A candidate tick-borne encephalitis virus vaccine based on virus-like particles induces specific cellular and humoral immunity in mice

Tick-borne encephalitis (TBE) is an important zoonotic viral disease transmitted by ticks. In recent decades, global climate change has increased human exposure to ticks, and mortality rate have gradually risen. Effective vaccines are essential for controlling TBE as specific antiviral treatment is unavailable. Vaccine candidates based on virus-like particles (VLPs) have previously been demonstrated to be effective in eliciting excellent immune responses against influenza virus and SARS-CoV-2. Here, we constructed TBE virus (TBEV) VLPs containing the envelope and membrane proteins derived from the Far Eastern TBEV strain (WH2012) using an insect cell-baculovirus expression system. Induction of immune responses was investigated in mice following intramuscular injection with the TBEV VLPs vaccine candidates formulated with a combination of poly(I:C) and Montanide ISA201VG adjuvants. Mice produced memory T-cells and serum-specific IgG antibodies that averaged up to 1:10^4.6 and remained at 1:10⁴ (mean) at 24 wk after three immunizations. TBEV VLPs vaccine was able to provide long-term antibody protection against TBEV, making it a promising subunit vaccine candidate for this disease.