Methods: The VIS410 epitope was predicted using experimental data and in silico antibody docking methods. Sequences of influenza HA from various subtypes were collected from GenBank and the Global Initiative on Sharing Avian Influenza Data (GISAID). A bioinformatics analysis was performed to analyze the composition and evolution of amino acids found at VIS410 epitope positions in HA. ELISA was used to assay VIS410 for binding to HAs that differ in epitope amino acids, and virus neutralization assays were used to assess VIS410’s ability to neutralize influenza viruses with epitope variation.
Results: VIS410 binds to an epitope that is highly conserved in group 1 and group 2 HAs and an analysis of over 44,000 sequences shows that the natural variability in these residues is limited within each group. Polymorphisms at epitope positions that occur at >1% were identified and interrogated in the context of existing strains harboring these mutations. VIS410 neutralized influenza virus strains that together covered > 97% of the observed positional variability at each epitope position in H1 strains and > 93% of the positional variability at each epitope position in H3 strains. Furthermore, when combined with ELISA binding data, VIS410 was empirically shown to bind to epitopes with amino acid content found in > 99% of HA sequences.
Conclusion: VIS410 displays broad binding and neutralization and is tolerant to observed polymorphisms in its epitope including newly emerging mutations found in currently circulating strains.
A. Wollacott, Visterra, Inc.: Employee and Shareholder , Salary
K. Szretter, Visterra, Inc.: Employee and Shareholder , Salary
G. Babcock, Visterra, Inc.: Employee and Shareholder , Salary