title: Development of Norwalk virus-specific monoclonal antibodies with therapeutic potential for the treatment of Norwalk virus gastroenteritis.
abstract: Passive immunoprophylaxis or immunotherapy with norovirus-neutralizing monoclonal antibodies (MAbs) could be a useful treatment for high-risk populations, including infants and young children, the elderly, and certain patients who are debilitated or immunocompromised. In order to obtain antinorovirus MAbs with therapeutic potential, we stimulated a strong adaptive immune response in chimpanzees to the prototype norovirus strain Norwalk virus (NV) (genogroup I.1). A combinatorial phage Fab display library derived from mRNA of the chimpanzees' bone marrow was prepared, and four distinct Fabs reactive with Norwalk recombinant virus-like particles (rVLPs) were recovered, with estimated binding affinities in the subnanomolar range. Mapping studies showed that the four Fabs recognized three different conformational epitopes in the protruding (P) domain of NV VP1, the major capsid protein. The epitope of one of the Fabs, G4, was further mapped to a specific site involving a key amino acid residue, Gly365. One additional specific Fab (F11) was recovered months later from immortalized memory B cells and partially characterized. The anti-NV Fabs were converted into full-length IgG (MAbs) with human γ1 heavy chain constant regions. The anti-NV MAbs were tested in the two available surrogate assays for Norwalk virus neutralization, which showed that the MAbs could block carbohydrate binding and inhibit hemagglutination by NV rVLP. By mixing a single MAb with live Norwalk virus prior to challenge, MAbs D8 and B7 neutralized the virus and prevented infection in a chimpanzee. Because chimpanzee immunoglobulins are virtually identical to human immunoglobulins, these chimpanzee anticapsid MAbs may have a clinical application.
authors.affiliation: Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA. zchen@niaid.nih.gov
authors.forename: Zhaochun
authors.initials: Z
authors.lastname: Chen
authors.forename: Stanislav V
authors.initials: SV
authors.lastname: Sosnovtsev
authors.forename: Karin
authors.initials: K
authors.lastname: Bok
authors.forename: Gabriel I
authors.initials: GI
authors.lastname: Parra
authors.forename: Michelle
authors.initials: M
authors.lastname: Makiya
authors.forename: Liane
authors.initials: L
authors.lastname: Agulto
authors.forename: Kim Y
authors.initials: KY
authors.lastname: Green
authors.forename: Robert H
authors.initials: RH
authors.lastname: Purcell
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000235:genetics / Q000302:isolation & purification / Q000627:therapeutic use*; D057134:Antibodies, Neutralizing / Q000235:genetics / Q000302:isolation & purification / Q000627:therapeutic use*; D000918:Antibody Specificity; D017250:Caliciviridae Infections / Q000276:immunology / Q000517:prevention & control / Q000628:therapy*; D018604:Epitope Mapping; D005759:Gastroenteritis / Q000276:immunology / Q000517:prevention & control / Q000628:therapy*; D006801:Humans; D007116:Immunization, Passive; D007140:Immunoglobulin Fab Fragments / Q000235:genetics / Q000302:isolation & purification / Q000627:therapeutic use; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009663:Norwalk virus / Q000276:immunology*; D002679:Pan troglodytes; D019151:Peptide Library; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D015678:Viral Structural Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D007140:Immunoglobulin Fab Fragments; D019151:Peptide Library; D015678:Viral Structural Proteins