Human papillomavirus-exposed Langerhans cells are activated by stabilized Poly-I:C

An exploration of the natural and acquired immunological mechanisms to high-risk human papillomavirus infection and unmasking immune escape in cervical cancer: A concise synopsis

The most common STD that triggers cervical cancer is the human papillomavirus. More than 20 types of human papillomavirus (HPV) can induce uterine cervical cancer. Almost all women acquire genital HPV infection soon after their first intercourse, with most of them clearing the virus within 3 years. An immune response is necessary to clear. The first responders to HPV infection are the innate immune system elements composed of macrophages, keratinocytes, natural killer cells, and natural killer T-lymphocytic (NKT) cells. Cytotoxic T lymphocytes (CTLs) comprise the second line of defense and kill HPV16-infected cells expressing various peptides derived from their transforming early viral oncoproteins, mainly E2•E6. Even though HPV can manage to trick away our immune systems, first of all, it is important to emphasize that HPV replication does not kill the host cells. It does not replicate viral antigens or cause inflammation. The HPV16 E6 and E7 genes suppress host cell type 1 interferons (IFNs), which are detectable after infection. The patient may have immunological tolerance; hence, there are no costimulatory signals from inflammatory cytokines like IFNs during antigen recognition. Evidence shows that HlA class I generations have been inhibited by HPV16 E5, which could protect this tumor cell from CTL attack. HPV16 E7 is responsible for initiating immunotolerance and increasing regulatory T cells (Treg) to repress immunological regression. Evasion from immune system protection plays a critical role in the outcome of persistent HPV infection and the development of cervical cancer. Vaccination against HPV16 and 18 during adolescence is the most effective method for preventing cervical cancer in women, considering the immunological processes involved.

Poly(I:C) Treatment Prevents Skin Tumor Formation in the Preclinical HPV8 Transgenic Mouse Model

Actinic keratoses and cutaneous squamous cell carcinomas are associated with infections with human papillomavirus of genus beta (betaHPV) in immunosuppressed patients. To date, targeted therapy against betaHPV-associated skin cancer does not exist because of the large number of betaHPV without defined high-risk types. In this study, we hypothesized that the activation of innate antiviral immunity in the skin, asymptomatically infected with betaHPV, induces an antitumor response by in situ autovaccination and prevents the formation of betaHPV-associated skin cancer. To test this, we used the preclinical keratin-14-HPV8 transgenic mouse model, which develops skin tumors after mechanical wounding. Remarkably, treatment with the antiviral immune response activating polyinosinic-polycytidylic acid (poly[I:C]) completely prevented cutaneous tumor growth. The induction of the IFN-induced genes Cxcl10 and Ifit1 by poly(I:C) depended on MDA5 activation. Increased numbers of total and activated CD4 and CD8 T cells were detected in poly(I:C)-treated skin. T cells were found in the skin of poly(I:C)-treated mice but not in the skin tumors of untreated mice. T-cell depletion showed a predominant role of CD4 T cells in poly(I:C)-mediated tumor prevention. Our findings identify the MDA5 ligand poly(I:C) as a promising candidate for in situ autovaccination approaches, which might serve as a treatment strategy against betaHPV-related skin diseases.

Immunotherapeutic Approaches for the Treatment of HPV-Associated (Pre-)Cancer of the Cervix, Vulva and Penis

Human papillomavirus (HPV) infection drives tumorigenesis in almost all cervical cancers and a fraction of vulvar and penile cancers. Due to increasing incidence and low vaccination rates, many will still have to face HPV-related morbidity and mortality in the upcoming years. Current treatment options (i.e., surgery and/or chemoradiation) for urogenital (pre-)malignancies can have profound psychosocial and psychosexual effects on patients. Moreover, in the setting of advanced disease, responses to current therapies remain poor and nondurable, highlighting the unmet need for novel therapies that prevent recurrent disease and improve clinical outcome. Immunotherapy can be a useful addition to the current therapeutic strategies in various settings of disease, offering relatively fewer adverse effects and potential improvement in survival. This review discusses immune evasion mechanisms accompanying HPV infection and HPV-related tumorigenesis and summarizes current immunotherapeutic approaches for the treatment of HPV-related (pre-)malignant lesions of the uterine cervix, vulva, and penis.

A model of impaired Langerhans cell maturation associated with HPV induced epithelial hyperplasia

Langerhans cells (LC) are skin-resident antigen-presenting cells that regulate immune responses to epithelial microorganisms. Human papillomavirus (HPV) infection can promote malignant epithelial transformation. As LCs are considered important for controlling HPV infection, we compared the transcriptome of murine LCs from skin transformed by K14E7 oncoprotein and from healthy skin. We identified transcriptome heterogeneity at the single cell level amongst LCs in normal skin, associated with ontogeny, cell cycle, and maturation. We identified a balanced co-existence of immune-stimulatory and immune-inhibitory LC cell states in normal skin that was significantly disturbed in HPV16 E7-transformed skin. Hyperplastic skin was depleted of immune-stimulatory LCs and enriched for LCs with an immune-inhibitory gene signature, and LC-keratinocyte crosstalk was dysregulated. We identified reduced expression of interleukin (IL)-34, a critical molecule for LC homeostasis. Enrichment of an immune-inhibitory LC gene signature and reduced levels of epithelial IL-34 were also found in human HPV-associated cervical epithelial cancers.

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Single cell atlas of Langerhans cells in cutaneous skin

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Stimulatory and inhibitory Langerhans cell states are in balance

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Inhibitory Langerhans cell states dominate HPV-transformed hyperplastic skin

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Langerhans cell imbalance is associated with disrupted IL-34 signaling

The Immune Microenvironment in Human Papilloma Virus-Induced Cervical Lesions-Evidence for Estrogen as an Immunomodulator

Globally, human papilloma virus (HPV) infection is a common sexually transmitted disease. However, most of the HPV infections eventually resolve aided by the body’s efficient cell-mediated immune responses. In the vast majority of the small group of patients who develop overt disease too, it is the immune response that culminates in regression of lesions. It is therefore a rarity that persistent infection by high-risk genotypes of HPV compounded by other risk factors progresses through precancer (various grades of cervical intraepithelial neoplasia—CIN) to cervical cancer (CxCa). Hence, although CxCa is a rare culmination of HPV infection, the latter is nevertheless causally linked to >90% of cancer. The three ‘Es’ of cancer immunoediting viz. elimination, equilibrium, and escape come into vogue during the gradual evolution of CIN 1 to CxCa. Both cell-intrinsic and extrinsic mechanisms operate to eliminate virally infected cells: cell-extrinsic players are anti-tumor/antiviral effectors like Th1 subset of CD4+ T cells, CD8+ cytotoxic T cells, Natural Killer cells, etc. and pro-tumorigenic/immunosuppressive cells like regulatory T cells (Tregs), Myeloid-Derived Suppressor Cells (MDSCs), type 2 macrophages, etc. And accordingly, when immunosuppressive cells overpower the effectors e.g., in high-grade lesions like CIN 2 or 3, the scale is tilted towards immune escape and the disease progresses to cancer. Estradiol has long been considered as a co-factor in cervical carcinogenesis. In addition to the gonads, the Peyer’s patches in the gut synthesize estradiol. Over and above local production of the hormone in the tissues, estradiol metabolism by the gut microbiome: estrobolome versus tryptophan non-metabolizing microbiome, regulates free estradiol levels in the intestine and extraintestinal mucosal sites. Elevated tissue levels of the hormone serve more than one purpose: besides a direct growth-promoting action on cervical epithelial cells, estradiol acting genomically via Estrogen Receptor-α also boosts the function of the stromal and infiltrating immunosuppressive cells viz. Tregs, MDSCs, and carcinoma-associated fibroblasts. Hence as a corollary, therapeutic repurposing of Selective Estrogen Receptor Disruptors or aromatase inhibitors could be useful for modulating immune function in cervical precancer/cancer. The immunomodulatory role of estradiol in HPV-mediated cervical lesions is reviewed.

Intratumoural immunotherapy: activation of nucleic acid sensing pattern recognition receptors

Recently, it has become clear that the tumour microenvironment (TME) is important in cancer immunotherapy. While immune checkpoint inhibitors are effective for some patients, the heterogeneous nature and status of the TME (‘cold’ tumours) play a critical role in suppressing antitumour immunity in non-responding patients. Converting ‘cold’ to ‘hot’ tumours through modulation of the TME may enable expansion of the therapeutic efficacy of immunotherapy to a broader patient population. This paper describes advances in intratumoural immunotherapy, specifically activation of nucleic acid sensing pattern recognition receptors to modulate the TME.

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Intratumoural immunotherapy to modulate the tumour microenvironment.

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Use of novel immunostimulatory agents which activate nucleic acid sensing pattern recognition receptors.

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Harnessing innate and adaptive immunity induced by receptor-mediated immune cascade.

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Intratumoural therapy leads to local and anenestic tumour responses.

CXCL14 suppresses human papillomavirus-associated head and neck cancer through antigen-specific CD8+ T-cell responses by upregulating MHC-I expression

Evasion of the host immune responses is critical for both persistent human papillomavirus (HPV) infection and associated cancer progression. We have previously shown that expression of the homeostatic chemokine CXCL14 is significantly downregulated by the HPV oncoprotein E7 during cancer progression. Restoration of CXCL14 expression in HPV-positive head and neck cancer (HNC) cells dramatically suppresses tumor growth and increases survival through an immune-dependent mechanism in mice. While CXCL14 recruits natural killer (NK) and T cells to the tumor microenvironment, the mechanism by which CXCL14 mediates tumor suppression through NK and/or T cells remained undefined. Here, we report that CD8⁺ T cells are required for CXCL14-mediated tumor suppression. Using a CD8⁺ T cell receptor transgenic model, we show that the CXCL14-mediated antitumor CD8⁺ T cell responses require antigen specificity. Interestingly, CXCL14 expression restores major histocompatibility complex class I (MHC-I) expression on HPV-positive HNC cells downregulated by HPV, and knockdown of MHC-I expression in HNC cells results in loss of tumor suppression even with CXCL14 expression. These results suggest that CXCL14 enacts antitumor immunity through restoration of MHC-I expression on tumor cells and promoting antigen-specific CD8⁺ T cell responses to suppress HPV-positive HNC.

Papillomavirus Immune Evasion Strategies Target the Infected Cell and the Local Immune System

Persistent infection with human papillomavirus (HPV) initiates ~5% of all human cancers, and particularly cervical and oropharyngeal cancers. HPV vaccines prevent HPV infection, but do not eliminate existing HPV infections. Papillomaviruses induce hyperproliferation of epithelial cells. In this review we discuss how hyperproliferation renders epithelial cells less sensitive to immune attack, and impacts upon the efficiency of the local immune system. These observations have significance for the design of therapeutic HPV cancer immunotherapies.

T cell ignorance is bliss: T cells are not tolerized by Langerhans cells presenting human papillomavirus antigens in the absence of costimulation

Human papillomavirus type 16 (HPV16) infections are intra-epithelial, and thus, HPV16 is known to interact with Langerhans cells (LCs), the resident epithelial antigen-presenting cells (APCs). The current paradigm for APC-mediated induction of T cell anergy is through delivery of T cell receptor signals via peptides on MHC molecules (signal 1), but without costimulation (signal 2). We previously demonstrated that LCs exposed to HPV16 in vitro present HPV antigens to T cells without costimulation, but it remained uncertain if such T cells would remain ignorant, become anergic, or in the case of CD4+ T cells, differentiate into Tregs. Here we demonstrate that Tregs were not induced by LCs presenting only signal 1, and through a series of in vitro immunizations show that CD8⁺ T cells receiving signal 1+2 from LCs weeks after consistently receiving signal 1 are capable of robust effector functions. Importantly, this indicates that T cells are not tolerized but instead remain ignorant to HPV, and are activated given the proper signals.

The Interaction Between Human Papillomaviruses and the Stromal Microenvironment

Human papillomaviruses (HPVs) are small, double-stranded DNA viruses that replicate in stratified squamous epithelia and cause a variety of malignancies. Current efforts in HPV biology are focused on understanding the virus-host interactions that enable HPV to persist for years or decades in the tissue. The importance of interactions between tumor cells and the stromal microenvironment has become increasingly apparent in recent years, but how stromal interactions impact the normal, benign life cycle of HPVs, or progression of lesions to cancer is less understood. Furthermore, how productively replicating HPV impacts cells in the stromal environment is also unclear. Here we bring together some of the relevant literature on keratinocyte-stromal interactions and their impacts on HPV biology, focusing on stromal fibroblasts, immune cells, and endothelial cells. We discuss how HPV oncogenes in infected cells manipulate other cells in their environment, and, conversely, how neighboring cells may impact the efficiency or course of HPV infection.

Current therapeutic vaccination and immunotherapy strategies for HPV-related diseases

Carcinomas of the anogenital tract, in particular cervical cancer, remains one of the most common cancers in women, and represent the most frequent gynecological malignancies and the fourth leading cause of cancer death in women worldwide. Human papillomavirus (HPV)-induced lesions are immunologically distinct in that they express viral antigens, which are necessary to maintain the cancerous phenotype. The causal relationship between HPV infection and anogenital cancer has prompted substantial interest in the development of therapeutic vaccines against high-risk HPV types targeting the viral oncoproteins E6 and E7. This review will focus on the most recent clinical trials for immunotherapies for mucosal HPV-induced lesions as well as emerging therapeutic strategies that have been tested in pre-clinical models for HPV-induced diseases. Progress in peptide- and protein-based vaccines, DNA-based vaccines, viral/bacterial vector-based vaccines, immune checkpoint inhibition, immune response modifiers, and adoptive cell therapy for HPV will be discussed.

Immunostimulatory Activity of the Cytokine-Based Biologic, IRX-2, on Human Papillomavirus-Exposed Langerhans Cells

Langerhans cells (LCs) are the antigen-presenting cells of the epithelial layer and are responsible for initiating immune responses against skin and mucosa-invading viruses. Human papillomavirus (HPV)-mediated suppression of LC function is a crucial mechanism of HPV immune evasion, which can lead to persistent infection and development of several human cancers, including cervical, anal, and head and neck cancers. The cell-derived cytokine-based biologic, IRX-2, consists of multiple well-defined cytokines and is broadly active on various immune cell subsets. In this study, we investigated primary human LC activation after exposure to HPV16, followed by treatment with IRX-2 in vitro, and evaluated their subsequent ability to induce HPV16-specific T cells. In contrast to its activity on dendritic cells, HPV16 alone is not sufficient to induce phenotypic and functional activation of LCs. However, IRX-2 induces a significant upregulation of antigen presentation and costimulatory molecules, T helper 1 (Th1)-associated cytokine release, and chemokine-directed migration of LCs pre-exposed to HPV16. Furthermore, LCs treated with IRX-2 after HPV16 exposure induced CD8⁺ T-cell responses against specific HLA-A*0201-binding HPV16 T-cell epitopes. The present study suggests that IRX-2 is an attractive immunomodulator for assisting the immune response in eradication of HPV-infected cells, thereby potentially preventing HPV-induced cancers.

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.