Background Vercelli and coworkers recently observed that a well-established bacterial lysate (OM-85, Vifor Pharma; CH) was able to downregulate the expression of Angiotensin-Converting Enzyme 2 (ACE2) on epithelial cells. This downregulation was also associated with a reduced infectivity of cells, resulting in a reduced viral titre. We evaluated whether another bacterial lysate (Lantigen B, Bruschettini Ltd; Italy) may have similar activities. However, while OM-85 is given per os and has a systemic effect after absorption at the gut level, Lantigen B is given locoregionally. Thus, the concentration that the bacterial lysate can reach at the mucosal level seems to be promising. Methods Oropharyngeal cells were collected from healthy donors. After 24 hours of treatment in vitro with doses of Lantigen B comparable to those that are reached in vivo, the expression of ACE2 was evaluated by direct fluorescence and flow cytometry. Results A reduction in the number of ACE2-positive cells was observed in 80% of treated samples. Only a few donors had poor expression of ACE2, and in these donors, the downregulation was less evident or absent. Conclusions These results suggest that Lantigen B, at pharmacological doses, could be an interesting drug to reduce ACE2 expression on oropharyngeal cells, thus contributing to the prophylaxis of COVID-19 in humans.
The bacterial lysate Lantigen B reduces the expression of ACE2 on primary oropharyngeal cells