Interplay between respiratory viruses and cilia in the airways

Abstract

The airway epithelium is the first point of contact for inhaled pathogens. The role of epithelial cells in clearance, infection and colonisation of bacteria is established. The interactions of respiratory viruses and cilia is less understood, but viruses are known to target ciliated epithelial cells for entry, replication and dissemination. Furthermore, some respiratory viruses impair and/or enhance ciliary activity. This review examines what is known about the interactions between cilia and viral infection and how respiratory viruses effect cilia function with subsequent consequences for human health. We discuss the models which can be used to investigate the relationship between respiratory viruses and the host airway.

FIGURE 1

Respiratory cilia beat in a coordinated sweeping pattern, a) which moves mucus and debris, including pathogens towards the oropharynx for swallowing or expectorating. b) The cilia beat forwards in a metachronal wave to propel mucus forward, followed by a recovery stroke. c) Labelled diagram of a normal ciliary axonemal ultrastructure and transmission electron micrographs of normal ciliary ultrastructure in transverse and longitudinal sections (labelled). The white scale bar in longitudinal section image: 500 nm. A normal ciliary axoneme is approximately 200 nm in diameter.

FIGURE 2

A triggering event (e.g. viral infection), or genetic condition affecting mucociliary clearance (e.g. primary ciliary dyskinesis), can lead to a persistent and progressive “vortex” of processes including inflammation and airway damage. Adapted from Flume et al. [33].

FIGURE 3

Respiratory viruses have differing impacts on the ciliated airway epithelia, ranging from mild deciliation (rhinovirus) to significant damage and loss of ciliated cells (severe acute respiratory syndrome (SARS) and influenza). This spectrum of viral effects on ciliated airway epithelia underscores the importance of understanding the specific mechanisms by which different respiratory pathogens interact with and potentially disrupt the mucociliary clearance system. MERS: Middle East respiratory syndrome; RSV: respiratory syncytial virus.