Immunogenicity of poliovirus B and T cell epitopes presented by hybrid porcine parvovirus particles

We have analysed the potential capacity of hybrid porcine parvovirus (PPV) capsids to present foreign epitopes to the immune system. Foreign sequences were introduced into the N and C termini of PPV VP2, which was previously shown to assemble spontaneously into parvovirus-like particles. The integrity of the C terminus was shown to be essential for preserving the structure of the capsid and therefore could not be used for epitope fusion. In contrast, insertion of sequences corresponding to T and B cell poliovirus epitopes in the N terminus did not alter the formation of particles. Moreover, the chimeric capsids containing the C3:T epitope were able to induce a T cell response in vivo. However, hybrid particles containing the C3:B epitope fused to the N terminus did not induce any peptide-specific antibody response, suggesting that the inserted B cell epitope was not exposed at the surface of the particles. These results show that the N terminus in PPV empty capsids is not an adequate site for insertion of B cell epitopes, but may be useful for T cell epitope presentation and suggest that the N terminus is located in an internal position.