Researchers established a simple and effective method for DNA immunization against Japanese encephalitis virus (JEV) infection with plasmids encoding the viral PrM and E proteins and colloidal gold. After being inoculated twice, BALB/c mice were found to resist challenge with 100,000 times the 50% lethal dose (LD(50)) of JEV (Beijing-1 strain) even when immunized with a relatively small dose of 0.5 micro g of plasmid DNA (Zhao et al., 2003).
