A recombinant humanized monoclonal antibody completely protects mice against lethal challenge with Venezuelan equine encephalitis virus.

A recombinant humanized antibody to Venezuelan equine encephalitis virus (VEEV) was constructed in a monocistronic adenoviral expression vector with a foot-and-mouth-disease virus-derived 2A self-cleavage oligopeptide inserted between the antibody heavy and light chains. After expression in mammalian cells, the heavy and light chains of the humanized antibody (hu1A4A1IgG1-2A) were completely cleaved and properly dimerized. The purified hu1A4A1IgG1-2A retained VEEV binding affinity and neutralizing activity similar to its parental murine antibody. The half-life of hu1A4A1IgG1-2A in mice was approximately 2 days. Passive immunization of hu1A4A1IgG1-2A in mice (50 microg/mouse) 24 h before or after virulent VEEV challenge provided complete protection, indicating that hu1A4A1IgG1-2A has potent prophylactic and therapeutic effects against VEEV infection.