Cellular and humoral immunogenicity of hamster polyomavirus-derived virus-like particles harboring a mucin 1 cytotoxic T-cell epitope.

In this study, we examined hamster polyomavirus (HaPyV) major capsid protein VP1-derived virus-like particles (VLPs) as a carrier for a human tumor-associated cytotoxic T lymphocyte (CTL) epitope. The VP1 tolerated the insertion of an HLA-*A2-restricted CTL epitope from human mucin 1 (MUC1) into two sites independently and simultaneously, without interfering with assembly of chimeric VLPs. Chimeric VLPs did not differ in the entry pathway or maturation potential of human dendritic cells (hDCs) compared to unmodified VLPs. Recently we demonstrated that immunization of BALB/c mice with chimeric VLPs harboring two MUC1 insertions resulted in the generation of MUC1-specific monoclonal antibodies. Here we demonstrate that the monoclonal antibodies generated react specifically with human tumor cells. Co-cultivation of chimeric VLP-primed hDCs with autologous peripheral blood leukocytes resulted in the activation of MUC1 epitope-specific CD8(+) T cells. This was evidenced by IFN-gamma secretion of an expanded MUC1-specific CD8(+) T-cell pool. The induction of epitope-specific T cells in a human in vitro model and of murine MUC1-reactive antibodies in vivo indicate the potential of chimeric HaPyV VP1-derived VLPs as a delivery vehicle for immunotherapeutic targets.