Rabies virus is a neurotropic virus that causes fatal, but, a preventable disease in mammals. Administration of rabies immunoglobulin (RIG) is essential for the post-exposure of the prophylaxis to prevent the disease. However, replacement of polyclonal RIGs with alternative monoclonal antibodies (MAbs) that are capable of neutralizing rabies virus has been recommended.,Here, we have investigated the transient expression of the full-size human MAb against rabies virus glycoprotein; the MAb SO57 in the tobacco plants using vacuum agro-infiltration. Previously, stably transformed plants expressing the MAb have been reported.,In this study three vectors carrying the codon-optimized genes for the heavy or light chain and p19 silencing-suppressor were constructed. These vectors were co-infiltrated into Nicotiana tabacum leaves and the transgenes were expressed.,Dot blot, Western blotting, ELISA, and in vitro neutralization assays of the plant extracts showed that the human MAb could assemble in tobacco leaves and was able to neutralize rabies virus.,This study is the first report of transient expression of human MAb SO57 gene in tobacco plant within a few days after vacuum agro-infiltration.