MDV-1 VP22 conjugated VP2 enhancing immune response against infectious bursal disease virus by DNA vaccination in mice

VP22 of Marek's disease virus serotype 1 (MDV-1) could function in protein transduction. In this study, an infectious bursal disease virus VP2 gene was fused to the carboxyl termini of VP22. It showed that the fusion protein did not spread into the bystander cells from the cells transfected with pVP22-VP2, as the VP22 alone could. The VP22 proteins were found to be translocated into all the nuclei in the neighboring COS-1 cells, as analyzed by a fluorescence assay. Although mice were immunized with the recombinant DNAs mixed with polyethylenimine (PEI) at a dose of 1:2, it failed to enhance the antibody response against IBDV VP2, as measured by the indirect ELISA assay, yet the cell mediated immune response was significantly increased. The ratio of CD8(+)/CD4(+) T cells was significantly increased in the immunized group with the fusion genes, compared with the group immunized with VP2 (P