation, and ischemic stroke were 1.770 (95% CI=1.638–1.860; P<0.0001), 1.097 (95% CI=1.008–1.194; P=0.0319), 1.338 (95% CI=1.248–1.435; P<0.0001), and 1.134 (95% CI=1.039–1.239, P=0.0051), respectively, in the influenza infection group compared with COPD patients without influenza infection.

Conclusion

Influenza infections are linked to an increased risk of ischemic stroke, pneumonia, respiratory failure, and COPD acute exacerbation among COPD patients. In conclusion, patients with COPD need to be closely monitored after having an influenza infection.

Analysis of Microbiological and Clinical Characteristics of Bacterial Infection in Patients with Pulmonary Infection

Objective

Using data investigation, the microbiology of bacterial infection in patients with pulmonary infection was discussed, and its clinical characteristics were analyzed.

Methods

The clinical data of 160 patients with pulmonary infection in our hospital from March 2019 to March 2021 were collected and analyzed. Blood samples were collected and cultured, and the pathogens were identified. The distribution, constituent ratio, and drug resistance of pathogens in elderly patients with pulmonary infection were analyzed. Logistics regression analysis was adopted to analyze the risk factors of pulmonary infection.

Results

Of the 160 patients with pulmonary infection, 107 were males (66.88%) and 53 were females (33.13%). The age ranged from 12 to 97 years old, with an average of 63.82 ± 12.64 years old. Sevent-six patients (47.50%) were over 65 years old. Urban patients accounted for 71.88%, and rural patients accounted for 28.13%, of which workers accounted for 46.25%, and farmers and cadres each accounted for about 4%. 85.62% of smokers have smoked for more than 4 years. Eighty-five patients had chronic diseases such as coronary heart disease, hypertension, diabetes, and cerebrovascular disease. Heart failure occurred in 10.00%, old tuberculosis in 11.25%, and new tuberculosis in 5.63%. The average hospital stay of the patients was 14.93 days, and the improvement rate was 91.25%. Eleven patients died. Among the 160 patients with pulmonary infection, COPD, pneumonia, and lung cancer accounted for the highest proportions, and idiopathic pulmonary fibrosis, bronchitis dilatation, tuberculosis, and bronchial asthma also played an important role. Pathogenic bacteria were detected in 104 of the 160 elderly patients with pulmonary infection, and the detection rate was 65.00%. A total of 444 strains of pathogenic bacteria were detected, including 328 strains of Gram-negative bacteria (73.87%, mainly Klebsiella pneumoniae, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and Serratia marcescens), 28 strains of Gram-positive bacteria (6.30%, mainly Staphylococcus aureus), and 88 strains of fungi (20.00%, mainly Candida albicans). Regarding Klebsiella pneumoniae in elderly patients with pulmonary infection, the drug resistance rates were 59.72% for amoxicillin-clavulanate potassium, 52.78% for ampicillin sodium-sulbactam sodium, and 51.39% for cefazolin sodium. Regarding Pseudomonas aeruginosa, the drug resistance rates were 29.31% for ticarcillin sodium-potassium clavulanate, 27.59% for piperacillin sodium, and 24.14% for gentamicin. Regarding Stenotrophomonas maltophilia, the drug resistance rates were 79.55% for ceftazidime, 38.64% for chloramphenicol, and 31.82% for levofloxacin. Regarding Serratia marcescens, the drug resistance rates from high to low were 74.42% for cefotaxime, 72.09% for moxifloxacin, and 69.77% for gentamicin. Regarding Staphylococcus aureus in elderly patients with pulmonary infection, the drug resistance rates were 100.00% for penicillin, 61.54% for erythromycin, 61.54% for clarithromycin, and 61.54% for azithromycin. Regarding Candida albicans, the drug resistance rates from high to low were 22.41% for caspofungin, 15.52% for itraconazole, and 9.09% for fluconazole. The results of univariate analysis of pulmonary bacterial infection indicated that there were no significant differences in sex and body mass index between nonbacterial infection group and bacterial infection group (P > 0.05). There were significant differences in terms of dust or harmful gas exposure, family member smoking, chronic lung disease history, age, smoking, family cooking, hospital stay, and indwelling catheter (P < 0.05). Exposure to dust or harmful gases, family cooking, age, history of chronic lung disease, indwelling catheter, and length of hospital stay were risk factors for pulmonary bacterial infection (P < 0.05).

Conclusion

Gram-negative bacteria are the main pathogens in elderly patients with pulmonary infection. Antibiotics should be administered reasonably according to the results of the drug sensitivity test. Older age, history of chronic lung disease, catheter indwelling, and length of stay are the risk factors for pulmonary bacterial infection.

Mortality, seasonal variation, and susceptibility to acute exacerbation of COPD in the pandemic year: a nationwide population study

Background:

Previous studies have suggested that the coronavirus disease 2019 (COVID-19) pandemic was associated with a decreased rate of acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Data on how the COVID-19 pandemic has influenced mortality, seasonality of, and susceptibility to AECOPD in the chronic obstructive pulmonary disease (COPD) population is scarce.

Methods:

We conducted a national population-based retrospective study using data from the Health Insurance Institute of Slovenia from 2015 to February 2021, with 2015–2019 as the reference. We extracted patient and healthcare data for AECOPD, dividing AECOPD into severe, resulting in hospitalisation, and moderate, requiring outpatient care. The national COPD population was generated based on dispensed prescriptions of inhalation therapies, and moderate AECOPD events were analysed based on dispensed AECOPD medications. We extracted data on all-cause and non-COVID mortality.

Results:

The numbers of severe and moderate AECOPD were reduced by 48% and 34%, respectively, in 2020. In the pandemic year, the seasonality of AECOPD was reversed, with a 1.5-fold higher number of severe AECOPD in summer compared to winter. The proportion of frequent exacerbators (⩾2 AECOPD hospitalisations per year) was reduced by 9% in 2020, with a 30% reduction in repeated severe AECOPD in frequent exacerbators and a 34% reduction in persistent frequent exacerbators (⩾2 AECOPD hospitalisations per year for 2 consecutive years) from 2019. The risk of two or more moderate AECOPD decreased by 43% in 2020. In the multivariate model, pandemic year follow-up was the only independent factor associated with a decreased risk for severe AECOPD (hazard ratio [HR]: 0.71; 95% confidence interval [CI]: 0.61–0.84; p < 0.0001). In 2020, non-COVID mortality decreased (−15%) and no excessive mortality was observed in the COPD population.

Conclusion:

In the pandemic year, we found decreased susceptibility to AECOPD across severity spectrum of COPD, reversed seasonal distribution of severe AECOPD and decreased non-COVID mortality in the COPD population.

COVID-19 Pandemic: What Considerations Should Be Taken during the Assessment and Management of COPD Exacerbation?

The on-going coronavirus disease 2019 (COVID-19) pandemic could contribute to higher mortality in population with underlying respiratory diseases, including chronic obstructive pulmonary disease (COPD). The aim of this review was to inform readers pertaining to the correlation of COPD exacerbation and severe acute respiratory syndrome-2 (SARS-CoV-2) infection along with considerations that could be taken in the clinical diagnosis and management. The literature search was conducted on Google Scholar, Scopus, and PubMed databases using related terms (such as, but not limited to, “COVID-19,” “SARS-CoV-2,” “COPD management,” “N-acetylcysteine,” and “corticosteroids”) on November 1–9, 2021. Recent studies suggest that COVID-19 and COPD are correlated through three pathways, namely, angiotensin-converting enzyme 2 expression, dysregulation of biological parameters, and occurrence of pneumonia. Early detection of COVID-19 in patients with underlying COPD is difficult because they share similar symptoms, attributed to advanced progression of the infection and subsequently deteriorates lung function. During COPD management, clinicians are expected to take consideration on the effect of systemic corticosteroids if patients develop COVID-19. In conclusion, COVID-19 and COPD and its management are potentially correlated, contributing to the worsening of the disease. There is a need of immediate research to reveal the true correlation between COVID-19 and COPD to improve the management.

Characterization of the Human Oropharyngeal Microbiomes in SARS-CoV-2 Infection and Recovery Patients

Respiratory tract microbiome is closely related to respiratory tract infections, while characterization of oropharyngeal microbiome in recovered coronavirus disease 2019 (COVID-19) patients is not studied. Herein, oropharyngeal swabs are collected from confirmed cases (CCs) with COVID-19 (73 subjects), suspected cases (SCs) (36), confirmed cases who recovered (21), suspected cases who recovered (36), and healthy controls (Hs) (140) and then completed MiSeq sequencing. Oropharyngeal microbial α-diversity is markedly reduced in CCs versus Hs. Opportunistic pathogens are increased, while butyrate-producing genera are decreased in CCs versus Hs. The classifier based on eight optimal microbial markers is constructed through a random forest model and reached great diagnostic efficacy in both discovery and validation cohorts. Notably, the classifier successfully diagnosed SCs with positive IgG antibody as CCs and is demonstrated from the perspective of the microbiome. Importantly, several genera with significant differences gradually increase and decrease along with recovery from COVID-19. Forty-four oropharyngeal operational taxonomy units (OTUs) are closely correlated with 11 clinical indicators of SARS-CoV-2 infection and Hs based on Spearman correlation analysis. Together, this research is the first to characterize oropharyngeal microbiota in recovered COVID-19 cases and suspected cases, to successfully construct and validate the diagnostic model for COVID-19 and to depict the correlations between microbial OTUs and clinical indicators.

The Effectiveness of Influenza Vaccination on Chronic Obstructive Pulmonary Disease with Different Severities of Airflow Obstruction

This retrospective study included COPD patients who attended our medical center between January and October 2018, and analyzed the outcomes of their influenza vaccination, including medical visits, hospitalization, medical expenses, and the incidence of respiratory failure. Airflow limitation was stratified according to GOLD guidelines. Overall, 543 COPD patients were enrolled, including 197, 113, 126, and 107 mild, moderate, severe, and very severe patients, respectively. Of all the participants, 238 received an influenza vaccination (43.8%), which significantly reduced hospital utilization for moderate (odds ratio [OR] 0.22, 95%CI 0.09–0.51), severe (OR 0.19, 95%CI 0.08–0.44), and very severe patients (OR 0.15, 95%CI 0.05–0.5) compared to mild patients (OR 0.51, 95%CI 0.2–1.26); reduced emergency department utilization for moderate (OR 0.33, 95%CI 0.14–0.77), severe (OR 0.22, 95%CI 0.10–0.52), and very severe patients (OR 0.30, 95%CI 0.10–0.88) compared to mild patients (OR 0.64, 95%CI 0.30–1.37); and reduced the occurrence of respiratory failure for moderate (OR 0.20, 95%CI 0.06–0.68), severe (OR 0.40, 95%CI 0.16–0.98), and very severe patients (OR 0.36, 95%CI 0.15–0.82) compared to mild patients (OR 0% CI 0.14–3.20). Influenza vaccination is more effective in COPD patients with moderate, severe, and very severe airflow obstruction than in those with mild obstruction with respect to hospital utilization, emergency department utilization, and respiratory failure.

The potential impact of the COVID-19 pandemic on global antimicrobial and biocide resistance: an AMR Insights global perspective

The COVID-19 pandemic presents a serious public health challenge in all countries. However, repercussions of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections on future global health are still being investigated, including the pandemic's potential effect on the emergence and spread of global antimicrobial resistance (AMR). Critically ill COVID-19 patients may develop severe complications, which may predispose patients to infection with nosocomial bacterial and/or fungal pathogens, requiring the extensive use of antibiotics. However, antibiotics may also be inappropriately used in milder cases of COVID-19 infection. Further, concerns such as increased biocide use, antimicrobial stewardship/infection control, AMR awareness, the need for diagnostics (including rapid and point-of-care diagnostics) and the usefulness of vaccination could all be components shaping the influence of the COVID-19 pandemic. In this publication, the authors present a brief overview of the COVID-19 pandemic and associated issues that could influence the pandemic's effect on global AMR.

The Effect of Unconventional Cytokine Combinations on NK-Cell Responses to Viral Infection

Cytokines are soluble and membrane-bound factors that dictate immune responses. Dogmatically, cytokines are divided into families that promote type 1 cell-mediated immune responses (e.g., IL-12) or type 2 humoral responses (e.g., IL-4), each capable of antagonizing the opposing family of cytokines. The discovery of additional families of cytokines (e.g., IL-17) has added complexity to this model, but it was the realization that immune responses frequently comprise mixtures of different types of cytokines that dismantled this black-and-white paradigm. In some cases, one type of response may dominate these mixed milieus in disease pathogenesis and thereby present a clear therapeutic target. Alternatively, synergistic or blended cytokine responses may obfuscate the origins of disease and perplex clinical decision making. Most immune cells express receptors for many types of cytokines and can mediate a myriad of functions important for tolerance, immunity, tissue damage, and repair. In this review, we will describe the unconventional effects of a variety of cytokines on the activity of a prototypical type 1 effector, the natural killer (NK) cell, and discuss how this may impact the contributions of these cells to health and disease.

Specialized proresolving mediators in infection and lung injury

Specialized proresolving mediators (SPMs) are endogenous lipid metabolites of long-chain polyunsaturated fatty acids that are involved in promoting the resolution of inflammation. Many disease conditions characterized by excessive inflammation have impaired or altered SPM biosynthesis, which may lead to chronic, unresolved inflammation. Exogenous administration of SPMs in infectious conditions has been shown to be effective at improving infection clearance and survival in preclinical models. SPMs have also shown tremendous promise in the context of inflammatory lung conditions, such as acute respiratory distress syndrome and chronic obstructive pulmonary disease, mostly in preclinical settings. To date, SPMs have not been studied in the context of the novel Coronavirus, severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2), however their preclinical efficacy in combatting infections and improving acute respiratory distress suggest they may be a valuable resource in the fight against Coronavirus disease-19 (COVID-19). Overall, while the research on SPMs is still evolving, they may offer a novel therapeutic option for inflammatory conditions.

Role of specialized pro-resolving lipid mediators and their receptors in virus infection: a promising therapeutic strategy for SARS-CoV-2 cytokine storm

Unexpected viral infections outbreaks, significantly affect human health, leading to increased mortality and life disruption. Among them is the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which emerged as a deadly pandemic, calling for intense research efforts on its pathogenicity mechanism and development of therapeutic strategies. In the SARS-CoV-2 cytokine storm, systemic inflammation has been associated with severe illness and mortality. Recent studies have demonstrated special pro-resolving lipids mediators (SPMs) lipoxins, resolvins, maresins, and protectins as potential therapeutic options for abnormal viral-triggered inflammation. Pro-resolving lipids mediators have shown great promise for the treatment of Herpes simplex virus, respiratory syncytial virus, human immunodeficiency virus, and hepatitis C virus. Based on this, studies are being conducted on their therapeutic effects in SARS-CoV-2 infection. In this review, we discussed SPMs and reviewed evidence from recent studies on SPMs as therapeutic options for viral infections, including SARS-CoV2. Based on our analysis of the previous study, we argue that SPMs are a potential treatment for SARS-CoV-2 infection and other viral infections. We expect further research on how SPMs modulate viral-triggered inflammation through G-protein-coupled receptors (GPCRs), and chemical stability and druggability of SPMs.

Specialized Proresolving Mediators Overcome Immune Suppression Induced by Exposure to Secondhand Smoke

Tobacco smoke exposure is associated with multiple diseases including, respiratory diseases like asthma and chronic obstructive pulmonary disease. Tobacco smoke is a potent inflammatory trigger and is immunosuppressive, contributing to increased susceptibility to pulmonary infections in smokers, ex-smokers, and vulnerable populations exposed to secondhand smoke. Tobacco smoke exposure also reduces vaccine efficacy. Therefore, mitigating the immunosuppressive effects of chronic smoke exposure and improving the efficacy of vaccinations in individuals exposed to tobacco smoke, is a critical unmet clinical problem. We hypothesized that specialized proresolving mediators (SPMs), a class of immune regulators promoting resolution of inflammation, without being immunosuppressive, and enhancing B cell Ab responses, could reverse the immunosuppressive effects resulting from tobacco smoke exposure. We exposed mice to secondhand smoke for 8 wk, followed by a period of smoke exposure cessation, and the mice were immunized with the P6 lipoprotein from nontypeable Haemophilus influenzae, using 17-HDHA and aspirin-triggered-resolvin D1 (AT-RvD1) as adjuvants. 17-HDHA and AT-RvD1 used as adjuvants resulted in elevated serum and bronchoalveolar lavage levels of anti-P6-specific IgG and IgA that were protective, with immunized mice exhibiting more rapid bacterial clearance upon challenge, reduced pulmonary immune cell infiltrates, reduced production of proinflammatory cytokines, and less lung-epithelial cell damage. Furthermore, the treatment of mice with AT-RvD1 during a period of smoke-cessation further enhanced the efficacy of SPM-adjuvanted P6 vaccination. Overall, SPMs show promise as novel vaccine adjuvants with the ability to overcome the tobacco smoke-induced immunosuppressive effects.

COVID-19 Susceptibility in chronic obstructive pulmonary disease

In barely nine months, the pandemic known as COVID-19 has spread over 200 countries, affecting more than 22 million people and causing over than 786 000 deaths. Elderly people and patients with previous comorbidities such as hypertension and diabetes are at an increased risk to suffer a poor prognosis after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Although the same could be expected from patients with chronic obstructive pulmonary disease (COPD), current epidemiological data are conflicting. This could lead to a reduction of precautionary measures in these patients, in the context of a particularly complex global health crisis. Most COPD patients have a long history of smoking or exposure to other harmful particles or gases, capable of impairing pulmonary defences even years after the absence of exposure. Moreover, COPD is characterized by an ongoing immune dysfunction, which affects both pulmonary and systemic cellular and molecular inflammatory mediators. Consequently, increased susceptibility to viral respiratory infections have been reported in COPD, often worsened by bacterial co-infections and leading to serious clinical outcomes. The present paper is an up-to-date review that discusses the available research regarding the implications of coronavirus infection in COPD. Although validation in large studies is still needed, COPD likely increases SARS-CoV-2 susceptibility and increases COVID-19 severity. Hence, specific mechanisms to monitor and assess COPD patients should be addressed in the current pandemic.

Microbiome in Chronic Obstructive Pulmonary Disease: Role of Natural Products Against Microbial Pathogens

The "microbiome" is the operative term to refer to a collection of all taxa constituting microbial communities, such as bacteria, archaea, fungi and protists (originally microbiota). The microbiome consists of the indigenous microbial communities and of the host environment that they inhabit. Actually, it has been shown that there is a close relationship between the microbiome and human health and disease condition. Although, initially, the lung was considered sterile, actually, the existence of a healthy lung microbiome is usually accepted. Lung microbiome changes are reported in Chronic Obstructive Pulmonary Disease (COPD) and in its exacerbation. Viral and bacterial infections of the respiratory system are a major cause of COPD exacerbations (AECOPD) leading to increased local and systemic inflammation. Detection rates of virus in AECOPD are variable between 25-62% according to the detection method. The study of human airway and lung disease virome is quite recent and still very limited. The purpose of this review is to summarize recent findings on the lung microbiome composition with a special emphasis on virome in COPD and in AECOPD. Some drugs of natural origins active against resistant bacteria and virus are described.

Secondary Bacterial Infections in Patients With Viral Pneumonia

Pulmonary diseases of viral origin are often followed by the manifestation of secondary infections, leading to further clinical complications and negative disease outcomes. Thus, research on secondary infections is essential. Here, we review clinical data of secondary bacterial infections developed after the onset of pulmonary viral infections. We review the most recent clinical data and current knowledge of secondary bacterial infections and their treatment in SARS-CoV-2 positive patients; case reports from SARS-CoV, MERS-CoV, SARS-CoV2 and the best-studied respiratory virus, influenza, are described. We outline treatments used or prophylactic measures employed for secondary bacterial infections. This evaluation includes recent clinical reports of pulmonary viral infections, including those by COVID-19, that reference secondary infections. Where data was provided for COVID-19 patients, a mortality rate of 15.2% due to secondary bacterial infections was observed for patients with pneumonia (41 of 268). Most clinicians treated patients with SARS-CoV-2 infections with prophylactic antibiotics (63.7%, n = 1,901), compared to 73.5% (n = 3,072) in all clinical reports of viral pneumonia included in this review. For all cases of viral pneumonia, a mortality rate of 10.9% due to secondary infections was observed (53 of 482). Most commonly, quinolones, cephalosporins and macrolides were administered, but also the glycopeptide vancomycin. Several bacterial pathogens appear to be prevalent as causative agents of secondary infections, including antibiotic-resistant strains of Staphylococcus aureus and Klebsiella pneumoniae.

Risk factors for postoperative delirium after spinal surgery: a systematic review and meta-analysis

BACKGROUND

Postoperative delirium is common in older patients after spinal surgery. Many reports investigating the risk factors for delirium after spinal surgery have been published recently.

METHODS

A literature search was performed using the Cochrane Library, Web of Science, PubMed, Embase, and Springer databases from inception to February 2019. Relevant studies involving patients with delirium who underwent spinal surgery were included if the studies contained data about blood transfusion or other related factors, such as haemoglobin, haematocrit, and blood loss levels. The Newcastle-Ottawa Scale was used for the study-quality evaluation. The pooled odds ratios or (standard) mean differences of the individual risk factors were estimated using the Mantel-Haenszel or inverse-variance methods.

RESULTS

Fifteen observational studies met the inclusion criteria; the studies included a total of 583,290 patients (5431 patients with delirium and 577,859 patients without delirium). In addition to an advanced age, the results of the meta-analyses showed that living in an institution, diabetes, cerebral vascular diseases, pulmonary diseases, opioid use, length of surgery, intraoperative blood loss, blood transfusions, intraoperative infusion, preoperative albumin, postoperative albumin, preoperative haematocrit, postoperative haematocrit, preoperative haemoglobin, postoperative haemoglobin, preoperative sodium, postoperative sodium, Mini-Mental State Examination score, inability to ambulate, depression, number of medications, and treatment with multiple drugs (> three types) were significantly associated with delirium.

CONCLUSION

The above-mentioned risk factors can be used to identify high-risk patients, and the appropriate prophylaxis strategies should be implemented to prevent delirium after spinal surgery.

Impact of the Local Inflammatory Environment on Mucosal Vitamin D Metabolism and Signaling in Chronic Inflammatory Lung Diseases

Vitamin D plays an active role in the modulation of innate and adaptive immune responses as well as in the protection against respiratory pathogens. Evidence for this immunomodulatory and protective role is derived from observational studies showing an association between vitamin D deficiency, chronic airway diseases and respiratory infections, and is supported by a range of experimental studies using cell culture and animal models. Furthermore, recent intervention studies have now shown that vitamin D supplementation reduces exacerbation rates in vitamin D-deficient patients with chronic obstructive pulmonary disease (COPD) or asthma and decreases the incidence of acute respiratory tract infections. The active vitamin D metabolite, 1,25-dihydroxy-vitamin D (1,25(OH)₂D), is known to contribute to the integrity of the mucosal barrier, promote killing of pathogens (via the induction of antimicrobial peptides), and to modulate inflammation and immune responses. These mechanisms may partly explain its protective role against infections and exacerbations in COPD and asthma patients. The respiratory mucosa is an important site of local 1,25(OH)₂D synthesis, degradation and signaling, a process that can be affected by exposure to inflammatory mediators. As a consequence, mucosal inflammation and other disease-associated factors, as observed in e.g., COPD and asthma, may modulate the protective actions of 1,25(OH)₂D. Here, we discuss the potential consequences of various disease-associated processes such as inflammation and exposure to pathogens and inhaled toxicants on vitamin D metabolism and local responses to 1,25(OH)₂D in both immune- and epithelial cells. We furthermore discuss potential consequences of disturbed local levels of 25(OH)D and 1,25(OH)₂D for chronic lung diseases. Additional insight into the relationship between disease-associated mechanisms and local effects of 1,25(OH)₂D is expected to contribute to the design of future strategies aimed at improving local levels of 1,25(OH)₂D and signaling in chronic inflammatory lung diseases.

Recent Advances in the Management of Acute Exacerbations of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease is a chronic, irreversible obstructive lung disease that results from exposure to noxious stimuli. Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) usually result from viral or bacterial respiratory infections, but may also result from exposure to environmental pollution. AECOPD are associated with functional decline, increased risk of subsequent exacerbations, and death. Despite the poor prognosis of AECOPD, patients are empowered through self-management programs in their battle against this lethal disease. Morbidity and mortality of chronic obstructive pulmonary disease hospitalizations are reduced by implementing standardized treatment modalities outlined in this article throughout the hospitalization and beyond.

Secondary Bacterial Infections During Pulmonary Viral Disease: Phage Therapeutics as Alternatives to Antibiotics?

Secondary bacterial infections manifest during or after a viral infection(s) and can lead to negative outcomes and sometimes fatal clinical complications. Research and development of clinical interventions is largely focused on the primary pathogen, with research on any secondary infection(s) being neglected. Here we highlight the impact of secondary bacterial infections and in particular those caused by antibiotic-resistant strains, on disease outcomes. We describe possible non-antibiotic treatment options, when small molecule drugs have no effect on the bacterial pathogen and explore the potential of phage therapy and phage-derived therapeutic proteins and strategies in treating secondary bacterial infections, including their application in combination with chemical antibiotics.

Use of DAMPs and SAMPs as Therapeutic Targets or Therapeutics: A Note of Caution

This opinion article discusses the increasing attention paid to the role of activating damage-associated molecular patterns (DAMPs) in initiation of inflammatory diseases and suppressing/inhibiting DAMPs (SAMPs) in resolution of inflammatory diseases and, consequently, to the future roles of these novel biomarkers as therapeutic targets and therapeutics. Since controlled production of DAMPs and SAMPs is needed to achieve full homeostatic restoration and repair from tissue injury, only their pathological, not their homeostatic, concentrations should be therapeutically tackled. Therefore, distinct caveats are proposed regarding choosing DAMPs and SAMPs for therapeutic purposes. For example, we discuss the need to a priori identify and define a context-dependent “homeostatic DAMP:SAMP ratio” in each case and a “homeostatic window” of DAMP and SAMP concentrations to guarantee a safe treatment modality to patients. Finally, a few clinical examples of how DAMPs and SAMPs might be used as therapeutic targets or therapeutics in the future are discussed, including inhibition of DAMPs in hyperinflammatory processes (e.g., systemic inflammatory response syndrome, as currently observed in Covid-19), administration of SAMPs in chronic inflammatory diseases, inhibition of SAMPs in hyperresolving processes (e.g., compensatory anti-inflammatory response syndrome), and administration/induction of DAMPs in vaccination procedures and anti-cancer therapy.

CUL1-Mediated Organelle Fission Pathway Inhibits the Development of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a global high-incidence chronic airway inflammation disease. Its deterioration will lead to more serious lung lesions and even lung cancer. Therefore, it is urgent to determine the pathogenesis of COPD and find potential therapeutic targets. The purpose of this study is to reveal the molecular mechanism of COPD disease development through in-depth analysis of transcription factors and ncRNA-driven pathogenic modules of COPD. We obtained the expression profile of COPD-related microRNAs from the NCBI-GEO database and analyzed the differences among groups to identify the microRNAs significantly associated with COPD. Then, their target genes are predicted and mapped to a protein-protein interaction (PPI) network. Finally, key transcription factors and the ncRNA of the regulatory module were identified based on the hypergeometric test. The results showed that CUL1 was the most interactive gene in the highly interactive module, so it was recognized as a dysfunctional molecule of COPD. Enrichment analysis also showed that it was much involved in the biological process of organelle fission, the highest number of regulatory modules. In addition, ncRNAs, mainly composed of miR-590-3p, miR-495-3p, miR-186-5p, and transcription factors such as MYC, BRCA1, and CDX2, significantly regulate COPD dysfunction blocks. In summary, we revealed that the COPD-related target gene CUL1 plays a key role in the potential dysfunction of the disease. It promotes the proliferation of fibroblast cells in COPD patients by mediating functional signals of organelle fission and thus participates in the progress of the disease. Our research helps biologists to further understand the etiology and development trend of COPD.

The Impact of Type 1 Interferons on Alveolar Macrophage Tolerance and Implications for Host Susceptibility to Secondary Bacterial Pneumonia

That macrophages adapt to environmental cues is well-established. This adaptation has had several reiterations, first with innate imprinting and then with various combinations of trained, tolerant, paralyzed, or primed. Whatever the nomenclature, it represents a macrophage that is required to perform very different functions. First, alveolar macrophages are one of the sentinel cells that flag up damage and release mediators that attract other immune cells. Next, they mature to support T cell priming and survival. Finally they are critical in clearing inflammatory immune cells by phagocytosis and extracellular matrix turnover components by efferocytosis. At each functional stage they alter intrinsic components to guide their activity. Training therefore is akin to changing function. In this mini-review we focus on the lung and the specific role of type I interferons in altering macrophage activity. The proposed mechanisms of type I IFNs on lung-resident alveolar macrophages and their effect on host susceptibility to bacterial infection following influenza virus infection.

Respiratory Viral Infections in Exacerbation of Chronic Airway Inflammatory Diseases: Novel Mechanisms and Insights From the Upper Airway Epithelium

Respiratory virus infection is one of the major sources of exacerbation of chronic airway inflammatory diseases. These exacerbations are associated with high morbidity and even mortality worldwide. The current understanding on viral-induced exacerbations is that viral infection increases airway inflammation which aggravates disease symptoms. Recent advances in in vitro air-liquid interface 3D cultures, organoid cultures and the use of novel human and animal challenge models have evoked new understandings as to the mechanisms of viral exacerbations. In this review, we will focus on recent novel findings that elucidate how respiratory viral infections alter the epithelial barrier in the airways, the upper airway microbial environment, epigenetic modifications including miRNA modulation, and other changes in immune responses throughout the upper and lower airways. First, we reviewed the prevalence of different respiratory viral infections in causing exacerbations in chronic airway inflammatory diseases. Subsequently we also summarized how recent models have expanded our appreciation of the mechanisms of viral-induced exacerbations. Further we highlighted the importance of the virome within the airway microbiome environment and its impact on subsequent bacterial infection. This review consolidates the understanding of viral induced exacerbation in chronic airway inflammatory diseases and indicates pathways that may be targeted for more effective management of chronic inflammatory diseases.

Pneumonia in exacerbations of COPD: what is the clinical significance?

Does it matter if a patient presenting with an exacerbation of COPD (ECOPD) is found to have consolidation on imaging? In the 2010 European COPD Audit, which included 14 111 patients from 384 hospitals in 13 countries with a primary discharge diagnosis of ECOPD, ∼20% had concomitant consolidation on admission chest radiography [1]. Crucially, the presence of consolidation was associated with increased 90-day mortality in this cohort (adjusted OR 1.36, 95% CI 1.2–1.55) [1]. Similar findings were seen in the large 2014 UK National COPD Audit, which found that ECOPD patients with consolidation experienced increased in-hospital mortality (6.7% versus 3.6%, p<0.001) and increased 90-day mortality (15.9% versus 10.8%, p<0.001) compared to patients without consolidation [2].

It is vital that clinicians identify radiological consolidation in hospitalised COPD patients, as this confers an increased mortality risk, has important implications for risk stratification and influences managementhttp://bit.ly/2q2vH2J

Emerging Principles in Myelopoiesis at Homeostasis and during Infection and Inflammation

Myelopoiesis ensures the steady state of the myeloid cell compartment. Technological advances in fate mapping and genetic engineering, as well as the advent of single cell RNA-sequencing, have highlighted the heterogeneity of the hematopoietic system and revealed new concepts in myeloid cell ontogeny. These technologies are also shedding light on mechanisms of myelopoiesis at homeostasis and at different phases of infection and inflammation, illustrating important feedback loops between affected tissues and the bone marrow. We review these findings here and revisit principles in myelopoiesis in light of the evolving understanding of myeloid cell ontogeny and heterogeneity. We argue for the importance of system-wide evaluation of changes in myelopoiesis and discuss how even after the resolution of inflammation, long-lasting alterations in myelopoiesis may play a role in innate immune memory or trained immunity.

New therapeutic targets for the prevention of infectious acute exacerbations of COPD: role of epithelial adhesion molecules and inflammatory pathways

Chronic respiratory diseases are among the leading causes of mortality worldwide, with the major contributor, chronic obstructive pulmonary disease (COPD) accounting for approximately 3 million deaths annually. Frequent acute exacerbations (AEs) of COPD (AECOPD) drive clinical and functional decline in COPD and are associated with accelerated loss of lung function, increased mortality, decreased health-related quality of life and significant economic costs. Infections with a small subgroup of pathogens precipitate the majority of AEs and consequently constitute a significant comorbidity in COPD. However, current pharmacological interventions are ineffective in preventing infectious exacerbations and their treatment is compromised by the rapid development of antibiotic resistance. Thus, alternative preventative therapies need to be considered. Pathogen adherence to the pulmonary epithelium through host receptors is the prerequisite step for invasion and subsequent infection of surrounding structures. Thus, disruption of bacterial-host cell interactions with receptor antagonists or modulation of the ensuing inflammatory profile present attractive avenues for therapeutic development. This review explores key mediators of pathogen-host interactions that may offer new therapeutic targets with the potential to prevent viral/bacterial-mediated AECOPD. There are several conceptual and methodological hurdles hampering the development of new therapies that require further research and resolution.

New frontiers in the treatment of comorbid cardiovascular disease in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a disease characterised by persistent airflow limitation that is not fully reversible and is currently the fourth leading cause of death globally. It is now well established that cardiovascular-related comorbidities contribute to morbidity and mortality in COPD, with approximately 50% of deaths in COPD patients attributed to a cardiovascular event (e.g. myocardial infarction). Cardiovascular disease (CVD) and COPD share various risk factors including hypertension, sedentarism, smoking and poor diet but the underlying mechanisms have not been fully established. However, there is emerging and compelling experimental and clinical evidence to show that increased oxidative stress causes pulmonary inflammation and that the spill over of pro-inflammatory mediators from the lungs into the systemic circulation drives a persistent systemic inflammatory response that alters blood vessel structure, through vascular remodelling and arterial stiffness resulting in atherosclerosis. In addition, regulation of endothelial-derived vasoactive substances (e.g. nitric oxide (NO)), which control blood vessel tone are altered by oxidative damage of vascular endothelial cells, thus promoting vascular dysfunction, a key driver of CVD. In this review, the detrimental role of oxidative stress in COPD and comorbid CVD are discussed and we propose that targeting oxidant-dependent mechanisms represents a novel strategy in the treatment of COPD-associated CVD.

Tissue kallikrein regulates alveolar macrophage apoptosis early in influenza virus infection

Host cell proteases are involved in influenza pathogenesis. We examined the role of tissue kallikrein 1 (KLK1) by comparing wild-type (WT) and KLK1-deficient mice infected with influenza H3N2 virus. The levels of KLK1 in lung tissue and in bronchoalveolar lavage (BAL) fluid increased substantially during infection. KLK1 did not promote virus infectivity despite its trypsin-like activity, but it did decrease the initial virus load. We examined two cell types involved in the early control of pathogen infections, alveolar macrophages (AMs) and natural killer (NK) cells to learn more about the antiviral action of KLK1. Inactivating the Klk1 gene or treating WT mice with an anti-KLK1 monoclonal antibody to remove KLK1 activity accelerated the initial virus-induced apoptotic depletion of AMs. Intranasal instillation of deficient mice with recombinant KLK1 (rKLK1) reversed the phenotype. The levels of granulocyte-macrophage colony-stimulating factor in infected BAL fluid were significantly lower in KLK1-deficient mice than in WT mice. Treating lung epithelial cells with rKLK1 increased secretion of this factor known to enhance AM resistance to pathogen-induced apoptosis. The recruitment of NK cells to the air spaces peaked 3 days after infection in WT mice but not in KLK1-deficient mice, as did increases in several NK-attracting chemokines (CCL2, CCL3, CCL5, and CXCL10) in BAL. Chronic obstructive pulmonary disease (COPD) patients are highly susceptible to viral infection, and we observed that the KLK1 mRNA levels decreased with increasing COPD severity. Our findings indicate that KLK1 intervenes early in the antiviral defense modulating the severity of influenza infection. Decreased KLK1 expression in COPD patients could contribute to the worsening of influenza.