Cadherin-related family member 3, a childhood asthma susceptibility gene product, mediates rhinovirus C binding and replication

Upper Airway Gene Expression in Hospitalized Children with Rhinovirus-induced Respiratory Illnesses

Background

The precise mechanisms underlying rhinovirus (RV)-induced respiratory illnesses are not completely known.

Objective

We sought to obtain nasal transcriptomic data from hospitalized children with respiratory viral infections.

Methods

We obtained nasal swabs from 46 children with RV (16 RV-A, 30 RV-C). For comparison, we examined swabs from 12 children with RSV and six controls. Subjects ranged in age from 1 month to 18 years. Viral detection, genotyping and copy number were determined by PCR. RNA transcripts were measured by next generation sequencing and differences in gene expression calculated using DESeq2.

Results

Compared to controls, 1232 transcripts were upregulated (adjusted p<0.05, fold change >1.5) by all three viruses, including genes regulating granulocyte chemotaxis, cysteinyl leukotriene production, epithelial remodeling and antiviral responses. Cilium-related genes were downregulated. Compared to RSV, RV induced greater expression of 207 genes including those regulating eosinophilic inflammation, mucus secretion and mast cell function.RSV induced greater upregulation of 674 genes including those regulating neutrophilic inflammation and type 1 IFN response. Computational deconvolution of RNA-seq profiles revealed that viral infection decreased ciliated cells while increasing neutrophils, natural killer cells, monocytes (all viral species) and goblet cells (RV only). RV-C infections increased mast cells and IFN-λ mRNA expression. RV copy number correlated with the expression of mast cell proteases and numerous pro-inflammatory and IFN-stimulated genes.

Conclusion

Children hospitalized with RV and RSV infections mount robust inflammatory responses, but virus-specific differences exist.

Clinical Implication

These data provide insight into mechanisms by which RV, and in particular, RV-C, trigger respiratory illnesses.

Capsule summary

Nasal transcriptomics demonstrate that RV infections in hospitalized children induce expression of genes regulating eosinophilic inflammation, mucus secretion and mast cell function, with RV-C in particular increasing IFN-λ expression.

Hidden in plain sight: the impact of human rhinovirus infection in adults

BACKGROUND

Human rhinovirus (HRV), a non-enveloped RNA virus, was first identified more than 70 years ago. It is highly infectious and easily transmitted through aerosols and direct contact. The advent of multiplex PCR has enhanced the detection of a diverse range of respiratory viruses, and HRV consistently ranks among the most prevalent respiratory pathogens globally. Circulation occurs throughout the year, with peak incidence in autumn and spring in temperate climates. Remarkably, during the SARS-CoV-2 pandemic, HRV transmission persisted, demonstrating its resistance to stringent public health measures aimed at curbing viral transmission.

MAIN BODY

HRV is characterised by its extensive genetic diversity, comprising three species and more than 170 genotypes. This diversity and substantial number of concurrently circulating strains allows HRVs to frequently escape the adaptive immune system and poses formidable challenges for the development of effective vaccines and antiviral therapies. There is currently a lack of specific treatments. Historically, HRV has been associated with self-limiting upper respiratory infection. However, there is now extensive evidence highlighting its significant role in severe lower respiratory disease in adults, including exacerbations of chronic airway diseases, such as asthma and chronic obstructive pulmonary disease (COPD), as well as pneumonia. These severe manifestations can occur even in immunocompetent individuals, broadening the clinical impact of this ubiquitous virus. Consequently, the burden of rhinovirus infections extends across various healthcare settings, from primary care to general hospital wards and intensive care units. The impact of HRV in adults, in terms of morbidity and healthcare utilisation, rivals that of the other major respiratory viruses, including influenza and respiratory syncytial virus. Recognition of this substantial burden underscores the critical need for novel treatment strategies and effective management protocols to mitigate the impact of HRV infections on public health.

CONCLUSION

This review examines the epidemiology, clinical manifestations, and risk factors associated with severe HRV infection in adults. By drawing on contemporary literature, we aim to provide a comprehensive overview of the virus's significant health implications. Understanding the scope of this impact is essential for developing new, targeted interventions and improving patient outcomes in the face of this persistent and adaptable pathogen.

Respiratory Symptoms and Health Outcomes of Rhinovirus and Influenza Virus Infections: Implications of Asthma, Diabetes Mellitus and Allergic Rhinitis in Rhinovirus C Infection

Rhinovirus (RV), classified into RV-A, RV-B, and RV-C, is a prevalent cause of respiratory tract infections (RTIs). Here, we analysed RV infection and its clinical implications among outpatients with acute upper RTIs. Demographic data, baseline comorbidities, clinical symptoms, and health outcomes of RV-infected patients (n = 849) were compared with influenza (n = 417). Multivariable logistic regression was employed to evaluate predictors and health outcomes over a 1-year follow-up period. RV infections predominantly presented with cough, nasal discharge, and sore throat, whereas fever was more prevalent in influenza cases. RV-C-infected individuals with diabetes mellitus (adjusted odds ratio [aOR] 3.6; 95% CI 1.7-7.2; p = 0.001) and asthma (aOR 1.9; 95% CI 1.0-3.5; p = 0.047) showed a higher likelihood of experiencing severe acute respiratory symptoms. RV-C patients with comorbidities were twice more likely to have primary care visits due to RTIs within 1 year (aOR 2.4; 95% CI 1.4-4.4; p = 0.003). Asthma (aOR 3.8; 95% CI 1.9-7.2; p < 0.0001) and allergic rhinitis (aOR 2.9; 95% CI 1.0-8.0; p = 0.042) were key predictors of increased RTI-related primary care visits. RV infection, particularly in individuals with asthma, allergic rhinitis and diabetes, poses a significant disease burden similar to that of influenza.

Transgenic mice expressing the human CDHR3 receptor: A sensitive RV-C infection model for the evaluation of vaccines and therapeutics

Rhinovirus C (RV-C) is the primary causative agent of severe acute respiratory illnesses (ARTIs) in infants and young children. The limited availability of animal models complicates the development of prophylactic and therapeutic strategies targeting RV-C. Previous studies have identified human cadherin-related family member 3 (hCDHR3) as the cellular receptor for RV-C, with its expression enabling previously unsusceptible cells to support both viral entry and replication. Recently, an adult hCDHR3 transgenic mouse model was developed to investigate the role of human stimulator of interferon genes (hSTING) in RV-C15 infection in vivo. However, adult mice do not support efficient RV-C15 infection. Here, we report a transgenic mouse line expressing hCDHR3 constitutively that is highly susceptible to early-life infections by multiple serotypes of RV-C, including RV-C15, RV-C2, and RV-C41. Neonatal transgenic mice infected with various RV-C strains via the intraperitoneal (i.p.) route exhibit similar symptoms, such as severe inflammation, limb paralysis, and death. Moreover, passive immunization with antisera or therapeutic antibodies can protect against lethal RV-C infection in these transgenic mice. Overall, this study provides a valuable animal model for the in vivo antiviral evaluation against RV-C.

Association between cadherin-related family member 3 rs6967330-A and human rhinovirus-C induced wheezing in children

BACKGROUND

The heterogeneity of childhood wheezing illnesses is associated with viral and host factors. Human rhinoviruses (HRV) are the major pathogens in severe wheezing in young children. The single nucleotide polymorphism (SNP) rs6967330 G > A proved to heighten the risk of wheezing. However, the relation between rs6967330 variants of cadherin-related family member 3 (CDHR3) and wheezing induced by human rhinovirus (HRV)-C has not been determined.

METHODS

A total of 11,756 respiratory specimens collected from hospitalized children with acute respiratory infections (ARIs) between September 2017 and March 2023 were screened for enterovirus (EV)/HRVs by the capillary electrophoresis-based multiplex PCR (CEMP) assay, and those positive only for HRVs were amplified and sequenced for HRV and CDHR3 genotyping. The clinical data of the enrolled patients were obtained and analyzed.

RESULTS

EV/HRVs (15.2%; 1,616/10,608) were the more common viruses detected in inpatients with ARIs. Among the enrolled samples, 148 were positive for HRV-A (49.83%; 148/297), 129 for HRV-C (43.4%; 129/297), and 20 for HRV-B (6.7%; 20/297). More patients infected with HRV-C had history of allergy (P = 0.004), family history of asthma (P = 0.001), wheezing (P = 0.005) and asthma (P = 0.001) than those infected with HRV-A or HRV-B, while patients infected with HRV-C were less likely to have older siblings compared to those infected with HRV-A (P = 0.014). The rs6967330-A variant was related to a high incidence of the three concave signs (P = 0.047), asthma exacerbation (P = 0.025), a higher risk of HRV-C infection determined by the dominant model (OR 1.91, 95% confidence interval 1.05-3.48; P = 0.033), and a high proportion of wheezing (56.67%) in patients infected with HRV-C.

CONCLUSIONS

HRV-C is the dominant species responsible for HRV-induced wheezing. The rs6967330-A variant is a risk factor for HRV-C infection, and was associated with the high rate of wheezing induced by HRV-C.

The rs6967330 minor allele in CDHR3 is a significant risk factor for severe acute exacerbations in chronic rhinosinusitis

BACKGROUND

Acute exacerbations of chronic rhinosinusitis (AECRS) are commonly triggered by rhinovirus (RV) infections with secondary bacterial infections. Risk factors for AECRS are not well understood.

OBJECTIVE

We sought to determine whether carriers of the minor allele rs6967330 (AA/AG) in the cadherin-related family member 3 (CDHR3) gene have an increased risk for RV infections in AECRS in vivo and identify CDHR3 genotype-dependent host responses to RV infection in differentiated nasal airway-liquid interface (ALI) cultures ex vivo.

METHODS

We performed a prospective year-long study of adult subjects with chronic rhinosinusitis by the rs6967330 genotype (AA/AG, n = 16; GG, n = 38). We contacted subjects every 2 weeks, and if they reported AECRS, then clinical data were collected. ALI cultures of adults with chronic rhinosinusitis (AG/AA, n = 19; GG, n = 19) were challenged with RV-A and RV-C. We measured viral copy numbers at 4 and 48 hours postinfection and RNA transcriptomes and cytokines at 48 hours postinfection.

RESULTS

Subjects with the minor allele had significantly higher rates of RV and bacterial infections than those with the major allele. ALI minor allele cultures had higher viral copy numbers of RV-A and RV-C after 48 hours compared with the major allele. Differentially expressed genes and pathways identified an upregulation of IL-10 and IL-4/IL-13 pathways and a significant downregulation of Toll-like receptor pathways in the minor allele cultures after RV-A and RV-C infection. Unsupervised hierarchical analysis of all differentially expressed genes suggested that allergic rhinitis had an additive effect on this response.

CONCLUSIONS

The rs6967330 minor allele is associated with increased RV-A and RV-C replication, downregulation of Toll-like receptor-mediated responses, and increased type-2 and cytokine and chemokine responses during RV infection.

Profiling epithelial viral receptor expression in amniotic membrane and nasal epithelial cells at birth

INTRODUCTION

Children with wheeze and asthma present with airway epithelial vulnerabilities, such as impaired responses to viral infection. It is postulated that the in utero environment may contribute to the development of airway epithelial vulnerabilities. The aims of the study were to establish whether the receptors for rhinovirus (RV), respiratory syncytial virus (RSV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are expressed in the amniotic membrane and whether the pattern of expression is similar to newborn nasal epithelium.

METHODS

Placenta were collected (n = 33) from newborns in AERIAL, a sub-study nested under the ORIGINS birth cohort. Using purified RNA from amniotic samples (n = 33), along with previously extracted RNA from nasal epithelial cells from newborns (n = 20), real-time quantitative polymerase chain reaction (qPCR) was performed to determine gene expression of viral receptors for RV, RSV and SARS-CoV-2 in both amniotic and newborn nasal epithelial samples. In addition, receptor protein expression was quantified through Western blot and localised using immunohistochemical staining in amniotic samples.

RESULTS

Amniotic and newborn nasal samples expressed various receptors for RV (ICAM-1, LDLR, CDHR3), RSV (NCL, CX3CR1) and SARS-CoV-2 (ACE2, TMPRSS2) at the gene level, although the magnitude of expression varied. In addition, protein expression of these receptors was confirmed in the amniotic samples. These proteins were localised to the epithelial layer of the amniotic membrane.

CONCLUSION

This proof-of-concept study indicates the potential of amniotic samples to facilitate investigation into the interactions between the in utero environment and prenatal programming of epithelial innate immune responses to viruses.

In Vitro Model to Test Therapeutic Agents Against Rhinovirus Infection

To develop an antiviral drug, it is extremely important to have a relevant cell culture model system. The airway epithelial cells lining the conductive airways are the primary target for all three classes of rhinoviruses. However, rhinovirus replication is not very robust in airway epithelial cells; therefore, it does not cause cytopathic effects. However, rhinovirus induces replication-dependent cytokines such as type I and type III interferons and CXCL-10, which can be used as surrogates for viral load. Here, we describe a method using the immortalized normal human bronchial epithelial cell line, BEAS-2B cells. These cells readily grow in serum-free medium and can be infected with rhinovirus A and B. The binding, endocytosis, and replication of the virus induce CXCL-8 in these cells. These cells also respond to replicating virus by showing robust CXCL-10 production. Both CXCL-8 and CXCL-10 secreted into the medium can be readily measured by ELISA. Therefore, this method can be used to examine the drugs that can inhibit binding, endocytosis, and replication of the virus.

Investigation of Differentiated Nasal Epithelial Responses to Infection with Clinical Isolates of Rhinovirus A and C

The nasal epithelium is the primary point of contact for inhaled respiratory viruses such as rhinovirus, respiratory syncytial virus, influenza, and coronavirus, among others. In order to establish infection, these viruses must engage their respective receptors located on host epithelial cells and begin replication. However, the nasal epithelium is also a pivotal orchestrator of both structural and innate immune defenses against these pathogens and thus mounts a broad antiviral response to halt the progression of the infection into the lower airways. Of note, the most common virus found in the airways of children presenting to the hospital emergency department with acute wheezing and asthma is rhinovirus C (RV-C), followed by rhinovirus A (RV-A). Here, we illustrate infection of a preclinical differentiated nasal epithelial model with clinical isolates of RV-A and -C, in conjunction with several methods utilized for characterization of epithelial responses post-infection in vitro.

Quantification of Infectious Rhinovirus A and B Serotypes by Plaque Assay

Plaque assay is a quantitative assay that determines the number of infective virions in the viral stock or the infected cells. Plaques are essentially virus-infected cells that produce progeny virus and infect adjacent cells. The cells producing progeny virus die and detach from the dish, leaving an empty space in the confluent monolayer of cells. Unlike other viruses, rhinovirus does not form characteristic round plaques but shows small clear areas of different shapes surrounded by dying cells. Rhinoviruses form plaques only in highly susceptible H1HeLa cells but not in their primary target, airway epithelial cells. The plaque assay to determine the number of infective virions works only for rhinovirus species A and B, but not C, because the latter does not infect H1HeLa cells. Here we describe a method to quantify the infective virions by plaque assay for rhinovirus speciesA and B.

Laboratory Protocol for Propagation and Purification of Rhinovirus A and B Suitable for In Vitro and In Vivo Infection

H1HeLa cell line has become the most utilized cell culture system for in vitro studies of the rhinovirus life cycle. These cells are also widely used to propagate the rhinovirus to study host responses. Unlike other viruses, high-titer virus is required for studies focusing on understanding the host responses to rhinovirus infection in vivo and in vitro. Therefore, after propagation of rhinovirus, H1HeLa cells should be concentrated and purified. In this chapter, we describe the methods used for the propagation of rhinovirus A and B that are adapted to H1HeLa cells.

Determination of Binding and Endocytosis of Rhinovirus by Flow Cytometry

Viruses are dependent on their host cells for replication. The first step in viral infection is the binding of the virus to the host cell membrane, followed by internalization or endocytosis of the virus. Rhinoviruses utilize several cellular membrane receptors to cross the plasma membrane by endocytosis. Three major glycoprotein receptors that are utilized by rhinoviruses to gain entry into the cells are intracellular adhesion molecules, low-density lipoprotein receptor family members, and cadherin-related family member-3. Rhinovirus is endocytosed by a clathrin- or dynamin-dependent mechanism. Upon uptake into an acidic endosomal environment, rhinovirus uncoats and injects its genome into the cytoplasm, where the viral replication begins. It is often difficult to differentiate between bound and the endocytosed rhinovirus in the cells. Here, we describe a method to quantify bound and endocytosed virus by flow cytometry.

Interplay between respiratory viruses and cilia in the airways

The airway epithelium is the first point of contact for inhaled pathogens. The role of epithelial cells in clearance, infection and colonisation of bacteria is established. The interactions of respiratory viruses and cilia is less understood, but viruses are known to target ciliated epithelial cells for entry, replication and dissemination. Furthermore, some respiratory viruses impair and/or enhance ciliary activity. This review examines what is known about the interactions between cilia and viral infection and how respiratory viruses effect cilia function with subsequent consequences for human health. We discuss the models which can be used to investigate the relationship between respiratory viruses and the host airway.

Interactions between epithelial mesenchymal plasticity, barrier dysfunction and innate immune pathways shape the genesis of allergic airway disease

INTRODUCTION

In genetically predisposed individuals, exposure to aeroallergens and infections from RNA viruses shape epithelial barrier function, leading to Allergic Asthma (AA). Here, activated pattern recognition receptors (PRRs) in lower airway sentinel cells signal epithelial injury-repair pathways leading to cell-state changes [epithelial mesenchymal plasticity (EMP)], barrier disruption and sensitization.

AREAS COVERED

1. Characteristics of sentinel epithelial cells of the bronchoalveolar junction, 2. The effect of aeroallergens on epithelial PRRs, 3. Role of tight junctions (TJs) in barrier function and how aeroallergens disrupt their function, 4. Induction of mucosal TGF autocrine loops activating type-2 innate lymphoid cells (ICL2s) leading to Th2 polarization, 5. How respiratory syncytial virus (RSV) directs goblet cell hyperplasia, and 6. Coupling of endoplasmic reticulum (ER) stress to metabolic adaptations and effects on basal lamina remodeling.

EXPERT OPINION

When aeroallergens or viral infections activate innate immunity in sentinel cells of the bronchoalveolar junction, normal barrier function is disrupted, promoting chronic inflammation and Th2 responses. An improved mechanistic understanding of how activated PRRs induce EMP couples with TJ disruption, metabolic reprogramming and ECM deposition provides new biologically validated targets to restore barrier function, reduce sensitization, and remodeling in AA.

Method to Generate High-Titer Rhinovirus C Suitable for In Vitro and In Vivo Studies

Rhinovirus (RV)-C, discovered in 2006, binds to human cadherin-related family member 3 expressed on ciliated cells. RV-C is the cause of severe respiratory illness in children with asthma. Unlike rhinovirus-A and B, very little is known about the RV-C biology or pathogenic mechanisms. This is because RV-C cannot be propagated using the conventional method that is described for RV-A and RV-B in Chapter 2 . H1HeLa cells or primary lung fibroblasts do not express the receptor for RV-C and, therefore, they are resistant to RV-C infection. Recently, human mucociliary-differentiated immortalized airway epithelial cells expressing cadherin-related family member 3 cells were shown to be suitable for propagating RV-C from clinical samples, but this method may not be sustainable due to the costs of culturing the cells for large-scale virus production. Another method to propagate the virus is to transfect the viral genome into H1HeLa or primary lung fibroblasts to bypass the initial infection step, which is the binding and endocytosis of the virus. RV-C virus propagated by this method was demonstrated to yield relatively high-titer infectious virus suitable for in vitro studies. Here, we describe a method to propagate and purify the RV-C suitable for in vitro and in vivo studies.

Human respiratory organoids sustained reproducible propagation of human rhinovirus C and elucidation of virus-host interaction

The lack of a robust system to reproducibly propagate HRV-C, a family of viruses refractory to cultivation in standard cell lines, has substantially hindered our understanding of this common respiratory pathogen. We sought to develop an organoid-based system to reproducibly propagate HRV-C, and characterize virus-host interaction using respiratory organoids. We demonstrate that airway organoids sustain serial virus passage with the aid of CYT387-mediated immunosuppression, whereas nasal organoids that more closely simulate the upper airway achieve this without any intervention. Nasal organoids are more susceptible to HRV-C than airway organoids. Intriguingly, upon HRV-C infection, we observe an innate immune response that is stronger in airway organoids than in nasal organoids, which is reproduced in a Poly(I:C) stimulation assay. Treatment with α-CDHR3 and antivirals significantly reduces HRV-C viral growth in airway and nasal organoids. Additionally, an organoid-based immunofluorescence assay is established to titrate HRV-C infectious particles. Collectively, we develop an organoid-based system to reproducibly propagate the poorly cultivable HRV-C, followed by a comprehensive characterization of HRV-C infection and innate immunity in physiologically active respiratory organoids. The organoid-based HRV-C infection model can be extended for developing antiviral strategies. More importantly, our study has opened an avenue for propagating and studying other uncultivable human and animal viruses.

Meeting report of the 37th International Conference on Antiviral Research in Gold Coast, Australia, May 20-24, 2024, organized by the International Society for Antiviral Research

The 37th International Conference on Antiviral Research (ICAR) was held in Gold Coast, Australia, May 20-24, 2024. ICAR 2024 featured over 75 presentations along with two poster sessions and special events, including those specifically tailored for trainees and early-career scientists. The meeting served as a platform for the exchange of cutting-edge research, with presentations and discussions covering novel antiviral compounds, vaccine development, clinical trials, and therapeutic advancements. A comprehensive array of topics in antiviral science was covered, from the latest breakthroughs in antiviral drug development to innovative strategies for combating emerging viral threats. The keynote presentations provided fascinating insight into two diverse areas fundamental to medical countermeasure development and use, including virus emergence at the human-animal interface and practical considerations for bringing antivirals to the clinic. Additional sessions addressed a variety of timely post-pandemic topics, such as the hunt for broad spectrum antivirals, combination therapy, pandemic preparedness, application of in silico tools and AI in drug discovery, the virosphere, and more. Here, we summarize all the presentations and special sessions of ICAR 2024 and introduce the 38th ICAR, which will be held in Las Vegas, USA, March 17-21, 2025.

Cryo-EM of human rhinovirus reveals capsid-RNA duplex interactions that provide insights into virus assembly and genome uncoating

The cryo-EM structure of the human rhinovirus B14 determined in this study reveals 13-bp RNA duplexes symmetrically bound to regions around each of the 30 two-fold axes in the icosahedral viral capsid. The RNA duplexes (~12% of the ssRNA genome) define a quasi-dodecahedral cage that line a substantial part of the capsid interior surface. The RNA duplexes establish a complex network of non-covalent interactions with pockets in the capsid inner wall, including coulombic interactions with a cluster of basic amino acid residues that surround each RNA duplex. A direct comparison was made between the cryo-EM structure of RNA-filled virions and that of RNA-free (empty) capsids that resulted from genome release from a small fraction of viruses. The comparison reveals that some specific residues involved in capsid-duplex RNA interactions in the virion undergo remarkable conformational rearrangements upon RNA release from the capsid. RNA release is also associated with the asynchronous opening of channels at the 30 two-fold axes. The results provide further insights into the molecular mechanisms leading to assembly of rhinovirus particles and their genome uncoating during infection. They may also contribute to development of novel antiviral strategies aimed at interfering with viral capsid-genome interactions during the infectious cycle.

A review of virus host factor discovery using CRISPR screening

The emergence of genome-scale forward genetic screening techniques, such as Haploid Genetic screen and clustered regularly interspaced short palindromic repeats (CRISPR) knockout screen has opened new horizons in our understanding of virus infection biology. CRISPR screening has become a popular tool for the discovery of novel host factors for several viruses due to its specificity and efficiency in genome editing. Here, we review how CRISPR screening has revolutionized our understanding of virus-host interactions from scientific and technological viewpoints. A summary of the published screens conducted thus far to uncover virus host factors is presented, highlighting their experimental design and significant findings. We will outline relevant methods for customizing the CRISPR screening process to answer more specific hypotheses and compile a glossary of conducted CRISPR screens to show their design aspects. Furthermore, using flaviviruses and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as examples, we hope to offer a broad-based perspective on the capabilities of CRISPR screening to serve as a reference point to guide future unbiased discovery of virus host factors.

Surfactant Protein A Inhibits Human Rhinovirus C Binding and Infection of Airway Epithelial Cells from Pediatric Asthma

Rhinovirus C (RV-C) infection can trigger asthma exacerbations in children and adults, and RV-C-induced wheezing illnesses in preschool children correlate with the development of childhood asthma. Surfactant protein A (SP-A) plays a critical role in regulating pulmonary innate immunity by binding to numerous respiratory pathogens. Mature SP-A consists of multiple isoforms that form the hetero-oligomers of SP-A1 and SP-A2, organized in 18-mers. In this report, we examined the efficacy of SP-A to antagonize RV-C infection using the wild-type (RV-C15) and reporter-expressing (RV-C15-GFP) viruses in differentiated nasal epithelial cells (NECs) from asthmatic and non-asthmatic children. We also determined the antiviral mechanism of action of SP-A on RV-C15 infection. The native SP-A was purified from alveolar proteinosis patients. The recombinant (r) SP-A1 and SP-A2 variants were expressed in FreeStyle™ 293-F cells. SP-A reduced the fluorescent focus-forming units (FFUs) after RV-C15-GFP infection of NECs by 99%. Both simultaneous and 4 h post-infection treatment with SP-A inhibited RV-C15 and RV-C15-GFP viral RNA load by 97%. In addition, the antiviral genes and chemokines (IFN-λ, IRF-7, MDA-5, and CXLC11) were not induced in the infected NECs due to the inhibition of RV-C propagation by SP-A. Furthermore, SP-A bound strongly to RV-C15 in a dose- and Ca2+-dependent manner, and this interaction inhibited RV-C15 binding to NECs. In contrast, rSP-A1 did not bind to solid-phase RV-C15, whereas the rSP-A2 variants, [A91, K223] and [P91, Q223], had strong binding affinities to RV-C15, similar to native SP-A. This study demonstrates that SP-A might have potential as an antiviral for RV infection and RV-induced asthma exacerbations.

Rhinovirus infection of airway epithelial cells uncovers the non-ciliated subset as a likely driver of genetic risk to childhood-onset asthma

Asthma is a complex disease caused by genetic and environmental factors. Studies show that wheezing during rhinovirus infection correlates with childhood asthma development. Over 150 non-coding risk variants for asthma have been identified, many affecting gene regulation in T cells, but the effects of most risk variants remain unknown. We hypothesized that airway epithelial cells could also mediate genetic susceptibility to asthma given they are the first line of defense against respiratory viruses and allergens. We integrated genetic data with transcriptomics of airway epithelial cells subject to different stimuli. We demonstrate that rhinovirus infection significantly upregulates childhood-onset asthma-associated genes, particularly in non-ciliated cells. This enrichment is also observed with influenza infection but not with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or cytokine activation. Overall, our results suggest that rhinovirus infection is an environmental factor that interacts with genetic risk factors through non-ciliated airway epithelial cells to drive childhood-onset asthma.

Human Stimulator of Interferon Genes Promotes Rhinovirus C Replication in Mouse Cells In Vitro and In Vivo

Rhinovirus C (RV-C) infects airway epithelial cells and is an important cause of acute respiratory disease in humans. To interrogate the mechanisms of RV-C-mediated disease, animal models are essential. Towards this, RV-C infection was recently reported in wild-type (WT) mice, yet, titers were not sustained. Therefore, the requirements for RV-C infection in mice remain unclear. Notably, prior work has implicated human cadherin-related family member 3 (CDHR3) and stimulator of interferon genes (STING) as essential host factors for virus uptake and replication, respectively. Here, we report that even though human (h) and murine (m) CDHR3 orthologs have similar tissue distribution, amino acid sequence homology is limited. Further, while RV-C can replicate in mouse lung epithelial type 1 (LET1) cells and produce infectious virus, we observed a significant increase in the frequency and intensity of dsRNA-positive cells following hSTING expression. Based on these findings, we sought to assess the impact of hCDHR3 and hSTING on RV-C infection in mice in vivo. Thus, we developed hCDHR3 transgenic mice, and utilized adeno-associated virus (AAV) to deliver hSTING to the murine airways. Subsequent challenge of these mice with RV-C15 revealed significantly higher titers 24 h post-infection in mice expressing both hCDHR3 and hSTING-compared to either WT mice, or mice with hCDHR3 or hSTING alone, indicating more efficient infection. Ultimately, this mouse model can be further engineered to establish a robust in vivo model, recapitulating viral dynamics and disease.

Role of airway epithelium in viral respiratory infections: Can carbocysteine prevent or mitigate them?

Alterations in airway epithelial homeostasis increase viral respiratory infections risk. Viral infections frequently are associated with chronic obstructive pulmonary disease (COPD) exacerbations, events that dramatically promote disease progression. Mechanism promoting the main respiratory viruses entry and virus-evocated innate and adaptive immune responses have now been elucidated, and an oxidative stress central role in these pathogenic processes has been recognized. Presence of reactive oxygen species in macrophages and other cells allows them to eliminate virus, but its excess alters the balance between innate and adaptive immune responses and proteases/anti-proteases and leads to uncontrolled inflammation, tissue damage, and hypercoagulability. Different upper and lower airway cell types also play a role in viral entry and infection. Carbocysteine is a muco-active drug with anti-oxidant and anti-inflammatory properties used for the management of several chronic respiratory diseases. Although the use of anti-oxidants has been proposed as an effective strategy in COPD exacerbations management, the molecular mechanisms that explain carbocysteine efficacy have not yet been fully clarified. The present review describes the most relevant features of the common respiratory virus pathophysiology with a focus on epithelial cells and oxidative stress role and reports data supporting a putative role of carbocysteine in viral respiratory infections.

Circulation pattern and genetic variation of rhinovirus infection among hospitalized children on Hainan Island, before and after the dynamic zero-COVID policy, from 2021 to 2023

Throughout the COVID-19 pandemic, rhinovirus (RV) remained notable persistence, maintaining its presence while other seasonal respiratory viruses were largely suppressed by pandemic restrictions during national lockdowns. This research explores the epidemiological dynamics of RV infections among pediatric populations on Hainan Island, China, specifically focusing on the impact before and after the zero-COVID policy was lifted. From January 2021 to December 2023, 19 680 samples were collected from pediatric patients hospitalized with acute lower respiratory tract infections (ARTIs) at the Hainan Maternal and Child Health Hospital. The infection of RV was detected by tNGS. RV species and subtypes were identified in 32 RV-positive samples representing diverse time points by analyzing the VP4/VP2 partial regions. Among the 19 680 pediatric inpatients with ARTIs analyzed, 21.55% were found to be positive for RV infection, with notable peaks observed in April 2021 and November 2022. A gradual annual decline in RV infections was observed, alongside a seasonal pattern of higher prevalence during the colder months. The highest proportion of RV infections was observed in the 0-1-year age group. Phylogenetic analysis on 32 samples indicated a trend from RV-A to RV-C in 2022. This observation suggests potential evolving dynamics within the RV species although further studies are needed due to the limited sample size. The research emphasizes the necessity for ongoing surveillance and targeted management, particularly for populations highly susceptible to severe illnesses caused by RV infections.

Immunotherapeutic implications on targeting the cytokines produced in rhinovirus-induced immunoreactions

Rhinovirus is a widespread virus associated with several respiratory diseases, especially asthma exacerbation. Currently, there are no accurate therapies for rhinovirus. Encouragingly, it is found that during rhinovirus-induced immunoreactions the levels of certain cytokines in patients' serum will alter. These cytokines may have pivotal pro-inflammatory or anti-inflammatory effects via their specific mechanisms. Thus far, studies have shown that inhibitions of cytokines such as IL-1, IL-4, IL-5, IL-6, IL-13, IL-18, IL-25, and IL-33 may attenuate rhinovirus-induced immunoreactions, thereby relieving rhinovirus infection. Furthermore, such therapeutics for rhinovirus infection can be applied to viruses of other species, with certain practicability.

Mutations at the conserved N-Terminal of the human Rhinovirus capsid gene VP4, and their impact on the immune response

Rhinoviruses (RV) are the major cause of chronic obstructive pulmonary disease and are associated with exacerbation development as well as community-acquired pneumonia in children, leading to substantial morbidity, mortality, and hospital admission. Here we have examined how changes at the amino terminal of the conserved VP4 epitope of different RV serotypes may affect pulmonary cytokine and chemokine responses and disease severity. Samples positive for rhinovirus were used for genetic characterization, followed by profiling gene expression of pulmonary Th1 and Th2 cytokines/chemokines by RT-PCR arrays. Genetic sequencing and homology 3D modeling revealed changes at the amino terminal of the conserved viral protein 4 (VP4) epitope in the RV-A101 serotype, especially serine at several positions that are important for interactive binding with the host immune cells. We found dysregulation of pulmonary gene expression of Th1- and Th2-related cytokines and chemokines in RV-A 101 and RV-C 8 pneumonia patients. These findings might contribute to a better understanding of RV immunity and the potential mechanisms underlying the pathogenesis of severe RV infections, but further functional studies are needed to confirm the causal relationship.

Identification of common genes of rhinovirus single/double‑stranded RNA‑induced asthma deterioration by bioinformatics analysis

Rhinovirus (RV) is the most common respiratory virus affecting humans. The majority of asthma deteriorations are triggered by RV infections. However, whether the effects of RV single- and double-stranded RNA on asthma deterioration have common target genes needs to be further studied. In the present study, two datasets (GSE51392 and GSE30326) were used to screen for common differentially expressed genes (cDEGs). The molecular function, signaling pathways, interaction networks, hub genes, key modules and regulatory molecules of cDEGs were systematically analyzed using online tools such as Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, STRING and NetworkAnalyst. Finally, the hub genes STAT1 and IFIH1 were verified in clinical samples using reverse transcription-quantitative PCR (RT-qPCR). A total of 85 cDEGs were identified. Function analysis revealed that cDEGs served an important role in the innate immune response to viruses and its regulation. Signal transducer and activator of transcription 1 (STAT1), interferon induced with helicase C domain 1 (IFIH1), interferon regulatory factor 7 (IRF7), DExD/H box helicase 58 (DDX58) and interferon-stimulating gene 15 (ISG15) were detected to be hub genes based on the protein-protein interactions and six topological algorithms. A key module involved in influenza A, the Toll-like receptor signaling pathway, was identified using Cytoscape software. The hub genes were regulated by GATA-binding factor 2 and microRNA-146a-5p. In addition, RT-qPCR indicated that the expression levels of the hub genes STAT1 and IFIH1 were low during asthma deterioration compared with post-treatment recovery samples. The present study enhanced the understanding of the mechanism of RV-induced asthma deterioration.

Identification of epidermal growth factor receptor-tyrosine kinase inhibitor targeting the VP1 pocket of human rhinovirus

Screening a library of 1,200 preselected kinase inhibitors for anti-human rhinovirus 2 (HRV-2) activity in HeLa cells identified a class of epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKI) as effective virus blockers. These were based on the 4-anilinoquinazoline-7-oxypiperidine scaffold, with the most potent representative AZ5385 inhibiting the virus with EC50 of 0.35 µM. Several structurally related analogs confirmed activity in the low µM range, while interestingly, other TKIs targeting EGFR lacked anti-HRV-2 activity. To further probe this lack of association between antiviral activity and EGFR inhibition, we stained infected cells with antibodies specific for activated EGFR (Y1068) and did not observe a dependency on EGFR-TK activity. Instead, consecutive passages of HRV-2 in HeLa cells in the presence of a compound and subsequent nucleotide sequence analysis of resistant viral variants identified the S181T and T210A alterations in the major capsid VP1 protein, with both residues located in the vicinity of a known hydrophobic pocket on the viral capsid. Further characterization of the antiviral effects of AZ5385 showed a modest virus-inactivating (virucidal) activity, while anti-HRV-2 activity was still evident when the inhibitor was added as late as 10 h post infection. The RNA copy/infectivity ratio of HRV-2 propagated in AZ5385 presence was substantially higher than that of control HRV indicating that the compound preferentially targeted HRV progeny virions during their maturation in infected cells. Besides HRV, the compound showed anti-respiratory syncytial virus activity, which warrants its further studies as a candidate compound against viral respiratory infections.

Common Pathogeneses Underlying Asthma and Chronic Obstructive Pulmonary Disease -Insights from Genetic Studies

Neither asthma nor chronic obstructive pulmonary disease (COPD) is a single disease consisting of a uniform pathogenesis; rather, they are both syndromes that result from a variety of basic distinct pathogeneses. Many of the basic pathogeneses overlap between the two diseases, and multiple basic pathogeneses are simultaneously involved at varying proportions in individual patients. The specific combination of different basic pathogeneses in each patient determines the phenotype of the patient, and it varies widely from patient to patient. For example, type 2 airway inflammation and neutrophilic airway inflammation may coexist in the same patient, and quite a few patients have clinical characteristics of both asthma and COPD. Even in the same patient, the contribution of each pathogenesis is expected to differ at different life stages (eg, childhood, adolescence, middle age, and older), during different seasons (eg, high seasons for hay fever and rhinovirus infection), and depending on the nature of treatments. This review describes several basic pathogeneses commonly involved in both asthma and COPD, including chronic non-type 2 inflammation, type 2 inflammation, viral infections, and lung development. Understanding of the basic molecular pathogeneses in individual patients, rather than the use of clinical diagnosis, such as asthma, COPD, or even asthma COPD overlap, will enable us to better deal with the diversity seen in disease states, and lead to optimal treatment practices tailored for each patient with less disease burden, such as drug-induced side effects, and improved prognosis. Furthermore, we can expect to focus on these molecular pathways as new drug discovery targets.

Sphingosine Prevents Rhinoviral Infections

Rhinoviral infections cause approximately 50% of upper respiratory tract infections and novel treatment options are urgently required. We tested the effects of 10 μM to 20 μM sphingosine on the infection of cultured and freshly isolated human cells with minor and major group rhinovirus in vitro. We also performed in vivo studies on mice that were treated with an intranasal application of 10 μL of either a 10 μM or a 100 μM sphingosine prior and after infection with rhinovirus strains 1 and 2 and determined the infection of nasal epithelial cells in the presence or absence of sphingosine. Finally, we determined and characterized a direct binding of sphingosine to rhinovirus. Our data show that treating freshly isolated human nasal epithelial cells with sphingosine prevents infections with rhinovirus strains 2 (minor group) and 14 (major group). Nasal infection of mice with rhinovirus 1b and 2 is prevented by the intranasal application of sphingosine before or as long as 8 h after infection with rhinovirus. Nasal application of the same doses of sphingosine exerts no adverse effects on epithelial cells as determined by hemalaun and TUNEL stainings. The solvent, octylglucopyranoside, was without any effect in vitro and in vivo. Mechanistically, we demonstrate that the positively charged lipid sphingosine binds to negatively charged molecules in the virus, which seems to prevent the infection of epithelial cells. These findings indicate that exogenous sphingosine prevents infections with rhinoviruses, a finding that could be therapeutically exploited. In addition, we demonstrated that sphingosine has no obvious adverse effects on the nasal mucosa. Sphingosine prevents rhinoviral infections by a biophysical mode of action, suggesting that sphingosine could serve to prevent many viral infections of airways and epithelial cells in general. Future studies need to determine the molecular mechanisms of how sphingosine prevents rhinoviral infections and whether sphingosine also prevents infections with other viruses inducing respiratory tract infections. Furthermore, our studies do not provide detailed pharmacokinetics that are definitely required before the further development of sphingosine.

Rhinovirus infection of airway epithelial cells uncovers the non-ciliated subset as a likely driver of genetic susceptibility to childhood-onset asthma

Asthma is a complex disease caused by genetic and environmental factors. Epidemiological studies have shown that in children, wheezing during rhinovirus infection (a cause of the common cold) is associated with asthma development during childhood. This has led scientists to hypothesize there could be a causal relationship between rhinovirus infection and asthma or that RV-induced wheezing identifies individuals at increased risk for asthma development. However, not all children who wheeze when they have a cold develop asthma. Genome-wide association studies (GWAS) have identified hundreds of genetic variants contributing to asthma susceptibility, with the vast majority of likely causal variants being non-coding. Integrative analyses with transcriptomic and epigenomic datasets have indicated that T cells drive asthma risk, which has been supported by mouse studies. However, the datasets ascertained in these integrative analyses lack airway epithelial cells. Furthermore, large-scale transcriptomic T cell studies have not identified the regulatory effects of most non-coding risk variants in asthma GWAS, indicating there could be additional cell types harboring these "missing regulatory effects". Given that airway epithelial cells are the first line of defense against rhinovirus, we hypothesized they could be mediators of genetic susceptibility to asthma. Here we integrate GWAS data with transcriptomic datasets of airway epithelial cells subject to stimuli that could induce activation states relevant to asthma. We demonstrate that epithelial cultures infected with rhinovirus significantly upregulate childhood-onset asthma-associated genes. We show that this upregulation occurs specifically in non-ciliated epithelial cells. This enrichment for genes in asthma risk loci, or 'asthma heritability enrichment' is also significant for epithelial genes upregulated with influenza infection, but not with SARS-CoV-2 infection or cytokine activation. Additionally, cells from patients with asthma showed a stronger heritability enrichment compared to cells from healthy individuals. Overall, our results suggest that rhinovirus infection is an environmental factor that interacts with genetic risk factors through non-ciliated airway epithelial cells to drive childhood-onset asthma.

Uncovering Structural Plasticity of Enterovirus A through Deep Insertional and Deletional Scanning

Insertions and deletions (InDels) are essential sources of novelty in protein evolution. In RNA viruses, InDels cause dramatic phenotypic changes contributing to the emergence of viruses with altered immune profiles and host engagement. This work aimed to expand our current understanding of viral evolution and explore the mutational tolerance of RNA viruses to InDels, focusing on Enterovirus A71 (EV-A71) as a prototype for Enterovirus A species (EV-A). Using newly described deep InDel scanning approaches, we engineered approximately 45,000 insertions and 6,000 deletions at every site across the viral proteome, quantifying their effects on viral fitness. As a general trend, most InDels were lethal to the virus. However, our screen reproducibly identified a set of InDel-tolerant regions, demonstrating our ability to comprehensively map tolerance to these mutations. Tolerant sites highlighted structurally flexible and mutationally plastic regions of viral proteins that avoid core structural and functional elements. Phylogenetic analysis on EV-A species infecting diverse mammalian hosts revealed that the experimentally-identified hotspots overlapped with sites of InDels across the EV-A species, suggesting structural plasticity at these sites is an important function for InDels in EV speciation. Our work reveals the fitness effects of InDels across EV-A71, identifying regions of evolutionary capacity that require further monitoring, which could guide the development of Enterovirus vaccines.

Physiological and immunological barriers in the lung

The lungs serve as the primary organ for respiration, facilitating the vital exchange of gases with the bloodstream. Given their perpetual exposure to external particulates and pathogens, they possess intricate protective barriers. Cellular adhesion in the lungs is robustly maintained through tight junctions, adherens junctions, and desmosomes. Furthermore, the pulmonary system features a mucociliary clearance mechanism that synthesizes mucus and transports it to the outside. This mucus is enriched with chemical barriers like antimicrobial proteins and immunoglobulin A (IgA). Additionally, a complex immunological network comprising epithelial cells, neural cells, and immune cells plays a pivotal role in pulmonary defense. A comprehensive understanding of these protective systems offers valuable insights into potential pathologies and their therapeutic interventions.

Genetics of preschool wheeze and its progression to childhood asthma

Wheezing is a common and heterogeneous condition in preschool children. In some countries, the prevalence can be as high as 30% and up to 50% of all children experience wheezing before the age of 6. Asthma often starts with preschool wheeze, but not all wheezing children will develop asthma at school age. At this moment, it is not possible to accurately predict which wheezing children will develop asthma. Recently, studying the genetics of wheeze and the childhood-onset of asthma have grown in interest. Childhood-onset asthma has a stronger heritability in comparison with adult-onset asthma. In early childhood asthma exacerbations, CDHR3, which encodes the receptor for Rhinovirus C, was identified, as well as IL33, and the 17q locus that includes GSDMB and ORMDL3 genes. The 17q locus is the strongest wheeze and childhood-onset asthma locus, and was shown to interact with many environmental factors, including smoking and infections. Finally, ANXA1 was recently associated with early-onset, persistent wheeze. ANXA1 may help resolve eosinophilic inflammation. Overall, despite its complexities, genetic approaches to unravel the early-onset of wheeze and asthma are promising, since these shed more light on mechanisms of childhood asthma-onset. Implicated genes point toward airway epithelium and its response to external factors, such as viral infections. However, the heterogeneity of wheeze phenotypes complicates genetic studies. It is therefore important to define accurate wheezing phenotypes and forge larger international collaborations to gain a better understanding of the pathways underlying early-onset asthma.

Genetic diversity and characterization of rhinoviruses from Chinese clinical samples with a global perspective

IMPORTANCE

Based on clinical samples collected in China, we detected and reported 22 types for the first time in China, as well as three types for the first time in Asia, and reported their genetic characteristics and diversity. We identified a novel type of Rhinovirus (RV), A110, highlighting its unique genetic features. We annotated the genomic structure and serotype of all the existing RV sequences in the database, and four novel RV types were identified and their genetic diversity reported. Combined with the sequence annotation, we constructed a complete VP1 data set of RV and conducted the first large-scale evolutionary dynamics analysis of RV. Based on a high-quality data set, we conducted a comprehensive analysis of the guanine-cytosine (GC) content variations among serotypes of RVs. This study provides crucial theoretical support and valuable data for understanding RV's genetic diversity and developing antiviral strategies.

Effects of treatment with corticosteroids on human rhinovirus-induced asthma exacerbations in pediatric inpatients: a prospective observational study

BACKGROUND

Human rhinoviruses (HRVs) infection is a common cause of exacerbations in pediatric patients with asthma. However, the effects of corticosteroids on HRV-induced exacerbations in pediatric asthma are unknown. We conducted a prospective observational study to determine the viral pathogens in school-age pediatric inpatients with asthma exacerbations. We assessed the effects of maintenance inhaled corticosteroids (ICS) on the detection rates of HRV species and treatment periods of systemic corticosteroids during exacerbations on pulmonary lung function after exacerbations.

METHODS

Nasopharyngeal samples and clinical information were collected from 59 patients with asthma exacerbations between April 2018 and March 2020. Pulmonary function tests were carried out 3 months after exacerbations in 18 HRV-positive patients. Changes in forced expiratory volume in 1 second (FEV1)% predicted from baseline in a stable state were compared according to the treatment periods of systemic corticosteroids.

RESULTS

Fifty-four samples collected from hospitalized patients were analyzed, and viral pathogens were identified in 45 patients (83.3%) using multiplex PCR assay. HRV-A, -B, and -C were detected in 16 (29.6%), one (1.9%), and 16 (29.6%) patients, respectively. The detection rates of HRV-C were lower in the ICS-treated group compared with those in the ICS-untreated group (p = 0.01), whereas maintenance ICS treatment did not affect the detection rate for viral pathogens in total and HRV-A. Changes in FEV1% predicted in patients treated with systemic corticosteroids for 6-8 days (n = 10; median, 4.90%) were higher than those in patients treated for 3-5 days (n = 8; median, - 10.25%) (p = 0.0085).

CONCLUSIONS

Maintenance ICS reduced the detection rates of HRV (mainly HRV-C) in school-age inpatients with asthma exacerbations, and the treatment periods of systemic corticosteroids during exacerbations affected lung function after HRV-induced exacerbations. The protective effects of corticosteroids on virus-induced asthma exacerbations may be dependent upon the types of viral pathogen.

From preschool wheezing to asthma: Environmental determinants

Wheezing is common among preschool children, representing a group of highly heterogeneous conditions with varying natural history. Several phenotypes of wheezing have been proposed to facilitate the identification of young children who are at risk of subsequent development of asthma. Epidemiological and immunological studies across different populations have revealed the key role of environmental factors in influencing the progression from preschool wheezing to childhood asthma. Significant risk factors include severe respiratory infections, allergic sensitization, and exposure to tobacco smoke. In contrast, a farming/rural environment has been linked to asthma protection in both human and animal studies. Early and intense exposures to microorganisms and microbial metabolites have been demonstrated to alter host immune responses to allergens and viruses, thereby driving the trajectory away from wheezing illness and asthma. Ongoing clinical trials of candidate microbes and microbial products have shown promise in shaping the immune function to reduce episodes of viral-induced wheezing. Moreover, restoring immune training may be especially important for young children who had reduced microbial exposure due to pandemic restrictions. A comprehensive understanding of the role of modifiable environmental factors will pave the way for developing targeted prevention strategies for preschool wheezing and asthma.

Early-immune development in asthma: A review of the literature

This review presents a comprehensive examination of the various factors contributing to the immunopathogenesis of asthma from the prenatal to preschool period. We focus on the contributions of genetic and environmental components as well as the role of the nasal and gut microbiome on immune development. Predisposing genetic factors, including inherited genes associated with increased susceptibility to asthma, are discussed alongside environmental factors such as respiratory viruses and pollutant exposure, which can trigger or exacerbate asthma symptoms. Furthermore, the intricate interplay between the nasal and gut microbiome and the immune system is explored, emphasizing their influence on allergic immune development and response to environmental stimuli. This body of literature underscores the necessity of a comprehensive approach to comprehend and manage asthma, as it emphasizes the interactions of multiple factors in immune development and disease progression.

Association of Asthma Risk Alleles With Acute Respiratory Tract Infections and Wheezing Illnesses in Young Children

BACKGROUND

Genome-wide association studies have identified several risk alleles for early childhood asthma, particularly in the 17q21 locus and in the cadherin-related family member 3 (CDHR3) gene. Contribution of these alleles to the risk of acute respiratory tract infections (ARI) in early childhood is unclear.

METHODS

We analyzed data from the STEPS birth-cohort study of unselected children and the VINKU and VINKU2 studies on children with severe wheezing illness. Genome-wide genotyping was performed on 1011 children. We analyzed the association between 11 preselected asthma risk alleles and the risk of ARIs and wheezing illnesses of various viral etiologies.

RESULTS

The asthma risk alleles in CDHR3, GSDMA, and GSDMB were associated with an increased rate of ARIs (for CDHR3, incidence rate ratio [IRR], 1.06; 95% confidence interval [CI], 1.01-1.12; P = .02), and risk allele in CDHR3 gene with rhinovirus infections (IRR, 1.10; 95% CI, 1.01-1.20, P = .03). Asthma risk alleles in GSDMA, GSDMB, IKZF3, ZPBP2, and ORMDL3 genes were associated with wheezing illnesses in early childhood, especially rhinovirus-positive wheezing illnesses.

CONCLUSIONS

Asthma risk alleles were associated with an increased rate of ARIs and an increased risk of viral wheezing illnesses. Nonwheezing and wheezing ARIs and asthma may have shared genetic risk factors. Clinical Trials Registration. NCT00494624 and NCT00731575.

Viral infections and chronic rhinosinusitis

Viral infections are the most common cause of upper respiratory infections; they frequently infect adults once or twice and children 6 to 8 times annually. In most cases, these infections are self-limiting and resolve. However, many patients with chronic rhinosinusitis (CRS) relay that their initiating event began with an upper respiratory infection that progressed in both symptom severity and duration. Viruses bind to sinonasal epithelia through specific receptors, thereby entering cells and replicating within them. Viral infections stimulate interferon-mediated innate immune responses. Recent studies suggest that viral infections may also induce type 2 immune responses and stimulate the aberrant production of cytokines that can result in loss of barrier function, which is a hallmark in CRS. The main purpose of this review will be to highlight common viruses and their associated binding receptors and highlight pathophysiologic mechanisms associated with alterations in mucociliary clearance, epithelial barrier function, and dysfunctional immune responses that might lead to a further understanding of the pathogenesis of CRS.

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.

Interactive effects between CDHR3 genotype and rhinovirus species for diagnosis and severity of respiratory tract infections in hospitalized children

Rhinovirus (RV) is the leading pathogen causing childhood wheezing, with rhinovirus C (RV-C) species reported to cause asthma exacerbation. Allele A of single-nucleotide polymorphism (SNP) CDHR3_rs6967330 upregulates epithelial expression of RV-C receptors which results in more severe asthma exacerbations in children. Nevertheless, there are limited data on interactions between CDHR3 variants and their impact on severity of RV-related pediatric respiratory tract infections (RTIs). Medical records of RV-related RTIs in children aged below 18 years who were hospitalized in two public hospitals in 2015-2016 were independently reviewed by two paediatricians. Archived nasopharyngeal aspirates were retrieved for RV detection and sequencing as well as CDHR3 genotyping. HaploView v.5.0 and generalized multifactor dimensionality reduction (GMDR) analysis were employed for haplotypic assignment and gene-environment interaction analyses. Among 1019 studied cases, our results confirmed the relationship between RV-C species and more severe RTIs. Besides the top risk variant rs6967330-A, we identified rs140154310-T to be associated with RV-C susceptibility under the additive model [odds ratio (OR) 2.53, 95% CI 1.15-5.56; P = 0.021]. Rs140154310 was associated with wheezing illness (OR 2.38, 95% CI 1.12-5.04; P = 0.024), with such association being stronger in subjects who wheezed due to RV-C infections (OR 2.71, 95% CI 1.32-5.58; P = 0.007). Haplotype GAG constructed from rs4730125, rs6967330, and rs73195665 was associated with increased risk of RV-C infection (OR 1.71, 95% CI 1.11-2.65; P = 0.016) and oxygen supplementation (OR 1.93, 95% CI 1.13-3.30; P = 0.016). GMDR analyses revealed epistatic interaction between rs140154310 and rs6967330 of CDHR3 for RV-C infection (P = 0.001), RV-C-associated lower RTI (P = 0.004), and RV-C-associated wheeze (P = 0.007). There was synergistic gene-environmental interaction between rs3887998 and RV-C for more severe clinical outcomes (P < 0.001). To conclude, rs140154310-T is another risk variant for RV-C susceptibility and more severe RTIs. Synergistic epistatic interaction is found between CDHR3 SNPs and RV-C for RTI severity, which is likely mediated by susceptibility to RV-C. Haplotypic analysis and GMDR should be included in identifying prediction models of CDHR3 for childhood asthma and RTIs. IMPORTANCE This case-control study investigated the interaction between CDHR3 genotypes and rhinovirus (RV) species on disease severity in Hong Kong children hospitalized for respiratory tract infection (RTI). There were synergistic effects between RV-C and CDHR3 SNPs for RTI severity, which was mainly driven by RV-C. Specifically, rs6967330 and rs140154310 alone and their epistatic interaction were associated with RV-C-related and severe RTIs in our subjects. Therefore, genotyping of CDHR3 SNPs may help physicians formulate prediction models for severity of RV-associated RTIs.

Epidemiology and Immunopathogenesis of Virus Associated Asthma Exacerbations

Asthma is a common airway disease, affecting millions of people worldwide. Although most asthma patients experience mild symptoms, it is characterized by variable airflow limitation, which can occasionally become life threatening in the case of a severe exacerbation. The commonest triggers of asthma exacerbations in both children and adults are viral infections. In this review article, we will try to investigate the most common viruses triggering asthma exacerbations and their role in asthma immunopathogenesis, since viral infections in young adults are thought to trigger the development of asthma either right away after the infection or at a later stage of their life. The commonest viral pathogens associated with asthma include the respiratory syncytial virus, rhinoviruses, influenza and parainfluenza virus, metapneumovirus and coronaviruses. All these viruses exploit different molecular pathways to infiltrate the host. Asthmatics are more prone to severe viral infections due to their unique inflammatory response, which is mostly characterized by T2 cytokines. Unlike the normal T1 high response to viral infection, asthmatics with T2 high inflammation are less potent in containing a viral infection. Inhaled and/or systematic corticosteroids and bronchodilators remain the cornerstone of asthma exacerbation treatment, and although many targeted therapies which block molecules that viruses use to infect the host have been used in a laboratory level, none has been yet approved for clinical use. Nevertheless, further understanding of the unique pathway that each virus follows to infect an individual may be crucial in the development of targeted therapies for the commonest viral pathogens to effectively prevent asthma exacerbations. Finally, biologic therapies resulted in a complete change of scenery in the treatment of severe asthma, especially with a T2 high phenotype. All available data suggest that monoclonal antibodies are safe and able to drastically reduce the rate of viral asthma exacerbations.

Rhinovirus C15 Attenuates Relaxation and cAMP Production in Human Airways and Smooth Muscle

Rhinoviruses (RVs) evoke as many as 85% of acute asthma exacerbations in children and 50% in adults and can induce airway hyperresponsiveness and decrease efficacy of current therapeutics to provide symptom relief. Using human precision-cut lung slices (hPCLSs), primary human air-liquid interface-differentiated airway epithelial cells (HAECs), and human airway smooth muscle (HASM) as preclinical experimental models, we demonstrated that RV-C15 attenuates agonist-induced bronchodilation. Specifically, airway relaxation to formoterol and cholera toxin, but not forskolin (Fsk), was attenuated following hPCLS exposure to RV-C15. In isolated HASM cells, exposure to conditioned media from RV-exposed HAECs decreased cellular relaxation in response to isoproterenol and prostaglandin E2, but not Fsk. Additionally, cAMP generation elicited by formoterol and isoproterenol, but not Fsk, was attenuated following HASM exposure to RV-C15-conditioned HAEC media. HASM exposure to RV-C15-conditioned HAEC media modulated expression of components of relaxation pathways, specifically GNAI1 and GRK2. Strikingly, similar to exposure to intact RV-C15, hPCLS exposed to UV-inactivated RV-C15 showed markedly attenuated airway relaxation in response to formoterol, suggesting that the mechanism(s) of RV-C15-mediated loss of bronchodilation is independent of virus replication pathways. Further studies are warranted to identify soluble factor(s) regulating the epithelial-driven smooth muscle loss of β2-adrenergic receptor function.

Rhinoviruses A and C elicit long-lasting antibody responses with limited cross-neutralization

Rhinoviruses (RVs) can cause severe wheezing illnesses in young children and patients with asthma. Vaccine development has been hampered by the multitude of RV types with little information about cross-neutralization. We previously showed that neutralizing antibody (nAb) responses to RV-C are detected twofold to threefold more often than those to RV-A throughout childhood. Based on those findings, we hypothesized that RV-C infections are more likely to induce either cross-neutralizing or longer-lasting antibody responses compared with RV-A infections. We pooled RV diagnostic data from multiple studies of children with respiratory illnesses and compared the expected versus observed frequencies of sequential infections with RV-A or RV-C types using log-linear regression models. We tested longitudinally collected plasma samples from children to compare the duration of RV-A versus RV-C nAb responses. Our models identified limited reciprocal cross-neutralizing relationships for RV-A (A12-A75, A12-A78, A20-A78, and A75-A78) and only one for RV-C (C2-C40). Serologic analysis using reference mouse sera and banked human plasma samples confirmed that C40 infections induced nAb responses with modest heterotypic activity against RV-C2. Mixed-effects regression modeling of longitudinal human plasma samples collected from ages 2 to 18 years demonstrated that RV-A and RV-C illnesses induced nAb responses of similar duration. These results indicate that both RV-A and RV-C nAb responses have only modest cross-reactivity that is limited to genetically similar types. Contrary to our initial hypothesis, RV-C species may include even fewer cross-neutralizing types than RV-A, whereas the duration of nAb responses during childhood is similar between the two species. The modest heterotypic responses suggest that RV vaccines must have a broad representation of prevalent types.

Rhinovirus C causes heterogeneous infection and gene expression in airway epithelial cell subsets

Rhinoviruses infect ciliated airway epithelial cells, and rhinoviruses' nonstructural proteins quickly inhibit and divert cellular processes for viral replication. However, the epithelium can mount a robust innate antiviral immune response. Therefore, we hypothesized that uninfected cells contribute significantly to the antiviral immune response in the airway epithelium. Using single-cell RNA sequencing, we demonstrate that both infected and uninfected cells upregulate antiviral genes (e.g. MX1, IFIT2, IFIH1, and OAS3) with nearly identical kinetics, whereas uninfected non-ciliated cells are the primary source of proinflammatory chemokines. Furthermore, we identified a subset of highly infectable ciliated epithelial cells with minimal interferon responses and determined that interferon responses originate from distinct subsets of ciliated cells with moderate viral replication. These findings suggest that the composition of ciliated airway epithelial cells and coordinated responses of infected and uninfected cells could determine the risk of more severe viral respiratory illnesses in children with asthma, chronic obstructive pulmonary disease, and genetically susceptible individuals.

Inhaled drug delivery for the targeted treatment of asthma

Asthma is a chronic lung disease affecting millions worldwide. While classically acknowledged to result from allergen-driven type 2 inflammatory responses leading to IgE and cytokine production and the influx of immune cells such as mast cells and eosinophils, the wide range in asthmatic pathobiological subtypes lead to highly variable responses to anti-inflammatory therapies. Thus, there is a need to develop patient-specific therapies capable of addressing the full spectrum of asthmatic lung disease. Moreover, delivery of targeted treatments for asthma directly to the lung may help to maximize therapeutic benefit, but challenges remain in design of effective formulations for the inhaled route. In this review, we discuss the current understanding of asthmatic disease progression as well as genetic and epigenetic disease modifiers associated with asthma severity and exacerbation of disease. We also overview the limitations of clinically available treatments for asthma and discuss pre-clinical models of asthma used to evaluate new therapies. Based on the shortcomings of existing treatments, we highlight recent advances and new approaches to treat asthma via inhalation for monoclonal antibody delivery, mucolytic therapy to target airway mucus hypersecretion and gene therapies to address underlying drivers of disease. Finally, we conclude with discussion on the prospects for an inhaled vaccine to prevent asthma.

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.