Structural Basis for Escape of Human Astrovirus from Antibody Neutralization: Broad Implications for Rational Vaccine Design.

TitleStructural Basis for Escape of Human Astrovirus from Antibody Neutralization: Broad Implications for Rational Vaccine Design.
Publication TypeJournal Article
Year of Publication2018
AuthorsBogdanoff, Walter A., Perez Edmundo I., López Tomás, Arias Carlos F., and DuBois Rebecca M.
JournalJ Virol
Volume92
Issue1
Date Published2018 01 01
ISSN1098-5514
KeywordsAntibodies, Monoclonal, Antibodies, Neutralizing, Antibodies, Viral, Capsid, Capsid Proteins, Drug Design, Epitopes, Humans, Mamastrovirus, Models, Molecular, Molecular Conformation, Mutation, Proline, Protein Binding, Sequence Analysis, DNA, Serine, Viral Vaccines
Abstract

Human astroviruses are recognized as a leading cause of viral diarrhea worldwide in children, immunocompromised patients, and the elderly. There are currently no vaccines available to prevent astrovirus infection; however, antibodies developed by healthy individuals during previous infection correlate with protection from reinfection, suggesting that an effective vaccine could be developed. In this study, we investigated the molecular mechanism by which several strains of human astrovirus serotype 2 (HAstV-2) are resistant to the potent HAstV-2-neutralizing monoclonal antibody PL-2 (MAb PL-2). Sequencing of the HAstV-2 capsid genes reveals mutations in the PL-2 epitope within the capsid's spike domain. To understand the molecular basis for resistance from MAb PL-2 neutralization, we determined the 1.35-Å-resolution crystal structure of the capsid spike from one of these HAstV-2 strains. Our structure reveals a dramatic conformational change in a loop within the PL-2 epitope due to a serine-to-proline mutation, locking the loop in a conformation that sterically blocks binding and neutralization by MAb PL-2. We show that mutation to serine permits loop flexibility and recovers MAb PL-2 binding. Importantly, we find that HAstV-2 capsid spike containing a serine in this loop is immunogenic and elicits antibodies that neutralize all HAstV-2 strains. Taken together, our results have broad implications for rational selection of vaccine strains that do not contain prolines in antigenic loops, so as to elicit antibodies against diverse loop conformations. Human astroviruses (HAstVs) infect nearly every person in the world during childhood and cause diarrhea, vomiting, and fever. In this study, we investigated how several strains of HAstV are resistant to a virus-neutralizing monoclonal antibody. We determined the crystal structure of the capsid protein spike domain from one of these HAstV strains and found that a single amino acid mutation induces a structural change in a loop that is responsible for antibody binding. Our findings reveal how viruses can escape antibody neutralization and provide insight for the rational design of vaccines to elicit diverse antibodies that provide broader protection from infection.

DOI10.1128/JVI.01546-17
Alternate JournalJ. Virol.
PubMed ID29070688
PubMed Central IDPMC5730766
Grant ListR25 GM058903 / GM / NIGMS NIH HHS / United States
T32 GM008646 / GM / NIGMS NIH HHS / United States