Biophysical Measurement of the Balance of Influenza A Hemagglutinin and Neuraminidase Activities [Molecular Bases of Disease]

January 13th, 2015 by Benton, D. J., Martin, S. R., Wharton, S. A., McCauley, J. W.

The interaction of Influenza A viruses with the cell surface is controlled by the two surface glycoproteins: hemagglutinin (HA) and neuraminidase (NA). These two glycoproteins have opposing activities, with the HA responsible for binding the host receptor, sialic acid, to allow infection and the NA responsible for cleaving the receptor to facilitate virus release. There have previously been several studies which have demonstrated that compatible levels of HA and NA activity are required in order for a virus to replicate efficiently. This is consequently of great interest for determining virus transmissibility. The concurrent role of these two proteins on receptor binding has never been directly measured. This paper demonstrates a novel biophysical approach based on biolayer interferometry (BLI) to measure the balance of the activities of these two proteins in real-time. This technique measures virus binding to and release from a surface coated in either the human-like receptor analogue α2,6-linked sialic acid or the avian-like receptor analogue α2,3-linked sialic acid, both in the presence and absence of NA inhibitors. BLI measurements are also carried out to determine the effect of altering HA receptor affinity and NA stalk length on receptor binding.