Gene immunization against tick-borne encephalitis virus

The genes for major glycoprotein antigens E and NS1 of the tick-borne encephalitis virus (TBEV) were recloned in an eukaryotic expression vector pSVK3. The resulting pSVK3-ENS1 plasmid was characterized by sequencing and restriction enzyme analysis. To test the protective effect of gene immunization, BALB/c mice were immunized with 80-100 mu g of purified pSVK3-ENS1 DNA five times and injected with 100 LD50 of the TBEV Sof'in strain one week after the last immunization. Immunized mice remained healthy for the observation period, while all control mice manifested the pathology and 42.9% of them died.