Hypertonic saline solution inhibits SARS-CoV-2 in vitro assay

Abstract

We are facing an unprecedented global health crisis caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). At this date more than 680 thousand people have died due to coronavirus disease 2019 (COVID-19). Unfortunately, until now no effective treatment to combat the virus and vaccine are available. We performed experiments to test if hypertonic saline solution is able to inhibit virus replication in vitro. Our data shows that 260 mM NaCl (1.5%) inhibits 100% SARS-CoV-2 replication in Vero cells. Furthermore, our results suggest that the virus replication inhibition is due to an intracellular mechanism and not due to the dissociation between spike SARS-CoV-2 protein and its human receptor angiotensin-converting enzyme 2 interaction. NaCl depolarizes the plasma membrane supposedly associated with the inhibition of the SARS-CoV-2 life cycle. This observation could lead to simple, safe and low cost interventions at various stages of COVID-19 treatment, improving the prognosis of infected patients, thereby mitigating the social and economic costs of the pandemic.

Essentials in saline pharmacology for nasal or respiratory hygiene in times of COVID-19

“…Thirdly, saline may interfere with the SARS-CoV-2 infectivity, possibly by interacting with the viral ACE2 entry mechanism, as well as with ENaC [33].…”

“…The pharmacological/pharmacodynamic effects of saline are effectuated at concentrations already reached by isotonic saline. In vivo, the limited action of isotonic saline on the viral ACE2-receptor binding and SARS-CoV-2 replication [33,91,92] will be complemented by its effect on ciliary beating and the MCC for clearing virus [46,47,[69][70][71]. Overall, the complex interactions with NaCl, particularly those impacting with ACE2 and ENaC, suggest that a therapeutic strategy for recovering the balance between alveolar uid formation and reabsorption may contribute to the treatment for alveolar lung injury.…”

“…Table 3 summarizes a number of recommendations, based on the results from this analysis, for use of saline for nasal and/or respiratory hygiene at initial onset of common cold symptoms, which clinically overlap with COVID-19 upper respiratory symptoms. While isotonic seawater has a rinsing effect improving the MCC [[134]], the use of pure isotonic saline is rather proposed, because nasal spray compositions with more (buffering) ions such as seawater, or with surfactants, emulsi ers, and/or active substances may not necessarily lead to the desired effects, such as observed with pure saline on SARS-CoV-2 replication in vitro [33,93]; moreover, the addition of surfactants/emulsi ers may enhance bio-aerosol formation [31,39], while these products or active substances may inhibit the ciliary beating [85] or be ciliotoxic (e.g. polyvidone-iodine [134,[135]]).…”

“…The inhalation of isotonic saline solution signi cantly reduces (bio) aerosol release from the lungs" [13]. Only recently, it has been shown that saline inhibits replication of SARS-CoV-2 in vitro in Vero cells (see further point 3) [ [33]], while a study with nebulized neutral electrolyzed saline was found to reduce the qPCR positivity of the virus in 6 out of 10 subjects by day 4, in 80% by day 6 and in all of them by day 9 (for clinical results, see point 6) [ [34]]. Other studies of the effect of saline on bio-aerosols, listed in Table 1 [[35]-, [36], [37]], have generated similar results with other viruses or lung particles, con rming a reduction bio-aerosols.…”

“…NaCl is listed as an antimicrobial against coronaviruses MHV-2, MHV-N (mouse hepatitis viruses) and CCV (canine coronavirus), as these viruses lose infectivity after exposure to NaCl 0.23% [ [86]]. Moreover, a recent in vitro assessment of SARS-CoV-2 with saline (0.8-1.7% NaCl) showed a dose-dependent inhibition of viral replication in Vero CL-81 cells [33]. Inhibition of viral replication started from 0.6% onwards, increasing to 50% at 0.9% (isotonic) saline and reaching 100% at 1.5% hypertonic saline.…”