title: 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.affiliation: Centro Nacional de Microbiología and CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
authors.forename: Concepción
authors.initials: C
authors.lastname: Palomo
authors.affiliation: Centro Nacional de Microbiología and CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
authors.forename: Vicente
authors.initials: V
authors.lastname: Mas
authors.affiliation: Ablynx NV, Zwijnaarde, Belgium.
authors.forename: Laurent
authors.initials: L
authors.lastname: Detalle
authors.affiliation: Ablynx NV, Zwijnaarde, Belgium.
authors.forename: Erik
authors.initials: E
authors.lastname: Depla
authors.affiliation: Centro Nacional de Microbiología and CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
authors.forename: Olga
authors.initials: O
authors.lastname: Cano
authors.affiliation: Centro Nacional de Microbiología and CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
authors.forename: Mónica
authors.initials: M
authors.lastname: Vázquez
authors.affiliation: Ablynx NV, Zwijnaarde, Belgium.
authors.forename: Catelijne
authors.initials: C
authors.lastname: Stortelers
authors.affiliation: Centro Nacional de Microbiología and CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain jmelero@isciii.es.
authors.forename: José A
authors.initials: JA
authors.lastname: Melero
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D000914:Antibodies, Viral / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D000956:Antigens, Viral / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D002161:Camelids, New World; D045744:Cell Line, Tumor; D004847:Epithelial Cells / Q000821:virology; D000939:Epitopes / Q000737:chemistry / Q000276:immunology; D006801:Humans; D057131:Immune Evasion / Q000235:genetics; D007106:Immune Sera / Q000737:chemistry; D008958:Models, Molecular; D009154:Mutation; D009500:Neutralization Tests; D011485:Protein Binding; D017433:Protein Structure, Secondary; D018113:Respiratory Syncytial Virus, Human / Q000187:drug effects* / Q000235:genetics / Q000276:immunology; D061905:Single-Domain Antibodies / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D014760:Viral Fusion Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D000956:Antigens, Viral; D000939:Epitopes; D007106:Immune Sera; D061905:Single-Domain Antibodies; D014760:Viral Fusion Proteins