Indeed, several studies have described a high viral load in the nasal tract during the first days of SARS-CoV-2 infection. The nose is not only a portal for viral infection but also an important site for viral replication. Therefore, the main site of initial infection is the nasopharyngeal epithelium and, in particular, the ciliated cells, which express high levels of ACE2, and proteases TMPRSS2 and furin on their apical side. Upon inhalation, the virions bind to cells that express angiotensin-converting enzyme 2 (ACE2), and after host-cell proteases cleave the viral spike protein, the virions enter cells and cause infection. SARS-CoV-2 infection is mainly contracted from airborne virions. Of the variants, the most concerning in terms of severity of illness is the Delta variant. These “Variants of Concern” (VOC) have the potential to evade immunity following vaccination or recovery from infection, and breakthrough cases have been emerging at an increasing rate. Moreover, the emergence and spread of SARS-CoV-2 variants is a major threat to public health. Despite ongoing vaccination campaigns, there is a pressing need for new, effective personal protection measures against the infection. To resolve the current pandemic, governments worldwide have variably implemented a series of non-pharmaceutical interventions, from physical distancing, school closures and travel restrictions to better hygiene and face mask requirements. This virus is the third coronavirus known to cause severe disease in humans, and its emergence follows two global outbreaks by SARS in 2002–2003 and the Middle East respiratory syndrome-related coronavirus in 2012 (reviewed in ). The pandemic continues to have a major impact on daily conduct in our attempt to prevent the spread of the causative agent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The COVID-19 pandemic has had a massive toll on daily life and has strained the capacity of healthcare institutions. Its physical (non-pharmaceutical) mechanism of action, safety and efficacy warrant additional investigations both in vitro and in vivo for safety and efficacy against a broad spectrum of airborne viruses and allergens. The results suggest that AM-301 is safe and significantly decelerates SARS-CoV-2 replication in cell culture inhibition assays of prophylaxis (pre-viral load application) and mitigation (post-viral load application). When AM-301 administration was started 24 h after infection, viral titer was reduced by about 12-folds and 3-folds on Day 4. controls over 4 days, reaching a maximum reduction of 99% in case of infection from the wild-type SARS-CoV-2 variant and more than 83% in case of the Delta variant. Prophylactic treatment with AM-301 significantly reduced viral titer vs. No toxic effects of AM-301 on the nasal epithelium were found. Efficacy against SARS-CoV-2 infection was evaluated in pre-viral load and post-viral load application on airway epithelium. Safety was assessed in assays for tight junction integrity, cytotoxicity and cilia beating frequency. In the present study, we test the safety and efficacy of a newly developed nasal spray (AM-301, marketed as Bentrio) against infection by SARS-CoV-2 and its Delta variant on an in vitro 3D-model of the primary human nasal airway epithelium. The nasal epithelium is a key portal for infection by respiratory viruses such as SARS-CoV-2 and represents an important target for prophylactic and therapeutic interventions.
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