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

Abstract

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.

Toward Chemotactic Supramolecular Nanoparticles: From Autonomous Surface Motion Following Specific Chemical Gradients to Multivalency-Controlled Disassembly

“…The identification of a threshold receptor density as a function of multivalent interactions has been recently estimated by a sophisticated image postprocessing approach . However, perhaps the main advantage of these self-assembling oligomers is that their modular structure enables the fine-tuning of hydrophobic/hydrophilic groups in order to control the NP disassembly and the release of the guests during the NP chemotaxis.…”

“…The results show that the NP tends to establish a higher number of multivalent interactions with the surface groups while moving toward denser surface regions, as recently demonstrated with fluorescent microscopy experiments in other multivalent binding systems. 19 Such enhancement of the multivalent binding with the surface leads to an increased exposure of the hydrophobic parts of the NP oligomers to the solvent, thereby entailing an increase of the SASA of the assembly (ΔSASA). The ΔSASA increases even further as a consequence of NP exfoliation, as well illustrated in Figure 5b.…”

“…The identification of a threshold receptor density as a function of multivalent interactions has been recently estimated by a sophisticated image postprocessing approach. 19 However, perhaps the main advantage of these self-assembling oligomers is that their modular structure enables the finetuning of hydrophobic/hydrophilic groups in order to control the NP disassembly and the release of the guests during the NP chemotaxis. While the ΔE ass /ΔE bind ratio is critical to control the chemotactic responsive behavior of the NPs, our simulations highlight how such a control can be achieved by for example, modulating the multivalent interactions between the NP and the surface, or even by changing the number of −1e charged groups on the oligomers (namely, changing the ΔE ass /ΔE bind by acting on the ΔE bind ).…”

“…Notable examples of synthetic supramolecular structures, such as fibers, vesicles, or tubes have demonstrated to have excellent stimuli responsive properties while autonomously moving. − Also responsive nanoparticles (NPs) have shown surface binding capability combined with tailored releasing of encapsulated guests. − To predict and engineer the selective binding on surfaces, both monovalent and multivalent affinities are exploited. To cite just a few examples, Liao et al studied the correlation between monovalent labeling schemes on a gold NP and its diffusion rate on supported lipid bilayer membranes, while Overseem and co-workers investigated multivalent binding profiles of influenza virus on surfaces with receptor density gradients . However, despite notable advances in surface modification and control are emerging thanks to cutting-edge techniques, technical experimental limitations still prevent the rational design of chemotactic functional materials.…”

“…To cite just a few examples, Liao et al studied the correlation between monovalent labeling schemes on a gold NP and its diffusion rate on supported lipid bilayer membranes, 18 while Overseem and co-workers investigated multivalent binding profiles of influenza virus on surfaces with receptor density gradients. 19 However, despite notable advances in surface modification and control are emerging thanks to cutting-edge techniques, 20 technical experimental limitations still prevent the rational design of chemotactic functional materials. First, tracking and observing the movement of soft, tiny NPs on surfaces at sufficiently small spatiotemporal scales is a hard challenge.…”