Innate Immune Responses by Respiratory Viruses, Including Rhinovirus, During Asthma Exacerbation

Viral infections causing asthma exacerbations in the age of biologics and the COVID-19 pandemic

PURPOSE OF REVIEW

Asthma exacerbations are associated with substantial symptom burden and healthcare costs. Viral infections are the most common identified cause of asthma exacerbations. The epidemiology of viral respiratory infections has undergone a significant evolution during the COVID-19 pandemic. The relationship between viruses and asthmatic hosts has long been recognized but it is still incompletely understood. The use of newly approved asthma biologics has helped us understand this interaction better.

RECENT FINDINGS

We review recent updates on the interaction between asthma and respiratory viruses, and we address how biologics and immunotherapies could affect this relationship by altering the respiratory mucosa cytokine milieu. By exploring the evolving epidemiological landscape of viral infections during the different phases of the COVID-19 pandemic, we emphasize the early post-pandemic stage, where a resurgence of pre-pandemic viruses with atypical seasonality patterns occurred. Finally, we discuss the newly developed RSV and SARS-CoV-2 vaccines and how they reduce respiratory infections.

SUMMARY

Characterizing how respiratory viruses interact with asthmatic hosts will allow us to identify tailored therapies to reduce the burden of asthma exacerbations. New vaccination strategies are likely to shape the future viral asthma exacerbation landscape.

Multifactorial Causes and Consequences of TLSP Production, Function, and Release in the Asthmatic Airway

Disruption of the airway epithelium triggers a defensive immune response that begins with the production and release of alarmin cytokines. These epithelial-derived alarmin cytokines, including thymic stromal lymphopoietin (TSLP), are produced in response to aeroallergens, viruses, and toxic inhalants. An alarmin response disproportionate to the inhaled trigger can exacerbate airway diseases such as asthma. Allergens inhaled into previously sensitized airways are known to drive a T2 inflammatory response through the polarization of T cells by dendritic cells mediated by TSLP. Harmful compounds found within air pollution, microbes, and viruses are also triggers causing airway epithelial cell release of TSLP in asthmatic airways. The release of TSLP leads to the development of inflammation which, when unchecked, can result in asthma exacerbations. Genetic and inheritable factors can contribute to the variable expression of TSLP and the risk and severity of asthma. This paper will review the various triggers and consequences of TSLP release in asthmatic airways.

Global prevalence of infections in newborns with respiratory complications: systematic review and meta-analysis

Background and Objectives

Newborns as a vulnerable population are exposed to congenital and acquired infections during and after birth. There are several reports of the isolation and reporting of infectious agents (IAs) in early life of newborns with respiratory manifestations, and the present comprehensive study provides a snapshot of the current global situation of the prevalence of IAs in newborns with respiratory symptoms.

Materials and Methods

A systematic search was conducted in main databases, including PubMed, Scopus, Web of science, and Google scholar. The pooled prevalence of infectious agents (IAs) in newborns was estimated using comprehensive meta-analysis software based on random effects model.

Results

Out of 44 inclusive studies (50 datasets) for IAs in newborns, the pooled prevalence was estimated to be 12.2% (95% CI: 6.40-22.0%) and the highest and lowest prevalence of IAs was related to the Brazil (78.2%, 95% CI: 31.0-96.6%), and UK (0.01%, 95% CI 0.01-0.01%) respectively.

Conclusion

The high prevalence of IAs in newborns emphasizes considers the necessary measures to prevent respiratory infections.

Daqing formula ameliorated allergic asthma and airway dysbacteriosis in mice challenged with ovalbumin and ampicillin

ETHNOPHARMACOLOGICAL RELEVANCE

Asthma is a chronic airway inflammatory disease that can lead to several complications caused by bacterial infections. However, recurrent attacks of the disease require long-term use of antibiotics, resulting in lung dysbiosis and poor outcomes. Daqing Formula (DQF) is a well-known herbal medicine in Pharmacopoeia of China, which is widely used for various stimuli-induced lower respiratory diseases, including asthma, bronchitis, and pneumonia. Thus, it has been demonstrated to be a plant-derived broad-spectrum antibiotic for treating and preventing various acute and chronic respiratory diseases.

AIM OF THE STUDY

This study evaluated the efficacy and possible mechanism of DQF on allergic asthma and airway dysbiosis.

METHODS AND MATERIALS

The mice were co-challenged with ovalbumin and ampicillin to induce allergic asthma combined with airway dysbacteriosis. The populations of lung microbiota were detected by using 16s DNA sequencing. The levels of asthmatic markers in BALF were detected by ELISA. The levels of Th1/Th2 cytokines in splenic CD4+ cells of mice were analyzed by flow cytometry. The expressions of the GSK-3β signaling pathway in the lung tissues of asthmatic mice and eosinophils were detected by western blotting assay. The inhibition of DQF on the production of pro-inflammatory cytokines in eosinophils of asthmatic mice.

RESULTS

The results showed that treatment with DQF at 200-800 mg/kg doses significantly reduced the frequency of nasal rubbing and lung inflammation as well as the number of total cells, eosinophils, and macrophages in bronchoalveolar lavage fluid. It decreased the relative abundances of Streptococcus, Cuoriavidus, and Moraxella, increased Akkermansia and Prevotella_6 in lung tissues of asthmatic mice, and inhibited the growth of Staphylococcus aureus, Klebsiella pneumoniae, Streptococcus pneumoniae and their resistant strains in vitro. Furthermore, DQF reduced the levels of eotaxin, TSLP, IL-4, IL-5, IL-25, and IL-33, but enhanced IFN-γ and IL-12 in BALF. It elevated the population of Th1 cells, inhibited eosinophil activation, and downregulated the expressions of p-GSK-3β, p-p65, nuclear β-catenin, and p-STAT3 in the lung tissues of asthmatic mice.

CONCLUSIONS

The results revealed that DQF reduced airway inflammation, ameliorated lung dysbiosis, shifted the Th1/Th2 balance, and inhibited eosinophil activation in asthmatic mice, indicating its potential for severe asthma treatment.

Cullin5 drives experimental asthma exacerbations by modulating alveolar macrophage antiviral immunity

Asthma exacerbations caused by respiratory viral infections are a serious global health problem. Impaired antiviral immunity is thought to contribute to the pathogenesis, but the underlying mechanisms remain understudied. Here using mouse models we find that Cullin5 (CUL5), a key component of Cullin-RING E3 ubiquitin ligase 5, is upregulated and associated with increased neutrophil count and influenza-induced exacerbations of house dust mite-induced asthma. By contrast, CUL5 deficiency mitigates neutrophilic lung inflammation and asthma exacerbations by augmenting IFN-β production. Mechanistically, following thymic stromal lymphopoietin stimulation, CUL5 interacts with O-GlcNAc transferase (OGT) and induces Lys48-linked polyubiquitination of OGT, blocking the effect of OGT on mitochondrial antiviral-signaling protein O-GlcNAcylation and RIG-I signaling activation. Our results thus suggest that, in mouse models, pre-existing allergic injury induces CUL5 expression, impairing antiviral immunity and promoting neutrophilic inflammation for asthma exacerbations. Targeting of the CUL5/IFN-β signaling axis may thereby serve as a possible therapy for treating asthma exacerbations.

Atopic March or Atopic Multimorbidity-Overview of Current Research

The atopic march encompasses a sequence of allergic conditions, including atopic dermatitis, food allergy, allergic rhinitis, and asthma, that frequently develop in a sequential pattern within the same individual. It was introduced as a conceptual framework aimed at elucidating the developmental trajectory of allergic conditions during childhood. Following the introduction of this concept, it was initially believed that the atopic march represented the sole and definitive trajectory of the development of allergic diseases. However, this perspective evolved with the emergence of new longitudinal studies, which revealed that the evolution of allergic diseases is far more intricate. It involves numerous immunological pathological mechanisms and may not align entirely with the traditional concept of the atopic march. The objective of our review is to portray the atopic march alongside other patterns in the development of childhood allergic diseases, with a specific emphasis on the potential for a personalized approach to the prevention, diagnosis, and treatment of atopic conditions.

CXCL10-based gene cluster model serves as a potential diagnostic biomarker for premature ovarian failure

Objective

Premature ovarian failure (POF) is a disease with high clinical heterogeneity. Subsequently, its diagnosis is challenging. CXCL10 which is a small signaling protein involved in immune response and inflammation may have diagnostic potential in detection of premature ovarian insufficiency. Therefore, this study aimed to investigate CXCL10 based diagnostic biomarkers for POF.

Methods

Transcriptome data for POF was obtained from the Gene Expression Omnibus (GEO) database (GSE39501). Principal component analysis (PCA) assessed CXCL10 expression in patients with POF. The receiver operating characteristic (ROC) curve, analyzed using PlotROC, demonstrated the diagnostic potential of CXCL10 and CXCL10-based models for POF. Differentially expressed genes (DEGs) in the control group of POF were identified using DEbylimma. PlotVenn was used to determine the overlap between the POF-control group and the high-/low-expression CXCL10 groups. QuadrantPlot was employed to detect CXCL10-dysregulated genes in POF. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA) were conducted on DEGs using RunMulti Group cluster Profiler. A POF model was induced with cisplatin (DDP) using KGN cells. RT-qPCR and Western blot were used to measure the expression of CXCL10, apoptosis-related proteins, and peroxisome proliferator-activated receptor (PPAR) signaling pathway-related proteins in this model, following siRNA-mediated silencing of CXCL10. Flow cytometry was employed to assess the apoptosis of KGN cells after CXCL10 downregulation.

Results

The expression of CXCL10 is dysregulated in POF, and it shows promising diagnostic potential for POF, as evidenced by an area under the curve value of 1. In POF, we found 3,362 up-regulated and 3,969 down-regulated DEGs compared to healthy controls, while the high- and low-expression groups of POF (comprising samples above and below the median CXCL10 expression) exhibited 1,304 up-regulated and 1,315 down-regulated DEGs. Among these, 786 DEGs consistently displayed dysregulation in POF due to CXCL10 influence. Enrichment analysis indicated that the PPAR signaling pathway was activated by CXCL10 in POF. The CXCL10-based model (including CXCL10, Itga2, and Raf1) holds potential as a diagnostic biomarker for POF. Additionally, in the DDP-induced KGN cell model, interfering with CXCL10 expression promoted the secretion of estradiol, and reduced apoptosis. Furthermore, CXCL10 silencing led to decreased expression levels of PPARβ and long-chain acyl-CoA synthetase 1 compared to the Si-NC group. These results suggest that CXCL10 influences the progression of POF through the PPAR signaling pathway.

Conclusion

The CXCL10-based model, demonstrating perfect diagnostic accuracy for POF and comprising CXCL10, Itga2, and Raf1, holds potential as a valuable diagnostic biomarker. Thus, the expression levels of these genes may collectively provide valuable diagnostic information for POF.

Development of a Melting-Curve-Based Multiplex Real-Time PCR Assay for the Simultaneous Detection of Viruses Causing Respiratory Infection

The prompt and accurate identification of the etiological agents of viral respiratory infections is a critical measure in mitigating outbreaks. In this study, we developed and clinically evaluated a novel melting-curve-based multiplex real-time PCR (M-m-qPCR) assay targeting the RNA-dependent RNA polymerase (RdRp) and nucleocapsid phosphoprotein N of SARS-CoV-2, the Matrix protein 2 of the Influenza A virus, the RdRp domain of the L protein from the Human Respiratory Syncytial Virus, and the polyprotein from Rhinovirus B genes. The analytical performance of the M-m-qPCR underwent assessment using in silico analysis and a panel of reference and clinical strains, encompassing viral, bacterial, and fungal pathogens, exhibiting 100% specificity. Moreover, the assay showed a detection limit of 10 copies per reaction for all targeted pathogens using the positive controls. To validate its applicability, the assay was further tested in simulated nasal fluid spiked with the viruses mentioned above, followed by validation on nasopharyngeal swabs collected from 811 individuals. Among them, 13.4% (109/811) tested positive for SARS-CoV-2, and 1.1% (9/811) tested positive for Influenza A. Notably, these results showed 100% concordance with those obtained using a commercial kit. Therefore, the M-m-qPCR exhibits great potential for the routine screening of these respiratory viral pathogens.

The upregulation of peripheral CD3-CD56+CD16+ natural killer cells correlates with Th1/Th2 imbalance in asthma patients during acute upper respiratory viral infections

PURPOSE

The aim of this study is to clarify the changes of peripheral CD3-CD56+CD16+ NK cells and their correlation with Th1/Th2 immunity profiles in asthma during the phase of acute upper respiratory viral infections (AURVIs).

METHODS

Peripheral venous blood and induced sputum samples were collected from 56 mild asthma patients, 49 asthma patients with AURVIs and 50 healthy subjects. Peripheral CD3-CD56+CD16+ NK cells were monitored by flow cytometry during the course of acute viral infections. Meanwhile, the induced sputum Th2 cytokines IL-4 and IL-5, and Th1 cytokine IFN-γ were also detected by ELISA assay.

RESULTS

The asthmatics had lower levels of peripheral CD3-CD56+CD16+ NK cells populations as well as higher induced sputum cytokines (IL-4, IL-5 and IFN-γ) compared to healthy controls at baseline. Upon upper respiratory viral infections, peripheral CD3-CD56+CD16+ NK cells numbers in asthma patients sharply elevated on day 3 and slowly decreased by day 14, in accordance with induced sputum IFN-γ changes. IL-4 and IL-5 levels spiked much later (day 8) and lasted until day 14. Compared with asthma alone group, the IFN-γ/IL-4 and IFN-γ/IL-5 ratios of the asthma patients with AURVIs on day 1 were higher and peaked on day 3. The changes of peripheral CD3-CD56+CD16+ NK cells proportions positively correlated with the IFN-γ/IL-4 and IFN-γ/IL-5 ratios on day 1 to day 3 in asthma subsequent to upper respiratory viral infections.

CONCLUSIONS

Our findings showed an imbalanced Th1/Th2 immunity in airways of asthma with acute upper respiratory viral infections. Upregulated peripheral CD3-CD56+CD16+ NK cells play a crucial role in biased Th1 immunity of airways in asthma during the acute phase of viral infections. The anti-viral Th1 immunity by targeting NK cells may be a possible therapeutic option for virus-induced asthma exacerbation.

Rhinovirus induces airway remodeling: what are the physiological consequences?

BACKGROUND

Rhinovirus infections commonly evoke asthma exacerbations in children and adults. Recurrent asthma exacerbations are associated with injury-repair responses in the airways that collectively contribute to airway remodeling. The physiological consequences of airway remodeling can manifest as irreversible airway obstruction and diminished responsiveness to bronchodilators. Structural cells of the airway, including epithelial cells, smooth muscle, fibroblasts, myofibroblasts, and adjacent lung vascular endothelial cells represent an understudied and emerging source of cellular and extracellular soluble mediators and matrix components that contribute to airway remodeling in a rhinovirus-evoked inflammatory environment.

MAIN BODY

While mechanistic pathways associated with rhinovirus-induced airway remodeling are still not fully characterized, infected airway epithelial cells robustly produce type 2 cytokines and chemokines, as well as pro-angiogenic and fibroblast activating factors that act in a paracrine manner on neighboring airway cells to stimulate remodeling responses. Morphological transformation of structural cells in response to rhinovirus promotes remodeling phenotypes including induction of mucus hypersecretion, epithelial-to-mesenchymal transition, and fibroblast-to-myofibroblast transdifferentiation. Rhinovirus exposure elicits airway hyperresponsiveness contributing to irreversible airway obstruction. This obstruction can occur as a consequence of sub-epithelial thickening mediated by smooth muscle migration and myofibroblast activity, or through independent mechanisms mediated by modulation of the β2 agonist receptor activation and its responsiveness to bronchodilators. Differential cellular responses emerge in response to rhinovirus infection that predispose asthmatic individuals to persistent signatures of airway remodeling, including exaggerated type 2 inflammation, enhanced extracellular matrix deposition, and robust production of pro-angiogenic mediators.

CONCLUSIONS

Few therapies address symptoms of rhinovirus-induced airway remodeling, though understanding the contribution of structural cells to these processes may elucidate future translational targets to alleviate symptoms of rhinovirus-induced exacerbations.

Advances in the Relationship between Respiratory Viruses and Asthma

Several studies have reported that viral infection is closely associated with the onset, progression, and exacerbation of asthma. The purpose of this review is to summarize the role that viral infections have in the pathogenesis of asthma onset and exacerbations, as well as discuss interrelated protective and risk factors of asthma and current treatment options. Furthermore, we present current knowledge of the innate immunological pathways driving host defense, including changes in the epithelial barrier. In addition, we highlight the importance of the genetics and epigenetics of asthma and virus susceptibility. Moreover, the involvement of virus etiology from bronchiolitis and childhood wheezing to asthma is described. The characterization and mechanisms of action of the respiratory viruses most frequently related to asthma are mentioned.

Thymic Stromal Lymphopoietin (TSLP), Its Isoforms and the Interplay with the Epithelium in Allergy and Asthma

Thymic stromal lymphopoietin (TSLP) is a pleiotropic cytokine that has emerged as a critical player in the development and progression of allergy and asthma. It is primarily produced by epithelial cells and functions as a potent immune system activator. TSLP acts through interaction with its receptor complex, composed of the TSLP receptor (TSLPR) and interleukin-7 receptor alpha chain (IL-7Rα), activating downstream complex signalling pathways. The TSLP major isoform, known as long-form TSLP (lfTSLP), is upregulated in the airway epithelium of patients with allergic diseases. More research is warranted to explore the precise mechanisms by which short-form TSLP (sfTSLP) regulates immune responses. Understanding the dynamic interplay between TSLP and the dysfunctional epithelium provides insights into the mechanisms underlying allergy and asthma pathogenesis. Targeting TSLP represents an important therapeutic strategy, as it may upstream disrupt the inflammatory cascade and alleviate symptoms associated with allergic inflammation.

Ιnterleukin-17A-Enriched Neutrophil Extracellular Traps Promote Immunofibrotic Aspects of Childhood Asthma Exacerbation

Childhood asthma is a chronic inflammatory airway disorder that can drive tissue remodeling. Neutrophils are amongst the most prominent inflammatory cells contributing to disease manifestations and may exert a potent role in the progression of inflammation to fibrosis. However, their role in asthma exacerbation is still understudied. Here, we investigate the association between neutrophil extracellular traps (NETs) and lung fibroblasts in childhood asthma pathophysiology using serum samples from pediatric patients during asthma exacerbation. Cell-based assays and NETs/human fetal lung fibroblast co-cultures were deployed. Increased levels of NETs and interleukin (IL)-17A were detected in the sera of children during asthma exacerbation. The in vitro stimulation of control neutrophils using the sera from pediatric patients during asthma exacerbation resulted in IL-17A-enriched NET formation. The subsequent co-incubation of lung fibroblasts with in vitro-generated IL-17A-enriched NETs led fibroblasts to acquire a pre-fibrotic phenotype, as assessed via enhanced CCN2 expression, migratory/healing capacity, and collagen release. These data uncover the important pathogenic role of the NET/IL-17A axis in asthma exacerbation, linking lung inflammation to fibroblast dysfunction and fibrosis.

Eosinophils as potential biomarkers in respiratory viral infections

Eosinophils are bone marrow-derived granulocytes that, under homeostatic conditions, account for as much as 1-3% of peripheral blood leukocytes. During inflammation, eosinophils can rapidly expand and infiltrate inflamed tissues, guided by cytokines and alarmins (such as IL-33), adhesion molecules and chemokines. Eosinophils play a prominent role in allergic asthma and parasitic infections. Nonetheless, they participate in the immune response against respiratory viruses such as respiratory syncytial virus and influenza. Notably, respiratory viruses are associated with asthma exacerbation. Eosinophils release several molecules endowed with antiviral activity, including cationic proteins, RNases and reactive oxygen and nitrogen species. On the other hand, eosinophils release several cytokines involved in homeostasis maintenance and Th2-related inflammation. In the context of SARS-CoV-2 infection, emerging evidence indicates that eosinophils can represent possible blood-based biomarkers for diagnosis, prognosis, and severity prediction of disease. In particular, eosinopenia seems to be an indicator of severity among patients with COVID-19, whereas an increased eosinophil count is associated with a better prognosis, including a lower incidence of complications and mortality. In the present review, we provide an overview of the role and plasticity of eosinophils focusing on various respiratory viral infections and in the context of viral and allergic disease comorbidities. We will discuss the potential utility of eosinophils as prognostic/predictive immune biomarkers in emerging respiratory viral diseases, particularly COVID-19. Finally, we will revisit some of the relevant methods and tools that have contributed to the advances in the dissection of various eosinophil subsets in different pathological settings for future biomarker definition.

Update on virus-induced asthma exacerbations

INTRODUCTION

Viral infections are common triggers for asthma exacerbation. Subjects with asthma are more susceptible to viral infections and develop more severe or long-lasting lower respiratory tract symptoms than healthy individuals owing to impaired immune responses. Of the many viruses associated with asthma exacerbation, rhinovirus (RV) is the most frequently identified virus in both adults and children.

AREAS COVERED

We reviewed epidemiological and clinical links and mechanistic studies on virus-associated asthma exacerbations. We included sections on severe acute respiratory syndrome coronavirus 2 (SARS-CoV2), the latest evidence of coronavirus disease 2019 (COVID-19) in asthma patients, and past and future searches for therapeutic and prevention targets.

EXPERT OPINION

Early treatment or prevention of viral infections might significantly reduce the rate of asthma exacerbation, which is one of the key points of disease management. Although it is hypothetically possible nowadays to interfere with every step of the infectious cycle of respiratory tract viruses, vaccination development has provided some of the most encouraging results. Future research should proceed toward the development of a wider spectrum of vaccines to achieve a better quality of life for patients with asthma and to reduce the economic burden on the healthcare system.

Heparin, Low Molecular Weight Heparin, and Non-Anticoagulant Derivatives for the Treatment of Inflammatory Lung Disease

Unfractionated heparin has multiple pharmacological activities beyond anticoagulation. These anti-inflammatory, anti-microbial, and mucoactive activities are shared in part by low molecular weight and non-anticoagulant heparin derivatives. Anti-inflammatory activities include inhibition of chemokine activity and cytokine synthesis, inhibitory effects on the mechanisms of adhesion and diapedesis involved in neutrophil recruitment, inhibition of heparanase activity, inhibition of the proteases of the coagulation and complement cascades, inhibition of neutrophil elastase activity, neutralisation of toxic basic histones, and inhibition of HMGB1 activity. This review considers the potential for heparin and its derivatives to treat inflammatory lung disease, including COVID-19, ALI, ARDS, cystic fibrosis, asthma, and COPD via the inhaled route.

Progress in diagnosis and treatment of difficult-to-treat asthma in children

At present, medications containing inhaled corticosteroids (ICS-containing) are the keystones of asthma treatment. The majority of asthmatic children can significantly improve clinical outcomes with little worsening by standardized inhaled glucocorticoid treatment, but there is still a small proportion of children who are unable to achieve good symptom control even after the maximum standardized treatment, known as 'children with difficult-to-treat asthma (DA)'. The high heterogeneity of DA makes therapy challenging and expensive, which poses a serious risk to children's health and makes it extremely difficult for clinical physicians to accurately identify and treat children with DA. This article reviews the definition, evaluation, and treatment of this asthma in order to provide a reference for optimal clinical decision-making.

Airway smooth muscle in contractility and remodeling of asthma: potential drug target mechanisms

INTRODUCTION

Asthma is characterized by enhanced airway contractility and remodeling where airway smooth muscle (ASM) plays a key role, modulated by inflammation. Understanding the mechanisms by which ASM contributes to these features of asthma is essential for the development of novel asthma therapies.

AREAS COVERED

Inflammation in asthma contributes to a multitude of changes within ASM including enhanced airway contractility, proliferation, and fibrosis. Altered intracellular calcium ([Ca²⁺]_i) regulation or Ca²⁺ sensitization contributes to airway hyperreactivity. Increased airway wall thickness from ASM proliferation and fibrosis contributes to structural changes seen with asthma.

EXPERT OPINION

ASM plays a significant role in multiple features of asthma. Increased ASM contractility contributes to hyperresponsiveness, while altered ASM proliferation and extracellular matrix production promote airway remodeling both influenced by inflammation of asthma and conversely even influencing the local inflammatory milieu. While standard therapies such as corticosteroids or biologics target inflammation, cytokines, or their receptors to alleviate asthma symptoms, these approaches do not address the underlying contribution of ASM to hyperresponsiveness and particularly remodeling. Therefore, novel therapies for asthma need to target abnormal contractility mechanisms in ASM and/or the contribution of ASM to remodeling, particularly in asthmatics resistant to current therapies.

Biomimetic lung-on-a-chip to model virus infection and drug evaluation

Viral infectious diseases remain a global public health problem. The rapid and widespread spread of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV‑2) has had a severe impact on the global economy and human activities, highlighting the vulnerability of humans to viral infectious diseases and the urgent need to develop new technologies and effective treatments. Organ-on-a-chip is an emerging technology for constructing the physiological and pathological microenvironment of human organs in vitro and has the advantages of portability, high throughput, low cost, and accurate simulation of the in vivo microenvironment. Indeed, organ-on-a-chip provides a low-cost alternative for investigating human organ physiology, organ diseases, toxicology, and drug efficacy. The lung is a main target organ of viral infection, and lung pathophysiology must be assessed after viral infection and treatment with antiviral drugs. This review introduces the construction of lung-on-a-chip and its related pathophysiological models, focusing on the in vitro simulation of viral infection and evaluation of antiviral drugs, providing a developmental direction for research and treatment of viral diseases.

"Liquid biopsy" - extracellular vesicles as potential novel players towards precision medicine in asthma

Extracellular vesicles (EVs) have emerged as vital mediators in intracellular communication in the lung microenvironment. Environmental exposure to various triggers (e.g., viruses, allergens) stimulates the EV-mediated cascade of pro-inflammatory responses that play a key role in the asthma pathomechanism. This complex EV-mediated crosstalk in the asthmatic lung microenvironment occurs between different cell types, including airway epithelial cells and immune cells. The cargo composition of EVs mirrors hereby the type and activation status of the parent cell. Therefore, EVs collected in a noninvasive way (e.g., in nasal lavage, serum) could inform on the disease status as a "liquid biopsy", which is particularly important in the pediatric population. As a heterogeneous disease, asthma with its distinct endotypes and phenotypes requires more investigation to develop novel diagnostics and personalized case management. Filling these knowledge gaps may be facilitated by further EV research. Here, we summarize the contribution of EVs in the lung microenvironment as potential novel players towards precision medicine in the development of asthma. Although rapidly evolving, the EV field is still in its infancy. However, it is expected that a better understanding of the role of EVs in the asthma pathomechanism will open up new horizons for precision medicine diagnostic and therapeutic solutions.

The potential roles of interleukin-25 in infectious diseases

Interleukin-25 (IL-25), also known as IL-17E, is a recently identified cytokine of the IL-17 family. Numerous studies illustrated that the expression of IL-25 is regulated by multiple pathogens, including parasitic, viral, and bacterial infections. IL-25 has a dual function in infectious diseases. On the one hand, IL-25 activates type 2 immunity via the relevant cytokines, including IL-4, IL-5, and IL-13, which are associated with the development of pathogenic infection-related allergic diseases. On the other hand, IL-25 involves in the recruitment of group 2 innate lymphoid cells (ILC2) to enhanced T helper 2 (Th2) cell differentiation, which are important to the clearance of pathogens. However, the precise roles of IL-25 in infectious diseases remain largely unknown. Thus, the current review will shed light on the pivotal roles of IL-25 in infectious diseases.