Humanized monoclonal antibodies derived from chimpanzee Fabs protect against Japanese encephalitis virus in vitro and in vivo.
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.
Goncalvez
Ana P
AP
Molecular Viral Biology Section, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892, USA. agoncalvez@niaid.nih.gov
Chien
Cheng-Hsin
CH
Tubthong
Kamolchanok
K
Gorshkova
Inna
I
Roll
Carrie
C
Donau
Olivia
O
Schuck
Peter
P
Yoksan
Sutee
S
Wang
Sy-Dar
SD
Purcell
Robert H
RH
Lai
Ching-Juh
CJ
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
D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D018985:Epitopes, B-Lymphocyte; D015686:Gene Products, env; D007140:Immunoglobulin Fab Fragments