Papillomaviruses (PVs) infect the epithelia of animals and man where they generally induce benign proliferation at the site of infection. However, there is a strong association between malignant progression of human genital lesions and certain HPV types, most frequently HPV 16. We have generated virus-like particles (VLPs) for HPV 16 and other PVs that consist of the L1 major capsid protein or L1 plus L2, the minor capsid protein. Parenteral injection of purifed VLPs induced high titers of neutralizing antibodies and protection from experimental challenge in animal models. Based upon these results, we have validated GMP grade VLPs and have recently completed a phase 1 and phase 2 clinical trial of an HPV16 VLP vaccine. Vaccinees, even those vaccinated in the absence of adjuvant, consistantly produced high titers of HPV16 psuedovirion neutralizing antibodies and reported only minor side effects. We are also developing alternative vaccine candidates. To increase the therapeutic potential of a VLP-based vaccine, we have incorporated non-structural HPV proteins into the VLPs as L2 fusion proteins. Vaccination with an HPV16 E7 or E7-E2 chimeric VLP generated a CD8 restricted T cell response that protected mice from tumor challenge using an E7 expressing tumor line and also induced regression of established tumors. Clinical grade chimeric VLPs for a phase I clinical trial are now being produced. To increase mucosal immune responses, we have tested intranasal instillation of purified VLPs in mice. In contrast to parenteral inoculation of VLPs, this protocol elicited both secretory IgA and transudated IgG in the female genital tract. Neutralizing antibodies were detected throughout the estus cycle in intranasally vaccinated mice, but not in those vaccinated parenterally. Potent anti-tumor cell mediated responses to VLPs were also detected after intranasal administration.To break B-cell tolerance and induce antibody responses to a self-protein, we have displayed the target self-polypeptide in an ordered array on a VLP surface. Display of a TNF peptide induced high titers of TNF IgG in mice that partially protected the mice from experimentally induced rheumatoid arthritis. Mice and macaques vaccinated with VLPs displaying the N-terminus of macaque CCR5 produced high titers of antibodies that bound cell surface CCR5 and blocked HIV infection of cultured cells. These findings suggest a general method for inducing auto-antibodies, with many basic and applied research applications. To begin to determine how VLP vaccination is able to induce potent B and T cell responses in the absence of adjuvant and without local inflammation, we have examine the interaction of VLPs with immature mouse bone marrow-derived dentritic cells (BMDCs). BMDCs rapidly bound and internalized VLPs. Interaction with VLPs, but not disorganized capsid subunits, resulted in rapid phenotypic maturation of BMDCs, but delayed release of pro-inflammatory cytokines, relative to a well characterized inducer, bacterial lipopolysacharide. VLP activated BMDCs induced a Th1 dominated primary T cell response in vitro. The results provide evidence that pattern recognition of virion surfaces by dendritic cell can play a central role in anti-virion immunity.
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