Immunogenicity of different recombinant rabbit hemorrhagic disease virus-like particles carrying CD8+ T cell epitope from chicken ovalbumin (OVA)

•Sequences of OVA CD8+ T epitopes were integrated into VP60 of RHDV at different locations.•Four recombinant baculoviruses were generated by baculovirus expression system.•Four recombinant proteins were expressed effectively.•Four recombinant proteins could self-assemble into VLPs.•I1 and I2 were able to elicit high levels of IFN-γ secretion in the murine model.

To explore the capacity and immunogenicity of virus-like particles (VLPs) of rabbit hemorrhagic disease virus (RHDV) accommodating foreign amino acid sequences, integrations were performed at the following four locations of the structural protein VP60 of RHDV using the OVA257–264 CD8+ T cell epitope (SIINFEKL): (1) inserting at the N-terminus of the VP60 protein (N1); (2) replacing amino acid positions 2–14 of the VP60 protein (N2); (3) replacing amino acid positions 196–207 of the VP60 protein (I1); and (4) replacing amino acid positions 217–228 of the VP60 protein (I2). The recombinant proteins were expressed by baculovirus expression system. The ability to form RHDV-like particles was confirmed by electron microscopy. The immunogenicity of the four recombinant proteins (N1, N2, I1 and I2) was evaluated in mice without any adjuvants. The results indicated that the four recombinant proteins (N1, N2, I1 and I2) could assemble into VLPs. All of the recombinant proteins could induce a specific immune response. Recombinant proteins I1 and I2 were able to elicit both high levels of IFN-γ secretion and anti-VP60 specific immune responses in the murine model. The levels of the VP60-specific IgG antibody in groups I1 and I2 displayed higher optical density (OD) values than those of groups N1 and N2 (P < 0.001, P < 0.001). The number of IFN-γ-producing splenocytes in mice that were immunized with recombinant proteins I1 and I2 was also significantly greater compared with mice that were immunized with recombinant proteins N1 and N2 (P < 0.01). All of these above mentioned results might be beneficial to the establishment of the RHDV-VLPs display system.