key: cord-0310099-wgnrtden
authors: Pizzimenti, Caterina; D’Agostino, Antonella; Pirrello, Paola; Rinaldi, Gilberto; Melioli, Giovanni
title: The bacterial lysate Lantigen B reduces the expression of ACE2 on primary oropharyngeal cells
date: 2022-05-08
journal: bioRxiv
DOI: 10.1101/2022.05.06.490962
sha: c4d4d8bbc311fa1d9774fa5b95e225722916265c
doc_id: 310099
cord_uid: wgnrtden

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.

However, while OM-85 is given per os and has a systemic effect after absorption at the gut 26 level, Lantigen B is given locoregionally. Thus, the concentration that the bacterial lysate can 27 reach at the mucosal level seems to be promising. 28

Methods: Oropharyngeal cells were collected from healthy donors. After 24 hours of 29 treatment in vitro with doses of Lantigen B comparable to those that are reached in vivo, the 30 expression of ACE2 was evaluated by direct fluorescence and flow cytometry. The cell surface molecule angiotensin-converting enzyme 2 (ACE2) is the main receptor for 46 SARS-CoV-2 spike (S) protein attachment [1, 2]. The binding of the spike protein to the 47 ACE2 receptor, together with other mechanisms, allows the fusion of the virus and the cell 48 membrane, thus infecting the target cell. ACE2 has been shown in many different cell types, 49 including nasal, intestinal, kidney, testis, gallbladder, and heart cells, and, to a lesser extent, 50 tongue, tonsil, and the olfactory region cells [3, 4] 51

The COVID-19 pandemic has pushed research to the limit, and in a few months, not 52 only advanced protocols for virus identification but also active vaccines have been developed This effect seems to be strictly related to the presence of the bacterial antigens 163 because the excipients and preservatives have no effect when used alone. Furthermore, the 164 surface expression of CD54, a rhinovirus receptor, was unmodified by in vitro treatment with 165 Lantigen B, thus suggesting that, at least in these experimental conditions, the 166 downregulation of ACE2 seems to be bacterial lysate specific. 167

The major limitation of this study is represented by the absence of any assay of 168

However, even if not formally demonstrated, this seems to be highly possible at least 170 comparing the results of the reduction in the expression of ACE2 in these experiments with 171 those described by Vercelli et al. 172

In conclusion, Lantigen B, a bacterial lysate used for decades in the prophylaxis of 173 recurrent respiratory infections, has well-established activity in reducing the number of infections in clinical trials. Our novel findings add that Lantigen B has activity that could be 175 extremely useful in the prophylaxis of COVID-19 (or at least in the prevention of SARS-176

CoV-2 asymptomatic infections), particularly in the period that seems to be less protected by 177 vaccines. Thus, in addition to the well-known effects of bacterial lysates on the adaptive and 178 innate immune response, the finding of this capability of Lantigen B adds to the mechanism 179 of action of bacterial lysates. 

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