| West Nile virus has spread rapidly across the United States, and there is currently no approved human vaccine or therapy to prevent or treat disease. Passive immunization with antibodies against the envelope protein represents a promising means to provide short term prophylaxis and treatment for West Nile virus infection. The objective of this study was therefore to identify and characterize recombinant human monoclonal antibodies that can be used in the treatment of West Nile virus infection.; Using a phage display screen, we identified a panel of human single chain variable region antibody fragments that bind a highly purified, recombinant form of the envelope protein of West Nile virus. We characterized the ability of these antibodies to bind the envelope protein, and their ability to neutralize West Nile virus in vitro. Because the scFvs did not protect mice in vivo, we fused an Fc domain to selected scFvs to create bivalent scFv-Fc molecules. We then examined the ability of these antibodies to prevent lethal murine West Nile virus infection, as well as their ability to cross-neutralize related flaviviruses in vitro. Several of the antibodies identified in this study were effective as both prophylaxis and treatment for lethal West Nile virus infection.; We next examined the mechanism by which these antibodies are protective, and began to map the protective epitopes bound by these antibodies. Although scFv-Fcs did not prevent viremia or limit dissemination into the central nervous system, mice that survived infection appeared healthy and did not have lasting or significant morbidity. Finally, we used a yeast display system to map the epitopes recognized by the scFv-Fcs. All of the antibody molecules bound to a Domain I/II fusion of the West Nile virus envelope protein, and potentially recognize unique protective epitopes.; This study is the first description of human monoclonal antibodies against West Nile virus. These recombinant human antibodies are important potential candidates for immunoprophylaxis and therapy of flavivirus infections, and provide us with insight into the virulence and pathogenesis of West Nile virus infection. |
