Construction and characterisation of a recombinant vaccinia virus expressing human papillomavirus proteins for immunotherapy of cervical cancer

Elimination of Human Papillomavirus 16-Positive Tumors by a Mucosal rAd5 Therapeutic Vaccination in a Pre-Clinical Murine Study

Therapeutic vaccination can harness the body's cellular immune system to target and destroy cancerous cells. Several treatment options are available to eliminate pre-cancerous and cancerous lesions caused by human papillomaviruses (HPV), but may not result in a long-term cure. Therapeutic vaccination may offer an effective, durable, and minimally intrusive alternative. We developed mucosally delivered, recombinant, non-replicating human adenovirus type 5 (rAd5)-vectored vaccines that encode HPV16's oncogenic proteins E6 and E7 alongside a molecular dsRNA adjuvant. The induction of antigen-specific T cells and the therapeutic efficacy of rAd5 were evaluated in a mouse model of HPV tumorigenesis where E6E7-transformed cells, TC-1, were implanted subcutaneously in C57BL/6 mice. After tumor growth, mice were treated intranasally with rAd5 vaccines expressing the wildtype form of E6E7 (rAd5-16/E6E7Wt) in combination with an anti-PD-1 antibody or isotype control. Animals treated with rAd5-16/E6E7Wt with and without anti-PD-1 had significant reductions in tumor volume and increased survival compared to controls. Further, animals treated with rAd5-16/E6E7Wt had increased CD4+ and CD8+ tumor-infiltrating lymphocytes (TILs) and produced a cytotoxic tumor microenvironment. In a second study, the immunogenicity of a non-transformative form of E6E7 (rAd5-16/E6E7Mu) and a vaccine encoding predicted T cell epitopes of E6E7 (rAd5-16/E6E7epi) were evaluated. These vaccines elicited significant reductions in TC-1 tumor volume and increased survival of animals. Antigen-specific CD8+ T effector memory cells were observed in the animals treated with E6E7-encoding rAd5, but not in the rAd5-empty group. The work described here demonstrates that this mucosal vaccination can be used therapeutically to elicit specific cellular immunity and further identifies a clinical candidate with great potential for the treatment and prevention of human cervical cancer.

The Interaction of Human Papillomavirus Infection and Prostaglandin E2 Signaling in Carcinogenesis: A Focus on Cervical Cancer Therapeutics

Chronic infection by high-risk human papillomaviruses (HPV) and chronic inflammation are factors associated with the onset and progression of several neoplasias, including cervical cancer. Oncogenic proteins E5, E6, and E7 from HPV are the main drivers of cervical carcinogenesis. In the present article, we review the general mechanisms of HPV-driven cervical carcinogenesis, as well as the involvement of cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2) and downstream effectors in this pathology. We also review the evidence on the crosstalk between chronic HPV infection and PGE2 signaling, leading to immune response weakening and cervical cancer development. Finally, the last section updates the current therapeutic and preventive options targeting PGE2-derived inflammation and HPV infection in cervical cancer. These treatments include nonsteroidal anti-inflammatory drugs, prophylactic and therapeutical vaccines, immunomodulators, antivirals, and nanotechnology. Inflammatory signaling pathways are closely related to the carcinogenic nature of the virus, highlighting inflammation as a co-factor for HPV-dependent carcinogenesis. Therefore, blocking inflammatory signaling pathways, modulating immune response against HPV, and targeting the virus represent excellent options for anti-tumoral therapies in cervical cancer.

Development of DNA Vaccine Targeting E6 and E7 Proteins of Human Papillomavirus 16 (HPV16) and HPV18 for Immunotherapy in Combination with Recombinant Vaccinia Boost and PD-1 Antibody

Immunotherapy for cervical cancer should target high-risk human papillomavirus types 16 and 18, which cause 50% and 20% of cervical cancers, respectively. Here, we describe the construction and characterization of the pBI-11 DNA vaccine via the addition of codon-optimized human papillomavirus 18 (HPV18) E7 and HPV16 and 18 E6 genes to the HPV16 E7-targeted DNA vaccine pNGVL4a-SigE7(detox)HSP70 (DNA vaccine pBI-1). Codon optimization of the HPV16/18 E6/E7 genes in pBI-11 improved fusion protein expression compared to that in DNA vaccine pBI-10.1 that utilized the native viral sequences fused 3' to a signal sequence and 5' to the HSP70 gene of Mycobacterium tuberculosis Intramuscular vaccination of mice with pBI-11 DNA better induced HPV antigen-specific CD8+ T cell immune responses than pBI-10.1 DNA. Furthermore, intramuscular vaccination with pBI-11 DNA generated stronger therapeutic responses for C57BL/6 mice bearing HPV16 E6/E7-expressing TC-1 tumors. The HPV16/18 antigen-specific T cell-mediated immune responses generated by pBI-11 DNA vaccination were further enhanced by boosting with tissue-antigen HPV vaccine (TA-HPV). Combination of the pBI-11 DNA and TA-HPV boost vaccination with PD-1 antibody blockade significantly improved the control of TC-1 tumors and extended the survival of the mice. Finally, repeat vaccination with clinical-grade pBI-11 with or without clinical-grade TA-HPV was well tolerated in vaccinated mice. These preclinical studies suggest that the pBI-11 DNA vaccine may be used with TA-HPV in a heterologous prime-boost strategy to enhance HPV 16/18 E6/E7-specific CD8+ T cell responses, either alone or in combination with immune checkpoint blockade, to control HPV16/18-associated tumors. Our data serve as an important foundation for future clinical translation.IMPORTANCE Persistent expression of high-risk human papillomavirus (HPV) E6 and E7 is an obligate driver for several human malignancies, including cervical cancer, wherein HPV16 and HPV18 are the most common types. PD-1 antibody immunotherapy helps a subset of cervical cancer patients, and its efficacy might be improved by combination with active vaccination against E6 and/or E7. For patients with HPV16+ cervical intraepithelial neoplasia grade 2/3 (CIN2/3), the precursor of cervical cancer, intramuscular vaccination with a DNA vaccine targeting HPV16 E7 and then a recombinant vaccinia virus expressing HPV16/18 E6-E7 fusion proteins (TA-HPV) was safe, and half of the patients cleared their lesions in a small study (NCT00788164). Here, we sought to improve upon this therapeutic approach by developing a new DNA vaccine that targets E6 and E7 of HPV16 and HPV18 for administration prior to a TA-HPV booster vaccination and for application against cervical cancer in combination with a PD-1-blocking antibody.

Twenty years of research on HPV vaccines based on genetically modified lactic acid bacteria: an overview on the gut-vagina axis

Most cervical cancer (CxCa) are related to persistent infection with high-risk human papillomavirus (HR-HPV) in the cervical mucosa, suggesting that an induction of mucosal cell-mediated immunity against HR-HPV oncoproteins can be a promising strategy to fight HPV-associated CxCa. From this perspective, many pre-clinical and clinical trials have proved the potential of lactic acid bacteria (LAB) genetically modified to deliver recombinant antigens to induce mucosal, humoral and cellular immunity in the host. Altogether, the outcomes of these studies suggest that there are several key factors to consider that may offer guidance on improvement protein yield and improving immune response. Overall, these findings showed that oral LAB-based mucosal HPV vaccines expressing inducible surface-anchored antigens display a higher potential to induce particularly specific systemic and mucosal cytotoxic cellular immune responses. In this review, we describe all LAB-based HPV vaccine investigations by reviewing databases from international studies between 2000 and 2020. Our aim is to promote the therapeutic HPV vaccines knowledge and to complete the gaps in this field to empower scientists worldwide to make proper decisions regarding the best strategies for the development of therapeutic HPV vaccines.

Targeting Head and Neck Cancer by Vaccination

Head and neck cancer (HNC) is a heterogeneous group of squamous cell cancers that affect the oral cavity, pharynx, and larynx. Worldwide, it is the sixth most common cancer but in parts of Southern and South-East Asia, HNC is one of the most common cancers. A significant proportion of HNC is driven by human papillomavirus (HPV) infection, whereas HPV-independent HNC is associated with alcohol, smoking, and smokeless tobacco consumption. Here, we review the past and present experience of targeting HNC with vaccination focusing on HPV-derived antigens as well as non-viral antigens for HPV-negative HNC. Novel therapeutic approaches for HNC will focus not only on effective vaccine platforms but will also target the stroma-rich immunosuppressive microenvironment found in those tumours.

Taking a Stab at Cancer; Oncolytic Virus-Mediated Anti-Cancer Vaccination Strategies

Vaccines have classically been used for disease prevention. Modern clinical vaccines are continuously being developed for both traditional use as well as for new applications. Typically thought of in terms of infectious disease control, vaccination approaches can alternatively be adapted as a cancer therapy. Vaccines targeting cancer antigens can be used to induce anti-tumour immunity and have demonstrated therapeutic efficacy both pre-clinically and clinically. Various approaches now exist and further establish the tremendous potential and adaptability of anti-cancer vaccination. Classical strategies include ex vivo-loaded immune cells, RNA- or DNA-based vaccines and tumour cell lysates. Recent oncolytic virus development has resulted in a surge of novel viruses engineered to induce powerful tumour-specific immune responses. In addition to their use as cancer vaccines, oncolytic viruses have the added benefit of being directly cytolytic to cancer cells and thus promote antigen recognition within a highly immune-stimulating tumour microenvironment. While oncolytic viruses are perfectly equipped for efficient immunization, this complicates their use upon previous exposure. Indeed, the host's anti-viral counter-attacks often impair multiple-dosing regimens. In this review we will focus on the use of oncolytic viruses for anti-tumour vaccination. We will explore different strategies as well as ways to circumvent some of their limitations.

Development of HPV Vaccines for HPV-associated Head and Neck Squamous Cell Carcinoma

High-risk genotypes of the human papillomavirus (HPV), particularly HPV type 16, are found in a distinct subset of head and neck squamous cell carcinomas (HNSCC). Thus, these HPV-associated HNSCC may be prevented or treated by vaccines designed to induce appropriate HPV virus-specific immune responses. Infection by HPV may be prevented by neutralizing antibodies specific for the viral capsid proteins. In clinical trials, vaccines comprised of HPV virus-like particles (VLPs) have shown great promise as prophylactic HPV vaccines. However, given that capsid proteins are not expressed at detectable levels by infected basal keratinocytes, vaccines with therapeutic potential must target other non-structural viral antigens. Two HPV oncogenic proteins, E6 and E7, are important in the induction and maintenance of cellular transformation and are co-expressed in the majority of HPV-containing carcinomas. Therefore, therapeutic vaccines targeting these proteins may have potential to control HPV-associated malignancies. Various candidate therapeutic HPV vaccines are currently being tested whereby E6 and/or E7 is administered in live vectors, in peptides or protein, in nucleic acid form, as components of chimeric VLPs, or in cell-based vaccines. Encouraging results from experimental vaccination systems in animal models have led to several prophylactic and therapeutic vaccine clinical trials. Should they fulfill their promise, these vaccines may prevent HPV infection or control its potentially life-threatening consequences in humans.

Intratumoral injection of therapeutic HPV vaccinia vaccine following cisplatin enhances HPV-specific antitumor effects

Despite the conventional treatments of radiation therapy and chemotherapy, the 5-year survival rates for patients with advanced-stage cervical cancers remain low. Cancer immunotherapy has emerged as an alternative, innovative therapy that may improve survival. Here, we utilize a preclinical HPV-16 E6/E7-expressing tumor model, TC-1, and employ the chemotherapeutic agent cisplatin to generate an accumulation of CD11c+ dendritic cells in tumor loci making it an ideal location for the administration of therapeutic vaccines. Following cisplatin treatment, we tested different routes of administration of a therapeutic HPV vaccinia vaccine encoding HPV-16 E7 antigen (CRT/E7-VV). We found that TC-1 tumor-bearing C57BL/6 mice treated with cisplatin and intratumoral injection of CRT/E7-VV significantly increased E7-specific CD8+ T cells in the blood and generated potent local and systemic antitumor immune responses compared to mice receiving cisplatin and CRT/E7-VV intraperitoneally or mice treated with cisplatin alone. We further extended our study using a clinical grade recombinant vaccinia vaccine encoding HPV-16/18 E6/E7 antigens (TA-HPV). We found that intratumoral injection with TA-HPV following cisplatin treatment also led to increased E7-specific CD8+ T cells in the blood as well as significantly decreased tumor size compared to intratumoral injection with wild type vaccinia virus. Our study has strong implications for future clinical translation using intratumoral injection of TA-HPV in conjunction with the current treatment strategies for patients with advanced cervical cancer.

Immunotherapy against HPV16/18 generates potent TH1 and cytotoxic cellular immune responses

Despite the development of highly effective prophylactic vaccines against human papillomavirus (HPV) serotypes 16 and 18, prevention of cervical dysplasia and cancer in women infected with high-risk HPV serotypes remains an unmet medical need. We report encouraging phase 1 safety, tolerability, and immunogenicity results for a therapeutic HPV16/18 candidate vaccine, VGX-3100, delivered by in vivo electroporation (EP). Eighteen women previously treated for cervical intraepithelial neoplasia grade 2 or 3 (CIN2/3) received a three-dose (intramuscular) regimen of highly engineered plasmid DNA encoding HPV16 and HPV18 E6/E7 antigens followed by EP in a dose escalation study (0.3, 1, and 3 mg per plasmid). Immunization was well tolerated with reports of mild injection site reactions and no study-related serious or grade 3 and 4 adverse events. No dose-limiting toxicity was noted, and pain was assessed by visual analog scale, with average scores decreasing from 6.2/10 to 1.4 within 10 min. Average peak interferon-γ enzyme-linked immunospot magnitudes were highest in the 3 mg cohort in comparison to the 0.3 and 1 mg cohorts, suggesting a trend toward a dose effect. Flow cytometric analysis revealed the induction of HPV-specific CD8(+) T cells that efficiently loaded granzyme B and perforin and exhibited full cytolytic functionality in all cohorts. These data indicate that VGX-3100 is capable of driving robust immune responses to antigens from high-risk HPV serotypes and could contribute to elimination of HPV-infected cells and subsequent regression of the dysplastic process.

Back to the future: learning from cancer vaccine trials in Cardiff

The early 1990s saw the first clinical testing of several therapeutic cancer vaccines. There was great optimism that these vaccines could be used as an alternative therapy for patients who had failed to respond to conventional cancer therapies. This article provides a personal perspective on the cancer vaccine field after being involved with a series of clinical trials in the United Kingdom (Cardiff) starting in the mid 1990s. It will also review the developments in technology and improved knowledge of the immune system that have informed the design of a new generation of cancer vaccine trials that will start in Cardiff in 2012.

Biolistic DNA vaccination against cervical cancer

The development of cervical cancer is associated with infection by oncogenic human papillomaviruses (HPVs), of which type 16 (HPV16) is the most prevalent in HPV-induced malignant diseases. The viral oncoproteins E6 and E7 are convenient targets for anti-tumor immunization. To adapt the corresponding genes for DNA vaccination, their oncogenicity needs to be reduced and immunogenicity enhanced. The main modifications for achieving these aims include mutagenesis, rearrangement of gene parts, and fusion with supportive cellular or viral/bacterial genes or their functional parts. As HPVs are strictly human specific, an animal model of HPV infection does not exist. Therefore, immunization against HPV-induced tumors is most frequently tested in mouse models utilizing transplantable syngeneic tumor cells producing the HPV16 E6/E7 oncoproteins. In this chapter, one such cell line designated TC-1 is characterized and the effect of immunization with the modified E7 fusion gene against TC-1-induced subcutaneous tumors is described. As down-regulation of MHC class I molecules is one of the most important escape mechanisms of cervical carcinoma cells, the TC-1/A9 clone with reversibly reduced MHC class I expression has been developed and, herein, its response to DNA vaccination is also shown and compared with that of the TC-1 cells.

Preventive and Therapeutic Vaccines against Human Papillomaviruses Associated Cervical Cancers

Cervical cancer is, globally known to be, one of the most common cancers among women especially in developing countries. More than 90% of cervical cancers are associated with high-risk human papillomaviruses (HPVs) particularly HPV types 16 and 18. Two major strategies have been developed for prevention and treatment of cervical cancer and other HPV-associated malignancies; the first one is based on HPV virus-like particles (VLPs) containing HPV structural proteins. VLP based vaccines can induce genotype specific virus neutralizing antibodies for preventing HPV infections. The other strategy is based on HPV early genes especially E6 and E7 for eliminating the established HPV infections; therefore they are classified as HPV therapeutic vaccines. This article reviews the preventive and therapeutic vaccines against HPV infections and cervical cancer.

Immunogenicity in mice and rhesus monkeys vaccinated with recombinant vaccinia virus expressing bivalent E7E6 fusion proteins from human papillomavirus types 16 and 18

BACKGROUND

Persistent infection with high-risk human papillomavirus (HPV) is a predominant cause of cervical cancer, and HPV16 and HPV18 occur in 50% and 20% of cervical cancer cases, respectively. The viral oncogenes E6 and E7 are constitutively expressed by HPV-associated tumour cells and can therefore be used as target antigens for immunotherapy. In this study, we constructed a recombinant vaccinia virus co-expressing the HPV16/18 E7E6 fusion proteins (rVVJ16/18E7E6) for use as a therapeutic vaccine for the treatment of HPV16⁺ and HPV18⁺ cancers.

METHODS

We constructed a bivalent recombinant vaccinia virus expressing modified E7E6 fusion proteins of HPV type 16 and 18 (rVVJ16/18E7E6) based on the vaccinia virus Tiantan strain. We then defined the cellular immune responses to the virus in mice and rhesus monkeys and assessed antitumour efficacy of these responses in mice using the TC-1 tumour challenge model.

RESULTS

Our data demonstrated that rVVJ16/18E7E6 was able to elicit varying levels of CD8⁺ T cell immune responses and lysis of target cells in mice in response to peptides HPV16E7₄₉₋₅₇ and HPV18E6₆₇₋₇₅. Furthermore, the virus was also able to induce anti-tumour responses in the HPV16⁺ TC-1 tumour challenge model, including partial protection (30-40%) and delayed tumour appearance. In addition, the virus was able to induce immune responses in rhesus monkeys.

CONCLUSIONS

The recombinant vaccinia virus rVVJ16/18E7E6 can generate clear and significant cellular immunity in both mice and rhesus monkeys. These data provide a basis for the use of this recombinant virus as a potential vaccine candidate for further study.

Long-term protection against human papillomavirus e7-positive tumor by a single vaccination of adeno-associated virus vectors encoding a fusion protein of inactivated e7 of human papillomavirus 16/18 and heat shock protein 70

We investigated a gene vaccine strategy against human papillomavirus (HPV)-induced cancer and premalignant diseases, using adeno-associated virus (AAV) vector encoding the viral E7 oncoproteins as the tumor antigens from HPV serotypes 16 (HPV16) and 18 (HPV18). Genetically inactivated E7 proteins were fused with a heat shock protein 70 (hsp70) to minimize the risk of cell transformation and enhance immune responses. The fusion protein gene was packaged in AAV serotype 1 or 2 (AAV1 or 2) for efficient in vivo gene expression. Our results showed that after a single intramuscular injection, the AAV1 vector elicited stronger HPV-specific cytotoxic T lymphocyte (CTL) responses and interferon-gamma secretion when compared with the AAV2 vector. Prophylactic immunization with AAV1 protected 100% of the mice from tumor growth for more than 1 year, whereas all the control mice immunized with either a LacZ vector or saline grew large tumors and died within 6 weeks after inoculation of E7-positive tumor cell line TC-1. In addition, this single-dose AAV1 vaccination completely protected the mice against second and third challenges with higher numbers of TC-1 cells. Despite lower CTL responses against the E7 antigens, AAV2 vector prophylactic immunization was also sufficient to protect 100% of the mice against the initial and second tumor challenges and 70% of the mice against the third challenge. In addition, therapeutic immunization with AAV1 after palpable tumor formation inhibited tumor growth and caused tumor regression in some mice. Thus, our studies support the potential of AAV vectors as a genetic vaccine for the prevention and treatment of HPV-induced malignancies.

DNA vaccines for cervical cancer

Human papillomavirus (HPV), particularly type 16, has been associated with more than 99% of cervical cancers. There are two HPV oncogenic proteins, E6 and E7, which play a major role in the induction and maintenance of cellular transformation. Thus, immunotherapy targeting these proteins may be employed for the control of HPV-associated cervical lesions. Although the commercially available preventive HPV vaccines are highly efficient in preventing new HPV infection, they do not have therapeutic effects against established HPV infection or HPV-associated lesions. Since T cell-mediated immunity is important for treating established HPV infections and HPV-associated lesions, therapeutic HPV vaccine should aim at generating potent E6 and E7-specific T cell-mediated immune responses. DNA vaccines have now developed into a promising approach for antigen-specific T cell-mediated immunotherapy to combat infection and cancer. Because dendritic cells are the most potent professional antigen-presenting cells, and are highly effective in priming antigen-specific T cells, several DNA vaccines have employed innovative strategies to modify the properties of dendritic cells (DCs) for the enhancement of the DNA vaccine potency. These studies have revealed impressive pre-clinical data that has led to several ongoing HPV DNA vaccine clinical trials.

Construction and characterization of recombinant fowlpox viruses expressing human papilloma virus E6 and E7 oncoproteins

Human papilloma virus (HPV)-16 is the most prevalent high-risk mucosal genotype and the expression of the E6 and E7 proteins, which can bind to the p53 and p105Rb host cell-cycle regulatory proteins, is related to its tumorigenicity. Virus-like-particle (VLP)-based immunogens developed recently are successful as prophylactic HPV vaccines. However, given the high number of individuals infected already with HPV and the absence of expression of the L1 structural protein in HPV-infected or HPV-transformed cells, an efficient therapeutic vaccine targeting the non-structural E6 and E7 oncoproteins is required. In this study, two new fowlpox virus (FPV) recombinants encoding the HPV-16 E6 and E7 proteins were engineered and evaluated for their correct expression in vitro, with the final aim of developing a therapeutic vaccine against HPV-related cervical tumors. Although vaccinia viruses expressing the HPV-16 and HPV-18 E6 and E7 oncoproteins have already been studied, due to their natural host-range restriction to avian species and their ability to elicit a complete immune response, FPV recombinants may represent efficient and safer vectors also for immunocompromised hosts. The results indicate that FPV recombinants can express correctly the E6 and E7 oncoproteins, and they should represent appropriate vectors for the expression of these oncoproteins in human cells.

Induction of antitumor immunity in vivo following delivery of a novel HPV-16 DNA vaccine encoding an E6/E7 fusion antigen

Human papillomavirus type 16 (HPV-16) infection is associated with a majority of cervical cancers and a significant proportion of head and neck cancers. Here, we describe a novel-engineered DNA vaccine that encodes a HPV-16 consensus E6/E7 fusion gene (pConE6E7) with the goal of increasing its antitumor cellular immunity. Compared to an early stage HPV-16 E7 DNA vaccine (pE7), this construct was up to five times more potent in driving E7-specific cellular immune responses. Prophylactic administration of this vaccine resulted in 100% protection against HPV E6 and E7-expressing tumors. Therapeutic studies indicated that vaccination with pConE6E7 prevented or delayed the growth of tumors. Moreover, immunization with pConE6E7 could also partially overcome immune tolerance in E6/E7 transgenic mice. Such DNA immunogens are interesting candidates for further study to investigate mechanisms of tumor immune rejection in vivo.

DNA vaccines for cervical cancer: from bench to bedside

More than 99% of cervical cancers have been associated with human papillomaviruses (HPVs), particularly HPV type 16. The clear association between HPV infection and cervical cancer indicates that HPV serves as an ideal target for development of preventive and therapeutic vaccines. Although the recently licensed preventive HPV vaccine, Gardasil, has been shown to be safe and capable of generating significant protection against specific HPV types, it does not have therapeutic effect against established HPV infections and HPV-associated lesions. Two HPV oncogenic proteins, E6 and E7, are consistently co-expressed in HPV-expressing cervical cancers and are important in the induction and maintenance of cellular transformation. Therefore, immunotherapy targeting E6 and/or E7 proteins may provide an opportunity to prevent and treat HPV-associated cervical malignancies. It has been established that T cell-mediated immunity is one of the most crucial components to defend against HPV infections and HPV-associated lesions. Therefore, effective therapeutic HPV vaccines should generate strong E6/E7-specific T cell-mediated immune responses. DNA vaccines have emerged as an attractive approach for antigen-specific T cell-mediated immunotherapy to combat cancers. Intradermal administration of DNA vaccines via a gene gun represents an efficient way to deliver DNA vaccines into professional antigen-presenting cells in vivo. Professional antigen-presenting cells, such as dendritic cells, are the most effective cells for priming antigen-specific T cells. Using the gene gun delivery system, we tested several DNA vaccines that employ intracellular targeting strategies for enhancing MHC class I and class II presentation of encoded model antigen HPV-16 E7. Furthermore, we have developed a strategy to prolong the life of DCs to enhance DNA vaccine potency. More recently, we have developed a strategy to generate antigen-specific CD4(+) T cell immune responses to further enhance DNA vaccine potency. The impressive pre- clinical data generated from our studies have led to several HPV DNA vaccine clinical trials.

Cellular immunity induced by a novel HPV18 DNA vaccine encoding an E6/E7 fusion consensus protein in mice and rhesus macaques

Human papilloma-virus (HPV) infection is the major cause of cervical cancer. HPV18 is the most prevalent high-risk HPV after type 16 that accounts for the largest number of cervical cancer cases worldwide. Currently, although prophylactic vaccines have been developed, there is still an urgent need to develop therapeutic HPV vaccines for targeting tumors post-infection. In this study, we utilize a novel multi-phase strategy for HPV18 antigen development with the goal of increasing anti-HPV18 cellular immunity. Our data show that this construct can induce strong cellular immune responses against HPV18 E6 and E7 antigens in a murine model. Moreover, when applied to rhesus monkeys, this construct is also able to elicit cellular immunity. These data suggest such DNA immunogens are candidates for further study in the eventual context of immunotherapy for HPV-associated cancers.

[Human papillomavirus and cervical cancer]

Human papillomavirus (HPV) is a small non-enveloped icosahedral virus with a circular double-stranded DNA genome of 8 kilo base pairs. HPV particles reach and infect the basal cells of the stratified epithelia through small epithelial lesions. In the basal cells the viral DNA is maintained as episomes, which start to replicate when the host cells initiate terminal differentiation. In these differentiating cells the degradation of p53 by the E6 protein and the abrogation of the pRb functions by the E7 protein lead to the reactivation of the DNA synthesis machinery. After virus propagation the host cells usually die. On the other hand, in some of the infected cells, the E6 and E7 genes are integrated on rare occasion into cell DNA. The cell continuously expressing the E6 and E7 proteins from the integrated genes is immortalized and sometimes acquires malignant phenotype induced by the accumulated damages to DNA. Of more than 100 HPV genotypes recorded to date, 13 including types 16 and 18 are associated with cervical cancer. Expression of HPV major capsid protein L1 in some cultured cells results in production of virus-like particles (VLPs). The VLPs of types 6, 11, 16, and 18 were used as a prophylactic vaccine in recent clinical trials and shown to successfully induce type-specific neutralizing antibodies in the recipients.

Probing the low-frequency vibrational modes of viruses with Raman scattering--bacteriophage M13 in water

Raman spectroscopy is used to study low-wave-number (</=20 cm(-1)) acoustic vibrations of the M13 phage. A well-defined Raman line is observed at around 8.5 cm(-1). The experimental results are compared with theoretical calculations based on an elastic continuum model and appropriate Raman selection rules derived from a bond polarizability model. The observed Raman mode is shown to belong to one of the Raman-active axial modes of the M13 phage protein coat. It is expected that the detection and characterization of this low-frequency vibrational mode can be used for applications in biomedical nanotechnology such as for monitoring the process of virus functionalization and self-assembly.

Activated B cells mediate efficient expansion of rare antigen-specific T cells

Potent professional antigen-presenting cells (APC) are essential tools to activate and expand antigen-specific T cells in vitro for use in adoptive immunotherapy. CD40-activated B cells can be easily generated and propagated from human donors and have been successfully used to generate antigen-specific T-cell cultures. Here we show that CD40-activated B cells strongly and specifically expand rare populations of antigen-specific CD8 T cells, with frequencies of less than 1 in 20,000 CD8 T cells in peripheral blood. We focused on T cells recognizing an epitope from the human papillomavirus 16 (HPV-16) E7 protein. In 6 of 6 healthy donors, epitope-specific CD8+ T cells were found to be "rare" by this criterion, as shown by staining with human leukocyte antigen (HLA)/peptide multimers. Using peptide-loaded CD40-activated B cells, epitope-specific T cells could be selectively expanded in all donors up to 10(6) fold, and the resulting T-cell cultures contained up to 88% specific T cells. These results strongly encourage the use of CD40-stimulated B cells as APCs in immunotherapy.

HLA class I binding promiscuity of the CD8 T-cell epitopes of human papillomavirus type 16 E6 protein

One of the critical steps in the progression to cervical cancer appears to be the establishment of persistent human papillomavirus (HPV) infection. We have demonstrated that the lack of cytotoxic T-lymphocyte response to HPV type 16 (HPV 16) E6 protein was associated with persistence and that the potential presence of dominant CD8 T-cell epitopes was most frequently found (n = 4 of 23) in the E6 16-40 region by examining the pattern of CD8 T-cell epitopes within the E6 protein in women who had cleared their HPV 16 infections. The goal of this study was to define the minimal/optimal amino acid sequences and the HLA restricting molecules of these dominant CD8 T-cell epitopes as well as those of subdominant ones if present. Three dominant epitopes, E6 29-38 (TIHDIILECV; restricted by the HLA-A0201 molecule), E6 29-37 (TIHDIILEC; restricted by B48), and E6 31-38 (HDIILECV; restricted by B4002), and one subdominant epitope, E6 52-61 (FAFRDLCIVY; restricted by B35) were characterized. Taken together with a previously described dominant epitope, E6 52-61 (FAFRDLCIVY; restricted by B57), the CD8 T-cell epitopes demonstrated striking HLA class I binding promiscuity. All of these epitopes were endogenously processed, but the presence of only two of the five epitopes could have been predicted based on the known binding motifs. The HLA class I promiscuity which has been described for human immunodeficiency virus may be more common than previously recognized.

Codon optimized expression of HPV 16 E6 renders target cells susceptible to E6-specific CTL recognition

The early proteins E6 and E7 of the cancer-related human papillomavirus type 16 (HPV 16) are constitutively expressed in cancer cells thus are targets for immune therapeutic approaches. Whereas previous studies have mainly focussed on the immunogenicity of E7 protein little is known about E6. In order to evaluate E6-specific DNA immunization strategies in a preclinical mouse model C57BL/6 mice were injected with plasmid pTHampE6 and analyzed for E6-specific CTL induction. CTL specific for the H2-K(b)-restricted E6-derived epitope E6 48-57, were readily detectable among splenocytes of immunized animals, however, these CTL showed a differential recognition pattern on various E6-expressing target cells. Using a newly generated E6-specific monoclonal antibody we found that most cell lines expressing E6 encoded by the natural gene showed undetectable protein amounts and were ignored by E6-specific CTL. However, transfection of a codon optimized version of the E6 gene (E6opt) strongly enhanced protein expression levels within these cells turning them into susceptible target cells. Surprisingly, we found that E6-positive TC-1 cells, although recognized by E6-specific CTL, were totally devoid of any detectable E6 protein. Inhibition of proteasomal function by lactacystin treatment diminished E6-specific CTL recognition of TC-1 cells and RMA/E6opt transfectants accompanied by intracellular accumulation of E6 protein as observed in RMA/E6opt transfectants, but not in TC-1 cells. These data suggest that in TC-1 cells rapid degradation processes might prevent stable expression of E6 protein yet generate precursor peptides in amounts sufficient for MHC class I restricted antigen presentation. Thus, the results presented in this paper show that: (i) use of optimized codons in transfection experiments can improve susceptibility of target cells to E6-specific CTL recognition and (ii) lack of detectable protein within a cell does not necessarily indicate the absence of epitope presentation. Both findings are of potential relevance for the design of tumor vaccines.

Plasmid encoding papillomavirus Type 16 (HPV16) DNA constructed with codon optimization improved the immunogenicity against HPV infection

Human papillomavirus Type 16 (HPV16) infections can cause neoplasia, which is thought to be closely associated with the development of cervical cancers. In the study, we attempted to construct a DNA plasmid encoding a HPV16 capsid protein (L1) and a HPV16 oncoprotein (E7), which was capable of preventing HPV16 infection and eliminating HPV16-infected cells. A plasmid, L1E7hpSCA1, encoding the L1 and E7 genes with the codon usage optimized for mammalian cell expression, was constructed. Mutations were introduced into the E7 gene sequence for reducing its oncogenicity. C57BL/6 mice were intramuscularly immunized at tibialis anterior (TA) muscles with the newly constructed L1E7hpSCA1 plasmid. The immune responses induced by the L1E7hpSCA1 plasmid (with codon optimization) and a control L1E7pSCA1 plasmid (without codon optimization) were compared. It is shown that the L1E7hpSCA1 was able to induce much stronger immune responses than the L1E7pSCA1. Sera obtained from immunized animals were found to contain anti-HPV16 antibodies as detected by ELISA and hemagglutination inhibition (HAI) assays. Cytotoxicity and interferon-gamma assays showed that spleenocytes from immunized animals were able to recognize and lyze E7 expressing tumor TC-1 cells. Moreover, the growth of E7 expressing tumor mass was inhibited in vaccinated mice. In vivo tumor protection test indicated that tumor formation was prevented in the experimental animals (67%) after vaccination with L1E7hpSCA1, while for the control group injected with L1E7pSCA1 only and the animal group injected with pSCA1 only, tumor formation was observed in all experimental animals. Our results suggest that the L1E7h gene (with codon optimization) is more effective against HPV16 than the L1E7 gene (without codon optimization). The L1E7hpSCA1 plasmid was able to provide protection against E7 expressing tumor, and it might have the potential to be a vaccine candidate for HPV prevention.

Immunization with adenoviral vectors carrying recombinant IL-12 and E7 enhanced the antitumor immunity to human papillomavirus 16-associated tumor

OBJECTIVE

Human papillomavirus (HPV) infection play a significant role in cervical carcinogenesis, and HPV oncoprotein E7 has important functions in the formation and maintenance of cervical cancers. Interleukin-12 (IL-12) has been reported to induce cellular immune responses, and has also been demonstrated to suppress the growth of tumors and the expression of E7. Here, we investigate the utility of adenovirus E7 (AdE7) and adenovirus IL-12 (AdIL-12) for protection against TC-1 tumor using an animal model.

METHODS

The antitumor effects induced by AdIL-12 and/or E7 were assessed by measurements of tumor size. E7-specific antibody and INF-gamma production in sera were measured, as were T-helper cell proliferative responses. Cytotoxic T-lymphocytes (CTL) and T cell subset depletion studies were also performed.

RESULTS

Infection of tumor sites with a combination of AdIL-12 and AdE7 resulted in an antitumor effect which was significantly more profound than that which resulted from singular infections with either AdIL-12 or AdE7. Combined infection resulted in regression of 9-mm-sized tumors in approximately 80% of our experimental animals as compared to the PBS group. Serum levels of E7-specific antibody and INF-gamma production, as well as T-helper cell proliferative responses, were found to be significantly higher in coinfected with AdIL-12 and AdE7 group than in single infection with either AdIL-12 or AdE7 group. CTL responses only exhibited by the AdIL-12 and AdE7 coinjected group suggested that these tumor suppression effects were mediated primarily by CD8+ and, to a lesser degree, by CD4+ T cells.

CONCLUSION

Combined injection with adenovirus carrying IL-12 and E7 induced significant antitumor immunity against TC-1 tumors. They may prove useful in clinical applications for the treatment of HPV-associated tumors.

Cross-typic specificity and immunotherapeutic potential of a human HPV16 E7-specific CTL line

Cervical cancer (CaCx) is strongly associated with human papillomavirus (HPV) infection, particularly HPV types 16 and 18. The constitutive expression of HPV E6 and E7 proteins in CaCx makes them attractive targets for CTL based immunotherapy. However cervical carcinomas may have features, e.g., antigen processing defects, that limit the effectiveness of HPV specific CTL. Furthermore most vaccine development has concentrated on HPV type 16, and it is not clear whether such vaccines could induce CTL able to cross‐react on related oncogenic HPV types, e.g., HPV31 and 52. To investigate these potentially important parameters in vitro, we used a CTL (D4) specific for HPV16 E7_11–20. D4 was able to kill a variety of HPV16+ CaCx cell lines including those with suspected (CaSki) or known antigen processing defects (C33A), and with low HPV DNA copy number (SiHa). D4 was also able to cross react on a related peptide from HPV52 E7 but not HPV31 E7. Further analysis suggested that D4 cross reactivity against related peptides was influenced both by TCR contact residues and a certain threshold for peptide binding. The HPV cross‐reactivity was confirmed at the whole protein level as D4 was also able to recognize the endogenously processed forms of HPV16 and 52 E7 but not 31 E7. These results suggest that HPV16 E7_11–20 would be a useful epitope for immunotherapy in both HPV 16 and 52 tumours. Despite this, it is difficult to generate these CTL in response to vaccination, emphasizing the need for definition of novel epitopes and more efficient vaccination strategies. © 2005 Wiley‐Liss, Inc.

Immunization with adenoviral vectors carrying recombinant IL-12 and E7 enhanced the antitumor immunity against human papillomavirus 16-associated tumor

PURPOSE

Human papillomavirus (HPV) infection has a significant role in cervical carcinogenesis, and HPV oncoprotein E7 plays an important part in the formation and maintenance of cervical cancer. Interleukin-12 (IL-12) has been reported to induce a cellular immune response, and to suppress the tumor growth and the E7 production. Here we describe the use of adenoviral delivery of the HPV 16 E7 subunit (AdE7) along with adenoviral delivery of IL-12 (AdIL-12) in mice with HPV-associated tumors.

MATERIALS AND METHODS

Mice were injected with TC-1 cells to establish TC-1 tumor, and then they were immunized with AdIL-12 and/or AdE7 intratumorally. The anti tumor effects induced by AdIL-12 and/or E7 were evaluated by measuring the size of the tumor. E7-specific antibody and INF-gamma production in sera, and the T-helper cell proliferative responses were then measured. Cytotoxic T-lymphocyte (CTL) and T cell subset depletion studies were also performed.

RESULTS

Combined AdIL-12 and AdE7 infection at the tumor sites significantly enhanced the antitumor effects more than that of AdIL-12 or AdE7 single infection. This combined infection resulted in regression of the 9 mm sized tumors in 80% of animals as compare to the PBS group. E7-specific antibody and INF-gamma production in the sera, and the T-helper cell proliferative responses were significantly higher with coinfection of AdIL-12 and AdE7 than with AdIL-12 or AdE7 alone. CTL response induced by AdIL-12 and AdE7 in the coinjected group suggested that tumor suppression was mediated by mostly CD8+ and only a little by the CD4+ T cells.

CONCLUSION

IL-12 and E7 application using adenovirus vector showed antitumor immunity effects against TC-1 tumor, and this system could be use in clinical applications for HPV-associated cancer.

Activation of CD40 in Cervical Carcinoma Cells Facilitates CTL Responses and Augments Chemotherapy-Induced Apoptosis

In this study, we describe the expression and function of CD40, a TNF receptor family member, in cervical carcinomas. CD40 was present at very low levels in normal cervical epithelium but was overexpressed in human papillomavirus-infected lesions and advanced squamous carcinomas of the cervix. The stimulation of CD40-positive cervical carcinoma cell lines with soluble CD40L (CD154) resulted in activation of the NF-kappaB and MAPK signaling pathways and up-regulation of cell surface markers and intracellular molecules associated with Ag processing and presentation. Concomitantly, the CD154-induced activation of CD40 in carcinoma cells was found to directly influence susceptibility to CTL-mediated killing. Thus, CD40 stimulation in cervical carcinoma cell lines expressing a TAP-dependent human papillomavirus 16 E6 Ag epitope resulted in their enhanced killing by specific CTLs. However, CD154 treatment of carcinoma cells expressing proteasome-dependent but TAP-independent Ags from the EBV-encoded BRLF1 and BMLF1 failed to increase tumor cell lysis by specific CTLs. Moreover, we demonstrate that chemotherapeutic agents that suppress protein synthesis and reverse the CD40-mediated dissociation of the translational repressor eukaryotic initiation factor 4E-binding protein from the initiation factor eukaryotic initiation factor 4E, such as 5-fluorouracil, etoposide, and quercetin, dramatically increase the susceptibility of cervical carcinoma cells to CD40L-induced apoptosis. Taken together, these observations demonstrate the functional expression of CD40 in epithelial tumors of the cervix and support the clinical exploitation of the CD40 pathway for the treatment of cervical cancer through its multiple effects on tumor cell growth, apoptosis, and immune recognition.

Preventative and therapeutic vaccines for cervical cancer

"High-risk" genotypes of the human papillomavirus (HPV), most commonly HPV genotype 16, are the primary etiologic agents of cervical cancer. Indeed HPV DNA is detected in 99% of cervical carcinomas. Thus, cervical cancer and other HPV-associated malignancies might be prevented or treated by the induction of the appropriate viral-antigen-specific immune responses. Transmission of papillomavirus may be prevented by the generation of antibodies to capsid proteins L1 and L2 that neutralize viral infection. HPV L1 virus-like particles (VLPs) show great promise as prophylactic HPV vaccines in ongoing clinical trials but L2-based preventative vaccines have yet to be tested in patients. Since the capsid proteins are not expressed at detectable levels by infected basal keratinocytes or in HPV-transformed cells, therapeutic vaccines generally target the nonstructural early viral antigens. Two HPV oncogenic proteins, E6 and E7, are critical to the induction and maintenance of cellular transformation and are co-expressed in the majority of HPV-containing carcinomas. Although other early viral antigens show promise for vaccination against papillomas, therapeutic vaccines targeting E6 and E7 may provide the best opportunity to control HPV-associated malignancies. Various candidate therapeutic HPV vaccines are currently being tested whereby E6 and/or E7 are administered in live vectors, as peptides or proteins, in nucleic acid form, as components of chimeric VLPs, or in cell-based vaccines. Encouraging results from experimental vaccination systems in animal models have led to several prophylactic and therapeutic vaccine clinical trials. Should this new generation of HPV preventative and therapeutic vaccines function in patients as demonstrated in animal models, oncogenic HPV infection and its associated malignancies could be controlled by vaccination. Importantly, recent advances in HPV detection and continued improvements in screening further enhance our opportunities to systematically eradicate HPV-associated malignancy.

Vaccination to prevent and treat cervical cancer

Human papillomaviruses (HPVs) are the primary etiologic agents of cervical cancer. Thus, cervical cancer and other HPV-associated malignancies might be prevented or treated by HPV vaccines. Transmission of papillomavirus may be prevented by the generation of antibodies to capsid proteins L1 and L2 that neutralize viral infection. However, because the capsid proteins are not expressed at detectable levels by infected basal keratinocytes or in HPV-transformed cells, therapeutic vaccines generally target nonstructural early viral antigens. Two HPV oncogenic proteins, E6 and E7, are critical to the induction and maintenance of cellular transformation and are coexpressed in the majority of HPV-containing carcinomas. Thus, therapeutic vaccines targeting E6 and E7 may provide the best option for controlling HPV-associated malignancies. Various candidate therapeutic HPV vaccines are currently being tested whereby E6 and/or E7 are administered in live vectors, as peptides or protein, in nucleic acid form, as components of chimeric virus-like particles, or in cell-based vaccines. Encouraging results from experimental vaccination systems in animal models have led to several prophylactic and therapeutic vaccine clinical trials. If these preventive and therapeutic HPV vaccines prove successful in patients, as they have in animal models, then oncogenic HPV infection and its associated malignancies may be controllable by vaccination.

Effect of TA-CIN (HPV 16 L2E6E7) booster immunisation in vulval intraepithelial neoplasia patients previously vaccinated with TA-HPV (vaccinia virus encoding HPV 16/18 E6E7)

Heterologous prime-boost vaccination schedules employing TA-HPV, a vaccinia virus encoding HPV 16/18 E6 and E7, in combination with TA-CIN, an HPV 16 L2E6E7 fusion protein, may offer advantages over the use of either agent alone for the immunotherapy of human papillomavirus (HPV) type 16-associated vulval intraepithelial neoplasia (VIN). In the present study, 10 women with HPV 16-positive high grade VIN, previously primed with TA-HPV, received three booster immunisations with TA-CIN. All but one demonstrated HPV 16-specific proliferative T-cell and/or serological responses following vaccination. Three patients additionally showed lesion shrinkage or symptom relief, but no direct correlation between clinical and immunological responses was seen.

Cytotoxic-T-lymphocyte human papillomavirus type 16 E5 peptide with CpG-oligodeoxynucleotide can eliminate tumor growth in C57BL/6 mice

Previously, we identified human papillomavirus type 16 (HPV-16) E5 as a tumor rejection antigen that can induce cytotoxic T lymphocytes (CTLs) to protect against tumor growth (D. W. Liu et al., J. Virol. 74:9083-9089, 2000). In the present study, we further mapped the CTL epitope of E5 protein by analyzing E5-specific CD8(+) gamma interferon-positive (IFN-gamma(+)) double-positive cells in C57BL/6 mice with flow cytometry. The results showed the region spanning amino acids 25 to 33 (VCLLIRPLL) contained the potential D(b)-restricted CTL epitope. Subsequently, to determine whether peptide E5 25-33-based vaccination could induce E5-specific CTL activity, syngeneic animals received E5 25-33 emulsified with either CpG oligodeoxynucleotide (CpG ODN 1826) or Freund's adjuvant, and the growth of the tumors was monitored. The results showed that although both adjuvants induced E5-specific CD8(+) IFN-gamma(+) T cells and eradicated E5-containing tumor growth, CpG ODN was found to stimulate stronger CTL response than Freund's adjuvant. We also compared the immune response of the effector/memory/recall phase induced by E5 25-33 peptide or by E5 protein that was synthesized in vivo by adenovirus-based E5 gene delivery. E5 25-33 peptide plus CpG ODN was shown to be a superior vaccine compared to the adenovirus-based E5 gene. Interestingly, their chronological patterns of immune response were similar, suggesting that E5 25-33 is a major CTL peptide of E5 protein.

Human Papillomavirus Vaccines and Prevention of Cervical Cancer

Cervical cancer and precancerous cervical lesions constitute a major problem in women's health. Every year 470,000 cases of cervical cancer are diagnosed worldwide, and about half the women afflicted will die. In the United States alone, approximately 14,000 cases of cervical cancer are diagnosed each year despite the availability of screening and access to high-quality gynecological care. With the confirmation that cervical cancer is caused by an infectious agent, human papillomavirus, the possibility of fighting this disease with either prophylactic or therapeutic vaccination arose. This review describes advances in vaccine development and very promising first results for prophylactic vaccination against cervical cancer.

Therapeutic vaccines against infectious diseases

Therapeutic vaccines against chronic infectious diseases aim at eliciting broad humoral and cellular immune responses against multiple target antigens. Importantly, the development of such vaccines will help to establish surrogate markers of protection in humans and thus will augment the subsequent development of efficient prophylactic vaccines. A combination of synthetic small-molecule drugs and immunotherapeutics is likely to represent a powerful means of controlling chronic infections in the future. Challenges faced in developing therapeutic vaccines include the following: first, overcoming the potential impairment of immune responses due to established infection; second, optimizing schedules of vaccine administration in combination with standard of care chemotherapy; and third, defining what biological and immunological read-outs should be used to infer vaccine efficacy.

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.

Papillomavirus vaccines in clinical trials

Cervical cancer remains a leading cause of death for women in the developing world, and the treatment of preneoplastic cervical lesions is a considerable public-health burden in the developed world. There is unambiguous evidence that human papillomaviruses (HPVs) trigger the development of cervical and other anogenital malignancies, and that continued expression of HPV antigens in the tumours drives the neoplastic progression. The viral cause of cervical cancer is also its Achilles heel. Prophylactic vaccines to prevent HPV infection and therapeutic vaccines targeted at the HPV tumour antigens are in clinical trials. A firm grasp of the molecular pathogenesis of HPVs and the natural history of genital HPV infections, combined with greater understanding of how to trigger effective immune responses, offers hope for the elimination of HPV-associated diseases.

Disabled infectious single cycle herpes simplex virus (DISC-HSV) is a candidate vector system for gene delivery/expression of GM-CSF in human prostate cancer therapy

BACKGROUND

DISC-HSV is a replication incompetent herpes simplex virus that is a highly efficient vector for the transduction of genes in vivo and in vitro. We examine the ability of DISC-HSV to infect human prostate cancer cell-lines and xenograft tumor models, and induce expression of reporter and therapeutic cytokine genes.

METHODS

Infection was confirmed by cellular staining for the beta-galactosidase reporter gene product, and by EM. Human GM-CSF production following DISC-hGMCSF infection was measured using ELISA. The metabolic activity of infected cells was determined by NADP/NADPH assay. Cell death was estimated by cell-cycle analysis using flow cytometry with propidium iodide staining.

RESULTS

Infection of DU145, PC3 and LNCaP cells with DISC-HSV was dose dependent. Cells infected with DISC-hGM-CSF released significant levels of hGM-CSF for 3 days. NADP/NADPH assay suggested that infected cells continued to be metabolically active for 3 days post-infection, which was consistent with flow cytometry findings that cell death did not occur within 7 days of infection. Tumor xenografts injected with DISC-HSV expressed beta-galactosidase, and intracellular viral particles were demonstrated using EM.

CONCLUSIONS

We have previously reported the rejection of established tumors following intra-tumoral injection of DISC-GMCSF. This study demonstrates the ability of DISC-HSV to infect prostate cancer and express GMCSF at significant levels. We suggest that prostate cancer is a potential target for therapy using DISC-HSV containing GM-CSF.

Human papillomavirus therapy for the prevention and treatment of cervical cancer

Cervical carcinoma is associated with human papillomavirus infection. Proliferation of cancer cells depends on the continual expression of the E6 and E7 viral oncogenes. This article includes treatment strategies that can interfere with expression or function of the proteins and immunotherapeutic approaches that can eliminate cells that express E6 and E7 proteins.

Oral vaccination with recombinant Listeria monocytogenes expressing human papillomavirus type 16 E7 can cause tumor growth in mice to regress

Listeria monocytogenes is a Gram-positive, facultative intracellular bacterium with the ability to present secreted proteins to the major histocompatibility complex class I pathway to stimulate cell-mediated immune response. In our study, we constructed the recombinant L. monocytogenes encoding human papillomavirus type 16 E7 gene (rLM-E7). When orally administered to syngeneic mice, rLM-E7 could induce a cytotoxic T-lymphocyte (CTL) response. Furthermore, in vitro flow cytometric assay and in vivo immune deficiency assays showed that rLM-E7 could prevent and eradicate tumor growth via CD8+-dependent CTLs. Hence, the potency of rLM-E7 as a therapeutic vaccine for cervical cancer is the result of the induction E7-specific cell-mediated immunity by L. monocytogenes. In addition to potency, this vaccine also offers ease of administration and reduced cost of production compared with other vaccines formulated for injection. Thus, L. monocytogenes encoding HPV-16 E7 may be a useful oral vaccine for cervical cancer treatment.

Prevalence of human papillomavirus in cervical cancer: a multicenter study in China

A large-scale epidemiologic survey on the prevalence of different types of human papillomavirus (HPV) in cervical cancer in China is indicated because of the implications for the development of diagnostic probes and vaccines against cervical cancer. A total of 809 cervical cancer specimens were collected from 5 regions in China including Shanghai, Guangzhou, Sichuan, Beijing and Hong Kong. HPV DNA was detected in 83.7% of the specimens. HPV-16 was present in 79.6%, HPV-18 in 7.5%, HPV-52 in 2.6% and HPV-58 in 3.8% of all HPV-positive specimens. The prevalences of HPV-16 and HPV-18 in Hong Kong were 61.7 and 14.8%, respectively, representing a lower HPV-16 and a higher HPV-18 proportion compared with the other regions. HPV-16 remained the most common HPV infection in both squamous cell carcinoma (SCC) and adenocarcinoma (AC). The proportion of HPV-18 infection was significantly higher in AC than in SCC.