• Vaccine Name: TBEV Virus Like Particle Vaccine
• Target Pathogen: Tick-borne Encephalitis Virus (TBEV)
• Target Disease: Tick-borne Encephalitis
• Type: Virus Particle Vaccine
• Status: Research
• Host Species for Licensed Use: None
• Host Species as Laboratory Animal Model: Mouse
• Antigen: Atructural (Core/prM/E) and non-structural (NS2B/NS3Pro) proteins of TBEV (Tang et al., 2023)
• Preparation: Expi293 cells were diluted to a density of 1.5 × 106 cells/mL before transfection with pcDNA3.1-NS2B/NS3Pro and pcDNA3.1-C/prM/E at a ratio of 1:2, then the cells were cultivated at 37°C in an atmosphere of 5% CO2, with agitation at 150 rpm. For the production of VLPs, the plasmids (480 μg) were added to polyethylenimine hydrochloride (1,350 μg; Polysciences) in 10 mL of Expi293 medium and incubated for 10 min, the mixture was then added to 470 mL of cell solution. The transfected cells were harvested at 4 days post-transfection and the supernatant was collected by two successive centrifugation steps at 400 ×g for 10 min at 4°C, then 10,000 ×g for 10 min at 4°C. The proteins in the supernatant were precipitated using 8% (wt/vol) polyethylene glycol 8000 and incubated overnight at 4°C. (Tang et al., 2023)
• Immunization Route: Intramuscular injection (i.m.)
• Description: Virus-like particle-based vaccine co-expressing the structural (Core/prM/E) and non-structural (NS2B/NS3Pro) proteins of TBEV confers complete protection against TBEV in mice. (Tang et al., 2023)

Mouse Response

• Vaccination Protocol: Eight-week-old male C57BL/6 mice were used for the immunization and viral neutralization experiments. The mice (n=5 per group) were immunized by twice intramuscular injections with PBS or 10 μg of VLPs.Six to eight-week-old male IFNAR-/- mice were used for immunization and challenge experiments. The mice (n=10 per group) were immunized with PBS or 10 μg of VLPs. (Tang et al., 2023)
• Immune Response: The results of ELISA demonstrated that vaccination with the VLPs stimulated a high total serum IgG response, and the prime antibody response increased by 2.5-fold following boost immunization (Fig. 2C). Additionally, the antibodies elicited by the VLPs significantly neutralized both TBEV-FE and TBEV-Eu infections in BHK-21 cells, with inhibition rates reaching up to 90%. Altogether, these findings suggested that the VLPs exhibited superior immunogenicity and induced high levels of humoral immunity (IgG and NAb) against different subtypes of TBEV. (Tang et al., 2023)
• Challenge Protocol: VLP-immunized IFNAR−/− mice were challenged with a lethal dose (3.2×106 PFU) of the WH2012 strain of TBEV by intramuscular injection after two weeks post-boost immunization with 10 μg VLPs. (Tang et al., 2023)
• Efficacy: The infected mice displayed some abnormal behaviors, such as listlessness, circling and freezing, and all the infected mice died within 8 dpi. In contrast, immunized mice survived the challenge, and their weights did not decrease significantly. The viremia of the control group was notably high (7.9×104 TCID50/mL), with average values in the brain and intestinal tissues reaching 1.0×10^7 and 5.0×10^5 TCID50/mL, respectively. In contrast, the mice that had been immunized with the VLPs did not exhibit any neurological symptoms and the viral loads in the serum samples, brain, and intestinal tissues were negligible or undetectable. (Tang et al., 2023)