Frequent detection of human polyomavirus 6 in keratoacanthomas

Development of a novel multi‑epitope vaccine against the pathogenic human polyomavirus V6/7 using reverse vaccinology

BACKGROUND

Human polyomaviruses contribute to human oncogenesis through persistent infections, but currently there is no effective preventive measure against the malignancies caused by this virus. Therefore, the development of a safe and effective vaccine against HPyV is of high priority.

METHODS

First, the proteomes of 2 polyomavirus species (HPyV6 and HPyV7) were downloaded from the NCBI database for the selection of the target proteins. The epitope identification process focused on selecting proteins that were crucial, associated with virulence, present on the surface, antigenic, non-toxic, and non-homologous with the human proteome. Then, the immunoinformatic methods were used to identify cytotoxic T-lymphocyte (CTL), helper T-lymphocyte (HTL), and B-cell epitopes from the target antigens, which could be used to create epitope-based vaccine. The physicochemical features of the designed vaccine were predicted through various online servers. The binding pattern and stability between the vaccine candidate and Toll-like receptors were analyzed through molecular docking and molecular dynamics (MD) simulation, while the immunogenicity of the designed vaccines was assessed using immune simulation.

RESULTS

Online tools were utilized to forecast the most optimal epitope from the immunogenic targets, including LTAg, VP1, and VP1 antigens of HPyV6 and HPyV7. A multi-epitope vaccine was developed by combining 10 CTL, 7 HTL, and 6 LBL epitopes with suitable linkers and adjuvant. The vaccine displayed 98.35% of the world's population coverage. The 3D model of the vaccine structure revealed that the majority of residues (87.7%) were located in favored regions of the Ramachandran plot. The evaluation of molecular docking and MD simulation revealed that the constructed vaccine exhibits a strong binding (-1414.0 kcal/mol) towards the host's TLR4. Moreover, the vaccine-TLR complexes remained stable throughout the dynamic conditions present in the natural environment. The immune simulation results demonstrated that the vaccine design had the capacity to elicit robust immune responses in the host.

CONCLUSION

The multi-parametric analysis revealed that the designed vaccine is capable of inducing sustained immunity against the selected polyomaviruses, although further in-vivo investigations are needed to verify its effectiveness.

Merkel cell polyomavirus and its etiological relationship with skin tumors

Viruses have been frequently identified in several human neoplasms, but the etiological role of these viruses in some tumors is still a matter of controversy. Polyomaviruses stand out among the main viruses with oncogenic capacity, specifically the Merkel cell polyomavirus (MCPyV). Recent revisions in the taxonomy of polyomaviruses have divided the Polyomaviridae family into six genera, including 117 species, with a total of 14 currently known human-infecting species. Although the oncogenicity of polyomaviruses has been widely reported in the literature since 1950, the first description of a polyomavirus as an etiological agent of a neoplasm in humans was made only in 2008 with the description of MCPyV, present in approximately 80% of cases of Merkel cell carcinoma (MCC), with the integration of its genome to that of the tumor cells and tumor-specific mutations, and it is considered the etiological agent of this neoplasm since then. MCPyV has also been detected in keratinocyte carcinomas, such as basal cell carcinoma and squamous cell carcinoma of the skin in individuals with and without immunosuppression. Data on the occurrence of oncogenic viruses potentially involved in oncogenesis, which cause persistence and tissue injury, related to the Merkel cell polyomavirus are still scarce, and the hypothesis that the Merkel cell polyomavirus may play a relevant role in the genesis of other cutaneous carcinomas in addition to MCC remains debatable. Therefore, the present study proposes to explore the current knowledge about the presence of MCPyV in keratinocyte carcinomas.

Squamous carcinogenesis: potential truncal mutations

Squamous carcinogenesis is incompletely understood, but more recent genetic studies support that the order of acquired mutations is important. This paper will review more recent genetic studies with an emphasis on the potential truncal mutations, mutations critical to the trunk of the cancer evolutionary tree, in actinic keratosis, squamous cell carcinoma in situ, cutaneous squamous cell carcinoma, keratoacanthoma, and keratoacanthoma-like squamous proliferation.

Quantification of human polyomaviruses MCPyV and HPyV6 in malignant and non-malignant skin lesions

BACKGROUND

Human Polyomaviruses such as MCPyV and HPyV6 are frequently found as part of healthy skin microbiota and have been associated with Merkel cell carcinoma (MCC), pruritic and dyskeratotic dermatoses, respectively. Their presence in other types of skin conditions varies greatly depending on lesion type and population.

OBJECTIVE

To analyse comparatively the presence of MCPyV and HPyV6 in nonmelanoma skin cancers and healthy skin.

METHODS

The authors utilized qPCR techniques to quantify these pathogens in NMSC, premalignant diseases, and healthy skin of 87 patients.

RESULTS

MCPyV was detected in over 40% of samples, while HPyV6 was in 9.6%. MCPyV load was higher in squamous cell carcinomas (SCC) compared to basal cell carcinomas (BCC) (p=0.016) and HPyV6 showed a higher percentage of infected cells in areas of low solar exposure as well as normal skin (p=0.012). A fair agreement (kappa=0.301) was found between MCPyV detection in lesions and their respective perilesional skin, indicating a random process of local dissemination of the virus.

STUDY LIMITATIONS

The lack of a larger sampling of different lesion types and protein expression analyses limits the correlation findings.

CONCLUSION

This is the first report of HPyV6 detection in the healthy skin of a Brazilian population, but the role of both polyomaviruses in NMSC has yet to be demonstrated.

Prevalence of 13 polyomaviruses in actinic keratosis and matched healthy skin samples of immunocompetent individuals

BACKGROUND

Actinic keratosis (AK) is a precursor of cutaneous squamous cell carcinoma (cSCC). UV radiation is the major risk factor for AK, but certain human papillomaviruses (HPVs) of the beta genus are also involved in its development. Differently, the role of polyomaviruses (PyVs) in skin carcinogenesis is still debated. Fiftheen PyVs have been isolated from human tissues so far, including Merkel cell polyomavirus (MCPyV), the aetiological agent of Merkel cell carcinoma.

METHODS

The presence of 13 PyVs was assessed in skin samples from AK patients (n = 342). Matched fresh-frozen scrapings from healthy skin (HS) and AK lesions from 242 patients, and formalin-fixed paraffin-embedded AK biopsies from a different cohort of 100 patients were analyzed by multiplex PyVs genotyping assay.

RESULTS

The most frequent lesion site was the scalp in men (27.3%), and the cheek area in women (29.0%). Differences between men and women were significant for the scalp, the cheek area and the lips. Almost all the scrapings were PyV-positive (HS: 89.7%, AK: 94.6%; p = 0.04). The three most frequent PyVs were MCPyV, HPyV6 and JCPyV (HS: 87.2%, 58.7%, 6.6%, respectively; AK: 88.8%, 51.2%, 9.9%, respectively). HPyV9, TSPyV, BKPyV, HPyV7, LIPyV and SV40 were detected in < 2% of the scrapings. In most cases, matched HS and AK scrapings were both positive (MCPyV: 78.1%, HPyV6: 41.7%), or both negative for the individual genotypes (for the remaining PyVs). PyV prevalence in AK biopsies was 22.0%. Only MCPyV (21.0%) and HPyV6 (3.0%) were detected in these samples.

CONCLUSIONS

PyV prevalence in HS and AK scrapings was high, but detection of PyVs exclusively in AK scrapings was rare. PyV positivity rate in AK biopsies was modest. Further research is need to reach firm conclusions regarding the role of these viruses in AK development.

[Human polyomavirus-associated skin diseases]

Of the 15 currently known human polyomaviruses (HPyV), eight have been found on healthy skin. Merkel cell polyomavirus (MCPyV), HPyV6, HPyV7, and to a lesser extent Saint Louis polyomavirus (STLPyV) are considered part of the human cutaneous virome. The most important cutaneous polyomavirus, MCPyV, causes the majority of Merkel cell carcinomas (MCC). MCC is a rare but very aggressive malignant skin tumor that affects both immunocompetent and immunosuppressed patients. A steady increase in incidence rates of this skin tumor has been observed in recent decades. MCC occurs primarily on sunlight-exposed skin of fair-skinned individuals. Risk factors for MCC development include immunosuppression and advanced age. In immunocompromised individuals, primary infection with trichodysplasia spinulosa-associated polyomavirus (TSPyV) can cause the very rare skin disease trichodysplasia spinulosa (TS). Keratin spines (spicules), mainly in the center of the face, clinically characterize this disease. Skin lesions associated with further HPyV have been described exclusively in immunocompromised individuals. For HPyV6 and HPyV7, cases of epithelial proliferation and pruritic dyskeratotic dermatitis have been published. HPyV9 and New Jersey polyomavirus (NJPyV-13) were each found in different skin lesions of individual patients. The role of these polyomaviruses in the development of the skin lesions is still unclear.

Natural History of Cutaneous Human Polyomavirus Infection in Healthy Individuals

Several human polyomaviruses (HPyVs) were recently discovered. Merkel cell polyomavirus (MCPyV) induces Merkel cell carcinoma. HPyV6, HPyV7, and TSPyV have been associated with rare skin lesions in immunosuppressed patients. HPyV9, HPyV10, and Saint Louis Polyomavirus (STLPyV) have not been convincingly associated with any disease. The aim of this prospective study was to evaluate the cutaneous prevalence, persistence and viral load of HPyVs in healthy individuals. Eight hundred seventy forehead and hand swabs were collected from 109 volunteers 4-6 weeks apart (collection period-1). Fifty-nine participants were available for follow-up a decade later (collection period-2). HPyV-DNA prevalence and viral loads of MCPyV, HPyV6, HPyV7, TSPyV, HPyV9, HPyV10, and STLPyV were determined by virus-specific real-time PCRs. Risk factors for HPyV prevalence, short- and long-term persistence were explored by logistic regression analyses. Baseline prevalence rates were similar for forehead and hand: MCPyV 67.9/67.0%, HPyV6 31.2/25.7%, HPyV7 13.8/11.0%, HPyV10 11.9/15.6%, STLPyV 7.3/8.3%, TSPyV 0.9/0.9%, and HPyV9 0.9/0.9%. Short-term persistence in period-1 was found in 59.6% (MCPyV), 23.9% (HPyV6), 10.1% (HPyV7), 6.4% (HPyV10), 5.5% (STLPyV), and 0% (TSPyV and HPyV9) on the forehead, with similar values for the hand. Long-term persistence for 9-12 years occurred only for MCPyV (forehead/hand 39.0%/44.1% of volunteers), HPyV6 (16.9%/11.9%), and HPyV7 (3.4%/5.1%). Individuals with short-term persistence had significantly higher viral loads at baseline compared to those with transient DNA-positivity (p < 0.001 for MCPyV, HPyV6, HPyV7, and HPyV10, respectively). This was also true for median viral loads in period-1 of MCPyV, HPyV6, and HPyV7 of volunteers with long-term persistence. Multiplicity (two or more different HPyVs) was a risk factor for prevalence and persistence for most HPyVs. Further risk factors were older age for HPyV6 and male sex for MCPyV on the forehead. Smoking was not a risk factor. In contrast to MCPyV, HPyV6, HPyV7, and rarely STLPyV, polyomaviruses TSPyV, HPyV9, and HPyV10 do not seem to be long-term constituents of the human skin virome of healthy individuals. Furthermore, this study showed that higher viral loads are associated with both short- and long-term persistence of HPyVs on the skin. HPyV multiplicity is a risk factor for prevalence, short-term and/or long-term persistence of MCPyV, HPyV6, HPyV7, and HPyV10.

Emerging role of human polyomaviruses 6 and 7 in human cancers

BACKGROUND

Currently 12 human polyomaviruses (HPyVs) have been identified, 6 of which have been associated with human diseases, including cancer. The discovery of the Merkel cell polyomavirus and its role in the etiopathogenesis in the majority of Merkel cell carcinomas has drawn significant attention, also to other novel HPyVs. In 2010, HPyV6 and HPyV7 were identified in healthy skin swabs. Ever since it has been speculated that they might contribute to the etiopathogenesis of skin and non-cutaneous human cancers.

MAIN BODY

Here we comprehensively reviewed and summarized the current evidence potentially indicating an involvement of HPyV6 and HPyV7 in the etiopathogenesis of neoplastic human diseases. The seroprevalence of both HPyV6 and 7 is high in a normal population and increases with age. In skin cancer tissues, HPyV6- DNA was far more often prevalent than HPyV7 in contrast to cancers of other anatomic sites, in which HPyV7 DNA was more frequently detected.

CONCLUSION

It is remarkable to find that the detection rate of HPyV6-DNA in tissues of skin malignancies is higher than HPyV7-DNA and may indicate a role of HPyV6 in the etiopathogenesis of the respected skin cancers. However, the sheer presence of viral DNA is not enough to prove a role in the etiopathogenesis of these cancers.

Keratoacanthoma: Update on the Debate

ABSTRACT

Keratoacanthoma (KA) is a cutaneous tumor with a biphasic pattern of growth. A rapidly growing phase is usually followed by involution. KA occurs on sun-damaged skin. There are many listed causative associations, which include some therapeutic agents. Debate continues as to whether KA is a variant of squamous carcinoma (SCC) or a separate entity. Reporting of KA versus SCC is markedly inconsistent. Reasons for inconsistency include overlapping microscopic criteria, variants of KA with more aggressive features, and possibly medicolegal concerns. Genetic studies have shown some differences between the 2 entities. Activation of apoptotic pathways has been demonstrated in KA. Genetic studies have shown a possible role of human polyomavirus 6 in the pathogenesis of at least some KAs. Given that some cases of KA have components that behave as conventional SCCs, KA can be considered as a low-grade variant of SCC with some genetic differences.

Identification of Polyomaviruses in Skin Cancers

BACKGROUND

Polyomaviruses (PyVs) were initially described in animals. They have also been detected in humans with some evidence that could play a role in skin carcinogenesis.

OBJECTIVES

This study aimed to verify the presence of PyVs in different skin tumour samples and to make clinical correlations with patients' epidemiological data from Clinics Hospital of Medical School of University of São Paulo, Brazil.

METHODS

This is a cross-sectional study. A random selection was performed of 120 patients with histopathological exams of different cutaneous neoplasms equally divided into 6 groups and 20 patients with normal skin. The available skin specimens were analysed with 2 different techniques of PCR (conventional and real time) for detection of PyV DNA. Concomitantly, retrospective analysis of the respective medical records for the collection of epidemiological data was done. Analyses suitable for categorical data were used to compare the proportion of patients in each group.

RESULTS

PyV DNA was found in 25.69% of the samples: 15% in basal cell carcinoma group, 15% in squamous cell carcinoma, 28.57% in melanoma, 15% in dermatofibrosarcoma protuberans, 13.33% in Kaposi sarcoma, 65% in Merkel cell carcinoma (MCC), and none in normal skin. Merkel cell PyV detection was statistically significant in MCC patients (p value <0.01), but no correlations were found between PyVs and others skin tumours.

CONCLUSION

This study demonstrated the presence of PyVs in different skin tumours; however, no association of any PyVs found in any skin tumour with epidemiological data could be shown. Further studies are still needed to elucidate the mechanisms of PyVs in skin carcinogenesis.

HPyV6 and HPyV7 in urine from immunocompromised patients

Background

Human polyomavirus 6 (HPyV6) and HPyV7 are two of the novel polyomaviruses that were originally detected in non-diseased skin. Serological studies have shown that these viruses are ubiquitous in the healthy adult population with seroprevalence up to 88% for HPyV6 and 72% for HPyV7. Both viruses are associated with pruritic skin eruption in immunocompromised patients, but a role with other diseases in immunoincompetent patients or malignancies has not been established.

Methods

PCR was used to determine the presence of HPyV6 and HPyV7 DNA in urine samples from systemic lupus erythematosus (n = 73), multiple sclerosis (n = 50), psoriasis vulgaris (n = 15), arthritic psoriasis (n = 15) and HIV-positive patients (n = 66). In addition, urine from pregnant women (n = 47) and healthy blood donors (n = 20) was investigated.

Results

HPyV6 DNA was detected in 21 (28.8%) of the urine specimens from SLE patients, in 6 (9.1%) of the urine samples from the HIV-positive cohort, and in 19 (40.4%) samples from pregnant women. HPyV7 DNA was only found in 6 (8.2%) of the urine specimens from SLE patients and in 4 (8.5%) samples from pregnant women. No HPyV6 and HPyV7 viruria was detected in the urine samples from the other patients.

Conclusions

HPyV6, and to a lesser extend HPyV7, viruria seems to be common in SLE and HIV-positive patients, and pregnant women. Whether these viruses are of clinical relevance in these patients is not known.

High Prevalence of Human Polyomavirus 7 in Cholangiocarcinomas and Adjacent Peritumoral Hepatocytes: Preliminary Findings

Cholangiocarcinoma (CCA) is a rare biliary-duct malignancy with poor prognosis. Recently, the presence of the human polyomavirus 6 (HPyV6) has been reported in the bile of diverse hepatobiliary diseases, particularly in the bile of CCA patients. Here, we investigated the presence of novel HPyVs in CCA tissues using diverse molecular techniques to assess a possible role of HPyVs in CCA. Formalin-Fixed Paraffin-Embedded (FFPE) tissues of 42 CCA patients were included in this study. PCR-based screening for HPyVs was conducted using degenerated and HPyV-specific primers. Following that, we performed FISH, RNA in situ hybridization (RNA-ISH), and immunohistochemistry (IHC) to assess the presence of HPyVs in selected tissues. Of all 42 CCAs, 25 (59%) were positive for one HPyV, while 10 (24%) CCAs were positive for 2 HPyVs simultaneously, and 7 (17%) were negative for HPyVs. Of the total 35 positive CCAs, 19 (45%) were positive for HPyV7, 4 (9%) for HPyV6, 2 (5%) for Merkel cell polyomavirus (MCPyV), 8 (19%) for both HPyV7/MCPyV, and 2 (5%) for both HPyV6/HPyV7 as confirmed by sequencing. The presence of viral nucleic acids was confirmed by specific FISH, while the RNA-ISH confirmed the presence of HPyV6 on the single-cell level. In addition, expression of HPyV7, HPyV6, and MCPyV proteins were confirmed by IHC. Our results strongly indicate that HPyV7, HPyV6, and MCPyV infect bile duct epithelium, hepatocytes, and CCA cells, which possibly suggest an indirect role of these viruses in the etiopathogenesis of CCA. Furthermore, the observed hepatotropism of these novel HPyV, in particular HPyV7, might implicate a role of these viruses in other hepatobiliary diseases.

Human polyomavirus modulation of the host DNA damage response

The human DNA damage response (DDR) is a complex signaling network constituting many factors responsible for the preservation of genomic integrity. Human polyomaviruses (HPyVs) are able to harness the DDR machinery during their infectious cycle by expressing an array of tumor (T) antigens. These molecular interactions between human polyomavirus T antigens and the DDR create conditions that promote viral replication at the expense of host genomic stability to cause disease as well as carcinogenesis in the cases of the Merkel cell polyomavirus and BK polyomavirus. This review focuses on the six HPyVs with disease association, emphasizing strain-dependent differences in their selective manipulation of the DDR. Appreciation of the HPyV-DDR interface at a molecular scale is conducive to the development of novel therapeutic approaches.

Prevalence and Viral Loads of Cutaneous Human Polyomaviruses in the Skin of Patients With Chronic Inflammatory Skin Diseases

BACKGROUND

Human skin microorganisms have been associated with various skin diseases. However, most studies have focused on bacterial communities, and little is known about normally resident skin viruses such as the Polyomaviridae and their association with cutaneous disorders.

METHODS

We investigated the infection levels of Merkel cell polyomavirus (MCPyV), human polyomavirus 6 (HPyV6), and human polyomavirus 7 (HPyV7), using triplet skin swabs collected from lesional and nonlesional skins of 86 Japanese patients with inflammatory skin diseases and mycosis fungoides, and from 149 healthy control individuals.

RESULTS

This age-matched case-control study provides the first analyses of the loads of polyomaviruses in association with various skin diseases. The viral loads were significantly higher for HPyV6/HPyV7 and lower for MCPyV in patients with psoriasis. The viral load variation was observed not only at lesion sites, but also at clinically unaffected skin sites in most of the patients. The viral strains tested were all of the Asian/Japanese genotype.

CONCLUSIONS

Our findings suggest a covariation in the infection levels of cutaneous polyomaviruses in certain inflammatory skin conditions. Worldwide prospective longitudinal studies are warranted to understand the influence of such alterations on the pathogenesis of inflammatory skin disorders.

Evolution and molecular epidemiology of polyomaviruses

Polyomaviruses (PyVs) are small DNA viruses that infect several species, including mammals, birds and fishes. Their study gained momentum after the report of previously unidentified viral species in the past decade, and especially, since the description of the first polyomavirus clearly oncogenic for humans. The aim of this work was to review the most relevant aspects of the evolution and molecular epidemiology of polyomaviruses, allowing to reveal general evolutionary patterns and to identify some unaddressed issues and future challenges. The main points analysed included: 1) the species and genera assignation criteria; 2) the hypotheses, mechanisms and timescale of the ancient and recent evolutionary history of polyomaviruses; and 3) the molecular epidemiology of human viruses, with special attention to JC, BK and Merkel cell polyomaviruses.

Prevalence and Genetic Variability of Human Polyomaviruses 6 and 7 in Healthy Skin Among Asymptomatic Individuals

Background

Despite the pathogenetic potential of human polyomavirus 6 (HPyV6) and human polyomavirus 7 (HPyV7), they have been found in the normal skin of healthy individuals. However, little is known about the prevalence, infection levels, and geographical variations of these polyomaviruses in the skin.

Methods

Using skin swabs from 470 participants aged 2-98 years, we estimated the prevalence of copy numbers of HPyV6 and HPyV7 with respect to age and ethnicity. Phylogenetic analyses were conducted based on viral sequences obtained from Asian and white populations.

Results

This study provides the first analyses of the age-specific prevalence and levels of HPyV6 and HPyV7 infections in normal skin. Comparisons of age groups revealed that the prevalence and viral loads were significantly higher in elderly persons. Phylogenetic analyses demonstrated the existence of Asian/Japanese-specific strains genetically distinct from strains prevalent in the skin of the white population studied.

Conclusions

This large study suggests that HPyV6 and HPyV7 infections in the skin are highly prevalent in elderly adults. Further research is warranted to understand whether persistent infection with high viral loads in the skin could be a risk factor for the development of HPyV6- and HPyV7-associated skin disorders.

Polyomaviruses of the skin: integrating molecular and clinical advances in an emerging class of viruses

BACKGROUND

Human polyomaviruses (HPyVs) are small, nonenveloped, double-stranded DNA viruses that express tumour antigen proteins. Fourteen species of polyomaviruses have been discovered in humans, and since the 2008 discovery of the first cutaneous polyomavirus - Merkel cell polyomavirus (MCPyV) - six more species have been detected in the skin: trichodysplasia spinulosa-associated polyomavirus (TSPyV), HPyV6, HPyV7, HPyV9, HPyV10 and HPyV13. Of these cutaneous species, only MCPyV, TSPyV, HPyV6 and HPyV7 have been definitively associated with diseases of the skin, most commonly in immunocompromised individuals. MCPyV is a predominant aetiology in Merkel cell carcinomas. TSPyV is one of the aetiological factors of trichodysplasia spinulosa. HPyV6 and HPyV7 have been recently linked to pruritic skin eruptions. The roles of HPyV9, HPyV10 and HPyV13 in pathogenesis, if any, are still unknown, but their molecular features have provided some insight into their functional biology.

RESULTS

In this review, we summarize the known molecular mechanisms, clinical presentation and targeted therapies of each of the eight cutaneous HPyVs.

CONCLUSIONS

We hope that heightened awareness and clinical recognition of HPyVs will lead to increased reports of HPyV-associated diseases and, consequently, a more robust understanding of how to diagnose and treat these conditions.

The Biology and Clinical Features of Cutaneous Polyomaviruses

Human polyomaviruses are double-stand DNA viruses with a conserved genomic structure, yet they present with diverse tissue tropisms and disease presentations. Merkel cell polyomavirus, trichodysplasia spinulosa polyomavirus, human polyomavirus 6 and 7, and Malawi polyomavirus are shed from the skin, and Merkel cell polyomavirus, trichodysplasia spinulosa polyomavirus, human polyomavirus 6 and 7 have been linked to specific skin diseases. We present an update on the genomic and clinical features of these cutaneous polyomaviruses.

Human polyomaviruses and cancer: an overview

The name of the family Polyomaviridae, derives from the early observation that cells infected with murine polyomavirus induced multiple (poly) tumors (omas) in immunocompromised mice. Subsequent studies showed that many members of this family exhibit the capacity of mediating cell transformation and tumorigenesis in different experimental models. The transformation process mediated by these viruses is driven by viral pleiotropic regulatory proteins called T (tumor) antigens. Similar to other viral oncoproteins T antigens target cellular regulatory factors to favor cell proliferation, immune evasion and downregulation of apoptosis. The first two human polyomaviruses were isolated over 45 years ago. However, recent advances in the DNA sequencing technologies led to the rapid identification of additional twelve new polyomaviruses in different human samples. Many of these viruses establish chronic infections and have been associated with conditions in immunosuppressed individuals, particularly in organ transplant recipients. This has been associated to viral reactivation due to the immunosuppressant therapy applied to these patients. Four polyomaviruses namely, Merkel cell polyomavirus (MCPyV), Trichodysplasia spinulosa polyomavirus (TSPyV), John Cunningham Polyomavirus (JCPyV) and BK polyomavirus (BKPyV) have been associated with the development of specific malignant tumors. However, present evidence only supports the role of MCPyV as a carcinogen to humans. In the present review we present a summarized discussion on the current knowledge concerning the role of MCPyV, TSPyV, JCPyV and BKPyV in human cancers.

Phylodynamics of Merkel-cell polyomavirus and human polyomavirus 6: A long-term history with humans

New human polyomaviruses have been described in the last years, including the Merkel-cell polyomavirus (MCPyV; Human polyomavirus 5) and the Human polyomavirus 6 (HPyV6). Although their infection is usually asymptomatic, in immunocompromised host can cause life-threatening pathologies, such as the Merkel cell carcinoma, an aggressive skin neoplasia associated to the MCPyV. Despite being prevalent viruses in population, epidemiological data from South America are scarce, as well as the characterization of the viral types circulating and their origin. The aims of this work were to describe MCPyV and HPyV6 from environmental samples with different geographical origin and to analyze their phylogenetic and evolutionary histories, particularly for MCPyV. Partial and complete genome sequences were obtained from sewage samples from Argentina, Uruguay and Spain. A total number of 87 sequences were obtained for MCPyV and 33 for HPyV6. Phylogenetic analysis showed that MCPyV sequences distributed according to their geographic origin in Europe/North America, Africa, Asia, South America and Oceania groups, suggesting that viral diversification might have followed human migrations across the globe. In particular, viruses from Argentina associated with Europe/North America and South America genotypes, whereas those from Uruguay and Spain also grouped with Africa genotype, reflecting the origin of the current population in each country, which could arrive not only during ancient human migration but also during recent migratory events. In addition, the South American group presented a high level of clusterization, showing internal clusters that could be related to specific locations, such as French Guiana and Brazil or the Southern region into South America, such as Argentina and Uruguay, suggesting a long term evolutionary process in the region. Additionally, in this work, we carried out the first analysis about the evolutionary history of MCPyV trough the integration of phylogenetic, epidemiological and historical data. Since a strong association is observed between the phylogenetic relationships and the origin of the sampled population, this analysis was based on the hypothesis of co-divergence between the virus and human populations. This analysis resulted in a substitution rate of 5.1 × 10^-8 s/s/y (∼5.1% of divergence per million years) for the complete genome of MCPyV, which is in the range of those estimated for other double-stranded DNA viruses. Regarding HPyV6, a South American group with clusterization was observed (sequences from Uruguay). Meanwhile, sequences from Argentina grouped with European ones (France and Spain) and remained separated from those isolated in China, USA or Australia. The analysis of viruses from the environment allowed us to deep characterize prevalent infections in different geographic regions, reveling that viruses circulating in each population reflected its origin and that there are specific lineages associated with South America.

Multicentric cutaneous keratoacanthomas in a free-living marmoset (Callithrix sp.)

Cutaneous neoplasia is common in non-human primates. We describe the gross and microscopic features of multicentric cutaneous keratoacanthomas in a free-living marmoset (Callithrix sp.). Immunohistochemistry for human papillomavirus and herpes simplex virus type I and simplex virus type II was negative. Keratoacanthomas should be included in the differential diagnosis for cutaneous masses in non-human primates.

Human polyomavirus 6 and 7 are associated with pruritic and dyskeratotic dermatoses

BACKGROUND

Human polyomavirus (HPyV)6 and HPyV7 are shed chronically from human skin. HPyV7, but not HPyV6, has been linked to a pruritic skin eruption of immunosuppression.

OBJECTIVE

We determined whether biopsy specimens showing a characteristic pattern of dyskeratosis and parakeratosis might be associated with polyomavirus infection.

METHODS

We screened biopsy specimens showing "peacock plumage" histology by polymerase chain reaction for HPyVs. Cases positive for HPyV6 or HPyV7 were then analyzed by immunohistochemistry, electron microscopy, immunofluorescence, quantitative polymerase chain reaction, and complete sequencing, including unbiased, next-generation sequencing.

RESULTS

We identified 3 additional cases of HPyV6 or HPyV7 skin infections. Expression of T antigen and viral capsid was abundant in lesional skin. Dual immunofluorescence staining experiments confirmed that HPyV7 primarily infects keratinocytes. High viral loads in lesional skin compared with normal-appearing skin and the identification of intact virions by both electron microscopy and next-generation sequencing support a role for active viral infections in these skin diseases.

LIMITATION

This was a small case series of archived materials.

CONCLUSION

We have found that HPyV6 and HPyV7 are associated with rare, pruritic skin eruptions with a distinctive histologic pattern and describe this entity as "HPyV6- and HPyV7-associated pruritic and dyskeratotic dermatoses."

Human polyomavirus DNA detection in keratoacanthoma and Spitz naevus: no evidence for a causal role

Keratoacanthomas (KA) and Spitz naevus (SN) are both lesions with unknown aetiology; therefore, the possibility of a viral involvement, more specifically the involvement of human polyomaviruses (HPyV), was investigated. In total, 22 cases of KA and 25 cases of SN were tested for the presence of HPyVs. DNA was extracted and amplified by multiplex PCR and thereafter tested with a multiplex bead-based assay for HPyVs (BKPyV, JCPyV, KIPyV, WUPyV, MCPyV, TSPyV, HPyV6, 7 and 9) and two primate viruses (SV40 and LPyV). HPyV DNA was found in 20 of the 47 lesions. There was no significant difference in HPyV DNA detection frequency between patients diagnosed with KA and patients diagnosed with SN, nor any over-representation of a specific HPyV type in any of the two patient categories. In conclusion, evidence for a specific aetiological role of any of the above tested HPyVs in either KA or SN was not disclosed.

First detection and complete genome sequence of a phylogenetically distinct human polyomavirus 6 highly prevalent in human bile samples

Oncovirus-associated malignancies are potentially preventable diseases with major public health significance. Human polyomaviruses (HPyVs) may be associated with oncogenesis or symptomatic illnesses in immunocompromised patients, but the site of viral shedding of most recently discovered HPyVs remains obscure. Using real-time PCR assay using specific primers targeting the HPyV6 large tumor antigen gene, we detected a phylogenetically distinct HPyV6 which was highly prevalent in the bile samples of patients with malignant biliary obstruction (18.8%) and acute gallstone cholangitis (5.5%). The prevalence rate and mean viral load of this HPyV6 were highest in the cholangiocarcinoma subgroup (27.6% and 2.41 × 10⁴copies/ml). These findings were confirmed with another real-time PCR assay using specific primers targeting the HPyV6 viral capsid protein 2 gene. These bile HPyV6 strains may represent a novel clade of HPyV6 as they formed a distinct cluster from the other HPyV6s and exhibited >2% differences in amino acid sequences in their major proteins. While HPyV6 was unlikely the cause of the patients' acute symptoms and liver dysfunction, the virus may be related to immunosuppression in patients with malignancy and/or important in the oncogenesis of cholangiocarcinoma in patients without coinfection with other oncogenic microbes. Further studies to ascertain a causative role of HPyV6 in cholangiocarcinoma should be conducted.

Molecular mechanisms supporting a pathogenic role for human polyomavirus 6 small T antigen: Protein phosphatase 2A targeting and MAPK cascade activation

BRAF inhibitors are highly effective therapies in treating a subset of melanomas but are associated with induction of secondary cutaneous squamous cell carcinoma (cSCC). Recently, Human Polyomavirus 6 (HPyV6) was found to actively express viral proteins in BRAF inhibitor-induced cSCCs; however, the specific cellular mechanisms by which HPyV6 may facilitate neoplastic cell growth require further investigation. The current study describes a novel pathogenic mechanism of action for HPyV6 small tumor (sT) antigen which involves binding to protein phosphatase 2A (PP2A) via its WFG motif and zinc binding sites. Our findings demonstrate an important role of HPyV6 sT for activation of PP2A's downstream oncogenic pathways (MEK/ERK/c-Jun), which may underlie the pathogenesis of BRAF inhibitor-induced neoplasms. J. Med. Virol. 89:742-747, 2017. © 2016 Wiley Periodicals, Inc.