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Remarkable progress has recently been achieved to identify the biological function and potential value of novel therapeutic targets for the effective control of allergic asthma. Interferon (IFN)-λ has been suggested to restrict chronic inflammation in the lungs of asthmatic mice and we sought to determine the contribution of IFN-λ as an asthma therapeutic. We show that inhaled IFN-λ can restrict Th2 and Th17 inflammation in the lungs of asthmatic mice, accompanied with alteration of IL-10 secretion. BALB/C mice were used for an asthmatic mouse model with OVA. Recombinant IFN-λs (IFN-λ

IL-17 family cytokines are directly involved in host immune responses and the critical mediators for host defense against infection or inflammation. IL-17C is highly expressed in respiratory epithelium and is induced after acute bacterial lung infection. However, the definite function of IL-17C induced by Pseudomonas aeruginosa (PAO1 strain) is not fully understood, and our study was designed to demonstrate IL-17C-induced immune response against PAO1 infection in nasal epithelium. Passage-2 normal human nasal epithelial (NHNE) cells were infected with PAO1 and the relationship between IL-17C-related immune responses and the iron absorption of PAO1, depending on inoculation of recombinant human IL-17C (rhIL-17C), was assessed by measuring the siderophore activity of PAO1. Microarray data showed that IL-17C expression increased 34.7 times at 8 hours postinfection (hpi) in NHNE cells, and IL-17C mRNA levels increased until 48 hpi. The PAO1 colonies significantly increased from 8 hpi in NHNE cells, and siderophore activity of PAO1 was enhanced in the supernatants of PAO1-infected NHNE cells. Interestingly, PAO1 colonies were reduced in PAO1-infected NHNE cells treated with rhIL-17C, and supernatants from NHNE cells treated with rhIL-17C also exhibited decreased PAO1 colonies. We found that the siderophore activity of PAO1 was significantly reduced in the supernatants of NHNE cells treated with rhIL-17C where LCN2 expression was highly elevated. Our findings indicate that IL-17C mediates an antibacterial effect against PAO1 by inhibiting siderophore activity in nasal epithelium. We propose that IL-17C might be an efficient mediator to suppress PAO1 infection through disturbing iron absorption of PAO1 in nasal epithelium.

The possibility has been suggested that interferon (IFN)-λs can be induced rapidly for restricting respiratory viral infection in asthmatic mice and may modulate Th2-related immune responses that underlie the pathogenesis of asthma. We sought to determine the in vivo contribution of IFN-λs on decrease of Th2 cytokines in the respiratory tract of in vivo asthma. Lungs of asthmatic mice were severely inflamed, with extensive inflammatory cell infiltration and increased goblet cell metaplasia with higher total lung resistance. The mean protein levels of TSLP and IL-33 from BAL fluid of asthmatic mice were significantly higher until 7 days. Following the collection of lung tissue of 20 asthmatic mice, TSLP and IL-33 gene expressions inversely correlated with mRNA levels of IFN-λ2/3. Asthmatic mice were administered recombinant IFN-λ2/3 via the intranasal route and the mRNA levels of IFN-stimulated genes were elevated to an even greater extent in the lung tissue of the mice without intranasal IFN-λ2/3. Asthma-related histopathologic lung inflammation was significantly improved and total lung resistance was maintained within normal range in IFN-λ2/3-treated asthmatic mice. Moreover, IFN-λ2/3-treated asthmatic mice exhibited significant decrease of secreted protein levels of TSLP and IL-33 in the BAL fluid until 7 days after IFN administration. The current data provide compelling evidence that the compensation of IFN-λs can restrict the secretion of epithelial-derived Th2 cytokines, accompanied with reduced asthmatic immunopathology and IFN-λs are critical for limiting Th2-mediated allergic responses in allergic asthma.

Our recent study presented that human nasal commensal Staphylococcus epidermidis could potentiate antiviral immunity in the nasal mucosa through interferon-related innate responses. Here, we found that human nasal commensal S. epidermidis promoted protease–protease inhibitor balance in favor of the host and prevented influenza A virus (IAV) replication in the nasal mucosa and lungs. A relatively higher induction of Serpine1 exhibited in S. epidermidis-inoculated nasal epithelium and S. epidermidis-induced Serpine1 significantly decreased the expression of serine proteases. Furthermore, the transcription of urokinase plasminogen activator (uPA) and Serpine1 was biologically relevant in S. epidermidis-inoculated nasal epithelium, and the induction of uPA might be related to the sequential increase of Serpine1 in human nasal epithelium. Our findings reveal that human nasal commensal S. epidermidis manipulates the cellular environment lacking serine proteases in the nasal epithelium through Serpine1 induction and disturbs IAV spread to the lungs at the level of the nasal mucosa.

Emerging evidence indicates that severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV-2) is transmitted through the human nasal mucosa via the principal entry factors angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2), which are highly expressed in the nasal epithelium. Therefore, the biologics targeting host entry factors on human nasal mucosa will be necessary for complete control of SARS-CoV-2. Our data reveal that ACE2 was more abundant in human nasal mucosa than lung tissue. Both ACE2 and TMPRSS2 transcriptions significantly decreased in nasal epithelium in response to S. epidermidis and were relatively lower in human nasal mucus with large numbers of S. epidermidis. ACE2 transcription was also reduced in nasal epithelium in response to nasal symbiont S. aureus. This study proposes that Staphylococcus species nasal commensals might potentially restrict SARS-CoV-2 entry to the nasal epithelium via down regulation of cellular receptors coupled with reduction of principal host protease., Graphical abstract, Biological sciences; Molecular biology; Microbiology; Virology

Background Emerging evidence indicates that severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV-2) targets the human nasal epithelium via the principal entry factors angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2), which are highly expressed in the nasal epithelium. However, little is known about suppressive biologics against SARS-CoV-2 entry factors. Here, we report that the nasal commensal Staphylococcus epidermidis altered the host transcriptional response against SARS-CoV-2 in the nasal epithelium by reducing ACE2 and TMPRSS2 gene expression in concert with an increase in serine-peptidase inhibitors. Results Our data reveal that ACE2 was more abundantly expressed in nasal epithelial (NHNE) cells than bronchial epithelial cells, and inoculation with S. epidermidis reduced ACE2 transcription in NHNE cells. Our data also show that TMPRSS2 mRNA was significantly decreased in NHNE cells and that S. epidermidis colony number in human nasal mucus was inversely correlated with ACE2 and TMPRSS2 gene expression in the nasal mucosa. In addition, levels of the serine-peptidase inhibitors SERPINE1 and SERPINE2 were significantly increased by S. epidermidis, and this accompanied reduction of TMPRSS2 transcription in nasal epithelial cells. Conclusion These results characterize the S. epidermidis-regulated host transcriptional response restricting SARS-CoV-2 entry to the nasal epithelium via downregulation of receptors and host protease for SARS-CoV-2 cellular invasion coupled with SERPINE1 and SERPINE2 induction.

Emerging evidence indicates that severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV-2) targets the human nasal epithelium via the principal entry factors angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2), which are highly expressed in the nasal epithelium. However, little is known about suppressive biologics against SARS-CoV-2 entry factors. Here, we show that the nasal commensal Staphylococcus epidermidis altered the host transcriptional response against SARS-CoV-2 by reducing ACE2 and TMPRSS2 gene expression in concert with an increase in serine protease inhibitors. Our data reveal that ACE2 was more abundantly expressed in nasal epithelial (NHNE) cells than bronchial epithelial cells, and inoculation with S. epidermidis reduced ACE2 transcription in NHNE cells. TMPRSS2 mRNA was significantly decreased in NHNE cells and S. epidermidis colony number in human nasal mucus was inversely correlated with ACE2 and TMPRSS2 gene expression in nasal mucosa. In addition, levels of the serine protease inhibitors SERPINE1 and SERPINE2 were significantly increased by S. epidermidis , and this accompanied reduction of TMPRSS2 transcription in nasal epithelial cells. These results characterize the S. epidermidis -regulated host transcriptional response restricting SARS-CoV-2 entry to the nasal epithelium via downregulation of cellular receptors and principal host protease of SARS-CoV-2 coupled with SERPINE1 and SERPINE2 induction. Funding: This work was supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education (2016R1D1A1B01014116 and 2019M3C9A6091945 to HJK). This research was also supported by a grant from the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare of the Republic of Korea (HI20C0546 to HJK). Declaration of Interest: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as potential conflicts of interest. Ethical Approval: Participation was voluntary, with written informed consent obtained from all subjects. This study was approved by the Institutional Review Board (IRB) of the Seoul National University College of Medicine (no. 1709-049-883).

Background: Our recent study presented that human nasal commensal Staphylococcus Epidermidis could potentiate antiviral immunity in the nasal mucosa through interferon-related innate responses. Here, we found that human nasal commensal S. epidermidis promoted protease–protease inhibitor balance in favor of the host and prevented influenza A virus (IAV) replication in the nasal mucosa and lungs. Methods: We examined the contribution of intranasal administration of human nasal S. epidermidis in controlling IAV infection using murine model and culture nasal epithelial cells. IAV mRNA, viral titer, nucleoprotein levels, and histopathologic findings were evaluated. The induction of S. epidermidis-regulated serine protease inhibitors and correlation of serine proteases were also determined. Findings: A relatively higher induction of Serpine1 exhibited in S. epidermidis-inoculated nasal epithelium and S. epidermidis-induced Serpine1 significantly decreased the expression of serine proteases. Furthermore, the transcription of urokinase plasminogen activator (uPA) and Serpine1 was biologically relevant in S. epidermidis-inoculated nasal epithelium, and the induction of uPA might be related with the sequential increase of Serpine1 in human nasal epithelium. Interpretation: Our findings reveal that human nasal commensal S. epidermidismanipulates the cellular environment lacking serine proteases in the nasal epithelium through Serpine1 induction and disturbs IAV spread to the lungs at the level of the nasal mucosa. Funding: This work was supported by the Basic Science Research Program through the National Research Foundation of Korea, funded by the Ministry of Education 2016R1D1A1B01014116, 2019M3C9A6091945, 2017M3A9F3041233) and was also supported by a grant from the Korean Health Technology R&D Project through the Korean Health Industry Development Institute, funded by the Ministry of Health & Welfare of the Republic of Korea (HI20C0546). Declaration of Interest: None to declare. Ethical Approval: The institutional review board (IRB) of the Seoul National University College of Medicine approved the protocol for this study (IRB #C2012248 [943]). In vivo experiments with C57BL/6J mice were carried out according to guidelines approved by the IRB of the Seoul National University College of Medicine (IACUC #2016-0093).

Background The host-microbial commensalism can shape the innate immune responses in respiratory mucosa and nasal microbiome also modulates front-line immune mechanism in the nasal mucosa. Inhaled allergens encounter the host immune system first in the nasal mucosa, and microbial characteristics of nasal mucus directly impact the mechanisms of initial allergic responses in nasal epithelium. However, the roles of the nasal microbiome in allergic nasal mucosa remain uncertain. We sought to determine the distribution of nasal microbiomes in allergic nasal mucosa and elucidate the interplay between nasal microbiome Staphylococcus species and Th2 cytokines in allergic rhinitis (AR) models. Results Staphylococcus aureus (AR-SA) and S. epidermidis (AR-SE) were isolated from the nasal mucosa of patients with AR. The influence of nasal microbiome Staphylococcus species on allergic nasal mucosa was also tested with in vitro and in vivo AR models. Pyrosequencing data showed that colonization by S. epidermidis and S. aureus was more dominant in nasal mucus of AR subjects. The mRNA and protein levels of IL-33 and TSLP were significantly higher in AR nasal epithelial (ARNE) cells which were cultured from nasal mucosa of AR subjects, and exposure of ARNE cells to AR-SA reduced IL-33 mRNA and secreted protein levels. Particularly, ovalbumin-driven AR mice inoculated with AR-SA by intranasal delivery exhibited significantly reduced IL-33 in their nasal mucosa. In the context of these results, allergic symptoms and Th2 cytokine levels were significantly downregulated after intranasal inoculation of AR-SA in vivo AR mice. Conclusion Colonization by Staphylococcus species was more dominant in allergic nasal mucosa, and nasal commensal S. aureus from subjects with AR mediates anti-allergic effects by modulating IL-33-dependent Th2 inflammation. The results demonstrate the role of host-bacterial commensalism in shaping human allergic inflammation.

IL-17 family cytokines are directly involved in host immune responses and the critical mediators for host defense against infection or inflammation. IL-17C is highly expressed in respiratory epithelium and is induced after acute bacterial lung infection. However, the definite function of IL-17C induced by

Middle East Respiratory Syndrome Coronavirus (MERS-CoV) causes severe respiratory in human with high mortality and it has been a challenge to determine optimum treatment for MERS-CoV-induced respiratory infection. Here, we observed the distribution of MERS-CoV receptors using human respiratory mucosa and also evaluated the contribution of interferon-lambdas (IFN-λs) in response to MERS-CoV infection using in vitro normal human nasal epithelial (NHNE) and bronchial epithelial (NHBE) cells. We found that the gene and protein expression of DPPIV, MERS-CoV receptor, were more dominantly located in nasal and bronchial epithelium although human nasal mucosa exhibited relatively lower DPPIV expression than lung parenchymal tissues. The quantitative mRNA level of the MERS-CoV envelope (upE) gene was significantly induced in MERS-CoV-infected cultured NHNE and NHBE cells until 3 days after infection. The induction of IFNs was identified in NHNE and NHBE cells after MERS-CoV infection and IFN-λs were predominantly increased in MERS-CoV-infected respiratory epithelial cells. Inoculation of IFN-λs to NHNE and NHBE cells suppressed MERS-CoV replication and in particular, IFN-λ4 showed a strong therapeutic effect in reducing MERS-CoV infection with higher induction of IFN-stimulated genes. Thus, IFN-λ has a decisive function in the respiratory epithelium that greatly limits MERS-CoV replication, and may be a key cytokine for better therapeutic outcomes against MERS-CoV infection in respiratory tract., Highlights • Respiratory epithelial cells might be a main target for MERS-CoV infection and transmission in the human respiratory tract. • An IFN-λ-mediated innate immune response is crucial for the clearance of MERS-CoV from the respiratory tract. • Recombinant IFN-λ4 shows potential as a therapeutic candidate to suppress MERS-CoV in respiratory epithelial cells.