Evasion of host immunity directed by papillomavirus-encoded proteins

Surveillance of human papillomavirus through salivary diagnostics - A roadmap to early detection of oropharyngeal cancer in men

Human papillomavirus (HPV) is the most common sexually transmitted disease. Certain strains have the potential to cause malignancy in multiple anatomical sites if not cleared by the immune system. In most infected people, HPV is cleared within two years. However, HPV may persist in susceptible individuals with certain risk factors, eventually leading to malignancy. New evidence suggests that over 75% of all oropharyngeal cancers (OPC) are directly attributable to HPV. It is estimated that prophylactic HPV vaccination alone may take at least 25 years to have a significant impact on reducing the incidence of OPC. The temporal link between detection of oral HPV, persistence of the infection and the subsequent development of OPC have been well established. Moreover, men have threefold higher risk than women for acquiring HPV-OPC. This comprehensive review focuses on OPC development in men, highlighting the risk factors associated with malignant transformation of HPV-OPC. Current evidence is insufficient to determine whether early identification of at-risk demographics, screening, and prompt diagnosis result in improved outcomes. Hitherto, the effectiveness of an oral HPV screening program in this regard has not been investigated. Nevertheless, the potential to emulate the success of the cervical screening program remains a very real possibility.

Rescue of NLRC5 expression restores antigen processing machinery in head and neck cancer cells lacking functional STAT1 and p53

The antigen processing machinery (APM) components needed for a tumor cell to present an antigen to a T cell are expressed at low levels in solid tumors, constituting an important mechanism of immune escape. More than most other solid tumors, head and neck squamous cell carcinoma (HNSCC) cells tend to have low APM expression, rendering them insensitive to immune checkpoint blockade and most other forms of immunotherapy. In HNSCC, this APM deficiency is largely driven by high levels of EGFR and SHP2, leading to low expression and activation of STAT1; however, recent studies suggest that p53, which is often mutated in HNSCCs, may also play a role. In the current study, we aimed to investigate the extent to which STAT1 and p53 individually regulate APM component expression in HNSCC cells. We found that in cells lacking functional p53, APM expression could still be induced by interferon-gamma or DNA-damaging chemotherapy (cisplatin) as long as STAT1 expression remained intact; when both transcription factors were knocked down, APM component expression was abolished. When we bypassed these deficient pathways by rescuing the expression of NLRC5, APM expression was also restored. These results suggest that dual loss of functional STAT1 and p53 may render HNSCC cells incapable of processing and presenting antigens, but rescue of downstream NLRC5 expression may be an attractive strategy for restoring sensitivity to T cell-based immunotherapy.

The effect of multiple-dose ivermectin treatment on CD4+/CD8+ and the oxidative stress index in goats with udder viral papillomatosis

This study aims to reveal the therapeutic effect of ivermectin against Capra hircus papillomavirus (ChPV-1) infection and on the CD4⁺/CD8⁺ (cluster of differentiation) and oxidative stress index (OSI). Twenty hair goats naturally infected with ChPV-1 were divided into two groups with equal numbers as the ivermectin group and the control groups. Ivermectin was administered subcutaneously at a dose of 0.2 mg/kg to the goats in the ivermectin group on days 0, 7, and 21. Blood samples were collected from the vena jugularis on days 0, 21, 45, and 90. The cluster of differentiation4⁺/CD8⁺ ratio was significantly higher in the ivermectin group than in the control group on the 90th day. Furthermore, the CD8⁺ concentration was significantly decreased in the ivermectin group on the 90th day compared with the control group. Both total oxidant status (TOS) and OSI were found to be significantly higher in the control group on the 21st and 45th days than in the ivermectin group. On the 90th day, it was determined that the lesions in the ivermectin group improved significantly compared to those in the control group. Additionally, only in the ivermectin group was there a significant difference between the 90th day and the other days in terms of healing. As a result, it can be suggested that ivermectin has positive effects on the immune response and that its oxidative actions are of therapeutic value and do not harm the systemic oxidative status, as in untreated goats.

Design, synthesis, and evaluation of peptides derived from L1 protein against bovine papillomavirus-1/2 identified along Mexico’s cattle export route

Introduction

Bovine papillomatosis affects animal health and represents one of the greatest economic losses in the livestock sector. New control and prevention methods to protect the livestock industry from this disease are necessary. The aim of this study was to evaluate a candidate peptide for antibody production against bovine papillomavirus (BPV).

Material and Methods

A total of 64 cattle underwent wart excision among 5,485 cattle distributed over 2 to 4 farms per state and 12 farms in total in the four Mexican states of Tabasco, Chiapas, Veracruz, and Nuevo León. The prevalence of bovine papillomatosis per farm was calculated by wart visualisation. The warts were genotyped by PCR and sequenced, then a phylogenetic tree was built using MEGA X software. A synthetic peptide was designed in the ABCpred, Bepipred 2.0, Bepipred IDBT, Bepitope, LBtope, and MHC II predictor online server software’s based on the C-terminal region of the L1 protein. Mice antibody production was induced by subcutaneous immunisation with 50 μg of synthetic peptide and evaluated by indirect ELISA.

Results

The prevalence of BPV was higher in Tabasco, Chiapas, and Veracruz. Bovine papillomaviruses 1 and 2 were found in all representative samples. A phylogenetic tree showed that Mexican sequences were located in exclusive clades yet were highly related to international ones. The peptide immunisation induced antibody titres of 1 : 10,000/1 : 1,000,000 against synthetic peptide and whole wart lysate (WWL), respectively.

Conclusion

Co-infections of BPV-1 and -2 were found in all four states. Immunisation of BALB/C mice with BPV-1/2–derived synthetic peptide based on the C-terminal region of the major viral capsid protein L1 induced the production of specific antibodies able to recognise BPV-1/2 viral particles from bovine WWL.

Oropharyngeal Carcinoma with a Special Focus on HPV-Related Squamous Cell Carcinoma

Human papillomavirus-positive oropharyngeal squamous cell carcinoma (HPV-OPSCC) has one of the most rapidly increasing incidences of any cancer in high-income countries. The most recent (8th) edition of the Union for International Cancer Control/American Joint Committee on Cancer staging system separates HPV-OPSCC from its HPV-negative counterpart to account for the improved prognosis seen in the former. Indeed, owing to its improved prognosis and greater prevalence in younger individuals, numerous ongoing trials are examining the potential for treatment deintensification as a means to improve quality of life while maintaining acceptable survival outcomes. Owing to the distinct biology of HPV-OPSCCs, targeted therapies and immunotherapies have become an area of particular interest. Importantly, OPSCC is often detected at an advanced stage, highlighting the need for diagnostic biomarkers to aid in earlier detection. In this review, we highlight important advances in the epidemiology, pathology, diagnosis, and clinical management of HPV-OPSCC and underscore the need for a progressive understanding of the molecular basis of this disease toward early detection and precision care.

Like Brothers in Arms: How Hormonal Stimuli and Changes in the Metabolism Signaling Cooperate, Leading HPV Infection to Drive the Onset of Cervical Cancer

Despite all precautionary actions and the possibility of using vaccinations to counteract infections caused by human papillomaviruses (HPVs), HPV-related cancers still account for approximately 5% of all carcinomas. Worldwide, many women are still excluded from adequate health care due to their social position and origin. Therefore, immense efforts in research and therapy are still required to counteract the challenges that this disease entails. The special thing about an HPV infection is that it is not only able to trick the immune system in a sophisticated way, but also, through genetic integration into the host genome, to use all the resources available to the host cells to complete the replication cycle of the virus without activating the alarm mechanisms of immune recognition and elimination. The mechanisms utilized by the virus are the metabolic, immune, and hormonal signaling pathways that it manipulates. Since the virus is dependent on replication enzymes of the host cells, it also intervenes in the cell cycle of the differentiating keratinocytes and shifts their terminal differentiation to the uppermost layers of the squamocolumnar transformation zone (TZ) of the cervix. The individual signaling pathways are closely related and equally important not only for the successful replication of the virus but also for the onset of cervical cancer. We will therefore analyze the effects of HPV infection on metabolic signaling, as well as changes in hormonal and immune signaling in the tumor and its microenvironment to understand how each level of signaling interacts to promote tumorigenesis of cervical cancer.

Human Papillomavirus 16 E6 Suppresses Transporter Associated with Antigen-Processing Complex in Human Tongue Keratinocyte Cells by Activating Lymphotoxin Pathway

Simple Summary

There is still limited knowledge of the critical pathogenic processes by which HPV16 induces oral carcinogenesis. Therefore, we aimed to illuminate the oncogenic role of HPV16 in the context of oral squamous cell carcinomas (OSCCs). Using human tongue keratinocyte cells, we demonstrated that HPV16 E6 promotes LTα₁β₂ and LTβR expression, thus promoting the lymphotoxin signaling pathway and leading to suppression of the transporter associated with the antigen-processing complex (TAPs; TAP1 and TAP2). Additionally, in vitro, we also demonstrated regulation of the antigenic peptide-loaded machinery in HPV-infected OSCC tissues through analysis of the transcriptomic profiles of the head and neck squamous cell carcinoma (HNSCC) cohort from the TCGA database, which was validated using fresh biopsied specimens. Thus, our study enhances the proposed functional role of HPV16 E6-associated immune-evasive properties in oral epithelial cells, revealing a possible mechanism underlying the development of HPV-mediated OSCCs.

Abstract

Infection by high-risk human papillomaviruses (hrHPVs), including HPV type 16 (HPV16), is a major risk factor for oral squamous cell carcinomas (OSCCs). However, the pathogenic mechanism by which hrHPVs promote oral carcinogenesis remains to be elucidated. Here, we demonstrated that the suppression of a transporter associated with the antigen-processing complex (TAPs; TAP1 and TAP2), which is a key molecule in the transportation of viral antigenic peptides into MHC class-I cells, is affected by the E6 protein of HPV16. Mechanistically, HPV-mediated immune evasion is principally mediated via the signal-transduction network of a lymphotoxin (LT) pathway, in particular LTα₁β₂ and LTβR. Our analysis of transcriptomic data from an HNSCC cohort from the Cancer Genome Atlas (TCGA) indicated that expression of TAP genes, particularly TAP2, was downregulated in HPV-infected cases. We further demonstrated that LTα₁β₂ and LTβR were upregulated, which was negatively correlated with TAP1 and TAP2 expression in HPV-positive clinical OSCC samples. Taken together, our findings imply that HPV16 E6 regulates the machinery of the antigenic peptide-loading system and helps to clarify the role of oncogenic viruses in the context of oral carcinoma.

CXCL10 Produced by HPV-Positive Cervical Cancer Cells Stimulates Exosomal PDL1 Expression by Fibroblasts via CXCR3 and JAK-STAT Pathways

Persistent infection with human papillomavirus (HPV) and immune surveillance failure may be the initiating factors for the carcinogenesis of cervical squamous cell carcinoma (CSCC). HPV infection might affect the innate immune pathway of cervical epithelial cells that constitute the “microenvironment” for tumor cells. Programmed death-ligand 1 (PD-L1) has been reported to be an immunosuppressor that helps cancer cells escape the actions of T cells. In the present study, CXCL10 was substantially upregulated both in cervical tissues of HPV infected patients with cervical intraepithelial neoplasia (CIN) or CSCC, as well as in HPV16 E6/E7 transgenic murine cervix. The HPV-positive (HPV+) cervical cancer cell lines SiHa and Caski secreted increased levels of CXCL10 compared to human foreskin fibroblasts (HFF-1), and its receptor CXCR3 was overexpressed in HFF-1. After co-culture with SiHa or Caski, the JAK-STAT signaling pathway and exosomal PD-L1 expression were both upregulated in HFF-1. Recombinant human CXCL10 induced JAK-STAT and PD-L1, while the CXCL10-CXCR3 and JAK-STAT inhibitors AMG487 or ruxolitinib reduced the expression of PD-L1 in HFF-1 cells. Furthermore, the upregulated expression of PD-L1 was verified in HPV+ but not HPV-negative (HPV-) patients with cervical cancers by analysis of tissue microarray cores in 25 cervical lesion patients (P < 0.05). The results indicate that HPV infection can induce cervical cancer cells to secrete CXCL10, which binds to CXCR3 in the surrounding fibroblast cells,leading to JAK-STAT pathway activation and the subsequent upregulated expression of exosomal PD-L1. These mechanisms may help HPV to escape immune response attack, leading to carcinogenesis.

The Role of Viruses in Carcinogenesis and Molecular Targeting: From Infection to Being a Component of the Tumor Microenvironment

About a tenth of all cancers are caused by viruses or associated with viral infection. Recent global events including the coronavirus disease-2019 (COVID-19) pandemic means that human encounter with viruses is increased. Cancer development in individuals with viral infection can take many years after infection, demonstrating that the involvement of viruses in cancer development is a long and complex process. This complexity emanates from individual genetic heterogeneity and the many steps involved in cancer development owing to viruses. The process of tumorigenesis is driven by the complex interaction between several viral factors and host factors leading to the creation of a tumor microenvironment (TME) that is ideal and promotes tumor formation. Viruses associated with human cancers ensure their survival and proliferation through activation of several cellular processes including inflammation, migration, and invasion, resistance to apoptosis and growth suppressors. In addition, most human oncoviruses evade immune detection and can activate signaling cascades including the PI3K-Akt-mTOR, Notch and Wnt pathways associated with enhanced proliferation and angiogenesis. This expert review examines and synthesizes the multiple biological factors related to oncoviruses, and the signaling cascades activated by these viruses contributing to viral oncogenesis. In particular, I examine and review the Epstein-Barr virus, human papillomaviruses, and Kaposi's sarcoma herpes virus in a context of cancer pathogenesis. I conclude with a future outlook on therapeutic targeting of the viruses and their associated oncogenic pathways within the TME. These anticancer strategies can be in the form of, but not limited to, antibodies and inhibitors.

Combinations of immunotherapy and radiation therapy in head and neck squamous cell carcinoma: a narrative review

Radiation therapy and systemic therapy are the primary non-surgical treatment modalities for head and neck squamous cell carcinoma (HNSCC). Despite advances in our biologic understanding of this disease and the development of novel therapeutics, treatment resistance remains a significant problem. It has become increasingly evident that the innate and adaptive immune systems play a significant role in the modulation of anti-tumor responses to traditional cancer-directed therapies. By inducing DNA damage and cell death, radiation therapy appears to activate both innate and adaptive immune responses. Immunotherapies targeting programmed cell death protein 1 (PD-1) and programmed cell death ligand 1 (PD-L1) also have yielded promising results, particularly in the recurrent/metastatic setting. In this review, we will discuss the rationale for combining radiotherapy with immunotherapy to harness the immunomodulatory effects of radiation therapy on HNSCC, as well as biomarkers for immune response. We will also review recent preclinical and clinical data exploring these combinations in various contexts, including recurrent/metastatic and locally advanced disease. Among those with locally advanced HNSCC, we will discuss clinical trials employing immunotherapy either concurrently with radiation therapy or as maintenance following chemoradiation in both the definitive and postoperative settings, with or without the use of cisplatin-based or non-cisplatin-based chemotherapy.

HPV and Other Microbiota; Who's Good and Who's Bad: Effects of the Microbial Environment on the Development of Cervical Cancer-A Non-Systematic Review

Cervical cancer is responsible for around 5% of all human cancers worldwide. It develops almost exclusively from an unsolved, persistent infection of the squamocolumnar transformation zone between the endo- and ecto-cervix with various high-risk (HR) human papillomaviruses (HPVs). The decisive turning point on the way to persistent HPV infection and malignant transformation is an immune system weakened by pathobionts and oxidative stress and an injury to the cervical mucosa, often caused by sexual activities. Through these injury and healing processes, HPV viruses, hijacking activated keratinocytes, move into the basal layers of the cervical epithelium and then continue their development towards the distal prickle cell layer (Stratum spinosum). The microbial microenvironment of the cervical tissue determines the tissue homeostasis and the integrity of the protective mucous layer through the maintenance of a healthy immune and metabolic signalling. Pathological microorganisms and the resulting dysbiosis disturb this signalling. Thus, pathological inflammatory reactions occur, which manifest the HPV infection. About 90% of all women contract an HPV infection in the course of their lives. In about 10% of cases, the virus persists and cervical intra-epithelial neoplasia (CIN) develops. Approximately 1% of women with a high-risk HPV infection incur a cervical carcinoma after 10 to 20 years. In this non-systematic review article, we summarise how the sexually and microbial mediated pathogenesis of the cervix proceeds through aberrant immune and metabolism signalling via CIN to cervical carcinoma. We show how both the virus and the cancer benefit from the same changes in the immune and metabolic environment.

Parenteral Bevacizumab for the Treatment of Severe Respiratory Papillomatosis in an Adult Population

OBJECTIVES/HYPOTHESIS

Recurrent respiratory papillomatosis (RRP) is a rare, potentially life-threatening, disease that impacts the voice, breathing, and quality of life of patients. Frequent surgical interventions may be needed to control symptoms. We examined the safety and efficacy of utilizing parenteral bevacizumab in the management of severe RRP in adults.

STUDY DESIGN

This is a retrospective review of clinical management approaches in a group of patients with severe RRP defined as having a high disease burden, frequent need for debridement, and/or tracheobronchial disease. Patients were initially treated with 15 mg/kg of bevacizumab at 3-week intervals. Bevacizumab dosing and frequency was then individually titrated down.

RESULTS

Fourteen adults received a median of 8.5 (range 2-17) bevacizumab infusions over approximately 24 months. All had a history of laryngeal RRP with 6/14 having additional tracheobronchial lesions. Patients required a median of 4 (range 2-11) procedures in the year prior to treatment. Only 3/10 (30%) patients who continued therapy required any additional procedures. Bevacizumab administration was generally well tolerated, with four patients discontinuing therapy. Medical reasons included severe epistaxis and hypertension and thrombocytopenia in an individual with systemic lupus erythematosus. Common side effects included hypertension (grade 2), headache (grades 1-2), elevated creatinine (grades 1-2), and epistaxis (grade 3).

CONCLUSIONS

Intravenous bevacizumab for the primary treatment of severe RRP in adults appears clinically effective and safe. Expected and typically mild side effects related to bevacizumab were observed. Continued investigation of bevacizumab through a prospective clinical trial is warranted.

LEVEL OF EVIDENCE

4. Laryngoscope, 131:E921-E928, 2021.

HPV16 E5 Mediates Resistance to PD-L1 Blockade and Can Be Targeted with Rimantadine in Head and Neck Cancer

There is a critical need to understand mechanisms of resistance and to develop combinatorial strategies to improve responses to checkpoint blockade immunotherapy (CBI). Here, we uncover a novel mechanism by which the human papillomavirus (HPV) inhibits the activity of CBI in head and neck squamous cell carcinoma (HNSCC). Using orthotopic HNSCC models, we show that radiation combined with anti-PD-L1 immunotherapy significantly enhanced local control, CD8⁺ memory T cells, and induced preferential T-cell homing via modulation of vascular endothelial cells. However, the HPV E5 oncoprotein suppressed immune responses by downregulating expression of major histocompatibility complex and interfering with antigen presentation in murine models and patient tumors. Furthermore, tumors expressing HPV E5 were rendered entirely resistant to anti-PD-L1 immunotherapy, and patients with high expression of HPV16 E5 had worse survival. The antiviral E5 inhibitor rimantadine demonstrated remarkable single-agent antitumor activity. This is the first report that describes HPV E5 as a mediator of resistance to anti-PD-1/PD-L1 immunotherapy and demonstrates the antitumor activity of rimantadine. These results have broad clinical relevance beyond HNSCC to other HPV-associated malignancies and reveal a powerful mechanism of HPV-mediated immunosuppression, which can be exploited to improve response rates to checkpoint blockade. SIGNIFICANCE: This study identifies a novel mechanism of resistance to anti-PD-1/PD-L1 immunotherapy mediated by HPV E5, which can be exploited using the HPV E5 inhibitor rimantadine to improve outcomes for head and neck cancer patients. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/4/732/F1.large.jpg.

Correlation of interleukin-18 gene polymorphism with the susceptibility of condyloma acuminatum in Chinese population

Host immunogenetic setting is involved in the regulation of human papillomavirus (HPV) infection and development of condyloma acuminatum (CA). We investigated the correlation of two common single nucleotide polymorphisms (SNPs) (−607C/A and −137G/C) of IL-18 with the susceptibility of CA in a large Chinese cohort. Out of 408 CA patients analyzed, 300 had HPV infection transmitted through sexual contact (SC) and 108 through non-sexual contact (NSC). In addition, 360 healthy volunteers were enrolled as controls. SNPs at positions −607C/A and −137G/C in IL-18 promoter were analyzed. Comparing CA patients to healthy controls, no dominant relevance was found between the IL-18 promoter −607 C/A or −137G/C polymorphisms and the CA disease either identified genotypically (p > 0.05) or by allelically (p > 0.05). However, the IL-18 promoter −137G/C polymorphism genotype and allele frequencies in the NSC CA group, but not between in the SC group, were significantly higher than in the controls. There was no dominant relevance between IL-18-607C/A polymorphism genotype and allele frequencies among SC, NSC CA patients, and controls. Our study demonstrates that polymorphism −137G/C in IL-18 promoter is significantly correlated with risk of CA in NSC patients.

Plasma Bleomycin Concentrations during Electrochemotherapeutic Treatment of Fibropapillomas in Green Turtles Chelonia mydas

Fibropapillomatosis of sea turtles is traditionally treated with surgical debulking techniques that are often associated with prolonged healing and tumor recurrence. Electrochemotherapy was recently described for green turtles Chelonia mydas and can be an alternative to surgery and even general anesthesia. The objectives of this study were to replicate an electrochemotherapy protocol from a previous report and add plasma bleomycin analysis to the treatment. After bleomycin injection into similarly sized tumors of two green turtles and immediate electroporation at two time points, plasma bleomycin reached detectable concentrations that were considerably lower than those found in human studies. At 3 months posttherapy, no healing complications or recurrences were encountered and only scar tissue remained. This study adds further support that electrochemotherapy with bleomycin has the potential to be used as an effective alternative treatment for this complex disease.

Novel Approaches for Vaccination Against HPV-Induced Cancers

To date, more than 5 % of all cancers are as a result of human papillomavirus (HPV) infection, and this incidence is increasing. Early recognition of disease is associated with good survival, but late presentation results in devastating consequences. Prevention is better than cure, and there are now successful prophylactic vaccination programmes in place. We discuss these and the prospect of therapeutic vaccinations in the near future to address a growing need for improved therapeutic options.

Haematological and immunophenotypic evaluation of peripheral blood cells of cattle naturally infected with bovine papillomavirus

Papillomaviruses are among the most widespread animal viruses, with many hosts harbouring multiple virus types. The present study aimed to evaluate the haematological and immunophenotypic profile of cattle infected with bovine papillomavirus (BPV). Blood samples were collected from 10 animals with clinical cutaneous BPV and without clinical papillomatosis (control). Haematological analysis demonstrated a significant reduction in haemoglobin and haematocrit for BPV-infected animals. The results also showed an increase of natural killer cells and a decrease of γδ⁺ T-cells and the CD4⁺/CD8⁺ ratio for the BPV group when compared to the control group. The infection was also found to stimulate a pro-inflammatory profile with the participation of CD8⁺T cells producing elevated IFN-γ and IL-17. These findings, although preliminary, provide a better understanding of the immune response of cattle infected with BPV.

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.

Viral Modulation of TLRs and Cytokines and the Related Immunotherapies for HPV-Associated Cancers

The modulation of the host innate immune system is a well-established carcinogenesis feature of several tumors, including human papillomavirus- (HPV-) related cancers. This virus is able to interrupt the initial events of the immune response, including the expression of Toll-like receptors (TLRs), cytokines, and inflammation. Both TLRs and cytokines play a central role in HPV recognition, cell maturation and differentiation as well as immune signalling. Therefore, the imbalance of this sensitive control of the immune response is a key factor for developing immunotherapies, which strengthen the host immune system to accomplish an efficient defence against HPV and HPV-infected cells. Based on this, the review is aimed at exposing the HPV immune evasion mechanisms involving TLRs and cytokines and at discussing existing and potential immunotherapeutic TLR- and cytokine-related tools.

Targeted Therapy in Head and Neck Cancer: An Update on Current Clinical Developments in Epidermal Growth Factor Receptor-Targeted Therapy and Immunotherapies

Most patients diagnosed with head and neck squamous cell carcinoma (HNSCC) will present with locally advanced disease, requiring multimodality therapy. Despite this curative approach, a significant subset of these patients will develop locoregional failure and/or distant metastases. Despite significant progress in the treatment and subsequent prognosis of locally advanced HNSCC, the prognosis of those patients with recurrent and/or metastatic (R/M) HNSCC is poor, with short-lived responses to palliative chemotherapy and few therapeutic agents available. The discovery of the integral role of epidermal growth factor receptor overexpression in the pathogenesis of HNSCC, coupled with emerging data on the role of tumor evasion of the immune system, has opened new pathways in the development of novel therapeutic agents for the treatment of R/M HNSCC. As a result, cetuximab, a monoclonal antibody targeting epidermal growth factor receptor, as well as pembrolizumab and nivolumab, monoclonal antibodies targeting programmed cell death 1 (PD-1), are now US Food and Drug Administration approved for the treatment of R/M HNSCC. This review will detail the data supporting the use of these agents, as well as clinical trials evaluating the efficacy of other novel and promising drugs.

Impact of genetic variations and transcriptional alterations of HLA class I genes on cervical cancer pathogenesis

In a novel attempt to understand the variations in DNA sequences underlying HLA class I alleles associated with HPV16-related CaCx, we determined the alleles by reconstructing SNP-based haplotypes from resequencing of the most polymorphic exons 2 and 3 of HLA-A, HLA-B and HLA-C. We also determined the impact of SNPs and transcriptional alterations of the genes on CaCx. A high density of SNPs was identified from resequencing. HLA expression was determined by real-time PCR. We identified that even a single associated HLA allele had many underlying SNP-based haplotypes. Out of the most frequent (≥5%) HLA class I alleles, HLA-B*40:06 and HLA-B*15:02 respectively imparted significant risk towards and protection from CaCx as well as HPV16 infection. Employing median-joining networks to detect clusters of sequence-variations for specific HLA alleles, we found the protective SNP-based signature, GAATTTA, in all SNP-based haplotypes of HLA-B*15:02 allele. The signature was derived from seven SNPs within HLA-B which were newly associated with the disease. Contrarily, similarly derived risk-signature, TTGCGCC, mapped only to 52% of SNP-based haplotypes of HLA-B*40:06 allele. This indicated that all SNP-based haplotypes underlying a particular associated HLA allele might or might not have a single signature of risk/protection. HLA-A, HLA-B and HLA-C expressions were downregulated among CaCx cases compared to asymptomatic infections and HPV-negative controls. HLA-A and HLA-B were repressed in both cases harbouring episomal and integrated HPV16, whereas HLA-C in only the latter. Novel genetic variations and differential downregulation-patterns of HLA class I have a significant bearing on HPV16-related CaCx pathogenesis.

Defining an inflamed tumor immunophenotype in recurrent, metastatic squamous cell carcinoma of the head and neck

OBJECTIVES

Immune checkpoint inhibitors have demonstrated clinical benefit in recurrent, metastatic (R/M) squamous cell carcinoma of the head and neck (SSCHN), but lacking are biomarkers that predict response. We sought to define an inflamed tumor immunophenotype in this R/M SCCHN population and correlate immune metrics with clinical parameters and survival.

METHODS

Tumor samples were prospectively acquired from 34 patients to perform multiparametric flow cytometry and multidimensional clustering analysis integrated with next-generation sequencing data, clinical parameters and outcomes.

RESULTS

We identified an inflamed subgroup of tumors with prominent CD8+ T cell infiltrates and high PD-1/TIM3 co-expression independent of clinical variables, with improved survival compared with a non-inflamed subgroup (median overall survival 84.0 vs. 13.0months, p=0.004). The non-inflamed subgroup demonstrated low CD8+ T cells, low PD-1/TIM3 co-expression, and higher T_regs. Overall non-synonymous mutational burden did not correlate with response to PD-1 blockade in a subset of patients.

CONCLUSION

R/M SCCHN patients with an inflamed tumor immunophenotype demonstrate improved survival. Further prospective studies are needed to validate these findings and explore the use of immunophenotype to guide patient selection for immunotherapeutic approaches.

The human papillomavirus E7 oncoprotein as a regulator of transcription

High-risk human papillomaviruses (HPVs) encode oncoproteins which manipulate gene expression patterns in the host keratinocytes to facilitate viral replication, regulate viral transcription, and promote immune evasion and persistence. In some cases, oncoprotein-induced changes in host cell behavior can cause progression to cancer, but a complete picture of the functions of the viral oncoproteins in the productive HPV life cycle remains elusive. E7 is the HPV-encoded factor most responsible for maintaining cell cycle competence in differentiating keratinocytes. Through interactions with dozens of host factors, E7 has an enormous impact on host gene expression patterns. In this review, we will examine the role of E7 specifically as a regulator of transcription. We will discuss mechanisms of regulation of cell cycle-related genes by E7 as well as genes involved in immune regulation, growth factor signaling, DNA damage responses, microRNAs, and others pathways. We will also discuss some unanswered questions about how transcriptional regulation by E7 impacts the biology of HPV in both benign and malignant conditions.

Immunotherapy and targeted therapy for cervical cancer: an update

The prognosis of patients with metastatic cervical cancer is poor with a median survival of 8-13 months. Despite the potency of chemotherapeutic drugs, this treatment is rarely curative and should be considered palliative only. In the last few years, a better understanding of Human papillomavirus tumor-host immune system interactions and the development of new therapeutics targeting immune check points have renewed interest in the use of immunotherapy in cervical cancer patients. Moreover, next generation sequencing has emerged as an attractive option for the identification of actionable driver mutations and other markers. In this review, we provide background information on the molecular biology of cervical cancer and summarize immunotherapy studies, targeted therapies, including those with angiogenesis inhibitors and tyrosine kinase inhibitors recently completed or currently on-going in cervical cancer patients.

Immunology and Immunotherapy of Head and Neck Cancer

The immune system plays a key role in the development, establishment, and progression of head and neck squamous cell carcinoma (HNSCC). A greater understanding of the dysregulation and evasion of the immune system in the evolution and progression of HNSCC provides the basis for improved therapies and outcomes for patients. HNSCC cells evade the host immune system through manipulation of their own immunogenicity, production of immunosuppressive mediators, and promotion of immunomodulatory cell types. Through the tumor's influence on the microenvironment, the immune system can be exploited to promote metastasis, angiogenesis, and growth. This article provides a brief overview of key components of the immune infiltrating cells in the tumor microenvironment, reviewing immunological principles related to head and neck cancer, including the concept of cancer immunosurveillance and immune escape. Current immunotherapeutic strategies and emerging results from ongoing clinical trials are presented.

HPV-Associated Head and Neck Cancer: Unique Features of Epidemiology and Clinical Management

Human papillomavirus (HPV) is a recently identified causative agent for a subset of head and neck cancers, primarily in the oropharynx, and is largely responsible for the rising worldwide incidence of oropharyngeal cancer (OPC). Patients with HPV-positive OPC have distinct risk factor profiles and generally have a better prognosis than patients with traditional, HPV-negative, head and neck cancer. Concurrent chemotherapy and radiation is a widely accepted primary treatment modality for many patients with HPV-positive OPC. However, recent advances in surgical modalities, including transoral laser and robotic surgery, have led to the reemergence of primary surgical treatment for HPV-positive patients. Clinical trials are under way to determine optimal treatment strategies for the growing subset of patients with HPV-positive OPC. Similarly, identifying those patients with HPV-positive cancer who are at risk for recurrence and poor survival is critical in order to tailor individual treatment regimens and avoid potential undertreatment.

HPV16-E7 expression in squamous epithelium creates a local immune suppressive environment via CCL2- and CCL5- mediated recruitment of mast cells

Human Papillomavirus (HPV) 16 E7 protein promotes the transformation of HPV infected epithelium to malignancy. Here, we use a murine model in which the E7 protein of HPV16 is expressed as a transgene in epithelium to show that mast cells are recruited to the basal layer of E7-expressing epithelium, and that this recruitment is dependent on the epithelial hyperproliferation induced by E7 by inactivating Rb dependent cell cycle regulation. E7 induced epithelial hyperplasia is associated with increased epidermal secretion of CCL2 and CCL5 chemokines, which attract mast cells to the skin. Mast cells in E7 transgenic skin, in contrast to those in non-transgenic skin, exhibit degranulation. Notably, we found that resident mast cells in E7 transgenic skin cause local immune suppression as evidenced by tolerance of E7 transgenic skin grafts when mast cells are present compared to the rejection of mast cell-deficient E7 grafts in otherwise competent hosts. Thus, our findings suggest that mast cells, recruited towards CCL2 and CCL5 expressed by epithelium induced to proliferate by E7, may contribute to an immunosuppressive environment that enables the persistence of HPV E7 protein induced pre-cancerous lesions.

HLA-G 3' untranslated region polymorphisms influence the susceptibility for human papillomavirus infection

Human leukocyte antigen (HLA)-G molecule acts as a potential factor for the regulation of immune responses and its expression in virus-infected cells may enable them to escape immunosurveillance. Besides its polymorphic promoter region, the 3' untranslated region (UTR) seems to play an important role in regulating HLA-G expression. In this study, we investigated the influence of HLA-G 14 bp (rs66554220) and +3142 (rs1063320) polymorphisms in 179 women with active human papillomavirus (HPV) infection and 143 age-matched, unrelated, HPV-negative, normal Chinese Han population. Our findings showed that frequency of the allele +3142 C [31.3% vs 44.4%, odds ratio (OR) = 0.57, Pc < 0.01] and the genotype +3142 CC (10.6% vs 21.7%, OR = 0.43, Pc = 0.012) was significantly decreased in HPV infected patients compared with normal controls. Furthermore, the haplotype -14 bp/C was associated with a reduced risk for HPV infection (OR = 0.57, Pc = 0.001). Our findings also showed that HLA-G homozygous +14 bp/+14 bp genotype was significantly associated with an increased risk for HPV18 infection (OR = 12.95, P < 0.01), whereas HLA-G heterozygous +14 bp/-14 bp genotype increased risk for HPV58 (OR = 5.55, P < 0.05). Furthermore, frequency of the haplotype +14 bp/G was significantly increased in HPV18 infected patients (60.0% vs 27.3%, OR = 4.00, Pc < 0.05). Taken together, our results supported a role of the HLA-G 3' UTR polymorphisms as a susceptible factor for the active HPV infection, and suggested a possible interference of the HLA-G molecule in the response to virus infection.

Immunologic treatments for precancerous lesions and uterine cervical cancer

Development of HPV-associated cancers not only depends on efficient negative regulation of cell cycle control that supports the accumulation of genetic damage, but also relies on immune evasion that enable the virus to go undetected for long periods of time. In this way, HPV-related tumors usually present MHC class I down-regulation, impaired antigen-processing ability, avoidance of T-cell mediated killing, increased immunosuppression due to Treg infiltration and secrete immunosuppressive cytokines. Thus, these are the main obstacles that immunotherapy has to face in the treatment of HPV-related pathologies where a number of different strategies have been developed to overcome them including new adjuvants. Although antigen-specific immunotherapy induced by therapeutic HPV vaccines was proved extremely efficacious in pre-clinical models, its progression through clinical trials suffered poor responses in the initial trials. Later attempts seem to have been more promising, particularly against the well-defined precursors of cervical, anal or vulvar cancer, where the local immunosuppressive milieu is less active. This review focuses on the advances made in these fields, highlighting several new technologies (such as mRNA vaccine, plant-derived vaccine). The most promising immunotherapies used in clinical trials are also summarized, along with integrated strategies, particularly promising in controlling tumor metastasis and in eliminating cancer cells altogether.

After the early promising clinical results, the development of therapeutic HPV vaccines need to be implemented and applied to the users in order to eradicate HPV-associated malignancies, eradicating existing perception (after the effectiveness of commercial preventive vaccines) that we have already solved the problem.

Interferons and their stimulated genes in the tumor microenvironment

Constitutive expression of interferons (IFNs) and activation of their signaling pathways have pivotal roles in host responses to malignant cells in the tumor microenvironment. IFNs are induced by the innate immune system and in tumors through stimulation of Toll-like receptors (TLRs) and through other signaling pathways in response to specific cytokines. Although in the oncologic context IFNs have been thought of more as exogenous pharmaceuticals, the autocrine and paracrine actions of endogenous IFNs probably have even more critical effects on neoplastic disease outcomes. Through high-affinity cell surface receptors, IFNs modulate transcriptional signaling, leading to regulation of more than 2,000 genes with varying patterns of temporal expression. Induction of the gene products by both unphosphorylated and phosphorylated STAT1 after ligand binding results in alterations in tumor cell survival, inhibition of angiogenesis, and augmentation of actions of T, natural killer (NK), and dendritic cells. The interferon-stimulated gene (ISG) signature can be a favorable biomarker of immune response but, in a seemingly paradoxical finding, a specific subset of the full ISG signature indicates an unfavorable response to DNA-damaging interventions such as radiation. IFNs in the tumor microenvironment thus can alter the emergence, progression, and regression of malignancies.

Urban legends series: oral manifestations of HIV infection

Human immunodeficiency virus-related oral lesions (HIV-OLs), such as oral candidiasis (OC) and oral hairy leukoplakia (OHL), have been recognized as indicators of immune suppression since the beginning of the global HIV epidemic. The diagnosis and management of HIV disease and spectrum of opportunistic infection has changed over the past 30 years as our understanding of the infection has evolved. We investigated the following controversial topics: (i) Are oral manifestations of HIV still relevant after the introduction of highly active antiretroviral therapy (HAART)? (ii) Can we nowadays still diagnose HIV infection through oral lesions? (iii) Is the actual classification of oral manifestations of HIV adequate or does it need to be reviewed and updated? (iv) Is there any novelty in the treatment of oral manifestations of HIV infection? Results from extensive literature review suggested the following: (i) While HAART has resulted in significant reductions in HIV-OLs, many are still seen in patients with HIV infection, with OC remaining the most common lesion. While the relationship between oral warts and the immune reconstitution inflammatory syndrome is less clear, the malignant potential of oral human papillomavirus infection is gaining increasing attention. (ii) Effective antiretroviral therapy has transformed HIV from a fatal illness to a chronic manageable condition and as a result expanded screening policies for HIV are being advocated both in developed and in developing countries. Affordable, reliable, and easy-to-use diagnostic techniques have been recently introduced likely restricting the importance of HIV-OLs in diagnosis. (iii) The 1993 EC-Clearinghouse classification of HIV-OLs is still globally used despite controversy on the relevance of periodontal diseases today. HIV-OL case definitions were updated in 2009 to facilitate the accuracy of HIV-OL diagnoses by non-dental healthcare workers in large-scale epidemiologic studies and clinical trials. (iv) Research over the last 6 years on novel modalities for the treatment of HIV-OLs has been reported for OC and OHL.

Expression of nonclassical molecule human leukocyte antigen-G in oral lesions

INTRODUCTION

Human leukocyte antigen (HLA)-G is a nonclassic class I molecule that acts as a modulator of immune responses, and the expression of these molecules in virus-infected cells has been associated with subversion of the immune response.

OBJECTIVE

In this study, we performed a cross-sectional study, systematically comparing the expression of the HLA-G in benign, premalignant, and malignant oral lesions and correlating it with the presence of high-risk and low-risk human papillomavirus (HPV) types. SPECIMENS AND METHODS: Oral biopsies were collected from 51 patients and analyzed by immunohistochemistry using anti-HLA-G antibody. Human papillomavirus detection and typing from oral biopsies were obtained by polymerase chain reaction using GP5+/GP6+ and specific primers.

RESULTS

The 51 biopsies were stratified into 3 groups according to lesion grade: oral benign lesions (oral hyperplasia and papilloma, n = 16), oral premalignant lesions (oral leukoplakia with dysplasia and lichen planus, n = 17), and malignant lesions (oral squamous cell carcinoma, n = 18). Human leukocyte antigen-G overexpression was mainly observed in benign and premalignant oral lesions but was not related to HPV infection (P > .05). On the other hand, HPV DNA was detected in 24 (47%) oral lesions, mainly in benign and premalignant lesions, with the most frequent type detected being high-risk HPV type.

CONCLUSION

The HLA-G molecule was expressed in a significant number of benign oral lesions and was not correlated with HPV infection or oral cancer.

S100, CD68, and MHC class II molecule expression in cervical high- and low-grade HPV-induced lesions

INTRODUCTION

Some human papillomavirus (HPV) types are involved in malignant processes in the cervical epithelium, with 99% of cases attributed to oncogenic HPV infection. This study aimed to detect S100, CD68, and major histocompatibility complex class II (MHC-II) molecules in cervical uterine epithelial samples in patients with high- and low-grade lesions induced by HPV.

METHODS

Fifty-eight samples from patients who were confirmed positive or negative for high-risk oncogenic HPV DNA, had histopathological diagnosis of cervical intraepithelial neoplasia (CIN) of grades I, II, or III, or were negative for intraepithelial lesion or malignancy were subjected to immunohistochemistry reaction to S100 protein, CD68, and MHC-II (HLA-DR alpha chain).

RESULTS

The presence of MHC-II predominated in samples exhibiting histopathological alterations (p < 0.05). S100 detection was more numerous in carcinoma samples (CIN III) (75%). Presence of this protein correlated significantly (p < 0.05) with histopathological findings and viral load.

CONCLUSIONS

A small expression of CD68 was observed, which may be explained by the observation in our study having been made on random microscopic fields and not on specific areas. The findings, such as the presence of S100 protein and MHC-II expression in samples with histological alterations, could suggest that the immune system fails to control HPV replication at the early stages of infection. Further studies with larger prospective data are necessary to confirm this result.

Papillomavirus E5: the smallest oncoprotein with many functions

Papillomaviruses (PVs) are established agents of human and animal cancers. They infect cutaneous and mucous epithelia. High Risk (HR) Human PVs (HPVs) are consistently associated with cancer of the uterine cervix, but are also involved in the etiopathogenesis of other cancer types. The early oncoproteins of PVs: E5, E6 and E7 are known to contribute to tumour progression. While the oncogenic activities of E6 and E7 are well characterised, the role of E5 is still rather nebulous. The widespread causal association of PVs with cancer makes their study worthwhile not only in humans but also in animal model systems. The Bovine PV (BPV) system has been the most useful animal model in understanding the oncogenic potential of PVs due to the pivotal role of its E5 oncoprotein in cell transformation. This review will highlight the differences between HPV-16 E5 (16E5) and E5 from other PVs, primarily from BPV. It will discuss the targeting of E5 as a possible therapeutic agent.

Safety and immunogenicity of BPV-1 L1 virus-like particles in a dose-escalation vaccination trial in horses

REASONS FOR PERFORMING STUDY

Infection with bovine papillomaviruses types 1 and 2 (BPV-1, BPV-2) can lead to the development of therapy-resistant skin tumours termed sarcoids and possibly other skin diseases in equids. Although sarcoids seriously compromise the welfare of affected animals and cause considerable economic losses, no prophylactic vaccine is available to prevent this common disease. In several animal species and man, immunisation with papillomavirus-like particles (VLP) has been shown to protect efficiently from papillomaviral infection.

HYPOTHESIS

BPV-1 L1 VLPs may constitute a safe and highly immunogenic vaccine candidate for protection of horses against BPV-1/-2-induced disease.

METHODS

Three groups of 4 horses each received 50, 100 or 150 µg of BPV-1 L1 VLPs, respectively, on Days 0, 28 and 168. Three control horses received adjuvant only. Horses were monitored on a daily basis for one week after each immunisation and then in 2 week intervals. Sera were collected immediately before, 2 weeks after each vaccination and one and 2 years after the final boost and analysed by pseudovirion neutralisation assay.

RESULTS

None of the horses showed adverse reactions upon vaccination apart from mild and transient swelling in 2 individuals. Irrespective of the VLP dose, all VLP-immunised horses had developed a BPV-1-neutralising antibody titre of ≥ 1600 plaque forming units (pfu)/ml 2 weeks after the third vaccination. Eight of 10 trial horses still available for follow-up had neutralising antibody titres ≥ 1600 pfu/ml one year and ≥ 800 pfu/ml 2 years after the last immunisation.

CONCLUSION

Intramuscular BPV-1 L1 VLP vaccination in horses is safe and results in a long-lasting antibody response against BPV-1. Neutralisation titres were induced at levels that correlate with protection in experimental animals and man.

POTENTIAL RELEVANCE

BPV-1 L1 VLPs constitute a promising vaccine candidate for prevention of BPV-1/-2-induced disease in equids.

Persistence of human papillomavirus infection: keys to malignant progression

Human papillomaviruses (HPVs) are the etiologic agents of cervical and other epithelial cancers. Persistence of infections by high-risk HPV types is the single greatest risk factor for malignant progression. Although prophylactic vaccines have been developed that target high-risk HPV types, there is a continuing need to understand better the virus-host interactions that underlie persistent benign infection and progression to cancer. In this review we summarize the molecular events that facilitate the differentiation-dependent HPV life cycle, how the life cycle is organized to facilitate virus persistence, and how the activities of HPV regulatory proteins result in malignancy.

HPV-16 E5 down-regulates expression of surface HLA class I and reduces recognition by CD8 T cells

HPV-16 is the major causes of cervical cancer. Persistence of infection is a necessary event for progression of the infection to cancer. Among other factors, virus persistence is due the viral proteins fighting the immune response. HPV-16 E5 down-regulates MHC/HLA class I, which is much reduced on the cell surface and accumulates in the Golgi apparatus in cells expressing E5. This effect is observed also in W12 cells, which mimic early cervical intraepithelial progression to cervical cancer. The functional effect of MHC I down-regulation on human CD8 T cells is not known, because of the need for HLA-matched, HPV-specific T cells that recognise E5 expressing-cells. Here we employ a heterologous cell/MHC I system which uses mouse cells expressing both E5 and HLA-A2, and A2-restricted CTLs; we show that the E5-induced reduction of HLA-A2 has a functional impact by reducing recognition of E5 expressing cells by HPV specific CD8+ T cells.

A conserved E7-derived cytotoxic T lymphocyte epitope expressed on human papillomavirus 16-transformed HLA-A2+ epithelial cancers

Human Papillomavirus 16 (HPV-16) has been identified as the causative agent of 50% of cervical cancers and many other HPV-associated tumors. The transforming potential/tumor maintenance capacity of this high risk HPV is mediated by two viral oncoproteins, E6 and E7, making them attractive targets for therapeutic vaccines. Of 21 E6 and E7 peptides computed to bind HLA-A*0201, 10 were confirmed through TAP-deficient T2 cell HLA stabilization assay. Those scoring positive were investigated to ascertain which were naturally processed and presented by surface HLA molecules for CTL recognition. Because IFNγ ELISpot frequencies from healthy HPV-exposed blood donors against HLA-A*0201-binding peptides were unable to identify specificities for tumor targeting, their physical presence among peptides eluted from HPV-16-transformed epithelial tumor HLA-A*0201 immunoprecipitates was analyzed by MS(3) Poisson detection mass spectrometry. Only one epitope (E7(11-19)) highly conserved among HPV-16 strains was detected. This 9-mer serves to direct cytolysis by T cell lines, whereas a related 10-mer (E7(11-20)), previously used as a vaccine candidate, was neither detected by MS(3) on HPV-transformed tumor cells nor effectively recognized by 9-mer specific CTL. These data underscore the importance of precisely defining CTL epitopes on tumor cells and offer a paradigm for T cell-based vaccine design.

CD1d, a sentinel molecule bridging innate and adaptive immunity, is downregulated by the human papillomavirus (HPV) E5 protein: a possible mechanism for immune evasion by HPV

CD1d and CD1d-restricted natural killer T (NKT) cells serve as a natural bridge between innate and adaptive immune responses to microbes. CD1d downregulation is utilized by a variety of microbes to evade immune detection. We demonstrate here that CD1d is downregulated in human papillomavirus (HPV)-positive cells in vivo and in vitro. CD1d immunoreactivity was strong in HPV-negative normal cervical epithelium but absent in HPV16-positive CIN1 and HPV6-positive condyloma lesions. We used two cell lines for in vitro assay; one was stably CD1d-transfected cells established from an HPV-negative cervical cancer cell line, C33A (C33A/CD1d), and the other was normal human vaginal keratinocyte bearing endogenous CD1d (Vag). Flow cytometry revealed that cell surface CD1d was downregulated in both C33A/CD1d and Vag cells stably transfected with HPV6 E5 and HPV16 E5. Although the steady-state levels of CD1d protein decreased in both E5-expressing cell lines compared to empty retrovirus-infected cells, CD1d mRNA levels were not affected. Confocal microscopy demonstrated that residual CD1d was not trafficked to the E5-expressing cell surface but colocalized with E5 near the endoplasmic reticulum (ER). In the ER, E5 interacted with calnexin, an ER chaperone known to mediate folding of CD1d. CD1d protein levels were rescued by the proteasome inhibitor, MG132, indicating a role for proteasome-mediated degradation in HPV-associated CD1d downregulation. Taken together, our data suggest that E5 targets CD1d to the cytosolic proteolytic pathway by inhibiting calnexin-related CD1d trafficking. Finally, CD1d-mediated production of interleukin-12 from the C33A/CD1d cells was abrogated in both E5-expressing cell lines. Decreased CD1d expression in the presence of HPV E5 may help HPV-infected cells evade protective immunological surveillance.

All 4 di-leucine motifs in the first hydrophobic domain of the E5 oncoprotein of human papillomavirus type 16 are essential for surface MHC class I downregulation activity and E5 endomembrane localization

The E5 oncoprotein of human papillomavirus type 16 downregulates surface MHC Class I and interacts with the heavy chain of the MHC complex via the first hydrophobic domain, believed to form the first helical transmembrane region (TM1) of E5. TM1 contains 4 equally spaced di-leucine (LL1-LL4) motifs. Di-leucine motifs have been implicated in protein-protein interactions and as localization signals. To see if any of the 4 di-leucine motifs of TM1 are involved in MHC downregulation by E5, we mutated each LL pair into valine pairs (VV1-VV4), as mutation of leucine to valine is not expected to cause major structural alterations in E5. We found that all 4 mutations disrupted the intracellular location of E5 and abrogated its MHC I downregulating activity; however VV2 and VV4 mutants were still able to interact physically with the MHC I heavy chain (HC) in vitro, while VV1 and VV3 mutants had lost this activity. We conclude that LL1 and LL3 are necessary for the interaction with HC, but LL2 and LL4 are not. However all 4 LL motifs are responsible for the proper localization of E5 in the Golgi/ER, and the displacement of E5 from this location contributes to the abrogation of MHC I downregulation. LL1 and LL3 motifs are expected to be on one face of the TM1 helix and LL2 and LL4 on the opposite face. We propose that E5 interacts with HC via LL1 and LL3 and that all 4 di-leucine motifs act as a targeting signal.

The canine papillomavirus e5 protein signals from the endoplasmic reticulum

The recently discovered Canis familiaris papillomavirus (PV) type 2 (CfPV2) provides a unique opportunity to study PV gene functions in vitro and in vivo. Unlike the previously characterized canine oral PV, CfPV2 contains an E5 open reading frame and is associated with progression to squamous cell carcinoma. In the current study, we have expressed and characterized the CfPV2-encoded E5 protein, a small, hydrophobic, 41-amino-acid polypeptide. We demonstrate that, similar to the E5 protein from high-risk human PV type 16, the CfPV2 E5 protein is localized in the endoplasmic reticulum (ER) and that its expression decreases keratinocyte proliferation and cell life span. E5 expression also increases the percentage of cells in the G(1) phase of the cell cycle, with a concomitant decrease in the percentage of cells in S phase. To identify a potential mechanism for E5-mediated growth inhibition from the ER, we developed a real-time PCR method to quantify the splicing of XBP1 mRNA as a measure of ER stress. We found that the CfPV2 E5 protein induced ER stress and that this, as well as the observed growth inhibition, is tempered significantly by coexpression of the CfPV2 E6 and E7 genes. It is possible that the spatial/temporal regulation of E6/E7 gene expression during keratinocyte differentiation might therefore modulate E5 activity and ER stress.

HLA-G polymorphisms in women with squamous intraepithelial lesions harboring human papillomavirus

Human papillomavirus (HPV) infection is etiologically associated with low- (LSIL) and high-grade squamous intraepithelial lesions (HSIL) and with cervical cancer. The progression or regression of the lesions may depend, among other factors, on the host heritable immune response. Because human leukocyte antigen (HLA)-G molecules are involved in the modulation of innate and adaptive immune responses, and because no previous studies have evaluated HLA-G polymorphism in patients with SIL, we conducted a study to assess the association between HLA-G polymorphisms and cervical lesions harboring HPV infection. Cervico-vaginal scrapings and blood samples were collected from 125 women with SIL (68 LSIL and 57 HSIL) and from 94 healthy women without HPV infection and cytological abnormalities. HPV type and HLA-G polymorphisms in exons 2, 3 and 8 (14 bp insertion/deletion) were evaluated by PCR methodology, and digested with restriction endonucleases. The Genepop software and the EM and PHASE algorithms were used for statistical analysis. A significant protective association was observed between the presence of the G(*)0103 allele and SIL and between the G0101/G0104 genotype and HSIL in the group of patients compared to control. The presence of the G0104/+14 bp and G0104/-14 bp haplotypes conferred susceptibility to SIL compared to control. In addition, patients possessing the G0104/+14 bp haplotype and harboring HPV-16 and -18 co-infections were particularly associated with HSIL. These findings suggest that HLA-G polymorphisms may be associated with HPV infection and SIL, consequently representing a profile of predisposition to cervical cancer.

Binding of human papillomavirus type 16 to heparan sulfate is inhibited by mucosal antibodies from patients with low-grade squamous intraepithelial lesions but not from cervical cancer patients

Mucosal antibodies against human papillomavirus type 16 (HPV16) capsids have been detected in infected women. To determine whether these antibodies recognize and block the receptor site mediating attachment of HPV16 to heparan sulfate, mucus samples from 126 HPV16-associated low-grade squamous intraepithelial lesion (LSIL) and 85 cervical cancer patients, previously found to react to HPV16 virus-like particles (VLP), and 101 normal controls were tested in an inhibition assay, using HPV16 VLP and heparan sulfate proteoglycan-coated plates. Inhibition levels of 9.3-67.2% were mediated by type-specific antibodies in 94.4% of LSIL patients. Cervical cancer cases showed significantly lower levels of inhibition than LSIL samples (P < 0.0001). The potential of antibodies to inhibit infection was explored in a pseudoinfection system using HPV16 pseudovirions. Inhibition of pseudoinfection by LSIL samples was significantly higher than that observed in the controls (P < 0.001) and cervical cancer cases (P < 0.005). These results indicate that mucosal antibodies inhibiting binding of VLP to heparan sulfate are developed in most LSIL patients, but are hardly present in cervical cancer patients.