Targeting immune response with therapeutic vaccines in premalignant lesions and cervical cancer: hope or reality from clinical studies

Combined immunization against TGF-β1 enhances HPV16 E7-specific vaccine-elicited antitumour immunity in mice with grafted TC-1 tumours

Therapeutic vaccine appears to be a potential approach for the treatment of human papillomavirus (HPV)-associated tumours, but its efficacy can be dampened by immunosuppressive factors such as transforming growth factor (TGF)-β1. We sought to investigate whether active immunity against TGF-β1 enhances the anti-tumour immunity elicited by an HPV16 E7-specific vaccine that we developed previously. In this study, virus-like particles of hepatitis B virus core antigen were used as vaccine carriers to deliver either TGF-β1 B cell epitopes or E7 cytotoxic T-lymphocyte epitope. The combination of preventive immunization against TGF-β1 and therapeutic immunization with the E7 vaccine significantly reduced the growth of grafted TC-1 tumours in C57 mice, showing better efficacy than immunization with only one of the vaccines. The improved efficacy of combined immunization is evidenced by elevated IFN-γ and decreased IL-4 and TGF-β1 levels in cultured splenocytes, increased E7-specific IFN-γ-expressing splenocytes, and increased numbers of CD4⁺IFN-γ⁺ and CD8⁺IFN-γ⁺ cells and decreased numbers of Treg (CD4⁺Foxp3⁺) cells in the spleen and tumours. The results strongly indicate that targeting TGF-β1 through active immunization might be a potent approach to enhancing antigen-specific therapeutic vaccine-induced anti-tumour immune efficacy and providing a combined strategy for effective cancer immunotherapy.

Therapeutic vaccines for high-risk HPV-associated diseases

Cancer is the second leading cause of death worldwide, and it is estimated that Human papillomavirus (HPV) related cancers account for 5% of all human cancers. Current HPV vaccines are extremely effective at preventing infection and neoplastic disease; however, they are prophylactic and do not clear established infections. Therapeutic vaccines which trigger cell-mediated immune responses for the treatment of established infections and malignancies are therefore required. The E6 and E7 early genes are ideal targets for vaccine therapy due to their role in disruption of the cell cycle and their constitutive expression in premalignant and malignant tissues. Several strategies have been investigated for the development of therapeutic vaccines, including live-vector, nucleic acid, peptide, protein-based and cell-based vaccines as well as combinatorial approaches, with several vaccine candidates progressing to clinical trials. With the current understanding of the HPV life cycle, molecular mechanisms of infection, carcinogenesis, tumour biology, the tumour microenvironment and immune response mechanisms, an approved HPV therapeutic vaccine seems to be a goal not far from being achieved. In this article, the status of therapeutic HPV vaccines in clinical trials are reviewed, and the potential for plant-based vaccine production platforms described.

Therapeutic vaccines and immune checkpoints inhibition options for gynecological cancers

Treatments for gynecological cancer include surgery, chemotherapy, and radiation. However, overall survival is not improved, and novel approaches are needed. Immunotherapy has been proven efficacious in various types of cancers and multiple approaches have been recently developed. Since numerous gynecological cancers are associated to human papilloma virus (HPV) infections, therapeutic vaccines, targeting HPV epitopes, have been developed. The advancing understanding of the immune system, regulatory pathways and tumor microenvironment have produced a major interest in immune checkpoint blockade, Indeed, immune checkpoint molecules are important clinical targets in a wide variety of tumors, including gynecological. In this review, we will describe the immunotherapeutic targets and modalities available and review the most recent immunotherapeutic clinical trials in the context of gynecological cancers. The synergic results obtained from the combination of HPV therapeutic vaccines with radiotherapy, chemotherapy, or immune checkpoint inhibitors, may underlie the potential for a novel therapeutic scenario for these tumors.

Therapeutic DNA Vaccines for Human Papillomavirus and Associated Diseases

Human papillomavirus (HPV) has long been recognized as the causative agent of cervical cancer. High-risk HPV types 16 and 18 alone are responsible for over 70% of all cases of cervical cancers. More recently, HPV has been identified as an etiological factor for several other forms of cancers, including oropharyngeal, anogenital, and skin. Thus, the association of HPV with these malignancies creates an opportunity to control these HPV lesions and HPV-associated malignancies through immunization. Strategies to prevent or to therapeutically treat HPV infections have been developed and are still pushing innovative boundaries. Currently, commercial prophylactic HPV vaccines are widely available, but they are not able to control established infections or lesions. As a result, there is an urgent need for the development of therapeutic HPV vaccines, to treat existing infections, and to prevent the development of HPV-associated cancers. In particular, DNA vaccination has emerged as a promising form of therapeutic HPV vaccine. DNA vaccines have great potential for the treatment of HPV infections and HPV-associated cancers due to their safety, stability, simplicity of manufacturability, and ability to induce antigen-specific immunity. This review focuses on the current state of therapeutic HPV DNA vaccines, including results from recent and ongoing clinical trials, and outlines different strategies that have been employed to improve their potencies. The continued progress and improvements made in therapeutic HPV DNA vaccine development holds great potential for innovative ways to effectively treat HPV infections and HPV-associated diseases.

Current status and future prospects for human papillomavirus vaccines

Cervical cancer is the fourth most frequent cancer among women worldwide. Human papillomaviruses (HPVs) cause almost all cervical cancers in low-income countries. Three prophylactic HPV virus-like particle-based vaccines have been licensed to date, and they have all shown high efficacy and reliable safety profiles. However, isolated safety issues have resulted in a reluctance to use these vaccinations. In addition, the high prices of the vaccinations have caused the inequitable distribution of the vaccine: the prices are unaffordable for low-income countries. Meanwhile, great effort has been put into the development of therapeutic HPV vaccines, including protein/peptide-, live vector-, DNA- and cell-based vaccines. These new vaccines have considerable therapeutic potential but limited practical use. The development of immune checkpoint inhibitors and personalized immunotherapy remain challenges for future study. In this article, the current status of the licensed vaccines, therapeutic HPV vaccines and biosimilars, and new platforms for HPV vaccines, are reviewed, and safety issues related to the licensed vaccines are discussed. In addition, the prospects for HPV vaccines are considered.

Cervical cancer: A global health crisis

Cervical cancer is the fourth most common malignancy diagnosed in women worldwide. Nearly all cases of cervical cancer result from infection with the human papillomavirus, and the prevention of cervical cancer includes screening and vaccination. Primary treatment options for patients with cervical cancer may include surgery or a concurrent chemoradiotherapy regimen consisting of cisplatin-based chemotherapy with external beam radiotherapy and brachytherapy. Cervical cancer causes more than one quarter of a million deaths per year as a result of grossly deficient treatments in many developing countries. This warrants a concerted global effort to counter the shocking loss of life and suffering that largely goes unreported. This article provides a review of the biology, prevention, and treatment of cervical cancer, and discusses the global cervical cancer crisis and efforts to improve the prevention and treatment of the disease in underdeveloped countries. Cancer 2017;123:2404-12. © 2017 American Cancer Society.

GTL001, a bivalent therapeutic vaccine against human papillomavirus 16 and 18, induces antigen-specific CD8+ T cell responses leading to tumor regression

BACKGROUND

Prophylactic vaccines are available for women and girls not yet infected with HPV, but women already infected with HPV need a treatment to prevent progression to high-grade cervical lesions and cancer. GTL001 is a bivalent therapeutic vaccine for eradicating HPV-infected cells that contains HPV16 E7 and HPV18 E7 both fused to detoxified adenylate cyclase from Bordetella pertussis, which binds specifically to CD11b+ antigen-presenting cells. This study examined the ability of therapeutic vaccination with GTL001 adjuvanted with topical imiquimod cream to induce functional HPV16 E7- and HPV18 E7-specific CD8+ T cell responses.

METHODS

Binding of GTL001 to human CD11b was assessed by a cell-based competition binding assay. Cellular immunogenicity of intradermal vaccination with GTL001 was assessed in C57BL/6 mice by enzyme-linked immunospot assay and in vivo killing assays. In vivo efficacy of GTL001 vaccination was investigated in the TC-1 murine HPV16 E7-expressing tumor model.

RESULTS

GTL001 bound specifically to the human CD11b/CD18 receptor. GTL001 adjuvanted with topical 5% imiquimod cream induced HPV16 E7 and HPV18 E7-specific CD8+ T cell responses. This CD8+ T-cell response mediated in vivo killing of HPV E7-expressing cells. In the HPV16 E7-expressing tumor model, GTL001 adjuvanted with imiquimod but not imiquimod alone or a combination of unconjugated HPV16 E7 and HPV18 E7 caused complete tumor regression.

CONCLUSIONS

GTL001 adjuvanted with topical 5% imiquimod is immunogenic and induces HPV16 E7 and HPV18 E7-specific CD8+ T cell responses that can kill HPV E7-expressing cells and eliminate HPV E7-expressing tumors.

Recent advances in understanding and preventing human papillomavirus-related disease

High-risk human papillomaviruses (hrHPV) are responsible for anogenital and oropharyngeal cancers, which together account for at least 5% of cancers worldwide. Industrialised nations have benefitted from highly effective screening for the prevention of cervical cancer in recent decades, yet this vital intervention remains inaccessible to millions of women in low- and middle-income countries (LMICs), who bear the greatest burden of HPV disease. While there is an urgent need to increase investment in basic health infrastructure and rollout of prophylactic vaccination, there are now unprecedented opportunities to exploit recent scientific and technological advances in screening and treatment of pre-invasive hrHPV lesions and to adapt them for delivery at scale in resource-limited settings. In addition, non-surgical approaches to the treatment of cervical intraepithelial neoplasia and other hrHPV lesions are showing encouraging results in clinical trials of therapeutic vaccines and antiviral agents. Finally, the use of next-generation sequencing to characterise the vaginal microbial environment is beginning to shed light on host factors that may influence the natural history of HPV infections. In this article, we focus on recent advances in these areas and discuss their potential for impact on HPV disease.

Control of immune escaped human papilloma virus is regained after therapeutic vaccination

High-risk human papillomaviruses infect the basal cells of human epithelia. There it deploys several mechanisms to suppress pathogen receptor recognition signalling, impeding the immune system to control viral infection. Furthermore, infected cells become more resistant to type I and II interferon, tumour necrosis factor-α and CD40 activation, via interference with downstream programs halting viral replication or regulating the proliferation and cell death. Consequently, some infected individuals fail to raise early protein-specific T-cell responses that are strong enough to protect against virus-induced premalignant disease and ultimately cancer. Therapeutic vaccines triggering a strong T-cell response against the early proteins can successfully be used to treat patients at the premalignant stage but combinations of different treatment modalities are required for cancer therapy.

A plant protein signal sequence improved humoral immune response to HPV prophylactic and therapeutic DNA vaccines

Signal sequences (ss) play a critical role in the sorting of nascent secretory and membrane proteins. This function has been conserved from bacteria through eukaryotes, although ss appear diverse in length and amino acid composition. Sorting of proteins is also critical to instruct antigens for a proper immunological response. Thus, a plant ss was used to drive Human Papillomavirus (HPV) model antigens into the human secretory pathway: the HPV16 E7 oncoprotein, its chimera with the coat protein (CP) of the Potato Virus X (PVX), the first 200 amino acids of the HPV16 minor capsid protein L2 (known to harbour cross-reacting epitopes) and its chimera with E7 gene. These genes were used to transfect HEK-293 cells and to immunize C57BL/6 mice. The ss-provided genes were expressed, and proteins detected by immunofluorescence and immunoblotting. Mouse immunization with DNA constructs carrying the ss elicited a strong humoral response against both E7 and L2 and a weak cell-mediated immunity. To our knowledge this is the first demonstration that a signal sequence derived from a plant can modulate the sorting of a heterologous protein in mammalian cells. This activity in mammalian cells may be responsible for the observed increased humoral response to DNA-based vaccines that are generally weak inducers of IgG response. This might open new perspectives in the design of DNA vaccines, especially to counteract infections where a strong humoral response is needed.

Therapeutic use of the HPV vaccine in Recurrent Respiratory Papillomatosis: A case report

Recurrent Respiratory Papillomatosis (RRP) is a condition characterized by recurring squamous papillomas in the aerodigestive tract due to Human Papilloma Virus (HPV) infection. Treatment includes surgical debridement of the lesions often with adjuvant therapy. A newer adjuvant agent being tested is the HPV vaccine. The case report includes a child with RRP who underwent 10 surgeries in a year with an average inter-surgical interval (ISI) of 46 days. The patient then received the scheduled regimen of 3 doses of 9 valent HPV vaccine. Since beginning the vaccination, her average ISI increased to 113 days and as of writing of this paper only 1 surgery in the last 340 days. It is theorized that the increase in humoral response to the virus can slow the course of the disease, lengthen the ISI, and decrease morbidity. The results of this case report lends evidence to the use of the HPV vaccine as a therapeutic adjuvant therapy for RRP.

Identificaiton of Novel Immunogenic Human Papillomavirus Type 16 E7-Specific Epitopes Restricted to HLA-A*33;03 for Cervical Cancer Immunotherapy

PURPOSE

To identify new immunogenic HLA-A*33;03-restricted epitopes from the human papillomavirus (HPV) 16 E7 protein for immunotherapy against cervical cancer.

MATERIALS AND METHODS

We synthesized fourteen overlapping 15-amino acid peptides and measured intracellular interferon-γ (IFN-γ) production in PBMC and CD8+ cytotoxic T lymphocytes (CTLs) after sensitization with these peptides using flow cytometry and ELISpot assay. The immunogenicity of epitopes was verified using a ⁵¹Cr release assay with SNU1299 cells.

RESULTS

Among the fourteen 15-amino acid peptides, E7₄₉₋₆₃ (RAHYNIVTFCCKCDS) demonstrated the highest IFN-γ production from peripheral blood mononuclear cells (PBMCs), and CD8+ CTLs sensitized with E7₄₉₋₆₃ showed higher cytotoxic effect against SNU1299 cells than did CD8+ CTLs sensitized with other peptides or a negative control group. Thirteen 9- or 10-amino acid overlapping peptides spanning E7₄₉₋₆₃, E7₅₀₋₅₉ (AHYNIVTFCC), and E7₅₂₋₆₁ (YNIVTFCCKC) induced significantly higher IFN-γ production and cytotoxic effects against SNU1299 cells than the other peptides and negative controls, and the cytotoxicity of E7₅₀₋₅₉- and E7₅₂₋₆₁-sensitized PBMCs was induced via the cytolytic effect of CD8+ CTLs.

CONCLUSION

We identified E7₅₀₋₅₉ and E7₅₂₋₆₁ as novel HPV 16 E7 epitopes for HLA-A*33;03. CD8+ CTL sensitized with these peptides result in an antitumor effect against cervical cancer cells. These epitopes could be useful for immune monitoring and immunotherapy for cervical cancer and HPV 16-related diseases including anal cancer and oropharyngeal cancer.

DNA-based immunotherapy for HPV-associated head and neck cancer

Squamous cell carcinoma of the head and neck (SCCHN) accounts for 3% of all cancers. Most patients present with locally advanced disease, where multimodality therapies are used with curative intent. Despite favorable early local treatment results, about one third of the patients will eventually develop metastatic disease. Immunotherapy offers a novel therapeutic strategy beyond cytotoxic chemotherapy, with initial approvals in melanoma and non-small-cell lung cancer. HPV-associated SCCHN is a distinct subset, with unique epidemiology and treatment outcomes. Both subsets of SCCHN (HPV-related or not) are particularly favorable for immunotherapy, as immune evasion and dysregulation have been shown to play a key role in the initiation and progression of disease. This review focuses on the latest developments in immunotherapy in SCCHN, with a particular focus on DNA-based approaches including vaccine and adoptive cellular therapies.