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The nuclear lamina is a dense network of intermediate filaments beneath the inner nuclear membrane. Composed of A-type lamins (lamin A/C) and B-type lamins (lamins B1 and B2), the nuclear lamina provides a scaffold for the nuclear envelope and chromatin, thereby maintaining the structural integrity of the nucleus. A-type lamins are also found inside the nucleus where they interact with chromatin and participate in gene regulation. Viruses replicating in the cell nucleus have to overcome the nuclear envelope during the initial phase of infection and during the nuclear egress of viral progeny. Here, we focused on the role of lamins in the replication cycle of a dsDNA virus, mouse polyomavirus. We detected accumulation of the major capsid protein VP1 at the nuclear periphery, defects in nuclear lamina staining and different lamin A/C phosphorylation patterns in the late phase of mouse polyomavirus infection, but the nuclear envelope remained intact. An absence of lamin A/C did not affect the formation of replication complexes but did slow virus propagation. Based on our findings, we propose that the nuclear lamina is a scaffold for replication complex formation and that lamin A/C has a crucial role in the early phases of infection with mouse polyomavirus., (© 2024 The Author(s). The FEBS Journal published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

It has been reported that polyomaviruses are the microbes which can be a cause of several human pathological conditions including cancers, nephropathy, progressive multifocal leukoencephalopathy and gynaecological disease. Although investigators proposed some mechanisms used by the viruses to induce the disorders, the roles played by chemokines in the pathogenesis of polyomaviruses infections are yet to be clarified. This review article investigated recent studies regarding the roles played by chemokines in the pathogenesis of the polyomaviruses infections. The research in the literature revealed that CXC chemokines, including CXCL1, CXCL5, CXCL8, CXCL9, CXCL10, CXCL11, CXCL12 and CXCL16, significantly participate in the pathogenesis of polyomaviruses. CC chemokines, such as CCL2, CCL5 and CCL20 also participate in the induction of the pathological conditions. Therefore, it appears that CXC chemokines may be considered as the strategic factors involved in the pathogenesis of polyomaviruses.

Lyon IARC polyomavirus (LIPyV), a newly discovered polyomavirus (PyV), was first identified in 2017 in human skin samples in the USA. Later, it was detected in several other countries in samples of human and feline origin. Our aim was to find out if the virus occurs in China. To this end, 100 fecal samples were collected from cats with diarrhea in Guangxi Province during 2016 and 2018 and tested with polymerase chain reaction (PCR). Only 2 samples that originated from two related individuals were found to be positive. Based on the sequence identity of the 240-bp PCR products, the two positive samples supposedly contained identical viruses. Therefore, only one of them, which was designated as LIPyV-GXNN01, was selected for full genome amplification, cloning, sequencing and analysis. LIPyV-GXNN01, which comprises 5,263 nucleotides, has an early region that consists of small T antigen (ST-Ag) and large T antigen (LT-Ag) and a late region coding for the VP1, VP2, and VP3 structural proteins. Moreover, the LIPyV-GXNN01 strain structural proteins share 95.9-99.4%, 97.6-99.2%, and 97.1-99.2% nucleic acid identity with the VP1, VP2, and VP3of other LIPyV reference strains, respectively. A phylogenetic analysis revealed that GXNN01 clustered together with previously reported LIPyV strain. This present study is the first report of LIPyV in China.

Herpes-Simplex Virus 1 (HSV-1) infects most humans when they are young, sometimes with fatal consequences. Gene expression occurs in a temporal order upon lytic HSV-1 infection: immediate early (IE) genes are expressed, then early (E) genes, followed by late (L) genes. During this infection cycle, the HSV-1 genome has the potential for exposure to APOBEC3 (A3) proteins, a family of cytidine deaminases that cause C>U mutations on single-stranded DNA (ssDNA), often resulting in a C>T transition. We developed a computational model for the mutational pressure of A3 on the lytic cycle of HSV-1 to determine which viral kinetic gene class is most vulnerable to A3 mutations. Using in silico stochastic methods, we simulated the infectious cycle under varying intensities of A3 mutational pressure. We found that the IE and E genes are more vulnerable to A3 than L genes. We validated this model by analyzing the A3 evolutionary footprints in 25 HSV-1 isolates. We find that IE and E genes have evolved to underrepresent A3 hotspot motifs more so than L genes, consistent with greater selection pressure on IE and E genes. We extend this model to two-step infections, such as those of polyomavirus, and find that the same pattern holds for over 25 human Polyomavirus (HPyVs) genomes. Genes expressed earlier during infection are more vulnerable to mutations than those expressed later., Competing Interests: The authors have declared that no competing interests exist.

Members of the Polyomaviridae family differ in their host range, pathogenesis, and disease severity. To date, some of the most studied polyomaviruses include human JC, BK, and Merkel cell polyomavirus and non-human subspecies murine and simian virus 40 (SV40) polyomavirus. Although dichotomies in host range and pathogenesis exist, overlapping features of the infectious cycle illuminate the similarities within this virus family. Of particular interest to human health, JC, BK, and Merkel cell polyomavirus have all been linked to critical, often fatal, illnesses, emphasizing the importance of understanding the underlying viral infections that result in the onset of these diseases. As there are significant overlaps in the capacity of polyomaviruses to cause disease in their respective hosts, recent advancements in characterizing the infectious life cycle of non-human murine and SV40 polyomaviruses are key to understanding diseases caused by their human counterparts. This review focuses on the molecular mechanisms by which different polyomaviruses hijack cellular processes to attach to host cells, internalize, traffic within the cytoplasm, and disassemble within the endoplasmic reticulum (ER), prior to delivery to the nucleus for viral replication. Unraveling the fundamental processes that facilitate polyomavirus infection provides deeper insight into the conserved mechanisms of the infectious process shared within this virus family, while also highlighting critical unique viral features.

JCPyV polyomavirus, a member of the human virome, causes progressive multifocal leukoencephalopathy (PML), an oft-fatal demyelinating brain disease in individuals receiving immunomodulatory therapies. Mutations in the major viral capsid protein, VP1, are common in JCPyV from PML patients (JCPyV-PML) but whether they confer neurovirulence or escape from virus-neutralizing antibody (nAb) in vivo is unknown. A mouse polyomavirus (MuPyV) with a sequence-equivalent JCPyV-PML VP1 mutation replicated poorly in the kidney, a major reservoir for JCPyV persistence, but retained the CNS infectivity, cell tropism, and neuropathology of the parental virus. This mutation rendered MuPyV resistant to a monoclonal Ab (mAb), whose specificity overlapped the endogenous anti-VP1 response. Using cryo-EM and a custom sub-particle refinement approach, we resolved an MuPyV:Fab complex map to 3.2 Å resolution. The structure revealed the mechanism of mAb evasion. Our findings demonstrate convergence between nAb evasion and CNS neurovirulence in vivo by a frequent JCPyV-PML VP1 mutation., Competing Interests: ML, DG, CN, KA, GJ, DH, EF, SC, CB, SB, NC, SH, AL No competing interests declared, (© 2020, Lauver et al.)

The question of whether some cases of interstitial cystitis may have an infectious etiology has been debated for some time. Previous studies have looked for the presence of certain specific viruses, but generally did not use the types of sensitive and unbiased approaches that are currently available. As part of the MAPP (Multidisciplinary Approach to the Study of Chronic Pelvic Pain) Research Network, we examined urine specimens from interstitial cystitis patients who provided specimens over time and also reported various symptoms at the time of urine collection. We first performed next-generation sequencing to look for the presence of viruses in urines, and detected two human polyomaviruses that are known to be excreted into urine, BKPyV and JCPyV. We were especially interested in BKPyV because it is a known cause of another bladder disease, hemorrhagic cystitis, in bone marrow transplant recipients. Further analysis of individual samples indicates a trend toward higher excretion of polyomaviruses in patients experiencing increased symptoms.

During entry, viruses must navigate through the host endomembrane system, penetrate cellular membranes, and undergo capsid disassembly to reach an intracellular destination that supports infection. How these events are coordinated is unclear. Here, we reveal an unexpected function of a cellular motor adaptor that coordinates virus membrane penetration and disassembly. Polyomavirus SV40 traffics to the endoplasmic reticulum (ER) and penetrates a virus-induced structure in the ER membrane called "focus" to reach the cytosol, where it disassembles before nuclear entry to promote infection. We now demonstrate that the ER focus is constructed proximal to the Golgi-associated BICD2 and BICDR1 dynein motor adaptors; this juxtaposition enables the adaptors to directly bind to and disassemble SV40 upon arrival to the cytosol. Our findings demonstrate that positioning of the virus membrane penetration site couples two decisive infection events, cytosol arrival and disassembly, and suggest cargo remodeling as a novel function of dynein adaptors., (© 2020 Spriggs et al.)

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., Competing Interests: Declaration of Competing Interest None., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Trichodysplasia spinulosa-associated polyomavirus (TSPyV or human polyomavirus 8) was identified from patients with trichodysplasia spinulosa, a rare skin disease affecting the faces of immunocompromised patients. Like other polyomaviruses, the TSPyV genome encodes a large T antigen (LT). However, the expression and functions of TSPyV LT in infected cells remain largely unknown. In the present study, we cloned a full-length TSPyV LT cDNA from cells transfected with the full-length of TSPyV LT DNA. Transfection study using green fluorescence protein-tagged LT expression plasmids showed that TSPyV LT was expressed in the nucleus of transfected cells. Analysis of deletion mutants identified a nuclear localization signal in TSPyV LT. Recombinant TSPyV LT exhibited an ATPase activity. TSPyV LT has a chitinase-like domain; however, no chitinase activity was detected. Immunoprecipitation assays revealed that TSPyV LT bound to retinoblastoma 1, but not to p53 in transfected cells. Expression of TSPyV LT in NIH3T3 cells induced colony formation in soft agar, suggesting its transformation activity. These data indicate that TSPyV LT may be associated with the pathogenesis of trichodysplasia spinulosa, which is a hyperplasia of keratinocytes in inner hair follicles.

Background: Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine carcinoma of the skin caused by either the integration of Merkel cell polyomavirus (MCPyV) and expression of viral T antigens or by ultraviolet-induced damage to the tumor genome from excessive sunlight exposure. An increasing number of deep sequencing studies of MCC have identified significant differences between the number and types of point mutations, copy number alterations, and structural variants between virus-positive and virus-negative tumors. However, it has been challenging to reliably distinguish between virus positive and UV damaged MCC., Methods: In this study, we assembled a cohort of 71 MCC patients and performed deep sequencing with OncoPanel, a clinically implemented, next-generation sequencing assay targeting over 400 cancer-associated genes. To improve the accuracy and sensitivity for virus detection compared to traditional PCR and IHC methods, we developed a hybrid capture baitset against the entire MCPyV genome and software to detect integration sites and structure., Results: Sequencing from this approach revealed distinct integration junctions in the tumor genome and generated assemblies that strongly support a model of microhomology-initiated hybrid, virus-host, circular DNA intermediate that promotes focal amplification of host and viral DNA. Using the clear delineation between virus-positive and virus-negative tumors from this method, we identified recurrent somatic alterations common across MCC and alterations specific to each class of tumor, associated with differences in overall survival. Finally, comparing the molecular and clinical data from these patients revealed a surprising association of immunosuppression with virus-negative MCC and significantly shortened overall survival., Conclusions: These results demonstrate the value of high-confidence virus detection for identifying molecular mechanisms of UV and viral oncogenesis in MCC. Furthermore, integrating these data with clinical data revealed features that could impact patient outcome and improve our understanding of MCC risk factors.

Microtubules, part of the cytoskeleton, are indispensable for intracellular movement, cell division, and maintaining cell shape and polarity. In addition, microtubules play an important role in viral infection. In this review, we summarize the role of the microtubules' network during polyomavirus infection. Polyomaviruses usurp microtubules and their motors to travel via early and late acidic endosomes to the endoplasmic reticulum. As shown for SV40, kinesin-1 and microtubules are engaged in the release of partially disassembled virus from the endoplasmic reticulum to the cytosol, and dynein apparently assists in the further disassembly of virions prior to their translocation to the cell nucleus-the place of their replication. Polyomavirus gene products affect the regulation of microtubule dynamics. Early T antigens destabilize microtubules and cause aberrant mitosis. The role of these activities in tumorigenesis has been documented . However, its importance for productive infection remains elusive. On the other hand, in the late phase of infection, the major capsid protein, VP1, of the mouse polyomavirus, counteracts T-antigen-induced destabilization. It physically binds microtubules and stabilizes them. The interaction results in the G2/M block of the cell cycle and prolonged S phase, which is apparently required for successful completion of the viral replication cycle., Competing Interests: The authors declare no conflict of interest.

Gliomas are tumors that originate from the glial tissue, thus involving the central nervous system with varying degrees of malignancy. The most aggressive and frequent form is glioblastoma multiforme, a disease characterized by resistance to therapies, frequent recurrences, and extremely poor median survival time. Data on overall glioma case studies demonstrate clear sex disparities regarding incidence, prognosis, drug toxicity, clinical outcome, and, recently, prediction of therapeutic response. In this study, we analyze data in the literature regarding malignant glioma, mainly glioblastoma multiforme, focusing on epidemiological and clinical evaluations. Less discussed issues, such as the role of viral infections, energy metabolism, and predictive aspects concerning the possible use of dedicated therapeutic approaches for male or female patients, will be reported together with different estimated pathogenetic mechanisms underlying astrocyte transformation and glioma chemosensitivity. In this era, where personalized/precision medicine is the most important driver for targeted cancer therapies, the lines of evidence discussed herein strongly suggest that clinical approaches to malignant glioma should consider the patient's sex. Furthermore, retrospectively revising previous clinical studies considering patient sex as a crucial variable is recommended., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: Human polyomaviruses (HPyVs), like herpesviruses, cause persistent infection in a large part of the population. In immunocompromised and elderly patients, PyVs cause severe diseases such as nephropathy (BK polyomavirus [BKPyV]), progressive multifocal leukoencephalopathy (JC polyomavirus [JCPyV]), and skin cancer (Merkel cell polyomavirus [MCPyV]). Like cytomegalovirus, donor-derived PyV can cause disease in kidney transplant recipients. Possibly blood components transmit PyVs as well. To study this possibility, as a first step we determined the presence of PyV DNA in Dutch blood donations., Study Design and Methods: Blood donor serum samples (n = 1016) were analyzed for the presence of DNA of 14 HPyVs using HPyV species-specific quantitative polymerase chain reaction (PCR) procedures. PCR-positive samples were subjected to confirmation by sequencing. Individual PCR findings were compared with the previously reported PyV serostatus., Results: MC polyomavirus DNA was detected in 39 donors (3.8%), JCPyV and TS polyomavirus (TSPyV) DNA in five donors (both 0.5%), and HPyV9 DNA in four donors (0.4%). BKPyV, WU polyomavirus (WUPyV), HPyV6, MW polyomavirus (MWPyV), and LI polyomavirus (LIPyV) DNA was detected in one or two donors. Amplicon sequencing confirmed the expected product for BKPyV, JCPyV, WUPyV, MCPyV, HPyV6, TSPyV, MWPyV, HPyV9, and LIPyV. For JCPyV a significant association was observed between detection of viral DNA and the level of specific IgG antibodies., Conclusion: In 5.4% of Dutch blood donors PyV DNA was detected, including DNA from pathogenic PyVs such as JCPyV. As a next step, the infectivity of PyV in donor blood and transmission via blood components to immunocompromised recipients should be investigated., (© 2019 The Authors. Transfusion published by Wiley Periodicals, Inc. on behalf of AABB.)

Polyomavirus family consists of a highly diverse group of small DNA viruses. The founding family member (MPyV) was first discovered in the newborn mouse in the late 1950s, which induces solid tumors in a wide variety of tissue types that are the epithelial and mesenchymal origin. Later, other family members were also isolated from a number of mammalian, avian and fish species. Some of these viruses significantly contributed to our current understanding of the fundamentals of modern biology such as transcription, replication, splicing, RNA editing, and cell transformation. After the discovery of first two human polyomaviruses (JC virus [JCV] and BK virus [BKV]) in the early 1970s, there has been a rapid expansion in the number of human polyomaviruses in recent years due to the availability of the new technologies and brought the present number to 14. Some of the human polyomaviruses cause considerably serious human diseases, including progressive multifocal leukoencephalopathy, polyomavirus-associated nephropathy, Merkel cell carcinoma, and trichodysplasia spinulosa. Emerging evidence suggests that the expression of the polyomavirus genome is more complex than previously thought. In addition to encoding universally expressed regulatory and structural proteins (LT-Ag, Sm t-Ag, VP1, VP2, and VP3), some polyomaviruses express additional virus-specific regulatory proteins and microRNAs. This review summarizes the recent advances in polyomavirus genome expression with respect to the new viral proteins and microRNAs other than the universally expressed ones. In addition, a special emphasis is devoted to the recent structural and functional discoveries in the field of polyomavirus agnoprotein which is expressed only by JCV, BKV, and simian virus 40 genomes., (© 2018 Wiley Periodicals, Inc.)

Background: Acute T-cell mediated rejection (TCMR) is usually indicated by alteration in serum-creatinine measurements when considerable transplant damage has already occurred. There is, therefore, a need for non-invasive early detection of immune signals that would precede the onset of rejection, prior to transplant damage., Methods: We examined the RT-qPCR expression of 22 literature-based genes in peripheral blood samples from 248 patients in the Kidney Allograft Immune Biomarkers of Rejection Episodes (KALIBRE) study. To account for post-transplantation changes unrelated to rejection, we generated time-adjusted gene-expression residuals from linear mixed-effects models in stable patients. To select genes, we used penalised logistic regression based on 27 stable patients and 27 rejectors with biopsy-proven T-cell-mediated rejection, fulfilling strict inclusion/exclusion criteria. We validated this signature in i) an independent group of stable patients and patients with concomitant T-cell and antibody-mediated-rejection, ii) patients from an independent study, iii) cross-sectional pre-biopsy samples from non-rejectors and iv) longitudinal follow-up samples covering the first post-transplant year from rejectors, non-rejectors and stable patients., Findings: A parsimonious TCMR-signature (IFNG, IP-10, ITGA4, MARCH8, RORc, SEMA7A, WDR40A) showed cross-validated area-under-ROC curve 0.84 (0.77-0.88) (median, 2.5 th -97.5 th centile of fifty cross-validation cycles), sensitivity 0.67 (0.59-0.74) and specificity 0.85 (0.75-0.89). The estimated probability of TCMR increased seven weeks prior to the diagnostic biopsy and decreased after treatment. Gene expression in all patients showed pronounced variability, with up to 24% of the longitudinal samples in stable patients being TCMR-signature positive. In patients with borderline changes, up to 40% of pre-biopsy samples were TCMR-signature positive., Interpretation: Molecular marker alterations in blood emerge well ahead of the time of clinically overt TCMR. Monitoring a TCMR-signature in peripheral blood could unravel T-cell-related pro-inflammatory activity and hidden immunological processes. This additional information could support clinical management decisions in cases of patients with stable but poor kidney function or with inconclusive biopsy results., (Copyright © 2019. Published by Elsevier B.V.)

Merkel cell carcinoma (MCC) is a rare and aggressive skin cancer associated with advanced age and immunosuppression. Over the past decade, an association has been discovered between MCC and either integration of the Merkel cell polyomavirus, which likely drives tumorigenesis, or somatic mutations owing to ultraviolet-induced DNA damage. Both virus-positive and virus-negative MCCs are immunogenic, and inhibition of the programmed cell death protein 1 (PD-1)-programmed cell death 1 ligand 1 (PD-L1) immune checkpoint has proved to be highly effective in treating patients with metastatic MCC; however, not all patients have a durable response to immunotherapy. Despite these rapid advances in the understanding and management of patients with MCC, many basic, translational and clinical research questions remain unanswered. In March 2018, an International Workshop on Merkel Cell Carcinoma Research was held at the US National Cancer Institute, at which academic, government and industry experts met to identify the highest-priority research questions. Here, we review the biology and treatment of MCC and report the consensus-based recommendations agreed upon during the workshop.

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.

Background: WU polyomavirus (WUPyV) is a relatively new virus associated with respiratory infections. However, its role is unclear in children with severe respiratory failure., Objectives: We aimed to evaluate the characteristics of severe respiratory failure associated with WUPyV infection in children., Study Design: We retrospectively reviewed cases of respiratory tract infection at a tertiary children's hospital in Japan and performed real-time polymerase chain reaction (PCR) for WUPyV using residual extracted nucleic acid samples taken from respiratory tract samples of pediatric patients primarily with respiratory failure. We investigated the clinical characteristics of patients positive for WUPyV and assessed samples positive for WUPyV for other respiratory pathogens using multiplex PCR., Results: WUPyV was detected in 14 of 318 specimens of respiratory tract infections. The median age was 34 months and males were predominant (n = 11, 64%). An underlying disease was found in 11 (79%) patients including five preterm and three immunocompromised patients. The most common clinical diagnosis was pneumonia (n = 13, 93%). The majority of the samples were endotracheal tube aspirates (n = 11, 79%). Other viruses were co-detected in nine (64%) patients, while WUPyV was the only pathogen detected in five patients with a history of admission to the neonatal intensive care unit. These five patients presented with fever and cough, and perihilar infiltrates were detected on chest radiograph in several days., Conclusions: WUPyV was detected in children with severe respiratory failure independently or concurrently with other pathogens. WUPyV can be a pathogen for children with a history of preterm birth or an underlying disease., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The ShcA adaptor protein transduces oncogenic signals downstream of receptor tyrosine kinases. We show here that breast tumors engage the ShcA pathway to increase their metabolism. ShcA signaling enhanced glucose catabolism through glycolysis and oxidative phosphorylation, rendering breast cancer cells critically dependent on glucose. ShcA signaling simultaneously increased the metabolic rate and flexibility of breast cancer cells by inducing the PGC-1α transcriptional coactivator, a central regulator of mitochondrial metabolism. Breast tumors that engaged ShcA signaling were critically dependent on PGC-1α to support their increased metabolic rate. PGC-1α deletion drastically delayed breast tumor onset in an orthotopic mouse model, highlighting a key role for PGC-1α in tumor initiation. Conversely, reduced ShcA signaling impaired both the metabolic rate and flexibility of breast cancer cells, rendering them reliant on mitochondrial oxidative phosphorylation. This metabolic reprogramming exposed a targetable metabolic vulnerability, leading to a sensitization of breast tumors to inhibitors of mitochondrial complex I (biguanides). Genetic inhibition of ShcA signaling in the Polyoma virus middle T (MT) breast cancer mouse model sensitized mammary tumors to biguanides during the earliest stages of breast cancer progression. Tumor initiation and growth were selectively and severely impaired in MT/ShcA-deficient animals. These data demonstrate that metabolic reprogramming is a key component of ShcA signaling and serves an unappreciated yet vital role during breast cancer initiation and progression. These data further unravel a novel interplay between ShcA and PGC-1α in the coordination of metabolic reprogramming and demonstrate the sensitivity of breast tumors to drugs targeting oxidative phosphorylation. Significance: This study uncovers a previously unrecognized mechanism that links aberrant RTK signaling with metabolic perturbations in breast cancer and exposes metabolic vulnerabilities that can be targeted by inhibitors of oxidative phosphorylation. Cancer Res; 78(17); 4826-38. ©2018 AACR ., (©2018 American Association for Cancer Research.)

MicroRNAs (miRNAs) are small, non-coding RNAs that regulate gene expression at the post-transcriptional level. Through this activity, they are implicated in almost every cellular process investigated to date. Hence, it is not surprising that miRNAs play diverse roles in regulation of viral infections and antiviral responses. Diverse families of DNA and RNA viruses have been shown to take advantage of cellular miRNAs or produce virally encoded miRNAs that alter host or viral gene expression. MiRNA-mediated changes in gene expression have been demonstrated to modulate viral replication, antiviral immune responses, viral latency, and pathogenesis. Interestingly, viruses mediate both canonical and non-canonical interactions with miRNAs to downregulate specific targets or to promote viral genome stability, translation, and/or RNA accumulation. In this review, we focus on recent findings elucidating several key mechanisms employed by diverse virus families, with a focus on miRNAs at the host⁻virus interface during herpesvirus, polyomavirus, retroviruses, pestivirus, and hepacivirus infections.

Polyomaviruses (PyVs) can cause serious disease in immunosuppressed hosts. Several pathogenic PyVs encode microRNAs (miRNAs), small RNAs that regulate gene expression via RNA silencing. Despite recent advances in understanding the activities of PyV miRNAs, the biological functions of PyV miRNAs during in vivo infections are mostly unknown. The studies presented here used murine polyomavirus (MuPyV) as a model to assess the roles of the PyV miRNAs in a natural host. This analysis revealed that a MuPyV mutant that is unable to express miRNAs has enhanced viral DNA loads in select tissues at late times after infection. This is consistent with the PyV miRNAs functioning to reduce viral replication during the persistent phase of infection in a natural host. Additionally, the MuPyV miRNA locus promotes viruria during the acute phase of infection as evidenced by a defect in shedding during infection with the miRNA mutant virus. The viruria defect of the miRNA mutant virus could be rescued by infecting Rag2 -/- mice. These findings implicate the miRNA locus as functioning in both the persistent and acute phases of infection and suggest a role for MuPyV miRNA in evading the adaptive immune response. IMPORTANCE MicroRNAs are expressed by diverse viruses, but for only a few is there any understanding of their in vivo function. PyVs can cause serious disease in immunocompromised hosts. Therefore, increased knowledge of how these viruses interact with the immune response is of clinical relevance. Here we show a novel activity for a viral miRNA locus in promoting virus shedding. This work indicates that in addition to any role for the PyV miRNA locus in long-term persistence, it also has biological activity during the acute phase. As this mutant phenotype is alleviated by infection of mice lacking an adaptive immune response, our work also connects the in vivo activity of the PyV miRNA locus to the immune response. Given that PyV-associated disease is associated with alterations in the immune response, our findings help to better understand how the balance between PyVs and the immune response becomes altered in pathogenic states., (Copyright © 2018 American Society for Microbiology.)

Although the human neurotropic polyomavirus, JC virus (JCV), was isolated almost a half century ago, understanding the molecular mechanisms governing its biology remains highly elusive. JCV infects oligodendrocytes and astrocytes in the central nervous system (CNS) and causes a rare fatal brain disease known as progressive multifocal leukoencephalopathy (PML) in immunocompromised individuals including AIDS. It has a small circular DNA genome (∼5 kb) and generates two primary transcripts from its early and late coding regions, producing several predicted alternatively spliced products mainly by cis-splicing. Here, we report the discovery and characterization of two novel open reading frames (ORF1 and ORF2) associated with JCV late transcripts, generated by an unusual splicing process called trans-splicing. These ORFs result from (i) the trans-splicing of two different lengths of the 5'-short coding region of VP1 between the coding regions of agnoprotein and VP2 after replacing the intron located between these two coding regions and (ii) frame-shifts occurring within the VP2 coding sequences terminated by a stop codon. ORF1 and ORF2 are capable of encoding 58 and 72 aa long proteins respectively and are expressed in infected cells and PML patients. Each ORF protein shares a common coding region with VP1 and has a unique coding sequence of their own. When the expression of the unique coding regions of ORFs is blocked by a stop codon insertion in the viral background, the mutant virus replicates less efficiently when compared to wild-type, suggesting that the newly discovered ORFs play critical roles in the JCV life cycle., (© 2017 Wiley Periodicals, Inc.)

Rapid restoration of virus-specific T immunity via adoptive transfer of ex vivo generated T cells has been proven as a powerful therapy for patients with advanced cancers and refractory viral infections such as cytomegalovirus (CMV) and Epstein-Barr virus (EBV). BK virus (BKV), John Cunningham virus (JCV), and Merkel cell carcinoma virus (MCV) are the members of the rapidly growing human polyomavirus (hPyV) family that commonly infects most healthy humans. These viruses have a clearly established potential for causing severe end-organ damage or malignant transformation, especially in individuals with weakened immunity who are unable to mount or regain endogenous T-cell responses as a result of underlying leukemia or iatrogenic immunosuppression in autoimmunity, bone marrow and solid organ transplant settings. Here we will discuss recent advances in using T-cell-based immunotherapies to save patients suffering from PyV-associated diseases including hemorrhagic cystitis, BKV virus-associated nephropathy, and JC-associated progressive multifocal leukoencephalopathy (PML). We will also review progress in the understanding of Merkel cell carcinoma (MCC) as a virally driven tumor that is amenable to immune intervention and can be targeted with adoptively transferred T cells specific for viral oncoproteins., (Copyright © 2017. Published by Elsevier Inc.)

Forty-six years after the identification of the first polyomaviruses in humans (PyV) still there are strong concerns to find new types related to pathologies of different organs in immunocompromised patients. At the time of this review, 15 PyV have been described, many of them without being clearly associated with diseases. In our country, as in much of South America, the knowledge and research of these infectious agents are insufficient, so we systematized what is known about these viruses and their relationship with different human systems with emphasis on immunocompromised and we pointed out data published in our continent. Thus, we hope to encourage the study of these infections.

In 1971, the first human polyomavirus was isolated from the brain of a patient who died from a rapidly progressing demyelinating disease known as progressive multifocal leukoencephalopathy. The virus was named JC virus after the initials of the patient. In that same year a second human polyomavirus was discovered in the urine of a kidney transplant patient and named BK virus. In the intervening years it became clear that both viruses were widespread in the human population but only rarely caused disease. The past decade has witnessed the discovery of eleven new human polyomaviruses, two of which cause unusual and rare cancers. We present an overview of the history of these viruses and the evolution of JC polyomavirus-induced progressive multifocal leukoencephalopathy over three different epochs. We review what is currently known about JC polyomavirus, what is suspected, and what remains to be done to understand the biology of how this mostly harmless endemic virus gives rise to lethal disease.

Background: The etiology of acute childhood diarrhea often eludes identification. We used a case-control study-stool archive to determine if nucleic acid tests for established and newly identified viruses diminish our previously published 32% rate of microbiologically unexplained episodes., Methods: Using polymerase chain reaction, we sought to detect noroviruses GI and GII, classic and novel astroviruses, and human bocaviruses (HBoVs) 2, 3, and 4 among 178 case and 178 matched control stool samples and St. Louis and Malawi polyomaviruses among a subset of 98 case and control stool samples. We calculated adjusted odds ratios and 95% confidence intervals using conditional logistic regression., Results: Noroviruses were more common in cases (GI, 2.2%; GII, 16.9%) than in controls (GI, 0%; GII, 4.5%) (adjusted odds ratio, 5.2 [95% confidence interval, 2.5-11.3]). Astroviruses and HBoVs 2, 3, and 4 were overrepresented among the cases, although this difference was not statistically significant. Malawi polyomavirus was not associated with case status, and St. Louis polyomavirus was identified in only 1 subject (a control). When identified in cases, HBoVs 2, 3, and 4 were frequently (77%) found in conjunction with a bona fide diarrheagenic pathogen. Thirty-five (20%) case and 3 (2%) control stool samples contained more than 1 organism of interest. Overall, a bona fide or plausible pathogen was identified in 79% of the case stool samples. Preceding antibiotic use was more common among cases (adjusted odds ratio, 4.5 [95% confidence interval, 2.3-8.5])., Conclusion: Noroviruses were found to cause one-third of the diarrhea cases that previously had no identified etiology. Future work should attempt to ascertain etiologic agents in the approximately one-fifth of cases without a plausible microbial cause, understand the significance of multiple agents in stools, and guide interpretation of nonculture diagnostics., (© The Author 2017. Published by the Oxford University Press on behalf of The Journal of the Pediatric Infectious Diseases Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

We report the identification, pathogenesis, and transmission of a novel polyomavirus in severe combined immunodeficient F344 rats with null Prkdc and interleukin 2 receptor gamma genes. Infected rats experienced weight loss, decreased fecundity, and mortality. Large basophilic intranuclear inclusions were observed in epithelium of the respiratory tract, salivary and lacrimal glands, uterus, and prostate gland. Unbiased viral metagenomic sequencing of lesioned tissues identified a novel polyomavirus, provisionally named Rattus norvegicus polyomavirus 2 (RatPyV2), which clustered with Washington University (WU) polyomavirus in the Wuki clade of the Betapolyomavirus genus. In situ hybridization analyses and quantitative polymerase chain reaction (PCR) results demonstrated viral nucleic acids in epithelium of respiratory, glandular, and reproductive tissues. Polyomaviral disease was reproduced in Foxn1 rnu nude rats cohoused with infected rats or experimentally inoculated with virus. After development of RatPyV2-specific diagnostic assays, a survey of immune-competent rats from North American research institutions revealed detection of RatPyV2 in 7 of 1,000 fecal samples by PCR and anti-RatPyV2 antibodies in 480 of 1,500 serum samples. These findings suggest widespread infection in laboratory rat populations, which may have profound implications for established models of respiratory injury. Additionally, RatPyV2 infection studies may provide an important system to investigate the pathogenesis of WU polyomavirus diseases of man.

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., (© 2016 Wiley Periodicals, Inc.)

Aim: Тo compare morphological changes and results of immunohistochemical (IHC) identification of viruses (polyomaviruses, adenoviruses, and herpesviruses) in the biopsy specimens with their clinical manifestations in recipients of renal transplants., Material and Methods: Morphological and IHC studies were conducted using 71 needle renal transplant biopsy specimens from patients in the study group and 10 renal biopsy specimens from those in the control group. A number of clinical indicators were estimated., Results: IHC examination revealed the expression of adenoviral antigens more commonly in patients with posttransplant nephritis than in recipients without nephritis or in control individuals (p<0.05). The association of patient age and time after kidney transplantation with the severity of viral damage was confirmed: graft loss in children occurred within the first months of surgery (p<0.05). Polyomavirus was detected by PCR in patients with the morphological patterns of polyomavirus nephropathy. Determination of HSV-1 and HSV-2 in the biopsy specimens showed no significant associations with morphological changes., Conclusion: By taking into account a variety of factors that influence the development of viral nephritis, morphological and IHC examinations should be combined with evaluation of clinical findings.

Developments of genome amplification techniques have rapidly expanded the family of human polyomaviruses (PyV). Following infection early in life, PyV persist in their hosts and are generally of no clinical consequence. High-level replication of PyV can occur in patients under immunosuppressive or immunomodulatory therapy and causes severe clinical entities, such as progressive multifocal leukoencephalopathy, polyomavirus-associated nephropathy or Merkel cell carcinoma. The characterization of known and newly-discovered human PyV, their relationship to human health, and the mechanisms underlying pathogenesis remain to be elucidated. Here, we summarize the most widely-used in vitro and in vivo models to study the PyV-host interaction, pathogenesis and anti-viral drug screening. We discuss the strengths and limitations of the different models and the lessons learned., Competing Interests: The authors declare no conflict of interest.

Polyomavirus BK-associated nephropathy (BKAN) is an important mechanism for renal losing after kidney transplantation. It seems that Polyomavirus BK can induce nephropathy by direct cell lysis and stimulation of the immune system and induction of inflammation. CXCL10 is a pro-inflammatory cytokine which stimulates the migration and activation of immune cells to the infected sites. Therefore, the aim of the current study was to evaluate the messenger RNA (mRNA) and protein levels of CXCL10 in the Polyomavirus BK-infected and Polyomavirus BK-non-infected post renal transplanted nephropathic patients in comparison to healthy controls. In this cross-sectional study, Polyomavirus BK-infected post renal transplanted nephropathic patients, Polyomavirus BK-non-infected post renal transplanted nephropathic patients, and healthy controls were enrolled to evaluate mRNA and protein levels of CXCL10 by real-time PCR and ELISA techniques, respectively. mRNA levels of CXCL10 were not significantly different among participants, while serum levels of CXCL10 were significantly elevated in the Polyomavirus BK-infected patients when compared to non-infected patients as well as controls and in non-infected patients when compared to healthy controls. Due to the results, it seems that Polyomavirus BK may potentially induce renal losing through stimulation of inflammation via increasing translation of CXCL10, as a pro-inflammatory chemokine.

Unlabelled: The APOBEC3 family of DNA cytosine deaminases has important roles in innate immunity and cancer. It is unclear how DNA tumor viruses regulate these enzymes and how these interactions, in turn, impact the integrity of both the viral and cellular genomes. Polyomavirus (PyVs) are small DNA pathogens that contain oncogenic potentials. In this study, we examined the effects of PyV infection on APOBEC3 expression and activity. We demonstrate that APOBEC3B is specifically upregulated by BK polyomavirus (BKPyV) infection in primary kidney cells and that the upregulated enzyme is active. We further show that the BKPyV large T antigen, as well as large T antigens from related polyomaviruses, is alone capable of upregulating APOBEC3B expression and activity. Furthermore, we assessed the impact of A3B on productive BKPyV infection and viral genome evolution. Although the specific knockdown of APOBEC3B has little short-term effect on productive BKPyV infection, our informatics analyses indicate that the preferred target sequences of APOBEC3B are depleted in BKPyV genomes and that this motif underrepresentation is enriched on the nontranscribed stand of the viral genome, which is also the lagging strand during viral DNA replication. Our results suggest that PyV infection upregulates APOBEC3B activity to influence virus sequence composition over longer evolutionary periods. These findings also imply that the increased activity of APOBEC3B may contribute to PyV-mediated tumorigenesis., Importance: Polyomaviruses (PyVs) are a group of emerging pathogens that can cause severe diseases, including cancers in immunosuppressed individuals. Here we describe the finding that PyV infection specifically induces the innate immune DNA cytosine deaminase APOBEC3B. The induced APOBEC3B enzyme is fully functional and therefore may exert mutational effects on both viral and host cell DNA. We provide bioinformatic evidence that, consistent with this idea, BK polyomavirus genomes are depleted of APOBEC3B-preferred target motifs and enriched for the corresponding predicted reaction products. These data imply that the interplay between PyV infection and APOBEC proteins may have significant impact on both viral evolution and virus-induced tumorigenesis., (Copyright © 2016, American Society for Microbiology. All Rights Reserved.)

Malignant tumours are the foremost complications of immunosuppressive treatment. They are a major challenge for organ transplant recipients and their treating physicians. This paper reviews the aetiology and current treatment of an unusual neuroendocrine skin cancer, Merkel cell carcinoma (MCC), caused by a Merkel cell polyomavirus infection. MCC occurs more frequently than expected in immunosuppressed subjects, especially in organ transplant recipients. The current literature comprises reports of 79 organ transplant recipients with MCC. The risk of MCC in organ transplant recipients is increased up to 66-182-fold compared with the general population. In addition to the increased risk of developing MCC, immunosuppressed individuals have poorer MCC-specific survival. The aim of this review article is to familiarize organ transplant doctors with this unique and clinically challenging skin cancer, and to provide recent data on the diagnosis and current treatment recommendations for an immunosuppressed population.

The number of polyomaviruses causing infections in humans is as high as thirteen. The BK and JC polyomaviruses and the diseases caused by them are best known. For the present, the Merkel cell polyomavirus is the only human polyomavirus considered to be a causative agent of cancer. Other disease associations of polyomaviruses are also subject to active research. All polyomavirus infections are usually harmless respiratory or intestinal infections of childhood. Polyomaviruses, remain in the body for the rest of life, i.e. they persist as part of the body microbiome. Upon weakening of cell-mediated immunity they can also become reactivated and cause clinical problems.

During pregnancy, the ETS transcription factor ELF5 establishes the milk-secreting alveolar cell lineage by driving a cell fate decision of the mammary luminal progenitor cell. In breast cancer, ELF5 is a key transcriptional determinant of tumor subtype and has been implicated in the development of insensitivity to anti-estrogen therapy. In the mouse mammary tumor virus-Polyoma Middle T (MMTV-PyMT) model of luminal breast cancer, induction of ELF5 levels increased leukocyte infiltration, angiogenesis, and blood vessel permeability in primary tumors and greatly increased the size and number of lung metastasis. Myeloid-derived suppressor cells, a group of immature neutrophils recently identified as mediators of vasculogenesis and metastasis, were recruited to the tumor in response to ELF5. Depletion of these cells using specific Ly6G antibodies prevented ELF5 from driving vasculogenesis and metastasis. Expression signatures in luminal A breast cancers indicated that increased myeloid cell invasion and inflammation were correlated with ELF5 expression, and increased ELF5 immunohistochemical staining predicted much shorter metastasis-free and overall survival of luminal A patients, defining a group who experienced unexpectedly early disease progression. Thus, in the MMTV-PyMT mouse mammary model, increased ELF5 levels drive metastasis by co-opting the innate immune system. As ELF5 has been previously implicated in the development of antiestrogen resistance, this finding implicates ELF5 as a defining factor in the acquisition of the key aspects of the lethal phenotype in luminal A breast cancer.

Murine polyomavirus (MuPyV) causes tumors of various origins in newborn mice and hamsters. Infection is initiated by attachment of the virus to ganglioside receptors at the cell surface. Single amino acid exchanges in the receptor-binding pocket of the major capsid protein VP1 are known to drastically alter tumorigenicity and spread in closely related MuPyV strains. The virus represents a rare example of differential receptor recognition directly influencing viral pathogenicity, although the factors underlying these differences remain unclear. We performed structural and functional analyses of three MuPyV strains with strikingly different pathogenicities: the low-tumorigenicity strain RA, the high-pathogenicity strain PTA, and the rapidly growing, lethal laboratory isolate strain LID. Using ganglioside deficient mouse embryo fibroblasts, we show that addition of specific gangliosides restores infectability for all strains, and we uncover a complex relationship between virus attachment and infection. We identify a new infectious ganglioside receptor that carries an additional linear [α-2,8]-linked sialic acid. Crystal structures of all three strains complexed with representative oligosaccharides from the three main pathways of ganglioside biosynthesis provide the molecular basis of receptor recognition. All strains bind to a range of sialylated glycans featuring the central [α-2,3]-linked sialic acid present in the established receptors GD1a and GT1b, but the presence of additional sialic acids modulates binding. An extra [α-2,8]-linked sialic acid engages a protein pocket that is conserved among the three strains, while another, [α-2,6]-linked branching sialic acid lies near the strain-defining amino acids but can be accommodated by all strains. By comparing electron density of the oligosaccharides within the binding pockets at various concentrations, we show that the [α-2,8]-linked sialic acid increases the strength of binding. Moreover, the amino acid exchanges have subtle effects on their affinity for the validated receptor GD1a. Our results indicate that both receptor specificity and affinity influence MuPyV pathogenesis.

Trichodysplasia spinulosa-associated Polyomavirus (TSPyV) was isolated from a patient suffering from trichodysplasia spinulosa, a skin disease that can appear in severely immunocompromised patients. While TSPyV is one of the five members of the polyomavirus family that are directly linked to a human disease, details about molecular recognition events, the viral entry pathway, and intracellular trafficking events during TSPyV infection remain unknown. Here we have used a structure-function approach to shed light on the first steps of TSPyV infection. We established by cell binding and pseudovirus infection studies that TSPyV interacts with sialic acids during attachment and/or entry. Subsequently, we solved high-resolution X-ray structures of the major capsid protein VP1 of TSPyV in complex with three different glycans, the branched GM1 glycan, and the linear trisaccharides α2,3- and α2,6-sialyllactose. The terminal sialic acid of all three glycans is engaged in a unique binding site on TSPyV VP1, which is positioned about 18 Å from established sialic acid binding sites of other polyomaviruses. Structure-based mutagenesis of sialic acid-binding residues leads to reduction in cell attachment and pseudovirus infection, demonstrating the physiological relevance of the TSPyV VP1-glycan interaction. Furthermore, treatments of cells with inhibitors of N-, O-linked glycosylation, and glycosphingolipid synthesis suggest that glycolipids play an important role during TSPyV infection. Our findings elucidate the first molecular recognition events of cellular infection with TSPyV and demonstrate that receptor recognition by polyomaviruses is highly variable not only in interactions with sialic acid itself, but also in the location of the binding site.

Background: Eleven new human polyomaviruses (HPyVs) have been identified in the last decade. Serological studies show that these novel HPyVs sub-clinically infect humans at an early age. The routes of infection, entry pathways, and cell tropism of new HPyVs remain unknown. VP1 proteins of polyomaviruses can assembly into virus-like particles (VLPs). As cell culturing systems for HPyV are currently not available, VP1-derived VLPs may be useful tools in basic research and biotechnological applications., Results: Recombinant VP1-derived VLPs from 11 newly identified HPyVs were efficiently expressed in yeast. VP1 proteins derived from Merkel cell polyomavirus (MCPyV), trichodysplasia spinulosa-associated polyomavirus (TSPyV), and New Jersey polyomavirus (NJPyV) self-assembled into homogeneous similarly-sized VLPs. Karolinska Institutet polyomavirus (KIPyV), HPyV7, HPyV9, HPyV10, and St. Louis polyomavirus (STLPyV) VP1 proteins formed VLPs that varied in size with diameters ranging from 20 to 60 nm. Smaller-sized VLPs (25-35 nm in diameter) predominated in preparations from Washington University polyomavirus (WUPyV) and HPyV6. Attempts to express recombinant HPyV12 VP1-derived VLPs in yeast indicate that translation of VP1 might start at the second of two potential translation initiation sites in the VP1-encoding open reading frame (ORF). This translation resulted in a 364-amino acid-long VP1 protein, which efficiently self-assembled into typical PyV VLPs. MCPyV-, KIPyV-, TSPyV-, HPyV9-, HPyV10-, and HPyV12-derived VLPs showed hemagglutination (HA) assay activity in guinea pig erythrocytes, whereas WUPyV-, HPyV6-, HPyV7-, STLPyV- and NJPyV-derived VP1 VLPs did not., Conclusions: The yeast expression system was successfully utilized for high-throughput production of recombinant VP1-derived VLPs from 11 newly identified HPyVs. HPyV12 VP1-derived VLPs were generated from the second of two potential translation initiation sites in the VP1-encoding ORF. Recombinant VLPs produced in yeast originated from different HPyVs demonstrated distinct HA activities and may be useful in virus diagnostics, capsid structure studies, or investigation of entry pathways and cell tropism of HPyVs until cell culture systems for new HPyVs are developed.

Polyomaviruses are non-enveloped, dsDNA viruses that are common in mammals, including humans. All polyomaviruses encode the large T-antigen and small t-antigen proteins that share conserved functional domains, comprising binding motifs for the tumor suppressors pRb and p53, and for protein phosphatase 2A, respectively. At present, 13 different human polyomaviruses are known, and for some of them their large T-antigen and small t-antigen have been shown to possess oncogenic properties in cell culture and animal models, while similar functions are assumed for the large T- and small t-antigen of other human polyomaviruses. However, so far the Merkel cell polyomavirus seems to be the only human polyomavirus associated with cancer. The large T- and small t-antigen exert their tumorigenic effects through classical hallmarks of cancer: inhibiting tumor suppressors, activating tumor promoters, preventing apoptosis, inducing angiogenesis and stimulating metastasis. This review elaborates on the putative roles of human polyomaviruses in some of the emerging hallmarks of cancer. The reciprocal interactions between human polyomaviruses and the immune system response are discussed, a plausible role of polyomavirus-encoded and polyomavirus-induced microRNA in cancer is described, and the effect of polyomaviruses on energy homeostasis and exosomes is explored. Therapeutic strategies against these emerging hallmarks of cancer are also suggested.

Mixed cryoglobulinemia is a lymphoproliferative disorder associated with hepatitis C virus (HCV). In patients chronically affected by HCV the prevalence of mixed cryoglobulinemia is variable ranging from 0% to 56%. To verify whether polyomaviruses (PyV) play a role in this disorder a total of 222 blood samples from 63 HCV chronic patients, 43 with mixed cryoglobulinemia, 59 chronic lymphocytic leukemia, 50 polytransfused patients, and 50 blood donors were evaluated for Merkel (MCPyV), BKV, JCV, and SV40. EBV was additionally included in the analysis since association with this disorder has been reported. Mixed cryoglobulinemia patients infected chronically with HCV resulted negative for both PyV and EBV. MCPyV was found in 1 subject with Merkel Cell Carcinoma, in 10% of polytransfused and in 10% of blood donors while EBV was detected in 22% of polytransfused, 10% of B-cell lymphatic leukemia patients and 4% of blood donors (P < 0.01). Taken together, the absence of PyV and EBV in HCV-mixed cryoglobulinemia patients seems to exclude a direct involvement of these viruses in the pathogenesis of this disease while the presence of MCPyV in healthy individuals, at the same rate as in polytransfused patients, may reinforce data on a minimal role of this virus in other human pathologies., (© 2013 Wiley Periodicals, Inc.)

The polyomavirus family is rapidly expanding with twelve new human viruses identified since 2007. A significant number of the new human polyomaviruses (HPyV) has been found on the skin. Whether these viruses share biological properties and should be grouped together is unknown. Here we investigated the serological behavior of cutaneous HPyVs in a general population. 799 sera from immunocompetent Australian individuals aged between 0-87 were analyzed with a Luminex xMAP technology-based immunoassay for the presence of VP1-directed IgG antibodies against MCPyV, HPyV6, HPyV7, TSPyV, HPyV9, and BKPyV as a control. Except for HPyV9, overall seropositivity was high for the cutanous polyomaviruses (66-81% in adults), and gradually increased with age. Children below 6 months displayed seropositivity rates comparable to the adults, indicative of maternal antibodies. TSPyV seroreactivity levels strongly increased after age 2 and waned later in life comparable to BKPyV, whereas MCPyV, HPyV6 and HPyV7 seroreactivity remained rather stable throughout. Based on the identified serologic profiles, MCPyV seems to cluster with HPyV6 and HPyV7, and TSPyV and HPyV9 by themselves. These profiles indicate heterogeneity among cutaneous polyomaviruses and probably reflect differences in exposure and pathogenic behavior of these viruses.

We have detected a high incidence of lymphomas in a colony of GASH:Sal Syrian golden hamsters (Mesocricetus auratus). This strain is characterised by its ability to present convulsive crises of audiogenic origin. Almost 16 % (90 males and 60 females) of the 975 animals were affected during a 5-year period by the development of a progressing lymphoid tumour and exhibited similar clinical profiles characterised by lethargy, anorexia, evident abdominal distension, and a rapid disease progression resulting in mortality within 1 to 2 weeks. A TaqMan® probe-based real-time PCR analysis of genomic DNA from different tissue samples of the affected animals revealed the presence of a DNA sequence encoding the hamster polyomavirus (HaPyV) VP1 capsid protein. Additionally, immunohistochemical analysis using HaPyV-VP1-specific monoclonal antibodies confirmed the presence of viral proteins in all hamster tumour tissues analysed within the colony. An indirect ELISA and western blot analysis confirmed the presence of antibodies against the VP1 capsid protein in sera, not only from affected and non-affected GASH:Sal hamsters but also from control hamsters from the same breeding area. The HaPyV genome that accumulated in tumour tissues typically contained deletions affecting the noncoding regulatory region and adjacent sequences coding for the N-terminal part of the capsid protein VP2.

Trichodysplasia spinulosa-associated polyomavirus (TSPyV) is a new species of the family Polyomaviridae that was discovered in 2010. TSPyV infects humans and is associated with the development of a rare disease called trichodysplasia spinulosa. Trichodysplasia spinulosa is a skin disease of severely immunocompromised hosts characterized by follicular distention and keratotic spine formation especially on the face. Electron microscopy, immunohistochemistry, and viral load measurements indicate an etiological role of active TSPyV infection in the development of this disease. This review will address virological and pathogenic properties of TSPyV, as well as epidemiologic, diagnostic, and therapeutic aspects of TSPyV infection., (© 2013 APMIS. Published by John Wiley & Sons Ltd.)

Polyomaviruses, classified in Polyomaviridae family, are non-enveloped small (40-45 nm) viruses with icosahedral symmetry and circular double-stranded DNA genome. Polyomaviruses can infect a variety of vertebrates including birds, rodents, cattle, monkeys and humans. The characteristics such as establishment of latent infections, reactivations during immunosuppression and oncogenic potencies render the human polyomaviruses (HPyVs) of considerable importance for public health. The first polyomavirus (Mouse polyomavirus) has been identified in 1953 as filterable tumor-causing agents in mice, followed by Simian vacuolating virus (SV40) isolated from rhesus monkey kidney cells that had been used for poliovirus vaccine preparation in 1960. Due to the known transforming capacity of SV40, it was initially thought that the incidence of cancer could increase following the administration of SV40-contaminated polio vaccines, however advanced studies yielded inconsistent results, without any evidence to conclude whether or not the contaminated polio vaccine caused cancer. Several studies have reported the detection of SV40 genome in some of the human tumors, as well as in the clinical samples of healthy subjects. In addition SV40 seropositivity was reported in human populations although in low rates (2-10%). These data have raised the possibility that SV40 infects humans and circulates in human populations unrelated to being exposed to the vaccine. The discovery of the first human polyomaviruses was in 1971 independently from each other, one was BK virus (BKPyV) isolated from the urine sample of a renal transplant patient, and the other was JC virus (JCPyV) isolated from the brain tissue of a patient with progressive multifocal leukoencephalopathy, and both were named after the patients' initials. BK and JC viruses were the only well-known human polyomaviruses throughout 36 years, however drammatical increase in number of newly identified human polyomaviruses was recorded in the last six years due to the use of sophisticated molecular methods and new-generation sequencing technologies. In 2007, two new HPyVs were identified independently from nasopharyngeal aspirates of children with acute respiratory tract infections; one was KI (Karolinska Institute) and the other was WU (Washington University) polyomaviruses, named after the initials of institutes which they were first described. In 2008, the fifth HPyV namely Merkel cell polyomavirus (MCPyV) was isolated from the skin tumor sample of a patient with Merkel cell carcinoma. In 2010, three other novel human polyomaviruses were discovered, two were from skin samples of healthy subjects (HPyV-6 and HPyV-7), and one (Trichodysplasia Spinulosa-associated virus; TSPyV) from keratotic spicule sample of a heart-transplanted patient. Another new HPyV was identified in 2011 named HPyV-9, from the blood and urine samples of an asymptomatic patient with kidney transplant. Most recently, three new HPyVs have been sequentially discovered during the last quarter of 2012. The 10th HPyV (HPyV10) was identified in condyloma samples of an immunocompromised patient with WHIM syndrome (Wart, Hypogammaglobulinemia, Infections, Myelokathexis), 11th virus was isolated from stool sample of a healthy child from Malawi (Malawi polyomavirus; MWPyV), and 12th was described from fecal sample of a diarrheal child from Mexico (Mexico polyomavirus; MXPyV). The whole genome sequence analysis of HPyV10, MWPyV and MXPyV pointed out that they are closely related viruses. The last novel polyomavirus, namely Saint Louis polyomavirus (STLPyV) has been reported in a study published on February 2013, identified from the stool sample of a healthy child. Seroepidemiological studies indicated that most of the novel HPyVs are highly prevalent (average rate: 40-80%) worldwide and likely acquired asymptomatically during childhood, similar to the old ones, BKPyV and JCPyV. However data about HPyV10, MWPyV, MXPyV and STLPyV are not enough as they have been discovered most recently. Similarly, little is known about the pathogenesis, route of infection and the relationship with clinical diseases of novel HPyVs except MCPyV and TSPyV which are known to be responsible for Merkel cell carcinoma and trichodysplasia spinulosa, respectively. The expanding repertoire of human polyomaviruses made us think that many others will be uncovered in the future thanking to the advances in molecular methods. In this review, recent developments subjecting new human polyomaviruses have been summarized.