ORCID Profile
0000-0003-4612-3973
Current Organisation
EPFL/ Laboratory of atmospheric processes and their impacts
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Publisher: American Society for Microbiology
Date: 24-10-2023
Abstract: Multiple respiratory viruses, including influenza A virus (IAV), can be transmitted via expiratory aerosol particles, and aerosol pH was recently identified as a major factor influencing airborne virus infectivity. Indoors, small exhaled aerosols undergo rapid acidification to pH ~4. IAV is known to be sensitive to mildly acidic conditions encountered within host endosomes however, it is unknown whether the same mechanisms could mediate viral inactivation within the more acidic aerosol micro-environment. Here, we identified that transient exposure to pH 4 caused IAV inactivation by a two-stage process, with an initial sharp decline in infectious titers mainly attributed to premature attainment of the post-fusion conformation of viral protein haemagglutinin (HA). Protein changes were observed by hydrogen-deuterium exchange coupled to mass spectrometry (HDX-MS) as early as 10 s post-exposure to acidic conditions. Our HDX-MS data are in agreement with other more labor-intensive structural analysis techniques, such as X-ray crystallography, highlighting the ease and usefulness of whole-virus HDX-MS for multiplexed protein analyses, even within enveloped viruses such as IAV. Additionally, virion integrity was partially but irreversibly affected by acidic conditions, with a progressive unfolding of the internal matrix protein 1 (M1) that aligned with a more gradual decline in viral infectivity with time. In contrast, no acid-mediated changes to the genome or lipid envelope were detected. Improved understanding of respiratory virus fate within exhaled aerosols constitutes a global public health priority, and information gained here could aid the development of novel strategies to control the airborne persistence of seasonal and/or pandemic influenza in the future. It is well established that COVID-19, influenza, and many other respiratory diseases can be transmitted by the inhalation of aerosolized viruses. Many studies have shown that the survival time of these airborne viruses is limited, but it remains an open question as to what drives their infectivity loss. Here, we address this question for influenza A virus by investigating structural protein changes incurred by the virus under conditions relevant to respiratory aerosol particles. From prior work, we know that expelled aerosols can become highly acidic due to equilibration with indoor room air, and our results indicate that two viral proteins are affected by these acidic conditions at multiple sites, leading to virus inactivation. Our findings suggest that the development of air treatments to quicken the speed of aerosol acidification would be a major strategy to control infectious bioburdens in the air.
Publisher: Cold Spring Harbor Laboratory
Date: 14-03-2022
DOI: 10.1101/2022.03.14.22272134
Abstract: Enveloped viruses are prone to inactivation when exposed to strong acidity levels characteristic of atmospheric aerosol. Yet, the acidity of expiratory aerosol particles and its effect on airborne virus persistence has not been examined. Here, we combine pH-dependent inactivation rates of influenza A virus and SARS-CoV-2 with microphysical properties of respiratory fluids under indoor conditions using a biophysical aerosol model. We find that particles exhaled into indoor air become mildly acidic (pH ≈ 4), rapidly inactivating influenza A virus within minutes, whereas SARS-CoV-2 requires days. If indoor air is enriched with non-hazardous levels of nitric acid, aerosol pH drops by up to 2 units, decreasing 99%-inactivation times for both viruses in small aerosol particles to below 30 seconds.Conversely, unintentional removal of volatile acids from indoor air by filtration may elevate pH and prolong airborne virus persistence. The overlooked role of aerosol pH has profound implications for virus transmission and mitigation strategies. Respiratory viruses are sensitive to aerosol pH, an unidentified factor in the mitigation of airborne virus transmission
Publisher: Proceedings of the National Academy of Sciences
Date: 29-08-2022
Publisher: American Chemical Society (ACS)
Date: 20-12-2022
Location: Switzerland
Location: France
Location: Switzerland
No related grants have been discovered for Kalliopi Violaki.