Cytotoxic T-lymphocyte responses to human papillomavirus type 16 E5 and E7 proteins and HLA-A*0201-restricted T-cell peptides in cervical cancer patients

Therapeutic DNA Vaccines against HPV-Related Malignancies: Promising Leads from Clinical Trials

In 2014 and 2021, two nucleic-acid vaccine candidates named MAV E2 and VGX-3100 completed phase III clinical trials in Mexico and U.S., respectively, for patients with human papillomavirus (HPV)-related, high-grade squamous intraepithelial lesions (HSIL). These well-tolerated but still unlicensed vaccines encode distinct HPV antigens (E2 versus E6+E7) to elicit cell-mediated immune responses; their clinical efficacy, as measured by HSIL regression or cure, was modest when compared with placebo or surgery (conization), but both proved highly effective in clearing HPV infection, which should help further optimize strategies for enhancing vaccine immunogenicity, toward an ultimate goal of preventing malignancies in millions of patients who are living with persistent, oncogenic HPV infection but are not expected to benefit from current, prophylactic vaccines. The major roadblocks to a highly efficacious and practical product remain challenging and can be classified into five categories: (i) getting the vaccines into the right cells for efficient expression and presentation of HPV antigens (fusion proteins or epitopes); (ii) having adequate coverage of oncogenic HPV types, beyond the current focus on HPV-16 and -18; (iii) directing immune protection to various epithelial niches, especially anogenital mucosa and upper aerodigestive tract where HPV-transformed cells wreak havoc; (iv) establishing the time window and vaccination regimen, including dosage, interval and even combination therapy, for achieving maximum efficacy; and (v) validating therapeutic efficacy in patients with poor prognosis because of advanced, recurrent or non-resectable malignancies. Overall, the room for improvements is still large enough that continuing efforts for research and development will very likely extend into the next decade.

Differences in Extracellular Vesicle Protein Cargo Are Dependent on Head and Neck Squamous Cell Carcinoma Cell of Origin and Human Papillomavirus Status

To identify potential extracellular vesicle (EV) biomarkers in head and neck squamous cell carcinoma (HNSCC), we evaluated EV protein cargo and whole cell lysates (WCL) from HPV-positive and -negative HNSCC cell lines, as well as normal oral keratinocytes and HPV16-transformed cells. EVs were isolated from serum-depleted, conditioned cell culture media by polyethylene glycol (PEG) precipitation/ultracentrifugation. EV and WCL preparations were analyzed by LC-MS/MS. Candidate proteins detected at significantly higher levels in EV compared with WCL, or compared with EV from normal oral keratinocytes, were identified and confirmed by Wes Simple Western protein analysis. Our findings suggest that these proteins may be potential HNSCC EV markers as proteins that may be (1) selectively included in EV cargo for export from the cell as a strategy for metastasis, tumor cell survival, or modification of tumor microenvironment, or (2) representative of originating cell composition, which may be developed for diagnostic or prognostic use in clinical liquid biopsy applications. This work demonstrates that our method can be used to reliably detect EV proteins from HNSCC, normal keratinocyte, and transformed cell lines. Furthermore, this work has identified HNSCC EV protein candidates for continued evaluation, specifically tenascin-C, HLA-A, E-cadherin, EGFR, EPHA2, and cytokeratin 19.

Development of multiepitope therapeutic vaccines against the most prevalent high-risk human papillomaviruses

Aim: Our goal was the development of DNA- or peptide-based multiepitope vaccines targeting HPV E7, E6 and E5 oncoproteins in tumor mouse model. Materials & methods: After designing the multiepitope E7, E6 and E5 constructs from four types of high risk HPVs (16, 18, 31 & 45) using bioinformatics tools, mice vaccination was performed by different homologous and heterologous modalities in a prophylactic setting. Then, anti-tumor effects of the best prophylactic strategies were studied in a therapeutic setting. Results: In both prophylactic and therapeutic experiments, groups receiving homologous E7+E6+E5 polypeptide, and heterologous E7+E6+E5 DNA prime/polypeptide boost were successful in complete rejection of tumors. Conclusion: The designed multiepitope constructs can be considered as promising candidates to develop effective therapeutic HPV vaccines.

A comprehensive in silico analysis for identification of therapeutic epitopes in HPV16, 18, 31 and 45 oncoproteins

Human papillomaviruses (HPVs) are a group of circular double-stranded DNA viruses, showing severe tropism to mucosal tissues. A subset of HPVs, especially HPV16 and 18, are the primary etiological cause for several epithelial cell malignancies, causing about 5.2% of all cancers worldwide. Due to the high prevalence and mortality, HPV-associated cancers have remained as a significant health problem in human society, making an urgent need to develop an effective therapeutic vaccine against them. Achieving this goal is primarily dependent on the identification of efficient tumor-associated epitopes, inducing a robust cell-mediated immune response. Previous information has shown that E5, E6, and E7 early proteins are responsible for the induction and maintenance of HPV-associated cancers. Therefore, the prediction of major histocompatibility complex (MHC) class I T cell epitopes of HPV16, 18, 31 and 45 oncoproteins was targeted in this study. For this purpose, a two-step plan was designed to identify the most probable CD8+ T cell epitopes. In the first step, MHC-I and II binding, MHC-I processing, MHC-I population coverage and MHC-I immunogenicity prediction analyses, and in the second step, MHC-I and II protein-peptide docking, epitope conservation, and cross-reactivity with host antigens' analyses were carried out successively by different tools. Finally, we introduced five probable CD8+ T cell epitopes for each oncoprotein of the HPV genotypes (60 epitopes in total), which obtained better scores by an integrated approach. These predicted epitopes are valuable candidates for in vitro or in vivo therapeutic vaccine studies against the HPV-associated cancers. Additionally, this two-step plan that each step includes several analyses to find appropriate epitopes provides a rational basis for DNA- or peptide-based vaccine development.

hrHPV E5 oncoprotein: immune evasion and related immunotherapies

The immune response is a key factor in the fight against HPV infection and related cancers, and thus, HPV is able to promote immune evasion through the expression of oncogenes. In particular, the E5 oncogene is responsible for modulation of several immune mechanisms, including antigen presentation and inflammatory pathways. Moreover, E5 was suggested as a promising therapeutic target, since there is still no effective medical therapy for the treatment of HPV-related pre-neoplasia and cancer. Indeed, several studies have shown good prospective for E5 immunotherapy, suggesting that it could be applied for the treatment of pre-cancerous lesions. Thus, insofar as the majority of cervical, oropharyngeal and anal cancers are caused by high-risk HPV (hrHPV), mainly by HPV16, the aim of this review is to discuss the immune pathways interfered by E5 oncoprotein of hrHPV highlighting the various aspects of the potential immunotherapeutic approaches.

HPV 16 E5 oncoprotein is expressed in early stage carcinogenesis and can be a target of immunotherapy

HPV16 persistent infection is a well-known condition that precedes human cancer development. High risk HPV E5 proteins cooperate with E6/E7 oncogenes to promote hyper-proliferation of infected cells leading to possible cancer progression. Thus, presence of E5 viral transcripts could be a key marker of active infection and, in turn, a target of immunotherapy. Purpose of the study is to detect E5 transcripts in clinical samples and to explore the activity of novel anti-HPV16 E5 DNA vaccines. HPV transcripts were detected by PCR with specific primers encompassing the splice-donor sites of E5 transcript. For E5-based immunotherapies, 2 E5-based versions of DNA vaccines carrying whole E5 gene or a synthetic multiepitope gene were improved by fusion to sequence of PVX coat protein. These vaccines were challenged with a new luminescent animal model based on C3-Luc cell line. E5 transcripts were detected in clinical samples of women with HPV positive low-grade SIL, demonstrating the validity of our test. In C3 pre-clinical mouse model, vaccine candidates were able to induce a strong cellular immunity as indicated by ELISPOT assays. In addition, E5-CP vaccines elicited strong anti-tumor effects as showed by decreased tumor growth monitored by animal imaging. The tumor growth inhibition was comparable to those obtained with anti-E7 DNA vaccines. In conclusion, detection of E5 transcripts in clinical samples indicates that E5 is a possible target of immunotherapy. Data from pre-clinical model demonstrate that E5 genetic immunization is feasible, efficacious and could be utilized in clinical trials.

Interleukin 10 promotes immune response by increasing the survival of activated CD8+ T cells in human papillomavirus 16-infected cervical cancer

Human papillomavirus (HPV)-specific CD8+ T cells are present in HPV-infected cervical cancer patients and have demonstrated potent antitumor properties. However, these cells cannot control tumor progression in most patients. To investigate the underlying mechanisms involved in suppressing or promoting CD8+ T cell functions, we focused on interleukin 10 (IL-10), a pleiotropic cytokine with controversial roles in antitumor immunity. We found that compared to healthy controls, circulating CD8+ T cells in HPV 16-infected cervical cancer patients expressed significantly higher levels of IL-10. Interestingly, these CD8+ T cells from cervical cancer patients, but not those from healthy controls, responded to HPV 16 E6/E7 peptide stimulation by increasing IL-10 expression, demonstrating an antigen-specific IL-10 release. Addition of exogenous IL-10 improved the survival, but did not increase the proliferation, of peptide-stimulated CD8+ T cells. CD8+ T cells cultured in the presence of IL-10 also resulted in significantly higher interferon gamma (IFN-gamma) and granzyme B concentration, primarily due to improved cell survival. In resected cervical tumors, the frequency of tumor-infiltrating IL-10+ CD8+ T cells was positively correlated with the frequency of tumor-infiltrating IFN-gamma+ and granzyme B+ CD8+ T cells. Tumor-associated macrophages were more potent than peripheral blood monocyte-derived macrophages at inducing IL-10 expression in CD8+ T cells, possibly explaining the elevated IL-10+ CD8+ T cell frequency in cervical cancer patients. Together, these results are consistent with an immunostimulatory role of IL-10, which promoted CD8+ T cell response by increasing the survival of activated CD8+ T cells.

Chimeric peptide containing both B and T cells epitope of tumor-associated antigen L6 enhances anti-tumor effects in HLA-A2 transgenic mice

Synthetic peptides are attractive for cancer immunotherapy because of their safety and flexibility. In this report, we identified a new B cell epitope of tumor-associated antigen L6 (TAL6) that could induce antibody-dependent cellular cytotoxicity (ADCC) in vivo. We incorporated the B cell epitope with a cytotoxic T lymphocyte (CTL) and a helper T (Th) epitope to form a chimeric long peptide. We formulated the chimeric peptide with different adjuvants to immunize HLA-A2 transgenic mice and evaluate their immunogenicity. The chimeric peptide formulated with an emulsion type nanoparticle (PELC) adjuvant and a toll-like receptor 9 agonist (CpG ODN) (PELC/CpG) induced the greatest ADCC and CTL responses. The induced anti-tumor immunity inhibited the growth of TAL6-positive cancer cells. Moreover, we observed that immunization with the chimeric peptide inhibited cancer cell migration in vitro and metastasis in vivo. These data suggest that a chimeric peptide containing both B and T cell epitopes of TAL6 formulated with PELC/CpG adjuvant is feasible for cancer immunotherapy.

A novel "priming-boosting" strategy for immune interventions in cervical cancer

Despite the encouraging development of a preventive vaccine for human papillomavirus (HPV), it cannot improve ongoing infections. Therefore, a new vaccine is urgently needed that can prevent and treat cervical cancer, and cure pre-cancerous lesions. In this study, we constructed two peptide-based vaccines. The first was a short-term, long-peptide (ST-LP) vaccine that simultaneously targeted three key carcinogenic epitopes (E5-E6-E7) on HPV16. We tested this vaccine in murine TC-1 cells infected with a recombinant adeno-associated virus (rAAV) fused with HPV16E5 DNA (rTC-1 cells), which served as a cell model; we also tested it in immune-competent mice loaded with rTC-1 cells, which served as an ectopic tumor model. The ST-LP injections resulted in strong, cell-mediated immunity, capable of attacking and eliminating abnormal antigen-bearing cells. Furthermore, to prolong immunogenic capability, we designed a unique rAAV that encoded the three predicted epitopes for a second, long-term, long-peptide (LT-LP) vaccine. Moreover, we used a new immune strategy of continuous re-injections, where three ST-LP injections were performed at one-week intervals (days 0, 7, 14), then one LT-LP injection was performed on day 120. Our in vitro and in vivo studies revealed that this strategy could boost the immune response to produce longer and stronger protection against target cells, and mice were thoroughly protected from tumor growth. Our results showed that priming the immune system with the ST-LP vaccine, followed by boosting the immune system with the LT-LP vaccine could generate a rapid, robust, durable cytotoxic T-lymphocyte response to HPV16-positive tumors.

Anti-tumor effects of genetic vaccines against HPV major oncogenes

Expression of HPV E5, E6 and E7 oncogenes are likely to overcome the regulation of cell proliferation and to escape immunological control, allowing uncontrolled growth and providing the potential for malignant transformation. Thus, their three oncogenic products may represent ideal target antigens for immunotherapeutic strategies. In previous attempts, we demonstrated that genetic vaccines against recombinant HPV16 E7 antigen were able to affect the tumor growth in a pre-clinical mouse model. To improve this anti-HPV strategy we developed a novel approach in which we explored the effects of E5-based genetic immunization. We designed novel HPV16 E5 genetic vaccines based on two different gene versions: whole E5 gene and E5Multi. The last one is a long multi epitope gene designed as a harmless E5 version. Both E5 genes were codon optimized for mammalian expression. In addition, we demonstrated that HPV 16 E5 oncogene is expressed in C3 mouse cell line making it an elective model for the study of E5 based vaccine. In this mouse model the immunological and biological activity of the E5 vaccines were assessed in parallel with the activity of anti-E7 and anti-E6 vaccines already reported to be effective in an immunotherapeutic setting. These E7 and E6 vaccines were made with mutated oncogenes, the E7GGG mutant that does not bind pRb and the E6F47R mutant that is less effective in inhibiting p53, respectively. Results confirmed the immunological activity of genetic formulations based on attenuated HPV16 oncogenes and showed that E5-based genetic immunization provided notable anti-tumor effects.

Cytolytic activity of the human papillomavirus type 16 E711-20 epitope-specific cytotoxic T lymphocyte is enhanced by heat shock protein 110 in HLA-A*0201 transgenic mice

Heat shock proteins (HSPs) have been successfully applied to a broad range of vaccines as biological adjuvants to enhance the immune response. The recently defined HSP110, in particular, exhibits strong protein binding affinity and is capable of enhancing the immunogenicity of protein antigens remarkably more than other HSP family members. In our previous study, we verified that murine HSP110 (mHSP110) significantly enhanced the immune response of a C57BL/6 mouse model to the H-2(d)-restricted human papillomavirus (HPV) E749-57 epitope (short peptide spanning the 49th to 57th amino acid residues in the E7 protein). To determine whether HSP110 similarly enhances the immunogenicity of human epitope peptides, we used the HLA-A2 transgenic mouse model to investigate the efficacy of the mHSP110 chaperone molecule as an immunoadjuvant of the human HLA-A2-restricted HPV16 E711-20 epitope vaccine. Results showed that mHSP110 efficiently formed a noncovalently bound complex with the E711-20 epitope. The mHSP110-E711-20 complex induced epitope-specific splenocyte proliferation and E711-20-specific gamma interferon (IFN-γ) secretion. Importantly, cytotoxic T lymphocytes primed by the mHSP110-E711-20 complex exerted strong cytolytic effects on target T2 cells pulsed with the E711-20 peptide or TC-1 cells transfected with the HLA-A2 gene. In addition, the mHSP110-E711-20 complex elicited stronger ex vivo and in vivo antitumor responses than either emulsified complete Freund's adjuvant or HSP70-chaperoned E711-20 peptide. These collective data suggest that HSP110 is a promising immunomodulator candidate for peptide-based human cancer vaccines, such as for the HLA-A2-restricted E711-20 epitope.

HPV-16 E6 and E7 protein T cell epitopes prediction analysis based on distributions of HLA-A loci across populations: an in silico approach

Human papillomavirus type 16 (HPV-16) is the most prevalent virus in human cervical cancers, as it is present in more than half of all cases. Many studies have found continued expression of E6 and E7 proteins in the majority of cervical cancer cases, but not in normal tissues. These results indicated that the E6 and E7 proteins could be ideal candidate therapeutic vaccines against HPV-16 infection and cervical cancer. Using the Immune Epitope Database Analysis Resource, cytotoxic T lymphocyte (CTL) epitopes of the HPV-16 E6 and E7 proteins were predicted according to worldwide frequency distributions of HLA-A alleles (HLA-A*01:01, -A*02:01, -A*02:06, -A*03:01, -A*11:01, -A*24:02, -A*26:01, -A*31:01 and -A*33:03). Our results predicted a total of 81 epitopes of HPV-16 E6 (n=59) and E7 (n=22). Epitope cluster analysis showed that among the 20 clusters of HPV-16 E6, cluster 3 contained the most epitopes (10 epitopes), which was represented by HLA-A*31:01 and -A*33:03. Of the 10 clusters of HPV-16 E7, cluster 3 contained the most epitopes (5 epitopes), which was represented by HLA-A*01:01 and -A*26:01. Our results indicated that the combination of epitopes FAFRDLCIVYR₅₂₋₆₂ of E6 (HLA-A*02:06, HLA-A*31:01, and HLA-A*33:03), PYAVCDKCLKF₆₆₋₇₆ of E6 (HLA-A*11:01 and HLA-A*24:02), HGDTPTLHEY₂₋₁₁ of E7 (HLA-A*01:01 and HLA-A*26:01), and YMLDLQPETT₁₁₋₂₀ of E7 (HLA-A*02:01) could vaccinate >50% of all individuals worldwide. Our results propose CTL epitopes or combinations of them predicted in current study for candidate therapeutic vaccines to effectively control HPV-16 infection and development of cervical cancer.

Polymorphisms of HLA-A and HLA-B genes in genetic susceptibility to esophageal carcinoma in Chaoshan Han Chinese

Esophageal carcinoma (EC) occurs at high rate in Chaoshan region of southern China. Human leukocyte antigen (HLA) polymorphism has been implicated in risk for various cancers. To investigate the impact of HLA-A and HLA-B polymorphisms on susceptibility to EC, a case-control study was conducted among 206 patients with esophageal squamous cell carcinoma and 524 controls from Chaoshan Han population. HLA-A and HLA-B polymorphisms were genotyped by polymerase chain reaction-sequence-specific primers. Genotypic association tests for dominant, recessive, and additive models, and haplotypic association were calculated using unconditional logistic regression. A*11 was identified in a recessive model as an only allele strongly associated with EC risk (odds ratios [OR]=2.10, 95% confidence interval [CI]=1.33-3.31) even after correction for multiple test. The haplotypes A*02-B*46 (OR=1.53, 95% CI=1.04-2.24) and A*11-B*51 (OR=2.29, 95% CI=1.20-4.40) showed association with increased risk for EC, whereas A*11-B*58 (OR=0.00, 95% CI=0.00-0.82) was associated with decreased risk, though the significance of these haplotypes was lost after correction. This is a first association study at genetic level identifying HLA-A and HLA-B-related variations in genetic susceptibility to EC among Chaoshan population. The variation pattern is likely to be EC-specific because it is different from that observed for nasopharyngeal carcinoma in the same study population and might, at least in part, explain the high rate of EC in this ethnic group.