Multivalent Affinity Profiling: Direct Visualization of the Superselective Binding of Influenza Viruses

The influenza A virus
(IAV) interacts with the glycocalyx of host
cells through its surface proteins hemagglutinin (HA) and neuraminidase
(NA). Quantitative biophysical measurements of these interactions
may help to understand these interactions at the molecular level with
the long-term aim to predict influenza infectivity and answer other
biological questions. We developed a method, called multivalent affinity
profiling (MAP), to measure virus binding profiles on receptor density
gradients to determine the threshold receptor density, which is a
quantitative measure of virus avidity toward a receptor. Here, we
show that imaging of IAVs on receptor density gradients allows the
direct visualization and efficient assessment of their superselective
binding. We show how the multivalent binding of IAVs can be quantitatively
assessed using MAP if the receptor density gradients are prepared
around the threshold receptor density without crowding at the higher
densities. The threshold receptor density increases strongly with
increasing flow rate, showing that the superselective binding of IAV
is influenced by shear force. This method of visualization and quantitative
assessment of superselective binding allows not only comparative studies
of IAV–receptor interactions, but also more fundamental studies
of how superselectivity arises and is influenced by experimental conditions.