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The human ocular surface hosts a paucibacterial resident microbiome and virome. The factors contributing to homeostasis of this mucosal community are presently unknown. To determine the impact of ocular enucleation and prosthesis placement on the ocular surface microbiome, we sampled conjunctival swabs from 20 anophthalmic and 20 fellow-eye intact conjunctiva. DNA was extracted and subjected to quantitative 16S rDNA PCR, biome representational karyotyping (BRiSK), and quantitative PCR (qPCR) confirmation of specific organisms. 16S ribosomal qPCR revealed equivalent bacterial loads between conditions. Biome representational in silico karyotyping (BRiSK) demonstrated comparable bacterial fauna between anophthalmic and intact conjunctiva. Both torque teno virus and Merkel cell polyoma virus (MCPyV) were detected frequently in healthy and anophthalmic conjunctiva. By qPCR, MCPyV was detected in 19/20 anophthalmic samples compared with 5/20 fellow eyes. MCPyV copy number averaged 891 copies/ng in anophthalmic conjunctiva compared with 193 copies/ng in fellow eyes (p < 0.001). These results suggest that enucleation and prosthesis placement affect the ocular surface flora, particularly for the resident virome. As MCPyV has been shown to be the etiologic cause of Merkel cell carcinoma, understanding the mechanisms by which the ocular surface regulates this virus may have clinical importance., (© 2021. The Author(s).)

We previously reported a novel diagnostic method using follicle-sinus complexes (FSCs) in the muzzle skin for postmortem diagnosis of rabies in dogs. However, whether this method works in other animal species remains unclear. Here, FSCs were collected from a wolf, a red fox, 2 bats, and a cat, and examined for the presence of viral antigen, viral mRNA, and viral particles. Viral antigen and viral mRNA were confirmed in Merkel cells (MCs) in FSCs of all species. Electron microscopy performed using only samples from wolf and cat confirmed viral particles in MCs of FSCs. These results suggested that this novel diagnostic method using FSCs might be useful for detection of rabies not only in domestic but also wild animals.

In the present study, follicle-sinus complexes (FSCs) were harvested from the muzzle skin of 123 dogs with suspected canine rabies, and the sensitivity and specificity of FSC analysis were compared with those of brain tissue immunohistochemistry analysis. In the FSCs, viral antigen was detected from Merkel cells. Sensitivity was 97.3%, specificity was 100%, and the coefficient κ was 0.88. These results reconfirm that FSCs are very useful for the postmortem diagnosis of canine rabies, and suggest that 5 FSCs can yield results that are almost equivalent to those derived from brain tissue analysis in rabid dogs.

The formation of a bipolar mitotic spindle is an essential process for the equal segregation of duplicated DNA into two daughter cells during mitosis. As a result of deregulated cellular signaling pathways, cancer cells often suffer a loss of genome integrity that might etiologically contribute to carcinogenesis. Merkel cell polyomavirus (MCV) small T (sT) oncoprotein induces centrosome overduplication, aneuploidy, chromosome breakage and the formation of micronuclei by targeting cellular ligases through a sT domain that also inhibits MCV large T oncoprotein turnover. These results provide important insight as to how centrosome number and chromosomal stability can be affected by the E3 ligase targeting capacity of viral oncoproteins such as MCV sT, which may contribute to Merkel cell carcinogenesis.

The direct fluorescent antibody test (dFAT) on fresh brain tissues is the gold standard for rabies virus antigen detection in dogs. However, this method is laborious and holds a high risk of virus exposure for the experimenter. Skin biopsies are useful for the diagnosis of humans and animals. In mammals, the tactile hair, known as the follicle-sinus complex (FSC), is a specialized touch organ that is abundant in the muzzle skin. Each tactile hair is equipped with more than 2,000 sensory nerve endings. Therefore, this organ is expected to serve as an alternative postmortem diagnostic material. However, the target cells and localization of rabies virus antigen in the FSCs remain to be defined. In the present study, muzzle skins were obtained from 60 rabid dogs diagnosed with rabies by dFAT at the Research Institute of Tropical Medicine in the Philippines. In all dogs, virus antigen was clearly detected in a part of the outer root sheath at the level of the ring sinus of the FSCs, and the majority of cells were positive for the Merkel cell (MC) markers cytokeratin 20 and CAM5.2. Our results suggest that MCs in the FSCs of the muzzle skin are a target for virus replication and could serve as a useful alternative specimen source for diagnosis of rabies., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Background: Molluscum contagiosum (MC) is the commonest human poxvirus infection. Follicular induction has rarely been observed in the epidermis surrounding lesions of MC. A virus-induced localized proliferation of germinative/stem cells of the folliculosebaceous-apocrine unit has been suggested as the underlying cause, however few reports of this peculiar phenomenon exist in the literature and the mechanisms involved in this proliferation require further study., Methods: We prospectively collected MC cases showing multifocal areas of primitive follicular induction involving the adjacent undersurface epidermis. Immunohistochemical expression of BerEP4, PHLDA1 and cytokeratin 20 (CK20) was evaluated in the basaloid germs surrounding the lesions. For PHLDA1, we used epidermal melanocytes as a positive internal control. For BerEP4, we employed a basal cell carcinoma (BCC) and for CK20, colon as positive external controls. An incubation without the primary antibody functioned as an external negative control., Results: All the cases studied showed an intense positive staining of the basaloid buds with BerEP4 and weaker stain for PHLDA1. CK20 showed the presence of scattered Merkel cells within the induced epidermal basaloid proliferations favoring their reactive origin., Discussion: The pathogenetic mechanisms behind the development of these microscopic features and the link between follicular induction and poxvirus infection are explored. Awareness of this unusual phenomenon by dermatopathologists will be helpful in avoiding a misdiagnosis of a superficial BCC in such cases., Conclusions: BerEP4 and PHLDA1 were consistently expressed in the areas of primitive follicular induction surrounding lesions of MC. CK 20 stained the Merkel cells present in the basaloid buds. All these findings support the reactive origin of this phenomenon, which we believe is most probably viral-induced., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Merkel cell carcinoma (MCC) is a neuroendocrine skin malignancy frequently associated with Merkel cell polyomavirus (MCPyV), which is suspected to be oncogenic. In a series of MCC patients, we compared clinical, histopathologic, and prognostic features according to the expression of viral large T antigen (LTA) correlated with viral load. We evaluated the LTA expression by immunohistochemistry using CM2B4 antibody and quantified viral load by real-time polymerase chain reaction. We analyzed formalin-fixed, paraffin-embedded (FFPE) tissue samples (n = 36) and corresponding fresh-frozen biopsies when available (n = 12), of the primary tumor and/or metastasis from 24 patients. MCPyV was detected in 88% and 58% of MCC patients by real-time polymerase chain reaction and immunohistochemistry, respectively. The relevance of viral load measurements was demonstrated by the strong consistency of viral load level between FFPE and corresponding frozen tissues as well as between primary tumor and metastases. From FFPE samples, 2 MCC subgroups were distinguished based on a viral load threshold defined by the positivity of CM2B4 immunostaining. In the LTA-negative subgroup with no or low viral load (nonsignificant), tumor cells showed more anisokaryosis (P = .01), and a solar elastosis around the tumor was more frequently observed (P = .03). LTA-positive MCCs with significant viral load had a lower proliferation index (P = .03) and a longer survival of corresponding patients (P = .008). Depending on MCPyV involvement, 2 MCC subgroups can be distinguished on histopathologic criteria, and the CM2B4 antibody is able to differentiate them reliably. Furthermore, the presence of a significant viral load in tumors is predictive of better prognosis., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Establishment of a chronic infection is a key event in virus-mediated carcinogenesis. Several cancer-associated, double-stranded DNA (dsDNA) viruses act via their oncoproteins to downregulate Toll-like receptor 9 (TLR9), a key receptor in the host innate immune response that senses viral or bacterial dsDNA. A novel oncogenic virus, Merkel cell polyomavirus (MCPyV), has been recently identified that causes up to 80% of Merkel cell carcinomas (MCCs). However, it is not yet known whether this oncogenic virus also disrupts immune-related pathways. We find that MCPyV large T antigen (LT) expression downregulates TLR9 expression in epithelial and MCC-derived cells. Accordingly, silencing of LT expression results in upregulation of mRNA TLR9 levels. In addition, small T antigen (sT) also appears to inhibit TLR9 expression, since inhibition of its expression also resulted in an increase of TLR9 mRNA levels. LT inhibits TLR9 expression by decreasing the mRNA levels of the C/EBPβ transactivator, a positive regulator of the TLR9 promoter. Chromatin immunoprecipitation reveals that C/EBPβ binding at a C/EBPβ response element (RE) in the TLR9 promoter is strongly inhibited by expression of MCPyV early genes and that mutation of the C/EBP RE prevents MCPyV downregulation of TLR9. A survey of BK polyomavirus (BKPyV), JC polyomavirus (JCPyV), KI polyomavirus (KIPyV), MCPyV, simian virus 40 (SV40), and WU polyomavirus (WUPyV) early genes revealed that only BKPyV and MCPyV are potent inhibitors of TLR9 gene expression. MCPyV LT targeting of C/EBP transactivators is likely to play an important role in viral persistence and potentially inhibit host cell immune responses during MCPyV tumorigenesis.

Neurological complications, often due to viral reactivation, after allogeneic hematopoetic stem cell transplantation (HSCT) are associated with increased mortality. Here, cerebrospinal fluid from 20 HSCT patients with neurological symptoms were analyzed and found to be negative by PCR for BK virus, JC virus, KI, WU and Merkel cell polyomavirus DNA.

Merkel cell polyomavirus (MCV) is the recently discovered cause of most Merkel cell carcinomas (MCCs), an aggressive form of nonmelanoma skin cancer. Although MCV is known to integrate into the tumor cell genome and to undergo mutation, the molecular mechanisms used by this virus to cause cancer are unknown. Here, we show that MCV small T (sT) antigen is expressed in most MCC tumors, where it is required for tumor cell growth. Unlike the closely related SV40 sT, MCV sT transformed rodent fibroblasts to anchorage- and contact-independent growth and promoted serum-free proliferation of human cells. These effects did not involve protein phosphatase 2A (PP2A) inhibition. MCV sT was found to act downstream in the mammalian target of rapamycin (mTOR) signaling pathway to preserve eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) hyperphosphorylation, resulting in dysregulated cap-dependent translation. MCV sT-associated 4E-BP1 serine 65 hyperphosphorylation was resistant to mTOR complex (mTORC1) and mTORC2 inhibitors. Steady-state phosphorylation of other downstream Akt-mTOR targets, including S6K and 4E-BP2, was also increased by MCV sT. Expression of a constitutively active 4E-BP1 that could not be phosphorylated antagonized the cell transformation activity of MCV sT. Taken together, these experiments showed that 4E-BP1 inhibition is required for MCV transformation. Thus, MCV sT is an oncoprotein, and its effects on dysregulated cap-dependent translation have clinical implications for the prevention, diagnosis, and treatment of MCV-related cancers.

While studying the virome of the skin surface of a patient with a Merkel cell carcinoma (MCC) by using unbiased, high-throughput sequencing, we identified a human polyomavirus nearly identical to human polyomavirus 9, a virus recently reported in blood and urine of renal transplantion patients and closely related to the African green monkey lymphotropic polyomavirus. Specific PCR analysis further identified this virus in 2/8 patients with MCC but in only 1/111 controls without MCC. This virus was shed for ≥20 months by the MCC index patient and was on the skin of the spouse of the index patient. These results provide information on the viral ecology of human skin and raise new questions regarding the pathology of virus-associated skin disorders.

Merkel cell polyomavirus (MCV) has been recently described as the cause for most human Merkel cell carcinomas. MCV is similar to simian virus 40 (SV40) and encodes a nuclear large T (LT) oncoprotein that is usually mutated to eliminate viral replication among tumor-derived MCV. We identified the hVam6p cytoplasmic protein involved in lysosomal processing as a novel interactor with MCV LT but not SV40 LT. hVam6p binds through its clathrin heavy chain homology domain to a unique region of MCV LT adjacent to the retinoblastoma binding site. MCV LT translocates hVam6p to the nucleus, sequestering it from involvement in lysosomal trafficking. A naturally occurring, tumor-derived mutant LT (MCV350) lacking a nuclear localization signal binds hVam6p but fails to inhibit hVam6p-induced lysosomal clustering. MCV has evolved a novel mechanism to target hVam6p that may contribute to viral uncoating or egress through lysosomal processing during virus replication.

To explore the putative role of the Merkel cell polyomavirus in human colon cancer, a prospective molecular case-control study was undertaken in patients and their relatives enrolled during a screening program. Fresh tissue samples from 64 cases of colon cancer (mean age 69.9 ± 11.0 years; 40 males) and fresh biopsies from 80 relatives (mean age 53.7 ± 8.6 years; 43 male; 55 son/daughter, 23 brother/sister, 2 parents) were analyzed by PCR and sequencing. Pre-cancerous lesions, namely adenomas and polyps, were detected in 15 (18.8%) and 9 (11.2%) of the controls, respectively. In addition, 144 blood samples were examined. Merkel cell polyomavirus DNA was detected in 6.3% of cases and 8.8% of controls. This difference was not statistically significant in the logistic regression analysis, after adjustment for age. Whereas blood samples from both cases and controls tested negative, the DNA Merkel cell polyomavirus was identified in 12.5% of adenoma/polyp tissues. No statistically significant difference was found when prevalence rates of Merkel cell polyomavirus in normal, pre-cancerous and cancer tissues were compared. Sequence analysis of the viral LT3 and VP1 regions showed high homology (>99%) with those of strains circulating worldwide, especially with genotypes detected in France. The findings of this survey are consistent with the hypothesis that the Merkel cell polyomavirus, in addition to other human polyomaviruses, can be recovered frequently from the gastrointestinal tract, because it is transmitted throughout the fecal-oral route. Moreover, the study does not indicate a role for Merkel cell polyomavirus in the genesis of colon cancer., (Copyright © 2011 Wiley-Liss, Inc.)

Background: Merkel cell polyomavirus (MCPyV) was first identified in Merkel cell carcinoma (MCC) as a new tumor virus. Studies have also reported differing frequencies of MCPyV detection in other skin cancers in western countries., Objectives: Little is known about geographical differences of MCPyV prevalence in non-MCC tumors. We examined the existence of MCPyV in non-MCC skin cancers including squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) in Japanese patients., Study Design: Paraffin-embedded tissues of cutaneous SCC (n=30) and BCC (n=10) from Japanese patients were tested for the presence of MCPyV by polymerase chain reaction (PCR) with primer sets directed against the genes encoding large-T antigen 3 (LT3) and viral protein 1 (VP1). This was followed by DNA fragment sequencing and immunohistochemistry., Results: PCR analysis targeting the LT3 gene showed that the viral sequences were found in 4 of 30 (13%) SCC cases. Nested PCR detected the VP1 region in four cases. Sequencing analysis of these PCR-amplified fragments showed a close homology to the previously published MCPyV sequences. Immunohistochemistry with the monoclonal antibody to MCPyV LT-antigen showed positive staining in 2 of 4 LT3 PCR-positive cases. On the other hand, our BCC samples were all negative for MCPyV., Conclusion: This study suggested that Japanese cutaneous SCC is infrequently associated with MCPyV. Further worldwide epidemiological surveys are warranted to determine the possible association of MCPyV with pathogenesis of non-MCC skin cancers., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Aims: Merkel cell carcinomas (MCCs) are rare but aggressive tumours associated recently with Merkel cell polyomavirus (MCV). As development and progression of several types of carcinomas can be promoted by changes in cell adhesion proteins, the aim of this study was to examine homo- and heterotypic cell contacts of Merkel cells and MCCs., Methods and Results: Merkel cells of healthy glabrous epidermis and 52 MCCs were analysed by double-label immunostaining, immunofluorescence and confocal microscopy. Merkel cells were connected to keratinocytes by E- and P-cadherin, desmoglein 2 and desmocollin 2. In contrast, the vast majority of MCCs (90%) contained N-cadherin, but only 67% and 65% contained E- and P-cadherin, respectively. Interestingly, P-cadherin was absent significantly more frequently in lymph node metastases than in primary tumours and by trend in more advanced clinical stages. Moreover, major subsets of MCCs synthesized desmoglein 2 and, surprisingly, tight junction proteins. No significant differences were observed upon stratification for MCV DNA, detected in 84% of tumours by real-time polymerase chain reaction., Conclusions: Assuming that MCCs originate from Merkel cells, our data indicate a switch from E- and P-cadherin to N-cadherin during tumorigenesis. Whether the unexpected heterogeneity of junctional proteins can be exploited for prognostic and therapeutic purposes will need to be examined., (© 2011 Blackwell Publishing Limited.)

A clear etiopathogenetic concept for atypical fibroxanthoma (AFX) is not established yet. Nevertheless, AFX is known as a pleomorphic but indolent tumor primarily of the elderly and/or immunosuppressed patient occurring in severely sun- or radiation-damaged skin. These risk factors are almost identical to those of Merkel cell carcinoma (MCC), a highly malignant skin tumor being thought to be pathogenetically associated with the recently discovered Merkel cell polyomavirus (MCPyV). Because AFX and MCC share risk factors, the aim of this study was to evaluate presence of MCPyV DNA in 23 cases of AFX by PCR and direct DNA sequencing. Subsequently, we correlated clinical features with MCPyV DNA status in AFX. We detected MCPyV DNA in 4 of 23 AFX. All patients with MCPyV DNA-positive tumors were men. The mean age of patients with MCPyV DNA-positive AFX was 84.8 ± 8.7 years (vs. 75.2 ± 7.8 years of MCPyV DNA-negative AFX), the mean duration of tumor growth was 4.5 ± 2.3 months (vs. 5.1 ± 2.8 months) and the mean tumor diameter was 1.2 ± 0.3 cm (vs. 1.3 ± 0.7 cm). Ulceration was present in 75% of MCPyV DNA-positive tumors (vs. 65.2%). In conclusion, MCPyV DNA is present in 17% of AFX, in this cohort affecting predominantly male patients with higher age (>80 years). Clinical features seem to be independent of MCPyV DNA status. Although the role of MCPyV is unclear in this setting, it may act as a cofactor in the tumorigenesis of AFX in a subset of cases.

Polyomaviruses have been linked to diseases of immunosuppressed patients. We sought to determine the prevalence of Merkel cell polyomavirus in benign epithelial skin neoplasms and nonmelanoma skin cancer of immunosuppressed renal transplant recipients and long-term dialysis patients. Merkel cell polyomavirus DNA was detected by polymerase chain reaction (PCR) in 2 (10%) of 20 patients, in carcinomas in situ (Bowen's disease). In one of our patients with Merkel cell polyomavirus-positive carcinoma in situ, 9 (39.1%) of 23 skin lesions at various anatomical locations tested positive for Merkel cell polyomavirus sequences by PCR, including all of his common warts (4/4), half of his carcinoma in situ lesions (3/6), and 2 of his 3 seborrheic keratoses. In a second cohort of immunosuppressed renal transplant recipients, Merkel cell polyomavirus DNA was found in 1 (6.3%) of 16 common warts and in 2 (9.5%) of 21 carcinomas in situ. In immunocompetent individuals, Merkel cell polyomavirus DNA was found in 2 (6.7%) of 30 common warts and in 2 (8.3%) of 24 carcinomas in situ. DNA of other human polyomaviruses was not detected in any of the investigated skin neoplasms. We conclude that common warts and carcinomas in situ can be positive for Merkel cell polyomavirus in immunosuppressed as well as immunocompetent individuals. Remarkably, some of the Merkel cell polyomavirus-positive common warts did not contain human papillomavirus. Furthermore, Merkel cell polyomavirus can be found in various skin neoplasms of the same individual., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Background: Recently, three new polyomaviruses-KI, WU and Merkel cell (MCV)-have been discovered and their detection has been reported in different types of specimens, including respiratory samples, suggesting their shedding in the airways. In lung graft recipients, viral agents are associated with events that may limit the success of transplantation, including organ infection/disease and allograft rejection., Aims: To evaluate the prevalence of KI, WU and MCV in transbronchial biopsies from lung transplant recipients and investigate the association with clinical and histopathological features., Methods: The quantitation of new polyomaviruses DNA by real-time PCR and association with clinical and histopathological findings were evaluated in 66 transbronchial biopsies from lung transplant recipients. Results KI, WU and MCV were detected in 9.2%, 12.3% and 33.8% of specimens, respectively; with mean viral load ranging from 81 copies/10(4) cells for WU to 258 for MCV, thus not differing from that previously reported in native lungs. No significant association with clinical and histopathological findings (including acute respiratory insufficiency, interstitial and organising pneumonia, acute and chronic rejection) was found., Conclusions: Results showed a relatively high frequency of detection of the novel polyomaviruses in transbronchial biopsies from lung transplant recipients. It is likely that this accounted for the positive results found in some cases with different pathological background, although no significant association with a specific clinical and/or histopathological pattern was found.

Merkel cell carcinoma (MCC) is a rare but aggressive skin cancer involving Merkel cells. Recently, a new human polyomavirus was implicated in MCC, being present in 80% of the samples analyzed. In virus-positive MCC, the Merkel cell polyomavirus (MCPyV) is clonally integrated into the patients DNA, and carries mutations in its large T antigen, leading to a truncated protein. In non-symptomatic tissue MCPyV can reside at very low levels. MCC is also associated with older age, immunosuppression and sun exposure. However, the link with solar exposure remains unknown, as the precise mechanism and steps involved between time of infection by MCPyV and the development of MCC. We thus investigated the potential impact of solar simulated radiation (SSR) on MCPyV transcriptional activity. We screened skin samples of 20 healthy patients enrolled in a photodermatological protocol based on in vivo-administered 2 and 4 J/cm(2) SSR. Two patients were infected with two new variants of MCPyV, present in their episomal form and RT-QPCR analyses on SSR-irradiated skin samples showed a specific and unique dose-dependent increase of MCPyV small t antigen transcript. A luciferase based in vitro assay confirmed that small t promoter is indeed UV-inducible. These findings demonstrate that solar radiation has an impact on MCPyV mRNA levels that may explain the association between MCC and solar exposure.

The recently discovered human polyomavirus (MCPyV) is frequently found in Merkel cell carcinoma (MCC) tissue and is believed to be causally linked to MCC pathogenesis. While cell lines established from MCC represent a valuable tool to study the contribution of MCPyV to MCC pathogenesis, hitherto only 1 MCPyV-positive line has been described. We have analyzed 7 MCC cell lines for the presence, integration pattern and copy number of MCPyV. In 5 cell lines, MCPyV specific sequences were detected. In 3 of these lines, multiple copies of viral genomes per cell were detected, and sequencing of PCR amplificates identified distinct mutations predicted to lead to the expression of a truncated large T-Antigen (LT-Ag). In 1 cell line, clonal integration of concatamerized viral genomes was confirmed by Southern Blotting. MCC cell lines are conventionally categorized as "classic" or "variant" and further divided into 4 subtypes, based on expression of neuroendocrine markers and morphology. While it has been suggested that the presence of MCPyV might promote a classic phenotype, such a notion is not supported by our data. Instead, we find MCPyV-positive as well as -negative lines of the classic variety, indicating that the distinguishing features are either inherently independent of viral infection or have become so in the course of tumorigenesis and/or cell line establishment. We therefore suggest a novel classification scheme based on MCPyV presence, integration patterns and T-Ag mutations. The cell lines described here extend the repertoire of available MCPyV-positive MCC-lines and should aid in the elucidation of the role of MCPyV in the pathogenesis of MCC.

Merkel cell polyomavirus (MCPyV) was recently discovered in Merkel cell carcinoma (MCC), a clinically and pathologically heterogeneous malignancy of dermal neuroendocrine cells. To investigate this heterogeneity, we developed a tissue microarray (TMA) to characterize immunohistochemical staining of candidate tumor cell proteins and a quantitative PCR assay to detect MCPyV and measure viral loads. MCPyV was detected in 19 of 23 (74%) primary MCC tumors, but 8 of these had less than 1 viral copy per 300 cells. Viral abundance of 0.06-1.2 viral copies/cell was directly related to presence of retinoblastoma gene product (pRb) and terminal deoxyribonucleotidyl transferase (TdT) by immunohistochemical staining (p < or = 0.003). Higher viral abundance tumors tended to be associated with less p53 expression, younger age at diagnosis and longer survival (p < or = 0.08). These data suggest that MCC may arise through different oncogenic pathways, including ones independent of pRb and MCPyV.

The genome of a new human polyomavirus, known as Merkel cell polyomavirus (MCV), has recently been reported to be integrated within the cellular DNA of Merkel cell carcinoma (MCC), a rare human skin cancer. To investigate MCV seroprevalence in the general population, we expressed three different MCV VP1 in insect cells using recombinant baculoviruses. Viruslike particles (VLPs) were obtained with only one of the three VP1 genes. High-titer antibodies against VP1 VLPs were detected in mice immunized with MCV VLPs, and limited cross-reactivity was observed with BK polyomavirus (BKV) and lymphotropic polyomavirus (LPV). MCV antibodies were detected in 77% of the general population, with no variations according to age.

To assess the usefulness of using cutaneous swabs to detect Merkel cell polyomavirus (MCPyV) DNA, we analyzed swabs from persons with Merkel cell carcinoma (MCC), others with skin diseases, and healthy volunteers. MCPyV was detected in at least 1 sample from virtually all participants. Viral loads were higher in samples from patients with MCC.

Merkel cell polyomavirus (MCPyV) has been found to be integrated monoclonally in a rare skin cancer named Merkel cell carcinoma. More recently, MCPyV has been detected in the upper respiratory tract of pediatric and adult patients. However, the mode of transmission and pathogenic role of MCPyV in the respiratory system has not been determined. In this study, MCPyV was sought in the lower respiratory tract of adult patients admitted to the hospital. MCPyV DNA was detected in 15 (17.24%) out of 87 lower respiratory tract samples. Most of the patients with MCPyV were over 50 years old. Nucleotide sequence of the t-antigen of MCPyV identified in respiratory secretions showed a homology to those found in Merkel cell carcinoma. In addition, phylogenetic analysis undertaken on the t-antigen sequences of Italian isolates and other MCPyVs identified in healthy and cancer tissues showed that all these isolates belonged to the same clade. Selective pressure analysis for the t-antigen revealed the presence of five sites under positive selection (omega = 4.3), with a posterior probabilities above 0.99. The alpha parameter of the gamma distribution was 0.01, showing that this distribution has a characteristic L-shape and suggesting a strong nucleotide substitution rate heterogeneity across sites. This study shows that MCPyV can infect the lower respiratory tract, but further investigations are needed to define its pathogenic role in respiratory diseases. J. Med. Virol. 82:505-509, 2010. (c) 2010 Wiley-Liss, Inc.

Background: Merkel cell carcinoma (MCC) is a malignant neuroendocrine neoplasm which shares structural and immunohistochemical features with neuroectodermally derived cells. One hypothesis claims that it arises from Merkel cells, highly innervated neuroendocrine cells involved in mechanoreception in the skin. The incidence rate of this cancer increases with age and sun exposure as well as after immunosuppression. Recently, the clonal integration of a newly identified polyomavirus called Merkel cell polyomavirus (MCPyV) was reported in up to 80% of MCC tissue. Here we report the incidence rate of MCPyV in MCC patients in Switzerland., Methods: We performed polymerase chain reaction in a collection of 32 samples obtained from pathology institutes around Switzerland. We used three different published primer sets. As control groups we used 7 squamous cell carcinoma samples and 11 normal skin samples., Conclusions: We detected viral DNA in 20 out of 30 cases of MCC and in 0 out of 19 control samples. The presence of viral DNA in 66.6% of our MCC tissue specimens confirms the high prevalence of MCPyV in MCC patients described in American, German, French and Hungarian patient collections., (Copyright 2010 S. Karger AG, Basel.)

Background: BK and JC polyomaviruses (BKV and JCV) are potentially oncogenic and have in the past inconclusively been associated with tumours of the central nervous system (CNS), while BKV has been hinted, but not confirmed to be associated with neuroblastomas. Recently three new polyomaviruses (KIPyV, WUPyV and MCPyV) were identified in humans. So far KIPyV and WUPyV have not been associated to human diseases, while MCPyV was discovered in Merkel Cell carcinomas and may have neuroepithelial cell tropism. However, all three viruses can be potentially oncogenic and this compelled us to investigate for their presence in childhood CNS and neuroblastomas., Methodology: The presence of KI, WU and MCPyV DNA was analysed, by a joint WU and KI specific PCR (covering part of VP1) and by a MCPyV specific regular and real time quantitative PCR (covering part of Large T) in 25 CNS tumour biopsies and 31 neuroblastoma biopsies from the Karolinska University Hospital, Sweden. None of the three new human polyomaviruses were found to be associated with any of the tumours, despite the presence of PCR amplifiable DNA assayed by a S14 housekeeping gene PCR., Conclusion: In this pilot study, the presence of MCPyV, KI and WU was not observed in childhood CNS tumours and neuroblastomas. Nonetheless, we suggest that additional data are warranted in tumours of the central and peripheral nervous systems and we do not exclude that other still not yet detected polyomaviruses could be present in these tumours.

Merkel cell carcinoma (MCC) is a very aggressive neuroendocrine carcinoma of the skin. The recently identified Merkel cell polyomavirus (MCPyV) is present in the majority of MCCs. MCPyV clonally integrates in the tumor DNA and tumor-specific viral mutations are detected within the large T-antigen. To elucidate a possible role of MCPyV in the pathogenesis of other non-melanoma skin cancers (NMSC), i.e. squamous cell carcinoma, Bowen's disease and basal cell carcinoma we tested a group of these tumors in immunosuppressed and immunocompetent patients. In addition we tested MCPyV-positive tumors for viral mutations within the large T-antigen. MCPyV DNA was significantly more frequently detected in the NMSC of the immunosuppressed patients (p<0.001). No tumor specific mutations were found within the large T-antigen. The presence of the virus in tumor cells was confirmed by FISH analysis. Although MCPyV is present in the tumor cells of squamous cell carcinoma, Bowen's disease and basal cell skin carcinoma, further investigations into the role of MCPyV in the pathogenesis of these tumors is needed.

Merkel cell polyomavirus (MCV) is a recently discovered human polyomavirus causing the majority of human Merkel cell carcinomas. We mapped a 71-bp minimal MCV replication core origin sufficient for initiating eukaryotic DNA replication in the presence of wild-type MCV large T protein (LT). The origin includes a poly(T)-rich tract and eight variably oriented, GAGGC-like pentanucleotide sequences (PS) that serve as LT recognition sites. Mutation analysis shows that only four of the eight PS are required for origin replication. A single point mutation in one origin PS from a naturally occurring, tumor-derived virus reduces LT assembly on the origin and eliminates viral DNA replication. Tumor-derived LT having mutations truncating either the origin-binding domain or the helicase domain also prevent LT-origin assembly. Optimal MCV replication requires coexpression of MCV small T protein (sT), together with LT. An intact DnaJ domain on the LT is required for replication but is dispensable on the sT. In contrast, PP2A targeting by sT is required for enhanced replication. The MCV origin provides a novel model for eukaryotic replication from a defined DNA element and illustrates the selective pressure within tumors to abrogate independent MCV replication.

Background: Immunosuppression and Merkel-cell polyomavirus (MCPyV) infection may have a role in the pathogenesis of Merkel-cell carcinoma (MCC), a rare neuroendocrine carcinoma of the skin., Methods: We studied incidence of chronic lymphocytic leukaemia (CLL) and MCC from the files of the Finnish Cancer Registry and the largest hospital of Finland, Helsinki University Central Hospital, from 1979 to 2006. Presence of MCPyV DNA in MCCs was investigated by quantitative PCR., Results: We identified 4164 patients diagnosed with CLL and 172 diagnosed with MCC. Six patients diagnosed with both diseases were found; CLL was the first diagnosis in four cases and MCC in two. The standardised incidence ratio (SIR) for CLL after the diagnosis of MCC was highly elevated, 17.9 (95% confidence interval (CI), 2.2-64.6; P<0.001), and the SIR for MCC after the diagnosis of CLL was also elevated, 15.7 (3.2-46.0, P<0.01). Merkel-cell polyomavirus DNA was present in all five MCCs with tumour tissue available for analysis., Conclusions: We conclude that patients diagnosed with CLL have a substantially increased risk for MCC, and vice versa. Merkel-cell polyomavirus DNA is frequently present in MCCs that occur in CLL patients. Immunosuppression related with CLL and viral infection might explain the association between CLL and MCC.

Background: Merkel cell polyomavirus (MCPyV) was discovered recently. It is considered a potential causative agent of Merkel cell carcinoma, a life-threatening skin cancer., Objectives: To study the prevalence of MCPyV in a large number of clinical samples of various types. Most of the samples were examined also for the other newly found polyomaviruses KI (KIPyV) and WU (WUPyV)., Study Design: Altogether 1390 samples from immunocompetent or immunocompromised patients, including (i) tonsillar tissues and sera from tonsillectomy patients; (ii) nasopharyngeal aspirates (NPAs) and sera from wheezing children and (iii) nasal swabs, sera and stools from febrile leukemic children were studied for MCPyV. The tonsils, nasal swabs and stools were also studied for KIPyV and WUPyV., Results: MCPyV DNA was detected in 14 samples altogether; 8 of 229 (3.5%) tonsillar tissues, 3 of 140 (2.1%) NPAs, 2 of 106 (1.9%) nasal swabs and 1 of 840 (0.1%) sera. WUPyV and KIPyV were detected in 5 (2.2%) and 0 tonsils, 1 (0.9%) and 4 (3.8%) nasal swabs and 0 and 2 (2.7%) fecal samples, respectively. The patients carrying in tonsils MCPyV were of significantly higher age (median 42years) than those carrying WUPyV (4years, p<0.001)., Conclusions: MCPyV DNA occurs in tonsils more frequently in adults than in children. By contrast, WUPyV DNA is found preferentially in children. MCPyV occurs also in nasal swabs and NPAs, in a frequency similar to that of KIPyV and WUPyV. The tonsil may be an initial site of WUPyV infection and a site of MCPyV persistence.

A new polyomavirus, Merkel cell polyomavirus, was identified from Merkel cell carcinoma, a rare skin cancer. Origin of Merkel cell carcinoma is Merkel cell, a neuroendocrine cell in the skin. Merkel cell carcinoma occurs in the skin of head and face of white elders. Like other polyomaviruses, a 5.4 kbp-virus genome encodes VP1, VP2, VP3, small T antigen, and large T (LT) antigen. MCV has been frequently detected in Merkel cell carcinoma in the world by PCR. It was demonstrated that MCV genome integrated into the host genome of Merkel cell carcinoma. LT plays an important role in replication of a circular MCV. However, mutations with stop codons were identified in the LT genes derived from Merkel cell carcinoma cases. Such mutations cause a truncation of the LT gene, resulting in defect of LTs helicase activity and in induction of Rb binding function in the LT. MCV is a new member of human oncovirus belonging to the human polyomavirus.

We investigated whether Merkel cell carcinoma (MCC) patients in France carry Merkel cell polyomavirus (MCPyV) and then identified strain variations. All frozen MCC specimens and 45% of formalin-fixed and paraffin-embedded specimens, but none of the non-MCC neuroendocrine carcinomas specimens, had MCPyV. Strains from France and the United States were similar.

Merkel cell carcinoma (MCC), a skin tumour with neuroendocrine features, was recently found to be associated with a new type of human polyomavirus, called Merkel cell virus (MCV). We investigated the specificity of this association as well as a causal role of MCV in oncogenesis. DNA and RNA from ten cases of MCC were analysed using PCR and RT-PCR. DNA from 1241 specimens of a wide range of human tumours was also analysed. The DIPS technique was used to identify the integration locus of viral DNA sequences. Array CGH was performed to analyse structural alterations of the cell genome. MCV DNA sequences were found in all ten cases of MCC and in none of the 1241 specimens of other tumour types. Clonal integration of MCV into the host genome was seen in all MCC cases and was checked by FISH in one case. A recurrent pattern of conserved viral sequences which encompassed the replication origin, the small tumour (ST), and the 5' part of the large tumour (LT) antigen DNA sequences was observed. Both ST and LT viral sequences were found to be significantly expressed in all MCCs. Neither recurrent site of integration nor alteration of cellular genes located near the viral sequences was observed. The tight association of MCV with MCC, the clonal pattern of MCV integration, and the expression of the viral oncoproteins strongly support a causative role for MCV in the tumour process. This information will help the development of novel approaches for the assessment and therapy of MCC and biologically related tumours.

Merkel cell polyomavirus (MCPyV), associated with Merkel cell carcinoma, was detected in 27 of 635 nasopharyngeal aspirate samples by real-time PCR. MCPyV was more commonly found in adults than in children. Presence in the upper respiratory tract may be a general property of human PyVs.

microRNAs (miRNAs) are post-transcriptional regulators of gene expression that play a role in viral infection. We have developed a method to identify viral-encoded miRNAs from viruses in which abundant amounts of infected material is limiting. We show that Merkel Cell Polyomavirus (MCV), a recently identified human virus associated with cancer, encodes a miRNA. This miRNA is expressed from the late strand, lies antisense to the early transcripts and negatively regulates expression of chimeric reporters containing a portion of the early transcripts. Interestingly, different viral isolates have sequence polymorphisms in the pre-miRNA region that result in amino acids substitutions but fully preserve the processing and activity of the miRNAs.

Merkel cell carcinoma (MCC) is a rare but very aggressive human malignancy of the elderly or immunosuppressed patients. Recently, the clonal integration of a new human polyoma virus, which was termed Merkel cell polyomavirus (MCPyV), has been reported in 8 of 10 MCC patients. In the present study, we studied the formalin-fixed and paraffin-embedded tissue specimens of 39 MCC for the presence of MCPyV by PCR. We applied four different primer sets directed against the large T antigen and the VP1 gene of MCPyV. We were able to detect MCPyV in 77% (n = 30) of MCC as confirmed by sequence analyses of the PCR products. Sequence analyses showed only minor nucleotide changes compared with the previously published MCC sequences. In addition, one patient revealed the amplification of two PCR products using PCR primers directed against the VP1 gene. Sequence analyses confirmed the presence of the expected 351-bp PCR product and in addition a second PCR product of 261 bp containing a unique 90-bp deletion in the VP1 gene, which will lead to a predicted loss of 28 amino acids. The unique 90-bp deletion within the VP1 gene possibly is a result of incomplete viral integration of MCPyV in the MCC. The presence of MCPyV in the majority of MCC tissue specimens in our study strongly underlines a possible role for MCPyV as an etiologic agent in the carcinogenesis of MCC.