Zimna et al.
Influence of adjuvant type and route of administration on the immunogenicity of Leishmania-derived tick-borne encephalitis virus-like particles – A recombinant vaccine candidate.
Antiviral Research. 2024; 228:105941. doi:/10.1016/j.antiviral.2024.105941
Recently, a novel tick-borne encephalitis (TBE) vaccine candidate has been described. This vaccine is based on virus-like particles (VLP) containing glycoprotein E and the membrane protein M produced in the protozoan Leishmania tarentolae (see e.g., December 2023 Newsletter). A new study has analyzed various adjuvants and routes of application to determine the optimal combination for effective vaccination.
The adjuvants tested were AddaS03 (an analog of AS03 based on squalene) and a combination of monophosphoryl A with Alhydrogel (aluminum hydroxide wet gel suspension). These were injected either intramuscularly or subcutaneously into BALB/c mice. Although the role of cellular response in TBE vaccines remains incompletely understood, existing studies suggest that relying solely on the humoral immune response may not be sufficient to prevent the virus from infecting the central nervous system.
According to the authors, neutralization titers did not necessarily correspond to the highest levels of antibodies within groups. The results of this study indicate that not all antibodies induced by, for example, subcutaneous administration of a vaccine formulation containing AddaS03, had neutralizing activity. Regardless of the route of administration, the combination of Alhydrogel and MPLA induced the most robust Th1 response.
While all currently licensed TBE vaccines are adjuvanted with aluminum hydroxide, the new VLP-based experimental TBE vaccine may be developed with a novel balanced Th1/Th2 adjuvant combination for human application.