Impaired Antigen Presentation and Effectiveness of Combined Active/Passive Immunotherapy for Epithelial Tumors

Background: Although immunization with tumor antigens can eliminate many transplantable tumors in animal models, immune effector mechanisms associated with successful immunotherapy of epithelial cancers remain undefined. Methods: Skin from transgenic mice expressing the cervical cancer-associated tumor antigen human papillornavirus type 16 (HPV16) E6 or E7 proteins from a keratin 14 promoter was grafted onto syngeneic, non-transgenic mice. Skin graft rejection was measured after active immunization with HPV16 E7 and adoptive transfer of antigen-specific T cells. Cytokine secretion of lymphocytes from mice receiving skin grafts and immunotherapy was detected by enzyme-linked immunosorbent assay, and HPV16 E7-specific memory CD8(+) T cells were detected by flow cytometry and ELISPOT. Results: Skin grafts containing HPV16 E6- or E7-expressing keratinocytes were not rejected spontaneously or following immunization with E7 protein and adjuvant. Adoptive transfer of E7-specific T-cell receptor transgenic CD8(+) T cells combined with immunization resulted in induction of antigen-specific interferon gamma-secreting CD8(+) T cells and rejection of HPV16 E7-expressing grafts. Specific memory CD8(+) T cells were generated by immunotherapy. However, a further HPV16 E7 graft was rejected from animals with memory T cells only after a second E7 immunization. Conclusions: Antigen-specific CD8(+) T cells can destroy epithelium expressing HPV16 E7 tumor antigen, but presentation of E7 antigen from skin is insufficient to reactivate memory CD8(+) T cells induced by immunotherapy. Thus, effective cancer immunotherapy in humans may need to invoke sufficient effector as well as memory T cells.

ISCOMATRIX (TM) adjuvant: An adjuvant suitable for use in anticancer vaccines

Human Papillomavirus type 16 (HPV16) E6 and E7 oncoproteins are associated with cervical cancer development and progression and can therefore be used as target antigens for cancer immunotherapy. In this study we evaluated the immunogenicity in mice, of different vaccine formulations using recombinant HPV16 derived E6E7 or E7GST fusion proteins. When co-administered with ISCOMATRIX(TM) adjuvant, these E6E7 proteins consistently induced E7 specific CTL, in vivo tumor protection, antibody and DTH responses. ISCOMATRIX(TM) adjuvant has been developed for use in the formulation of novel human vaccines and has been evaluated for safety and toxicity in human trials. A formulation containing aluminum hydroxide (Al(OH)(3)) gave a lesser degree of E7 specific antibody, and no local E7 specific CTL response but similar DTH and tumor protection. These findings demonstrate the potential of ISCOMATRIX(TM) adjuvant to stimulate both cellular and humoral immune responses to endogenously processed target antigens, and hence is the preferred adjuvant when CTL responses are desirable. (C) 2004 Elsevier Ltd. All rights reserved.

The human papillomavirus type 16 E7 protein binds human interferon regulatory factor-9 via a novel PEST domain required for transformation

It is critical that viruses are able to avoid the antiviral activities of interferon (IFN). We have shown previously that the human papillomavirus (HPV) is able to avoid IFN-alpha via interaction of the HPV-16 E7 protein with IFN regulatory factor-9 (IRF-9). Here, we investigated the details of the interaction using HPV-16 E7 peptide mapping to show that IRF-9 binds HPV-16 E7 in a domain encompassing amino acids 25-36. A closer examination of this region indicates this is a novel proline, glutamate, serine, and threonine-rich (PEST) domain, with a PEST score of 8.74. We have also mapped the region of interaction within IRF-9 and found that amino acids 354-393 play an important role in binding to HPV-16 E7. This region of IRF-9 encompasses the IRF association domain (IAD), a region important for protein-protein interaction central to IRF function. Finally, we used alanine-scanning mutagenesis to determine if E7-IRF-9 interaction was important for E7-mediated cellular transformation and found that the HPV-16 E7 mutants Y25A, E26A, S31A, S32A, and E35A, but not L28A and N29A, caused loss of transformation ability. Preliminary data suggest loss of IRF-9 interaction with E7 mutants correlated with transformation. Our work suggests E7- IRF- 9 interaction is important for the transforming ability of HPV-16 E7 and that HPV-16 E7 may interact with other IRF proteins that have IAD domains.

God's gift to women: The human papillomavirus vaccine

An Australian newspaper recently bestowed Ian Frazer the title of God's gift to women for his research team's part in developing a vaccine to help control cervical cancer. Here Frazer discusses this work and the science behind the vaccine.

Chapter 8 HPV vaccines

Vaccines to prevent infection with high-risk human papillomaviruses (HPV) will help protect women against cervical cancer, and some are likely to be available within the next year. One vaccine, a quadrivalent vaccine against HPV types 6, 11, 16 and 18 and known as Garadsil ©(Merck &Co., Inc), was approved by the Federal Drug Administration (FDA) for the prevention of cervical cancer, cervical cancer precursors and vulval and vaginal cancer precursors associated with HPV 16 and 18 in June 2006. In addition, the vaccine has been approved for the prevention of genital warts and low grade cervical lesions e.g. cervical intraepithelial neoplasia1. The main vaccines components are recombinant viral capsid proteins assembled into virus-like particles and alum-based adjuvants. If given before HPV infection, the vaccines, which induce HPV type-specific, virus-neutralizing antibodies, have proven safe and highly effective at preventing HPV infection and its clinical consequences, including high-grade cervical lesions. Their use should not immediately alter existing screening programs for cervical cancer, however. Because they incorporate only the 2 HPV types most commonly associated with cervical cancer (HPV-16 and HPV-18), they can only prevent about 70% of cervical cancers. Vaccines to treat existing HPV infection are under development but are unlikely to become clinically available in the near future.

Assembly of Human Papillomavirus Type-16 Virus-Like Particles: Multifactorial Study of Assembly and Competing Aggregation

Pentameric capsomeres of human papillomavirus capsid protein L1 expressed in Escherichia coli self-assemble into virus-like particles (VLPs) in vitro. A multifactorial experimental design was used to explore a wide range of solution conditions to optimize the assembly process. The degree of assembly was measured using an enzyme-linked immunosorbent assay, and a high-throughput turbidity assay was developed to monitor competing aggregation. The presence of zinc ions in the assembly buffer greatly increased the incidence of aggregation and had to be excluded from the experiment for meaningful analysis. Assembly of VLPs was optimal at a pH of about 6.5, calcium and sodium ions had no measurable effect, and dithiothreitol and glutathione inhibited assembly. Tryptophan fluorescence spectroscopy demonstrated that an increase in urea concentration reduced the rate of VLP formation but had no effect on the final concentration of assembled VLPs. This study demonstrates the use of the hanging-drop vapor-diffusion crystallization method to screen for conditions that promote aggregation and the use of tryptophan fluorescence spectroscopy for real-time monitoring of the assembly process.