Differentiating Antibody Neutralisation Mechanisms using a Single Virus-Assay

Abstract

Neutralizing antibodies to influenza mostly target the viral envelope glycoprotein hemagglutinin, critical for viral entry and fusion. Antigens recognizing the globular head of hemagglutinin are thought to inhibit virus attachment and antigens against the stalk region are thought to inhibit fusion. We report the development of a microfluidic single-virus fusion assay that utilizes both reconstituted receptors and DNA-lipid tethering to clearly differentiate the antibody inhibition of virus attachment versus fusion. As expected, antibodies to the receptor-binding domain inhibited attachment, but, antibodies against the fusion stalk could inhibit attachment and fusion. The relative potencies of neutralizing attachment versus fusion are trivially predictable from the antibody binding site and, combined with analysis of fusion kinetics under antibody inhibition, reveals further insight into the mechanism of neutralization by different antibodies. The information gained from this assay can be used to help guide antibody and vaccine optimization strategies.