Superdiffusive Motion of Influenza A Viruses on Surfaces

Viral infections depend on the ability of the invading pathogen to move through the extracellular environment to reach host cells. In the case of Influenza A virus (IAV), this means traversing a thick layer of mucus above airway epithelial cells. The glycosylated biopolymers (mucins) that make up the mucus layer present glycans that bind to receptors on the virus envelop and can be cleaved by enzymes also on the virus envelop. It was recently observed that IAV can move in a persistent and directed manner through the spatial organization of binding and cleaving activity on the viral envelop — employing a 'burnt-bridge' Brownian ratchet-like mechanism. A mean squared displacement (MSD) analysis of IAV trajectories on glycan-coated coverslips reveals superdiffusive motion on relevant time scales. Here we present a stochastic model that captures the fundamental mechanism of IAV motion on surfaces. The model describes the rectification of the stochastic binding, unbinding and cleaving events into directed motion that agrees with experimental observations. The model also suggests a concentration gradient sensing strategy that may be exploited by IAV to navigate through the mucus layer.