Trivalency of a Nanobody Specific for the Human Respiratory Syncytial Virus Fusion Glycoprotein Drastically Enhances Virus Neutralization and Impacts Escape Mutant Selection.

Abstract

ALX-0171 is a trivalent Nanobody derived from monovalent Nb017 that binds to antigenic site II of the human respiratory syncytial virus (hRSV) fusion (F) glycoprotein. ALX-0171 is about 6,000 to 10,000 times more potent than Nb017 in neutralization tests with strains of hRSV antigenic groups A and B. To explore the effect of this enhanced neutralization on escape mutant selection, viruses resistant to either ALX-0171 or Nb017 were isolated after serial passage of the hRSV Long strain in the presence of suboptimal concentrations of the respective Nanobodies. Resistant viruses emerged notably faster with Nb017 than with ALX-0171 and in both cases contained amino acid changes in antigenic site II of hRSV F. Detailed binding and neutralization analyses of these escape mutants as well as previously described mutants resistant to certain monoclonal antibodies (MAbs) offered a comprehensive description of site II mutations which are relevant for neutralization by MAbs and Nanobodies. Notably, ALX-0171 showed a sizeable neutralization potency with most escape mutants, even with some of those selected with the Nanobody, and these findings make ALX-0171 an attractive antiviral for treatment of hRSV infections.

• Authors: Concepción Palomo, Vicente Mas, Laurent Detalle, Erik Depla, Olga Cano, Mónica Vázquez, Catelijne Stortelers, José A Melero
• Journal: Antimicrobial agents and chemotherapy (Antimicrob Agents Chemother) Vol. 60 Issue 11 Pg. 6498-6509 (11 2016) ISSN: 1098-6596 [Electronic] United States
• PMID: 27550346 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Chemical References

• Antibodies, Monoclonal
• Antibodies, Viral
• Antigens, Viral
• Epitopes
• Immune Sera
• Single-Domain Antibodies
• Viral Fusion Proteins

Topics

• Animals
• Antibodies, Monoclonal (chemistry, isolation & purification, pharmacology)
• Antibodies, Viral (chemistry, isolation & purification, pharmacology)
• Antigens, Viral (chemistry, genetics, immunology)
• Camelids, New World
• Cell Line, Tumor
• Epithelial Cells (virology)
• Epitopes (chemistry, immunology)
• Humans
• Immune Evasion (genetics)
• Immune Sera (chemistry)
• Models, Molecular
• Mutation
• Neutralization Tests
• Protein Binding
• Protein Structure, Secondary
• Respiratory Syncytial Virus, Human (drug effects, genetics, immunology)
• Single-Domain Antibodies (chemistry, isolation & purification, pharmacology)
• Viral Fusion Proteins (antagonists & inhibitors, chemistry, genetics, immunology)