Virus-like particles (VLPs) are efficient ways to express antigens of interest for strong induction of antigen specific antibodies. While antibodies against infectious pathogens are key components of prophylactic vaccines, ones that are produced by al...
Virus-like particles (VLPs) are efficient ways to express antigens of interest for strong induction of antigen specific antibodies. While antibodies against infectious pathogens are key components of prophylactic vaccines, ones that are produced by allergens play crucial roles in allergic reactions. In this thesis study, I examined whether VLPs could be utilized (i) to induce antibody, especially IgG isotype, responses to antigens of MERS-CoV for the identification of potential neutralization targets of MERS-CoV, and (ii) to elicit IgE responses to hen egg lysozyme (HEL), a model allergen, for the investigation of allergenicity of proteins, in mice. In the first part, VLPs that express four different domains of MERS-CoV were produced and administrated in mice for generation of IgG against respective target domains of the spike protein. Using in vitro neutralization assay, I found that IgG antibodies produced by immunization with the VLPs exhibited highly potent neutralizing activity against pseudo-MERS-CoV infection. Proteolytic cleavage site fusion peptide (PSFP), which is responsible for proteolytic cleavage and fusion into target cells, has not been reported as a target of MERS-CoV vaccines. I observed IgG antibody targeting S1, S2, receptor binding domain (RBD), or PSFP exhibited neutralizing ability, particularly in immune serum targeting S1 and RBD, which has been targeted for protective MERS-CoV vaccine development. In the second part, to examine whether VLP system could be used as a sensitization tool in mice, VLP expressing HEL were produced and administrated in mice for elicitation of IgE against HEL protein. Following systemic and local challenges of the VLP-sensitized mice with recombinant HEL protein, increase of serum histamine, reduced mobility and production of cytokines were observed. Taken together, I demonstrate that (i) IgG antibodies produced by VLP immunization are able to neutralize viral infection and (ii) VLP that express model allergens can be an efficient tool to induce allergen specific IgE responses in mice, which could provide a novel platform to investigate allergenicity of proteins.