Human rhinovirus capsid dynamics is controlled by canyon flexibility

Area of Science:

• Virology
• Biochemistry
• Structural Biology

Background:

• The human rhinovirus (HRV) capsid's dynamic nature, or "breathing," is crucial for its lifecycle and a target for antiviral development.
• Understanding how antiviral compounds and genetic mutations affect capsid stability is essential for designing effective therapies.

Purpose of the Study:

• To investigate the dynamic properties of the HRV capsid under various conditions, including the presence of antiviral compounds, antibodies, and specific mutations.
• To correlate changes in capsid mobility with antiviral efficacy and mechanism of action.

Main Methods:

• Quantitative enzyme accessibility experiments utilizing nano liquid chromatography electrospray mass spectrometry (nLC-ESI-MS).
• Limited proteolysis and isotope labeling techniques were employed to probe capsid structure and dynamics.
• Analysis of site-directed mutations within the drug-binding cavity and antibody binding sites.

Main Results:

• The antiviral compounds WIN 52084 and pleconaril stabilized the HRV capsid against proteolytic digestion.
• Dansylaziridine destabilized the capsid, indicating varied effects of antivirals.
• Mutations in the drug-binding cavity mimicked the stabilizing effect of WIN 52084 and pleconaril.
• Antibodies binding to the NIm-IA antigenic site also conferred protection against proteolytic cleavage.

Conclusions:

• Quantifying capsid "breathing" provides a method to compare antiviral modes of action and efficacy.
• Hydrophobic antiviral agents, specific antibodies, and mutations in the canyon region effectively block viral breathing.
• Mobility within the canyon region is a critical determinant of HRV capsid breathing and stability.