Purpose: Virus-like particles (VLPs) are being developed as a promising vaccine platform and therapeutic delivery. Various strategies for effectively constructing VLPs have been studied, but relatively few studies have been done on various factors affecting storage. In this study, we investigated the antigenic changes of VLPs in an acidic or basic pH environment using influenza VLPs as an experimental model.

Materials and methods: Influenza VLPs containing hemagglutination and M1 proteins were generated and their antigenicity and protective immunity in vitro and in vivo were evaluated after exposure to acidic (pH 4 and 5) or basic (pH 9 and 10) pH buffers.

Results: VLP exposed to basic pH showed similar levels of antigenicity to those stored in neutral pH, while antigenicity of VLP exposed to acidic pH was found to be significantly reduced compared to those expose neutral or basic pH. All groups of mice responded effectively to low concentrations of virus infections; however, VLP vaccine groups exposed to acid pH were found not to induce sufficient protective immune responses when a high concentration of influenza virus infection.

Conclusion: In order for VLP to be used as a more powerful vaccine platform, it should be developed in a strategic way to respond well to external changes such as acidic pH conditions.