A Computationally Designed Hemagglutinin Stem-Binding Protein Provides In Vivo Protection from Influenza Independent of a Host Immune Response.

Merika Treants Koday,Travis Nieusma,Hannah Kalinoski,Ashley Dagley,Aaron Chevalier,Peter S Lee,Lauren Carter,Donald F Smee,Andrew B Ward,Deborah Heydenburg Fuller,Michael Koday,Lance Stewart,Ian A Wilson,David Baker,Jorgen Nelson,George F Gao

doi:10.1371/journal.ppat.1005409

Abstract

Broadly neutralizing antibodies targeting a highly conserved region in the hemagglutinin (HA) stem protect against influenza infection. Here, we investigate the protective efficacy of a protein (HB36.6) computationally designed to bind with high affinity to the same region in the HA stem. We show that intranasal delivery of HB36.6 affords protection in mice lethally challenged with diverse strains of influenza independent of Fc-mediated effector functions or a host antiviral immune response. This designed protein prevents infection when given as a single dose of 6.0 mg/kg up to 48 hours before viral challenge and significantly reduces disease when administered as a daily therapeutic after challenge. A single dose of 10.0 mg/kg HB36.6 administered 1-day post-challenge resulted in substantially better protection than 10 doses of oseltamivir administered twice daily for 5 days. Thus, binding of HB36.6 to the influenza HA stem region alone, independent of a host response, is sufficient to reduce viral infection and replication in vivo. These studies demonstrate the potential of computationally designed binding proteins as a new class of antivirals for influenza.

Highlights

The influenza envelope glycoprotein hemagglutinin (HA) on the surface of the influenza virus consists of a highly variable globular head domain (HA1) and a more conserved stem domain (HA2/HA1) [1, 2]
A Computationally Designed Protein Protects against Influenza virus that protection is independent of the host immune response, demonstrating that an antiviral can disrupts influenza infection in vivo via direct binding to the HA stem
We made a combinatorial library of substitutions that were enriched across all subtype selections at 12 mutated positions and carried out three rounds of yeast display sorting against A/South Carolina/1/1918 (H1N1) HA, which converged on a variant with nine substitutions called HB36.6

Summary

Introduction

The influenza envelope glycoprotein hemagglutinin (HA) on the surface of the influenza virus consists of a highly variable globular head domain (HA1) and a more conserved stem domain (HA2/HA1) [1, 2]. Influenza viruses comprise two phylogenetic groups (Groups 1 and 2) consisting of 18 HA subtypes and numerous genetic variants or strains within each subtype. Neutralizing monoclonal antibodies (bnAbs) that bind the conserved HA stem can neutralize diverse influenza strains in vitro, suggesting that antivirals targeting the HA stem could provide similar widespread protection. Recent studies show that protection by HA-stem binding bnAbs is greatly enhanced through FcγR engagement in vivo [1, 9]. While antibody binding to the fusogenic region is sufficient for in vitro neutralization of the virus, Fc-FcγR interaction and activation of antibodydependent cellular cytotoxicity (ADCC) are critical for in vivo efficacy of stem-binding bnAbs [1, 10]

Methods

Results

Discussion

Conclusion