Mucin Colocalizes with Influenza Virus and Preserves Infectivity in Deposited Model Respiratory Droplets
Jin Pan, Nisha K. Duggal, Seema S. Lakdawala, Nicole C. Rockey, Linsey C. Marr
Abstract
The stability of influenza virus in respiratory particles varies with relative humidity (RH) and protein content. This study investigated the decay, or loss of infectivity, of influenza A virus (IAV) in 1-μL respiratory droplets deposited on a surface with varying concentrations of mucin, one of the most abundant proteins in respiratory mucus, and examined the localization of virions within droplets. IAV remained stable at 0.1% and 0.5% mucin in phosphate-buffered saline (PBS) over 4 h at 20%, 50%, and 80% RH, with a maximum decay of 1.2 log 10 /mL. In contrast, in pure PBS droplets, the virus decayed by at least 2.6 log 10 /mL after 4 h at 50% and 80% RH. Mucin’s protective effect was independent of its concentration, except at 80% RH after 4 h. Confocal microscopy of the particles revealed that at 20% and 50% RH, mucin led to thicker coffee rings and dendritic patterns where virions colocalized with mucin. At 80% RH, no morphological difference was observed between PBS-only and mucin-containing droplets, but virions still colocalized with mucin in the center of droplets with 0.5% mucin. Analysis by digital droplet PCR showed that mucin helped maintain virus integrity. To our knowledge, this is the first study to localize influenza virus in model respiratory droplets. The results suggest that mucin’s colocalization with virions in droplets may protect the virus from environmental stressors, enhancing its stability.