Whole genome sequencing of recombinant viruses obtained from co-infection and superinfection of Vero cells with modified vaccinia virus ankara vectored influenza vaccine and a naturally occurring cowpox virus.

Modified vaccinia virus Ankara (MVA) has been widely tested in clinical trials as recombinant vector vaccine against infectious diseases and cancers in humans and animals. However, one biosafety concern about the use of MVA vectored vaccine is the potential for MVA to recombine with naturally occurring orthopoxviruses in cells and hosts in which it multiplies poorly and, therefore, producing viruses with mosaic genomes with altered genetic and phenotypic properties. We previously conducted co-infection and superinfection experiments with MVA vectored influenza vaccine (MVA-HANP) and a feline Cowpox virus (CPXV-No-F1) in Vero cells (that were semi-permissive to MVA infection) and showed that recombination occurred in both co-infected and superinfected cells. In this study, we selected the putative recombinant viruses and performed genomic characterization of these viruses. Some putative recombinant viruses displayed plaque morphology distinct of that of the parental viruses. Our analysis demonstrated that they had mosaic genomes of different lengths. The recombinant viruses, with a genome more similar to MVA-HANP (>50%), rescued deleted and/or fragmented genes in MVA and gained new host ranges genes. Our analysis also revealed that some MVA-HANP contained a partially deleted transgene expression cassette and one recombinant virus contained part of the transgene expression cassette similar to that incomplete MVA-HANP. The recombination in co-infected and superinfected Vero cells resulted in recombinant viruses with unpredictable biological and genetic properties as well as recovery of delete/fragmented genes in MVA and transfer of the transgene into replication competent CPXV. These results are relevant to hazard characterization and risk assessment of MVA vectored biologicals.

Merkel Cell Polyomavirus in the Context of Oral Squamous Cell Carcinoma and Oral Potentially Malignant Disorders.

Despite recent advances in prevention, detection and treatment, oral squamous cell carcinoma (OSCC) remains a global health concern, strongly associated with environmental and lifestyle risk factors and infection with oncogenic viruses. Merkel Cell Polyomavirus (MCPyV), well known to be the causative agent of Merkel Cell Carcinoma (MCC) has been found in OSCC, suggesting its potential role as a co-factor in the development of oral cavity cancers. To improve our understanding about MCPyV in oral cavities, the detection and analysis of MCPyV DNA, transcripts and miRNA were performed on OSCCs and oral potentially malignant disorders (OPMDs). In addition, the cellular miR-375, known to be deregulated in tumors, was examined. MCPyV DNA was found in 3 out of 11 OSCC and 4 out of 12 OPMD samples, with a viral mean value of 1.49 × 102 copies/mL. Viral integration was not observed and LTAg and VP1 transcripts were detected. Viral miRNAs were not detected whereas the cellular miR-375 was found over expressed in all MCPyV positive oral specimens. Our results reported evidence of MCPyV replication in both OSCC and OPMD suggesting the oral cavity as a site of replicative MCPyV infection, therefore underscoring an active role of this virus in the occurrence of oral lesions.

Differentiation of highly pathogenic strains of human JC polyomavirus in neurological patients by next generation sequencing.

BACKGROUND: JC polyomavirus (JCPyV) persists asymptomatic in more than half of the human population. Immunocompromising conditions may cause reactivation and acquisition of neurotropic rearrangements in the viral genome, especially in the non-coding control region (NCCR). Such rearranged JCPyV strains are strongly associated with the development of progressive multifocal leukoencephalopathy (PML). METHODS: Using next-generation sequencing (NGS) and bioinformatics tools, the NCCR was characterized in cerebrospinal fluid (CSF; N = 21) and brain tissue (N = 16) samples from PML patients (N = 25), urine specimens from systemic lupus erythematosus patients (N = 2), brain tissue samples from control individuals (N = 2) and waste-water samples (N = 5). Quantitative PCR was run in parallel for diagnostic PML samples. RESULTS: Archetype NCCR (i.e. ABCDEF block structure) and archetype-like NCCR harboring minor mutations were detected in two CSF samples and in one CSF sample and in one tissue sample, respectively. Among samples from PML patients, rearranged NCCRs were found in 8 out of 21 CSF samples and in 14 out of 16 brain tissue samples. Complete or partial deletion of the C and D blocks was characteristic of most rearranged JCPyV strains. From ten CSF samples and one tissue sample NCCR could not be amplified. CONCLUSIONS: Rearranged NCCRs are predominant in brain tissue and common in CSF from PML patients. Extremely sensitive detection and identification of neurotropic viral populations in CSF or brain tissue by NGS may contribute to early and accurate diagnosis, timely intervention and improved patient care.

Phosphorylation of Human Polyomavirus Large and Small T Antigens: An Ignored Research Field.

Protein phosphorylation and dephosphorylation are the most common post-translational modifications mediated by protein kinases and protein phosphatases, respectively. These reversible processes can modulate the function of the target protein, such as its activity, subcellular localization, stability, and interaction with other proteins. Phosphorylation of viral proteins plays an important role in the life cycle of a virus. In this review, we highlight biological implications of the phosphorylation of the monkey polyomavirus SV40 large T and small t antigens, summarize our current knowledge of the phosphorylation of these proteins of human polyomaviruses, and conclude with gaps in the knowledge and a proposal for future research directions.

Detection of Merkel Cell Polyomavirus (MCPyV) DNA and Transcripts in Merkel Cell Carcinoma (MCC).

Merkel cell polyomavirus (MCPyV) is the etiological agent of the majority of Merkel cell carcinoma (MCC): a rare skin tumor. To improve our understanding of the role of MCPyV in MCCs, the detection and analysis of MCPyV DNA and transcripts were performed on primary tumors and regional lymph nodes from two MCC patients: one metastatic and one non-metastatic. MCPyV-DNA was searched by a quantitative polymerase chain reaction (qPCR), followed by the amplification of a Large T Antigen (LTAg), Viral Protein 1 (VP1) and Non-Coding Control Region (NCCR). LTAg and VP1 transcripts were investigated by reverse-transcription PCR (RT-PCR). Viral integration was also studied, and full-length LTAg sequencing was performed. qPCR revealed that the primary tumor of both patients and the lymph node of one patient was positive for the small t-antigen, with an average value of 7.0 × 102 copies/µg. The same samples harbored LTAg, NCCR and VP1 DNA. Sequencing results showed truncated LTAg with the conserved retinoblastoma (Rb) protein binding motif and VP1 and NCCR sequences identical to the MCC350 strain. RT-PCR detected LTAg but not VP1 transcripts. The MCPyV genome was integrated into the primary tumor of both patients. The results confirmed the connection between MCPyV and MCC, assuming integration, LTAg truncation and Rb sequestration as key players in MCPyV-mediated oncogenesis.

Detection of human neurotropic JCPyV DNA sequence in pediatric anaplastic xanthoastrocytoma.

Due to its peculiar histopathological findings, pleomorphic xanthoastrocytoma (PXA), a rare cerebral tumor of young adults with a slow growth and a good prognosis, resembles to the lytic phase of progressive multifocal leukoencephalopathy, a fatal neurodegenerative disease caused by JC polyomavirus (JCPyV). Therefore, the presence of JCPyV DNA was examined in an 11-year-old child with xanthoastrocytoma, WHO grade 3, by quantitative PCR (qPCR) and nested PCR (nPCR) using primers amplifying sequences encoding the N- and C-terminal region of large T antigen (LTAg), the non-coding control region (NCCR), and viral protein 1 (VP1) DNA. The expression of transcripts from LTAg and VP1 genes was also evaluated. In addition, viral microRNAs' (miRNAs) expression was investigated. Cellular p53 was also searched at both DNA and RNA level. qPCR revealed the presence of JCPyV DNA with a mean value of 6.0 × 104 gEq/mL. nPCR gave a positive result for the 5' region of the LTAg gene and the NCCR, whereas 3' end LTAg and VP1 DNA sequences were not amplifiable. Only LTAg transcripts of 5' end were found whereas VP1 gene transcript was undetectable. Although in most cases, either Mad-1 or Mad-4 NCCRs have been identified in association with JCPyV-positive human brain neoplasms, the archetype NCCR structure was observed in the patient's sample. Neither viral miRNA miR-J1-5p nor p53 DNA and RNA were detected. Although the expression of LTAg supports the possible role of JCPyV in PXA, further studies are warranted to better understand whether the genesis of xanthoastrocytoma could depend on the transformation capacity of LTAg by Rb sequestration.

JC polyomavirus: a short review of its biology, its association with progressive multifocal leukoencephalopathy, and the diagnostic value of different methods to manifest its activity or presence.

INTRODUCTION: JC polyomavirus is the causative agent of progressive multifocal leukoencephalopathy (PML), a demyelinating disease resulting from the lytic infection of oligodendrocytes that may develop in immunosuppressed individuals: HIV1 infected or individuals under immunosuppressive therapies. Understanding the biology of JCPyV is necessary for a proper patient management, the development of diagnostic tests, and risk stratification. AREAS COVERED: The review covers different areas of expertise including the genomic characterization of JCPyV strains detected in different body compartments (urine, plasma, and cerebrospinal fluid) of PML patients, viral mutations, molecular diagnostics, viral miRNAs, and disease. EXPERT OPINION: The implementation of molecular biology techniques improved our understanding of JCPyV biology. Deep sequencing analysis of viral genomes revealed the presence of viral quasispecies in the cerebrospinal fluid of PML patients characterized by noncoding control region rearrangements and VP1 mutations. These neurotropic JCPyV variants present enhanced replication and an altered cell tropism that contribute to PML development. Monitoring these variants may be relevant for the identification of patients at risk of PML. Multiplex realtime PCR targeting both the LTAg and the archetype NCCR could be used to identify them. Failure to amplify NCCR should indicate the presence of a JCPyV prototype speeding up the diagnostic process.

Regulation of Transcriptional Activity of Merkel Cell Polyomavirus Large T-Antigen by PKA-Mediated Phosphorylation.

Merkel cell polyomavirus (MCPyV) is the major cause of Merkel cell carcinoma (MCC), an aggressive skin cancer. MCPyV large T-antigen (LTag) and small T-antigen (sTag) are the main oncoproteins involved in MCPyV-induced MCC. A hallmark of MCPyV-positive MCC cells is the expression of a C-terminal truncated LTag. Protein kinase A (PKA) plays a fundamental role in a variety of biological processes, including transcription by phosphorylating and thereby regulating the activity of transcription factors. As MCPyV LTag has been shown to be phosphorylated and acts as a transcription factor for the viral early and late promoter, we investigated whether LTag can be phosphorylayted by PKA, and whether this affects the transcript activity of LTag. Using a phosphorylation prediction algorithm, serine 191, 203, and 265 were identified as putative phosphorylation sites for PKA. Mass spectrometry of in vitro PKA-phosphorylated peptides confirmed phosphorylation of S203 and S265, but not S191. Full-length LTag inhibited early and late promoter activity of MCPyV, whereas the truncated MKL2 LTag variant stimulated both promoters. Single non-phosphorylable, as well as phosphomimicking mutations did not alter the inhibitory effect of full-length LTag. However, the non-phosphorylable mutations abrogated transactivation of the MCPyV promoters by MKL2 LTag, whereas phosphomimicking substitutions restored the ability of MKL2 LTag to activate the promoters. Triple LTag and MKL2 LTag mutants had the same effect as the single mutants. Activation of the PKA signaling pathway did not enhance MCPyV promoter activity, nor did it affect LTag expression levels in MCPyV-positive Merkel cell carcinoma (MCC) cells. Our results show that phosphorylation of truncated LTag stimulates viral promoter activity, which may contribute to higher levels of the viral oncoproteins LTag and sTag. Interfering with PKA-induced LTag phosphorylation/activity may be a therapeutic strategy to treat MCPyV-positive MCC patients.

Detection Analysis and Study of Genomic Region Variability of JCPyV, BKPyV, MCPyV, HPyV6, HPyV7 and QPyV in the Urine and Plasma of HIV-1-Infected Patients.

Since it was clearly established that HIV/AIDS predisposes to the infection, persistence or reactivation of latent viruses, the prevalence of human polyomaviruses (HPyVs) among HIV-1-infected patients and a possible correlation between HPyVs and HIV sero-status were investigated. PCR was performed to detect and quantify JCPyV, BKPyV, MCPyV, HPyV6, HPyV7 and QPyV DNA in the urine and plasma samples of 103 HIV-1-infected patients. Subsequently, NCCR, VP1 and MCPyV LT sequences were examined. In addition, for MCPyV, the expression of transcripts for the LT gene was investigated. JCPyV, BKPyV and MCPyV's presence was reported, whereas HPyV6, HPyV7 and QPyV were not detected in any sample. Co-infection patterns of JCPyV, BKPyV and MCPyV were found. Archetype-like NCCRs were observed with some point mutations in plasma samples positive for JCPyV and BKPyV. The VP1 region was found to be highly conserved among these subjects. LT did not show mutations causing stop codons, and LT transcripts were expressed in MCPyV positive samples. A significant correlation between HPyVs' detection and a low level of CD4+ was reported. In conclusion, HPyV6, HPyV7 and QPyV seem to not have a clinical relevance in HIV-1 patients, whereas further studies are warranted to define the clinical importance of JCPyV, BKPyV and MCPyV DNA detection in these subjects.

Genomic Sequencing and Phylogenomics of Cowpox Virus.

Cowpox virus (CPXV; genus Orthopoxvirus; family Poxviridae) is the causative agent of cowpox, a self-limiting zoonotic infection. CPXV is endemic in Eurasia, and human CPXV infections are associated with exposure to infected animals. In the Fennoscandian region, five CPXVs isolated from cats and humans were collected and used in this study. We report the complete sequence of their genomes, which ranged in size from 220-222 kbp, containing between 215 and 219 open reading frames. The phylogenetic analysis of 87 orthopoxvirus strains, including the Fennoscandian CPXV isolates, confirmed the division of CPXV strains into at least five distinct major clusters (CPXV-like 1, CPXV-like 2, VACV-like, VARV-like and ECTV-Abatino-like) and can be further divided into eighteen sub-species based on the genetic and patristic distances. Bayesian time-scaled evolutionary history of CPXV was reconstructed employing concatenated 62 non-recombinant conserved genes of 55 CPXV. The CPXV evolution rate was calculated to be 1.65 × 10-5 substitution/site/year. Our findings confirmed that CPXV is not a single species but a polyphyletic assemblage of several species and thus, a reclassification is warranted.

COS-7 and SVGp12 Cellular Models to Study JCPyV Replication and MicroRNA Expression after Infection with Archetypal and Rearranged-NCCR Viral Strains.

Since the non-coding control region (NCCR) and microRNA (miRNA) could represent two different and independent modalities of regulating JC polyomavirus (JCPyV) replication at the transcriptional and post-transcriptional levels, the interplay between JC viral load based on NCCR architecture and miRNA levels, following JCPyV infection with archetypal and rearranged (rr)-NCCR JCPyV variants, was explored in COS-7 and SVGp12 cells infected by different JCPyV strains. Specifically, the involvement of JCPyV miRNA in regulating viral replication was investigated for the archetypal CY strain-which is the transmissible form-and for the rearranged MAD-1 strain, which is the first isolated variant from patients with progressive multifocal leukoencephalopathy. The JCPyV DNA viral load was low in cells infected with CY compared with that in MAD-1-infected cells. Productive viral replication was observed in both cell lines. The expression of JCPyV miRNAs was observed from 3 days after viral infection in both cell types, and miR-J1-5p expression was inversely correlated with the JCPyV replication trend. The JCPyV miRNAs in the exosomes present in the supernatants produced by the infected cells could be carried into uninfected cells. Additional investigations of the expression of JCPyV miRNAs and their presence in exosomes are necessary to shed light on their regulatory role during viral reactivation.

High prevalence of Merkel cell polyomavirus is associated with dysregulation in transcript levels of TLR9 and type I IFNs in a large cohort of CF patients from the Italian (Lazio) reference center for cystic fibrosis.

Merkel cell polyomavirus (MCPyV) has been detected in respiratory specimens including those from Cystic Fibrosis (CF) patients, raising questions about its immunological and clinical relevance in the respiratory tract. MCPyV might promote an inappropriate antiviral response contributing to a chronic inflammatory response and resulting in detrimental effects in CF. Respiratory samples (n = 1138) were randomly collected from respiratory tract of CF patients (n = 539) during July 2018-October 2019. MCPyV-DNA detection was performed by real time PCR and positive samples were characterized by sequencing of the NCCR genomic region. The transcript levels of Toll-like receptor 9 (TLR9) and type I interferon (IFN-I) genes (IFNα, IFNß and IFNε) were examined by real-time RT-PCR assays. MCPyV-DNA was detected in 268 out of 1138 respiratory specimens (23.5%) without any difference in the prevalence of MCPyV-DNA according to age, gender or bacteriological status of CF individuals. Thirteen out of 137 CF patients remained positive for MCPyV-DNA over the time (a median follow-up period of 8.8 months). Detection of MCPyV-DNA in respiratory specimens was not associated with the occurrence of exacerbation events. Both MCPyV positive adolescents (11-24 years) and adults (≥25 years) had lower mRNA levels of TLR9, IFNß, IFNε and IFNα than the negative patients of the same age group, while MCPyV positive children produced increased levels of TLR9 and IFN-I genes (p < 0.05 for TLR9, IFNß, IFNε) with respect to the negative ones. There were significant differences in TLR9 levels (p < 0.01), but not in those of IFNs, between MCPyV-DNA positive and negative patients with S. aureus, P. aeruginosa or both. Overall, these results indicate that MCPyV-DNA is frequently detected in the respiratory samples of CF patients and might influence the expression levels of IFN-related genes in an age dependent manner. The concomitant detection of MCPyV together with S. aureus and/or P. aeruginosa correlated with alterations in TLR9 levels suggesting that virus-bacteria coinfections might contribute to affect antiviral immunity in CF patients.

The Merkel Cell Polyomavirus T-Antigens and IL-33/ST2-IL1RAcP Axis: Possible Role in Merkel Cell Carcinoma.

Merkel cell polyomavirus (MCPyV) is a causal factor in Merkel cell carcinoma (MCC). The oncogenic potential is mediated through its viral oncoproteins large T-antigen (LT) and small T-antigen (sT). Cytokines produced by tumor cells play an important role in cancer pathogenesis, and viruses affect their expression. Therefore, we compared human cytokine and receptor transcript levels in virus positive (V+) and virus negative (V-) MCC cell lines. Increased expression of IL-33, a potent modulator of tumor microenvironment, was observed in V+ MCC cell lines when compared to V- MCC-13 cells. Transient transfection studies with luciferase reporter plasmids demonstrated that LT and sT stimulated IL-33, ST2/IL1RL1 and IL1RAcP promoter activity. The induction of IL-33 expression was confirmed by transfecting MCC-13 cells with MCPyV LT. Furthermore, recombinant human cytokine domain IL-33 induced activation of MAP kinase and NF-κB pathways, which could be blocked by a ST2 receptor antibody. Immunohistochemical analysis demonstrated a significantly stronger IL-33, ST2, and IL1RAcP expression in MCC tissues compared to normal skin. Of interest, significantly higher IL-33 and IL1RAcP protein levels were observed in MCC patient plasma compared to plasma from healthy controls. Previous studies have demonstrated the implication of the IL-33/STL2 pathway in cancer. Because our results revealed a T-antigens-dependent induction of the IL-33/ST2 axis, IL-33/ST2 may play a role in the tumorigenesis of MCPyV-positive MCC. Therefore, neutralizing the IL-33/ST2 axis may present a novel therapeutic approach for MCC patients.

Functional Domains of the Early Proteins and Experimental and Epidemiological Studies Suggest a Role for the Novel Human Polyomaviruses in Cancer.

As their name indicates, polyomaviruses (PyVs) can induce tumors. Mouse PyV, hamster PyV and raccoon PyV have been shown to cause tumors in their natural host. During the last 30 years, 15 PyVs have been isolated from humans. From these, Merkel cell PyV is classified as a Group 2A carcinogenic pathogen (probably carcinogenic to humans), whereas BKPyV and JCPyV are class 2B (possibly carcinogenic to humans) by the International Agency for Research on Cancer. Although the other PyVs recently detected in humans (referred to here as novel HPyV; nHPyV) share many common features with PyVs, including the viral oncoproteins large tumor antigen and small tumor antigen, as their role in cancer is questioned. This review discusses whether the nHPyVs may play a role in cancer based on predicted and experimentally proven functions of their early proteins in oncogenic processes. The functional domains that mediate the oncogenic properties of early proteins of known PyVs, that can cause cancer in their natural host or animal models, have been well characterized and we examined whether these functional domains are conserved in the early proteins of the nHPyVs and presented experimental evidence that these conserved domains are functional. Furthermore, we reviewed the literature describing the detection of nHPyV in human tumors.

Prevalence of MCPyV, HPyV6, HPyV7 and TSPyV in Actinic Keratosis Biopsy Specimens.

To date, 14 human polyomaviruses (HPyVs) have been identified using high-throughput technologies. Among them, MCPyV, HPyV6, HPyV7 and TSPyV present a skin tropism, but a causal role in skin diseases has been established only for MCPyV as a causative agent of Merkel cell carcinoma (MCC) and TSPyV as an etiological agent of Trichodysplasia Spinulosa (TS). In the search for a possible role for cutaneous HPyVs in the development of skin malignant lesions, we investigated the prevalence of MCPyV, HPyV6, HPyV7 and TSPyV in actinic keratosis (AK), a premalignant skin lesion that has the potential to progress towards a squamous cell carcinoma (SCC). One skin lesion and one non-lesion skin from nine affected individuals were analyzed by qualitative PCR. MCPyV was detected in 9 out of 9 lesion biopsies and 6 out of 8 non-lesion biopsies. HPyV6 was detected only in healthy skin, while HPyV7 and TSPyV were not detected in any skin sample. These findings argue against a possible role of cutaneous HPyVs in AK. However, considering the small sample size analyzed, a definitive conclusion cannot be drawn. Longitudinal studies on large cohorts are warranted.

Diagnostic Value of JC Polyomavirus Viruria, Viremia, Serostatus and microRNA Expression in Multiple Sclerosis Patients Undergoing Immunosuppressive Treatment.

Markers of JC polyomavirus (JCPyV) activity can be used to evaluate the risk of progressive multifocal leukoencephalopathy (PML) in treated multiple sclerosis (MS) patients. The presence of JCPyV DNA and microRNA (miR-J1-5p), the anti-JCV index and the sequence of the non-coding control region (NCCR) in urine and plasma were determined in 42 MS subjects before treatment (T0), 6 months (T6) and 12 months (T12) after natalizumab, ocrelizumab, fingolimod or dimethyl-fumarate administration and in 25 healthy controls (HC). The number of MS patients with viruria increased from 43% at T0 to 100% at T12, whereas it remained similar for the HC group (35-40%). Viremia first occurred 6 months after treatment in MS patients and increased after 12 months, whereas it was absent in HC. The viral load in urine and plasma from the MS cohort increased over time, mostly pronounced in natalizumab-treated patients, whereas it persisted in HC. The archetypal NCCR was detected in all positive urine, whereas mutations were observed in plasma-derived NCCRs resulting in a more neurotropic variant. The prevalence and miR-J1-5p copy number in MS urine and plasma dropped after treatment, whereas they remained similar in HC specimens. Viruria and miR-J1-5p expression did not correlate with anti-JCV index. In conclusion, analyzing JCPyV DNA and miR-J1-5p levels may allow monitoring JCPyV activity and predicting MS patients at risk of developing PML.

Reply to Henriksen, S.; Rinaldo, C.H. Should SVGp12 Be Used for JC Polyomavirus Studies? Comment on "Prezioso et al. COS-7 and SVGp12 Cellular Models to Study JCPyV Replication and MicroRNA Expression after Infection with Archetypal and Rearranged-NCCR Viral Strains. Viruses 2022, 14, 2070".

In relation to the comment by Henriksen and Rinaldo, the authors intend to emphasize that before every experiment with SVGp12 cells they routinely test the cells for the absence of BKPyV contamination. The scientists can state that the SVGp12 cells used in their laboratory were not infected by BKPyV and that their results were also validated on the COS-7 cell line, which is permissive for JCPyV infection. Therefore, the overall findings of the study and its conclusions remain authentic. The authors recommend the necessity of carefully testing SVGp12 cells for BKPyV infection before use or, alternatively, in case of a first purchase; moreover, it is possible to choose different cell lines to avoid running into this unpleasant situation.

Role of Virus-Induced Host Cell Epigenetic Changes in Cancer.

The tumor viruses human T-lymphotropic virus 1 (HTLV-1), hepatitis C virus (HCV), Merkel cell polyomavirus (MCPyV), high-risk human papillomaviruses (HR-HPVs), Epstein-Barr virus (EBV), Kaposi's sarcoma-associated herpes virus (KSHV) and hepatitis B virus (HBV) account for approximately 15% of all human cancers. Although the oncoproteins of these tumor viruses display no sequence similarity to one another, they use the same mechanisms to convey cancer hallmarks on the infected cell. Perturbed gene expression is one of the underlying mechanisms to induce cancer hallmarks. Epigenetic processes, including DNA methylation, histone modification and chromatin remodeling, microRNA, long noncoding RNA, and circular RNA affect gene expression without introducing changes in the DNA sequence. Increasing evidence demonstrates that oncoviruses cause epigenetic modifications, which play a pivotal role in carcinogenesis. In this review, recent advances in the role of host cell epigenetic changes in virus-induced cancers are summarized.

KI and WU Polyomavirus in Respiratory Samples of SARS-CoV-2 Infected Patients.

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has been declared a global pandemic. Our goal was to determine whether co-infections with respiratory polyomaviruses, such as Karolinska Institutet polyomavirus (KIPyV) and Washington University polyomavirus (WUPyV) occur in SARS-CoV-2 infected patients. Oropharyngeal swabs from 150 individuals, 112 symptomatic COVID-19 patients and 38 healthcare workers not infected by SARS-CoV-2, were collected from March 2020 through May 2020 and tested for KIPyV and WUPyV DNA presence. Of the 112 SARS-CoV-2 positive patients, 27 (24.1%) were co-infected with KIPyV, 5 (4.5%) were positive for WUPyV, and 3 (2.7%) were infected simultaneously by KIPyV and WUPyV. Neither KIPyV nor WUPyV DNA was detected in samples of healthcare workers. Significant correlations were found in patients co-infected with SARS-CoV-2 and KIPyV (p < 0.05) and between SARS-CoV-2 cycle threshold values and KIPyV, WUPyV and KIPyV and WUPyV concurrently detected (p < 0.05). These results suggest that KIPyV and WUPyV may behave as opportunistic respiratory pathogens. Additional investigations are needed to understand the epidemiology and the prevalence of respiratory polyomavirus in COVID-19 patients and whether KIPyV and WUPyV could potentially drive viral interference or influence disease outcomes by upregulating SARS-CoV-2 replicative potential.

Reciprocal transactivation of Merkel cell polyomavirus and high-risk human papillomavirus promoter activities and increased expression of their oncoproteins.

BACKGROUND: Approximately 15% of human cancers are attributed to viruses. Numerous studies have shown that high-risk human polyomaviruses (HR-HPV) and Merkel cell polyomavirus (MCPyV) are two human tumor viruses associated with anogenetal and oropharyngeal cancers, and with Merkel cell carcinoma, respectively. MCPyV has been found in HR-HPV positive anogenetal and oropharyngeal tumors, suggesting that MCPyV can act as a co-factor in HR-HPV induced oncogenesis. This prompted us to investigate whether the oncoproteins large T-antigen (LT) and small antigen (sT) of MCPyV could affect the transcriptional activity HPV16 and HPV18 and vice versa whether HPV16 and HPV18 E6 and E7 oncoproteins affected the expression of MCPyV LT and sT. Reciprocal stimulation of these viral oncoproteinscould enhance the oncogenic processes triggered by these tumor viruses. METHODS: Transient co-transfection studies using a luciferase reporter plasmid with the long control region of HPV16 or HPV18, or the early or late promoter of MCPyV and expression plasmids for LT and sT, or E6 and E7, respectively were performed in the HPV-negative cervical cancer cell line C33A, in the keratinocyte cell line HaCaT, and in the oral squamous cell carcinoma cell line HSC-3. Transfections were also performed with deletion mutants of all these promoters and with mutants of all four oncoproteins. Finally, the effect of E6 and E7 on LT and sT expression in the MCPyV-positive Merkel cell carcinoma cell line WaGa and the effect of LT and sT on the expression of E6 and E7 was monitored by Western blotting. RESULTS: LT and sT stimulated the transcriptional activity of the HPV16 and HPV18 LCR and v.v. E6 and E7 potentiated the MCPyV early and late promoter in all cell lines. Induction by E6 and E7 was p53- and pRb-independent, and transactivation by LT did not require DNA binding, nuclear localization and HSC70/pRb interaction, whereas sT stimulated the HPV16/18 LCR activity in a PP2A- and DnaJ-independent manner. CONCLUSIONS: These results indicate that the co-infection of MCPyV may act as a co-factor in the initiation and/or progression of HPV-induced cancers.