Viscoelastic Response of Commercial Mucin to HIV Psuedotyped Virus

Mucin is a heavily glycosylated protein that makes up the mucus gel which serves as a protective barrier against pathogens like viruses. Mucins are prone to self-aggregation which imparts a viscoelastic (fluid-like and solid-like) characteristic to the mucus gel. However little is known about how the presence of viruses change the flow properties of mucin. Replication-deficient HIV viruses pseudotyped with either gp120 or vesicular stomatitis virus (VSV-G) envelope proteins were used as model viruses. Commercially available Porcine gastric mucin-type II (PGM-II) and porcine gastric mucin type III (PGM-III) in the filtered ( free mucin) and unfiltered ( having mucin-mucin interactions) states were used as model mucins. DLS was used to determine the landscape of the sizes of the diffusing species (mucin, virus, or virus-mucin species). Rheology was used to determine change in the inter-mucin interaction and friction. Axisymmetric drop shape analysis was used to determine the changes to the mucin surface tension. Preliminary results suggest that the average intensity of PGM-II and PGM-III, in the filtered state, are lowered and the hydrodynamic diameter decreases with both pseudotyped viruses. Subsequent rheology studies show a lowered elastic and frictional character when either VSV-G or gp120 pseudotyped viruses are present. The unfiltered state of mucin shows no significant changes in DLS measurements but increased elastic and frictional characteristics are observed at lower oscillatory frequencies in rheology studies. Our data demonstrates that viruses change solution behavior of mucin both in the singular and aggregated states and thus may alter the viscoelastic characteristics of the mucus gel.