Mucin Transiently Sustains Coronavirus Infectivity through Heterogenous Changes in Phase Morphology of Evaporating Aerosol

Abstract

Respiratory pathogens can be spread though the transmission of aerosolised expiratory secretions in the form of droplets or particulates. Understanding the fundamental aerosol parameters that govern how such pathogens survive whilst airborne is essential to understanding and developing methods of restricting their dissemination. Pathogen viability measurements made using Controlled Electrodynamic Levitation and Extraction of Bioaerosol onto Substrate (CELEBS) in tandem with a comparative kinetics electrodynamic balance (CKEDB) measurements allow for a direct comparison between viral viability and evaporation kinetics of the aerosol with a time resolution of seconds. Here, we report the airborne survival of mouse hepatitis virus (MHV) and determine a comparable loss of infectivity in the aerosol phase to our previous observations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Through the addition of clinically relevant concentrations of mucin to the bioaerosol, there is a transient mitigation of the loss of viral infectivity at 40% RH. Increased concentrations of mucin promoted heterogenous phase change during aerosol evaporation, characterised as the formation of inclusions within the host droplet. This research demonstrates the role of mucus in the aerosol phase and its influence on short-term airborne viral stability.

Physicochemical characterization of porcine respiratory aerosol and considerations for future aerovirology

“…From the measured ion mass concentration and protein concentration, the volume fraction of protein was also calculated (Table 1 ). The organic contribution was modeled as both BSA and PGM, as both have been used as analogs for respiratory proteins in prior studies ( 9 , 10 , 12 , 13 , 32 ) (Tables S2 and S3 ). A comprehensive discussion of the ZSR fitting procedure is described in Section S2 .…”

“…After nebulization, some intermediate storage system is required for the particles to reach equilibrium with some controlled environment. In the case of particle levitation studies which investigate physicochemical properties of a select number of particles, that controlled environment is a sealed chamber in which the humidity and temperature can be altered and maintained ( 13 , 14 ). For studies which investigate ensembles of particles, a rotating storage chamber is a common choice both to provide a controlled environment and to also minimize particle losses due to gravitational settling ( 2 , 15–18 ).…”

“…Research is accumulating to understand better the composition and morphology of respiratory aerosols, which will be useful to explain virus viability in aerovirology studies. Recently, work has shown that simulated respiratory fluid (SRF), including simple organic/inorganic solutions and growth media, exhibits semisolid organic phases upon dehydration ( 9 , 12 , 13 , 19 ). Numerous studies also confirm the crystallization of SRF (efflorescence) either through hygroscopicity measurements or micrograph analysis ( 9 , 10 , 12 , 14 , 18 , 20 , 21 ), and some provided evidence that effloresced salts were less effective at inactivating viruses than concentrated aqueous salts ( 17 ).…”

Toward Standardized Aerovirology: A Critical Review of Existing Results and Methodologies

“…85−88 Chamber-style setups have been favored for experiments which are investigating decay rates or half-lives of viruses, as historically, half-lives have been measured on the order of hours. 24,26,[29][30][31][32][33][34][35]38,39,41,47,53 Recently, EDT techniques (e.g., controlled electrodynamic levitation and extraction onto a substrate, CELEBS) 51,52,55,58 have been implemented for aerovirology and employ the strengths of both FTS and chamber systems, as they can store particles indefinitely and also have very high sampling resolution due to the fixed pathlength of the particles. Practical limitations on the ability to fully seal systems in aerovirology often lead to design philosophies that allow the chambers, and often the entire experimental apparatus, to be small enough to fit entirely within a laminar flow cabinet.…”

“…Alternatively, once the suspension is diluted below the 50% CPE level, the most probable number (MPN) of viables viruses can be calculated using Poisson statistics. 51,52,55,58,96 Regardless of how the virus viability is measured, it is important that the assay type remains consistent throughout an experiment and that both the initial virus concentration prior to experimentation and the concentration after treatment are quantified in the same way, including the use of the same cell line and culture medium.…”