Molnupiravir combined with different repurposed drugs further inhibits SARS-CoV-2 infection in human nasal epithelium in vitro

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), first identified in late 2019, has caused a worldwide pandemic with unprecedented economic and societal impact. Currently, several vaccines are available, and multitudes of antiviral treatments have been proposed and tested. Although many of the vaccines show high clinical efficacy, they are not equally accessible worldwide. Additionally, due to the continuous emergence of new virus variants, and generally short duration of immunity, the development of safe and effective antiviral treatments remains of the utmost importance. Since the emergence of SARS-CoV-2, substantial efforts have been undertaken to repurpose existing and approved drugs for accelerated clinical testing and potential emergency use authorizations. However, drug-repurposing using high throughput screenings in cellular assays, often identify hits that later prove ineffective in clinical studies. Our approach was to evaluate the activity of compounds that have either been tested clinically or already undergone extensive preclinical profiling, using a standardized in vitro model of human nasal epithelium. Secondly, we evaluated drug combinations using sub-maximal doses of each active single compound. Here, we report the antiviral effects of 95 single compounds and 30 combinations. The data show that selected drug combinations including 10 μM of molnupiravir, a viral RNA-dependent RNA polymerase (RdRp) inhibitor, effectively inhibit SARS-CoV-2 replication. This indicates that such combinations are worthy of further evaluation as potential treatment strategies against coronavirus disease 2019 (COVID-19).

Efficacy and safety evaluation of a hypertonic seawater solution enriched with manganese and copper salts

Background: Nasal irrigation is commonly recommended as an adjuvant treatment for blocked nose. In the present study, the safety and efficacy profile of Stérimar Blocked Nose (SBN), a hypertonic seawater solution enriched with manganese and copper salts, has been evaluated on nasal epithelium, in vitro. Methodology: 3D reconstituted human nasal epithelium tissue model, MucilAir™, has been used to investigate the safety of SBN on nasal epithelium by measuring trans-epithelial electrical resistance (TEER), cytotoxicity (lactate dehydrogenase (LDH) release) and phlogosis-related effects (interleukin-8 secretion). Efficacy assessment was measured by ciliary beat frequency (CBF), mucociliary clearance (MCC) and antimicrobial activities (against Staphylococcus aureus and Pseudomonas aeruginosa). Results: Four-day SBN treatment did not compromise the nasal epithelium integrity as TEER values were over the tissue integrity limit. SBN treatment did not exert cytotoxic (LDH release) or pro-inflammatory effects (IL-8 secretion). SBN treatment significantly increased the CBF and MCC rates compared to untreated cells. SBN treatment exerted a bactericidal effect on S. aureus and P. aeruginosa cultures, whereas seawater not enriched in copper and manganese had only a bacteriostatic effect. Conclusions: The results demonstrate that SBN is a safe formula for use on human nasal epithelium. The results also suggest a better potential therapeutic role for SBN in comparison to not-enriched seawater when used to control nasal congestion and inhibit bacterial growth which may cause nasal congestion.

The nasal symbiont Staphylococcus epidermidis shapes the cellular environment to decrease expression of SARS-CoV-2 entry factors in nasal epithelium

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.

Is a diluted seawater-based solution safe and effective on human nasal epithelium?

Purpose Nasal irrigation is an effective method for alleviating several nasal symptoms and regular seawater-based nasal irrigation is useful for maintaining nasal hygiene which is essential for appropriate functioning of the nose and for preventing airborne particles including some pollutants, pathogens, and allergens from moving further in the respiratory system. However, safety studies on seawater-based nasal irrigation are scarce. In this study, the safety and efficacy of a diluted isotonic seawater solution (Stérimar Nasal Hygiene, SNH) in maintaining nasal homeostasis were evaluated in vitro. Methods Safety was assessed by measuring tissue integrity via transepithelial electrical resistance (TEER). Efficacy was measured by mucociliary clearance (MCC), mucin secretion, and tissue re-epithelization (wound repair) assays. All assays were performed using a 3D reconstituted human nasal epithelium model. Results In SNH-treated tissues, TEER values were statistically significantly lower than the untreated tissues; however, the values were above the tissue integrity limit. SNH treatment significantly increased MCC (88 vs. 36 µm/s, p < 0.001) and mucin secretion (1717 vs. 1280 µg/ml, p < 0.001) as compared to untreated cultures. Faster wound closure profile was noted upon pre-SNH treatment as compared to classical isotonic saline solution pre-treatment (90.5 vs. 50.7% wound closure 22 h after wound generation). Conclusion SNH did not compromise the integrity of the nasal epithelium in vitro. Furthermore, SNH was effective for removal of foreign particles through MCC increase and for enhancing wound repair on nasal mucosa.