Treatment of mice with human monoclonal antibody 24 hours after lethal aerosol challenge with virulent Venezuelan equine encephalitis virus prevents disease but not infection

We recently described a Venezuelan equine encephalitis virus (VEEV)-specific human monoclonal antibody (MAb), F5 nIgG, that recognizes a new neutralization epitope on the VEEV E2 envelope glycoprotein. In this study, we investigated the ability of F5 nIgG given prophylactically or therapeutically to protect mice from subcutaneous or aerosolized VEEV infection. F5 nIgG had potent ability to protect mice from infection by either route when administered 24 h before exposure; however, mice treated 24 h after aerosol exposure developed central nervous system infections but exhibited no clinical signs of disease. Infectious virus, viral antigen and RNA were detected in brains of both treated and untreated mice 2–6 days after aerosol exposure but were cleared from the brains of treated animals by 14–28 days after infection. This fully human MAb could be useful for prophylaxis or immediate therapy for individuals exposed to VEEV accidentally in the laboratory or during a deliberate release.