Transcriptomics of rhinovirus persistence reveals sustained expression of RIG-I and interferon-stimulated genes in nasal epithelial cells in vitro

Unique immune and other responses of human nasal epithelial cells infected with H5N1 avian influenza virus compared to seasonal human influenza A and B viruses

Highly pathogenic avian influenza (HPAI) virus (e.g. H5N1) infects the lower airway to cause severe infections, and constitute a prime candidate for the emergence of disease X. The nasal epithelium is the primary portal of entry for respiratory pathogens, serving as the airway's physical and immune barrier. While HPAI virus predominantly infects the lower airway, not much is known about its interactions with the nasal epithelium. Hence, we sought to elucidate and compare the differential responses of the nasal epithelium against HPAI infection that may contribute to its pathology, and to identify critical response markers. We infected human nasal epithelial cells (hNECs) cultured at the air-liquid interface from multiple healthy donors with clinical isolates of major human seasonal influenza viruses (H1N1, H3N2, influenza B) and HPAI H5N1. The infected cells were subjected to virologic, transcriptomic and secretory protein analyses. While less adapted to infecting the nasal epithelium, HPAI H5N1 elicited unique host responses unlike seasonal influenza. Interestingly, H5N1 infection of hNECs induced responses indicative of subdued antiviral activity (e.g. reduced expression of IFNβ, and inflammasome mediators, IL-1α and IL-1β); decreased wound healing; suppressed re-epithelialization; compromised epithelial barrier integrity; diminished responses to oxidative stress; and increased transmembrane solute and ion carrier gene expression. These unique molecular changes in response to H5N1 infection may represent potential targets for enhancing diagnostic and therapeutic strategies for better surveillance and management of HPAI infection in humans.

Inhibitory Activity of Hydroxypropyl Methylcellulose on Rhinovirus and Influenza A Virus Infection of Human Nasal Epithelial Cells

The nasal epithelium is the primary site for entry of respiratory viruses. In comparison to oral administration, nasal drug applications directed locally to the site of infection can serve as early interventional barriers against respiratory virus pathogenesis by limiting viral spread in the upper airway. Experiments on the diffusion of methylene blue and nanoparticles in both water and low pH conditions revealed that hydroxypropyl methylcellulose (HPMC) can act as an effective physical barrier. This study also evaluated the activity of HPMC as a barrier against common respiratory viruses, i.e., rhinovirus (RV) and influenza A virus (IAV) using the in vitro human nasal epithelial cell (hNEC) model. Utilizing the hNEC infection model, we assessed the protective effects of HPMC in pH 3.5 and pH 7 buffers against RV and IAV. Acidic and pH-neutral buffers and HPMC dissolved in acidic and pH-neutral buffers were administered for 4 h prior to virus infection and at 4 h post-infection (hpi). The apical supernatant was harvested at 24 hpi to determine the viral loads of RV and IAV (H1N1 and H3N2). HPMC was demonstrated to exert protective effects in the infected hNECs independent of acidic pH. Pre-treatment with HPMC in acidic buffer significantly diminished viral loads for both RV and IAV infections of hNECs. Similarly, direct treatment of HPMC in acidic buffer after infection (4 hpi) also effectively decreased viral loads of both RV and IAV. Moreover, treatment using HPMC in acidic buffer before or after infection did not affect the epithelial integrity and ciliary function of hNECs. This study demonstrates the protective effects of HPMC in acidic buffer against RV and IAV infections of the human nasal epithelium.

Rhinoviral Infection of the Human Lung Vascular Endothelium May Protect From the Secondary Infection With Rhinovirus RV-16

Rhinoviruses are a major cause of respiratory infections, including asthma infectious exacerbations. Human rhinovirus 16 (RV-16) has been widely shown to infect respiratory epithelial cells and the human lung vascular endothelium. RV-16 was also observed to induce an IFN-β-dependent mechanism of antiviral intracellular mechanisms based on OAS-1 and PKR activity. This study aimed to investigate whether the human lung microvascular endothelial cells (HMVEC-L) infected with RV-16 display a resistance to subsequent infections with the same virus, RV-16. HMVEC-L were infected with RV-16 and reinfected with RV-16 on Day 5. IFN-β-dependent responses, antiviral protein expression, inflammatory cytokine levels, and a viral copy numbers were assessed by real-time PCR, flow cytometry, ELISA, and confocal microscopy. RV-16 infection induced a significant IFN-β production and an activation of IFN-β-dependent antiviral proteins in HMVEC-L. On Day 5 post infection, these antiviral mechanisms remained active. In cells reinfected with RV-16, significantly lower replication of RV-16 was observed as compared to cells primarily infected with RV-16 on Day 5. Concomitantly, reinfected HMVEC-L showed a weaker response in IFN-β and inflammatory cytokine production. HMVEC-L infected with RV-16 display a sustained activation of IFN-β-dependent antiviral mechanisms, conferring resistance to subsequent infections with RV-16.

Dynamic changes in the circulation of respiratory pathogens in children during and after the containment of the 2019 coronavirus disease pandemic in Kunming, China

PURPOSE

We aimed to determine the changes in the frequency of respiratory pathogens and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during containment of the 2019 coronavirus disease pandemic and elucidate the epidemiological interference that may have occurred after lifting pandemic measures.

METHODS

A total of 4,770 Nasopharyngeal swab samples were collected from children with ARTIs from the First People's Hospital of Yunnan Province between January 2022 and December 2023 and subjected to nucleic acid testing for 13 types of respiratory pathogens and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

RESULTS

The frequency of pathogens among children from 2020 to 2022 was in the following order: HRV > Mp > HADV > H3N2 > HMPV and HRV > HRSV > HPIV > H1N1 > H3N2. In weeks 1 to 3 of 2023, the frequency of pathogens significantly declined, and then H1N1 rebounded significantly in 2023. HRV, HRSV, and H3N2 showed a shift in the season of high frequency. Patterns of multi-pathogen infections were more complex in 2023 than in 2022, with HRV having a higher frequency and co-infection rate than other pathogens. These changes may have been associated with interference caused by the resurgence of SARS-CoV-2 prevalence, in addition to being influenced by changes in pandemic containment and lifting measures.

CONCLUSIONS

The frequency rate of common respiratory pathogens among children was not significantly different and remained high. The study findings help elucidate the aforementioned unique historical period and effectively control respiratory tract infections to reduce the harm to pediatric health caused by respiratory pathogens.

Updated epithelial barrier dysfunction in chronic rhinosinusitis: Targeting pathophysiology and treatment response of tight junctions

Tight junction (TJ) proteins establish a physical barrier between epithelial cells, playing a crucial role in maintaining tissue homeostasis by safeguarding host tissues against pathogens, allergens, antigens, irritants, etc. Recently, an increasing number of studies have demonstrated that abnormal expression of TJs plays an essential role in the development and progression of inflammatory airway diseases, including chronic obstructive pulmonary disease, asthma, allergic rhinitis, and chronic rhinosinusitis (CRS) with or without nasal polyps. Among them, CRS with nasal polyps is a prevalent chronic inflammatory disease that affects the nasal cavity and paranasal sinuses, leading to a poor prognosis and significantly impacting patients' quality of life. Its pathogenesis primarily involves dysfunction of the nasal epithelial barrier, impaired mucociliary clearance, disordered immune response, and excessive tissue remodeling. Numerous studies have elucidated the pivotal role of TJs in both the pathogenesis and response to traditional therapies in CRS. We therefore to review and discuss potential factors contributing to impair and repair of TJs in the nasal epithelium based on their structure, function, and formation process.

Concurrent loss of ciliary genes WDR93 and CFAP46 in phylogenetically distant birds

The respiratory system is the primary route of infection for many contagious pathogens. Mucociliary clearance of inhaled pathogens is an important innate defence mechanism sustained by the rhythmic movement of epithelial cilia. To counter host defences, viral pathogens target epithelial cells and cilia. For instance, the avian influenza virus that targets ciliated cells modulates the expression of WDR93, a central ciliary apparatus C1d projection component. Lineage-specific prevalence of such host defence genes results in differential susceptibility. In this study, the comparative analysis of approximately 500 vertebrate genomes from seven taxonomic classes spanning 73 orders confirms the widespread conservation of WDR93 across these different vertebrate groups. However, we established loss of the WDR93 in landfowl, geese and other phylogenetically independent bird species due to gene-disrupting changes. The lack of WDR93 transcripts in species with gene loss in contrast to its expression in species with an intact gene confirms gene loss. Notably, species with WDR93 loss have concurrently lost another C1d component, CFAP46, through large segmental deletions. Understanding the consequences of such gene loss may provide insight into their role in host-pathogen interactions and benefit global pathogen surveillance efforts by prioritizing species missing host defence genes and identifying putative zoonotic reservoirs.

Prolonged Primary Rhinovirus Infection of Human Nasal Epithelial Cells Diminishes the Viral Load of Secondary Influenza H3N2 Infection via the Antiviral State Mediated by RIG-I and Interferon-Stimulated Genes

Our previous study revealed that prolonged human rhinovirus (HRV) infection rapidly induces antiviral interferons (IFNs) and chemokines during the acute stage of infection. It also showed that expression levels of RIG-I and interferon-stimulated genes (ISGs) were sustained in tandem with the persistent expression of HRV RNA and HRV proteins at the late stage of the 14-day infection period. Some studies have explored the protective effects of initial acute HRV infection on secondary influenza A virus (IAV) infection. However, the susceptibility of human nasal epithelial cells (hNECs) to re-infection by the same HRV serotype, and to secondary IAV infection following prolonged primary HRV infection, has not been studied in detail. Therefore, the aim of this study was to investigate the effects and underlying mechanisms of HRV persistence on the susceptibility of hNECs against HRV re-infection and secondary IAV infection. We analyzed the viral replication and innate immune responses of hNECs infected with the same HRV serotype A16 and IAV H3N2 at 14 days after initial HRV-A16 infection. Prolonged primary HRV infection significantly diminished the IAV load of secondary H3N2 infection, but not the HRV load of HRV-A16 re-infection. The reduced IAV load of secondary H3N2 infection may be explained by increased baseline expression levels of RIG-I and ISGs, specifically MX1 and IFITM1, which are induced by prolonged primary HRV infection. As is congruent with this finding, in those cells that received early and multi-dose pre-treatment with Rupintrivir (HRV 3C protease inhibitor) prior to secondary IAV infection, the reduction in IAV load was abolished compared to the group without pre-treatment with Rupintrivir. In conclusion, the antiviral state induced from prolonged primary HRV infection mediated by RIG-I and ISGs (including MX1 and IFITM1) can confer a protective innate immune defense mechanism against secondary influenza infection.

The role of hypoxia in the pathophysiology of chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a chronic inflammatory disease of the nasal cavity characterized by excessive nasal mucus secretion and nasal congestion. The development of CRS is related to pathological mechanisms induced by hypoxia. Under hypoxic conditions, the stable expression of both Hypoxia inducible factor-1 (HIF-1) α and HIF-2α are involved in the immune response and inflammatory pathways of CRS. The imbalance in the composition of nasal microbiota may affect the hypoxic state of CRS and perpetuate existing inflammation. Hypoxia affects the differentiation of nasal epithelial cells such as ciliated cells and goblet cells, induces fibroblast proliferation, and leads to epithelial-mesenchymal transition (EMT) and tissue remodeling. Hypoxia also affects the proliferation and differentiation of macrophages, eosinophils, basophils, and mast cells in sinonasal mucosa, and thus influences the inflammatory state of CRS by regulating T cells and B cells. Given the multifactorial nature in which HIF is linked to CRS, this study aims to elucidate the effect of hypoxia on the pathogenic mechanisms of CRS.