Antitumor efficacy of Venezuelan equine encephalitis virus replicon particles encoding mutated HPV16 E6 and E7 genes.

An effective vaccine for treating human papillomavirus (HPV)-associated malignancies such as cervical cancer should elicit strong T cell-mediated immunity (CMI) against the E6 and/or E7 proteins necessary for the malignant state. We have developed Venezuelan equine encephalitis (VEE) virus replicon particle (VRP) vaccines encoding the HPV16 E6 and E7 genes and tested their immunogenicity and antitumor efficacy. The E6 and E7 genes were fused to create one open reading frame and mutated at four or at five amino acid positions to inactivate their oncogenic potential. VRP encoding mutant or wild type E6 and E7 proteins elicited comparable cytotoxic T lymphocyte (CTL) responses to an immunodominant E7(49-57) epitope and generated comparable antitumor responses in several HPV16 E6(+)E7(+) tumor challenge models: protection from either C3 or TC-1 tumor challenge was observed in 100% of VRP-vaccinated mice. Eradication of C3 tumors was observed in approximately 90% of mice following therapeutic VRP vaccination. Eradication of HLF16 tumors lacking the E7(49-57) epitope was observed in 90% of human leukocyte antigen (HLA)-A(*)0201 transgenic mice following therapeutic VRP vaccination. Finally, the predicted inactivation of E6 and E7 oncogenic potential was confirmed by demonstrating normal levels of both p53 and retinoblastoma proteins in human mammary epithelial cells (MEC) infected with VRP expressing mutant E6 and E7 genes. These promising results support the continued development of mutant E6 and E7 VRP as safe and effective candidates for clinical evaluation against HPV-associated disease.

CD4+ T cell matters in tumor immunity.

CD4+ T cells have been shown to be able to affect tumor growth through both direct and indirect means. In addition, a requirement has been demonstrated for CD4+ T cells in the regulation and induction of T cell memory, and CD4+ suppressor T cells have been identified, stressing a role for CD4+ T cells in the induction and maintenance of antitumor immune responses. A review of the involvement of CD4+ T cells at different stages of tumor immunity is provided, and based on these data we discuss how CD4+ T cell response induction could be incorporated into tumor immunotherapy strategies.

Cervical cancer vaccines: recent advances in HPV research.

Carcinomas of the anogenital tract, particularly cancer of the cervix, account for almost 12% of all cancers in women, and so represent the second most frequent gynecological malignancy in the world (48). It is well established that chronic infection of cervical epithelium by human papillomaviruses (HPV) is necessary for the development of cervical cancer. In fact, HPV DNA has been demonstrated in more than 99.7% of cervical cancer biopsy specimens, with high-risk HPV16 and HPV18 sequences being most prevalent (45,73). Therefore, an effective vaccine that would mount an immune response against HPV-related proteins might contribute to the prevention or elimination of HPV expressing lesions. This review will concentrate on the most recent advances in vaccine-mediated prevention and immunotherapy of HPV-induced cervical cancer, including presentations from the 20(th) International HPV Conference held in October 2002 in Paris.

HPV protein/peptide vaccines: from animal models to clinical trials.

Human Papillomaviruses are viruses that infect the epithelial layers of the oral, rectal, vaginal, and cervical mucosa. There is a causal link between the development of cervical cancer and some other cancers and high-risk human papillomavirus infection (1, 2). Currently there is no prophylactic or therapeutic vaccine available against human papillomavirus infection and its associated lesions. In addition, there exists a high degree of species specificity associated with papillomavirus infection precluding human papillomavirus's use in animal models. Therefore, multiple researchers have utilized a variety of homologous animal papillomaviruses and animal model systems for the development of vaccine strategies against papillomaviruses. The goal of their efforts is to identify vaccine strategies that are efficacious in the animal model systems and translate these strategies into human clinical trials against human papillomavirus. The development of such a vaccine would ultimately result in a reduction in the incidence of cervical cancer and some other HPV-linked cancers and may provide therapy for individuals harboring papillomavirus lesions. This review discusses the advances in papillomavirus vaccinology using proteins/peptides, from the work completed in the animal models to the results of the early human clinical trials.

Establishment of an HLA-A*0201 human papillomavirus type 16 tumor model to determine the efficacy of vaccination strategies in HLA-A*0201 transgenic mice.

With the increasing generation of new cancer vaccine strategies, there is also an increasing demand for preclinical models that can carefully predict the efficacy of these vaccines in humans. However, the only tumor models available to study vaccines against human papillomavirus (HPV) 16 have been developed in C57BL/6 mice. To test the HLA-restricted capabilities of vaccination strategies, it is important to establish a tumor model in HLA-A*0201 transgenic mice. By transfecting heart lung fibroblasts from HLA-A*0201 mice with HPV16 E6 and E7 oncogenes and H-Ras V12, we have generated a transgenic cell line that is tumorigenic in HLA-A*0201 mice. The dominant H-2D(b) HPV16 E7 epitope was removed from the E7 construct to ensure that all antitumor responses were mediated through the HLA-A*0201-restricted epitopes. We used this tumor model to test the efficacy of two genetic vaccines: a plasmid DNA multi-epitope vaccine encoding human epitopes of HPV16, and a Venezuelan equine encephalitis (VEE) virus-based vector to deliver HPV16 E6 and E7 RNA. We show that both our multi-epitope DNA- and VEE-based vaccines protect 100% of HLA-A*0201 transgenic mice from tumor challenge and elicit a specific T-cell response against multiple HLA-A*0201-restricted HPV16 epitopes. Furthermore, both vaccines significantly decreased tumor burden when tested therapeutically. In conclusion, this is the first tumor model that allows for the assessment of the potential of a vaccine to induce HPV-directed, HLA-A*0201-restricted, antitumor responses in mice. These results pave the way for the clinical evaluation of these vaccines.