Mouthrinses against SARS-CoV-2: anti-inflammatory effectivity and a clinical pilot study

Abstract

Purpose: The scope of this research endeavor was the determination of the applicability of over the counter mouthwash solutions in reducing the viral load in the saliva of COVID-19 patients and hence decreasing their infectivity. Beyond that, new experimental mouthwashes were investigated in terms of a possible positive immune modulation, which might offer an additional opportunity for a positive pharmaceutical effect.

Methods: The effectivity of the mouth washing solution was determined on 34 hospitalized COVID-19 patients by measuring the viral load by RT-qPCR in pharyngeal swabs, which were taken before and after rinsing. The inflammatory modulation thru the experimental solutions was assayed in an in vitro model of virus infected nasopharyngeal epithelium cells.

Results: The clinical pilot study demonstrated that the mouth rinsing solution was able to reduce the viral load by about 90% in the saliva of most patients. This reduction was determined to persist for about 6 h. In the experimental solutions, the ingredients dexpanthenol and zinc were able to reduce the expression of proinflammatory cytokines in the cell culture model, while the antiviral response was not altered significantly.

Conclusion: We recommend the application of mouth wash solutions to COVID-19 patients, since our results indicate a reduction in infectivity and might govern the protection of health care professionals. Further improvement to the over the counter formulation can be made by utilizing zinc and dexpanthenol, as they which might be beneficial for the patients' health.

Keywords: Anti-inflammatory; Covid-19; Dexpanthenol; Mouth wash; Zinc.

Fig. 1

Vitality of oral epithelial cells after incubation with the six test substances. a The cells were incubated for 24 h with different v/v ratios of the test substances. The vitality was measured in terms of metabolic activity via an MTS assay. The test substance A, C and F exhibited only minor effects on the metabolic activity. The test substance D and E showed a positive effect on the vitality of epithelial cell. The test substance B decreased the metabolic activity of the assayed cells. (one tailed Mann–Whitney-U with 95% confidence interval, ** ≤ 0.01, *** ≤ 0.001) b The cell culture model of epithelium treated with 10 µg/ml Poly (I:C) showed a reproducible strong upregulation of inflammatory marker TNF-α. Interestingly, it also showed a significant downregulation of this inflammation upon treatment with 1% (v/v) of test substance A, E and F. (Depicted: mean and standard deviation; t test with welch correction, two tailed with 95% confidence interval, ** ≤ 0.01)

Fig. 2

Viability of oral epithelial cells treated with the four test substances. The exclusion of Carrageenan and phenoxyethanol resulted in a highly in vitro biocompatible formulation allowing high concentration of E*, F* and D to be used in vitro without causing severe cellular stress. Isolated from treated and untreated cells. RT-qPCR results are shown in Fig. 3

Fig. 3

Investigation of action of the test substances on cells treated with the test substances E*, F* and D. Compared to the medium control (MC) a strong upregulation of all transcripts was observed upon application of Poly (I:C) (P). More importantly, the expression of the cytokines (TNF-α, IL-6, GM-CSF) and chemokines (CXCL-9 and CXCL-10) was significantly downregulated by additional application of test substance E*. Some were more sensitive to dexpanthenol (chemokines) and some susceptible to zinc (GM-CSF). The antiviral transcripts (INF-β, MX-1 and OAS-1) on the other side were slightly upregulated (MX-1 by F*), slightly downregulated (OAS-1 by zinc + dexpanthenol) or not influenced at all (INF-β) (t test with welch correction, two tailed with 95% confidence interval,* ≤ 0.05, ** ≤ 0.01, *** ≤ 0.001, **** ≤ 0.0001). Three anionic surfactants led to a significant reduction of the viral load in the pharynx

Fig. 4

a A clear reduction of the viral load was detectable in the population of SARS-CoV-2 patients after gargling with the applied mouth wash solution. This change was statistically highly significant (Wilcoxon matched-pairs signed rank test, with 95% confidence interval, **** ≤ 0.0001). b The depiction of the reduction of the viral load shows that it is reduced by a factor of at least two (median: dashed line, quartile: dotted lines). c Assay of the time course of the viral load development in the nasopharynx. The viral load requires around 6 h to recover from the rinsing process