Review on the relationship between human polyomaviruses-associated tumors and host immune system

Viral infection, APOBEC3 dysregulation, and cancer

Viral infection plays a significant role in the development and progression of many cancers. Certain viruses, such as Human Papillomavirus (HPV), Epstein-Barr Virus (EBV), and Hepatitis B and C viruses (HBV, HCV), are well-known for their oncogenic potential. These viruses can dysregulate specific molecular and cellular processes through complex interactions with host cellular mechanisms. One such interaction involves a family of DNA mutators known as APOBEC3 (Apolipoprotein B mRNA Editing Catalytic Polypeptide-like 3). The primary function of these cytidine deaminases is to provide protection against viral infections by inducing viral mutagenesis. However, induction and dysregulation of A3 enzymes, driven by viral infection, can inadvertently lead to cellular DNA tumorigenesis. This review focuses on the current knowledge regarding the interplay between viral infection, A3 dysregulation, and cancer, highlighting the molecular mechanisms underlying this relationship.

Iron‑sulfur clusters in viral proteins: Exploring their elusive nature, roles and new avenues for targeting infections

Viruses have evolved complex mechanisms to exploit host factors for replication and assembly. In response, host cells have developed strategies to block viruses, engaging in a continuous co-evolutionary battle. This dynamic interaction often revolves around the competition for essential resources necessary for both host cell and virus replication. Notably, iron, required for the biosynthesis of several cofactors, including iron‑sulfur (FeS) clusters, represents a critical element in the ongoing competition for resources between infectious agents and host. Although several recent studies have identified FeS cofactors at the core of virus replication machineries, our understanding of their specific roles and the cellular processes responsible for their incorporation into viral proteins remains limited. This review aims to consolidate our current knowledge of viral components that have been characterized as FeS proteins and elucidate how viruses harness these versatile cofactors to their benefit. Its objective is also to propose that viruses may depend on incorporation of FeS cofactors more extensively than is currently known. This has the potential to revolutionize our understanding of viral replication, thereby carrying significant implications for the development of strategies to target infections.

BK and JC polyomaviruses and risk of urothelial bladder carcinoma: a preliminary study in the northern shores of Persian Gulf, Iran

BACKGROUND

Bladder cancer is a challenging public health concern in South of Iran because of its high prevalence and the related medical expenses. Although the exact etiology of bladder cancer remains unknown, given the cell transforming ability and oncogenic potential of the members of Polyomaviridae families, this study was conducted to evaluate the magnitude of BK polyomavirus (BKPyV) and John Cunningham polyomavirus (JCPyV) among patients with bladder cancer residents in the northern shores of the Persian Gulf, South of Iran.

METHODS

Totally 211 patients with bladder cancer were enrolled in this study. Bladder biopsy samples of these patients and patients with interstitial cystitis as well as autoptic samples of healthy bladder were tested for detection of BKPyV and JCPyV by semi-nested PCR-RFLP followed by sequencing.

RESULTS

BKPyV and JCPyV were detected in 1.7% and 6.1% of bladder cancer samples, respectively. These samples were infected with JCPyV genotypes 2, 3 and 6 and BKPyV genotypes I and IV. BKPyV and JCPyV coinfection was detected in 2 samples. Moreover, one of the healthy bladder samples was positive for BKPyV, and one of the interstitial cystitis samples was positive for JCPyV. Although the majority of infected patients were in the age group 70-79 years, male, residents in Tangestan, stage Ta-T1, and low-grade and high-grade papillary urothelial carcinoma, the prevalence of BKPyV and JCPyV among patients with bladder cancer was not statistically associated with age, gender, place of residency, and stage and grade of the tumor.

CONCLUSION

Despite identifying BKPyV and JCPyV in a number of bladder cancer biopsy specimens and the high prevalence of bladder cancer among people resident in South of Iran, it is suggested that these viruses are unlikely to be effective causative factors in bladder carcinogenesis in this region. Therefore, environmental risk factors and genetic backgrounds may have a more prominent role than human polyomaviruses in the development of bladder cancer in South of Iran.

Emerging role of human polyomaviruses 6 and 7 in human cancers

BACKGROUND

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

MAIN BODY

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

CONCLUSION

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

Merkel Cell Polyomavirus Downregulates N-myc Downstream-Regulated Gene 1, Leading to Cellular Proliferation and Migration

Merkel cell polyomavirus (MCPyV) is the first human polyomavirus etiologically associated with Merkel cell carcinoma (MCC), a rare and aggressive form of skin cancer. Similar to other polyomaviruses, MCPyV encodes early T antigen genes, viral oncogenes required for MCC tumor growth. To identify the unique oncogenic properties of MCPyV, we analyzed the gene expression profiles in human spontaneously immortalized keratinocytes (NIKs) expressing the early genes from six distinct human polyomaviruses (PyVs), including MCPyV. A comparison of the gene expression profiles revealed 28 genes specifically deregulated by MCPyV. In particular, the MCPyV early gene downregulated the expression of the tumor suppressor gene N-myc downstream-regulated gene 1 (NDRG1) in MCPyV gene-expressing NIKs and hTERT-MCPyV gene-expressing human keratinocytes (HK) compared to their expression in the controls. In MCPyV-positive MCC cells, the expression of NDRG1 was downregulated by the MCPyV early gene, as T antigen knockdown rescued the level of NDRG1. In addition, NDRG1 overexpression in hTERT-MCPyV gene-expressing HK or MCC cells resulted in a decrease in the number of cells in S phase and cell proliferation inhibition. Moreover, a decrease in wound healing capacity in hTERT-MCPyV gene-expressing HK was observed. Further analysis revealed that NDRG1 exerts its biological effect in Merkel cell lines by regulating the expression of the cyclin-dependent kinase 2 (CDK2) and cyclin D1 proteins. Overall, NDRG1 plays an important role in MCPyV-induced cellular proliferation.IMPORTANCE Merkel cell carcinoma was first described in 1972 as a neuroendocrine tumor of skin, most cases of which were reported in 2008 to be caused by a PyV named Merkel cell polyomavirus (MCPyV), the first PyV linked to human cancer. Thereafter, numerous studies have been conducted to understand the etiology of this virus-induced carcinogenesis. However, it is still a new field, and much work is needed to understand the molecular pathogenesis of MCC. In the current work, we sought to identify the host genes specifically deregulated by MCPyV, as opposed to other PyVs, in order to better understand the relevance of the genes analyzed on the biological impact and progression of the disease. These findings open newer avenues for targeted drug therapies, thereby providing hope for the management of patients suffering from this highly aggressive cancer.

Mixed epithelial and stromal tumor after pediatric kidney transplant

MEST of the kidney are a benign group of tumors with very rare incidence of malignant transformation. First described in 1998, this tumor has never been reported in a transplanted organ before. We present a unique case of de novo MEST in a donor kidney 4 years after transplant into a pediatric patient. Although removal of the lesions is curative without risking malignant transformation, in this case, surgical removal was not attempted to prevent reduction in transplant longevity. In this unique report of MEST in a transplanted kidney, we describe the patient/transplant outcomes without MEST resection.

Oncogenic Virome Benefits from the Different Vaginal Microbiome-Immune Axes

The picture of dynamic interaction between oncogenic viruses and the vaginal bacteria-immune host milieu is incomplete. We evaluated the impact of Polyomaviridae, Papillomaviridae, and Herpesviridae oncoviruses on the vaginal Community State Types (CSTs) and host immune response in reproductive-age women. In our cohort, only Polyomaviridae and Papillomaviridae were detected and were associated with changes in the resident bacteria of CST I and IV (p < 0.05). Lactobacillus crispatus increased in CST I while Prevotella timonensis and Sneathia sanguinegens increased in CST IV. Conversely, CST II and III showed an alteration of the immune response, with the decrease of Eotaxin, MCP-1, IL-7, IL-9, and IL-15 (p < 0.05), leading to reduced antiviral efficacy. An efficient viral clearance was observed only in women from CST I, dominated by Lactobacillus crispatus. Our in vivo study begins to address the knowledge gap with respect to the role of vaginal bacteria and immune response in susceptibility to oncoviral infections.

Human polyomaviruses and cancer: an overview

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

BK Polyomavirus and the Transplanted Kidney: Immunopathology and Therapeutic Approaches

BK polyomavirus is ubiquitous, with a seropositivity rate of over 75% in the adult population. Primary infection is thought to occur in the respiratory tract, but asymptomatic BK virus latency is established in the urothelium. In immunocompromised host, the virus can reactivate but rarely compromises kidney function except in renal grafts, where it causes a tubulointerstitial inflammatory response similar to acute rejection. Restoring host immunity against the virus is the cornerstone of treatment. This review covers the virus-intrinsic features, the posttransplant microenvironment as well as the host immune factors that underlie the pathophysiology of polyomavirus-associated nephropathy. Current and promising therapeutic approaches to treat or prevent this complication are discussed in relation to the complex immunopathology of this condition.

Metagenomic survey for viruses in Western Arctic caribou, Alaska, through iterative assembly of taxonomic units

Pathogen surveillance in animals does not provide a sufficient level of vigilance because it is generally confined to surveillance of pathogens with known economic impact in domestic animals and practically nonexistent in wildlife species. As most (re-)emerging viral infections originate from animal sources, it is important to obtain insight into viral pathogens present in the wildlife reservoir from a public health perspective. When monitoring living, free-ranging wildlife for viruses, sample collection can be challenging and availability of nucleic acids isolated from samples is often limited. The development of viral metagenomics platforms allows a more comprehensive inventory of viruses present in wildlife. We report a metagenomic viral survey of the Western Arctic herd of barren ground caribou (Rangifer tarandus granti) in Alaska, USA. The presence of mammalian viruses in eye and nose swabs of 39 free-ranging caribou was investigated by random amplification combined with a metagenomic analysis approach that applied exhaustive iterative assembly of sequencing results to define taxonomic units of each metagenome. Through homology search methods we identified the presence of several mammalian viruses, including different papillomaviruses, a novel parvovirus, polyomavirus, and a virus that potentially represents a member of a novel genus in the family Coronaviridae.

Polyomavirus BK-encoded microRNA suppresses autoregulation of viral replication

Polyomavirus BK (BKV) infection is an important cause of renal allograft failure. Viral microRNAs are known to play a crucial role in viral replication. This study investigated the expression of BKV-encoded microRNAs (miR-B1) in patients with polyomavirus-associated nephropathy (PVAN) and their role in viral replication. Following BKV infection in renal proximal tubular cells, the 3p and 5p miR-B1 levels were significantly increased. Cells transfected with the vector containing the miR-B1 precursor (the miR-B1 vector) showed a significant increase in expression of 3p and 5p miR-B1 and decrease in luciferase activity of a reporter containing the 3p and 5p miR-B1 binding sites, compared to cells transfected with the miR-B1-mutated vector. Transfection of the miR-B1 expression vector or the 3p and 5p miR-B1 oligonucleotides inhibited expression of TAg. TAg-enhanced promoter activity and BKV replication were inhibited by miR-B1. In contrast, inhibition of miR-B1 expression by addition of miR-B1 antagomirs or silencing of Dicer upregulated the expression of TAg and VP1 proteins in BKV-infected cells. Importantly, patients with PVAN had significantly higher levels of 3p and 5p miR-B1 compared to renal transplant patients without PVAN. In conclusion, we demonstrated that (1) miR-B1 expression was upregulated during BKV infection and (2) miR-B1 suppressed TAg-mediated autoregulation of BKV replication. Use of miR-B1 can be evaluated as a potential treatment strategy against BKV infection.

Small Circular DNAs in Human Pathology

In general, human pathogen-related small circular deoxyribonucleic acid (DNA) molecules are bacterial plasmids and a group of viral genomes. Plasmids are extra-chromosomal small circular DNAs that are capable of replicating independently of the host, and are present throughout a variety of different microorganisms, most notably bacteria. While plasmids are not essential components of the host, they can impart an assortment of survival enhancing genes such as for fertility, drug resistance, and toxins. Furthermore, plasmids are of particular interest to molecular biology especially in relation to gene-cloning. Among viruses, genomes of anelloviruses, papillomaviruses, and polyomaviruses consist of small circular DNA. The latter two virus families are known for their potential roles in a number of pathogenic processes. Human papillomaviruses (HPV) are now widely recognised to be associated with a greatly increased risk of cervical cancer, especially oncogenic strains 16 and 18. On the other hand, human cells may contain several types of small circular DNA molecules including mitochondrial DNA (mtDNA). The mitochondrial genome consists of 37 genes that encode for proteins of the oxidation phosphorylation system, transfer ribonucleic acids (tRNAs), and ribosomal RNAs (rRNAs). Though mitochondria can replicate independently of the host; nuclear DNA does encode for several mitochondrial proteins. Mutations in mtDNA contribute to some well characterised diseases; mtDNA is also implicated in several diseases and malignancies with poorly elucidated aetiologies. Furthermore, mtDNA can function as a diagnostic tool. Other extra-chromosomal circular DNAs are usually detected in cancer. This review article is intended to provide an overview of four broad categories of small circular DNAs that are present in non-eukaryotic (plasmids and relevant viral genomes) and eukaryotic (mtDNA and other extra-chromosomal DNAs) systems with reference to human diseases, particularly cancer. For this purpose, a literature search has been carried out mainly from PubMed. Improved understanding of the significance of small circular DNA molecules is expected to have far reaching implications in many fields of medicine.

Oncogenic Papillomavirus and Polyomavirus in Water Environments: Is There a Potential for Waterborne Transmission?

Waterborne exposure to human viruses through contact with sewage-contaminated water environments can result in infections associated with a wide range of illnesses. Gastrointestinal symptoms are the most commonly encountered manifestations of waterborne viral illness. Respiratory diseases, neurological diseases and paralysis can also occur. Whether viral infections resulting in health outcomes like cancer might also be transmitted by the waterborne route is unknown. Recently, viruses belonging to two oncogenic groups-Human Papillomaviruses (HPVs) and Human Polyomaviruses (HPyVs)-have been detected in urban sewages worldwide. The latter have also been identified in other water environments. HPVs are epitheliotropic viruses responsible for several diseases of skin and mucosae, from common warts to squamous intraepithelial lesions that can either heal or progress to invasive carcinoma of the cervix, vulva, vagina, penis, anus or oropharynx. Human PyVs infect different tissues and organs, causing infections that are usually subclinical in immunocompetent individuals but can be serious in immunocompromised hosts. These pathogens belong to a family of DNA tumour viruses. Merkel cell polyomavirus, a HPyV identified in recent years, has attracted much attention due to its link with a rare and aggressive form of human cancer. Merkel cell carcinoma, the incidence of which has tripled over the past two decades. JC polyomavirus and BK polyomavirus are also potentially oncogenic. The observed abundance and wide dissemination of HPVs and HPyVs in water environments strongly suggest the need to shed light on the fate of these viruses in water environments and to elucidate their potential for waterborne transmission. Such information is essential for the improvement of wastewater management programs in terms of both sewage treatment and water quality surveillance.

SV40 TAg mouse models of cancer

The discovery of a number of viruses with the ability to induce tumours in animals and transform human cells has vastly impacted cancer research. Much of what is known about tumorigenesis today regarding tumour drivers and tumour suppressors has been discovered through experiments using viruses. The SV40 virus has proven extremely successful in generating transgenic models of many human cancer types and this review provides an overview of these models and seeks to give evidence as to their relevance in this modern era of personalised medicine and technological advancements.

Human polyomavirus reactivation: disease pathogenesis and treatment approaches

JC and BK polyomaviruses were discovered over 40 years ago and have become increasingly prevalent causes of morbidity and mortality in a variety of distinct, immunocompromised patient cohorts. The recent discoveries of eight new members of the Polyomaviridae family that are capable of infecting humans suggest that there are more to be discovered and raise the possibility that they may play a more significant role in human disease than previously understood. In spite of this, there remains a dearth of specific therapeutic options for human polyomavirus infections and an incomplete understanding of the relationship between the virus and the host immune system. This review summarises the human polyomaviruses with particular emphasis on pathogenesis in those directly implicated in disease aetiology and the therapeutic options available for treatment in the immunocompromised host.