The biology of beta human papillomaviruses

Synergistic Effect of Human Papillomavirus and Environmental Factors on Skin Squamous Cell Carcinoma, Basal Cell Carcinoma, and Melanoma: Insights from a Taiwanese Cohort

Human papillomavirus (HPV) has been implicated in various cancers, including those affecting the skin. The study assessed the long-term risk of skin cancer associated with HPV infection in Taiwan region, using data from the National Health Insurance Research Database between 2007 and 2015. Our analysis revealed a significant increase in skin cancer risk among those with HPV, particularly for squamous cell carcinoma (SCC), the subtype with the highest observed adjusted hazard ratio (aHR) = 5.97, 95% CI: 4.96-7.19). The overall aHR for HPV-related skin cancer was 5.22 (95% CI: 4.70-5.80), indicating a notably higher risk in the HPV-positive group. The risk of skin cancer was further stratified by type, with basal cell carcinoma (aHR = 4.88, 95% CI: 4.14-5.74), and melanoma (aHR = 4.36, 95% CI: 2.76-6.89) also showing significant associations with HPV. The study also highlighted regional variations, with increased risks in southern Taiwan and the Kaohsiung-Pingtung area. Key findings emphasize the importance of sun protection, particularly in regions of high UV exposure and among individuals in high-risk occupations. This research contributes to a better understanding of the complex interactions between HPV and skin cancer risk, reinforcing the importance of preventive strategies in public health.

The significance of stem cell-like memory T cells in viral and bacterial vaccines: A mini review

Vaccination has become a widely used method to induce immune protection against microbial pathogens, including viral and bacterial microorganisms. Both humoral and cellular immunity serve a critical role in neutralizing and eliminating these pathogens. An effective vaccine should be able to induce a long-lasting immune memory response. Recent investigations on different subsets of T cells have identified a new subset of T cells using multi-parameter flow cytometry, which possess stem cell-like properties and the ability to mount a rapid immune response upon re-exposure to antigens known as stem cell-like memory T cells (TSCM). One of the major challenges with current vaccines is their limited ability to maintain long-term memory in the adaptive immune system. Recent evidence suggests that a specific subgroup of memory T cells has the unique ability to retain their longevity for up to 25 years, as observed in the case of the yellow fever vaccine. Therefore, in this study, we tried to explore and discuss the potential role of this new T cell memory subset in the development of viral and bacterial vaccines.

T Cell Immunity in Human Papillomavirus-Related Cutaneous Squamous Cell Carcinoma-A Systematic Review

Cutaneous squamous cell carcinoma (cSCC) is an invasive malignancy that disproportionately afflicts immunosuppressed individuals. The close associations of cSCC with immunosuppression and human papillomavirus (HPV) infection beget the question of how these three entities are intertwined in carcinogenesis. By exploring the role of T cell immunity in HPV-related cSCC based on the existing literature, we found that the loss of T cell immunity in the background of β-HPV infection promotes cSCC initiation following exposure to environmental carcinogens or chronic trauma. This highlights the potential of developing T-cell centred therapeutic and preventive strategies for populations with increased cSCC risk.

Betapapillomavirus natural history and co-detection with alphapapillomavirus in cervical samples of adult women

Human papillomaviruses (HPV) of the genus Betapapillomavirus can infect both cutaneous and mucosal sites, but research on their natural history at mucosal sites remains scarce. We examined the risk factors and co-detection patterns of HPVs of the Betapapillomavirus and Alphapapillomavirus genera in cervical samples of the Ludwig-McGill cohort study. We assessed a subset of 505 women from the Ludwig-McGill cohort study from São Paulo, Brazil. Cervical samples over the first year of follow-up were tested for DNA of over 40 alphapapillomavirus types and 43 betapapillomavirus types using a type-specific multiplex genotyping polymerase chain reaction assay. We assessed the risk factors for prevalent and incident betapapillomavirus type detection, and whether types were detected more frequently together than expected assuming independence using permutation tests, logistic regression, and Cox regression. We observed significant within-genus clustering but not cross-genus clustering. Multiple betapapillomavirus types were co-detected in the same sample 2.24 (95% confidence interval [CI]: 1.65-3.29) times more frequently than expected. Conversely, co-detections of alphapapillomavirus and betapapillomavirus types in the same sample occurred only 0.64 (95% CI: 0.51-0.83) times as often as expected under independence. In prospective analyses, positivity to one HPV genus was associated with a nonsignificant lower incidence of detection of types in the other genus. Lifetime number of sex partners and new sex partner acquisition were associated with lower risks of prevalent and incident betapapillomavirus detection. Betapapillomaviruses are commonly found in the cervicovaginal tract. Results suggest potentially different mechanisms of transmission for betapapillomavirus genital infections other than vaginal sex.

Microbiota in cancer: molecular mechanisms and therapeutic interventions

The diverse bacterial populations within the symbiotic microbiota play a pivotal role in both health and disease. Microbiota modulates critical aspects of tumor biology including cell proliferation, invasion, and metastasis. This regulation occurs through mechanisms like enhancing genomic damage, hindering gene repair, activating aberrant cell signaling pathways, influencing tumor cell metabolism, promoting revascularization, and remodeling the tumor immune microenvironment. These microbiota-mediated effects significantly impact overall survival and the recurrence of tumors after surgery by affecting the efficacy of chemoradiotherapy. Moreover, leveraging the microbiota for the development of biovectors, probiotics, prebiotics, and synbiotics, in addition to utilizing antibiotics, dietary adjustments, defensins, oncolytic virotherapy, and fecal microbiota transplantation, offers promising alternatives for cancer treatment. Nonetheless, due to the extensive and diverse nature of the microbiota, along with tumor heterogeneity, the molecular mechanisms underlying the role of microbiota in cancer remain a subject of intense debate. In this context, we refocus on various cancers, delving into the molecular signaling pathways associated with the microbiota and its derivatives, the reshaping of the tumor microenvironmental matrix, and the impact on tolerance to tumor treatments such as chemotherapy and radiotherapy. This exploration aims to shed light on novel perspectives and potential applications in the field.

Ubiquitin-protein ligase E3A (UBE3A) mediation of viral infection and human diseases

The Ubiquitin-protein ligase E3A, UBE3A, also known as E6-associated protein (E6-AP), is known to play an essential role in regulating the degradation of various proteins by transferring Ub from E2 Ub conjugating enzymes to the substrate proteins. Several studies indicate that UBE3A regulates the stabilities of key viral proteins in the virus-infected cells and, thereby, the infected virus-mediated diseases, even if it were reported that UBE3A participates in non-viral-related human diseases. Furthermore, mutations such as deletions and duplications in the maternally inherited gene in the brain cause human neurodevelopmental disorders such as Angelman syndrome (AS) and autism. It is also known that UBE3A functions as a transcriptional coactivator for the expression of steroid hormone receptors. These reports establish that UBE3A is distinguished by its multitudinous functions that are paramount to viral pathology and human diseases. This review is focused on molecular mechanisms for such intensive participation of UBE3A in disease formation and virus regulation.

Characterization and comparative analysis of phosphorylation patterns in HPV18 and HPV11 E1 helicases: Implications for viral genome replication

The genome of human papillomaviruses (HPVs) encodes the E1 replication factor, whose biological activities are regulated by cellular protein kinases. Here, the phosphorylation pattern of the E1 helicase of oncogenic mucosotropic HPV18 was investigated both in vitro and in vivo. Four serine residues located in a short peptide within a localization regulatory region were found to be phosphorylated in both experimental settings. We demonstrate that this peptide is targeted in vitro by various protein kinases, including CK2, PKA, and CKD2/cyclin A/B/E complexes. Through point mutagenesis, we show that phosphorylation of this region is essential for E1 subcellular localization, the interaction of E1 with the E2 protein, and replication of the HPV18 genome. Furthermore, we demonstrate the functional conservation of this phosphorylation across the E1 proteins of the low-risk mucosotropic HPV11 and high-risk cutaneotropic HPV5. These findings provide deeper insights into the phosphorylation-mediated regulation of biological activities of the E1 protein.

Betapapillomaviruses in p16-Negative Vulvar Intraepithelial Lesions Associated with Squamous Cell Carcinoma

Approximately 40% of vulvar squamous cell carcinoma (vSCC) cases are etiologically associated with high-risk human papillomaviruses (HPVs) of the alpha genera (α-HPV) that cause other anogenital cancers; however, the etiology of α-HPV-negative vSCC is poorly understood. HPVs of the beta genera (β-HPV) are risk factors for cutaneous squamous cell carcinoma (cSCC) and may be related to carcinomas originating in other cutaneous sites such as the vulva. In this study, we investigate the presence of β-HPVs, with an emphasis on p16-negative squamous lesions adjacent to vSCC. We subjected 28 vulvar squamous intraepithelial lesions adjacent to vSCC for comprehensive HPV genotyping, p16 and p53 immunohistochemistry, and consensus morphology review. Selected cases were subjected to qPCR and RNA in situ hybridization. Clinical data were obtained from medical records. β-HPV DNA was detected in eight of ten p16-negative lesions and three of fourteen p16-positive high-grade squamous intraepithelial lesions. The HPV DNA loads in vulvar squamous intraepithelial lesions ranged between less than 1 HPV DNA copy per cell to more than 100 HPV DNA copies per cell. This is, to the best of our knowledge, the first report of the association of p16-negative vulvar intraepithelial squamous lesions with detection of β-HPVs. These findings expand possible etiologic mechanisms that may contribute to p16-negative lesions of the vulva.

Human papillomavirus spectrum of HPV-infected women in Nigeria: an analysis by next-generation sequencing and type-specific PCR

BACKGROUND

Human papillomavirus (HPV) infection and cervical cancer are leading health problems and causes of death in many parts of the world. There are ~ 200 HPV types that can infect humans. This study aims to understand the spectrum of HPV infections in Nigerian women with normal or abnormal cytology.

METHODS

We screened cervical samples from 90 women with possible HPV infections collected in two regional hospitals in Nigeria. The first screening was done using next-generation DNA sequencing (NGS), identifying multiple HPV types in many samples. Thereafter, type-specific PCR analysis was used to verify the NGS-identified HPV types in each sample.

RESULTS

NGS analysis of the 90 samples from the Nigerian cohort identified 44 HPV types. The type-specific PCR confirmed 25 HPV types out of the 44 HPV types detected by NGS, and ~ 10 of these types were the most prevalent. The top five prevalent types found in the Nigerian cohort were HPV71 (17%), HPV82 (15%), HPV16 (16%), HPV6 (10%), and HPV20 (7%). Among the PCR-confirmed HPV types, we found 40.98% high-risk HPV types, 27.22% low-risk HPV types, and 31.15% undetermined HPV types. Among these 25 HPV types in Nigeria, only six were included in the current nine-valent HPV vaccine. We also observed strikingly high multiple HPV infections in most patients, with as many as nine HPV types in a few single samples.

CONCLUSIONS

Our NGS-PCR approach of HPV typing in the Nigerian cohort samples unveiled all possible HPV types currently circulating in Nigerian people. We confirmed 25 HPV types using NGS and PCR, with many samples infected with multiple HPV types. However, only six of these types are part of the nine-valent HPV vaccines indicating the need to develop region-specific selective vaccines.

Phosphorylation of E2 Serine Residue 402 Is Required for the Transcription and Replication of the HPV5 Genome

Cutaneous human papillomavirus type 5 (HPV5) belongs to the supposedly oncogenic β-HPVs associated with specific types of skin and oral cavity cancers. Three viral proteins, namely, helicase E1 and transcription factors E2 and E8^E2, are master regulators of the viral life cycle. HPV5 E2 is a transcriptional activator that also participates in the E1-dependent replication and nuclear retention of the viral genome, whereas E8^E2 counterbalances the activity of E2 and inhibits HPV transcription and replication. In the present study, we demonstrate that the HPV5 E2 protein is extensively phosphorylated by cellular protein kinases, and serine residue 402 (S402) is the highest scoring phosphoacceptor site. This residue is located within a motif conserved among many β-HPVs and in the oncogenic HPV31 α-type. Using the nonphosphorylatable and phosphomimetic mutants, we demonstrate that phosphorylation of the E2 S402 residue is required for the transcription and replication of the HPV5 genome in U2OS cells and human primary keratinocytes. Mechanistically, the E2-S402-phopshodeficient protein is unable to trigger viral gene transcription and has an impaired ability to support E1-dependent replication, but the respective E8^E2-S213 mutant displays no phenotype. However, phosphorylation of the E2 S402 residue has no impact on the E2 stability, subcellular localization, self-assembly, DNA-binding capacity, and affinity to the E1 and BRD4 proteins. Further studies are needed to identify the protein kinase(s) responsible for this phosphorylation. IMPORTANCE Human papillomavirus type 5 (HPV5) may play a role in the development of specific types of cutaneous and head and neck cancers. The persistence of the HPV genome in host cells depends on the activity of its proteins, namely, a helicase E1 and transcription/replication factor E2. The latter also facilitates the attachment of episomal viral genomes to host cell chromosomes. In the present study, we show that the HPV5 E2 protein is extensively phosphorylated by host cell protein kinases, and we identify serine residue 402 as the highest scoring phosphoacceptor site of E2. We demonstrate that the replication of the HPV5 genome may be blocked by a single point mutation that prevents phosphorylation of this serine residue and switches off the transcriptional activity of the E2 protein. The present study contributes to a better understanding of β-HPV5 replication and its regulation by host cell protein kinases.

Recent advances in cutaneous HPV infection

More than 200 types of human papillomavirus (HPV) have been reported to date and have been associated with various dermatological diseases. Among dermatological diseases, viral verrucae are the most commonly reported to be associated with HPV. Epidermodysplasia verruciformis (EV) consists of three types: typical EV is an autosomal recessive genetic disorder with TMC6/TMC8 gene mutations, atypical EV develops due to various gene mutations that cause immunodeficiency, and acquired EV develops due to acquired immunodeficiency. Generalized verrucosis differs from EV in that it involves numerous verrucous nodules (mainly on the limbs), histopathologically no blue cells as seen in EV, and infection with cutaneous α-HPVs as well as β-HPVs. HPV-induced skin malignancies include squamous cell carcinoma (SCC) caused by β-HPV (especially HPV types 5 and 8) in EV patients, organ transplant recipients, and healthy individuals, and SCC of the vulva and nail unit caused by mucosal high-risk HPV infection. Carcinogenesis of β-HPV is associated with sunlight. Mucosal high-risk HPV-associated carcinomas may also be sexually transmitted. We focused on Bowen's disease of the nail, which has been the subject of our research for a long time and has recently come to the fore in the field of dermatology.

Tracking HPV Infection, Associated Cancer Development, and Recent Treatment Efforts-A Comprehensive Review

Human papillomaviruses (HPVs) are high-risk causative factors for HPV infection. This infection does not come alone; it is often seen with co-infection with other viruses and acts as a causative agent for several malignancies. The major purpose of this comprehensive study was to highlight some recent advances in biotechnology associated with HPV infection, including understanding its host interactions and cancerous progression. A systematic research strategy was used to gather data from recent, and the most advanced published electronic sources. The compiled data explain the recent understanding of biology, host-viral interaction cycles, co-infection with other viral diseases, and cellular transformation toward malignancies associated with HPV. In recent years, some vaccination protocols have been introduced in the form of live attenuated, subunit, and DNA-based vaccines. Moreover, some strategies of nanotechnology are being employed to synthesize drugs and vaccines with a whole new approach of plant-based products. The data are immense for the proposed research question, yet the need is to implement modern follow-up screening and modern therapeutics at the clinical level and to conduct wide-scale public awareness to lessen the HPV-related disease burden.

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.

Enhanced Spontaneous Skin Tumorigenesis and Aberrant Inflammatory Response to UVB Exposure in Immunosuppressed Human Papillomavirus Type 8‒Transgenic Mice

Human papillomaviruses (HPVs) from the beta genus are commensal viruses of the skin usually associated with asymptomatic infection in the general population. However, in individuals with specific genetic backgrounds, such as patients with epidermodysplasia verruciformis, or those with immune defects, such as organ transplant recipients, they are functionally involved in sunlight-induced skin cancer development, mainly keratinocyte carcinoma. Despite their well-established protumorigenic role, the cooperation between β-HPV infection, impaired host immunosurveillance, and UVB exposure has never been formally shown in animal models. In this study, by crossing skin-specific HPV8-transgenic mice with Rag2-deficient mice, we have generated a preclinical mouse model, named Rag2^‒/‒:K14-HPV8. These mice display an unhealthy skin phenotype and spontaneously develop papilloma-like lesions spreading to the entire skin much more rapidly compared with Rag2^+/+:K14-HPV8 mice. Exposure to low doses of UVB radiation is sufficient to trigger severe skin inflammation in Rag2^‒/‒:K14-HPV8 but not in Rag2^+/+:K14-HPV8 mice. Their inflamed skin very much resembled that observed in cutaneous field cancerization in organ transplant recipients, showing high levels of UVB-damaged cells, enhanced production of proinflammatory cytokines, and mast cell recruitment to the dermis. Overall, this immunocompromised HPV8-transgenic mouse model shows that the coexistence of immune defects, β-HPV, and UVB exposure promotes skin cancer development.

Beta Human Papillomavirus 8 E6 Induces Micronucleus Formation and Promotes Chromothripsis

Cutaneous beta genus human papillomaviruses (β-HPVs) are suspected to promote the development of nonmelanoma skin cancer (NMSC) by destabilizing the host genome. Multiple studies have established the genome destabilizing capacities of β-HPV proteins E6 and E7 as a cofactor with UV. However, the E6 protein from β-HPV8 (HPV8 E6) induces tumors in mice without UV exposure. Here, we examined a UV-independent mechanism of HPV8 E6-induced genome destabilization. We showed that HPV8 E6 reduced the abundance of anaphase bridge resolving helicase, Bloom syndrome protein (BLM). The diminished BLM was associated with increased segregation errors and micronuclei. These HPV8 E6-induced micronuclei had disordered micronuclear envelopes but retained replication and transcription competence. HPV8 E6 decreased antiproliferative responses to micronuclei and time-lapse imaging revealed HPV8 E6 promoted cells with micronuclei to complete mitosis. Finally, whole-genome sequencing revealed that HPV8 E6 induced chromothripsis in nine chromosomes. These data provide insight into mechanisms by which HPV8 E6 induces genome instability independent of UV exposure. IMPORTANCE Some beta genus human papillomaviruses (β-HPVs) may promote skin carcinogenesis by inducing mutations in the host genome. Supporting this, the E6 protein from β-HPV8 (8 E6) promotes skin cancer in mice with or without UV exposure. Many mechanisms by which 8 E6 increases mutations caused by UV have been elucidated, but less is known about how 8 E6 induces mutations without UV. We address that knowledge gap by showing that 8 E6 causes mutations stemming from mitotic errors. Specifically, 8 E6 reduces the abundance of BLM, a helicase that resolves and prevents anaphase bridges. This hinders anaphase bridge resolution and increases their frequency. 8 E6 makes the micronuclei that can result from anaphase bridges more common. These micronuclei often have disrupted envelopes yet retain localization of nuclear-trafficked proteins. 8 E6 promotes the growth of cells with micronuclei and causes chromothripsis, a mutagenic process where hundreds to thousands of mutations occur in a chromosome.

Vaccination with human alphapapillomavirus-derived L2 multimer protects against human betapapillomavirus challenge, including in epidermodysplasia verruciformis model mice

Human alphapapillomaviruses (αHPV) infect genital mucosa, and a high-risk subset is a necessary cause of cervical cancer. Licensed L1 virus-like particle (VLP) vaccines offer immunity against the nine most common αHPV associated with cervical cancer and genital warts. However, vaccination with an αHPV L2-based multimer vaccine, α11-88x5, protected mice and rabbits from vaginal and skin challenge with diverse αHPV types. While generally clinically inapparent, human betapapillomaviruses (βHPV) are possibly associated with cutaneous squamous cell carcinoma (CSCC) in epidermodysplasia verruciformis (EV) and immunocompromised patients. Here we show that α11-88x5 vaccination protected wild type and EV model mice against HPV5 challenge. Passive transfer of antiserum conferred protection independently of Fc receptors (FcR) or Gr-1+ phagocytes. Antisera demonstrated robust antibody titers against ten βHPV by L1/L2 VLP ELISA and neutralized and protected against challenge by 3 additional βHPV (HPV49/76/96). Thus, unlike the licensed vaccines, α11-88x5 vaccination elicits broad immunity against αHPV and βHPV.

Human Beta Papillomavirus Type 8 E1 and E2 Proteins Suppress the Activation of the RIG-I-like Receptor MDA5

Persistent infections of the skin with the human papillomavirus of genus beta (β-HPV) in immunocompetent individuals are asymptomatic, but in immunosuppressed patients, β-HPV infections exhibit much higher viral loads on the skin and are associated with an increased risk of skin cancer. Unlike with HPV16, a high-risk α-HPV, the impact of β-HPV early genes on the innate immune sensing of viral nucleic acids has not been studied. Here, we used primary skin keratinocytes and U2OS cells expressing HPV8 or distinct HPV8 early genes and well-defined ligands of the nucleic-acid-sensing receptors RIG-I, MDA5, TLR3, and STING to analyze a potential functional interaction. We found that primary skin keratinocytes and U2OS cells expressed RIG-I, MDA5, TLR3, and STING, but not TLR7, TLR8, or TLR9. While HPV16-E6 downregulated the expression of RIG-I, MDA5, TLR3, and STING and, in conjunction with HPV16-E7, effectively suppressed type I IFN in response to MDA5 activation, the presence of HPV8 early genes showed little effect on the expression of these immune receptors, except for HPV8-E2, which was associated with an elevated expression of TLR3. Nevertheless, whole HPV8 genome expression, as well as the selective expression of HPV8-E1 or HPV8-E2, was found to suppress MDA5-induced type I IFN and the proinflammatory cytokine IL-6. Furthermore, RNA isolated from HPV8-E2 expressing primary human keratinocytes, but not control cells, stimulated a type I IFN response in peripheral blood mononuclear cells, indicating that the expression of HPV8-E2 in keratinocytes leads to the formation of stimulatory RNA ligands that require the active suppression of immune recognition. These results identify HPV8-E1 and HPV8-E2 as viral proteins that are responsible for the immune escape of β-HPV from the innate recognition of viral nucleic acids, a mechanism that may be necessary for establishing persistent β-HPV infections.

The E6 and E7 proteins of beta3 human papillomavirus 49 can deregulate both cellular and extracellular vesicles-carried microRNAs

BACKGROUND

The β3 human papillomavirus (HPV)49 induces immortalization of primary keratinocytes through the action of E6 and E7 oncoproteins with an efficiency similar to alpha high risk (HR)-HPV16. Since HR-HPV oncoproteins are known to alter microRNA (miRNA) expression and extracellular vesicle (EV) production, we investigated the impact of HPV49 E6 and E7 proteins on miRNA profile and EV expression, and their involvement in the control of cell proliferation.

METHODS

The miRNA expression was evaluated by a miRNA array and validated by RT-qPCR in primary human keratinocytes immortalized by β3 HPV49 (K49) or α9 HR-HPV16 (K16), and in EVs from K49 and K16. The modulation of miRNA target proteins was investigated by immunoblotting analyses.

RESULTS

By comparing miRNA expression in K49 and K16 and the derived EVs, six miRNAs involved in HPV tumorigenesis were selected and validated. MiR-19a and -99a were found to be upregulated and miR-34a downregulated in both cell lines; miR-17 and -590-5p were upregulated in K49 and downmodulated in K16; miR-21 was downregulated only in K16. As for EV-carried miRNAs, the expression of miR-17, -19a, -21 and -99a was decreased and miR-34a was increased in K49 EVs. In K16 EVs, we revealed the same modulation of miR-19a, -34a, and -99a observed in producing cells, while miR-21 was upregulated. Cyclin D1, a common target of the selected miRNAs, was downmodulated in both cell lines, whereas cyclin-dependent kinase 4 was down-modulated in K49 but upregulated in K16.

CONCLUSION

These data suggest that E6 and E7 proteins of β3 HPV49 and α9 HR-HPV16 affect key factors of cell cycle control by indirect mechanisms based on miRNA modulation.

Gene Expression Profile Analysis of Human Epidermal Keratinocytes Expressing Human Papillomavirus Type 8 E7

Background: Human papillomavirus type 8 (HPV8) has been implicated in the progress of non-melanoma skin cancers and their precursor lesions. The HPV8 E7 oncoprotein plays a key role in the tumorigenesis of HPV-associated cutaneous tumors. However, the exact role of HPV8 E7 in human epidermal carcinogenesis has not been fully elucidated.

Methods: To investigate the potential carcinogenic effects of HPV8 E7 on epithelial cells, we used RNA-sequencing technology to analyze the gene expression profile of HPV8 E7-overexpressed normal human epidermal keratinocytes (NHEKs).

Results: RNA-sequencing revealed 831 differentially expressed genes (DEGs) between HPV8 E7-expressing NHEKs and control cells, among which, 631 genes were significantly upregulated, and 200 were downregulated. Gene ontology annotation enrichment analysis showed that HPV8 E7 mainly affected the expression of genes associated with protein heterodimerization activity, DNA binding, nucleosomes, and nucleosome assembly. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis revealed that overexpression of HPV8 E7 affected the expression of gene clusters associated with viral carcinogenesis and transcriptional misregulation in cancer and necroptosis signaling pathways that reportedly play crucial roles in HPV infection promotion and cancer progression. We also found the DEGs, such as HKDC1 and TNFAIP3, were associated with epigenetic modifications, immune regulation, and metabolic pathways.

Conclusion: Our results demonstrate that the pro-carcinogenic effect of HPV8 expression in epithelial cells may be attributed to the regulatory effect of oncogene E7 on gene expression associated with epigenetic modifications and immune and metabolic status-associated gene expression. Although our data are based on an in vitro experiment, it provides the theoretical evidence that the development of squamous cell carcinoma can be caused by HPV.

Molecular Mechanisms of HIV Protease Inhibitors Against HPV-Associated Cervical Cancer: Restoration of TP53 Tumour Suppressor Activities

Cervical cancer is a Human Papilloma virus-related disease, which is on the rise in a number of countries, globally. Two essential oncogenes, E6 and E7, drive cell transformation and cancer development. These two oncoproteins target two of the most important tumour suppressors, p53 and pRB, for degradation through the ubiquitin ligase pathway, thus, blocking apoptosis activation and deregulation of cell cycle. This pathway can be exploited for anticancer therapeutic interventions, and Human Immunodeficiency Virus Protease Inhibitors (HIV-PIs) have attracted a lot of attention for this anticancer drug development. HIV-PIs have proven effective in treating HPV-positive cervical cancers and shown to restore impaired or deregulated p53 in HPV-associated cervical cancers by inhibiting the 26S proteasome. This review will evaluate the role players, such as HPV oncoproteins involved cervical cancer development and how they are targeted in HIV protease inhibitors-induced p53 restoration in cervical cancer. This review also covers the therapeutic potential of HIV protease inhibitors and molecular mechanisms behind the HIV protease inhibitors-induced p53-dependent anticancer activities against cervical cancer.

HPV8 Reverses the Transcriptional Output in Lrig1 Positive Cells to Drive Skin Tumorigenesis

K14-HPV8-CER transgenic mice express the complete early genome region of human papillomavirus type 8 (HPV8) and develop skin tumours attributed to the expansion of the Lrig1+ stem cell population. The correlation between HPV8-induced changes in transcriptional output in the stem cell compartment remains poorly understood. To further understand the oncogenic pathways underlying skin tumour formation we examined the gene expression network in skin tumours of K14-HPV8-CER mice and compared the differentially expressed genes (DEG) with those of the Lrig1-EGFP-ires-CreERT2 mice. Here, we report 397 DEGs in skin tumours of K14-HPV8-CER mice, of which 181 genes were up- and 216 were down-regulated. Gene ontology and KEGG pathway enrichment analyses suggest that the 397 DEGs are acting in signalling pathways known to be involved in skin homeostasis. Interestingly, we found that HPV8 early gene expression subverts the expression pattern of 23 cellular genes known to be expressed in Lrig1+ keratinocytes. Furthermore, we identified putative upstream regulating transcription factors as well as miRNAs in the control of these genes. These data provide strong evidence that HPV8 mediated transcriptional changes may contribute to skin tumorigenesis, offering new insights into the mechanism of HPV8 driven oncogenesis.

Restriction of viral gene expression and replication prevents immortalization of human keratinocytes by a beta-human papillomavirus

High-risk (HR) human papillomaviruses (HPV) from the genus alpha cause anogenital and oropharyngeal cancers, whereas the contribution of HPV from the genus beta to the development of cutaneous squamous cell cancer is still under debate. HR-HPV genomes display potent immortalizing activity in human keratinocytes, the natural target cell for HPV. This paper shows that immortalization of keratinocytes by the beta-HPV49 genome requires the inactivation of the viral E8^E2 repressor protein and the presence of the E6 and E7 oncoproteins but also of the E1 and E2 replication proteins. This reveals important differences in the carcinogenic properties of HR-HPV and beta-HPV but also warrants further investigations on the distribution and mutation frequencies of beta-HPV in human cancers.

Beta-human papillomaviruses (HPV) have been implicated in the development of cutaneous squamous cell cancer (cSCC) in epidermodysplasia verruciformis (EV) patients and organ transplant recipients. In contrast to high-risk (HR) HPV, which cause anogenital and oropharyngeal cancers, immortalizing activity of complete beta-HPV genomes in normal human keratinocytes (NHK), the natural target cells for HPV, has not been reported. We now demonstrate that the beta-HPV49 wild-type genome is transcriptionally active in NHK but lacks immortalizing activity unless the E8 gene, which encodes the E8^E2 repressor, is inactivated. HPV49 E8− immortalized keratinocytes maintain high levels of viral gene expression and very high copy numbers of extrachromosomal viral genomes during long-term cultivation. Not only disruption of the viral E6 and E7 oncogenes but also of the E1 or E2 replication genes renders E8− genomes incapable of immortalization. E8−/E1− and E8−/E2− genomes display greatly reduced E6 and E7 RNA levels in short-term assays. This strongly suggests that high-level expression of E6 and E7 from extrachromosomal templates is necessary for immortalization. The requirement for an inactivation of E8 while maintaining E1 and E2 expression highlights important differences in the carcinogenic properties of HR-HPV and beta-HPV. These findings strengthen the notion that beta-HPV have carcinogenic potential that warrants further investigations into the distribution of beta-HPV in human cancers.

E6/E7 from Beta-2-HPVs 122, 38b, and 107 possess transforming properties in a fibroblast model in vitro

Beta-2 Human papillomaviruses 38b, 107, and 122 have been frequently found in cervical cancer samples in western Mexico. Because their E6/E7 genes functions are not fully elucidated, we deepen into their transformation capabilities. To achieve this goal, primary human fibroblasts (FB) were transduced with E6/E7 genotype-specific viral particles. Additionally, E6/E7 from HPVs 16 and 18 were included as controls. All E6/E7-cell models increased their lifespan; however, it is important to highlight that FB-E6/E7-122 showed growth as accelerated as FB-E6/E7-16 and 18. Furthermore, both FB-E6/E7-38b and 122 exhibited abilities to migrate, and FB-E6/E7-122 presented high invasive capacity. On the other hand, ΔNp73 expression was found in all cell models, except for FB-pLVX (empty-vector). Finally, RNAseq found differentially expressed genes enriched in signaling pathways related to cell cycle, epithelial-mesenchymal transition, and cancer, among others. This study shows for the first time, the great transformative potential that genotypes of the Beta-2 also possess, especially HPV122. These Beta-2 HPVs can modulate some of the genes that are well known to be regulated by Alpha-HPVs, however, they also possess alternative strategies to modulate diverse signaling pathways. These data support the idea that Beta-2 HPVs should play an important role in co-infections with Alpha-HPV during carcinogenesis.

Protamine Sulfate Is a Potent Inhibitor of Human Papillomavirus Infection In Vitro and In Vivo

Human papillomavirus (HPV) infections are transmitted through sexual or other close contact and are etiologically associated with epithelial warts, papillomas, and intraepithelial lesions that may progress to cancer. Indeed, 4.8% of the global cancer burden is linked to HPV infection. Highly effective vaccines protect against two to nine of the most medically important HPV genotypes, yet vaccine uptake is inadequate and/or cost prohibitive in many settings. With HPV-related cancer incidence expected to rise over the coming decades, there is a need for effective HPV microbicides. Herein, we demonstrate the strong inhibitory activity of the heparin-neutralizing drug protamine sulfate (PS) against HPV infection. Pretreatment of cells with PS greatly reduced infection, regardless of HPV genotype or virus source. Vaginal application of PS prevented infection of the murine genital tract by HPV pseudovirions. Time-of-addition assays where PS was added to cells before infection, during infection, or after viral attachment demonstrated strong inhibitory activities on early infection steps. No effect on virus infection was found for cell lines deficient in heparan sulfate expression, suggesting that PS binds to heparan sulfate on the cell surface. Consistent with this, prophylactic PS exposure prevented viral attachment, including under low-pH conditions akin to the human vaginal tract. Our findings suggest PS acts dually to prevent HPV infection: prophylactic treatment prevents HPV attachment to host cells, and postattachment administration alters viral entry. Clinical trials are warranted to determine whether protamine-based products are effective as topical microbicides against genital HPVs.

Cutaneous beta HPVs, sun exposure and risk of squamous and basal cell skin cancers in Australia

BACKGROUND

Sun exposure causes cutaneous squamous (SCC) and basal cell (BCC) carcinomas. Human papillomavirus (HPV) infection might cause SCC.

METHODS

We examined associations of beta and gamma HPV infection in skin-swab DNA and serum antibodies with skin cancer risk, and modification of the carcinogenic effects of sun exposure by them, in case-control studies of 385 SCC cases, 832 BCC cases and 1100 controls nested in an Australian prospective cohort study (enrolled 2006-2009).

RESULTS

Presence of beta-1 and beta-3 HPV DNA appeared to increase risks for SCC and BCC by 30%-40% (P adjusted <0.01). BCC was also associated with genus beta DNA, OR=1.48; 95%CI 1.10-2.00 (P adjusted <0.01). Associations were strengthened with each additional positive beta HPV DNA type: SCC (OR=1.07; 95%CI 1.02-1.12) and BCC (OR=1.06; 95%CI 1.03-1.10), P trend <0.01. Positivity to genus beta or gamma in serology, and genus gamma in DNA, was not associated with either cancer. There was little evidence that any beta HPV type was more strongly associated than others with either cancer. A weaker association of sun-exposure with SCC and BCC in the presence of beta-3 HPVs than in their absence suggests that beta-3 HPVs modify sun exposure's effect.

CONCLUSIONS

Our substantive findings are at the level of genus beta HPV. Like SCC, BCC risk may increase with increasing numbers of beta HPV types on skin.

IMPACT

The consistency in our findings that HPV infection may moderate the effects of sun exposure, the main environmental cause of SCC and BCC, merits further investigation.

The Mus musculus Papillomavirus Type 1 E7 Protein Binds to the Retinoblastoma Tumor Suppressor: Implications for Viral Pathogenesis

The species specificity of papillomaviruses has been a significant roadblock for performing in vivo pathogenesis studies in common model organisms. The Mus musculus papillomavirus type 1 (MmuPV1) causes cutaneous papillomas that can progress to squamous cell carcinomas in laboratory mice. The papillomavirus E6 and E7 genes encode proteins that establish and maintain a cellular milieu that allows for viral genome synthesis and viral progeny synthesis in growth-arrested, terminally differentiated keratinocytes. The E6 and E7 proteins provide this activity by binding to and functionally reprogramming key cellular regulatory proteins. The MmuPV1 E7 protein lacks the canonical LXCXE motif that mediates the binding of multiple viral oncoproteins to the cellular retinoblastoma tumor suppressor protein, RB1. Our proteomic experiments, however, revealed that MmuPV1 E7 still interacts with RB1. We show that MmuPV1 E7 interacts through its C terminus with the C-terminal domain of RB1. Binding of MmuPV1 E7 to RB1 did not cause significant activation of E2F-regulated cellular genes. MmuPV1 E7 expression was shown to be essential for papilloma formation. Experimental infection of mice with MmuPV1 expressing an E7 mutant that is defective for binding to RB1 caused delayed onset, lower incidence, and smaller sizes of papillomas. Our results demonstrate that the MmuPV1 E7 gene is essential and that targeting noncanonical activities of RB1, which are independent of RB1's ability to modulate the expression of E2F-regulated genes, contribute to papillomavirus-mediated pathogenesis. IMPORTANCE Papillomavirus infections cause a variety of epithelial hyperplastic lesions, or warts. While most warts are benign, some papillomaviruses cause lesions that can progress to squamous cell carcinomas, and approximately 5% of all human cancers are caused by human papillomavirus (HPV) infections. The papillomavirus E6 and E7 proteins are thought to function to reprogram host epithelial cells to enable viral genome replication in terminally differentiated, normally growth-arrested cells. E6 and E7 lack enzymatic activities and function by interacting and functionally altering host cell regulatory proteins. Many cellular proteins that can interact with E6 and E7 have been identified, but the biological relevance of these interactions for viral pathogenesis has not been determined. This is because papillomaviruses are species specific and do not infect heterologous hosts. Here, we use a recently established mouse papillomavirus (MmuPV1) model to investigate the role of the E7 protein in viral pathogenesis. We show that MmuPV1 E7 is necessary for papilloma formation. The retinoblastoma tumor suppressor protein (RB1) is targeted by many papillomaviral E7 proteins, including cancer-associated HPVs. We show that MmuPV1 E7 can bind RB1 and that infection with a mutant MmuPV1 virus that expresses an RB1 binding-defective E7 mutant caused smaller and fewer papillomas that arise with delayed kinetics.

Molecular Characterization of Human Papillomavirus Type 159 (HPV159)

Human papillomavirus type 159 (HPV159) was identified in an anal swab sample and preliminarily genetically characterized by our group in 2012. Here we present a detailed molecular in silico analysis that showed that the HPV159 viral genome is 7443 bp in length and divided into five early and two late genes, with conserved functional domains and motifs, and a non-coding long control region (LCR) with significant regulatory sequences that allow the virus to complete its life cycle and infect novel host cells. HPV159, clustering into the cutaneotropic Betapapillomavirus (Beta-PV) genus, is phylogenetically most similar to HPV9, forming an individual phylogenetic group in the viral species Beta-2. After testing a large representative collection of clinical samples with HPV159 type-specific RT-PCR, in addition to the anal canal from which the first HPV159 isolate was obtained, HPV159 was further detected in other muco-cutaneous (4/181, 2.2%), mucosal (22/764, 2.9%), and cutaneous (14/554, 2.5%) clinical samples, suggesting its extensive tissue tropism. However, because very low HPV159 viral loads were estimated in the majority of positive samples, it seemed that HPV159 mainly caused clinically insignificant infections of the skin and mucosa. Using newly developed, highly sensitive HPV159-specific nested PCRs, two additional HPV159 LCR viral variants were identified. Nevertheless, all HPV159 mutations were demonstrated outside important functional domains of the LCR, suggesting that the HPV159 viral variants were most probably not pathogenically different. This complete molecular characterization of HPV159 enhances our knowledge of the genome characteristics, tissue tropism, and phylogenetic diversity of Beta-PVs that infect humans.

Beta-Genus Human Papillomavirus 8 E6 Destabilizes the Host Genome by Promoting p300 Degradation

The beta genus of human papillomaviruses infects cutaneous keratinocytes. Their replication depends on actively proliferating cells and, thus, they conflict with the cellular response to the DNA damage frequently encountered by these cells. This review focus on one of these viruses (HPV8) that counters the cellular response to damaged DNA and mitotic errors by expressing a protein (HPV8 E6) that destabilizes a histone acetyltransferase, p300. The loss of p300 results in broad dysregulation of cell signaling that decreases genome stability. In addition to discussing phenotypes caused by p300 destabilization, the review contains a discussion of the extent to which E6 from other β-HPVs destabilizes p300, and provides a discussion on dissecting HPV8 E6 biology using mutants.

MinION nanopore sequencing and assembly of a complete human papillomavirus genome

BACKGROUND

The MinION sequencer belongs to the third generation of sequencing technology that allows for the generation of ultra-long reads, representing a potentially more effective approach to characterize entire viral genome sequences than other time-consuming and low-throughput methodologies.

METHODS

We report the use of the MinION nanopore sequencer to sequence the full-length genome of human papillomavirus (HPV)-ICB2 (7441 bp), which was previously characterized in our laboratory. Three independent MinION libraries were prepared and sequenced using either three consecutive 12 -h runs (Protocol A) or a single run of 48 h starting from a pool of three barcoded DNA libraries (Protocol B). A fully automated bioinformatics pipeline was developed for the reconstruction of the viral genome.

RESULTS

Protocols A and B generated 9,354,933 and 3,255,879 reads, respectively. Read length N50 values ranged between 6976 and 7360 nucleotides over the four sequencing runs. Bioinformatics analysis showed that both protocols allowed for the reconstruction of the whole viral genome, with pairwise percentages of identity to HPV-ICB2 of 100 % for protocol A and 99.98 % for protocol B.

CONCLUSION

Our results show that the use of the MinION nanopore sequencer represents an effective strategy for whole-genome sequencing of HPVs with a minimal error rate.

Canine Papillomavirus 2 E6 Does Not Interfere With UVB-Induced Upregulation of p53 and p53-Regulated Genes

Cutaneous papillomaviruses are oncogenic viruses that cause severe, persistent infections that can develop into skin cancers within ultraviolet (UV)-exposed skin of immunodeficient individuals, such as those with X-linked severe combined immunodeficiency (XSCID). A canine research model of XSCID exhibits a similar phenotype; these dogs develop severe canine papillomavirus 2 (CPV2) infections that often progress to cancer. Thus, the dog is a natural, spontaneous model to investigate cutaneous papillomavirus infections in immunodeficient patients. The human papillomavirus oncogene E6 contributes to cancer development, in part, by initiating degradation of the tumor suppressor protein p53, or by inhibiting upregulation of p53-dependent genes required within the cell growth arrest and apoptotic pathways, thereby leading to an accumulation of DNA damage required for oncogenesis. Currently, little is known about CPV2, and how it promotes cancer development. The aim of this study was to determine if CPV2 oncogene E6 similarly affects p53 upon activation by UV radiation, as well as the downstream p53-regulated genes necessary to control growth arrest and apoptosis. We determined that cutaneous CPV2 E6 does not degrade p53, or interfere with the upregulation of p53-regulated genes p21, Bax, Bak, or lncRNA-p21, suggesting that CPV2 may use a p53-independent mechanism to contribute to oncogenesis.

RG1-VLP and Other L2-Based, Broad-Spectrum HPV Vaccine Candidates

Licensed human papillomavirus (HPV) vaccines contain virus-like particles (VLPs) self-assembled from L1 major-capsid proteins that are remarkably effective prophylactic immunogens. However, the induced type-restricted immune response limits coverage to the included vaccine types, and costly multiplex formulations, restrictive storage and distribution conditions drive the need for next generation HPV vaccines. Vaccine candidates based upon the minor structural protein L2 are particularly promising because conserved N-terminal epitopes induce broadly cross-type neutralizing and protective antibodies. Several strategies to increase the immunological potency of such epitopes are being investigated, including concatemeric multimers, fusion to toll-like receptors ligands or T cell epitopes, as well as immunodominant presentation by different nanoparticle or VLP structures. Several promising L2-based vaccine candidates have reached or will soon enter first-in-man clinical studies. RG1-VLP present the HPV16L2 amino-acid 17–36 conserved neutralization epitope “RG1” repetitively and closely spaced on an immunodominant surface loop of HPV16 L1-VLP and small animal immunizations provide cross-protection against challenge with all medically-significant high-risk and several low-risk HPV types. With a successful current good manufacturing practice (cGMP) campaign and this promising breadth of activity, even encompassing cross-neutralization of several cutaneous HPV types, RG1-VLP are ready for a first-in-human clinical study. This review aims to provide a general overview of these candidates with a special focus on the RG1-VLP vaccine and its road to the clinic.

Effects of β-HPV on DNA damage response pathways to drive carcinogenesis: a review

The DDR is a complex signaling network responsible for the preservation of genomic integrity. Beta human papillomaviruses (β-HPVs) are able to destabilize the host genome by attenuating the DDR machinery at the molecular scale following expression of the oncogenes E6 and E7. In the event of β-HPV infection, the E6- and E7-mediated inhibition of the DDR enhances the oncogenicity of UV-induced mutations to enable carcinogenesis in an otherwise immunocompetent host, marking an important mechanistic divergence from the alpha genus of HPVs. In this review, we summarize recent updates to build upon the 'hit-and-run' hypothesis of β-HPV pathomechanism and highlight strain-dependent variations. Simultaneously, we illuminate points within the β-HPV-DDR interface that may unravel new insights for HPV viral genetics, genus-specific mechanistic models, and developments in targeted molecular therapy of β-HPV-related cancers.

A Systematic Review and Meta-Analysis: Evaluation of the β-Human Papillomavirus in Immunosuppressed Individuals with Cutaneous Squamous Cell Carcinoma

Background

Some types of beta-human papillomavirus (β-HPV) may be one of the probable causes of squamous cell carcinoma (SCC) in transplant recipients. β-HPVs are linked to SCC in the literature with small number of subjects.

Aim

Herein, the first meta-analysis was carried out on the association between β-HPVs and cutaneous SCC in immunosuppressed patients.

Methods

A systematic search was carried out in the PubMed and Scopus databases up to December 2018. The odds ratio (OR) were calculated by RevMan 5.3 software and the event rate (ER) by Comprehensive Meta-Analysis 2.0 software with a 95% confidence interval (CI).

Results

A total of 1250 records were identified through the two databases, but at last eleven studies were included in the meta-analysis that they were published from 1989 to 2018. The results showed a significantly high prevalence of β-HPVs in cutaneous SCC patients (ER = 69.1%; 95%CI: 58.7%, 77.8%). In addition, the prevalence of overall β-HPVs and β-HPVs of 5, 8, 9, 17, 49, 75, and 76 in immunosuppressed cutaneous SCC patients was significantly higher compared with controls.

Conclusions

The findings of the present meta-analysis support the hypothesis that β-HPV may play a role in cutaneous SCC development in immunosuppressed individuals.

Expression of a TMC6-TMC8-CIB1 heterotrimeric complex in lymphocytes is regulated by each of the components

The TMC genes encode a set of homologous transmembrane proteins whose functions are not well understood. Biallelic mutations in either TMC6 or TMC8 are detected in more than half of cases of the pre-malignant skin disease epidermodysplasia verruciformis (EV). It is controversial whether EV induced by mutations in TMC6 or TMC8 originates from keratinocyte or lymphocyte defects. Quantification of TMC6 and TMC8 RNA levels in various organs revealed that lymphoid tissues have the highest levels of expression of both genes, and custom antibodies confirmed protein expression in mouse lymphocytes. To study the function of these proteins we generated mice with targeted deletion mutant alleles of Tmc6 or Tmc8 Either TMC6 or TMC8 deficiency induced a reduction in apparent molecular weight and/or amount of the other TMC molecule. Co-immunoprecipitation experiments indicated that TMC6 and TMC8 formed a protein complex in mouse and human T cells. MS and biochemical analysis demonstrated that TMC6 and TMC8 additionally interacted with the CIB1 protein to form TMC6-TMC8-CIB1 trimers. We demonstrated that TMC6 and TMC8 regulated CIB1 levels by protecting CIB1 from ubiquitination and proteasomal degradation. Reciprocally, CIB1 was needed for stabilizing TMC6 and TMC8 levels. These results suggest why inactivating mutations in any of the three human genes leads to similar clinical presentations. We also demonstrated that TMC6 and TMC8 levels are drastically lower and the proteins are less active in regulating CIB1 in keratinocytes than in T cells. Our study suggests that defects in lymphocytes may contribute to the etiology and pathogenesis of EV.

Progress in L2-Based Prophylactic Vaccine Development for Protection against Diverse Human Papillomavirus Genotypes and Associated Diseases

The human papillomaviruses (HPVs) are a family of small DNA tumor viruses including over 200 genotypes classified by phylogeny into several genera. Different genera of HPVs cause ano-genital and oropharyngeal cancers, skin cancers, as well as benign diseases including skin and genital warts. Licensed vaccines composed of L1 virus-like particles (VLPs) confer protection generally restricted to the ≤9 HPV types targeted. Here, we examine approaches aimed at broadening the protection against diverse HPV types by targeting conserved epitopes of the minor capsid protein, L2. Compared to L1 VLP, L2 is less immunogenic. However, with appropriate presentation to the immune system, L2 can elicit durable, broadly cross-neutralizing antibody responses and protection against skin and genital challenge with diverse HPV types. Such approaches to enhance the strength and breadth of the humoral response include the display of L2 peptides on VLPs or viral capsids, bacteria, thioredoxin and other platforms for multimerization. Neither L2 nor L1 vaccinations elicit a therapeutic response. However, fusion of L2 with early viral antigens has the potential to elicit both prophylactic and therapeutic immunity. This review of cross-protective HPV vaccines based on L2 is timely as several candidates have recently entered early-phase clinical trials.

β-HPV 8E6 combined with TERT expression promotes long-term proliferation and genome instability after cytokinesis failure

Human papillomavirus (HPV) is a family of viruses divided into five genera: alpha, beta, gamma, mu, and nu. There is an ongoing discussion about whether beta genus HPVs (β-HPVs) contribute to cutaneous squamous cell carcinoma (cSCC). The data presented here add to this conversation by determining how a β-HPV E6 protein (β-HPV 8E6) alters the cellular response to cytokinesis failure. Specifically, cells were observed after cytokinesis failure was induced by dihydrocytochalasin B (H2CB). β-HPV 8E6 attenuated the immediate toxicity associated with H2CB but did not promote long-term proliferation after H2CB. Immortalization by telomerase reverse transcriptase (TERT) activation also rarely allowed cells to sustain proliferation after H2CB exposure. In contrast, TERT expression combined with β-HPV 8E6 expression allowed cells to proliferate for months following cytokinesis failure. However, this continued proliferation comes with genome destabilizing consequences. Cells that survived H2CB-induced cytokinesis failure suffered from changes in ploidy.

Expression of different L1 isoforms of Mastomys natalensis papillomavirus as mechanism to circumvent adaptive immunity

Although many high-risk mucosal and cutaneous human papillomaviruses (HPVs) theoretically have the potential to synthesize L1 isoforms differing in length, previous seroepidemiological studies only focused on the short L1 variants, co-assembling with L2 to infectious virions. Using the multimammate mouse Mastomys coucha as preclinical model, this is the first study demonstrating seroconversion against different L1 isoforms during the natural course of papillomavirus infection. Intriguingly, positivity with the cutaneous MnPV was accompanied by a strong seroresponse against a longer L1 isoform, but to our surprise, the raised antibodies were non-neutralizing. Only after a delay of around 4 months, protecting antibodies against the short L1 appeared, enabling the virus to successfully establish an infection. This argues for a novel humoral immune escape mechanism that may also have important implications on the interpretation of epidemiological data in terms of seropositivity and protection of PV infections in general.

Footprint of the host restriction factors APOBEC3 on the genome of human viruses

APOBEC3 enzymes are innate immune effectors that introduce mutations into viral genomes. These enzymes are cytidine deaminases which transform cytosine into uracil. They preferentially mutate cytidine preceded by thymidine making the 5'TC motif their favored target. Viruses have evolved different strategies to evade APOBEC3 restriction. Certain viruses actively encode viral proteins antagonizing the APOBEC3s, others passively face the APOBEC3 selection pressure thanks to a depleted genome for APOBEC3-targeted motifs. Hence, the APOBEC3s left on the genome of certain viruses an evolutionary footprint. The aim of our study is the identification of these viruses having a genome shaped by the APOBEC3s. We analyzed the genome of 33,400 human viruses for the depletion of APOBEC3-favored motifs. We demonstrate that the APOBEC3 selection pressure impacts at least 22% of all currently annotated human viral species. The papillomaviridae and polyomaviridae are the most intensively footprinted families; evidencing a selection pressure acting genome-wide and on both strands. Members of the parvoviridae family are differentially targeted in term of both magnitude and localization of the footprint. Interestingly, a massive APOBEC3 footprint is present on both strands of the B19 erythroparvovirus; making this viral genome one of the most cleaned sequences for APOBEC3-favored motifs. We also identified the endemic coronaviridae as significantly footprinted. Interestingly, no such footprint has been detected on the zoonotic MERS-CoV, SARS-CoV-1 and SARS-CoV-2 coronaviruses. In addition to viruses that are footprinted genome-wide, certain viruses are footprinted only on very short sections of their genome. That is the case for the gamma-herpesviridae and adenoviridae where the footprint is localized on the lytic origins of replication. A mild footprint can also be detected on the negative strand of the reverse transcribing HIV-1, HIV-2, HTLV-1 and HBV viruses. Together, our data illustrate the extent of the APOBEC3 selection pressure on the human viruses and identify new putatively APOBEC3-targeted viruses.

Transforming Properties of Beta-3 Human Papillomavirus E6 and E7 Proteins

The beta human papillomaviruses (HPVs) are subdivided into 5 species (beta-1 to beta-5), and they were first identified in the skin. However, the beta-3 species appears to be more highly represented in the mucosal epithelia than in the skin. Functional studies have also highlighted that beta-3 HPV49 shares some functional similarities with mucosal high-risk (HR) HPV16. Here, we describe the characterization of the in vitro transforming properties of the entire beta-3 species, which includes three additional HPV types: HPV75, HPV76, and HPV115. HPV49, HPV75, and HPV76 E6 and E7 (E6/E7), but not HPV115 E6 and E7, efficiently inactivate the p53 and pRb pathways and immortalize or extend the life span of human foreskin keratinocytes (HFKs). As observed for HR HPV16, cell cycle deregulation mediated by beta-3 HPV E6/E7 expression leads to p16INK4a accumulation, whereas no p16INK4a was detected in beta-2 HPV38 E6/E7 HFKs. As shown for HPV49 E6, HPV75 and HPV76 E6s degrade p53 by an E6AP/proteasome-mediated mechanism. Comparative analysis of cellular gene expression patterns of HFKs containing E6 and E7 from HR HPV16, beta-3 HPV types, and beta-2 HPV38 further highlights the functional similarities of HR HPV16 and beta-3 HPV49, HPV75, and HPV76. The expression profiles of these four HPV HFKs show some similarities and diverge substantially from those of beta-3 HPV115 E6/E7 and beta-2 HPV38 E6/E7 HFKs. In summary, our data show that beta-3 HPV types share some mechanisms with HR HPV types and pave the way for additional studies aiming to evaluate their potential role in human pathologies.IMPORTANCE Human papillomaviruses are currently classified in different genera. Mucosal HPVs belonging to the alpha genus have been clearly associated with carcinogenesis of the mucosal epithelium at different sites. Beta HPV types have been classified as cutaneous. Although findings indicate that some beta HPVs from species 1 and 2 play a role, together with UV irradiation, in skin cancer, very little is known about the transforming properties of most of the beta HPVs. This report shows the transforming activity of E6 and E7 from beta-3 HPV types. Moreover, it highlights that beta-3 HPVs share some biological properties more extensively with mucosal high-risk HPV16 than with beta-2 HPV38. This report provides new paradigms for a better understanding of the biology of the different HPV types and their possible association with lesions at mucosal and/or cutaneous epithelia.

Beta human papillomaviruses infection and skin carcinogenesis

During the last decade, the worldwide incidence of keratinocyte carcinomas (KC) has increased significantly. They are now the most common malignancy, representing approximately 30% of all cancers. The role of ultraviolet (UV) radiation as a major environmental risk factor for skin cancers is well recognized. The aim of this review is to analyse the current understanding of the nature of beta-human papillomavirus (HPV) and its association with KC and explore the implications for the management and prevention of these cancers. A comprehensive review of the literature on beta-HPV and its association with KC was undertaken, the results reported in the form of a narrative review. A subgroup of HPV that infects the mucosal epithelia of the genital tract has been firmly associated with carcinogenesis. In addition, some HPV types with cutaneous tropism have been proposed to cooperate with UV in the development of KC. The first evidence for this association was reported in 1922 in patients with epidermodysplasia verruciformis (EV). Since then, epidemiological studies have highlighted the higher risk of skin cancer in patients with EV and certain cutaneous HPV types, and in vitro studies have elucidated molecular mechanisms and transforming properties of beta-HPV. Furthermore, in vivo research conducted on transgenic mice models has shown the possible role of beta-HPV in cutaneous carcinogenesis as a co-factor with UV radiation and immunosuppression. There is good evidence supporting the role of beta-HPV in the oncogenesis of KC. The high prevalence of beta-HPV in human skin and the worldwide burden of KC makes the search for an effective vaccine relevant and worthwhile.

Detection of Alpha, Beta, Gamma, and Unclassified Human Papillomaviruses in Cervical Cancer Samples From Mexican Women

Background: Cervical cancer (CC) is associated to high-risk human papillomavirus (HPV) infections, for this reason it is crucial to have sensitive and accurate HPV diagnostic tests. To date, most research is focused on HPVs within the Alphapapillomavirus (α-PVs) genus and little attention has been paid to cervical infections with other HPV genotypes, like those of the Betapapillomavirus (β-PVs) and Gammapapillomavirus (γ-PVs) genera. The aim of this study was to determine the HPV genotypes from different genera in women with CC using Next-Generation Sequencing (NGS). Methods: The study comprised 48 HPV positive CC samples evaluated with the Linear Array HPV Genotyping test and individually sequenced by 454 NGS using PGMY09/11 and FAP primers. To determine the HPV genotypes present in each sample, the obtained sequences were compared with all HPV L1 gene reference sequences from the Papillomavirus Episteme database (PaVE). Moreover, 50 HPV positive low-grade cervical lesion samples individually genotyped with NGS were also included to determine the genotypes present preferentially in CC patients. Results: Among the 48 CC samples, 68.75% consisted of multiple HPV infections, 51 different genotypes were detected, of which 7 are still unclassified, 28 belong to α-PVs (6, 11, 16, 18, 26, 30, 33, 35, 39, 42, 43, 44, 45, 51, 52, 53, 54, 59, 62, 66, 68, 69, 70, 71, 74, 81, 102, 114), 10 to β-PVs (5, 12, 21, 37, 38b, 47, 80, 107, 118, 122), and 6 to γ-PVs (101, 103, 123, 135, 147, 214). Among them, HPV16 was the most prevalent genotype (54.2%), followed by HPV18 (16.7%), HPV38b (14.6%), and HPVs 52/62/80 (8.3%). Some genotypes were exclusively found in CC when compared with Cervical Intraepithelial Neoplasia grade 1 (CIN1) samples, such as HPVs 5, 18, 38b, 107, 122, FA39, FA116, mSK_120, and mSK_136. Conclusions: This work demonstrates the great diversity of HPV genotypes detected by combining PGMY and FAP primers with NGS in cervical swabs. The relatively high attribution of β- and γ- PVs in CC samples suggest their possible role as carcinogenic cofactors, but deeper studies need to be performed to determine if they have transforming properties and the significance of HPV-coinfections.

Detection of human papillomaviruses in paired healthy skin and actinic keratosis by next generation sequencing

Actinic keratosis (AK) arises on photo-damaged skin and is considered to be the precursor lesion of cutaneous squamous cell carcinoma (cSCC). Many findings support the involvement of β human papillomaviruses (HPVs) in cSCC, while very little is known on γ HPV types. The objective of this study was to characterize the spectrum of PV types in healthy skin (HS) and AK samples of the same immunocompetent individuals using next generation sequencing (NGS). Viral DNA of 244 AK and 242 HS specimens were amplified by PCR using two different sets of primers (FAP59/64 and FAPM1). Purified amplicons were pooled and sequenced using NGS. The study resulted in the identification of a large number of known β and γ PV types. In addition, 27 putative novel β and 16 γ and 4 unclassified PVs were isolated. HPV types of species γ-1 (e.g. HPV4) appeared to be strongly enriched in AK versus HS. The NGS analysis revealed that a large spectrum of known and novel PVs is present in HS and AK. The evidence that species γ-1 HPV types appears to be enriched in AK in comparison to HS warrants further studies to evaluate their role in development of skin (pre)cancerous lesions.

Development of a β-HPV vaccine: Updates on an emerging frontier of skin cancer prevention

Human papillomaviruses (HPVs) are small, non-enveloped, doublestranded DNA viruses. Over 200 subtypes of HPV have been identified, organized into five major genera. β-HPVs are a group of approximately 50 HPV subtypes that preferentially infect cutaneous sites. While α-HPVs are primarily responsible for genital lesions and mucosal cancers, growing evidence has established an association between β-HPVs and the development of cutaneous squamous cell carcinomas. Given this association, the development of a vaccine against β-HPVs has become an important topic of research; however, currently licensed vaccines only provide coverage for genital HPVs, leaving β-HPV infections and their associated skin cancers unaddressed. In this review, we summarize the current advances in β-HPV vaccine development, including progress made in preclinical testing and limited clinical data. We also discuss novel findings in the viral pathomechanisms involved in β-HPV cutaneous tumorigenesis that may play a large role in future vaccine development. We hope that synthesizing the available data and advances surrounding β- HPV vaccine development will not only lead to increased dedication to vaccine development, but also heightened awareness of a future vaccine among clinicians and the public.

Beta HPV Type 15 Can Interfere With NF-κB Activity and Apoptosis in Human Keratinocytes

E7 protein from cutaneous as well as mucosal HPV types can alter NF-κB activity. Conflicting literature data show a HPV-induced up- or down-regulation of the NF-κB pathway in different cell lines. In a previous study we detected the expression of E7 gene of HPV15 in a subungual tumor of a patient affected by incontinentia pigmenti (IP). IP is a rare X-linked genodermatosis in which the IKKγ gene is altered. From observations in transgenic IKKγ defective mice, it was suggested that IKK-deficient cells may undergo rapid hyper-proliferation and apoptosis/necrosis, leading to increased pro-inflammatory cytokine production in the neighboring IKK-positive cells. The objective of this study was to ascertain if beta HPV 15 can alter apoptosis and NF-κB pathway in normal and IKKγ-deficient keratinocytes. The human immortalized keratinocyte cell line (HaCaT), and human primary keratinocyte (HPK) cells were transduced with a retrovirus expressing E6–E7 proteins of HPV 15 and IKKγ was successful silenced mimicking the HPV15 infection and IP. HPV15 E6–E7 gene expression improved NF-κB activity in human keratinocytes even when IKKγ was silenced by siRNA. In IKKγ silenced keratinocyte cells, TNF-α-induced apoptosis was strongly reduced by the expression of HPV15 E6–E7 genes. Beta HPV15 exerted this anti-apoptotic activity by decreasing pro-apoptotic BAK and cleaved Caspase 3 proteins. In conclusion, we can speculate that presence of persistent infection by beta papillomavirus might influence the biological fate of IP by altering NF-κB activation and apoptosis in IKKγ mutated cells, favoring their survival and possibly the development of tumors in the late stage of disease. Taken together, our data reinforce the importance of host genetic background in the pathogenesis of HPV-associated skin lesions.

Role of human papillomavirus infection in the etiology of vulvar cancer in Italian women

Background

Vulvar squamous cell carcinoma (VSCC) is a rare malignancy of the female genital tract. We aimed to determine the mucosal high-risk human papillomavirus (HPV)-attributable fraction of VSCCs from Italian women using multiple markers of viral infections.

Methods

VSCCs and 8 metastatic lymph node samples from 107 Italian women were analyzed by a highly type-specific multiplex genotyping assay for the presence of DNA from 119 different HPVs. Tissues were further analyzed for HPV RNA and for upregulation of the cellular protein p16^INK4a.

Results

The rate of mucosal HPV-related tumors defined by viral DNA and RNA positivity was low (7.8%). HPV16 was the most prevalent, followed by 53, 56, and 58. Only five (4.9%) p16^INK4a-positive tumors were also positive for both viral DNA and RNA. One (14.3%) metastatic lymph node sample was positive for all three markers. DNA of cutaneous HPVs was detected in only two VSCCs, i.e. genus beta types 5 and 110.

Conclusion

A small proportion of Italian VSCCs is putatively HPV-related, i.e. positive for both viral DNA and RNA of the same type, thus reinforcing the importance of HPV vaccination. Moreover, this study suggests that a direct role of HPV from genus beta and gamma in vulvar carcinogenesis is unlikely.

HPV Oncoproteins and the Ubiquitin Proteasome System: A Signature of Malignancy?

Human papillomavirus (HPV) E6 and E7 oncoproteins are critical for development and maintenance of the malignant phenotype in HPV-induced cancers. These two viral oncoproteins interfere with a plethora of cellular pathways, including the regulation of cell cycle and the control of apoptosis, which are critical in maintaining normal cellular functions. E6 and E7 bind directly with certain components of the Ubiquitin Proteasome System (UPS), enabling them to manipulate a number of important cellular pathways. These activities are the means by which HPV establishes an environment supporting the normal viral life cycle, however in some instances they can also lead to the development of malignancy. In this review, we have discussed how E6 and E7 oncoproteins from alpha and beta HPV types interact with the components of the UPS, and how this interplay contributes to the development of cancer.

Cancer susceptibility of beta HPV49 E6 and E7 transgenic mice to 4-nitroquinoline 1-oxide treatment correlates with mutational signatures of tobacco exposure

We have previously showed that a transgenic (Tg) mouse model with cytokeratin 14 promoter (K14)-driven expression of E6 and E7 from beta-3 HPV49 in the basal layer of the epidermis and of the mucosal epithelia of the digestive tract (K14 HPV49 E6/E7 Tg mice) are highly susceptible to upper digestive tract carcinogenesis upon exposure to 4-nitroquinoline 1-oxide (4NQO). Using whole-exome sequencing, we show that in K14 HPV49 E6/E7 Tg mice, development of 4NQO-induced cancers tightly correlates with the accumulation of somatic mutations in cancer-related genes. The mutational signature in 4NQO-treated mice was similar to the signature observed in humans exposed to tobacco smoking and tobacco chewing. Similar results were obtained with K14 Tg animals expressing mucosal high-risk HPV16 E6 and E7 oncogenes. Thus, beta-3 HPV49 share some functional similarities with HPV16 in Tg animals.

Catching HPV in the Homologous Recombination Cookie Jar

To replicate, the human papillomaviruses (HPVs) that cause anogenital and oropharyngeal malignancies must simultaneously activate DNA repair pathways and avoid the cell cycle arrest that normally accompanies DNA repair. For years it seemed that HPV oncogenes activated the homologous recombination pathway to facilitate the HPV lifecycle. However, recent developments show that, although homologous recombination gene expression and markers of pathway activation are increased, homologous recombination itself is attenuated. This review provides an overview of the diverse ways that HPV oncogenes manipulate homologous recombination and ideas on how the resulting dysregulation and inhibition offer opportunities for improved therapies and biomarkers.