PAPILLOMA VLP IMMUNIZATION AGAINST HPV-TRANSFORMED CELLS

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Human papillomaviruses (HPVs) are implicated in the etiology of cervical cancer. HPV DNA is detected in more than 95% of cervical carcinomas and 60% of these are accounted for by the high risk HPV type 16 (HPV16). The E6 and E7 genes of HPV16 are selectively retained and expressed in human carcinomas and are sufficient for the transformation of both mouse fibroblasts and primary human keratinocytes. This allows fundamental immunological experiments in mice that can be extrapolated to humans. High risk HPVs infect the basal layers of the epithelium of the anogenital tract in which they replicate. Since these replication conditions can not yet be mimicked in vitro, the development of classical vaccines has been hampered by the lack of obtaining sufficient amounts of intact HPV16 virions. However, when L1, the major virion protein of the virus is over expressed in eukaryotic cells, it assembles into virus-like particles (VLPs). Recombinant VLPs that express other proteins of the virus such as E6 and E7 can be made and will be used to study their preventative and therapeutic potential which is the long-term objective of this proposal. We will address the following specific aims: 1) To determine if and how VLP immunization effectively prevents the outgrowth of HPV16 induced tumors in mice. 2) To determine the therapeutic potential of recombinant VLPs in tumor-bearing mice. 3) To determine the potential of recombinant VLPs to induce HLA-restricted T cell responses in human T cell cultures in vitro and 4) To determine the immunologic potential of recombinant VLPs expressing other tumor-associated antigens or cytokines. To achieve these aims the following methodology will be used: 1) mice will be immunized with VLPs and challenged with HPV16-induced tumor cells, specific neutralizing antibodies, T cell responses and tumor out growth in VLP immunized mice will be analyzed. 2) Tumor bearing mice will be treated by local or systemic inoculation of VLPs. 3) Human HPV specific T cell responses will be induced by in vitro immunization of human peripheral blood cells with antigen presenting cells pseudo-infected with VLPs. 4) VLPs recombinant for other tumor-associated antigens or cytokines will be analyzed for their immunizing effects and compared to other vaccination strategies. This combined analysis will shed light on the potential of VLPs to induce preventative and/or therapeutic T-cell mediated immune responses against virus induced tumors like HPV16 induced cervical cancer in patients.