title: Humanized monoclonal antibodies derived from chimpanzee Fabs protect against Japanese encephalitis virus in vitro and in vivo.
abstract: Japanese encephalitis virus (JEV)-specific Fab antibodies were recovered by repertoire cloning from chimpanzees initially immunized with inactivated JE-VAX and then boosted with attenuated JEV SA14-14-2. From a panel of 11 Fabs recovered by different panning strategies, three highly potent neutralizing antibodies, termed Fabs A3, B2, and E3, which recognized spatially separated regions on the virion, were identified. These antibodies reacted with epitopes in different domains: the major determinant for Fab A3 was Lys(179) (domain I), that for Fab B2 was Ile(126) (domain II), and that for Fab E3 was Gly(302) (domain III) in the envelope protein, suggesting that these antibodies neutralize the virus by different mechanisms. Potent neutralizing antibodies reacted with a low number of binding sites available on the virion. These three Fabs and derived humanized monoclonal antibodies (MAbs) exhibited high neutralizing activities against a broad spectrum of JEV genotype strains. Demonstration of antibody-mediated protection of JEV infection in vivo is provided using the mouse encephalitis model. MAb B2 was most potent, with a 50% protective dose (ED(50)) of 0.84 microg, followed by MAb A3 (ED(50) of 5.8 microg) and then MAb E3 (ED(50) of 24.7 microg) for a 4-week-old mouse. Administration of 200 microg/mouse of MAb B2 1 day after otherwise lethal JEV infection protected 50% of mice and significantly prolonged the average survival time compared to that of mice in the unprotected group, suggesting a therapeutic potential for use of MAb B2 in humans.
authors.affiliation: Molecular Viral Biology Section, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892, USA. agoncalvez@niaid.nih.gov
authors.forename: Ana P
authors.initials: AP
authors.lastname: Goncalvez
authors.forename: Cheng-Hsin
authors.initials: CH
authors.lastname: Chien
authors.forename: Kamolchanok
authors.initials: K
authors.lastname: Tubthong
authors.forename: Inna
authors.initials: I
authors.lastname: Gorshkova
authors.forename: Carrie
authors.initials: C
authors.lastname: Roll
authors.forename: Olivia
authors.initials: O
authors.lastname: Donau
authors.forename: Peter
authors.initials: P
authors.lastname: Schuck
authors.forename: Sutee
authors.initials: S
authors.lastname: Yoksan
authors.forename: Sy-Dar
authors.initials: SD
authors.lastname: Wang
authors.forename: Robert H
authors.initials: RH
authors.lastname: Purcell
authors.forename: Ching-Juh
authors.initials: CJ
authors.lastname: Lai
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification*; D000914:Antibodies, Viral / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification*; D002460:Cell Line; D004664:Encephalitis Virus, Japanese / Q000276:immunology*; D004672:Encephalitis, Japanese / Q000517:prevention & control*; D018985:Epitopes, B-Lymphocyte / Q000276:immunology; D015686:Gene Products, env / Q000276:immunology; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D002679:Pan troglodytes; D011485:Protein Binding; D016415:Sequence Alignment; D016019:Survival Analysis
chemical_list: D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D018985:Epitopes, B-Lymphocyte; D015686:Gene Products, env; D007140:Immunoglobulin Fab Fragments