Mucin Protects Influenza a Virus from Decay in Evaporating Droplets
JIN PAN, Nisha Duggal, Seema Lakdawala, Nicole C. Rockey, Linsey Marr, Virginia Tech
Abstract Number: 147
Working Group: Health-Related Aerosols
Abstract
The stability of influenza virus in respiratory particles is a function of relative humidity (RH), and this relationship appears to depend on protein content, which accounts for 20-50% of dry weight of the particles. The objective of this research was to investigate the stability of influenza A virus in evaporating 1-μL respiratory droplets at different concentrations of mucin, the most abundant protein in respiratory fluids. The virus remained relatively stable at mucin concentrations of both 0.1% and 0.5% in droplets of phosphate-buffered saline (PBS) over the 4-hour duration of the experiment at 20%, 50%, and 80% RH, with a maximum decay of 1.5 log10, whereas the virus decayed by at least 3 log10 to the detection limit in pure PBS droplets after 4 hours at 50% and 80% RH. The protective effect was slightly stronger with 0.5% mucin than with 0.1% mucin. We further examined droplet morphology and localization of fluorescently labeled virions in evaporating droplets at various RH through confocal microscopy. Confocal images suggested that at 20% and 50% RH, the addition of mucin promoted the formation of feather-like, dendritic crystals, around which virions were co-localized with mucin. In the absence of mucin, isolated and square crystals formed. Virions were either in direct contact with the isolated crystals or scattered on the substrate surface. We observed that 0.5% mucin mitigated the coffee-ring effect and thus homogenized the distribution of virions in evaporating droplets. At 80% RH, there was no morphological difference between virus-laden droplets with and without mucin, but virions were still co-localized with mucin. These findings suggest that the co-localization of mucin and virions in evaporating droplets may reduce the exposure of virions to high concentrations of salts near salt crystals and other environmental stressors near the coffee ring in respiratory droplets, thereby maintaining virus stability.