Interaction of human papillomavirus type 11 E7 protein with TAP-1 results in the reduction of ATP-dependent peptide transport

Immune escape of head and neck cancer mediated by the impaired MHC-I antigen presentation pathway

Tumor immune evasion is a hallmark of Head and Neck Cancers. The advent of immune checkpoint inhibitors (ICIs) in the first-line setting has transformed the management of these tumors. Unfortunately, the response rate of Head and Neck Squamous Cell Carcinomas (HNSCC) to ICIs is below 15%, regardless of the human papillomavirus (HPV) status, which might be partially related with impaired antigen presentation machinery (APM). Mechanistically, HNSCC cells are usually defective in the expression of MHC-I associated APM, while this transcriptional pathway is critical for the activation of tumor-killing effector T-cells. To specifically illuminate the phenomenon and seek for therapeutic strategies, this review summarizes the most recently identified role of genetic and functional dysregulation of the MHC-I pathway, specifically through changes at the genetic, epigenetic, post-transcriptional, and post-translational levels, which substantially contributes to HNSCC immune escape and ICI resistance. Several treatment modalities can be potentially exploited to restore APM signaling in tumors, which improves anti-tumor immunity through the activation of interferons, vaccines or rimantadine against HPV and the inhibition of EGFR, SHP-2, PI3K and MEK. Additionally, the combinatorial use of radiotherapy or cytotoxic agents with ICIs can synergize to potentiate APM signaling. Future directions would include further dissection of MHC-I related APM signaling in HNSCC and whether reversing this inhibition in combination with ICIs would elicit a more robust immune response leading to improved response rates in HNSCC. Therapeutic approaches to restore the MHC-I antigen presentation machinery in Head and Neck Cancer. (Red color texts represent the according strategies and the outcomes).

The Hallmarks of Cervical Cancer: Molecular Mechanisms Induced by Human Papillomavirus

Human papillomaviruses (HPVs) and, specifically, high-risk HPVs (HR-HPVs) are identified as necessary factors in the development of cancer of the lower genital tract, with CaCU standing out as the most prevalent tumor. This review summarizes ten mechanisms activated by HR-HPVs during cervical carcinogenesis, which are broadly associated with at least seven of the fourteen distinctive physiological capacities of cancer in the newly established model by Hanahan in 2022. These mechanisms involve infection by human papillomavirus, cellular tropism, genetic predisposition to uterine cervical cancer (CaCU), viral load, viral physical state, regulation of epigenetic mechanisms, loss of function of the E2 protein, deregulated expression of E6/E7 oncogenes, regulation of host cell protein function, and acquisition of the mesenchymal phenotype.

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.

Preclinical Models of Laryngeal Papillomavirus Infection: A Scoping Review

OBJECTIVE

Laryngeal human papillomavirus (HPV) infection causes recurrent respiratory papillomatosis (RRP) and accounts for up to 25% of laryngeal cancers. Lack of satisfactory preclinical models is one reason that treatments for these diseases are limited. We sought to assess the literature describing preclinical models of laryngeal papillomavirus infection.

DATA SOURCES

PubMed, Web of Science, and Scopus were searched from the inception of database through October 2022.

REVIEW METHODS

Studies searched were screened by two investigators. Eligible studies were peer-reviewed, published in English, presented original data, and described attempted models of laryngeal papillomavirus infection. Data examined included type of papillomavirus, infection model, and results including success rate, disease phenotype, and viral retention.

RESULTS

After screening 440 citations and 138 full-text studies, 77 studies published between 1923 and 2022 were included. Models used low-risk HPV or RRP (n = 51 studies), high-risk HPV or laryngeal cancer (n = 16), both low- and high-risk HPV (n = 1), and animal papillomaviruses (n = 9). For RRP, 2D and 3D cell culture models and xenografts retained disease phenotypes and HPV DNA in the short term. Two laryngeal cancer cell lines were consistently HPV-positive in multiple studies. Animal laryngeal infections with animal papillomaviruses resulted in disease and long-term retention of viral DNA.

CONCLUSIONS

Laryngeal papillomavirus infection models have been researched for 100 years and primarily involve low-risk HPV. Most models lose viral DNA after a short duration. Future work is needed to model persistent and recurrent diseases, consistent with RRP and HPV-positive laryngeal cancer.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:3256-3268, 2023.

Molecular Mechanisms of Carcinogenesis in Pediatric Airways Tumors

Primary tumors of the airways in the pediatric population are very rare entities. For this reason, little is known about the pathogenesis of these neoplasms. Understanding the biology has different practical implications: for example, it could help in the differential diagnosis, have a prognostic significance, or may lead to the development of a targeted therapy. The aim of this article is to present the current knowledge about pediatric airways tumors, focusing on the molecular mechanisms that cause the onset and progression of these neoplasms. After a brief introduction of epidemiology and clinical presentation, the tumorigenesis of the most frequent pediatric airways tumors will be described: Juvenile-onset recurrent respiratory papillomatosis (JORRP), Subglottic Hemangiona (SH), Rhabdomyosarcoma (RMS), and Mucoepidermoid carcinoma (MEC).

Clinical implications of alpha, beta, and gamma HPV infection in juvenile onset recurrent respiratory papillomatosis

PURPOSE

The aim of our study was to evaluate the prevalence of different HPV genera-alpha, beta and gamma-in Juvenile onset Recurrent Respiratory Papillomatosis (JoRRP) and examine the association of type and genus-specific viral features with the clinical outcome of disease.

METHODS

This retrospective observational study included consecutive patients with JoRRP who were treated in a referral centre between October 2000 and October 2020. All patients underwent cold excision and laser vaporisation of papillomatous lesions. Samples were analysed for the presence of 120 viral genotypes (22 alpha-HPV, 46 beta-HPV, 52 gamma-HPV) using a highly sensitive multiplex genotyping assay.

RESULTS

Twenty patients with JoRRP, aged 0.3-11 years, were included, with a median follow-up of 13.5 years. All samples were HPV DNA positive: 20 (100%) for alpha-HPV DNA; 7 (35%) for beta-HPV DNA; 0 for gamma-HPV DNA. Three groups were defined according to the number of infections: seven cases (35%) with HPV mono-infection; ten cases (50%) with HPV double-infection; three cases (15%) with ≥ 3 HPV infections. At diagnosis, patients with ≥ 3 HPV infections reported higher median Derkay's score than those with mono-infection (21 vs 14, P = 0.018). Number of HPV infections was also associated with clinical outcomes, with an average of 0.5 surgical procedures/year in patients with mono-infection, 1.2 for double-infection, 2.6 for ≥ 3 infections (P = 0.006).

CONCLUSION

Despite the small sample size, these preliminary data support an association between the number of different alpha and beta HPV co-infections and the clinical severity of the disease.

Potential role of micro ribonucleic acids in screening for anal cancer in human papilloma virus and human immunodeficiency virus related malignancies

Despite advances in antiretroviral treatment (ART), human immunodeficiency virus (HIV) continues to be a major global public health issue owing to the increased mortality rates related to the prevalent oncogenic viruses among people living with HIV (PLWH). Human papillomavirus (HPV) is the most common sexually transmitted viral disease in both men and women worldwide. High-risk or oncogenic HPV types are associated with the development of HPV-related malignancies, including cervical, penile, and anal cancer, in addition to oral cancers. The incidence of anal squamous cell cancers is increasing among PLWH, necessitating the need for reliable screening methods in this population at risk. In fact, the currently used screening methods, including the Pap smear, are invasive and are neither sensitive nor specific. Investigators are interested in circulatory and tissue micro ribonucleic acids (miRNAs), as these small non-coding RNAs are ideal biomarkers for early detection and prognosis of cancer. Multiple miRNAs are deregulated during HIV and HPV infection and their deregulation contributes to the pathogenesis of disease. Here, we will review the molecular basis of HIV and HPV co-infections and focus on the pathogenesis and epidemiology of anal cancer in PLWH. The limitations of screening for anal cancer and the need for a reliable screening program that involves specific miRNAs with diagnostic and therapeutic values is also discussed.

The human papillomavirus oncoproteins: a review of the host pathways targeted on the road to transformation

Persistent infection with high-risk human papillomaviruses (HR-HPVs) is the causal factor in over 99 % of cervical cancer cases, and a significant proportion of oropharyngeal and anogenital cancers. The key drivers of HPV-mediated transformation are the oncoproteins E5, E6 and E7. Together, they act to prolong cell-cycle progression, delay differentiation and inhibit apoptosis in the host keratinocyte cell in order to generate an environment permissive for viral replication. The oncoproteins also have key roles in mediating evasion of the host immune response, enabling infection to persist. Moreover, prolonged infection within the cellular environment established by the HR-HPV oncoproteins can lead to the acquisition of host genetic mutations, eventually culminating in transformation to malignancy. In this review, we outline the many ways in which the HR-HPV oncoproteins manipulate the host cellular environment, focusing on how these activities can contribute to carcinogenesis.

Vaccination against Nonmutated Neoantigens Induced in Recurrent and Future Tumors

Vaccination of patients against neoantigens expressed in concurrent tumors, recurrent tumors, or tumors developing in individuals at risk of cancer is posing major challenges in terms of which antigens to target and is limited to patients expressing neoantigens in their tumors. Here, we describe a vaccination strategy against antigens that were induced in tumor cells by downregulation of the peptide transporter associated with antigen processing (TAP). Vaccination against TAP downregulation-induced antigens was more effective than vaccination against mutation-derived neoantigens, was devoid of measurable toxicity, and inhibited the growth of concurrent and future tumors in models of recurrence and premalignant disease. Human CD8⁺ T cells stimulated with TAP^low dendritic cells elicited a polyclonal T-cell response that recognized tumor cells with experimentally reduced TAP expression. Vaccination against TAP downregulation-induced antigens overcomes the main limitations of vaccinating against mostly unique tumor-resident neoantigens and could represent a simpler vaccination strategy that will be applicable to most patients with cancer.

Immunological tolerance of low-risk HPV in recurrent respiratory papillomatosis

Recurrent respiratory papillomatosis (RRP) is characterized by benign exophytic lesions of the respiratory tract caused by the human papillomavirus (HPV), in particular low-risk HPV6 and HPV11. Aggressiveness varies greatly among patients. Surgical excision is the current standard of care for RRP, with adjuvant therapy used when surgery cannot control disease recurrence. Numerous adjuvant therapies have been used to control RRP with some success, but none are curative. Current literature supports a polarization of the adaptive immune response to a T helper type 2 (Th2)-like or T regulatory phenotype, driven by a complex interplay between innate immunity, adaptive immunity and HPV6/11 proteins. Additionally, certain immunogenetic polymorphisms can predispose individuals to an HPV6/11-tolerant microenvironment. As a result, immunomodulatory efforts are being made to restore the host immune system to a more balanced T cell phenotype and clear viral infection. Literature has shown exciting evidence for the role of HPV vaccination with Gardasil or Gardasil-9 as both primary prevention, by decreasing incidence through childhood vaccinations, and secondary prevention, by treating active RRP disease. Multi-institution randomized clinical trials are needed to better assess their efficacy as treatment for active disease. Interestingly, a DNA vaccine has recently shown in-vitro success in generating a more robust CD8⁺ T cell response. Furthermore, clinical trials for programmed death 1 (PD-1) inhibitors are under investigation for RRP management. Molecular insights into RRP, in particular the interplay between RRP and the immune system, are needed to advance our understanding of this disease and may lead to the identification of immunomodulatory agents to better manage RRP.

The diversity of the HLA-E-restricted peptide repertoire explains the immunological impact of the Arg107Gly mismatch

Human leukocyte antigen (HLA)-E molecules are potent inhibitors of NK cell-mediated killing. Low in polymorphisms, two alleles are widely expressed among diverse populations: HLA-E*01:01 and HLA-E*01:03. Both alleles are distinguished by one SNP resulting in the substitution Arg107Gly. Both alleles present a limited set of peptides derived from class I leader sequences physiologically; however, HLA-E*01:01 presents non-canonical peptides in the absence of HLA class I molecules. To further assess the functional differences between both alleles, we analyzed the peptide repertoire of HLA-E*01:03 by applying soluble HLA technology followed by mass-spectrometric peptide sequencing. HLA-E*01:03 restricted peptides showed a length of 9-17 amino acids and differed in their biophysical properties, no overlap in the peptide repertoire of both allelic variants could be observed; however, both alleles shared marginal peptides from the same proteomic content. Artificial APCs expressing empty HLA-E*01:01 or E*01:03 molecules were generated and stabilized using cognate HLA class I-derived peptide ligands to analyze the impact of residue 107 within the HLA-E heavy chain on the NKG2/CD94 receptor engagement. Differences in peptide stabilization could be translated to the density and half-life time of peptide-HLA-E molecules on the cell surface that subsequently impacted NK cell inhibition as verified by cytotoxicity assays. Taken together, these data illustrate functional differences of HLA-E allelic variants induced by a single amino acid. Furthermore, the function of HLA-E in pathophysiologic situations when the HLA processing machinery is interrupted seems to be more emphasized than previously described, implying a crucial role for HLA-E in tumor or viral immune episodes.

Langerhans cells from women with cervical precancerous lesions become functionally responsive against human papillomavirus after activation with stabilized Poly-I:C

Human papillomavirus (HPV)-mediated suppression of Langerhans cell (LC) function can lead to persistent infection and development of cervical intraepithelial neoplasia (CIN). Women with HPV-induced high-grade CIN2/3 have not mounted an effective immune response against HPV, yet it is unknown if LC-mediated T cell activation from such women is functionally impaired against HPV. We investigated the functional activation of in vitro generated LC and their ability to induce HPV16-specific T cells from CIN2/3 patients after exposure to HPV16 followed by treatment with stabilized Poly-I:C (s-Poly-I:C). LC from patients exposed to HPV16 demonstrated a lack of costimulatory molecule expression, inflammatory cytokine secretion, and chemokine-directed migration. Conversely, s-Poly-I:C caused significant phenotypic and functional activation of HPV16-exposed LC, which resulted in de novo generation of HPV16-specific CD8(+) T cells. Our results highlight that LC of women with a history of persistent HPV infection can present HPV antigens and are capable of inducing an adaptive T cell immune response when given the proper stimulus, suggesting that s-Poly-I:C compounds may be attractive immunomodulators for LC-mediated clearance of persistent HPV infection.

The interplay between HPV and host immunity in head and neck squamous cell carcinoma

Persistent infection with human papillomavirus (HPV) type 16 is a major risk factor for the development of head and neck squamous cell carcinoma (HNSCC), in particular oropharyngeal squamous cell carcinoma (OPSCC). The oropharyngeal epithelium differs from the mucosal epithelium at other commonly HPV16-infected sites (i.e., cervix and anogenital region) in that it is juxtaposed with the underlying lymphatic tissue, serving a key immunologic function in the surveillance of inhaled and ingested pathogens. Therefore, the natural history of infection and immune response to HPV at this site may differ from that at other anatomic locations. This review summarizes the literature concerning the adaptive immune response against HPV in the context of HNSCC, with a focus on the T-cell response. Recent studies have shown that a broad repertoire of tumor-infiltrating HPV-specific T-cells are found in nearly all patients with HPV-positive tumors. A systemic response is found in only a proportion of these. Furthermore, the local response is more frequent in OPSCC patients than in cervical cancer patients and HPV-negative OPSCC patients. Despite this, tumor persistence may be facilitated by abnormalities in antigen processing, a skewed T-helper cell response, and an increased local prevalence of T-regulatory cells. Nonetheless, the immunologic profile of HPV-positive vs. HPV-negative HNSCC is associated with a significantly better outcome, and the HPV-specific immune response is suggested to play a role in the significantly better response to therapy of HPV-positive patients. Immunoprofiling may prove a valuable prognostic tool, and immunotherapy trials targeting HPV are underway, providing hope for decreasing treatment-related toxicity.

HPV infection: immunological aspects and their utility in future therapy

High prevalence and mortality rates of cervical cancer create an imperative need to clarify the uniqueness of HPV (Human Papillomavirus) infection, which serves as the key causative factor in cervical malignancies. Understanding the immunological details and the microenvironment of the infection can be a useful tool for the development of novel therapeutic interventions. Chronic infection and progression to carcinogenesis are sustained by immortalization potential of HPV, evasion techniques, and alterations in the microenvironment of the lesion. Inside the lesion, Toll-like receptors expression becomes irregular; Langerhans cells fail to present the antigens efficiently, tumor-associated macrophages aggregate resulting in an unsuccessful immune response by the host. HPV products also downregulate the expression of microenvironment components which are necessary for natural-killer cells response and antigen presentation to cytotoxic cells. Additionally HPV promotes T-helper cell 2 (Th2) and T-regulatory cell phenotypes and reduces Th1 phenotype, leading to suppression of cellular immunity and lesion progression to cancer. Humoral response after natural infection is inefficient, and neutralizing antibodies are not adequate in many women. Utilizing this knowledge, new endeavors, such as therapeutic vaccination, aim to stimulate cellular immune response against the virus and alter the milieu of the lesion.

Human papillomavirus 16-encoded E7 protein inhibits IFN-γ-mediated MHC class I antigen presentation and CTL-induced lysis by blocking IRF-1 expression in mouse keratinocytes

Human papillomavirus 16 (HPV16) infection causes 50 % or more of cervical cancers in women. The HPV16 E7 oncogene is continuously expressed in infected epithelium with its oncogenicity linked to cervical cancer. The E7 protein is an ideal target in control of HPV infection through T-cell-mediated immunity. Using HPV16 E7-transgenic mouse keratinocytes (KCs-E7) to investigate T-cell-mediated immune responses, we have shown previously that HPV16-encoded E7 protein inhibits IFN-γ-mediated enhancement of MHC class I antigen processing and T-cell-induced target cell lysis. In this study, we found that HPV16 E7 suppresses IFN-γ-induced phosphorylation of STAT1((Tyr701)), leading to the blockade of interferon regulatory factor-1 (IRF-1) and transporter associated antigen processing subunit 1 (TAP-1) expression in KCs-E7. The results of a (51)Cr release assay demonstrated that IFN-γ-treated KCs-E7 escaped from CTL recognition because HPV16 E7 downregulated MHC class I antigen presentation on KCs. Restoration of IRF-1 expression in KCs-E7 overcame the inhibitory effect of E7 protein on IFN-γ-mediated CTL lysis and MHC class I antigen presentation on KCs. Our results suggest that HPV16 E7 interferes with the IFN-γ-mediated JAK1/JAK2/STAT1/IRF-1 signal transduction pathway and reduces the efficiency of peptide loading and MHC class I antigen presentation on KCs-E7. These results may reveal a new mechanism whereby HPV16 escapes from immune surveillance in vivo.

The papillomavirus E7 proteins

E7 is an accessory protein that is not encoded by all papillomaviruses. The E7 amino terminus contains two regions of similarity to conserved regions 1 and 2 of the adenovirus E1A protein, which are also conserved in the simian vacuolating virus 40 large tumor antigen. The E7 carboxyl terminus consists of a zinc-binding motif, which is related to similar motifs in E6 proteins. E7 proteins play a central role in the human papillomavirus life cycle, reprogramming the cellular environment to be conducive to viral replication. E7 proteins encoded by the cancer-associated alpha human papillomaviruses have potent transforming activities, which together with E6, are necessary but not sufficient to render their host squamous epithelial cell tumorigenic. This article strives to provide a comprehensive summary of the published research studies on human papillomavirus E7 proteins.

Regulation of immune responses to HPV infection and during HPV-directed immunotherapy

The recent development of vaccines prophylactic against human papillomavirus (HPV) infection has the potential to reduce the incidence of cervical cancer globally by up to 70% over the next 40 years, if universal immunization is adopted. As these prophylactic vaccines do not alter the natural history of established HPV infection, immunotherapies to treat persistent HPV infection and associated precancers would be of benefit to assist with cervical cancer control. Efforts to develop immuno-therapeutic vaccines have been hampered by the relative non-immunogenicity of HPV infection, by immunoregulatory processes in skin, and by subversion of immune response induction and immune effector functions by papillomavirus proteins. This review describes HPV-specific immune responses induced by viral proteins, their regulation by host and viral factors, and highlights some conclusions from our own recent research.

Immunosuppressive tumor microenvironment in cervical cancer patients

Cervical cancer is caused by Human papillomavirus (HPV) in virtually all cases. These HPV-induced cancers express the viral oncogenes E6 and E7 and are therefore potentially recognized by the immune system. Despite the abundant presence of these foreign antigens, the immune system is unable to cope with the tumor. Due to the constant immunological pressure, cervical cancers can evolve different immune evasion strategies, which will be described in the current review. Several approaches for immunotherapy of cervical cancer are currently under development, which aim at inducing strong HPV-specific immunity. Besides the reinforcement of potent anti-tumor immune responses, immunotherapy could also enhance HPV-specific T regulatory cells. Supplementary strategies that neutralize an immunosuppressive milieu may have great potential. These strategies are discussed as well.

Identification of key amino acid residues that determine the ability of high risk HPV16-E7 to dysregulate major histocompatibility complex class I expression

High risk human Papillomavirus (HPV) types are the major causative agents of cervical cancer. Reduced expression of major histocompatibility complex class I (MHC I) on HPV-infected cells might be responsible for insufficient T cell response and contribute to HPV-associated malignancy. The viral gene product required for subversion of MHC I synthesis is the E7 oncoprotein. Although it has been suggested that high and low risk HPVs diverge in their ability to dysregulate MHC I expression, it is not known what sequence determinants of HPV-E7 are responsible for this important functional difference. To investigate this, we analyzed the capability to affect MHC I of a set of chimeric E7 variants containing sequence elements from either high risk HPV16 or low risk HPV11. HPV16-E7, but not HPV11-E7, causes significant diminution of mRNA synthesis and surface presentation of MHC I, which depend on histone deacetylase activity. Our experiments demonstrate that the C-terminal region within the zinc finger domain of HPV-E7 is responsible for the contrasting effects of HPV11- and HPV16-E7 on MHC I. By using different loss- and gain-of-function mutants of HPV11- and HPV16-E7, we identify for the first time a residue variation at position 88 that is highly critical for HPV16-E7-mediated suppression of MHC I. Furthermore, our studies suggest that residues at position 78, 80, and 88 build a minimal functional unit within HPV16-E7 required for binding and histone deacetylase recruitment to the MHC I promoter. Taken together, our data provide new insights into how high risk HPV16-E7 dysregulates MHC I for immune evasion.

Human papillomavirus 16 E7 protein inhibits interferon-γ-mediated enhancement of keratinocyte antigen processing and T-cell lysis

Infection of epithelium with human papillomavirus (HPV) 16 is generally prolonged, suggesting an ineffective virus-specific immune response, and prolonged infection promotes anogenital cancer. To determine whether poor antigen presentation by HPV-infected keratinocytes (KCs) contributes to prolonged HPV infection, KCs and KCs expressing HPV 16 E7 protein (E7-KCs) were compared for susceptibility to T-cell-mediated lysis directed to ovalbumin (OVA) processed for presentation by the KCs. Interferon (IFN)-γ efficiently enhanced susceptibility to lysis of KCs presenting OVA, but not of E7-KCs similarly presenting OVA. E7-KCs also exhibited impaired IFN-γ-induced upregulation of transcription of major histocompatibility complex class I antigen processing and presentation-associated genes, and of membrane SIINFEKL-H-2K(b) complexes. Thus, expression of HPV 16 E7 protein in KCs may inhibit enhancement by IFN-γ of KC sensitivity to T-cell lysis, by impairing antigen presentation.

[Prophylactic and therapeutic vaccines against human papilloma virus]

Infection with human papilloma virus (HPV) has been identified as the cause of recurrent papillomatosis and of a subgroup of squamous cell carcinomas of the head and neck. A change in prevalence of these lesions, especially for oropharyngeal carcinoma, can be expected as a consequence of the introduction of prophylactic HPV vaccines for young women, targeting the most frequent high- and low-risk HPV subtypes. Vaccination for the major low-risk HPV types has proven to be highly effective against genital warts and activity against papillomatosis can be expected. The possibilities of prophylactic HPV vaccination as well as new developments and the rationale for therapeutic vaccines are discussed on the basis of the current literature.

RNA Interference of Human Papillomavirus Type 16 E7 Increases HLA Class I Antigen Expression in HaCaT-E7 Cells

Background:

High-risk human papillomaviruses (HPVs) are the major causative agents of cervical cancer. The E7 protein of high-risk HPV disturbs cell cycle control and down-regulates components of the antigen presentation pathway, suggesting an ideal target for development of the immunotherapy in HPV-positive cervical cancers. We previously reported that HPV16 E7 could down-regulate cell-surface HLA class I antigen accompanying decreased expression of transporter associated with antigen processing 1 (TAP-1). The purpose of this study was to determine whether knockdown of HPV16 E7 could up-regulate surface HLA class I antigen expression in HPV16 E7 expressing HaCaT cells (HaCaT-E7).

Methods:

An E7-specific small interfering RNA (siRNA) was transfected into the HaCaT-E7 cells, and the expression of HPV16 E7 was measured by real-time reverse transcriptase polymerase chain reaction and Western blot. With the use of flow cytometry analysis, the levels of cell surface HLA class I antigen and intracellular TAP-1 expression were detected.

Results:

It was found that transfection of HPV16 E7-siRNA reduced HPV16 E7 expression as measured on messenger RNA and protein levels. The flow cytometry analysis showed that, compared with mock transfection, a statistically significant increase of approximately 75% in surface HLA class I levels was observed in HaCaT-E7 cells at 72 hours after transfection of E7 siRNA. Moreover, he knockdown of E7 in HaCaT-E7 cells could result in an increase of intracellular TAP-1 expression, which is essential for the expression of HLA class I at cell surface.

Conclusions:

Our study showed that the knockdown of HPV16 E7 could increase cell surface HLA class I antigen expression in HaCaT-E7 cells. In addition, for HPV-positive human cervical cancer, our observations indicate that theHPV E7gene is a target of choice.

T cell-tumor interaction directs the development of immunotherapies in head and neck cancer

The competent immune system controls disease effectively due to induction, function, and regulation of effector lymphocytes. Immunosurveillance is exerted mostly by cytotoxic T-lymphocytes (CTLs) while specific immune suppression is associated with tumor malignancy and progression. In squamous cell carcinoma of the head and neck, the presence, activity, but also suppression of tumor-specific CTL have been demonstrated. Functional CTL may exert a selection pressure on the tumor cells that consecutively escape by a combination of molecular and cellular evasion mechanisms. Certain of these mechanisms target antitumor effector cells directly or indirectly by affecting cells that regulate CTL function. This results in the dysfunction or apoptosis of lymphocytes and dysregulated lymphocyte homeostasis. Another important tumor-escape mechanism is to avoid recognition by dysregulation of antigen processing and presentation. Thus, both induction of functional CTL and susceptibility of the tumor and its microenvironment to become T cell targets should be considered in CTL-based immunotherapy.

Recurrent respiratory papillomatosis: a complex defect in immune responsiveness to human papillomavirus-6 and -11

Recurrent respiratory papillomatosis (RRP) is a rare disease of the larynx caused by infection with human papillomaviruses (HPV) -6 or -11, associated with significant morbidity and on occasion mortality. Here we summarize our current understanding of the permissive adaptive and innate responses made by patients with RRP that support chronic HPV infection and prevent immune clearance of these viruses. Furthermore, we provide new evidence of T(H)2-like polarization in papillomas and blood of patients with RRP, restricted CD4 and CD8 Vbeta repertoires, the effect of HPV-11 early protein E6 on T-cell alloreactivity, enriched Langerhans cell presence in papillomas, and evidence that natural killer cells are dysfunctional in RRP. We review the immunogenetic mechanisms that regulate the dysfunctional responses made by patients with RRP in response to HPV infection of the upper airway. In addition, we are identifying T-cell epitopes on HPV-11 early proteins, in the context of human leukocyte antigen (HLA) class II alleles enriched in RRP that should help generate a therapeutic vaccine. Taken together, RRP is a complex, multigene disease manifesting as a tissue and HPV-specific, immune deficiency that prevents effective clearance and/or control of HPV-6 and -11 infection.

Evolution of human papillomavirus carcinogenicity

Members of the Alphapapillomavirus genus are the causative agent for virtually all cases of cervical cancer. However, strains (commonly referred to as types) within this genus span the entire range of pathogenicity from highly carcinogenic (e.g., HPV16, odds ratio = 281.9, responsible for 50% of all cervical cancers), moderately carcinogenic (e.g., HPV31) to not carcinogenic (e.g., HPV71). The persistent expression of the viral oncoproteins (E6 and E7) from HPV16 has been shown to be necessary and sufficient to transform primary human keratinocytes in vitro. A plethora of functions have been described for both oncoproteins, and through functional comparisons between HPV16 and HPV6, a subset of these functions have been suggested to be oncogenic. However, extrapolating functional differences from these comparisons is unlikely to tease apart the fine details. In this review, we argue that a thorough understanding of the molecular mechanisms differentiating oncogenic from nononcogenic types should be obtained by performing functional assays in an evolutionary and epidemiological framework. We continue by interpreting some recent results using this paradigm and end by suggesting directions for future inquiries.

The biological properties of E6 and E7 oncoproteins from human papillomaviruses

More than 100 different human papillomavirus (HPV) types have been isolated so far, and they can be sub-grouped in cutaneous or mucosal according to their ability to infect the skin or the mucosa of the genital or upper-respiratory tracts. A sub-group of human mucosal HPVs, referred to as high-risk HPV types, is responsible for approximately 5% of all human cancers, which represents one-third of all the tumours induced by viruses. Epidemiological and biological studies have shown that HPV16 is the most oncogenic type within the high-risk group. Emerging lines of evidence suggest that, in addition to the high-risk mucosal HPV types, certain cutaneous HPVs are involved in skin cancer. HPV-associated cancers are intimately linked to HPV persistence and the accumulation of chromosomal rearrangements. The products of the early genes, E6 and E7, of the high-risk mucosal HPV types play a key role in both events. Indeed, these proteins have developed a number of strategies to evade host immuno-surveillance allowing viral persistence, and to alter cell cycle and apoptosis control, facilitating the accumulation of DNA damage/mutations. Often, the two oncoproteins target the same cellular pathways with different mechanisms, showing a strong synergism in promoting cellular transformation and neutralizing the immune response. Here, we review most of the findings on the biological properties and molecular mechanisms of the oncoproteins E6 and E7 from mucosal and cutaneous HPV types.

[Laryngeal papillomatosis: etiology, diagnostics and therapy]

Papillomas are rare tumors that originate from the mucosa. They may appear in the nose, paranasal sinuses, oral cavity, larynx, trachea, or the skin. Papillomas are mainly asymptomatic and are therefore mostly diagnosed coincidentally. In contrast, laryngeal papillomatosis may cause stridor, dyspnoea, and hoarseness. A viral cause of the disease seems likely, especially human papilloma virus. Mechanical irritation is also a possible reason when the nose, oral cavity, or oropharynx is affected. All papillomas, independent of their origin, may recur, and have the possibility of malignant degeneration in common. The therapy of choice is complete surgical excision. Regarding laryngeal papillomatosis, laser vaporisation or excision using the CO(2)laser is recommended. Because retreatments using conventional modalities are frequently necessary, especially in the case of laryngeal papillomatosis, adjuvant therapies are applied with the aim of reducing the recurrence rate and prolonging the interval between treatments.

Recurrent Respiratory Papillomatosis: A Longitudinal Study Comparing Severity Associated With Human Papilloma Viral Types 6 and 11 and Other Risk Factors in a Large Pediatric Population

OBJECTIVES/HYPOTHESIS

A database was developed for prospective, longitudinal study of recurrent respiratory papillomatosis (RRP) in a large population of pediatric patients. Data recorded for each patient included epidemiological factors, human papilloma virus (HPV) type, clinical course, staged severity of disease at each surgical intervention, and frequency of surgical intervention. The study hypothesizes that patients with HPV type 11 (HPV-11) and patients younger than 3 years of age at diagnosis are at risk for more aggressive and extensive disease.

STUDY DESIGN

The 10-year prospective epidemiological study used disease staging for each patient with an original scoring system. Severity scores were updated at each surgical procedure.

METHODS

Parents of children with RRP referred to the authors' hospital completed a detailed epidemiological questionnaire at the initial visit or at the first return visit after the study began. At the first endoscopic debridement after study enrollment, tissue was obtained and submitted for HPV typing using polymerase chain reaction techniques and in situ hybridization. Staging of disease severity was performed in real time at each endoscopic procedure using an RRP scoring system developed by one of the authors (B.J.W.). The frequency of endoscopic operative debridement was recorded for each patient. Information in the database was analyzed to identify statistically significant relationships between extent of disease and/or HPV type, patient age at diagnosis, and selected epidemiological factors.

RESULTS

The study may represent the first longitudinal prospective analysis of a large pediatric RRP population. Fifty-eight of the 73 patients in the study underwent HPV typing. Patients infected with HPV-11 were significantly more likely to have higher severity scores, require more frequent surgical intervention, and require adjuvant therapy to control disease progression. In addition, patients with HPV-11 RRP were significantly more likely to develop tracheal disease, to require tracheotomy, and to develop pulmonary disease. Patients receiving a diagnosis of RRP before 3 years of age had significantly higher severity scores, higher frequencies of surgical intervention, and greater likelihood of requiring adjuvant medical therapy. Patients with Medicaid insurance had significantly higher severity scores and required more frequent surgical debridement. Birth by cesarean section appeared to be a significant risk factor for more severe disease and necessity of more frequent surgical intervention.

CONCLUSION

Statistical analysis of the relationships among epidemiological factors, HPV type, and clinical course revealed that patients with HPV-11 and patients younger than 3 years of age at RRP diagnosis are prone to develop more aggressive disease as represented by higher severity scores at endoscopic debridement, more frequent operative debridement procedures per year, a greater requirement for adjuvant therapy, and greater likelihood of tracheal disease with tracheotomy.

Human papillomavirus and molecular considerations for cancer risk

Human papillomaviruses (HPVs) are a major cause of cancer globally, including cervical cancer. The HPV 'early' proteins, E6 and E7, are the chief oncoproteins involved in cancer progression. These oncoproteins are more highly expressed in high-grade dysplasias and invasive cancer coincident with reduced viral DNA replication and reduced production of infective progeny virions. The E6 and E7 oncoproteins interact with several cellular proteins-classically TP53 and RB1, respectively-leading to the degradation of several of these proteins, although all interactions do not necessarily result in the degradation of a cellular protein. HPV infection is also associated with viral and host DNA methylation changes, many of which also occur in cancer types not associated with HPV infection. The E6 and E7 interactions with cellular proteins and DNA methylation changes are associated with changes in the integrity of key cellular pathways that regulate genomic integrity, cell adhesion, the immune response, apoptosis, and cell cycle control. The alterations in key cellular pathways may provide useful biomarkers to improve the sensitivity of current cancer screening methods, such as the Papanicolaou test. This review provides a detailed summary of the interactions of E6 and E7 with cellular proteins and alterations in cellular DNA methylation associated with HPV infection. The importance of molecular biomarkers to the clinical setting, underserved populations, and general public health is discussed.

Structural and Functional Dissection of the Human Cytomegalovirus Immune Evasion Protein US6

The human cytomegalovirus (HCMV) protein US6 inhibits the transporter associated with antigen processing (TAP). Since TAP transports antigenic peptides into the endoplasmic reticulum for binding to major histocompatibility class I molecules, inhibition of the transporter by HCMV US6 impairs the presentation of viral antigens to cytotoxic T lymphocytes. HCMV US6 inhibits ATP binding by TAP, hence depriving TAP of the energy source it requires for peptide translocation, yet the molecular basis for the interaction between US6 and TAP is poorly understood. In this study we demonstrate that residues 89 to 108 of the HCMV US6 luminal domain are required for TAP inhibition, whereas sequences that flank this region stabilize the binding of the viral protein to TAP. In parallel, we demonstrate that chimpanzee cytomegalovirus (CCMV) US6 binds, but does not inhibit, human TAP. The sequence of CCMV US6 differs from that of HCMV US6 in the region corresponding to residues 89 to 108 of the HCMV protein. The substitution of this region of CCMV US6 with the corresponding residues from HCMV US6 generates a chimeric protein that inhibits human TAP and provides further evidence for the pivotal role of residues 89 to 108 of HCMV US6 in the inhibition of TAP. On the basis of these observations, we propose that there is a hierarchy of interactions between HCMV US6 and TAP, in which residues 89 to 108 of HCMV US6 interact with and inhibit TAP, whereas other parts of the viral protein also bind to TAP and stabilize this inhibitory interaction.

The E5 protein of the human papillomavirus type 16 down-regulates HLA-I surface expression in calnexin-expressing but not in calnexin-deficient cells

The human papillomavirus type 16 E5 protein (HPV16 E5) down-regulates surface expression of HLA-I molecules. The molecular mechanisms underlying this effect are so far unknown. Here we show that HPV16 E5 down-regulates HLA-I surface expression in calnexin-containing but not in calnexin-deficient cells. Immunoprecipitation experiments reveal that calnexin and HPV16E5 can be co-precipitated and that this association depends on the presence of a wild-type first hydrophobic region of E5. When an E5 mutant (M1) in which the first putative transmembrane helix had been disrupted was used for the transfections calnexin-E5 co-precipitation was strongly impaired. In addition, we show that the M1 mutant is only able to marginally down-regulate HLA-I surface expression compared to the wild-type protein. Besides, we demonstrate that E5 forms a ternary complex with calnexin and the heavy chain of HLA-I, which is mediated by the first hydrophobic region of the E5 protein. On the basis of our results we conclude that formation of this complex is responsible for retention of HLA-I molecules in the ER of the cells.

Resolution of cervical dysplasia is associated with T-cell proliferative responses to human papillomavirus type 16 E2

The 'high-risk' human papillomaviruses (HPVs) cause persistent infections of the anogenital region that may resolve spontaneously following activation of a protective immune response. The aim of this study was to determine whether cell-mediated immunity (CMI) to the early protein E2 was associated with disease regression and to establish whether E2 CMI and antibodies to L1 virus-like particles (VLPs) were associated markers of immunity to HPV. Lymphoproliferative responses to histidine-tagged E2 and antibody responses to VLPs were measured in patients with persistent cervical dysplasia, those whose disease had recently resolved and normal controls. Resolvers had significantly higher E2-specific lymphoproliferative responses when compared with normal controls or persisters, whereas there was no significant difference between the persisters and the normal controls. The T cells stimulated by E2 secreted high levels of gamma interferon (IFN-gamma), consistent with a type 1 helper (Th1) phenotype. VLP IgG responses were associated with current or previous HPV infection, but not with disease regression or a lymphoproliferative response to E2. Major histocompatibility complex class I-restricted T cells secreted IFN-gamma following stimulation with E1, and E2 peptides were detected more frequently in the persister group. The data showed that lymphoproliferative responses to E2 with a cytokine profile indicative of Th1 are associated with disease resolution, supporting the development of a therapeutic vaccine that activates this type of response for the treatment of individuals with pre-existing disease.

Children and partners of patients with recurrent respiratory papillomatosis have no evidence of the disease during long-term observation

OBJECTIVE

Recurrent respiratory papillomatosis (RRP) is the most common benign neoplasm affecting the larynx and upper respiratory tract. The aim of our study was to investigate whether children and partners of patients with RRP develop the same disease and to determine whether there is an impact of pregnancy on the course of RRP.

PATIENTS AND METHODS

Thirty-eight of 42 patients with RRP were accepted for a multicenter prospective study in Germany in 21.06.83-12.03.90. Mean follow-up duration was 15.3+/-1.8 years. The data of partners of patients with RRP was collected during the period of observation and then updated via interviews in January 2006. Twenty-nine children and four grandchildren were born to 14 patients with RRP. Fifteen of 448 cases of patients with RRP were treated in Saint Vladimir Moscow Children's Hospital in Russia in 1988-2003 and analyzed retrospectively. Sixteen children and one grandchild were born to 15 patients with RRP from Russia. In both studies, the virus type of patients with RRP was identified by nested PCR or Southern blot hybridization. Statistical analysis was performed using Fisher's exact test (probability value set at p<0.05).

RESULTS

All children born to patients with RRP were healthy. RRP was not diagnosed in any of them on the basis of clinical or histological examination. Four of 45 children developed dysphonia, two of them had vocal cord nodules. None of the sexual partners of patients has developed RRP during the follow-up period. Pregnancy was accompanied by excessive growth of papillomas in all women (100%) with RRP associated with HPV type 11, and only in 16.7% of women with RRP associated with HPV type 6 (p=0.001).

CONCLUSIONS

Patients with RRP are able to have healthy children regardless of the stage of the disease. Partners of RRP patients do not develop RRP during an observation period of 15 years. Pregnancy has a negative impact on the course of RRP and local laryngeal status in patients; it is more significant in HPV type 11 associated cases as it is manifested by more rapid papillomas growth and more frequent recurrence.

Adenovirus subversion of immune surveillance, apoptotic and growth regulatory pathways: a model for tumorigenesis

The adenovirus system provides a novel model for evaluating the roles of multiple factors involved in tumour progression. In common with other DNA tumour viruses, adenovirus employs a variety of strategies to evade immune surveillance and perturbs cellular apoptotic and growth regulatory pathways to ensure efficient replication of progeny virions. Such subversion of cellular networks is also found in tumour cells. The mechanism behind the avoidance of immune surveillance and the extent of cellular network interference achieved by adenovirus is still being uncovered and is predicted to have ramifications for the design of cancer therapeutics.

Molecular mechanisms of HLA class I antigen abnormalities following viral infection and transformation

In humans as in other animal species, CD8+ cytotoxic T lymphocytes (CTLs) play an important if not the major role in controlling virus-infected and malignant cell growth. The interactions between CD8+ T cells and target cells are mediated by human leukocyte antigen (HLA) class I antigens loaded with viral and tumor antigen-derived peptides along with costimulatory receptor/ligand stimuli. Thus, to escape from CD8+ T-cell recognition and destruction, viruses and tumor cells have developed strategies to inhibit the expression and/or function of HLA class I antigens. In contrast, cells with downregulated MHC class I surface expression can be recognized by NK cells, although NK cell-mediated lysis could be abrogated by the expression of inhibiting NK cell receptors. This review discusses the molecular mechanisms utilized by viruses to inhibit the formation, transport and/or expression of HLA class I antigen/peptide complexes on the cell surface. The knowledge about viral interference with MHC class I antigen presentation is not only crucial to understand the pathogenesis of viral diseases, but contributes also to the design of novel strategies to counteract the escape mechanisms utilized by viruses. These investigations may eventually lead to the development of effective immunotherapies to control viral infections and virus-associated malignant diseases.

Heat shock proteins in autoimmune diseases

Heat shock proteins (hsp's) are among the most conserved proteins in evolution. They have been identified as important pathogen-related antigens as well as autoantigens suitable for construction of novel vaccines. The high evolutionary homology of hsp's has raised the question about the safety of such vaccines. Experimental and clinical observations have confirmed that hsp proteins are involved in the regulation of some autoimmune disease such as autoimmune arthritis, type 1 diabetes mellitus, atherosclerosis, multiple sclerosis, and other autoimmune reactions. It has been shown in experimental animals that some hsp proteins (especially hsp60, hsp70, and hsp10) can either induce or prevent autoimmune reactions depending on the circumstances. This article discusses the involvement of hsp proteins in the etiology of autoimmune diseases and it presents promising experimental data on the effects of immunization with hsp proteins in the prevention and therapy of autoimmune diseases.

Antitumor Activity of Human Papillomavirus Type 16 E7–Specific T Cells against Virally Infected Squamous Cell Carcinoma of the Head and Neck

Human papillomavirus (HPV)-associated squamous cell carcinoma of the head and neck (SCCHN) seems to be a suitable target for cancer vaccination. HPV-encoded oncogenic proteins, such as E7, are promising tumor-specific antigens and are obligatory for tumor growth. Because few immunologic studies have analyzed the endogenous HPV-specific immune response in this subset of SCCHN patients, we studied T-cell frequencies against HPV-16 E7(11-20) or E7(86-93) in tumor-bearing, human leukocyte antigen (HLA)-A*0201+ SCCHN patients, whose tumors were either HPV-16+ or HPV-16-. In HPV-16+ SCCHN patients, frequencies of T cells against either peptide were significantly elevated (P < 0.005) compared with HPV-16- patients or healthy volunteers. Tetramer+ T cells showed evidence of terminally differentiated phenotype (CD45RA+CCR7-) and an elevated level of CD107a staining for degranulation. Despite detectable expression of the restricting HLA class I allele, HLA-A*0201-E7(11-20)- or HLA-A*0201-E7(86-93)-specific CTL obtained by in vitro stimulation of healthy donor peripheral blood mononuclear cells only recognize a naturally HPV-16-transformed, HLA-A*0201+ SCCHN cell line after pretreatment with IFN-gamma. This cell line had little or no expression of LMP2, TAP1, and tapasin, critical components of the HLA class I antigen-processing machinery, which were up-regulated by IFN-gamma treatment. Immunohistochemistry of HPV-16+ SCCHN tumors showed that these antigen-processing machinery components are down-regulated in tumors in vivo compared with adjacent normal squamous epithelium. Thus, immunity to HPV-16 E7 is associated with the presence of HPV-16 infection and presentation of E7-derived peptides on SCCHN cells, which show evidence of immune escape. These findings support further development of E7-specific immunotherapy and strategies for up-regulation of antigen-processing machinery components in HPV-associated SCCHN.

Recurrent respiratory papillomatosis: pathogenesis to treatment

PURPOSE OF REVIEW

Recurrent respiratory papillomatosis remains a serious disease and is commonly treated by otolaryngologists. The goals of this review are to update physicians on current understandings regarding viral pathogenesis, patient risks, and current trends in treatment strategies.

RECENT FINDINGS

Surgical debulking still remains the foundation of treatment; however, newer surgical approaches utilizing microdebriders are replacing laser ablation. Genetic studies have identified individuals with specific immune cell alleles to be at greater risk for persistent infection. Our understanding of the viral pathogenesis has increased by the identification of a viral mechanism to downregulate antigen expression in cells infected with human papillomavirus, thus possibly allowing decreased immune detection. Although the viral types responsible for recurrent respiratory papillomatosis have been identified, the mechanism by which they alter cellular growth has not been identified. Research studies investigating adjuvant medical therapies aimed at reducing required surgical therapy intervals and possibly helping cure the infection are being completed. A safe, effective adjuvant therapy is still currently not available.

SUMMARY

Improved surgical approaches have slightly enhanced patient care; however, more research is needed to understand how human papillomavirus causes disease so that these therapies can be developed.

Failure of gamma interferon but not interleukin-10 expression in response to human papillomavirus type 11 E6 protein in respiratory papillomatosis

Recurrent respiratory papillomatosis (RRP) is a chronic, debilitating disease of the upper airway caused by human papillomavirus type 6 (HPV-6) or HPV-11. We describe responses of peripheral blood mononuclear cells (PBMC) and T cells from RRP patients and controls to the HPV-11 early proteins E6 and E7. PBMC were exposed in vitro to purified E6 or E7 proteins or transduced with fusion proteins containing the first 11 amino acids of the human immunodeficiency virus type 1 protein tat fused to E6 or E7 (tat-E6/tat-E7). T(H)1-like (interleukin-2 [IL-2], gamma interferon [IFN-gamma], IL-12, and IL-18), and T(H)2-like (IL-4 and IL-10) cytokine mRNAs were identified by reverse transcription-PCR, and IFN-gamma and IL-10 cytokine-producing cells were identified by enzyme-linked immunospot assay. These studies show that HPV-11 E6 skews IL-10-IFN-gamma expression by patients with RRP toward greater expression of IL-10 than of IFN-gamma. In addition, there is a general cytokine hyporesponsiveness to E6 that is more prominent for T(H)1-like cytokine expression by patients with severe disease. Patients showed persistent IL-10 cytokine expression by the nonadherent fraction of PBMC when challenged with E6 and tat-E6, and, in contrast to controls, both T cells and non-T cells from patients expressed IL-10. However, E7/tat-E7 cytokine responses in patients with RRP were similar to those of the controls. In contrast, E6 inhibited IL-2 and IL-18 mRNA expression that would further contribute to a cytokine microenvironment unfavorable to HPV-specific, T-cell responses that should control persistent HPV infection. In summary, E6 is the dominant inducer of cytokine expression in RRP, and it induces a skewed expression of IL-10 compared to the expression of IFN-gamma.

E5 protein of human papillomavirus type 16 selectively downregulates surface HLA class I

Papillomaviruses have evolved mechanisms that result in escape from host immune surveillance. The E5 protein is expressed early in papillomavirus infection in the deep layers of the infected epithelium. It is localized to the Golgi apparatus (GA) and endoplasmic reticulum. The E5 protein of bovine papillomavirus (BPV) impairs the synthesis and stability of major histocompatibility (MHC) class I complexes and prevents their transport to the cell surface due to retention in the GA. Here we show that human papillomavirus type 16 (HPV-16) E5 also causes the retention of MHC (HLA) class I complexes in the GA and impedes their transport to the cell surface, which is rescued by treatment with interferon. Unlike BPV E5, HPV-16 E5 does not affect the synthesis of HLA class I heavy chains or the expression of the transporter associated with antigen processing TAP. These results show that downregulation of surface MHC class I molecules is common to both BPV and HPV E5 proteins. Moreover, we determined that HPV-16 E5 downregulates surface expression of HLA-A and HLA-B, which present viral peptides to MHC class I-restricted cytotoxic T lymphocytes (CTLs), but not the natural killer (NK) cell inhibitory ligands HLA-C and HLA-E. Selective downregulation of cell surface HLA class I molecules may allow the virus to establish infection by avoiding immune clearance of virus-infected cells by both CTLs and NK cells.

Downregulation of major histocompatibility complex class I in bovine papillomas

Bovine papillomavirus (BPV) induces papillomas in cattle; in the great majority of cases, these regress due to the host immune response, but they can persist and progress to malignancy. Even in the absence of malignant transformation, BPV infection persists for a significant period of time before activation of the host immune system, suggesting that the host immune system is unaware of, or disabled by, BPV. E5 is the major oncoprotein of BPV, which, in addition to its transforming properties, downregulates the expression and transport to the cell surface of major histocompatibility complex class I (MHC I). Here, it is shown that co-expression of MHC I and E5 in papillomas caused by BPV-4 infection is mutually exclusive, in agreement with the inhibition of surface MHC I expression by E5 that is observed in vitro. The inhibition of MHC expression in E5-expressing papilloma cells could explain the long period that is required for activation of the immune response and has implications for the progression of papillomas to the malignant stage; absence of peptide presentation by MHC I to cytotoxic T lymphocytes would allow the infected cells to evade the host cellular immune response and allow the lesions to persist.

Long-term follow-up of patients treated with recombinant human interferon gamma for cervical intraepithelial neoplasia

OBJECTIVES

The immediate results of interferon gamma (IFN-gamma) treatment in the management of cervical intraepithelial neoplasia (CIN) have been described. However, little is known of the long-term results of this conservative treatment and we aimed to assess them.

METHODS

We conducted a 5-year follow-up of 13 women with either complete response to intracervical administration of 6,000,000 IU of IFN-gamma (remission from human papilloma virus-induced CIN occurred in nine cases) or partial response (a lower grade of CIN and/or HPV clearance was achieved in four cases).

RESULTS

We performed Papanicolaou smears and colposcopic examinations every 3 months for the first 2 years and every 6 months for the next 3 years. We found three cases of relapse of stage 1 CIN (CIN I), for a recurrence rate of 33.3%, and three cases of complete remission in four subjects with initial diagnosis of partial response. This allowed us to assess the overall lesion-free rate at 53% for the entire group of patients who had CIN I and CIN II treated with IFN-gamma.

CONCLUSIONS

Immunomodulation therapy with IFN-gamma has a high long-term efficacy; however, it is inferior to that of surgery.

Interplay between human papillomaviruses and dendritic cells

The design of the human papillomavirus (HPV) infection cycle is tightly fitted to the differentiation program of its natural host, the keratinocyte. This has important consequences for the role of antigen-presenting cells in the priming of antiviral immunity. The confinement of HPV infection to epithelia puts the epithelial dendritic cell, the Langerhans cell (LC), in charge of the induction of T cell-dependent immunity. Because HPV-infected keratinocytes cannot reach the regional lymphoid organs, and HPV-infection of LCs does not result in viral gene expression, priming of antiviral T cells exclusively depends on cross-presentation of viral antigens by the LC. Sensitization of the immune system in the regional lymphoid organs elicits systemic anti-HPV immunity as well as intraepithelial immune surveillance by memory-type intraepithelial T cells and locally produced antibodies. The high rate of spontaneous rejections of high-risk HPV-infections and HPV-positive premalignant lesions indicates that in general the LC-driven antigen presentation machinery is capable of raising an effective immune defense against HPV. Epidemiological studies also reveal that a decrease in the vigilance of the immune system is readily exploited by HPV to escape immune destruction, resulting in persistent infections and development of HPV-positive cancers. In view of the inherent antigenicity of HPV, immune intervention strategies constitute a promising approach for both the prevention and the therapeutic treatment of HPV-induced diseases. Importantly, the mechanisms that govern the induction and effector phases of the intraepithelial immune surveillance against HPV must be taken into account when designing such strategies.

The E5 protein of human papillomavirus type 16 perturbs MHC class II antigen maturation in human foreskin keratinocytes treated with interferon-gamma

Major histocompatibility complex (MHC) class II antigens are expressed on human foreskin keratinocytes (HFKs) following exposure to interferon gamma. The expression of MHC class II proteins on the cell surface may allow keratinocytes to function as antigen-presenting cells and induce a subsequent immune response to virus infection. Invariant chain (Ii) is a chaperone protein which plays an important role in the maturation of MHC class II molecules. The sequential degradation of Ii within acidic endocytic compartments is a key process required for the successful loading of antigenic peptide onto MHC class II molecules. Since human papillomavirus (HPV) 16 E5 can inhibit the acidification of late endosomes in HFKs, the E5 protein may be able to affect proper peptide loading onto the MHC class II molecule. To test this hypothesis, HFKs were infected with either control virus or a recombinant virus expressing HPV16 E5 and the infected cells were subsequently treated with interferon-gamma. ELISAs revealed a decrease of MHC class II expression on the surface of E5-expressing cells compared with control virus-infected cells after interferon treatment. Western blot analysis showed that, in cells treated with interferon gamma, E5 could prevent the breakdown of Ii and block the formation of peptide-loaded, SDS-stable mature MHC class II dimers, correlating with diminished surface MHC class II expression. These data suggest that HPV16 E5 may be able to decrease immune recognition of infected keratinocytes via disruption of MHC class II protein function.