The role of human papillomavirus vaccines in cervical neoplasia

Identification of HPV oncogene and host cell differentiation associated cellular heterogeneity in cervical cancer via single-cell transcriptomic analysis

Human Papillomaviruses (HPVs) are associated with around 5-10% of human cancer, notably nearly 99% of cervical cancer. The mechanisms HPV interacts with stratified epithelium (differentiated layers) during the viral life cycle, and oncogenesis remain unclear. In this study, we used single-cell transcriptome analysis to study viral gene and host cell differentiation-associated heterogeneity of HPV-positive cervical cancer tissue. We examined the HPV16 genes - E1, E6, and E7, and found they expressed differently across nine epithelial clusters. We found that three epithelial clusters had the highest proportion of HPV-positive cells (33.6%, 37.5%, and 32.4%, respectively), while two exhibited the lowest proportions (7.21% and 5.63%, respectively). Notably, the cluster with the most HPV-positive cells deviated significantly from normal epithelial layer markers, exhibiting functional heterogeneity and altered epithelial structuring, indicating that significant molecular heterogeneity existed in cancer tissues and that these cells exhibited unique/different gene signatures compared with normal epithelial cells. These HPV-positive cells, compared to HPV-negative, showed different gene expressions related to the extracellular matrix, cell adhesion, proliferation, and apoptosis. Further, the viral oncogenes E6 and E7 appeared to modify epithelial function via distinct pathways, thus contributing to cervical cancer progression. We investigated the HPV and host transcripts from a novel viewpoint focusing on layer heterogeneity. Our results indicated varied HPV expression across epithelial clusters and epithelial heterogeneity associated with viral oncogenes, contributing biological insights to this critical field of study.

Identification of HPV oncogene and host cell differentiation associated cellular heterogeneity in cervical cancer via single-cell transcriptomic analysis

Human Papillomaviruses (HPVs) are associated with around 5%-10% of human cancer, notably nearly 99% of cervical cancer. The mechanisms HPV interacts with stratified epithelium (differentiated layers) during the viral life cycle, and oncogenesis remain unclear. In this study, we used single-cell transcriptome analysis to study viral gene and host cell differentiation-associated heterogeneity of HPV-positive cervical cancer tissue. We examined the HPV16 genes-E1, E6, and E7, and found they expressed differently across nine epithelial clusters. We found that three epithelial clusters had the highest proportion of HPV-positive cells (33.6%, 37.5%, and 32.4%, respectively), while two exhibited the lowest proportions (7.21% and 5.63%, respectively). Notably, the cluster with the most HPV-positive cells deviated significantly from normal epithelial layer markers, exhibiting functional heterogeneity and altered epithelial structuring, indicating that significant molecular heterogeneity existed in cancer tissues and that these cells exhibited unique/different gene signatures compared with normal epithelial cells. These HPV-positive cells, compared to HPV-negative, showed different gene expressions related to the extracellular matrix, cell adhesion, proliferation, and apoptosis. Further, the viral oncogenes E6 and E7 appeared to modify epithelial function via distinct pathways, thus contributing to cervical cancer progression. We investigated the HPV and host transcripts from a novel viewpoint focusing on layer heterogeneity. Our results indicated varied HPV expression across epithelial clusters and epithelial heterogeneity associated with viral oncogenes, contributing biological insights to this critical field of study.

Human papillomavirus as a target for management, prevention and therapy

The discovery that human papillomavirus (HPV) is the necessary causal factor in cervical carcinogenesis has made it a target for prophylactic and therapeutic vaccines, as well as a diagnostic tool in cervical screening. Whilst prophylactic vaccination has proven very effective in terms of preventing cervical cancer precursor lesions, therapeutic strategies have presented far greater challenges. HPV testing has shown itself to be extremely valuable in the triage of low grade cytological abnormalities, test of cure following treatment of cervical intraepithelial neoplasia (CIN), and will, over the next 10 years, gradually replace cytology as the mainstay of primary cervical screening. In this review, the latest evidence supporting HPV as both a biomarker of risk for cervical cancer and a target for prophylactic and therapeutic vaccination is presented.

Progress in the development of a cervical cancer vaccine

Persistent infection by 'high risk' genotypes of human papilloma virus (HPV) is necessary but not sufficient for the development of over 98% of cervical cancers. Thus the development of vaccines that prevent HPV transmission represent an important opportunity to prevent cervical cancer. There are several prophylactic HPV vaccine formulations based upon L1 virus-like particles (VLPs) currently in phase III trials and recently released data are extremely promising. However, many practical issues surrounding implementation of these vaccines need to be addressed including, who and when to vaccinate, duration of protection, and integration with current screening programs. The vaccines currently being evaluated target the two most prevalent high risk HPV types which are responsible for approximately 70% of cervical cancers. To increase the breadth of protection, it is likely that L1 VLPs of other viral subtypes must be included, although vaccines targeting the conserved regions of the L2 minor capsid protein warrant further exploration in this regard. In addition the vaccines nearing licensing will not combat established HPV-related disease and a therapeutic vaccine, of which there are several candidates in early stages of development, would be desirable. This review discusses the background to and progress in vaccine development and the issues surrounding the introduction of HPV vaccines.

Immunological responses in women with human papillomavirus type 16 (HPV-16)-associated anogenital intraepithelial neoplasia induced by heterologous prime-boost HPV-16 oncogene vaccination

PURPOSE

The purpose is to study the immunogenicity of heterologous prime-boost human papillomavirus (HPV) oncogene vaccination in patients with anogenital intraepithelial neoplasia (AGIN).

EXPERIMENTAL DESIGN

Twenty-nine women with high-grade AGIN received three i.m. doses of TA-CIN (HPV-16 L2/E6/E7 protein) at four weekly intervals followed by a single dermal scarification of vaccinia HPV-16/18 E6/E7 and were followed up for 12 weeks. Immunity to HPV-16 was assessed by lymphoproliferation, IFN-gamma enzyme-linked immunospot (ELISPOT), and ELISA.

RESULTS

The patient group significantly responded to TA-CIN and not to the control antigen HPV-6 L2/E7 at all postvaccination time points when compared with baseline responses (P < or = 0.05). Ten of the patients showed at least a 3-fold increase in TA-CIN-specific proliferation at one or more time points after vaccination. Comparison of stimulation with HPV-16 E6- or E7-GST fusion proteins showed that proliferative responses were biased to HPV-16 E6. This bias was also seen by IFN-gamma ELISPOT using overlapping peptides, with HPV-16 E6- or E7-specific T cells being detected in 9 and 2 patients, respectively. In addition, vaccination resulted in the induction of antibodies against the HPV-16 oncoproteins. Of the 6 clinical responders, 2 patients showed both a proliferative TA-CIN-specific response and an E6-specific IFN-gamma response, whereas 3 other patients displayed E6-specific reactivity only. Stable disease was recorded in 19 patients, 8 of whom showed a concomitant TA-CIN-specific proliferative and/or E6-specific T-cell response. Of the 4 progressors, 2 failed to make a T-cell response and 2 responded by either proliferation or E6 ELISPOT alone.

CONCLUSIONS

The prime-boost regimen is immunogenic in AGIN patients (humoral and cellular immunity), but there is no simple relationship between induction of systemic HPV-16-specific immunity and clinical outcome. Other factors that may play a role in the eradication of long-term established AGIN lesions need to be determined to identify the patient group that would benefit from immunotherapy with the vaccines used in this study.

Vaccine and antibody-directed T cell tumour immunotherapy

Clearer evidence for immune surveillance in malignancy and the identification of many new tumour-associated antigens (TAAs) have driven novel vaccine and antibody-targeted responses for therapy in cancer. The exploitation of active immunisation may be particularly favourable for TAA where tolerance is incomplete but passive immunisation may offer an additional strategy where the immune repertoire is affected by either tolerance or immune suppression. This review will consider how to utilise both active and passive types of therapy delivered by T cells in the context of the failure of tumour-specific immunity by presenting cancer patients. This article will outline the progress, problems and prospects of several different vaccine and antibody-targeted approaches for immunotherapy of cancer where proof of principle pre-clinical studies have been or will soon be translated into the clinic. Two examples of vaccination-based therapies where both T cell- and antibody-mediated anti-tumour responses are likely to be relevant and two examples of oncofoetal antigen-specific antibody-directed T cell therapies are described in the following sections: (1) therapeutic vaccination against human papillomavirus (HPV) antigens in cervical neoplasia; (2) B cell lymphoma vaccines including against immunoglobulin idiotype; (3) oncofoetal antigens as tumour targets for redirecting T cells with antibody strategies.

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.

Therapeutic vaccination for the treatment of mucosotropic human papillomavirus-associated disease

There is a high prevalence of diseases caused by human papillomavirus (HPV) infection. Unfortunately, current treatments are inadequate. However, because there is evidence to support a role for the immune system in host defence against this virus, an immunotherapeutic approach is warranted. The existing immunotherapies are not completely effective, nor are they durable. In addition, natural history studies associated with spontaneous regression have provided little guidance to the design of successful interventions. This state of knowledge has encouraged efforts towards the development of novel immunotherapeutic strategies. Successful preclinical studies of therapeutic vaccine candidates have led to clinical studies for a variety of HPV-associated indications, such as anogenital warts and cervical and anal intraepithelial neoplasia. Immunisation approaches such as adjuvanted peptides, virus-like particles and fusion constructs are discussed. Specifically, chimaeric molecules comprised of mycobacterial heat-shock proteins (Hsps) and HPV16 E7 appear promising.

Improving cancer therapy by non-genotoxic activation of p53

Inactivation of p53 function is a common event in cancer. Approximately 50% of human tumours express mutant p53 and there is evidence that in others, including many childhood tumours, p53 function is impaired in other ways. These defects in p53 function may be due to the alteration of cellular factors that modulate p53 or to the expression of viral oncoproteins. Radiotherapy and many of the chemotherapeutic drugs currently used in cancer treatment are potent activators of p53. However, most of these therapies have a serious drawback, and that is the long-term consequences of their DNA damaging effects. Here, we review the discoveries in p53 research that are most significant to the development of new therapies based on the induction of the transcriptional activity of p53 in a non-genotoxic way and discuss the situations in which this type of approach may be most beneficial.

Human papillomavirus type 16 L1 capsomeres induce L1-specific cytotoxic T lymphocytes and tumor regression in C57BL/6 mice

We analyzed capsomeres of human papillomavirus type 16 (HPV16) consisting of the L1 major structural protein for their ability to trigger a cytotoxic T-cell (CTL) response. To this end, we immunized C57BL/6 mice and used the L1(165-173) peptide for ex vivo restimulation of splenocytes prior to analysis ((51)Cr release assay and enzyme-linked immunospot assay [ELISPOT]). This peptide was identified in this study as a D(b)-restricted naturally processed CTL epitope by HPV16 L1 sequence analysis, major histocompatibility complex class I binding, and (51)Cr release assays following immunization of C57BL/6 mice with HPV16 L1 virus-like particles (VLPs). HPV16 L1 capsomeres were obtained by purification of HPV16 L1 lacking 10 N-terminal amino acids after expression in Escherichia coli as a glutathione S-transferase fusion protein (GST-HPV16 L1 Delta N10). Sedimentation analysis revealed that the majority of the purified protein consisted of pentameric capsomeres, and assembled particles were not observed in minor contaminating higher-molecular-weight material. Subcutaneous (s.c.) as well as intranasal immunization of C57BL/6 mice with HPV16 L1 capsomeres triggered an L1-specific CTL response in a dose-dependent manner as measured by ELISPOT and (51)Cr release assay. Significant reduction of contaminating bacterial endotoxin (lipopolysaccharide) from the capsomere preparation did not diminish the immunogenicity. Antibody responses (serum and vaginal) were less robust under the experimental conditions employed. In addition, s.c. vaccination with HPV16 L1 capsomeres induced regression of established tumors expressing L1 determinants (C3 tumor cells). Our data demonstrate that capsomeres are potent inducers of CTL responses similar to completely assembled T=7 VLPs. This result is of potential relevance for the development of (combined prophylactic and therapeutic) HPV-specific vaccines, since capsomeres can be produced easily and also can be modified to incorporate heterologous sequences such as early HPV proteins.

Differences in the ubiquitination of p53 by Mdm2 and the HPV protein E6

The human papillomavirus (HPV) protein E6 can promote the ubiquitination of the p53 tumour suppressor in vitro, providing an explanation for the ability of E6 to induce p53 degradation in vivo and contribute to the potential tumorigenic effect of the virus. Instead, in non-infected cells, p53 levels are primarily destabilised by the ubiquitin E3 ligase activity of the Mdm2 protein. Here we have compared the effects of E6 and Mdm2 on p53 ubiquitination in vivo. We show that whereas in the presence of Mdm2 proteasome inhibitors induce the accumulation of ubiquitinated forms of p53, this does not occur in the presence of E6. Accordingly, we confirm that the effect of E6 and p53 is independent of the six C-terminal lysine residues in p53, which have previously been described to play an important role for effective ubiquitination and degradation of 53 mediated by Mdm2. We also show that other yet unidentified residues in p53 are also susceptible to ubiquitination. These results indicate that E6 does not induce ubiquitination of p53 in the same way as Mdm2 in order to promote its degradation, suggesting important differences between the Mdm2 and E6 effects on p53 degradation.

Primary prevention of uterine cervix cancer: focus on vaccine history and current strategy

Primary prevention of uterine cervix cancer spans the gamut of human papillomavirus vaccine development, dietary adjustment, chemoprevention, and risk reduction. Lifestyle and social behaviors impact on risk for cervical cancer. Before examining the growing body of molecular evidence, animal studies, and phase I clinical trials that suggest that a virus-based vaccine for cervical cancer may soon become a reality, one must reflect on what has gone before in the vaccine-based battle with viral disease.